FibroGen (FGEN) 424B5 Prospectus supplement for primary offering

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-280597

Prospectus Supplement

(To prospectus dated July 10, 2024)

$30,000,000

Common Stock

We have entered into an ATM Equity Offering Sales Agreement, or Sales Agreement, with BofA Securities, Inc., or BofA, as our sales agent, dated February 24, 2025, relating to the sale from time to time of shares of our common stock, par value $0.01 per share, offered by this prospectus supplement and accompanying prospectus. In accordance with the terms of the Sales Agreement, under this prospectus supplement and accompanying prospectus we may offer and sell shares of our common stock having an aggregate offering price of up to $30.0 million from time to time through or to BofA, acting as our agent or principal.

Our common stock is listed on the Nasdaq Global Select Market under the trading symbol “FGEN.” On February 20, 2025, the last reported sale price of our common stock was $0.7724 per share.

Sales of our common stock, if any, under this prospectus supplement and accompanying prospectus, will be made in sales deemed to be an “at the market offering” as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, or the Securities Act, in ordinary brokers’ transactions, to or through a market maker, on or through The Nasdaq Global Select Market or any other market venue where the securities may be traded, in the over-the-counter market, in privately negotiated transactions, or through a combination of any such methods of sale. BofA may also sell our common stock by any other method permitted by law. BofA is not required to sell any specific amount of securities but will act as our sales agent using commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between BofA and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

Under the Sales Agreement, we may also sell common stock to BofA as principal for its own account, at a price to be agreed upon at the time of sale. If we sell common stock to BofA as principal, we will enter into a separate terms agreement with BofA, and we will describe the agreement in a separate prospectus supplement or pricing supplement.

The compensation to BofA for sales of common stock sold pursuant to the Sales Agreement will be an amount up to 3.00% of the gross proceeds of any shares of common stock sold under the Sales Agreement. In connection with the sale of the common stock on our behalf, BofA may be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of BofA may be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to BofA with respect to certain liabilities, including liabilities under the Securities Act and the Securities Exchange Act of 1934, as amended, or the Exchange Act.

We are a smaller reporting company as defined under the U.S. federal securities laws and, as such, may elect to comply with certain reduced public company reporting requirements for this and future filings. See the section titled “Prospectus Supplement Summary—Implications of Being a Smaller Reporting Company.”

Investing in our securities involves a high degree of risk. Before making an investment decision, you should review carefully and consider all of the information set forth in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein. See “Risk Factors ” beginning on page S-5 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

BofA Securities

The date of this prospectus supplement is February 24, 2025.

TABLE OF CONTENTS

Prospectus Supplement

	Page
ABOUT THIS PROSPECTUS SUPPLEMENT		S-ii
PROSPECTUS SUPPLEMENT SUMMARY		S-1
RISK FACTORS		S-5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		S-9
USE OF PROCEEDS		S-10
DILUTION		S-11
UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL INFORMATION		S-12
MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERS		S-20
PLAN OF DISTRIBUTION		S-24
LEGAL MATTERS		S-26
EXPERTS		S-26
WHERE YOU CAN FIND MORE INFORMATION		S-26
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		S-27

Prospectus

	Page
ABOUT THIS PROSPECTUS		ii
PROSPECTUS SUMMARY		1
RISK FACTORS		5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		6
USE OF PROCEEDS		7
DESCRIPTION OF CAPITAL STOCK		8
DESCRIPTION OF DEBT SECURITIES		13
DESCRIPTION OF WARRANTS		20
LEGAL OWNERSHIP OF SECURITIES		22
PLAN OF DISTRIBUTION		25
LEGAL MATTERS		27
EXPERTS		27
WHERE YOU CAN FIND ADDITIONAL INFORMATION		27
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		28

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ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying prospectus are part of a “shelf” registration statement on Form S-3 (File No. 333-280597) that we filed with the U.S. Securities and Exchange Commission, or the SEC, on June 28, 2024 and that was declared effective on July 10, 2024.

This document contains two parts. The first part is this prospectus supplement, including the documents incorporated by reference herein, which describes the specific terms of this offering and adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference herein and therein. The second part is the accompanying prospectus, including the documents incorporated by reference therein, which provides more general information about the shares of our common stock and other securities we may offer from time to time under our shelf registration statement, some of which may not apply to the securities offered by this prospectus supplement. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. Before you invest, you should carefully read and consider this prospectus supplement, the accompanying prospectus and all information incorporated by reference herein and therein and any free writing prospectus that we have authorized for use in connection with this offering before making an investment decision. You should also carefully read and consider the information described under the sections of this prospectus supplement and the accompanying prospectus titled “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.” These documents contain information you should consider when making your investment decision. This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or any document incorporated by reference into this prospectus supplement and the accompanying prospectus, on the other hand, you should rely on the information in the document having the later date, as our business, financial condition, results of operations and prospects may have changed since the earlier date.

Neither we nor BofA have authorized any other person to provide you with any information that is different than or inconsistent with the information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus or in any free writing prospectus that we have authorized for use in connection with this offering. We and BofA take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement, the accompanying prospectus and the offering of shares of our common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of shares of our common stock and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

We obtained the industry and market data in this prospectus supplement and accompanying prospectus from our own research, as well as from industry and general publications, surveys and studies conducted by third parties. These data involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions and estimates of our future performance and the future performance of the industry in which we operate is necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including those described in “Risk Factors” and elsewhere in this prospectus supplement and accompanying prospectus, and the documents incorporated by reference herein and therein. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

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Unless otherwise stated or unless the context requires otherwise, all references in this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein to “FibroGen,” the “Company,” “we,” “us” and “our” and other similar references refer to FibroGen, Inc., a corporation under the laws of the State of Delaware. Our website address is http://www.fibrogen.com. We do not incorporate the information on our website into this prospectus supplement, and you should not consider it part of this prospectus supplement.

This prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein include trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus supplement and the accompanying prospectus are the property of their respective owners.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights selected information contained elsewhere in this prospectus supplement and accompanying prospectus and the documents incorporated by reference herein and therein, and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus supplement and accompanying prospectus and any related free writing prospectus, including the risks of investing in our securities discussed under the heading “Risk Factors” contained in this prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus supplement. You should also carefully read the information incorporated by reference into this prospectus supplement and accompanying prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus supplement is a part.

FibroGen, Inc.

Overview

Through our partnership with Fortis Therapeutics, we are developing FG-3246, a first-in-class antibody-drug conjugate targeting CD46, for the treatment of metastatic castration-resistant prostate cancer and potentially other cancers. This program also includes the development of FG-3180, an associated CD46-targeted PET biomarker and imaging agent. We anticipate initiation of a Phase 2 monotherapy dose optimization study of FG-3246 for the treatment of mCRPC in the second quarter of 2025.

Prior to focusing on FG-3246 and our other clinical programs, we and our collaboration partners developed roxadustat (爱瑞卓^®, EVRENZO^TM), which is currently approved in China, Europe, Japan, and numerous other countries for the treatment of anemia in chronic kidney disease patients on dialysis and not on dialysis.

On February 20, 2025, we and our indirect subsidiary FibroGen China Anemia Holdings, Ltd. entered into a share purchase agreement with AstraZenec Treasury Limited, a subsidiary of AstraZeneca plc, or AstraZenaca, pursuant to which we agreed to sell all of the issued and outstanding equity interests of FibroGen International (Hong Kong) Ltd., or FibroGen International, to AstraZeneca for an aggregate purchase price of approximately $160 million, comprised of $85 million in cash for the enterprise value of FibroGen International, plus an additional cash amount equal to the cash held in China by FibroGen International and its subsidiaries, currently anticipated to be approximately $75 million, as of the closing. The transaction is expected to close by mid-2025, and is subject to customary closing conditions and closing deliverables, including receipt of regulatory approval from the China State Administration for Market Regulation. At the closing, we intend to repay our term loan facility with Morgan Stanley Tactical Value.

AstraZeneca is our long-time commercialization partner for roxadustat in greater China and South Korea. Upon the closing, we will assign to AstraZeneca all rights to roxadustat in China, Hong Kong, and Macao, including rights to manufacture, develop, distribute, and commercialize roxadustat.

We will retain the rights to roxadustat in the United States, Canada, Mexico, and in all markets not held by AstraZeneca or licensed to Astellas Pharma Inc. Roxadustat is not approved for commercialization in any indication in the United States, Canada, or Mexico. Astellas Pharma is commercializing roxadustat (Evrenzo^TM) in Europe and Japan to treat anemia under two development and commercialization license agreements: one for Japan, and one for Europe, the Commonwealth of Independent States, the Middle East and South Africa.

We intend to continue to evaluate a development plan for roxadustat in anemia associated with lower-risk myelodysplastic syndrome, a high-value indication with significant unmet medical need. We are planning for a meeting with the FDA in the second quarter of 2025 to determine the potential next steps for the development program for roxadustat in the United States.

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Intellectual Property

Several patents in our roxadustat patent portfolio have been challenged in Europe and China. In particular, patent challenges have been filed against our crystal form patents in Europe and China, and against our photostable formulations patent in Europe. European Patent No. 2872488, or the 488 Patent, which claimed the commercial crystalline form of roxadustat, was revoked in opposition, and the decision is not under appeal. While European Patent No. 3470397, or the 397 Patent, which is a divisional of the 488 Patent, was upheld in opposition, the opponents have appealed the decision. European Patent No. 3003284, or the 284 Patent, which claims photostable formulations of roxadustat, was upheld in opposition, but the opponents appealed the decision and the patent was revoked, with no further appeals possible. In China, three roxadustat crystal form patents were revoked in first-round proceedings and two revocations were upheld on first appeal; however, all decisions currently remain on appeal. Final resolution of ongoing proceedings in Europe and China will take time and we cannot be assured that these patents will survive these proceedings as originally granted or at all.

Risks Associated with Our Business

Our business is subject to numerous risks. You should read these risks before you invest in our common stock. In particular, our risks include, but are not limited to, the following:

• If we are unable to consummate the sale of FibroGen International to AstraZenca, the trading price of our common stock and our business may be harmed;

• There is substantial doubt about our ability to continue as a going concern and we need to raise additional funding, which may not be available on acceptable terms. If we are unable to raise additional capital when needed, we may be forced to delay, limit, reduce or terminate our product candidate development programs or other operations;

• We are not currently in compliance with the minimum bid price requirements of the Nasdaq listing rules, and if we are unable to achieve compliance, our common stock may be delisted from the Nasdaq Stock Market, which may adversely the trading volume and liquidity of our common stock;

• We are substantially dependent on the success of our lead product candidate FG-3246 (in conjunction with our PET imaging agent FG-3180).

• Drug development and obtainment of marketing authorization are very difficult endeavors, and we may ultimately be unsuccessful in one or more clinical trials and be unable to obtain regulatory approval for our various product candidates in one or more jurisdictions and in one or more indications;

• If our preclinical and clinical trial contractors do not properly perform their agreed-upon obligations, we may not be able to obtain or may be delayed in receiving regulatory approvals for our product candidates;

• We currently rely, and expect to continue to rely, on third parties to conduct many aspects of our product development, manufacturing and distribution, and these third parties may terminate these agreements or not perform satisfactorily;

• We face significant competition from other biotherapeutics and pharmaceutical companies, and our operating results will suffer if we fail to compete effectively;

• We are exposed to the risks associated with litigation, investigations, regulatory proceedings, and other legal matters, any of which could have a material adverse effect on us; and

• We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

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Implications of Being a Smaller Reporting Company

We are a “smaller reporting company,” as defined in the Exchange Act. As such, we are eligible for exemptions from various reporting requirements applicable to other public companies that are not smaller reporting companies, including, but not limited to, reduced disclosure obligations regarding financial data and executive compensation. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests.

Corporate Information

We were incorporated in 1993 in Delaware. The telephone number at our headquarters is (415) 978-1200. Our website address is www.fibrogen.com. The information contained on, or that can be accessed through, our website is not part of, and is not incorporated into, this prospectus supplement. We have included our website address in this prospectus supplement solely as an inactive textual reference.

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The Offering

Common stock offered by us Shares of common stock having an aggregate offering price of up to $30.0 million.

Common stock to be outstanding after this offering Up to 139,610,132 shares, assuming the sale of 38,839,979 shares of our common stock in this offering at an offering price of $0.7724 per share, which was the last reported sale price of our common stock on the Nasdaq Global Select Market on February 20, 2025. The actual number of shares issued will vary depending on how many shares of our common stock are sold in the offering.

Manner of offering From time to time by us through or to BofA, acting as agent on our behalf or as principal, including through “at-the-market” offerings, as applicable. See “Plan of Distribution.”

Use of proceeds We intend to use the net proceeds from this offering, if any, for working capital and general corporate purposes, including research and development expenses and capital expenditures. We may also use a portion of the net proceeds and our existing cash, cash equivalents and marketable securities to in-license, acquire, or invest in complementary businesses, technology platforms, products or assets. However, we have no current commitments or obligations to do so. See “Use of Proceeds.”

Risk factors You should read the “Risk Factors” section of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement for a discussion of factors to consider before deciding to purchase shares of our common stock.

Nasdaq Global Select Market symbol “FGEN”

The number of our shares of common stock to be outstanding after this offering is based on 100,770,153 shares of common stock outstanding as of September 30, 2024, and excludes the following, all as of September 30, 2024:

• 15,136,617 shares of common stock issuable upon the exercise of outstanding stock options with a weighted-average exercise price of $12.1194 per share;

• 3,368,722 shares of common stock issuable upon the vesting and settlement of outstanding restricted stock units;

• 12,197,475 shares of common stock available for future grant under our 2024 Equity Incentive Plan; and

• 6,665,858 shares of common stock available for issuance under our Employee Stock Purchase Plan.

In addition, unless we specifically state otherwise, all information in this prospectus supplement reflects and assumes no exercise of outstanding stock options or vesting and settlement of the restricted stock units described above.

In connection with entering into the Sales Agreement with BofA, we terminated our prior Equity Distribution Agreement, dated February 27, 2023, with Goldman Sachs & Co. LLC and BofA.

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RISK FACTORS

Investing in our common stock involves a high degree of risk. Before deciding whether to invest in our common stock, you should consider carefully the risks and uncertainties described below and discussed under the heading “Risk Factors” contained in our most recent Annual Report on Form 10-K, and in our subsequent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus supplement in their entirety, together with other information in this prospectus supplement and accompanying prospectus, the documents incorporated by reference herein and therein, and any free writing prospectus that we may authorize for use in connection with this offering. The risks described in these documents are not the only ones we face, but those that we consider to be material. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment. Please also read carefully the section below titled “Special Note Regarding Forward-Looking Statements.”

Risks Related to This Offering

Management will have broad discretion as to the use of the net proceeds from this offering, and may not use the proceeds effectively.

Because we have not designated the amount of net proceeds from this offering to be used for any particular purpose, our management will have broad discretion as to the application of any net proceeds from this offering and could use them for purposes other than those contemplated at the time of the offering. Our management may use any net proceeds for corporate purposes that may not improve our financial condition or market value. If our management applies these proceeds in a manner that does not yield a significant return, if any, on our investment of these net proceeds, it could compromise our ability to pursue our growth strategy and adversely affect the market price of our common stock.

You may experience immediate and substantial dilution as a result of this offering.

The offering price per share in this offering may exceed the net tangible book deficit per share of our common stock outstanding prior to this offering. Assuming an aggregate of 38,839,979 shares of our common stock are sold in this offering, based on an assumed sale price of $0.7724 per share, the last sale price of a share of our common stock on the Nasdaq Global Select Market on February 20, 2025, you will experience immediate dilution of $2.0123 per share, representing the difference between the price you pay and our as adjusted net tangible book deficit per share as of September 30, 2024, after giving effect to this offering, and the assumed public offering price. The exercise of outstanding stock options and vesting and settlement of outstanding restricted stock units may result in further dilution of your investment. See the section titled “Dilution” below for a more detailed illustration of the dilution you would incur if you participate in this offering.

The actual number of shares of common stock we will issue under the Sales Agreement, at any one time or in total, is uncertain.

Subject to certain limitations in the Sales Agreement and compliance with applicable law, we have the discretion to deliver an issuance notice to BofA at any time throughout the term of the Sales Agreement. The number of shares of common stock that are sold through BofA after delivering an issuance notice will fluctuate based on the market price of the shares of common stock during the sales period and limits we set with BofA. Because the price per share of each shares of common stock sold will fluctuate based on the market price of our shares of common stock during the sales period, it is not possible at this stage to predict the number of shares of common stock that will be ultimately issued.

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You may experience future dilution as a result of future equity offerings.

To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering pursuant to the Sales Agreement. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering pursuant to the Sales Agreement, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price per share paid by investors in this offering.

We do not intend to pay dividends in the foreseeable future.

We have never paid cash dividends on our common stock and currently do not plan to pay any cash dividends in the foreseeable future.

It is not possible to predict the aggregate proceeds resulting from sales made under the Sales Agreement.

Subject to certain limitations in the Sales Agreement and compliance with applicable law, we have the discretion to deliver a placement notice to BofA at any time throughout the term of the Sales Agreement. The number of shares that are sold through BofA after delivering a placement notice will fluctuate based on a number of factors, including the market price of our common stock during the sales period, any limits we may set with BofA in any applicable placement notice and the demand for our common stock. Because the price per share of each share sold pursuant to the Sales Agreement will fluctuate over time, it is not currently possible to predict the aggregate proceeds to be raised in connection with sales under the Sales Agreement.

Sales of common stock offered hereby will be in “at the market offerings,” and investors who buy shares at different times will likely pay different prices.

Investors who purchase shares in this offering at different times will likely pay different prices, and accordingly may experience different levels of dilution and different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices and number of shares sold in this offering. In addition, subject to the final determination by our board of directors or any restrictions we may place in any applicable placement notice delivered to BofA, there is no minimum or maximum sales price for shares to be sold in this offering. Investors may experience a decline in the value of the shares they purchase in this offering as a result of sales made at prices lower than the prices they paid.

Future sales or issuances of our common stock in the public markets, or the perception of such sales, could depress the trading price of our common stock.

The sale of a substantial number of shares of our common stock or other equity-related securities in the public markets, or the perception that such sales could occur, could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We may sell large quantities of our common stock at any time pursuant to this prospectus supplement or in one or more separate offerings. We cannot predict the effect that future sales of common stock or other equity-related securities would have on the market price of our common stock.

Risks Related to Our Business

If we are unable to consummate the sale of FibroGen International to AstraZenca, the trading price of our common stock and our business may be harmed.

The consummation of the sale of FibroGen International is subject to the satisfaction or waiver of various customary closing conditions, including the receipt of regulatory approval from the China State Administration

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for Market Regulation. We cannot guarantee that the closing conditions set forth in the share purchase agreement will be satisfied and if we are unable to satisfy the closing conditions, AstraZeneca will not be obligated to purchase FibroGen International. In the event that the sale is not completed, the announcement of the termination of the share purchase agreement may adversely affect the trading price of our common stock and our business. In addition, if the sale of FibroGen International to AstraZeneca is not completed, our Board of Directors, may evaluate other strategic alternatives with respect to FibroGen International, if any are available, which alternatives may not be as favorable to our stockholders as the proposed sale to AstraZeneca, and may not result in any definitive transaction or enhance stockholder value.

There is substantial doubt about our ability to continue as a going concern and we need to raise additional funding, which may not be available on acceptable terms. If we are unable to raise additional capital when needed, we may be forced to delay, limit, reduce or terminate our product candidate development programs or other operations.

If we are unable to complete the sale of FibroGen International, repatriate additional cash from our China operations, or raise additional capital in the United States, we will not have sufficient liquidity to continue operations in the United States for the twelve months from the date of this prospectus supplement and will not be able to comply with certain of our debt covenants under our senior secured term loan facilities, including the financial covenant that requires a minimum balance of $30 million of unrestricted cash and cash equivalents to be held in accounts in the United States. Upon an event of default, our senior secured term loan facilities could become immediately due and payable. We have evaluated measures to repatriate additional cash from our China operations and we believe the sale of FibroGen International represents the most efficient way to repatriate the entirety of our cash from China upon closing of the transaction. There is also the potential that we raise additional funds in the United States at any time through equity, equity-linked, or debt financing arrangements or from other sources. There can be no assurances that these plans will be successful. As a result of these factors, we have determined that there is substantial doubt about our ability to continue as a going concern within 12 months after the date of this prospectus supplement.

The consolidated financial statements incorporated into this prospectus supplement herein have been prepared in accordance with the U.S. GAAP applicable to a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business and does not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above.

Our common stock may be delisted if we are unable to regain compliance with the Nasdaq minimum bid price requirement.

On September 12, 2024, we received a letter from the Nasdaq Listing Qualifications Staff of The Nasdaq Stock Market notifying us that for 30 consecutive business days the bid price of our common stock had closed below $1.00 per share, the minimum closing bid price required by the continued listing requirements of Nasdaq listing rule 5450(a)(1).

The notification received had no immediate effect on the listing of our common stock on Nasdaq. In accordance with listing rule 5810(c)(3)(A), we have 180 calendar days, or until March 11, 2025, to regain compliance with the minimum bid price rule. To regain compliance, the closing bid price of our common stock must be at least $1.00 per share for a minimum of ten consecutive business days (or such longer period of time as the Nasdaq staff may require in some circumstances, but generally not more than 20 consecutive business days) before March 11, 2025.

If our common stock does not achieve compliance by March 11, 2025, we may be eligible for an additional 180-day period to regain compliance if we meet the continued listing requirement for market value of publicly held shares and all other initial listing standards for The Nasdaq Capital Market, with the exception of the bid

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price requirement, and provide written notice to Nasdaq of our intention to cure the deficiency during the second compliance period, including by effecting a reverse stock split, if necessary. However, if it appears to the Nasdaq staff that we will not be able to cure the deficiency, or if we do not meet the other listing standards, Nasdaq could provide notice that our common stock will become subject to delisting. In the event we receive notice that our common stock is being delisted, Nasdaq rules permit us to appeal any delisting determination by the Nasdaq staff to a Hearings Panel. We expect that our common stock would remain listed pending the Hearing Panel’s decision.

There can be no assurance that we will regain compliance with the minimum bid price rule or maintain compliance with the other listing requirements within the above timelines, or if it is necessary for us to effect a reverse stock split in order for us to regain compliance with the minimum bid price rule we may fail to do so, in which case our common stock may be delisted. If we appeal a delisting determination by Nasdaq to the Hearing Panel, there can be no assurance that such appeal would be successful.

Delisting from the Nasdaq Global Select Market or any Nasdaq market could make trading our common stock more difficult for investors, potentially leading to declines in our share price and liquidity. In addition, without a Nasdaq market listing, stockholders may have a difficult time getting a quote for the sale or purchase of our common stock, the sale or purchase of our common stock would likely be made more difficult and the trading volume and liquidity of our common stock could decline. Delisting from Nasdaq could also result in negative publicity and could also make it more difficult for us to raise additional capital. The absence of such a listing may adversely affect the value accorded by other parties. Further, if we are delisted, we would also incur additional costs under state blue sky laws in connection with any sales of our securities. These requirements could severely limit the market liquidity of our common stock and the ability of our stockholders to sell our common stock in the secondary market. If our common stock is delisted by Nasdaq, our common stock may be eligible to trade on an over-the-counter quotation system, such as the OTCQB market, where an investor may find it more difficult to sell our common stock or obtain accurate quotations as to the market value of our common stock. We cannot assure you that our common stock, if delisted from Nasdaq, will be listed on another national securities exchange or quoted on an over-the counter quotation system. If our common stock is delisted, it may come within the definition of “penny stock” as defined in the Exchange Act, and would be covered by Rule 15g-9 of the Exchange Act. That rule imposes additional sales practice requirements on broker-dealers who sell securities to persons other than established customers and accredited investors. For transactions covered by Rule 15g-9, the broker-dealer must make a special suitability determination for the purchaser and receive the purchaser’s written agreement to the transaction prior to the sale. Consequently, Rule 15g-9, if it were to become applicable, would affect the ability or willingness of broker-dealers to sell our securities, and accordingly would affect the ability of stockholders to sell their securities in the public market. These additional procedures could also limit our ability to raise additional capital in the future.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the documents we have filed with the SEC that are incorporated by reference contain “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. These statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terminology such as “believe,” “will,” “may,” “estimate,” “continue,” “anticipate,” “contemplate,” “intend,” “target,” “project,” “should,” “plan,” “expect,” “predict,” “could,” “potentially” or the negative of these terms or other similar terms or expressions that concern our expectations, strategy, plans or intentions. These statements reflect our current views with respect to future events and are based on assumptions and are subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We discuss in greater detail many of these risks under the heading “Risk Factors” in this prospectus supplement, in any free writing prospectuses we may authorize for use in connection with this offering, and in our most recent Annual Report on Form 10-K and in our most recent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus supplement in their entirety. Also, these forward-looking statements represent our estimates and assumptions only as of the date of the document containing the applicable statement. Unless required by law, we undertake no obligation to update or revise any forward-looking statements to reflect new information or future events or developments. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements. You should read this prospectus supplement and accompanying prospectus, together with the documents we have filed with the SEC that are incorporated by reference, and any free writing prospectus that we may authorize for use in connection with this offering, completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in the foregoing documents by these cautionary statements.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus supplement, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

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USE OF PROCEEDS

We may issue and sell shares of our common stock having aggregate sales proceeds of up to $30.0 million from time to time. Because there is no minimum offering amount required pursuant to the Sales Agreement with BofA, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. Actual net proceeds will depend on the number of shares we sell and the prices at which such sales occur. There can be no assurance that we will sell any shares under or fully utilize the Sales Agreement with BofA as a source of financing.

We currently intend to use the net proceeds from the sale of the common stock offered by us hereunder, if any, for working capital and general corporate purposes, including research and development expenses and capital expenditures.

We may also use a portion of the net proceeds and our existing cash, cash equivalents and marketable securities to in-license, acquire, or invest in complementary businesses, technology platforms, products or assets. However, we have no current commitments or obligations to do so.

The amounts and timing of our use of the net proceeds from this offering will depend on a number of factors, such as the timing and progress of our research and development efforts, the timing and progress of any partnering and commercialization efforts, technological advances and the competitive environment for our products. As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses for the net proceeds to us from the sale of the securities offered by us hereunder. Accordingly, our management will have broad discretion in the timing and application of these proceeds. We reserve the right to change the use of these proceeds.

Pending application of the net proceeds as described above, we intend to temporarily invest the proceeds in short-term, interest-bearing instruments.

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DILUTION

We calculate net tangible book deficit per share by dividing the net tangible book deficit, which is tangible assets less total liabilities, by the number of outstanding shares of our common stock. Dilution represents the difference between the portion of the amount per share paid by purchasers of shares in this offering and the as adjusted net tangible book deficit per share of our common stock immediately after giving effect to this offering. Our net tangible book deficit as of September 30, 2024, was $201.8 million, or $2.0026 per share.

After giving effect to the assumed sale of 38,839,979 shares of our common stock pursuant to the Sales Agreement, at a sale price of $0.7724 per share, the last sale price of our common stock on the Nasdaq Global Select Market on February 20, 2025, our net tangible book deficit as of September 30, 2024, would have been $173.1 million, or $1.2399 per share of common stock. This represents an immediate decrease in the net tangible book deficit of $(0.7627) per share to our existing stockholders and an immediate dilution in net tangible book deficit of $2.0123 per share to new investors purchasing shares in this offering. The following table illustrates this per share dilution:

Assumed offering price per share				$	0.7724
Net tangible book deficit per share as of September 30, 2024	$	2.0026
Decrease in net tangible book deficit per share attributable to new investors in offering	$	(0.7627	)
As adjusted net tangible book deficit per share as of September 30, 2024, after giving effect to this offering				$	1.2399
Dilution per share to new investors purchasing shares in this offering				$	2.0123

The above discussion and table are based on 100,770,153 shares of common stock outstanding as of September 30, 2024, and excludes the following, all as of September 30, 2024:

• 15,136,617 shares of common stock issuable upon the exercise of outstanding stock options with a weighted-average exercise price of $12.1194 per share;

• 3,368,722 shares of common stock issuable upon the vesting and settlement of outstanding restricted stock units;

• 12,197,475 shares of common stock available for future grant under our 2024 Equity Incentive Plan; and

• 6,665,858 shares of common stock available for issuance under our Employee Stock Purchase Plan.

To the extent that stock options are exercised, or restricted stock units vest and settle, or other shares are issued, investors purchasing shares in this offering could experience further dilution. In addition, we may choose to raise additional capital due to market conditions or strategic considerations, even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

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UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL INFORMATION

The following unaudited pro forma condensed consolidated financial information is intended to illustrate how the transactions contemplated by that certain share purchase agreement, dated February 20, 2025, by and among FibroGen, Inc. (“FibroGen”), FibroGen China Anemia Holdings, Ltd. and AstraZeneca Treasury Limited, pursuant to which all of the issued and outstanding equity interests of FibroGen International (Hong Kong) Ltd., (“FibroGen International”) were sold to AstraZeneca Treasury Limited (the “Agreement”), would affect the historical financial statements of FibroGen if the transactions contemplated therein had been consummated at an earlier time as indicated herein. The unaudited pro forma condensed consolidated financial information is derived, in part, from, and should be read in conjunction with, FibroGen’s historical consolidated financial statements and notes thereto, as presented in its Quarterly Report on Form 10-Q for the nine months ended September 30, 2024 and Annual Report on Form 10-K for the year ended December 31, 2023.

The aggregate purchase price included in the share purchase agreement of approximately $160 million is comprised of the base purchase price of $85.0 million and estimated cash balance of $75 million at closing. The pro forma purchase price of $104.5 million is based on the base purchase price plus cash as of September 30, 2024 adjusted primarily for net working capital.

The unaudited pro forma condensed consolidated financial information has been prepared in accordance with Article 11 of Regulation S-X. FibroGen’s accounting and financial reporting in these unaudited pro forma condensed consolidated financial information is based on its preliminary assessment of the appropriate application of accounting principles generally accepted in the U.S. (“U.S. GAAP”). The final application of U.S. GAAP to the transactions contemplated in Agreement may differ from what is presented in these unaudited pro forma condensed consolidated financial information.

The unaudited pro forma condensed consolidated balance sheet as of September 30, 2024 is prepared with the assumption that the transactions contemplated in Agreement had been consummated and FibroGen had paid off all remaining obligations under the senior secured term loan facilities with Morgan Stanley Tactical Value (“MSTV”) as of September 30, 2024.

The unaudited pro forma condensed consolidated statements of operations for the nine months ended September 30, 2024 and the year ended December 31, 2023 are prepared with the assumption that the transactions contemplated by the Agreement had been consummated as of January 1, 2022, and FibroGen had paid off all remaining obligations under the senior secured term loan facilities with MSTV when the initial term loan was drawn in 2023.

The unaudited pro forma condensed consolidated statement of operations for the year ended December 31, 2022 is prepared with the assumption that the transactions contemplated by the Agreement had been consummated as of January 1, 2022.

The transaction accounting adjustments to reflect the sale of FibroGen International in the unaudited pro forma condensed consolidated financial statements include:

• The sale of the assets and liabilities of FibroGen International required to present it on a discontinued operations basis in accordance with Accounting Standards Codification 205, Presentation of Financial Statements;

• Adjustments to release of all deferred revenue related to China single performance obligation and recognition as revenue associated with FibroGen International, which is then presented as part of discontinued operations;

• Adjustments required to present the revenues and expenses associated with FibroGen International as discontinued operations;

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• Adjustments of events that are directly attributable to the sale including, but not limited to those required to record the estimated impact of the consideration received in connection with the transaction, transaction costs, and estimated gain associated with the transaction; and

• The use of proceeds received from the transaction and existing cash and cash equivalents to repay the remainder of a term loan.

The unaudited pro forma condensed consolidated financial information does not purport to be indicative of the results of operations, the financial position or the gain on the transaction which would have actually resulted if the transactions contemplated by the Agreement had been consummated on the dates indicated, or which may result in the future.

FibroGen prepared the unaudited pro forma condensed consolidated financial information based upon assumptions deemed appropriate by its management. An explanation of certain assumptions is set forth under the notes to the unaudited pro forma condensed consolidated financial information. The pro forma adjustments may differ from those that have been or will be calculated to report the sale of FibroGen International as a discontinued operation in our historical and future filings, and do not reflect future events that may occur after the transaction.

The unaudited pro forma condensed consolidated financial statements should be read in conjunction with the notes thereto.

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FIBROGEN, INC.

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET

AS OF SEPTEMBER 30, 2024

(In thousands, except per share amounts)

	As Reported			Discontinued Operations Note 2 (a)			Note 2	Other Transaction Accounting Adjustments			Note 2	Pro Forma
Assets
Current assets:
Cash and cash equivalents	$	131,003		$	(50,956	)		$	14,850		(b)(c)	$	94,897
Accounts receivable, net		29,030			(28,839	)			—				191
Inventories		23,937			(19,365	)			—				4,572
Prepaid expenses and other current assets		60,559			(26,551	)			—				34,008
Total current assets		244,529			(125,711	)			14,850				133,668
Restricted time deposits		1,658			—								1,658
Property and equipment, net		7,603			(7,603	)			—				—
Equity method investment in unconsolidated variable interest entity		5,806			(5,806	)			—				—
Operating lease right-of-use assets		2,093			(2,093	)			—				—
Other assets		2,732			(1,044	)			—				1,688
Total assets	$	264,421		$	(142,257	)		$	14,850			$	137,014
Liabilities, redeemable non-controlling interests and deficit
Current liabilities:
Accounts payable	$	9,238		$	(224	)		$	—			$	9,014
Accrued and other current liabilities		151,141			(65,885	)			939		(d)		86,195
Deferred revenue		28,858			—				(22,135	)	(e)		6,723
Operating lease liabilities, current		1,293			(1,293	)			—				—
Total current liabilities		190,530			(67,402	)			(21,196	)			101,932
Product development obligations		18,199			—				—				18,199
Deferred revenue, net of current		126,219			—				(124,832	)	(e)		1,387
Operating lease liabilities, non-current		707			(707	)			—				—
Senior secured term loan facilities, non-current		72,779			—				(72,779	)	(c)		—
Liability related to sale of future revenues, non-current		56,850			—				—				56,850
Other long-term liabilities		837			—				—				837
Total liabilities		466,121			(68,109	)			(218,807	)			179,205
Redeemable non-controlling interests		21,480			—				—				21,480
Stockholders’ deficit:
Preferred stock, $0.01 par value; 125,000 shares authorized; no shares issued and outstanding		—			—				—				—
Common stock, $0.01 par value; 225,000 shares authorized; 98,770 shares issued and outstanding		1,008			—				—				1,008
Additional paid-in capital		1,668,434			—				—				1,668,434
Accumulated other comprehensive loss		(5,628	)		—				4,374		(f)		(1,254	)
Accumulated deficit		(1,907,481	)		(74,148	)	(g)		229,283		(g)		(1,752,346	)
Total stockholders’ deficit attributable to FibroGen		(243,667	)		(74,148	)			233,657				(84,158	)
Nonredeemable non-controlling interests		20,487			—				—				20,487
Total deficit		(223,180	)		(74,148	)			233,657				(63,671	)
Total liabilities, redeemable non-controlling interests and deficit	$	264,421		$	(142,257	)		$	14,850			$	137,014

See accompanying notes to the unaudited pro forma condensed consolidated financial information.

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FIBROGEN, INC.

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2024

(In thousands, except per share amounts)

	As Reported			Discontinued Operations Note 2 (h)			Other Transaction Accounting Adjustments		Note 2	Pro Forma
Revenue:
License revenue	$	—		$	—		$	—		$	—
Development and other revenue		1,532			—			—			1,532
Product revenue, net		126,391			(126,391	)		—			—
Drug product revenue, net		24,954			—			—			24,954
Total revenue		152,877			(126,391	)		—			26,486
Operating costs and expenses:
Cost of goods sold		36,227			(14,820	)		—			21,407
Research and development		94,206			(5,382	)		—			88,824
Selling, general and administrative		62,650			(21,666	)		—			40,984
Restructuring charge		18,554			—			—			18,554
Total operating costs and expenses		211,637			(41,868	)		—			169,769
Loss from operations		(58,760	)		(84,523	)		—			(143,283	)
Interest and other, net
Interest expense		(14,774	)		—			8,745	(i)		(6,029	)
Interest income and other income (expenses), net		5,092			(484	)		—			4,608
Total interest and other, net		(9,682	)		(484	)		8,745			(1,421	)
Loss from continuing operations before income taxes		(68,442	)		(85,007	)		8,745			(144,704	)
Benefit from income taxes		(217	)		(54	)		—			(271	)
Investment income in unconsolidated variable interest entity		2,664			(2,664	)		—			—
Net loss from continuing operations	$	(65,561	)	$	(87,617	)	$	8,745		$	(144,433	)
Net loss from continuing operations per share – basic and diluted	$	(0.66	)							$	(1.45	)
Weighted average number of common shares used to calculate net loss from continuing operations per share – basic and diluted		99,780									99,780

See accompanying notes to the unaudited pro forma condensed consolidated financial information.

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FIBROGEN, INC.

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 31, 2023

(In thousands, except per share amounts)

	As Reported			Discontinued Operations Note 2 (h)			Other Transaction Accounting Adjustments			Note 2	Pro Forma
Revenue:
License revenue	$	9,649		$	—		$	—			$	9,649
Development and other revenue		18,401			—			—				18,401
Product revenue, net		100,949			(100,949	)		—				—
Drug product revenue, net		18,753			—			—				18,753
Total revenue		147,752			(100,949	)		—				46,803
Operating costs and expenses:
Cost of goods sold		18,848			(14,886	)		—				3,962
Research and development		282,861			(16,388	)		—				266,473
Selling, general and administrative		115,252			(28,769	)		—				86,483
Restructuring charge		12,606			—			—				12,606
Total operating costs and expenses		429,567			(60,043	)		—				369,524
Loss from operations		(281,815	)		(40,906	)		—				(322,721	)
Interest and other, net
Interest expense		(15,532	)		—			7,437		(i)		(8,095	)
Loss on debt extinguishments		—			—			(10,663	)	(j)		(10,663	)
Interest income and other income (expenses), net		10,480			(2,886	)		—				7,594
Total interest and other, net		(5,052	)		(2,886	)		(3,226	)			(11,164	)
Loss from continuing operations before income taxes		(286,867	)		(43,792	)		(3,226	)			(333,885	)
Provision for (benefit from) income taxes		3			(255	)		—				(252	)
Investment income in unconsolidated variable interest entity		2,638			(2,638	)		—				—
Net loss from continuing operations	$	(284,232	)	$	(46,175	)	$	(3,226	)		$	(333,633	)
Net loss from continuing operations per share – basic and diluted	$	(2.92	)								$	(3.43	)
Weighted average number of common shares used to calculate net loss from continuing operations per share – basic and diluted		97,303										97,303

See accompanying notes to the unaudited pro forma condensed consolidated financial information.

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FIBROGEN, INC.

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 31, 2022

(In thousands, except per share amounts)

	As Reported			Discontinued Operations Note 2 (h)			Pro Forma
Revenue:
License revenue	$	22,590		$	—		$	22,590
Development and other revenue		24,189			—			24,189
Product revenue, net		82,869			(82,869	)		—
Drug product revenue, net		11,086			—			11,086
Total revenue		140,734			(82,869	)		57,865
Operating costs and expenses:
Cost of goods sold		20,280			(15,126	)		5,154
Research and development		296,791			(20,314	)		276,477
Selling, general and administrative		124,688			(32,204	)		92,484
Total operating costs and expenses		441,759			(67,644	)		374,115
Loss from operations		(301,025	)		(15,225	)		(316,250	)
Interest and other, net
Interest expense		(1,440	)		—			(1,440	)
Interest income and other income (expenses), net		7,596			(4,545	)		3,051
Total interest and other, net		6,156			(4,545	)		1,611
Loss from continuing operations before income taxes		(294,869	)		(19,770	)		(314,639	)
Provision for income taxes		358			(245	)		113
Investment income in unconsolidated variable interest entity		1,573			(1,573	)		—
Net loss from continuing operations	$	(293,654	)	$	(21,098	)	$	(314,752	)
Net loss from continuing operations per share – basic and diluted	$	(3.14	)				$	(3.36	)
Weighted average number of common shares used to calculate net loss from continuing operations per share – basic and diluted		93,582						93,582

See accompanying notes to the unaudited pro forma condensed consolidated financial information.

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FIBROGEN, INC.

NOTES TO UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL INFORMATION

1. Basis of Presentation

The unaudited pro forma condensed consolidated financial information is prepared based on FibroGen’s historical consolidated financial statements and pursuant to Article 11 of Regulation S-X, adjusted for certain transaction accounting adjustments listed in the Note 2 below. Actual adjustments, however, may differ materially from the information presented.

The “Discontinued Operations” columns in the unaudited pro forma condensed consolidated financial statements give effect to the transactions contemplated by the Agreement and has been prepared consistent with Accounting Standards Codification (“ASC”) 205-20, Presentation of Financial Statements – Discontinued Operations. Therefore, FibroGen did not allocate any general corporate overhead expenses to the discontinued operation. As such, the unaudited pro forma condensed consolidated financial information does not reflect what FibroGen’s results of operations would have been on a stand-alone basis and is not necessarily indicative of future results of operations. In addition, FibroGen’s current estimates for discontinued operations are preliminary and actual results could differ from these estimates as FibroGen finalizes the discontinued operations accounting to be reported in its Annual Report on Form 10-K for the year ended December 31, 2024.

In addition, FibroGen does not expect material income tax impact resulting from the transactions contemplated by the Agreement as it maintains a full valuation allowance on all of its deferred tax assets due to its history of losses.

2. Pro Forma Adjustments

The unaudited pro forma condensed consolidated financial information reflects the following adjustments:

(a) Derecognition of the associated assets and liabilities upon divestiture as of September 30, 2024, the net asset value of which is $74.1 million.

(b) Recognition of cash received for the sale of $104.5 million and cash paid for transaction expenses of $6.2 million at the closing of the transaction as of September 30, 2024.

(c) Recognition of cash paid to MSTV of $83.4 million to pay off the remaining obligations of the term loan and recognition of loss on debt extinguishments of $10.7 million as of September 30, 2024.

(d) Recognition of $0.9 million accrued severance payable to a certain officer at the closing of the transaction, assuming the transaction had been consummated on September 30, 2024.

(e) Release of all deferred revenues related to the single performance obligation totaling $147.0 million associated with FibroGen International.

(f) Derecognition of the currency translation adjustment balance related to FibroGen International as a result of foreign currency translation upon divestiture as of September 30, 2024.

(g) This represents the net change in accumulated deficit of the following:

• Recognition of gain on the transaction of $19.8 million, which takes into consideration transaction costs of $6.2 million (tickmark (b)), assuming the transaction had been consummated on September 30, 2024, based on the net asset held-for-sale of $74.1 million (tickmark (a));

• Recognition of loss on the debt extinguishments of $10.7 million (tickmark (c));

• Recognition of $0.9 million severance costs (tickmark (d)), which would be presented in the results of discontinued operations; and

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• Recognition of deferred revenue related to the single performance obligation totaling $147.0 million upon the sale of FibroGen International (tickmark (e)), which would be presented in the results discontinued operations.

(h) Presenting the revenues, operating costs and expenses, interest income and other income (expenses), income taxes and investment income in unconsolidated variable interest entity associated with FibroGen International as discontinued operations for the nine months ended September 30, 2024 and the years ended December 31, 2023 and 2022.

(i) Derecognition of interest expenses associated with the senior secured term loan facilities of $8.7 million and $7.4 million, respectively, for the nine months ended September 30, 2024 and the year ended December 31, 2023.

(j) Recognition of loss on debt extinguishments of $10.7 million for the year ended December 31, 2023, assuming FibroGen had paid off all obligations under the senior secured term loan facilities with MSTV when the initial term loan was drawn in 2023.

On February 20, 2025, the parties agreed to the terms for a transition services agreement. The unaudited pro forma condensed consolidated financial information does not include any compensation related to the transition services agreement as compensation related to this agreement cannot be reasonably estimated.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERS

The following summary describes the material U.S. federal income tax consequences of the acquisition, ownership and disposition of our common stock acquired in this offering by Non-U.S. Holders (as defined below). This discussion is not a complete analysis of all potential U.S. federal income tax consequences relating thereto, and does not address the potential application of the Medicare contribution tax on net investment income, the alternative minimum tax, or the special tax accounting rules under Section 451(b) of the Internal Revenue Code of 1986, as amended, or the Code, and also does not address any U.S. federal non-income tax consequences, such as estate or gift tax consequences, or any tax consequences arising under any state, local or foreign tax laws. Special rules different from those described below may apply to certain Non-U.S. Holders that are subject to special treatment under the Code, such as financial institutions, insurance companies, tax-exempt organizations, governmental organizations, broker-dealers and traders in securities, certain former U.S. citizens or long-term residents, “controlled foreign corporations,” “passive foreign investment companies,” corporations that accumulate earnings to avoid U.S. federal income tax, corporations organized outside of the United States, any state thereof or the District of Columbia that are nonetheless treated as United States income taxpayers for United States federal tax purposes, persons that hold our common stock as part of a “straddle,” “hedge,” “conversion transaction,” “synthetic security” or integrated investment or other risk reduction strategy, persons who acquire our common stock through the exercise of an option or otherwise as compensation, persons that own or have owned, actually or constructively, more than 5% of our common stock, “qualified foreign pension funds” as defined in Section 897(l)(2) of the Code and entities all of the interests of which are held by qualified foreign pension funds, partnerships and other pass-through entities or arrangements, and investors in such pass-through entities or arrangements. Such Non-U.S. Holders are urged to consult their own tax advisors to determine the U.S. federal, state, local and other tax consequences that may be relevant to them. Furthermore, the discussion below is based upon the provisions of the Code, and Treasury regulations, rulings and judicial decisions thereunder as of the date hereof, and such authorities are subject to differing interpretations and may be repealed, revoked or modified, perhaps retroactively, so as to result in U.S. federal income tax consequences different from those discussed below. We have not requested a ruling from the U.S. Internal Revenue Service, or IRS, with respect to the statements made and the conclusions reached in the following summary, and there can be no assurance that the IRS will agree with such statements and conclusions. This discussion assumes that the Non-U.S. Holder holds our common stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment).

Persons considering the purchase of our common stock pursuant to this offering should consult their own tax advisors concerning the U.S. federal income, estate and other tax consequences of acquiring, owning and disposing of our common stock in light of their particular situations as well as any consequences arising under the laws of any other taxing jurisdiction, including any state, local or foreign tax consequences.

For the purposes of this discussion, a “Non-U.S. Holder” is a beneficial owner of common stock that is neither a “U.S. Holder,” nor a partnership (or other entity treated as a partnership for U.S. federal income tax purposes regardless of its place of organization or formation). A “U.S. Holder” means a beneficial owner of our common stock that is, for U.S. federal income tax purposes, any of the following:

• an individual who is a citizen or resident of the United States;

• a corporation (or other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the U.S., any state thereof or the District of Columbia;

• an estate, the income of which is subject to U.S. federal income taxation regardless of its source; or

• a trust if it (1) is subject to the primary supervision of a court within the U.S. and one or more U.S. persons have the authority to control all substantial decisions of the trust or (2) has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

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If an entity or arrangement that is classified as a partnership for U.S. federal income tax purposes holds our common stock, the tax treatment of a person treated as a partner in such partnership for U.S. federal income tax purposes generally will depend on the status of the partner, the activities of the partner and the partnership and certain determinations made at the partner level. A person treated as a partner in a partnership or who holds our common stock through another pass-through entity should consult his, her or its own tax advisor regarding the tax consequences of the ownership and disposition of our common stock through a partnership or other pass-through entity, as applicable.

THIS DISCUSSION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT TAX ADVICE. PROSPECTIVE INVESTORS SHOULD CONSULT THEIR TAX ADVISORS REGARDING THE PARTICULAR U.S. FEDERAL INCOME TAX CONSEQUENCES TO THEM OF ACQUIRING, OWNING AND DISPOSING OF OUR COMMON STOCK, AS WELL AS ANY TAX CONSEQUENCES ARISING UNDER ANY STATE, LOCAL OR FOREIGN TAX LAWS AND ANY OTHER U.S. FEDERAL TAX LAWS OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Distributions

Distributions, if any, made on our common stock to a Non-U.S. Holder to the extent treated as made out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles) generally will constitute dividends for U.S. federal income tax purposes and will be subject to withholding tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty, subject to the discussions below regarding effectively connected income, backup withholding and foreign accounts. To obtain a reduced rate of withholding under a treaty, a Non-U.S. Holder generally will be required to provide us or our withholding agent with a properly executed IRS Form W-8BEN (in the case of individuals) or IRS Form W-8BEN-E (in the case of entities), or other appropriate form, including a U.S. taxpayer identification number, or in certain circumstances, a foreign tax identifying number, and certifying the Non-U.S. Holder’s entitlement to benefits under that treaty. This certification must be provided to us or our withholding agent prior to the payment of dividends and must be updated periodically. In the case of a Non-U.S. Holder that is an entity, Treasury Regulations and the relevant tax treaty provide rules to determine whether, for purposes of determining the applicability of a tax treaty, dividends will be treated as paid to the entity or to those holding an interest in that entity. If a Non-U.S. Holder holds stock through a financial institution or other agent acting on the holder’s behalf, the holder will be required to provide appropriate documentation to such agent. The holder’s agent will then be required to provide certification to us or our withholding agent, either directly or through other intermediaries. If the Non-U.S. Holder is eligible for a reduced rate of U.S. federal withholding tax under an income tax treaty and the Non-U.S. Holder does not timely file the required certification, the Non-U.S. Holder may be able to obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim for a refund with the IRS.

We generally are not required to withhold U.S. federal tax on dividends paid to a Non-U.S. Holder that are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, are attributable to a permanent establishment or fixed base that such holder maintains in the United States) if a properly executed IRS Form W-8ECI, stating that the dividends are so connected, is furnished to us (or, if stock is held through a financial institution or other agent, to such agent) prior to the payment of such dividends. In general, such effectively connected dividends will be subject to U.S. federal income tax, on a net income basis at the regular rates applicable to U.S. residents. A corporate Non-U.S. Holder receiving effectively connected dividends may also be subject to an additional “branch profits tax,” which is imposed, under certain circumstances, at a rate of 30% (or such lower rate as may be specified by an applicable treaty) on the corporate Non-U.S. Holder’s effectively connected earnings and profits, subject to certain adjustments. Non-U.S. Holders should consult their tax advisors regarding any applicable income tax treaties that may provide for different rules.

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To the extent distributions on our common stock, if any, exceed our current and accumulated earnings and profits, they will first reduce the Non-U.S. Holder’s adjusted basis in our common stock, but not below zero, and then will be treated as gain to the extent of any excess, and taxed in the same manner as gain realized from a sale or other disposition of common stock as described in the next section.

Gain on Disposition of Our Common Stock

Subject to the discussions below regarding backup withholding and foreign accounts, a Non-U.S. Holder generally will not be subject to U.S. federal income tax with respect to gain realized on a sale or other disposition of our common stock unless: (a) the gain is effectively connected with the conduct of a trade or business of such holder in the United States (and, if required by an applicable income tax treaty, is attributable to a permanent establishment or fixed base that such holder maintains in the United States), (b) the Non-U.S. Holder is a nonresident alien individual and is present in the United States for 183 or more days in the taxable year of the disposition and certain other conditions are met or (c) we are or have been a “United States real property holding corporation”, or USRPHC, within the meaning of Code Section 897(c)(2) at any time within the shorter of the five-year period preceding such disposition or such holder’s holding period. In general, we would be a USRPHC if interests in U.S. real property interests comprise (by fair market value) at least half of the value our business assets and worldwide real property interests. We believe that we have not been and we are not, and do not anticipate becoming, a USRPHC, although there can be no assurance that we will not in the future become a USRPHC. Even if we are treated as a USRPHC, gain realized by a Non-U.S. Holder on a disposition of our common stock will not be subject to U.S. federal income tax so long as (1) the Non-U.S. Holder owned, directly, indirectly and constructively, no more than five percent of our common stock at all times within the shorter of (i) the five-year period preceding the disposition or (ii) the holder’s holding period and (2) our common stock is regularly traded on an established securities market. There can be no assurance that our common stock will continue to qualify as regularly traded on an established securities market. If any gain on your disposition is taxable because we are a USRPHC and a Non-U.S. Holder’s ownership of our common stock exceeds five percent, such holder will be taxed on such disposition generally in the manner applicable to U.S. persons, and in addition, a purchaser of such holder’s common stock may be required to withhold tax with respect to that obligation.

A Non-U.S. Holder described in (a) above will be required to pay tax on the net gain derived from the sale at regular U.S. federal income tax rates in the same manner as if such holder were a resident of the United States, and corporate Non-U.S. Holders described in (a) above may be subject to the additional branch profits tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty. Gain described in (b) above will be subject to U.S. federal income tax at a flat 30% rate or such lower rate as may be specified by an applicable income tax treaty, which gain may be offset by certain U.S.-source capital losses (even though the Non-U.S. Holder is not considered a resident of the U.S.), provided that the Non-U.S. Holder has timely filed U.S. federal income tax returns with respect to such losses.

Non-U.S. Holders should consult their tax advisors regarding any applicable income tax treaties that may provide for different rules.

Information Reporting Requirements and Backup Withholding

Generally, we must report information to the IRS with respect to any distributions we pay on our common stock (even if the payments are exempt from withholding), including the amount of any such distributions, the name and address of the recipient, and the amount, if any, of tax withheld. A similar report is sent to the holder to whom any such distributions are paid. Pursuant to tax treaties or certain other agreements, the IRS may make its reports available to tax authorities in the recipient’s country of residence.

Backup withholding, currently at a 24% rate, generally will not apply to payments to a Non-U.S. Holder of dividends on or the gross proceeds of a disposition of our common stock provided the Non-U.S. Holder furnishes the required certification for its non-U.S. status, such as by providing a valid IRS Form W-8BEN, IRS

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Form W-8BEN-E or IRS Form W-8ECI, or otherwise establishes an exemption, and if the payor does not have actual knowledge, or reason to know, that the holder is a U.S. person who is not an exempt recipient.

Backup withholding is not an additional tax. If any amount is withheld under the backup withholding rules, the Non-U.S. Holder should consult with a U.S. tax advisor regarding the possibility of and procedure for obtaining a refund or a credit against the Non-U.S. Holder’s U.S. federal income tax liability, if any.

Foreign Accounts

Sections 1471 through 1474 of the Code (commonly referred to as FATCA) impose a U.S. federal withholding tax of 30% on certain payments to a “foreign financial institution” (as specifically defined under these rules) unless such institution enters into an agreement with the U.S. government to withhold on certain payments and to collect and provide to the U.S. tax authorities substantial information regarding U.S. account holders of such institution (which includes certain equity and debt holders of such institution, as well as certain account holders that are foreign entities with U.S. owners). FATCA also generally imposes a U.S. federal withholding tax of 30% on certain payments to a “non-financial foreign entity” (as specifically defined under these rules) unless such entity provides the withholding agent with either a certification that it does not have any substantial direct or indirect U.S. owners or provides information regarding substantial direct and indirect U.S. owners of the entity. An intergovernmental agreement between the United States and an applicable foreign country may modify those requirements. The withholding tax described above will not apply if the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from the rules. Under certain circumstances, a Non-U.S. Holder might be eligible for refunds or credits of such taxes. FATCA currently applies to dividends paid on our common stock and would have applied also to payments of gross proceeds from the sale or other disposition of our common stock. However, the U.S. Treasury Department has released proposed regulations under FATCA providing for the elimination of the U.S. federal withholding tax of 30% applicable to gross proceeds of a sale or other disposition of property of a type that can produce U.S. source dividends or interest. Under these proposed Treasury Regulations (which may be relied upon by taxpayers prior to finalization), FATCA will not apply to gross proceeds from sales or other dispositions of our common stock.

Prospective investors are encouraged to consult with their own tax advisors regarding the possible implications of FATCA on their investment in our common stock.

EACH PROSPECTIVE INVESTOR SHOULD CONSULT ITS OWN TAX ADVISOR REGARDING THE TAX CONSEQUENCES OF PURCHASING, HOLDING AND DISPOSING OF OUR COMMON STOCK, INCLUDING THE CONSEQUENCES OF ANY CHANGE IN APPLICABLE LAW AS WELL AS TAX CONSEQUENCES ARISING UNDER ANY STATE, LOCAL, NON-U.S. OR U.S. FEDERAL NON-INCOME TAX LAWS.

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PLAN OF DISTRIBUTION

General

We have entered into the Sales Agreement with BofA, under which we may offer and sell from time to time shares of our common stock having an aggregate offering price of up to $30.0 million through BofA, acting as our agent, or directly to BofA, acting as principal for its own account.

Sales of shares of our common stock, if any, under this prospectus supplement and the accompanying prospectus will be made by any method permitted by law and deemed to be an “at the market offering” as defined in Rule 415 promulgated under the Securities Act, including by ordinary brokers’ transactions through the facilities of The Nasdaq Global Select Market or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices, in block transactions or as otherwise permitted by law.

BofA is not required to sell any specific number or dollar amount of shares of common stock, but BofA will use its commercially reasonable efforts, as our agent and consistent with its normal trading and sales practices, to sell, subject to the terms of the Sales Agreement, shares of common stock, as agreed upon between us and BofA from time to time.

In no event will the aggregate sales price of shares of our common stock sold by us to or through BofA, acting as our agent or as principal for its own account pursuant to the Sales Agreement, exceed $30.0 million.

In connection with the sale of shares of our common stock on our behalf, BofA may be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation paid to BofA may be deemed to be underwriting commissions or discounts. We have agreed that we will indemnify BofA against certain liabilities, including liabilities under the Securities Act, or contribute to payments that BofA may be required to make in respect of those liabilities.

We estimate that the expenses payable by us in connection with the offering and sale of shares of our common stock pursuant to the Sales Agreement, other than discounts and commissions but including expenses paid prior to the date of this prospectus supplement, will be approximately $400,000. The remaining sales proceeds from the sale of any shares of our common stock, after deducting any transaction fees, transfer taxes or similar fees, taxes or charges imposed by any governmental or self-regulatory organization in connection with such sales, shall constitute the net proceeds from the sale of our common stock offered by this prospectus supplement and the accompanying prospectus.

The offering of shares of our common stock pursuant to the Sales Agreement will terminate upon the earlier of (1) the sale of shares of our common stock having an aggregate sales price of $30.0 million pursuant to the Sales Agreement or (2) the termination of the Sales Agreement in accordance with its terms. We and BofA may each terminate the Sales Agreement at any time by providing written notice.

Upon its acceptance of instructions from us, BofA has agreed to use its reasonable efforts to sell shares of our common stock on the terms and subject to the conditions set forth in the Sales Agreement. We will instruct BofA as to the amount of common stock to be sold by it as our agent. We may instruct BofA not to sell our common stock if sales cannot be effected at or above a price designated by us. We or BofA may at any time immediately suspend the offering of shares of our common stock through BofA upon notice to the other party.

BofA will provide written confirmation following the close of trading on The Nasdaq Global Select Market on each trading day on which shares of our common stock are sold through BofA under the Sales Agreement. Each confirmation will include the number of shares of our common stock sold on that day, the aggregate gross proceeds of such sales, the net proceeds of such sales and the compensation payable by us to BofA in connection with such sales of our common stock.

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We will pay BofA an aggregate fee up to 3.0% of the gross proceeds of any shares of common stock sold pursuant to the Sales Agreement, or as otherwise agreed between us and BofA with respect to any shares of common stock sold pursuant to the Sales Agreement. We have also agreed to reimburse BofA for certain its out-of-pocket expenses, including the reasonable fees and disbursements of counsel for BofA in an amount not to exceed $150,000 in the aggregate, payable upon execution of the Sales Agreement (plus certain ongoing fees and disbursements of counsel for BofA not to exceed $15,000 in connection with each triggering event date, as such term is defined in the Sales Agreement).

Under the terms of the Sales Agreement, we may also sell shares of our common stock in negotiated transactions or as otherwise agreed with BofA, including sales to BofA, as principal for its own account, at a price to be agreed upon at the time of sale. If we sell shares of our common stock in a manner which is not an “at the market offering”, including sales to BofA, as principal for its own account, we will enter into a separate terms agreement with BofA, and we will describe the terms of the offering of such shares in a separate prospectus supplement or free writing prospectus if required. BofA does not have any obligation to purchase shares of common stock from us as principal and may elect whether or not to do so in its sole and absolute discretion.

Certain Relationships

BofA and its affiliates are a full service financial institution engaged in various activities, which may include sales and trading, commercial and investment banking, advisory, investment management, investment research, principal investment, hedging, market making, brokerage and other financial and non-financial activities and services. BofA and certain of its affiliates have provided, and may in the future provide, a variety of these services to us and to persons and entities with relationships with us, for which they received or will receive customary fees and expenses.

In the ordinary course of its various business activities, BofA and its affiliates, officers, directors and employees may purchase, sell or hold a broad array of investments and actively trade securities, derivatives, loans, commodities, currencies, credit default swaps and other financial instruments for their own accounts and for the accounts of their customers, and such investment and trading activities may involve or relate to our assets, securities and/or instruments (directly, as collateral securing other obligations or otherwise) and/or persons and entities with relationships with us. BofA and its affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such assets, securities or instruments and may at any time hold, or recommend to clients that they should acquire, long and/or short positions in such assets, securities and instruments.

Selling Restrictions

Other than in the United States, no action has been taken by us or BofA that would permit a public offering of the shares of common stock offered by this prospectus supplement and the accompanying prospectus in any jurisdiction where action for that purpose is required. The shares offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such shares be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement. This prospectus supplement does not constitute an offer to sell or a solicitation of an offer to buy any shares of common stock offered by this prospectus supplement in any jurisdiction in which such an offer or a solicitation is unlawful.

You should be aware that the laws and practices of certain countries require investors to pay stamp taxes and other charges in connection with purchases of securities.

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LEGAL MATTERS

Cooley LLP has passed upon the validity of the shares of our common stock offered hereby. BofA is being represented by Latham & Watkins, LLP in connection with the offering.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Annual Report on Internal Control over Financial Reporting) incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2023 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus supplement is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth in the registration statement. Whenever a reference is made in this prospectus supplement to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus supplement for a copy of such contract, agreement or other document. Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus supplement. Information in this prospectus supplement supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus supplement, while information that we file later with the SEC will automatically update and supersede the information in this prospectus supplement. We incorporate by reference into this prospectus supplement and the registration statement of which this prospectus supplement is a part the information or documents listed below that we have filed with the SEC (Commission File No. 001-36740):

• Our Annual Report on Form 10-K for the year ended December 31, 2023, filed with the SEC on February 26, 2024;

• The information incorporated by reference in our Annual Report on Form 10-K for the year ended December  31, 2023 from our proxy statement on Schedule 14A, filed with the SEC on April 24, 2024;

• Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2024, filed with the SEC on May 6, 2024;

• Our Quarterly Report on Form 10-Q for the quarter ended June 30, 2024, filed with the SEC on August 6, 2024;

• Our Quarterly Report on Form 10-Q for the quarter ended September 30, 2024, filed with the SEC on November 12, 2024;

• Our Current Reports on Form 8-K filed with the SEC on June 7, 2024, June  26, 2024, August 7,  2024, September  6, 2024, September  13, 2024, September  16, 2024, October  3, 2024, December  16, 2024, and February 20, 2025; and

• The description of our common stock set forth in our registration statement on Form 8-A, filed with the SEC on November  12, 2014, including any additional amendment or report filed for the purpose of updating such description, including Exhibit 4.4 to our Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020.

We also incorporate by reference any future filings (other than current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, until we file a post-effective amendment that indicates the termination of the offering of the securities made by this prospectus supplement, which will become a part of this prospectus supplement from the date that such documents are filed with the SEC. Information in such future filings updates and supplements the information provided in this prospectus supplement. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later-filed document modify or replace such earlier statements. We will furnish without charge to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request, a copy of any or all of the documents incorporated by reference into this prospectus supplement but not delivered with the prospectus supplement, including exhibits that are specifically incorporated by reference into such documents. You should direct any requests for documents to:

FibroGen, Inc.

Attn: Investor Relations

350 Bay Street

Suite 100 #6009

San Francisco, CA 94133

Telephone number: (415) 978-1200

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Prospectus

Up to $300,000,000

Common Stock

Preferred Stock

Debt Securities

Warrants

From time to time, FibroGen, Inc. may offer and sell up to an aggregate amount of $300,000,000 of any combination of the securities described in this prospectus, either individually or in combination. We may also offer common stock upon conversion of preferred stock, common stock or preferred stock upon conversion of debt securities, or common stock, preferred stock or debt securities upon the exercise of warrants.

We will provide the specific terms of these offerings and securities in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectus may also add, update or change information contained in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement and any related free writing prospectus, as well as any documents incorporated by reference, before buying any of the securities being offered.

Our common stock is listed on the Nasdaq Global Select Market under the trading symbol “FGEN.” On June 27, 2024, the last reported sale price of our common stock was $1.03 per share. The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on the Nasdaq Global Select Market or other securities exchange of the securities covered by the applicable prospectus supplement.

Investing in our securities involves a high degree of risk. Before making an investment decision, you should review carefully the risks described under the heading “Risk Factors” on page 5 of this prospectus and in our most recent Annual Report on Form 10-K and any subsequent Quarterly Report on Form 10-Q incorporated by reference into this prospectus, any similar section contained in the applicable prospectus supplement and in any free writing prospectus we have authorized for use in connection with a specific offering, and under similar headings in the documents that are incorporated by reference into this prospectus.

This prospectus may not be used to consummate a sale of securities unless accompanied by a prospectus supplement.

The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers, on a continuous or delayed basis. For additional information on the methods of sale, you should refer to the section titled “Plan of Distribution” in this prospectus. The supplements to this prospectus will provide the specific terms of the plan of distribution. If any agents or underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such agents or underwriters and any applicable fees, commissions, discounts and options to purchase additional shares will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is July 10, 2024.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		ii
PROSPECTUS SUMMARY		1
RISK FACTORS		5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		6
USE OF PROCEEDS		7
DESCRIPTION OF CAPITAL STOCK		8
DESCRIPTION OF DEBT SECURITIES		13
DESCRIPTION OF WARRANTS		20
LEGAL OWNERSHIP OF SECURITIES		22
PLAN OF DISTRIBUTION		25
LEGAL MATTERS		27
EXPERTS		27
WHERE YOU CAN FIND ADDITIONAL INFORMATION		27
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		28

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or the SEC. Under this shelf registration statement, we may offer and sell from time to time in one or more offerings the common stock, preferred stock, debt securities, warrants or any combination of these securities described in this prospectus up to a total dollar amount of $300,000,000. We may also offer common stock or preferred stock upon conversion of debt securities, common stock upon conversion of preferred stock, or common stock, preferred stock or debt securities upon the exercise of warrants.

This prospectus provides you with a general description of the securities we may offer. Each time we offer securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change any of the information contained in this prospectus or in the documents that we have incorporated by reference into this prospectus. We urge you to read carefully this prospectus, any applicable prospectus supplement and any free writing prospectus we have authorized for use in connection with a specific offering, together with the information incorporated herein by reference as described under the section titled “Incorporation of Certain Information by Reference,” before buying any of the securities being offered.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement.

You should rely only on the information contained in, or incorporated by reference into, this prospectus, any related prospectus supplement and in any free writing prospectus that we may authorize for use in connection with an offering. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are not making an offer to sell or soliciting an offer to buy our securities in any jurisdiction in which an offer or solicitation is not authorized or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation. You should assume that the information appearing in this prospectus, any related prospectus supplement and the documents incorporated by reference into this prospectus, any related prospectus supplement and in any free writing prospectus that we may authorize for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus, any related prospectus supplement, the documents incorporated by reference into this prospectus, and any free writing prospectus that we may authorize for use in connection with this offering, in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus titled “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

We are offering to sell, and seeking offers to buy, our securities only in jurisdictions where offers and sales are permitted. The distribution of this prospectus and any related prospectus supplement and the offering of our securities in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus and any related prospectus supplement must inform themselves about, and observe any restrictions relating to, the offering of our securities and the distribution of this prospectus and any related prospectus supplement outside the United States. This prospectus and any related prospectus supplement does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus and any related prospectus supplement by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

We obtained the industry and market data in this prospectus from our own research as well as from industry and general publications, surveys and studies conducted by third parties. These data involve a number of

ii

assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions and estimates of our future performance and the future performance of the industry in which we operate is necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including those described in “Risk Factors” and elsewhere in this prospectus, any related prospectus supplement and documents incorporated by reference into this prospectus and any related prospectus supplement. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below under the section titled “Where You Can Find Additional Information.”

“FibroGen,” the FibroGen logo and other trademarks or service marks of FibroGen, Inc. appearing or incorporated by reference in this prospectus and any related prospectus supplement are the property of FibroGen, Inc. This prospectus and any related prospectus supplement, including the information incorporated by reference into this prospectus and any related prospectus supplement, include trademarks, service marks and trade names owned by others. All trademarks, service marks and trade names included or incorporated by reference in this prospectus, any related prospectus supplement or any related free writing prospectus are the property of their respective owners.

iii

PROSPECTUS SUMMARY

This summary highlights selected information appearing elsewhere in this prospectus or incorporated by reference in this prospectus, and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus, the applicable prospectus supplement and any related free writing prospectus, including the risks of investing in our securities discussed under the section titled “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus. You should also carefully read the information incorporated by reference into this prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus is a part.

References in this prospectus to “FibroGen,” “we,” “us” and “our” refer to FibroGen, Inc., a Delaware corporation, and its subsidiaries. Our website address is www.fibrogen.com. We do not incorporate the information on our website into this prospectus, and you should not consider it part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

FibroGen, Inc.

Overview

FibroGen is developing and commercializing a diversified pipeline of novel therapeutics that work at the frontier of cancer biology and anemia.

Pamrevlumab, a human monoclonal antibody targeting connective tissue growth factor, or CTGF, is in Phase 3 clinical development for the treatment of locally advanced unresectable pancreatic cancer. Pamrevlumab is also in Phase 2/3 development for the treatment of metastatic pancreatic cancer. To date, we have retained exclusive worldwide rights for pamrevlumab.

Roxadustat is an oral small molecule inhibitor of HIF prolyl hydroxylase activity. Roxadustat (爱瑞卓^®, EVRENZO^TM) is approved in China, Europe, Japan, and numerous other countries for the treatment of anemia in chronic kidney disease for patients who are on dialysis and not on dialysis. Roxadustat is in clinical development for chemotherapy-induced anemia in China.

We are also developing earlier stage clinical and preclinical product candidates, FG-3246, FG-3165 and FG-3175, to address unmet patient needs in oncology.

Risks Associated with Our Business

Our business is subject to numerous risks. You should read these risks set forth under the section titled “Risk Factors” in the applicable prospectus supplement and contained in our most recent Annual Report on Form 10-K and in our most recent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, before you invest in our securities.

Corporate Information

We were incorporated in 1993 in Delaware. Our headquarters are located at 409 Illinois Street, San Francisco, California 94158 and our telephone number is (415) 978-1200. Our website address is www.fibrogen.com. The information contained on, or that can be accessed through, our website is not part of, and is not incorporated into, this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

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The Securities We May Offer

We may offer shares of our common stock and preferred stock, various series of debt securities or warrants to purchase any of such securities, either individually or in combination upt to a totals dollar amount of $300,000,000, from time to time under this prospectus, together with the applicable prospectus supplement and any related free writing prospectus, at prices and on terms to be determined by market conditions at the time of any offering. We may also offer common stock, preferred stock or debt securities upon the exercise of warrants. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

• designation or classification;

• aggregate principal amount or aggregate offering price;

• maturity date, if applicable;

• original issue discount, if any;

• rates and times of payment of interest or dividends, if any;

• redemption, conversion, exercise, exchange or sinking fund terms, if any;

• conversion or exchange prices or rates, if any, and, if applicable, any provisions for changes to or adjustments in the conversion or exchange prices or rates and in the securities or other property receivable upon conversion or exchange;

• ranking;

• restrictive covenants, if any;

• voting or other rights, if any; and

• material or special U.S. federal income tax considerations, if any.

The applicable prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change any of the information contained in this prospectus or in the documents we have incorporated by reference. However, no prospectus supplement or free writing prospectus will offer a security that is not registered and described in this prospectus at the time of the effectiveness of the registration statement of which this prospectus is a part.

THIS PROSPECTUS MAY NOT BE USED TO CONSUMMATE A SALE OF SECURITIES UNLESS IT IS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

We may sell the securities directly to investors or to or through agents, underwriters or dealers. We and our agents or underwriters, reserve the right to accept or reject all or part of any proposed purchase of securities. If we do offer securities to or through agents or underwriters, we will include in the applicable prospectus supplement:

• the names of those agents or underwriters;

• applicable fees, discounts and commissions to be paid to them;

• details regarding over-allotment options, if any; and

• the net proceeds to us.

Common Stock. We may issue shares of our common stock from time to time. The holders of our common stock are entitled to one vote for each share held of record on all matters submitted to a vote of stockholders.

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Subject to preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends as may be declared by our board of directors out of legally available funds. Upon our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preferences of any outstanding shares of preferred stock. Holders of common stock have no preemptive rights and no right to convert their common stock into any other securities. There are no redemption or sinking fund provisions applicable to our common stock. In this prospectus, we have summarized certain general features of the common stock under the section titled “Description of Capital Stock — Common Stock.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you) related to any common stock being offered.

Preferred Stock. We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors will determine the designations, voting powers, preferences and rights of the preferred stock, as well as the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, preemptive rights, terms of redemption or repurchase, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our common stock or exchangeable for other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we sell any series of preferred stock under this prospectus, we will fix the designations, voting powers, preferences and rights of the preferred stock of each series we issue under this prospectus, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that contains the terms of the series of preferred stock we are offering. In this prospectus, we have summarized certain general features of the preferred stock under the section titled “Description of Capital Stock — Preferred Stock.” We urge you, however, to read the applicable prospectus supplement and any related free writing prospectus that we may authorize to be provided to you, related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities. We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our common stock or other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

Any debt securities issued under this prospectus will be issued under one or more documents called indentures, which are contracts between us and a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities under the section titled “Description of Debt Securities.” We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of debt securities being offered, as well as the complete indentures and any supplemental indentures that contain the terms of the debt securities. We have filed the form of indenture as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

Warrants. We may issue warrants for the purchase of common stock, preferred stock or debt securities in one or more series. We may issue warrants independently or in combination with common stock, preferred stock

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or debt securities offered by any prospectus supplement. In this prospectus, we have summarized certain general features of the warrants under the section titled “Description of Warrants.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you) related to the particular series of warrants being offered, as well as any warrant agreements and warrant certificates that contain the terms of the warrants. We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that contain the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants.

Any warrants issued under this prospectus may be evidenced by warrant certificates. Warrants also may be issued under an applicable warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if applicable, in the prospectus supplement relating to the particular series of warrants being offered.

Use of Proceeds

Except as described in any applicable prospectus supplement or in any free writing prospectus we have authorized for use in connection with a specific offering, we currently intend to use the net proceeds from the sale of the securities offered by us hereunder, if any, for working capital, capital expenditures and other general corporate purposes. See “Use of Proceeds” in this prospectus.

Nasdaq Global Select Market Listing

Our common stock is listed on the Nasdaq Global Select Market under the symbol “FGEN.” The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on the Nasdaq Global Select Market or other securities exchange of the securities covered by the applicable prospectus supplement.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks and uncertainties described under the section titled “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and discussed under the section titled “Risk Factors” contained in our most recent Annual Report on Form 10-K and in our most recent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, together with other information in this prospectus, the documents incorporated by reference and any free writing prospectus that we may authorize for use in connection with this offering. The risks described in these documents are not the only ones we face, but those that we consider to be material. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occur, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment. Please also read carefully the section below titled “Special Note Regarding Forward-Looking Statements” and the section titled “Forward-Looking Statements” included in our most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents we have filed with the SEC that are incorporated by reference contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “could,” “would,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “projects,” “predicts,” “potential” and similar expressions intended to identify forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and are subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We discuss in greater detail many of these risks under the heading “Risk Factors” contained in the applicable prospectus supplement, in any free writing prospectus we may authorize for use in connection with a specific offering, and in our most recent Annual Report on Form 10-K and in our most recent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety. Also, these forward-looking statements represent our estimates and assumptions only as of the date of the document containing the applicable statement. Unless required by law, we undertake no obligation to update or revise any forward-looking statements to reflect new information or future events or developments. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements. You should read this prospectus, any applicable prospectus supplement, together with the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we may authorize for use in connection with this offering, completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in the foregoing documents by these cautionary statements.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

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USE OF PROCEEDS

Except as described in any applicable prospectus supplement or in any free writing prospectus we have authorized for use in connection with a specific offering, we currently intend to use the net proceeds from the sale of the securities offered by us hereunder, if any, for working capital and general corporate purposes, including research and development expenses and capital expenditures, or for any other purpose we describe in the applicable prospectus supplement.

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DESCRIPTION OF CAPITAL STOCK

Our authorized capital stock consists of 225,000,000 shares of common stock, $0.01 par value per share, and 125,000,000 shares of preferred stock, $0.01 par value per share. A description of material terms and provisions of our certificate of incorporation and bylaws affecting the rights of holders of our capital stock is set forth below. The description is intended as a summary, and is qualified in its entirety by reference to our amended and restated certificate of incorporation and amended and restated bylaws.

Common Stock

Voting Rights

Each holder of our common stock is entitled to one vote for each share of common stock held on all matters submitted to a vote of stockholders, except as otherwise expressly provided in our amended and restated certificate of incorporation or required by applicable law. We have not provided for cumulative voting for the election of directors in our amended and restated certificate of incorporation.

Economic Rights

Dividends and Distributions. Subject to the prior rights of holders of all classes and series of stock at the time outstanding having prior rights as to dividends, the holders of common stock will be entitled to receive, when, as and if declared by our board of directors, out of any assets legally available therefor, such dividends as may be declared from time to time by our board of directors.

Liquidation Rights. In the event of our liquidation, dissolution or winding-up, upon the completion of the distributions required with respect to any series of preferred stock that may then be outstanding, the remaining assets legally available for distribution to stockholders shall be distributed ratably among the holders of common stock and any participating preferred stock outstanding at that time.

Holders of common stock have no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to the common stock.

Preferred Stock

Our amended and restated certificate of incorporation provides that our board of directors may, without further action by our stockholders, fix the rights, preferences, privileges and restrictions of up to an aggregate of 125,000,000 shares of preferred stock in one or more series and authorize their issuance. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of such series, any or all of which may be greater than the rights of our common stock. The issuance of our preferred stock could adversely affect the voting power of holders of our common stock and the likelihood that such holders will receive dividend payments and payments upon liquidation, which could decrease the market price of our common stock. In addition, the issuance of preferred stock could have the effect of delaying, deferring or preventing a change of control or other corporate action. No shares of preferred stock are outstanding, and we have no present plan to issue any shares of preferred stock.

We will fix the designations, voting powers, preferences and rights of the preferred stock of each series we issue under this prospectus, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that contains the terms of the series of preferred stock we are offering. We will describe in the

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applicable prospectus supplement the terms of the series of preferred stock being offered, including, to the extent applicable:

• the title and stated value;

• the number of shares we are offering;

• the liquidation preference per share;

• the purchase price;

• the dividend rate, period and payment date and method of calculation for dividends;

• whether dividends will be cumulative or non-cumulative and, if cumulative, the date from which dividends will accumulate;

• the procedures for any auction and remarketing, if applicable;

• the provisions for a sinking fund, if applicable;

• the provisions for redemption or repurchase, if applicable, and any restrictions on our ability to exercise those redemption and repurchase rights;

• any listing of the preferred stock on any securities exchange or market;

• whether the preferred stock will be convertible into our common stock, and, if applicable, the conversion price, or how it will be calculated, and the conversion period;

• whether the preferred stock will be exchangeable into debt securities, and, if applicable, the exchange price, or how it will be calculated, and the exchange period;

• voting rights of the preferred stock;

• preemptive rights, if any;

• restrictions on transfer, sale or other assignment;

• whether interests in the preferred stock will be represented by depositary shares;

• a discussion of material United States federal income tax considerations applicable to the preferred stock;

• the relative ranking and preferences of the preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs;

• any limitations on the issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs; and

• any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

Anti-Takeover Effects of Provisions of our Amended and Restated Certificate of Incorporation, our Amended and Restated Bylaws and Delaware Law

Certain provisions of Delaware law and our amended and restated certificate of incorporation and our amended and restated bylaws contain provisions that could make the following transactions more difficult: acquisition of us by means of a tender offer; acquisition of us by means of a proxy contest or otherwise; or removal of our incumbent officers and directors. It is possible that these provisions could make it more difficult to accomplish or could deter transactions that stockholders may otherwise consider to be in their best interest or in our best interests, including transactions that might result in a premium over the market price for our shares.

These provisions, summarized below, are expected to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first

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negotiate with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us outweigh the disadvantages of discouraging these proposals because negotiation of these proposals could result in an improvement of their terms.

Delaware Anti-Takeover Statute

We are subject to Section 203 of the Delaware General Corporation Law, which prohibits persons deemed “interested stockholders” from engaging in a “business combination” with a publicly-held Delaware corporation for three years following the date these persons become interested stockholders unless the business combination is, or the transaction in which the person became an interested stockholder was, approved in a prescribed manner or another prescribed exception applies. Generally, an “interested stockholder” is a person who, together with affiliates and associates, owns or within three years prior to the determination of interested stockholder status did own, 15% or more of a corporation’s voting stock. Generally, a “business combination” includes a merger, asset or stock sale or other transaction resulting in a financial benefit to the interested stockholder. The existence of this provision may have an anti-takeover effect with respect to transactions not approved in advance by the board of directors, such as discouraging takeover attempts that might result in a premium over the market price of our common stock.

Undesignated Preferred Stock

The ability to authorize undesignated preferred stock makes it possible for our board of directors to issue preferred stock with voting or other rights or preferences that could impede the success of any attempt to change control of us. These and other provisions may have the effect of deterring hostile takeovers or delaying changes in control or management of our company.

Special Stockholder Meetings

Our amended and restated bylaws provide that a special meeting of stockholders may be called at any time by our board of directors or the chairperson of the board of directors, or our chief executive officer, but such special meetings may not be called by the stockholders or any other person or persons.

Requirements for Advance Notification of Stockholder Nominations and Proposals

Our amended and restated bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of the board of directors or a committee of the board of directors.

Elimination of Stockholder Action by Written Consent

Our amended and restated certificate of incorporation and our amended and restated bylaws eliminate the right of stockholders to act by written consent without a meeting.

Classified Board; Election and Removal of Directors; Filling Vacancies

Our board of directors is divided into three classes. The directors in each class will serve for a three-year term, one class being elected each year by our stockholders, with staggered three-year terms. Only one class of directors will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms. Because our stockholders do not have cumulative voting rights, our stockholders holding a majority of the shares of our common stock outstanding will be able to elect all of our directors. Our amended and restated certificate of incorporation provides for the removal of any of our directors only for cause and requires a stockholder vote by the holders of at least a 66 2/3% of the voting power of the then

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outstanding voting stock. Furthermore, any vacancy on our board of directors, however occurring, including a vacancy resulting from an increase in the size of the board, may only be filled by a resolution of the board of directors unless the board of directors determines that such vacancies shall be filled by the stockholders. This system of electing and removing directors and filling vacancies may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of us, because it generally makes it more difficult for stockholders to replace a majority of the directors.

Choice of Forum

Our amended and restated certificate of incorporation provides that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the exclusive forum for:

• any derivative action or proceeding brought on behalf of FibroGen;

• any action asserting a claim of breach of a fiduciary duty owed by any director, officer or other employee of FibroGen to FibroGen or FibroGen’s stockholders;

• any action asserting a claim against FibroGen arising pursuant to any provision of the Delaware General Corporation Law, the amended and restated certificate of incorporation or amended and restated bylaws of FibroGen; or

• any action asserting a claim against FibroGen governed by the internal affairs doctrine.

As a result, any action brought by any of our stockholders with regard to any of these matters will need to be filed in the Court of Chancery of the State of Delaware and cannot be filed in any other jurisdiction; provided that, the exclusive forum provision will not apply to suits brought to enforce any liability or duty created by the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction.

Although our amended and restated certificate of incorporation contains the choice of forum provision described above, it is possible that a court could find that such a provision is inapplicable for a particular claim or action or that such provision is unenforceable.

This choice of forum provision may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or any of our directors, officers, other employees or stockholders, which may discourage lawsuits with respect to such claims, although our stockholders will not be deemed to have waived our compliance with federal securities laws and the rules and regulations thereunder.

Amendment of Charter Provisions

The amendment of any of the above provisions in our amended and restated certificate of incorporation, except for the provision setting forth the authorized number of shares of our capital stock and making it possible for our board of directors to issue undesignated preferred stock, would require approval by a stockholder vote by the holders of at least a 66 2/3% of the voting power of the then outstanding voting stock.

The provisions of the Delaware General Corporation Law, our amended and restated certificate of incorporation and our amended and restated bylaws could have the effect of discouraging others from attempting hostile takeovers and, as a consequence, they may also inhibit temporary fluctuations in the market price of our common stock that often result from actual or rumored hostile takeover attempts. These provisions may also have the effect of preventing changes in our management. It is possible that these provisions could make it more difficult to accomplish transactions that stockholders may otherwise deem to be in their best interests.

Limitation of Liability and Indemnification Matters

Our amended and restated certificate of incorporation contains provisions that limit the liability of our directors for monetary damages to the fullest extent permitted by Delaware law. Consequently, our directors will

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not be personally liable to us or our stockholders for monetary damages for any breach of fiduciary duties as directors, except liability for:

• any breach of the director’s duty of loyalty to us or our stockholders;

• any act or omission not in good faith or that involves intentional misconduct or a knowing violation of law;

• unlawful payments of dividends or unlawful stock repurchases or redemptions as provided in Section 174 of the Delaware General Corporation Law; or

• any transaction from which the director derived an improper personal benefit.

Each of our amended and restated certificate of incorporation and amended and restated bylaws provide that we are required to indemnify our directors and officers, in each case to the fullest extent permitted by Delaware law. Our amended and restated bylaws also obligate us to advance expenses incurred by a director or officer in advance of the final disposition of any action or proceeding, and permit us to secure insurance on behalf of any officer, director, employee or other agent for any liability arising out of his or her actions in that capacity regardless of whether we would otherwise be permitted to indemnify them under Delaware law. We have entered and expect to continue to enter into agreements to indemnify our directors, officers and other employees as determined by our board of directors. With specified exceptions, these agreements provide for indemnification for related expenses including, among other things, attorneys’ fees, judgments, fines and settlement amounts incurred by any of these individuals in any action or proceeding. We believe that these bylaw provisions and indemnification agreements are necessary to attract and retain qualified persons as directors and officers. We also maintain directors’ and officers’ liability insurance.

The limitation of liability and indemnification provisions in our amended and restated certificate of incorporation and amended and restated bylaws may discourage stockholders from bringing a lawsuit against our directors and officers for breach of their fiduciary duty. They may also reduce the likelihood of derivative litigation against our directors and officers, even though an action, if successful, might benefit us and our stockholders. Further, a stockholder’s investment may be adversely affected to the extent that we pay the costs of settlement and damages.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC. Its address is 6201 15th Avenue, Brooklyn, New York 11219. The transfer agent for any series of preferred stock that we may offer under this prospectus will be named and described in the prospectus supplement related to that series.

Listing on the Nasdaq Global Select Market

Our common stock is listed on the Nasdaq Global Select Market the symbol “FGEN.” The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on the Nasdaq Global Select Market or any securities market or other exchange of the preferred stock covered by such prospectus supplement.

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DESCRIPTION OF DEBT SECURITIES

We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any debt securities that we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. The terms of any debt securities offered under a prospectus supplement may differ from the terms described below. Unless the context requires otherwise, whenever we refer to the indenture, we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

We will issue the debt securities under the indenture that we will enter into with the trustee named in the indenture. The indenture will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We have filed the form of indenture as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

The following summary of material provisions of the debt securities and the indenture is subject to, and qualified in its entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectus related to the debt securities that we may offer under this prospectus, as well as the complete indenture that contains the terms of the debt securities.

General

The indenture does not limit the amount of debt securities that we may issue. It provides that we may issue debt securities up to the principal amount that we may authorize and may be in any currency or currency unit that we may designate. Except for the limitations on consolidation, merger and sale of all or substantially all of our assets contained in the indenture, the terms of the indenture do not contain any covenants or other provisions designed to give holders of any debt securities protection against changes in our operations, financial condition or transactions involving us.

We may issue the debt securities issued under the indenture as “discount securities,” which means they may be sold at a discount below their stated principal amount. These debt securities, as well as other debt securities that are not issued at a discount, may be issued with “original issue discount”, or OID, for U.S. federal income tax purposes because of interest payment and other characteristics or terms of the debt securities. Material U.S. federal income tax considerations applicable to debt securities issued with OID will be described in more detail in any applicable prospectus supplement.

We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

• the title of the series of debt securities;

• any limit upon the aggregate principal amount that may be issued;

• the maturity date or dates;

• the form of the debt securities of the series;

• the applicability of any guarantees;

• whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;

• whether the debt securities rank as senior debt, senior subordinated debt, subordinated debt or any combination thereof, and the terms of any subordination;

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• if the price (expressed as a percentage of the aggregate principal amount thereof) at which such debt securities will be issued is a price other than the principal amount thereof, the portion of the principal amount thereof payable upon declaration of acceleration of the maturity thereof, or if applicable, the portion of the principal amount of such debt securities that is convertible into another security or the method by which any such portion shall be determined;

• the interest rate or rates, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

• our right, if any, to defer payment of interest and the maximum length of any such deferral period;

• if applicable, the date or dates after which, or the period or periods during which, and the price or prices at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;

• the date or dates, if any, on which, and the price or prices at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder’s option to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;

• the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;

• any and all terms, if applicable, relating to any auction or remarketing of the debt securities of that series and any security for our obligations with respect to such debt securities and any other terms which may be advisable in connection with the marketing of debt securities of that series;

• whether the debt securities of the series shall be issued in whole or in part in the form of a global security or securities;

• the terms and conditions, if any, upon which such global security or securities may be exchanged in whole or in part for other individual securities, and the depositary for such global security or securities;

• if applicable, the provisions relating to conversion or exchange of any debt securities of the series and the terms and conditions upon which such debt securities will be so convertible or exchangeable, including the conversion or exchange price, as applicable, or how it will be calculated and may be adjusted, any mandatory or optional (at our option or the holders’ option) conversion or exchange features, the applicable conversion or exchange period and the manner of settlement for any conversion or exchange;

• if other than the full principal amount thereof, the portion of the principal amount of debt securities of the series which shall be payable upon declaration of acceleration of the maturity thereof;

• additions to or changes in the covenants applicable to the particular debt securities being issued, including, among others, the consolidation, merger or sale covenant;

• additions to or changes in the events of default with respect to the securities and any change in the right of the trustee or the holders to declare the principal, premium, if any, and interest, if any, with respect to such securities to be due and payable;

• additions to or changes in or deletions of the provisions relating to covenant defeasance and legal defeasance;

• additions to or changes in the provisions relating to satisfaction and discharge of the indenture;

• additions to or changes in the provisions relating to the modification of the indenture both with and without the consent of holders of debt securities issued under the indenture;

• the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars;

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• whether interest will be payable in cash or additional debt securities at our or the holders’ option and the terms and conditions upon which the election may be made;

• the terms and conditions, if any, upon which we will pay amounts in addition to the stated interest, premium, if any and principal amounts of the debt securities of the series to any holder that is not a “United States person” for federal tax purposes;

• any restrictions on transfer, sale or assignment of the debt securities of the series; and

• any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, any other additions or changes in the provisions of the indenture, and any terms that may be required by us or advisable under applicable laws or regulations.

Conversion or Exchange Rights

We will set forth in the applicable prospectus supplement the terms on which a particular series of debt securities may be convertible into or exchangeable for our common stock or our other securities. We will include provisions as to settlement upon conversion or exchange and whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock or our other securities that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indenture will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of our assets as an entirety or substantially as an entirety. However, any successor to or acquirer of such assets (other than a subsidiary of ours) must assume all of our obligations under the indenture or the debt securities, as appropriate.

Events of Default under the Indenture

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indenture with respect to any series of debt securities that we may issue:

• if we fail to pay any installment of interest on any series of debt securities, as and when the same shall become due and payable, and such default continues for a period of 90 days; provided, however, that a valid extension of an interest payment period by us in accordance with the terms of any indenture supplemental thereto shall not constitute a default in the payment of interest for this purpose;

• if we fail to pay the principal of, or premium, if any, on any series of debt securities as and when the same shall become due and payable whether at maturity, upon redemption, by declaration or otherwise, or in any payment required by any sinking or analogous fund established with respect to such series; provided, however, that a valid extension of the maturity of such debt securities in accordance with the terms of any indenture supplemental thereto shall not constitute a default in the payment of principal or premium, if any;

• if we fail to observe or perform any other covenant or agreement contained in the debt securities or the indenture, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive written notice of such failure, requiring the same to be remedied and stating that such is a notice of default thereunder, from the trustee or holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and

• if specified events of bankruptcy, insolvency or reorganization occur.

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If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, if any, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indenture, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

• the direction so given by the holder is not in conflict with any law or the applicable indenture; and

• subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

A holder of the debt securities of any series will have the right to institute a proceeding under the indenture or to appoint a receiver or trustee, or to seek other remedies only if:

• the holder has given written notice to the trustee of a continuing event of default with respect to that series;

• the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made written request,

• such holders have offered to the trustee indemnity satisfactory to it against the costs, expenses and liabilities to be incurred by the trustee in compliance with the request; and

• the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, if any, the debt securities.

We will periodically file statements with the trustee regarding our compliance with specified covenants in the indenture.

Modification of Indenture; Waiver

We and the trustee may change an indenture without the consent of any holders with respect to specific matters:

• to cure any ambiguity, defect or inconsistency in the indenture or in the debt securities of any series;

• to comply with the provisions described above under “Description of Debt Securities—Consolidation, Merger or Sale;”

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• to provide for uncertificated debt securities in addition to or in place of certificated debt securities;

• to add to our covenants, restrictions, conditions or provisions such new covenants, restrictions, conditions or provisions for the benefit of the holders of all or any series of debt securities, to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred upon us in the indenture;

• to add to, delete from or revise the conditions, limitations, and restrictions on the authorized amount, terms, or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;

• to make any change that does not adversely affect the interests of any holder of debt securities of any series in any material respect;

• to provide for the issuance of and establish the form and terms and conditions of the debt securities of any series as provided above under “Description of Debt Securities—General” to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;

• to evidence and provide for the acceptance of appointment under any indenture by a successor trustee; or

• to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act.

In addition, under the indenture, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

• extending the fixed maturity of any debt securities of any series;

• reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption of any series of debt securities; or

• reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

• provide for payment;

• register the transfer or exchange of debt securities of the series;

• replace stolen, lost or mutilated debt securities of the series;

• pay principal of and premium, if any, and interest, if any, on any debt securities of the series;

• maintain paying agencies;

• hold monies for payment in trust;

• recover excess money held by the trustee;

• compensate and indemnify the trustee; and

• appoint any successor trustee.

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In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest, if any, on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue the debt securities of each series only in fully registered form without coupons and, unless we provide otherwise in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indenture provides that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company, or DTC, or another depositary named by us and identified in the applicable prospectus supplement with respect to that series. To the extent the debt securities of a series are issued in global form and as book-entry, a description of terms relating to any book entry securities will be set forth in the applicable prospectus supplement.

At the option of the holder, subject to the terms of the indenture and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indenture and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will impose no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

If we elect to redeem the debt securities of any series, we will not be required to:

• issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or

• register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Trustee

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indenture at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

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Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

The indenture and the debt securities will be governed by and construed in accordance with the internal laws of the State of New York, except to the extent that the Trust Indenture Act of 1939 is applicable.

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DESCRIPTION OF WARRANTS

The following description, together with the additional information we may include in any applicable prospectus supplements and in any related free writing prospectus that we may authorize to be distributed to you, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase common stock, preferred stock or debt securities and be issued in one or more series. Warrants may be offered independently or in combination with common stock, preferred stock or debt securities offered by any prospectus supplement. While the terms we have summarized below will apply generally to any warrants that we may offer under this prospectus, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. The following description of warrants will apply to the warrants offered by this prospectus unless we provide otherwise in the applicable prospectus supplement. The applicable prospectus supplement for a particular series of warrants may specify different or additional terms.

We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the complete form of warrant and/or the warrant agreement and warrant certificate, as applicable, that describe the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants. The following summaries of material terms and provisions of the warrants are subject to, and qualified in their entirety by reference to, all the provisions of the form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements applicable to a particular series of warrants that we may offer under this prospectus. We urge you to read the applicable prospectus supplement related to the particular series of warrants that we may offer under this prospectus, as well as any related free writing prospectus, and the complete form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements, that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms of the series of warrants being offered, including:

• the offering price and aggregate number of warrants offered;

• the currency for which the warrants may be purchased;

• if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

• in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;

• in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;

• the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreements and the warrants;

• the terms of any rights to redeem or call the warrants;

• any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

• the dates on which the right to exercise the warrants will commence and expire;

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• the manner in which the warrant agreements and warrants may be modified;

• a discussion of any material or special U.S. federal income tax considerations of holding or exercising the warrants;

• the terms of the securities issuable upon exercise of the warrants; and

• any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

• in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, if any, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or

• in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. The warrants may be exercised as set forth in the prospectus supplement relating to the warrants offered. Unless we otherwise specify in the applicable prospectus supplement, warrants may be exercised at any time up to the close of business on the expiration date set forth in the prospectus supplement relating to the warrants offered thereby. After the close of business on the expiration date, unexercised warrants will become void.

Upon receipt of payment and the warrant or warrant certificate, as applicable, properly completed and duly executed at the corporate trust office of the warrant agent, if any, or any other office, including ours, indicated in the prospectus supplement, we will, as soon as practicable, issue and deliver the securities purchasable upon such exercise. If less than all of the warrants (or the warrants represented by such warrant certificate) are exercised, a new warrant or a new warrant certificate, as applicable, will be issued for the remaining warrants.

Governing Law

Unless we otherwise specify in the applicable prospectus supplement, the warrants and any warrant agreements will be governed by and construed in accordance with the laws of the State of New York.

Enforceability of Rights by Holders of Warrants

Each warrant agent, if any, will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

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LEGAL OWNERSHIP OF SECURITIES

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a book-entry security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

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For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depositary participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the holders.

Special Considerations For Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

• how it handles securities payments and notices;

• whether it imposes fees or charges;

• how it would handle a request for the holders’ consent, if ever required;

• whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;

• how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

• if the securities are in book-entry form, how the depositary’s rules and procedures will affect these matters.

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, DTC will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under the section titled “Special Situations When a Global Security Will Be Terminated” in this prospectus. As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a bank, broker, or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

The rights of an indirect holder relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

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If securities are issued only in the form of a global security, an investor should be aware of the following:

• an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

• an investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

• an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

• an investor may not be able to pledge his or her interest in a global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

• the depositary’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor’s interest in a global security;

• we and any applicable trustee have no responsibility for any aspect of the depositary’s actions or for its records of ownership interests in a global security, nor do we or any applicable trustee supervise the depositary in any way;

• the depositary may, and we understand that DTC will, require that those who purchase and sell interests in a global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and

• financial institutions that participate in the depositary’s book-entry system, and through which an investor holds its interest in a global security, may also have their own policies affecting payments, notices and other matters relating to the securities.

There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated

In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in the applicable prospectus supplement, the global security will terminate when the following special situations occur:

• if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

• if we notify any applicable trustee that we wish to terminate that global security; or

• if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The applicable prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the applicable prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

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PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, direct sales to the public, negotiated transactions, block trades or a combination of these methods. We may sell the securities to or through one or more underwriters or dealers, through agents, or directly to one or more purchasers. We may distribute securities from time to time in one or more transactions:

• at a fixed price or prices, which may be changed;

• at market prices prevailing at the time of sale;

• at prices related to such prevailing market prices; or

• at negotiated prices.

A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

• the name or names of the underwriters, if any;

• the purchase price of the securities or other consideration therefor, and the proceeds, if any, we will receive from the sale;

• any over-allotment options under which underwriters may purchase additional securities from us;

• any agency fees or underwriting discounts and other items constituting agents’ or underwriters’ compensation;

• any public offering price;

• any discounts or concessions allowed or reallowed or paid to dealers; and

• any securities exchange or market on which the securities may be listed.

Only underwriters named in the prospectus supplement will be underwriters of the securities offered by the prospectus supplement. Dealers and agent participating in the distribution of securities may be deemed to be underswriters, and compensation received by them on resale of the securities may be deemed to be underwriting discounts. If such dealers or agents were deemed to be underwriters, they may be subject to statutory liabilities under the Securities Act.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the prospectus supplement, other than securities covered by any over-allotment option or option to purchase additional shares. If a dealer is used in the sale of securities, we, or an underwrite, will sell the securities to the dealer, as principal. The deal may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale. To the extent required, we will set forth in the prospectus supplement the name of the dealer and ther terms of the transaction. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time. We may use underwriters, dealers or agents with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, dealer or agent, and the nature of any such relationship.

We may sell securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities and we will describe any commissions we will pay the agent in the prospectus supplement. Unless the applicable prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

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We may authorize agents, dealers or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

We may provide agents, dealers and underwriters with indemnification against civil liabilities, including liabilities under the Securities Act, or contribution with respect to payments that the agents, dealers or underwriters may make with respect to these liabilities. Agents, dealers and underwriters or their affilaites may engage in transactions with, or perform services for, us in the ordinary course of business.

All securities we may offer, other than common stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Over-allotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum price. Syndicate-covering or other short-covering transactions involve purchases of the securities, either through exercise of the over-allotment option or in the open market after the distribution is completed, to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a stabilizing or covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

Any underwriters, dealers or agents that are qualified market makers on the Nasdaq Global Select Market may engage in passive market making transactions in our common stock on the Nasdaq Global Select Market in accordance with Regulation M under the Exchange Act, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the common stock. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker’s bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded. Passive market making may stabilize the market price of the securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

In compliance with guidelines of the Financial Industry Regulatory Authority, or FINRA, the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and any applicable prospectus supplement.

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LEGAL MATTERS

Cooley LLP, Palo Alto, California, will pass upon the validity of the securities offered by this prospectus, and any supplement thereto, unless otherwise indicated in the applicable prospectus supplement. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Annual Report on Internal Control over Financial Reporting) incorporated in this Prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2023 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

This prospectus is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth or incorporated by reference in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document. Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this prospectus and the registration statement of which this prospectus is a part the information or documents listed below that we have filed with the SEC (Commission File No. 001-36740):

• Our Annual Report on Form 10-K for the year ended December 31, 2023, filed with the SEC on February 26, 2024;

• The information incorporated by reference in our Annual Report on Form 10-K for the year ended December  31, 2024 from our proxy statement on Schedule 14A, filed with the SEC on April 24, 2024;

• Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2024, filed with the SEC on May 6, 2024;

• our Current Reports on Form 8-K filed with the SEC on June 7, 2024 and June 26, 2024;

• the description of our common stock set forth in our registration statement on Form 8-A, filed with the SEC on November  12, 2014, including any additional amendment or report filed for the purpose of updating such description, including Exhibit 4.4 to our Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020.

All filings filed by us pursuant to the Exchange Act after the date of the initial filing of the registration statement of which this prospectus is a part and prior to effectiveness of the registration statement shall be deemed to be incorporated by reference into this prospectus.

We also incorporate by reference any future filings (other than current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including those made after the date of the initial filing of the registration statement of which this prospectus is a part until we file a post-effective amendment that indicates the termination of the offering of the securities made by this prospectus, which will become a part of this prospectus from the date that such documents are filed with the SEC. Information in such future filings updates and supplements the information provided in this prospectus. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later-filed document modify or replace such earlier statements. We will furnish without charge to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request, a copy of any or all of the documents incorporated by reference into this prospectus but not delivered with the prospectus, including exhibits that are specifically incorporated by reference into such documents. You should direct any requests for documents to:

FibroGen, Inc.

Attn: Investor Relations

409 Illinois Street

San Francisco, California 94158

Telephone number: (415) 978-1200

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$30,000,000

Common Stock

PROSPECTUS SUPPLEMENT

BofA Securities

February 24, 2025