Zosano Pharma (ZSANQ) 424B5 Prospectus supplement for primary offering

Filed Pursuant to Rule 424(b)(5)
Registration Statement No. 333-257682

Prospectus Supplement

(To Prospectus dated July 14, 2021)

51,250,000 Units Each Consisting of One Share of Common Stock and One Series F Warrant to Purchase One Share of Common Stock

Zosano Pharma Corporation

We are offering 51,250,000 Units, with each Unit consisting of one share of common stock, par value $0.0001 per share, and one Series F Warrant (“Series F Warrant”) to purchase one share of common stock (together with the share of common stock underlying each Series F Warrant, the “Units”) at a public offering price of $0.30 per Unit. Each Series F Warrant included in the Units entitles its holder to purchase one share of common stock at an exercise price per share of $0.30.

The Units have no stand-alone rights and will not be certificated or issued as stand-alone securities. The shares of common stock and the Series F Warrants comprising such units are immediately separable and will be issued separately, but will be purchased together in this offering. The Series F Warrants offered hereby may be exercised from time to time beginning on the issuance date and expire on the five-year anniversary of the issuance date.

Our common stock is listed on the Nasdaq Capital Market under the symbol “ZSAN.” The last reported sale price of our common stock on February 8, 2022 was $0.4726 per share. There is no established public trading market for the Series F Warrants. We do not intend to apply for listing of the Series F Warrants on any securities exchange or recognized trading system.

This investment involves a high degree of risk. Before making an investment decision, please read the information under the heading “Risk Factors” beginning on page S-11 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 passed upon the adequacy or accuracy of this prospectus supplement or the prospectus to which it relates. Any representation to the contrary is a criminal offense.

	PER UNIT		TOTAL
Public offering price	$	0.30	$	15,375,000
Underwriting discounts and commissions(1)	$	0.0165	$	845,625
Proceeds, before expenses, to us(2)	$	0.2835	$	14,529,375

(1) We have agreed to reimburse the underwriter for certain expenses. See “Underwriting.”

(2) The amount of the offering proceeds to us presented in this table does not give effect to any exercise of the Series F Warrants being issued in this offering.

We have granted the underwriter an option to purchase up to 7,687,500 additional shares of common stock and/or additional Series F Warrants to purchase up to 7,687,500 shares of common stock (equal to 15% of the shares of common stock and 15% of the Series F Warrants in the offering), at the applicable price to the public of $0.29 per share or $0.01 per Series F Warrant, less the underwriting discounts and commissions. This option is exercisable for 30 days from the date of this prospectus supplement.

The underwriters expect to deliver the securities on or about February 10, 2022.

Sole Book-Running Manager

Maxim Group LLC

The date of this prospectus supplement is February 8, 2022.

TABLE OF CONTENTS

Prospectus Supplement

ABOUT THIS PROSPECTUS SUPPLEMENT	S-1
FORWARD-LOOKING STATEMENTS	S-2
PROSPECTUS SUPPLEMENT SUMMARY	S-4
THE OFFERING	S-8
RISK FACTORS	S-11
USE OF PROCEEDS	S-15
DIVIDEND POLICY	S-16
DESCRIPTION OF SECURITIES WE ARE OFFERING	S-17
CERTAIN MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS	S-20
UNDERWRITING	S-27
LEGAL MATTERS	S-31
EXPERTS	S-31
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE	S-32

Prospectus

	Page
About This Prospectus		1
Where You Can Find More Information; Incorporation by Reference		2
The Company		4	��
Risk Factors		5
Use of Proceeds		6
Description of Capital Stock		7
Description of Debt Securities		9
Description of Warrants		17
Description of Units		19
Global Securities		20
Plan of Distribution		24
Legal Matters		26
Experts		26

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ABOUT THIS PROSPECTUS SUPPLEMENT

We provide information to you about this offering in two separate documents that are bound together: (1) this prospectus supplement, which describes the specific details regarding this offering; and (2) the accompanying base prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. If information in this prospectus supplement is inconsistent with the accompanying base prospectus, you should rely on this prospectus supplement. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in this prospectus supplement—the statement in the document having the later date modifies or supersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlier dates.

We have not authorized anyone to provide you with any information or to make any representation, other than those contained or incorporated by reference in this prospectus supplement or in any free writing prospectus we have prepared. We take no responsibility for, and provide no assurance as to the reliability of, any other information that others may give you. Neither we nor the underwriter are making an offer to sell or soliciting an offer to buy our securities in any jurisdiction where 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 supplement, the accompanying base prospectus, the documents incorporated by reference into this prospectus, 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 supplement, the accompanying base prospectus, 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 section of this prospectus supplement entitled “Where You Can Find More Information; Incorporation by Reference.”

We are offering to sell, and seeking offers to buy, securities only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the accompanying base prospectus and the offering of the securities in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying base prospectus must inform themselves about, and observe any restrictions relating to, the offering of the securities and the distribution of this prospectus supplement and the accompanying base prospectus outside the United States. This prospectus supplement and the accompanying base 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 accompanying base prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

When we refer to “we,” “our,” “us” and the “Company” in this prospectus, we mean Zosano Pharma Corporation, unless otherwise specified. When we refer to “you,” we mean the prospective investors in the Company.

This prospectus contains references to our trademarks and to trademarks belonging to other entities, which are protected under applicable intellectual property laws. Solely for convenience, our trademarks and tradenames referred to in this prospectus supplement appear without the ^® and ^™ symbol, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights, or the right of the applicable licensor to these trademarks and tradenames.

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FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying base prospectus, the documents incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering contain forward-looking statements concerning our business, operations and financial performance and condition, as well as our plans, objectives and expectations for our business, operations and financial performance and condition. Any statements contained herein that are not statements of historical facts may be deemed to be forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “predict,” “potential,” “positioned,” “seek,” “should,” “target,” “will,” “would” and other similar expressions that are predictions or indicate future events and future trends, or the negative of these terms or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

• our expectations regarding our expenses and revenue, the sufficiency of our cash resources and needs for additional financing;

• our resubmission strategy for our 505(b)(2) New Drug Application (“NDA”) for M207 to the U.S. Food and Drug Administration (the “FDA”);

• our expectations regarding the clinical effectiveness and safety of our product candidates;

• the ability to obtain and maintain regulatory approval of our product candidates, and the labeling for any approved product;

• our manufacturing capabilities and strategy, and our ability to establish and maintain relationships with contract manufacturing organization(s) (“CMOs”) to expand our manufacturing capacity;

• the anticipated timing, costs and conduct of our planned clinical trials and preclinical studies;

• our intellectual property position and our ability to obtain and maintain intellectual property protection for our product candidates;

• our expectations regarding competition;

• the anticipated trends and challenges in our business and the markets in which we operate;

• the scope, progress, expansion and costs of developing and commercializing our product candidates;

• the impact of the COVID-19 pandemic, including its impact on us and our operations;

• the size and growth of the potential markets for our product candidates and the ability to serve those markets;

• the rate and degree of market acceptance of our product candidates;

• our ability to establish and maintain development partnerships;

• our ability to attract or retain key personnel;

• our expectations regarding federal, state and foreign regulatory requirements;

• regulatory developments in the United States and foreign countries; and

• the intended use of proceeds from this offering.

These forward-looking statements are based on management’s current expectations, estimates, forecasts and projections about our business and the industry in which we operate and involve known and unknown risks, uncertainties and other factors that are in some cases beyond our control. As a result, any or all of our forward-looking statements in this prospectus may turn out to be inaccurate. Factors that may cause actual results to differ materially from current expectations include, among other things, those listed under “Risk Factors” and

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elsewhere in this prospectus. Potential investors are urged to consider these factors carefully in evaluating the forward-looking statements. These forward-looking statements speak only as of the date hereof and as of the dates indicated in these statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future. Given these risks and uncertainties, you are cautioned not to rely on such forward-looking statements as predictions of future events. You should, however, review the factors and risks we describe in the reports we will file from time to time with the SEC after the date of this prospectus. See “Where You Can Find More Information; Incorporation by Reference.”

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PROSPECTUS SUPPLEMENT SUMMARY

This summary provides a general overview of selected information and does not contain all of the information you should consider before buying our securities. Therefore, you should read the entire prospectus supplement, accompanying base prospectus and any free writing prospectus that we have authorized for use in connection with this offering carefully, including the information incorporated by reference, before deciding to invest in our securities. Investors should carefully consider the information set forth under “Risk Factors” beginning on page S-11 and incorporated by reference to our Quarterly Report on Form 10-Q for the quarter ended September 30, 2021.

Overview

We are a clinical-stage biopharmaceutical company focused on providing rapid systemic administration of therapeutics and other bioactive molecules to patients using our proprietary transdermal microneedle system.

On January 18, 2022, we resubmitted our M207 (zolmitriptan transdermal microneedle system) 505(b)(2) NDA to the FDA following our receipt of a Complete Response Letter relating to such product candidate on October 20, 2020.

In line with our previously disclosed resubmission strategy, the NDA has been resubmitted under Section 505(b)(2) of the Food, Drug, and Cosmetic Act and relies on the FDA’s findings of safety and efficacy of ZOMIG^® nasal spray (NDA 21-450) (the “Listed Drug”). The resubmitted NDA relies primarily on data from the recently completed Phase 1 pharmacokinetic (“PK”) study (CP 2021-001), along with previous PK studies (CP-2018-002 and CP-2019-002) evaluating M207, to potentially establish a PK bridge to the Listed Drug, with the goal of establishing comparative bioavailability to the Listed Drug. Prior to the resubmission, the FDA provided us with written feedback which, among other things, noted concerns regarding our approach for establishing a PK bridge to the Listed Drug through comparisons across multiple PK studies of M207, particularly Study CP-2019-002, which included PK outliers.

We believe that the data provided in our resubmitted NDA demonstrates an adequate bridge to the Listed Drug. With this resubmission that includes additional PK data from our CP 2021-001 study, the FDA can evaluate and determine the adequacy of the data package to potentially support M207 approval, though there can be no assurances that the FDA will accept our view. The FDA may require additional clinical trials and may never approve M207.

Certain Preliminary Financial and Other Information

Currently, we have approximately $7.6 million in cash and cash equivalents. After taking into account our receipt of the estimated net proceeds of this offering, we expect that we will have cash and cash equivalents necessary to fund our operations through approximately July 2022. While we are exploring raising additional capital beyond this offering to enable our ongoing operations, if we cannot obtain sufficient additional capital on terms acceptable to us, or at all, we may be unable to fund our ongoing operations. Furthermore, any additional capital that we are able to raise in the near term may not be sufficient to fund our operations through potential FDA approval of the M207 NDA, even if the FDA accepts our view regarding the M207 NDA resubmission.

In addition, we have retained SierraConstellation Partners, LLC as an independent financial advisor to assist in exploring financial and strategic alternatives to maximize value, which may include, but not be limited to, asset or equity sales, joint venture and partnership opportunities, and restructuring, amendment or refinancing of existing liabilities. We are also evaluating various alternatives to improve our liquidity, including but not limited to, further reductions of operating and capital expenditures and other contractual obligations. However, there can

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be no assurances that we will be able to successfully raise capital, improve our financial position and liquidity, restructure our obligations, enter into any asset or equity sale, joint venture or partnership opportunity and/or otherwise achieve any of these objectives.

The above information is preliminary and subject to completion, including the completion of customary financial statement closing and review procedures for the quarter ended December 31, 2021 and the quarter ending March 31, 2022. As a result, the preliminary results set forth above reflect our preliminary estimates with respect to such information, based on information currently available to management, and may vary from our actual financial results. Further, these preliminary estimates are not a comprehensive statement or estimate of our financial results or financial condition as of and for the quarter ending March 31, 2022. The preliminary financial information included herein has been prepared by, and is the responsibility of, management. Deloitte & Touche LLP has not audited, reviewed, compiled or performed any procedures with respect to the preliminary financial information. Accordingly, Deloitte & Touche LLP does not express an opinion or any other form of assurance with respect thereto. These estimates should not be viewed as a substitute for financial statements prepared in accordance with accounting principles generally accepted in the United States and they are not necessarily indicative of the results to be achieved in any future period. Accordingly, you should not draw any conclusions based on the foregoing estimates and should not place undue reliance on these preliminary estimates. We assume no duty to update these preliminary estimates except as required by law.

Available Information

Our website address is www.zosanopharma.com. The information contained in, or accessible through, our website does not constitute part of this prospectus. We make available free of charge on our website our annual, quarterly and current reports, including amendments to such reports, as soon as reasonably practicable after we electronically file such material with, or furnish such material to, the Securities and Exchange Commission, or the SEC. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider information contained on our website as part of this prospectus.

Risks Associated with our Business

Our business is subject to a number of risks of which you should be aware before making an investment decision. These risks are discussed more fully in the “Risk Factors” section of this prospectus immediately following this prospectus summary and in Part II, Item 1A “Risk Factors” of our Quarterly Report on Form 10-Q for the quarter ended September 30, 2021 filed with the SEC on November 10, 2021, which is incorporated by reference in this prospectus. These risks include, but are not limited to, the following:

• We will need substantial additional funding to fund our operations, and we may not be able to continue as a going concern if we are unable to do so. We could also be forced to delay, reduce or terminate our product development, other operations or commercialization efforts.

• We have a history of operating losses. We expect to continue to incur losses over the next several years and may never become profitable.

• We have generated only limited revenues and will need additional capital to develop and commercialize our product candidates, which may cause dilution to our existing stockholders, restrict our operations or require us to relinquish rights to our technologies or lead product candidates.

• Our build-to-suit arrangement with Trinity Funding 1, LLC (successor to Trinity Capital Fund III, L.P.) (“Trinity”) imposes restrictions on our business, and if we default on our obligations, Trinity would have a right to request payment in full of the build-to-suit obligation.

• We have limited operating history and capabilities.

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• The development and commercialization of our product candidates are subject to many risks. For example, we received a complete response letter from the FDA in response to our NDA for M207, and based on feedback from the FDA, we conducted an additional PK study for inclusion in an NDA resubmission package. However, there is no guarantee that we will be able to adequately address the issues raised to the FDA’s satisfaction. If we do not successfully develop, receive approval for, and commercialize our product candidates, our business will be adversely affected.

• If the FDA does not conclude that our product candidates satisfy the requirements for the 505(b)(2) regulatory approval pathway, or if the requirements for approval of our product candidates under Section 505(b)(2) are not as we expect, the approval pathway for our product candidates will likely take significantly longer, cost significantly more and encounter significantly greater complications and risks than anticipated, and in any case may not be successful.

• If the FDA does not agree with our M207 NDA resubmission strategy to submit PK data primarily comparing Zomig^® nasal spray and patches produced on manufacturing equipment at our Fremont, California facility that produced patches for our long-term safety study, then the approval pathway for M207 will likely take significantly longer than expected, cost significantly more than anticipated, and may not be successful.

• If M207 is approved utilizing our current NDA resubmission strategy, we will only be able to produce limited quantities of M207 at our Fremont, CA location and we will not be able to produce M207 drug product on our manufacturing equipment at our third-party CMOs without FDA approval, which may require us to conduct additional clinical studies and incur significant time and cost, and we may not be successful. If we are unable to manufacture M207 on our manufacturing lines at our CMOs, it will limit our product availability and materially adversely impact our business.

• Clinical trials are very expensive, time-consuming and difficult to design and implement.

• The COVID-19 pandemic, including any strains or variants of the virus, could adversely impact our business, including our clinical trials.

• The results of our clinical trials may not support the intended use of M207 or any other product candidates we may develop.

• Clinical failure can occur at any stage of clinical development. Because the results of earlier clinical trials are not necessarily predictive of future results, any product candidate we advance through clinical trials may not have favorable results in later clinical trials or receive regulatory approval.

• We use customized equipment to manufacture, coat and package our transdermal microneedle system; any production or equipment performance failures could negatively impact the clinical trials of our product candidates that we may develop or sales of our product candidate(s), if approved.

• We currently depend on third-party suppliers for manufacture of certain components of our product candidates. If these manufacturers fail to provide us or our collaborators with adequate supplies of materials for clinical trials or commercial product or fail to comply with the requirements of regulatory authorities, we may be unable to develop or commercialize M207 or any other product candidates we may develop.

• We rely on CMOs for various components of our transdermal microneedle system, and our business could be harmed if those third parties fail to provide us with sufficient quantities of those components at acceptable quality levels and prices or fail to maintain or achieve satisfactory regulatory compliance.

• We rely on third parties to conduct our clinical trials and those third parties may not perform satisfactorily, including failing to comply with applicable regulatory requirements or to meet deadlines for the completion of such trials.

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• We have no experience selling, marketing or distributing approved product candidates and currently have no internal capabilities to do so, and will rely on Eversana and other third parties for the commercialization of M207 or may need to develop an internal sales organization, and we and they may not be able to effectively market, sell and distribute M207, if approved. In addition, Eversana may terminate our master services agreement because we did not receive FDA approval of M207 by December 31, 2021. Also, the amendment to the Eversana agreement provides that, if the NDA is approved, the deferral mechanism, payment terms and loan terms in the master services agreement will be adjusted as mutually agreed by both parties. There is no guarantee that we and Eversana will reach an agreement on the deferral mechanism, payment terms and loan terms.

• If we fail to comply with our obligations to our licensor in our intellectual property license, we could lose license rights that are important to our business.

• Our failure to obtain and maintain patent protection for our technology and our product candidates could permit our competitors to develop and commercialize technology and products similar or identical to ours, and our ability to successfully commercialize our technology and product candidate may be adversely affected.

• We are highly dependent on key executive officers and the research and development, clinical, manufacturing, financial and business development expertise of our executive officers and other employees at our Fremont, CA facility with extensive knowledge of our technology and manufacturing processes. If we are not able to adequately retain our officers or train and retain staff at our Fremont, CA facility, our ability to obtain FDA approval and commercialize M207, if approved, would be impacted and our business would be materially adversely affected.

• The trading price of our common stock has been volatile with substantial price fluctuations on heavy volume, which could result in substantial losses for purchasers of our common stock and existing stockholders.

• If we are unable to maintain listing of our securities on the Nasdaq Capital Market or another reputable stock exchange, it may be more difficult for our stockholders to sell their securities.

Corporate Information

We were incorporated under the laws of the State of Delaware as ZP Holdings, Inc. in January 2012, and changed our name to Zosano Pharma Corporation in June 2014. Our business was spun out of ALZA Corporation, a subsidiary of Johnson & Johnson, in October 2006. We were originally incorporated under the name The Macroflux Corporation, and changed our name to Zosano Pharma, Inc. in 2007 following the spin-off from Johnson & Johnson. In April 2012, in a transaction to recapitalize the business, a wholly-owned subsidiary of ZP Holdings was merged with and into Zosano Pharma, Inc., whereby Zosano Pharma, Inc. was the surviving entity and became a wholly-owned subsidiary of ZP Holdings. In June 2014, Zosano Pharma, Inc. changed its name to ZP Opco, Inc. ZP Group LLC, a former subsidiary that was originally formed as a joint venture with Asahi Kasei Pharmaceuticals USA (Asahi), ceased operations in December 2013 and was dissolved on December 30, 2016. On November 1, 2017, ZP Opco, Inc. merged with and into Zosano Pharma Corporation, with Zosano Pharma Corporation as the surviving corporation of the merger.

Our principal executive offices are located at 34790 Ardentech Court, Fremont, California 94555. Our telephone number is (510) 745-1200. Our website address is www.zosanopharma.com. The information contained on our website is not incorporated by reference into this prospectus, and you should not consider any information contained on, or that can be accessed through, our website as part of this prospectus or in deciding whether to purchase our securities.

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THE OFFERING

Units offered by us We are offering 51,250,000 Units. Each Unit consists of one share of common stock and one Series F Warrant to purchase one share of common stock. This prospectus also relates to the offering of shares of our common stock issuable upon the exercise of the Series F Warrants included in the Units.

Offering price per Unit $0.30.

Option to purchase additional securities The underwriter has the option to purchase up to 7,687,500 additional shares of common stock and/or additional Series F Warrants to purchase up to 7,687,500 shares of common stock (equal to 15% of the shares of common stock and 15% of the Series F Warrants in the offering), at the applicable price to the public of $0.29 per share or $0.01 per Series F Warrant set forth on the cover page of this prospectus, less the underwriting discounts and commissions. This option is exercisable for 30 days from the date of this prospectus supplement.

Description of Series F Warrants The Series F Warrants will be exercisable beginning on the date of issuance and expire on the five-year anniversary of the date of issuance at an initial exercise price per share equal to $0.30, subject to appropriate adjustment in the event of recapitalization events, stock dividends, stock splits, stock combinations, reclassifications, reorganizations or similar events affecting our common stock. Notwithstanding the foregoing, we shall not effect any exercise of Series F Warrants to the extent that, after giving effect to an exercise, the holder of Series F Warrants (together with such holder’s affiliates, and any persons acting as a group together with such holder or any of such holder’s affiliates) would beneficially own a number of shares of our common stock in excess of 4.99% (or, at the election of the purchaser prior to the date of issuance, 9.99%) of the shares of our common stock then outstanding after giving effect to such exercise.

Common stock to be outstanding after the offering 169,364,793 shares (assuming no exercise of the Series F Warrants and no exercise of the underwriter’s option to purchase additional securities).

Use of proceeds We estimate that the net proceeds to us from this offering will be approximately $14.0 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, and assuming no exercise of any of the Series F Warrants and no exercise of the underwriter’s option to purchase additional securities. We intend to use net proceeds from this offering for pre-commercialization activities and for general working capital and corporate purposes. See “Use of Proceeds” for additional information.

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Risk factors Investing in our securities involves a high degree of risk. See “Risk Factors” and other information included or incorporated by reference in this prospectus supplement and the accompanying base prospectus for a discussion of factors that you should consider carefully before deciding to invest in our securities.

Voting Agreement We expect that certain investors in this offering may agree to enter into a voting agreement whereby each such investor will agree to vote all shares of common stock they beneficially own on the closing date of this offering, including the shares purchased in the offering, with respect to any proposals presented to our stockholders at our next stockholders’ meeting. Such investors’ agreement to vote their shares of common stock in accordance with the immediately preceding sentence does not require the holder to vote its shares for or against any particular proposal or proposals, whether or not such proposal or proposals are recommended by our board of directors.

Nasdaq Capital Market Symbol ZSAN.

No Listing of Warrants There is no established public trading market for the Series F Warrants, and we do not intend to apply for listing of the Series F Warrants on any securities exchange or trading system. Without an active trading market, the liquidity of the Series F Warrants will be limited.

Issuance of Warrants The Series F Warrants that are purchased in the offering as part of the Units will be issued as separate warrant certificates.

The number of shares of our common stock to be outstanding immediately after this offering as shown above is based on 118,114,793 shares of common stock outstanding as of September 30, 2021, and excludes the following, in each case as of such date:

• 728,535 shares of common stock issuable upon the exercise of warrants to purchase common stock outstanding, at a weighted average exercise price of $1.08 per share;

• 4,613,658 shares of common stock issuable upon the exercise of stock options outstanding under our 2012 Stock Incentive Plan, or 2012 Plan, our Amended and Restated 2014 Equity and Incentive Plan, or 2014 Plan, and in connection with inducement awards granted outside of the plans, at a weighted average exercise price of $2.32 per share;

• 891,500 shares of common stock issuable upon the exercise of stock options outstanding under our 2014 Plan and in connection with inducement awards outside of our 2014 Plan granted after September 30, 2021, at a weighted average exercise price of $0.61 per share;

• 872,236 shares of common stock issuable upon the vesting of restricted stock units outstanding under our 2014 Plan;

• 203,750 shares of common stock issuable upon the vesting of restricted stock units outstanding under our 2014 Plan granted after September 30, 2021; and

• 1,129,087 shares of common stock reserved for future issuance under our 2014 Plan (which does not reflect the options or restricted stock units granted under the 2014 Plan after September 30, 2021), and an additional 4,207,203 shares of common stock reserved for future issuance under this plan on January 1, 2022 pursuant to its automatic increase provisions, as well as any automatic increases in the number of shares of our common stock reserved for future issuance under this plan.

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In addition, the number of shares of our common stock to be outstanding immediately after this offering as shown above excludes the issuance and sale of 2,083,520 shares of common stock after September 30, 2021 and through the date of this prospectus supplement under our at-the-market offering program with Cantor Fitzgerald & Co. (“Cantor”) and H.C. Wainwright & Co., LLC (“Wainwright”), which we established on June 28, 2021. As of the date of this prospectus supplement, under the at-the-market offering program, we may issue and sell shares of our common stock having an aggregate offering price of up to approximately $25.0 million from time to time, in such amounts as we may determine, subject to certain limitations contained therein and under applicable securities laws.

The number of shares of common stock outstanding after this offering also excludes shares issuable upon the exercise of the Series F Warrants.

Unless otherwise indicated, all information in this prospectus supplement assumes no exercise of the underwriter’s option to purchase additional securities and no exercise or settlement, as applicable, of the outstanding warrants, options and restricted stock units described above.

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RISK FACTORS

Investing in our securities involves a high degree of risk. You should consider carefully the risks described below and discussed under the section captioned “Risk Factors” contained in our Annual Report for the year ended December 31, 2020, as updated by our subsequent filings under the Securities Exchange Act of 1934, as amended, or the Exchange Act, each of which is incorporated by reference in this prospectus in their entirety, together with other information in this prospectus, and the information and documents incorporated by reference in this prospectus, and any free writing prospectus that we have authorized for use in connection with this offering before you make a decision to invest in our securities. If any of the following events actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our securities to decline and you may lose all or part of your investment. The risks described below are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business operations.

Risks Relating to this Offering

Management will have broad discretion as to the use of proceeds from this offering and may invest or spend the proceeds in ways with which you do not agree and in ways that may not increase the value of your investment.

Our management will have broad discretion over the use of proceeds from this offering, including for any of the purposes described in the section of this prospectus entitled “Use of Proceeds.” You may not agree with our decisions, and our use of the proceeds may not yield any return on your investment. Our failure to apply the net proceeds from this offering effectively could compromise our ability to pursue our business strategy and we might not be able to yield a significant return, if any, on our investment of these net proceeds. In addition, the net proceeds from this offering may not be sufficient for our anticipated uses, and we may need additional resources to progress our product candidates to the stage we expect. You will not have the opportunity to influence our decisions on how to use our net proceeds from this offering.

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

In order 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. We cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal to or greater than the price paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. 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, including under our at-the-market offering program with Cantor and Wainwright, the issuance of these securities could result in further dilution to our stockholders or result in downward pressure on the price of our common stock. A significant portion of our total outstanding shares are eligible to be sold into the market, which could cause the market price of our common stock to drop significantly, even if our business is doing well.

Sales of a substantial number of shares of our common stock in the public market could occur at any time. These sales, or the perception in the market that the holders of a large number of shares of our common stock stockholders intend to sell shares, could cause the market price of our common stock to decline significantly.

Upon completion of this offering, based on 118,114,793 shares of our common stock outstanding as of September 30, 2021 and the issuance and sale of 2,083,520 shares of common stock after September 30, 2021 and through the date of this prospectus supplement under our at-the-market offering program with Cantor and Wainwright, we will have outstanding a total of approximately 171,448,313 shares of common stock (assuming no exercise of the underwriter’s option to purchase additional securities and no exercise of the Series F Warrants

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to purchase shares of common stock offered hereby). Other than any shares held by our directors, officers and certain existing investors, all of these are currently freely tradable, and the shares to be sold in this offering, or issuable upon exercise of the Series F Warrants, plus any shares sold upon exercise of the underwriter’s option to purchase additional securities, or issuable upon the exercise of the Series F Warrants sold upon the exercise of the underwriter’s option to purchase additional Series F Warrants, will be freely tradable, without restriction, in the public market immediately following this offering. Maxim Group LLC, however, may, in its sole discretion, permit our officers, directors and certain existing investors, who are subject to lock-up agreements to sell shares prior to the expiration of the lock-up agreements. Exceptions to the lock-up restrictions are described in more detail in this prospectus supplement under the caption “Underwriting.”

As of September 30, 2021, we had an aggregate of approximately 7,343,516 shares of common stock (i) issuable upon exercise of stock options outstanding, (ii) issuable upon the exercise of warrants, (iii) issuable upon the settlement of restricted stock units and (iv) reserved for issuance under our 2014 Plan, all of which would result in additional dilution. In addition, subsequent to September 30, 2021 and through the date of this prospectus supplement, we granted stock options to purchase an aggregate of approximately 891,500 shares of common stock under our 2014 Plan and in connection with inducement awards granted outside of our 2014 Plan and 203,750 restricted stock units under our 2014 Plan. Our 2014 Plan also provides for annual automatic increases in the number of shares of our common stock reserved for future issuance under the plan.

The trading price of our common stock has been volatile with substantial price fluctuations on heavy volume, which could result in substantial losses for purchasers of our common stock and existing stockholders.

Our stock price has been and, in the future, may be subject to substantial volatility. During the period from January 2, 2018 through February 8, 2022, for example, our stock has traded in a range with a low of $0.328 and a high of $25.70. The stock market in general and the market for biopharmaceutical companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. We do not, for example, have any explanation for the volatility in our stock price or the heavy volume of trading (on some days exceeding six times the number of shares currently outstanding) that occurred in our common stock in February and March of 2019. As a result of this volatility, investors may not be able to sell their common stock at or above the price paid for the shares. The market price for our common stock may be influenced by many factors, including:

• announcements relating to development, regulatory approvals or commercialization of our product candidates or those of competitors;

• results of clinical trials of our product candidates or those of our competitors;

• announcements by us or our competitors of significant strategic partnerships or collaborations or terminations of such arrangements;

• actual or anticipated variations in our operating results;

• changes in financial estimates by us or by any securities analysts who might cover our stock;

• conditions or trends in our industry;

• changes in laws or other regulatory actions affecting us or our industry;

• stock market price and volume fluctuations of comparable companies and, in particular, those that operate in the biopharmaceutical industry;

• announcements of investigations or regulatory scrutiny of our operations or lawsuits filed against us;

• capital commitments;

• investors’ general perception of our company and our business;

• disputes concerning our intellectual property or other proprietary rights;

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• recruitment or departure of key personnel; and

• sales of our common stock, including sales by our directors and officers or specific stockholders.

Moreover, the global stock markets have experienced, and may continue to experience, significant volatility as a result of the COVID-19 pandemic. The COVID-19 pandemic and the significant uncertainties it has caused for the global economy, business activity and business confidence have had, and may continue to have, a significant effect on the market price of securities generally, including our common stock.

In addition, in the past, stockholders have initiated class action lawsuits against pharmaceutical and biotechnology companies following periods of volatility in the market prices of these companies’ stock. We have been subject to such lawsuits. Although the lawsuits have ended, any future lawsuits to which we may become a party are subject to inherent uncertainties and will likely be expensive and time-consuming to investigate, defend and resolve, and will divert our management’s attention and financial and other resources. The outcome of litigation is necessarily uncertain, and we could be forced to expend significant resources in the defense of these and other suits, and we may not prevail. Any litigation to which we are a party may result in an onerous or unfavorable judgment that may not be reversed upon appeal or in payments of substantial monetary damages or fines, or we may decide to settle these or other lawsuits on similarly unfavorable terms, which could adversely affect our business, financial condition, results of operations or stock price.

If we are unable to maintain listing of our securities on the Nasdaq Capital Market or another reputable stock exchange, it may be more difficult for our stockholders to sell their securities.

Nasdaq requires listing issuers to comply with certain standards in order to remain listed on its exchange. If, for any reason, Nasdaq should delist our securities from trading on its exchange and we are unable to obtain listing on another reputable national securities exchange, a reduction in some or all of the following may occur, each of which could materially adversely affect our stockholders:

• the liquidity of our common stock;

• the market price of our common stock;

• our ability to obtain financing for the continuation of our operations;

• the number of institutional and general investors that will consider investing in our common stock;

• the number of market makers in our common stock;

• the availability of information concerning the trading prices and volume of our common stock; and

• the number of broker-dealers willing to execute trades in shares of our common stock.

On June 1, 2021, we received a written notice from Nasdaq indicating that we were not in compliance with the $1.00 minimum bid price requirement for continued listing on The Nasdaq Capital Market, as set forth in Listing Rule 5550(a)(2). In accordance with Listing Rule 5810(c)(3)(A), we were provided a period of 180 calendar days, or until November 29, 2021, to regain compliance with the minimum bid price requirement. On November 30, 2021, we received a written notice from Nasdaq (the “November Notice”) stating that, although we had not regained compliance with the minimum bid price requirement by November 29, 2021, in accordance with Listing Rule 5810(c)(3)(A), we were eligible for an additional 180 calendar day period, or until May 30, 2022, to regain compliance with the minimum bid price requirement. To regain compliance, the closing bid price of our common stock must meet or exceed $1.00 per share for a minimum of ten consecutive business days during this 180-day period. The November Notice has no effect on the listing or trading of our common stock at this time, and we currently to plan to seek the approval of our stockholders to implement a reverse stock split. There is no assurance that we will be able to obtain stockholder approval of the reverse stock split or regain compliance with the minimum bid price requirement or will otherwise be in compliance with other Nasdaq listing criteria.

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There is no public market for the Series F Warrants offered in this offering.

There is no established public trading market for the Series F Warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to apply for listing of the Series F Warrants on any securities exchange or recognized trading system. Without an active market, the liquidity of the Series F Warrants will be limited.

Holders of the Series F Warrants will have no rights as a common stockholder until such holders exercise their Series F Warrants and acquire our common stock.

Until holders of the Series F Warrants acquire shares of our common stock upon exercise of the Series F Warrants, holders of the Series F Warrants will have no rights with respect to the shares of our common stock underlying such Series F Warrants. Upon exercise of the Series F Warrants, the holders thereof will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

Our ability to utilize our net operating loss carryforwards and certain other tax attributes may be limited.

Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, if a corporation undergoes an “ownership change” (generally defined as a greater than 50 percentage point change (by value) in the ownership of its equity by certain significant stockholders over a rolling three-year period), the corporation’s ability to use its pre-change net operating loss carryforwards and certain other pre-change tax attributes to offset its post-change income or tax liability may be limited. We have experienced such ownership changes in the past (and derecognized certain deferred tax assets as of December 31, 2020 in connection with ownership changes we determined had occurred prior to such date), and we may experience ownership changes as a result of this offering, future offerings and/or subsequent shifts in our stock ownership, some of which may be outside our control. Because our ability to use our net operating loss carryforwards and other tax attributes is limited by ownership changes, we may be unable to utilize a material portion of our net operating losses and other tax attributes.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $14.0 million (or $16.2 million if the underwriter exercises its option to purchase additional securities in full), after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. We will only receive additional proceeds from the exercise of the Series F Warrants issuable in connection with this offering if the Series F Warrants are exercised and the holders of such Series F Warrants pay the exercise price in cash upon such exercise and do not utilize the cashless exercise provision of the Series F Warrants.

We currently expect to use the net proceeds from this offering to fund pre-commercialization activities and for general working capital and corporate purposes.

The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the amount of cash used in our operations. We therefore cannot estimate with certainty the amount of net proceeds to be used for the purposes described above. We may find it necessary or advisable to use the net proceeds from this offering for other purposes, and we will have broad discretion in the application of the net proceeds.

Pending the use of the net proceeds from this offering as described above, we may invest the net proceeds in a variety of capital preservation investments, including short- and intermediate-term, interest-bearing obligations, investment-grade instruments or U.S. government securities.

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DIVIDEND POLICY

We have never declared or paid any cash dividends on our capital stock. We currently expect to retain all available funds and future earnings, if any, to finance the growth and development of our business. We do not expect to pay any cash dividends on our common stock in the foreseeable future. Payment of future dividends, if any, will be at the discretion of our board of directors and will depend on our financial condition, results of operations, capital requirements, restrictions contained in any future financing instruments, provisions of applicable law and other factors the board of directors deems relevant.

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DESCRIPTION OF SECURITIES WE ARE OFFERING

In this offering, we are offering for sale 51,250,000 Units. Each Unit consists of one share of common stock and one Series F Warrant to purchase one share of common stock. The shares of common stock and Series F Warrants comprising the units are immediately separable and will be issued separately, but will be purchased together in this offering. We are also registering the shares of common stock issuable upon exercise of the Series F Warrants. These securities are being issued pursuant to an underwriting agreement between us and the underwriter. You should review the underwriting agreement and the form of Series F Warrant, each of which will be filed as exhibits to a Current Report on Form 8-K on or around the date of this prospectus and incorporated by reference into this prospectus, for a complete description of the terms and conditions applicable to the Series F Warrants. The following brief summary of the material terms and provisions of the Series F Warrants is subject to, and qualified in its entirety by, the form of Series F Warrant.

Units

We are offering Units, with each Unit consisting of one share of common stock and one Series F Warrant to purchase one share of common stock at an exercise price per share of $0.30, together with the share of common stock underlying each Series F Warrant, at a public offering price of $0.30 per Unit. The Units will not be certificated and the shares of common stock and Series F Warrants comprising such units are immediately separable and will be issued separately, but will be purchased together in this offering.

Common Stock

The material terms and provisions of our common stock and other outstanding securities convertible into or exercisable for shares of our common stock are described under the headings “Description of Capital Stock” in the accompanying prospectus.

Warrants

Description of Series F Warrants Included in the Units

The material terms and provisions of the Series F Warrants being offered pursuant to this prospectus are summarized below. This summary of some provisions of the Series F Warrants is not complete. For the complete terms of the Series F Warrants, you should refer to the form of Series F Warrant which will be filed as an exhibit to a Current Report on Form 8-K on or around the date of this prospectus and incorporated by reference into this prospectus.

Pursuant to a warrant agency agreement between us and Computershare, Inc. and Computershare Trust Company, N.A., as warrant agent, the warrants will be issued in book-entry form and shall initially be represented only by one or more global warrants deposited with the warrant agent, as custodian, on behalf of The Depository Trust Company (“DTC”) and registered in the name of Cede & Co., a nominee of DTC, or as otherwise directed by DTC.

Each Unit includes one Series F Warrant to purchase one share of common stock at an exercise price equal to $0.30 per share at any time for five years after the date of the closing of this offering. The Series F Warrants issued in this offering will be governed by the terms of such Series F Warrant. The holder of a Series F Warrant will not be deemed a holder of our underlying common stock until the Series F Warrant is exercised, except as set forth in the Series F Warrant.

Subject to certain limitations as described below, the Series F Warrants are immediately exercisable upon issuance on the closing date and expire on the five-year anniversary of the closing date. Pursuant to the terms of the Series F Warrants, a holder of Series F Warrants will not have the right to exercise any portion of its Series F

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Warrants if the holder (together with such holder’s affiliates, and any persons acting as a group together with such holder or any of such holder’s affiliates) would beneficially own a number of shares of common stock in excess of 4.99% (or, at the election of the purchaser prior to the date of issuance, 9.99%) (the “Beneficial Ownership Limitations”) of the shares of our common stock then outstanding after giving effect to such exercise; provided, however, that upon notice to us, the holder may increase or decrease the Beneficial Ownership Limitation, provided that in no event shall the Beneficial Ownership Limitation exceed 9.99% and any increase in the Beneficial Ownership Limitation will not be effective until 61 days following notice of such increase from the holder to us.

The exercise price and the number of shares issuable upon exercise of the Series F Warrants is subject to appropriate adjustment in the event of recapitalization events, stock dividends, stock splits, stock combinations, reclassifications, reorganizations or similar events affecting our common stock. The Series F Warrant holders must pay the exercise price in cash upon exercise of the Series F Warrants, unless such Series F Warrant holders are utilizing the cashless exercise provision of the Series F Warrants.

The Series F Warrants contain a full-ratchet anti-dilution exercise price adjustment upon the issuance of any common stock, securities convertible into common stock or certain other issuances at a price below the then-existing exercise price of the Series F Warrants, with certain exceptions. The terms of the Series F Warrants, including these anti-dilution protections, may make it difficult for us to raise additional capital at prevailing market terms in the future.

In addition, in the event we consummate a merger or consolidation with or into another person or other reorganization event in which our common shares are converted or exchanged for securities, cash or other property, or we sell, lease, license, assign, transfer, convey or otherwise dispose of all or substantially all of our assets or we or another person acquire 50% or more of our outstanding shares of common stock, then following such event, the holders of the Series F Warrants will be entitled to receive upon exercise of such Series F Warrants the same kind and amount of securities, cash or property which the holders would have received had they exercised their Series F Warrants immediately prior to such fundamental transaction. Any successor to us or surviving entity shall assume the obligations under the Series F Warrants. In addition, in the event of a fundamental transaction, the holders of the Series F Warrants have the right to require us or a successor entity to redeem the Series F Warrants for cash in the amount of the Black-Scholes value of the unexercised portion of the Series F Warrants within 30 days of the date of the consummation of the fundamental transaction as described in the Series F Warrants; provided, however, that, if the fundamental transaction is not within our control, including not approved by our board of directors, the holders of the Series F Warrants shall only be entitled to receive the same type or form of consideration (and in the same proportion), at the Black-Scholes value of the unexercised portion of the Series F Warrants, that is being offered and paid to the holders of common stock in connection with the fundamental transaction.

Upon the holder’s exercise of a Series F Warrant, we will issue the shares of common stock issuable upon exercise of the Series F Warrant within two trading days following our receipt of a notice of exercise, provided that payment of the exercise price has been made (unless exercised via the “cashless” exercise provision). Prior to the exercise of any Series F Warrants to purchase common stock, holders of the Series F Warrants will not have any of the rights of holders of the common stock purchasable upon exercise, including the right to vote, except as set forth therein.

Holders of Series F Warrants may exercise the Series F Warrants only if the issuance of the shares of our common stock upon exercise of the warrants is covered by an effective registration statement, or an exemption from registration is available under the Securities Act of 1933, as amended (the “Securities Act”), and the securities laws of the state in which the holder resides. Pursuant to the terms of the underwriting agreement, we intend to use commercially reasonable efforts to maintain an effective registration statement covering the issue and sale of the shares of our common stock issuable upon the exercise of the Series F Warrants. The holders of Series F Warrants must pay the exercise price in cash upon exercise of the Series F Warrants unless there is not

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an effective registration statement or, if required, there is not an effective state law registration or exemption covering the issuance of the shares of our common stock underlying the Series F Warrants (in which case, the Series F Warrants may only be exercised via a “cashless” exercise provision).

We do not intend to apply for listing of the Series F Warrants on any securities exchange or recognized trading system.

Voting Agreements

We expect that certain investors in this offering may agree to enter into a voting agreement whereby each such investor will agree to vote all shares of common stock they beneficially own on the closing date of this offering, including the shares purchased in the offering, with respect to any proposals presented to our stockholders at our next stockholders’ meeting. Such investors’ agreement to vote their shares of common stock in accordance with the immediately preceding sentence does not require the holder to vote its shares for or against any particular proposal or proposals, whether or not such proposal or proposals are recommended by our board of directors.

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CERTAIN MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

The following discussion is a summary of certain material U.S. federal income tax considerations relating to the purchase, ownership and disposition of the Units or components thereof issued pursuant to this offering and shares of our common stock received upon exercise of the Series F Warrants, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local or non-U.S. tax laws are not discussed. This discussion is based on the U.S. Internal Revenue Code of 1986, as amended (the “Code”), Treasury Regulations promulgated thereunder, judicial decisions, and published rulings and administrative pronouncements of the U.S. Internal Revenue Service (the “IRS”), in each case in effect as of the date hereof. These authorities may change or be subject to differing interpretations. Any such change or differing interpretation may be applied retroactively in a manner that could adversely affect a holder of Series F Warrants or shares of our common stock. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below. There can be no assurance the IRS or a court will not take a contrary position to that discussed below regarding the tax consequences of the purchase, ownership and disposition of the Units and shares of our common stock received upon the exercise of the Series F Warrants.

This discussion is limited to holders that hold Units, Series F Warrants or shares of our common stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all U.S. federal income tax consequences relevant to a holder’s particular circumstances, including the impact of the alternative minimum tax and the Medicare contribution tax on net investment income. In addition, it does not address consequences relevant to holders subject to special rules, including, without limitation:

• U.S. expatriates and former citizens or long-term residents of the United States;

• persons holding Series F Warrants or shares of our common stock as part of a hedge, straddle or other risk reduction strategy or as part of a conversion transaction or other integrated investment;

• banks, insurance companies, and other financial institutions;

• brokers, dealers or traders in securities;

• “controlled foreign corporations,” “passive foreign investment companies,” and corporations that accumulate earnings to avoid U.S. federal income tax;

• partnerships or other entities or arrangements treated as partnerships for U.S. federal income tax purposes (and investors therein);

• tax-exempt organizations or governmental organizations;

• persons deemed to sell Series F Warrants or shares of our common stock under the constructive sale provisions of the Code;

• persons subject to special tax accounting rules as a result of any item of gross income with respect to Series F Warrants or shares of our common stock being taken into account in an “applicable financial statement” (as defined in the Code);

• persons who hold or receive Series F Warrants or shares of our common stock pursuant to the exercise of any employee stock option or otherwise as compensation;

• tax-qualified retirement plans; and

• “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.

If an entity or arrangement treated as a partnership for U.S. federal income tax purposes holds Series F Warrants or shares of our common stock, the tax treatment of a partner in the partnership will depend on the status of the

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partner, the activities of the partnership and certain determinations made at the partner level. Accordingly, partnerships holding Series F Warrants or shares of our common stock and the partners in such partnerships should consult their tax advisors regarding the U.S. federal income tax consequences to them.

THIS DISCUSSION IS FOR INFORMATION PURPOSES ONLY AND IS NOT TAX ADVICE. INVESTORS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATIONS AS WELL AS ANY TAX CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF UNITS AND SHARES OF OUR COMMON STOCK RECEIVED UPON THE EXERCISE OF THE SERIES F WARRANTS ARISING UNDER THE U.S. FEDERAL ESTATE OR GIFT TAX LAWS OR UNDER THE LAWS OF ANY STATE, LOCAL OR NON-U.S. TAXING JURISDICTION OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Characterization of Units

Each Unit will be treated for U.S. federal income tax purposes as an investment unit consisting of one share of our common stock and one Series F Warrant to purchase one share of common stock. In determining their tax basis for the common stock and the Series F Warrant constituting a Unit, purchasers of Units should allocate its purchase price between such share of common stock and Series F Warrants based on their respective fair market values at the time of issuance. We do not intend to advise purchasers of the Units with respect to this determination, and purchasers of the Units are advised to consult their tax and financial advisors with respect to the relative fair market values of the common stock and the Series F Warrants for U.S. federal income tax purposes.

Tax Considerations Applicable to U.S. Holders

Definition of a U.S. Holder

For purposes of this discussion, a “U.S. holder” is any beneficial owner of Series F Warrants or shares of our common stock that, for U.S. federal income tax purposes, is:

• 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 under the laws of the United States, any state thereof, or the District of Columbia;

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

• a trust that (1) is subject to the primary supervision of a U.S. court and one or more “United States persons” (within the meaning of Section 7701(a)(30) of the Code) have the authority to control substantial decisions of the trust, or (2) has made a valid election under applicable Treasury Regulations to continue to be treated as a United States person for U.S. federal income tax purposes.

Sale or Other Disposition, Exercise or Expiration of Series F Warrants

Upon the sale or other disposition of a Series F Warrant (other than by exercise), a U.S. holder will generally recognize capital gain or loss equal to the difference between the amount realized on the sale or other disposition and the U.S. holder’s tax basis in the Series F Warrant. This capital gain or loss generally will be long-term capital gain or loss if the U.S. holder’s holding period in such Series F Warrant is more than one year at the time of the sale or other disposition. The deductibility of capital losses is subject to limitations.

In general, a U.S. holder will not be required to recognize income, gain or loss upon exercise of a Series F Warrant for its exercise price. A U.S. holder’s tax basis in a share of our common stock received upon exercise of the Series F Warrants will be equal to the sum of (1) the U.S. holder’s tax basis in the Series F Warrants exchanged therefor and (2) the exercise price of such Series F Warrants. A U.S. holder’s holding period in the

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shares of our common stock received upon exercise will commence on the day after such U.S. holder exercises the Series F Warrants. Although there is no direct legal authority as to the U.S. federal income tax treatment of an exercise of a Series F Warrant on a cashless basis, we intend to take the position that such exercise will not be taxable, either because the exercise is not a gain realization event or because it qualifies as a tax-free recapitalization. In the former case, the holding period of the shares of our common stock received upon exercise of Series F Warrants should commence on the day after the Series F Warrants are exercised. In the latter case, the holding period of the shares of our common stock received upon exercise of Series F Warrants would include the holding period of the exercised Series F Warrants. However, our position is not binding on the IRS, and the IRS may treat a cashless exercise of a Series F Warrant as a taxable exchange. U.S. holders are urged to consult their tax advisors as to the consequences of an exercise of a Series F Warrant on a cashless basis, including with respect to their holding period and tax basis in the common stock received.

If a Series F Warrant expires without being exercised, a U.S. holder will recognize a capital loss in an amount equal to such holder’s tax basis in the Series F Warrant. Such loss generally will be long-term capital loss if the U.S. holder’s holding period in such Series F Warrant is more than one year at the time of expiration. The deductibility of capital losses is subject to limitations.

Constructive Dividends on Series F Warrants

As described in the section entitled “Dividend Policy,” we do not expect to pay any cash dividends on our common stock in the foreseeable future. However, if the exercise price of the Series F Warrants is adjusted as a result of certain events affecting our common stock (or in certain circumstances, there is a failure to make adjustments), such adjustments may result in the deemed payment of a taxable dividend to a U.S. holder. U.S. holders should consult their tax advisors regarding the proper treatment of any adjustments to the exercise price of the Series F Warrants.

We are currently required to report the amount of any deemed distributions on our website or to the IRS and to holders not exempt from reporting. The IRS has proposed regulations addressing the amount and timing of deemed distributions, as well as obligations of withholding agents and filing and notice obligations of issuers in respect of such deemed distributions. If adopted as proposed, the regulations would generally provide that (i) the amount of a deemed distribution is the excess of the fair market value of the right to acquire stock immediately after the exercise price adjustment over the fair market value of the right to acquire stock (after the exercise price adjustment) without the adjustment, (ii) the deemed distribution occurs at the earlier of the date the adjustment occurs under the terms of the instrument and the date of the actual distribution of cash or property that results in the deemed distribution and (iii) we are required to report the amount of any deemed distributions on our website or to the IRS and to all holders (including holders that would otherwise be exempt from reporting). The final regulations will be effective for deemed distributions occurring on or after the date of adoption, but holders and withholding agents may rely on them prior to that date under certain circumstances.

Distributions on Common Stock

As described in the section entitled “Dividend Policy,” we do not expect to pay any cash dividends on our common stock in the foreseeable future. However, if we do make distributions of cash or property on our common stock, such distributions will constitute dividends to the extent paid out of our current or accumulated earnings and profits, as determined for U.S. federal income tax purposes. Dividends received by a corporate U.S. holder may be eligible for a dividends received deduction, subject to applicable limitations. Dividends received by certain non-corporate U.S. holders, including individuals, are generally taxed at the lower applicable capital gains rate provided certain holding period and other requirements are satisfied. Distributions in excess of our current and accumulated earnings and profits will constitute a return of capital and first be applied against and reduce a U.S. holder’s adjusted tax basis in its common stock, as the case may be, but not below zero. Any excess will be treated as capital gain and will be treated as described below in the section relating to the sale or disposition of our common stock, as applicable.

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Sale, Exchange or Other Disposition of Common Stock

Upon a sale, exchange, or other disposition of our common stock, a U.S. holder generally will recognize capital gain or loss equal to the difference between the amount realized (not including any amount attributable to declared and unpaid dividends, which will be taxable as described above to U.S. holders of record who have not previously included such dividends in income) and the U.S. holder’s adjusted tax basis in our common stock. A U.S. holder’s adjusted tax basis in our common stock generally will equal (i) its cost for the common stock (in the case of common stock acquired in this offering) or (ii) the sum of (A) its tax basis in a Series F Warrant and (B) the exercise price of the Series F Warrant (in the case of common stock acquired upon exercise of a Series F Warrant and as discussed above under “—Sale or Other Disposition, Exercise or Expiration of Series F Warrants”), reduced by the amount of any cash distributions treated as a return of capital as described above. Such capital gain or loss generally will be long-term capital gain or loss if the U.S. holder’s holding period for our common stock is more than one year at the time of disposition. Long-term capital gains recognized by certain non-corporate U.S. Holders, including individuals, generally are subject to reduced rates of taxation. The deductibility of capital losses is subject to limitations.

Information Reporting and Backup Withholding

A U.S. holder may be subject to information reporting and backup withholding when such holder receives payments (including constructive dividends) or receives proceeds from the sale or other taxable disposition of shares of our common stock of Series F Warrants. Certain U.S. holders are exempt from backup withholding, including corporations and certain tax-exempt organizations. A U.S. holder will be subject to backup withholding if such holder is not otherwise exempt and such holder:

• fails to furnish the holder’s taxpayer identification number, which for an individual is ordinarily his or her social security number;

• furnishes an incorrect taxpayer identification number;

• is notified by the IRS that the holder previously failed to properly report payments of interest or dividends; or

• fails to certify under penalties of perjury that the holder has furnished a correct taxpayer identification number and that the IRS has not notified the holder that the holder is subject to backup withholding.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a U.S. holder’s U.S. federal income tax liability, provided the required information is timely furnished to the IRS. U.S. holders should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption.

Tax Considerations Applicable to Non-U.S. Holders

For purposes of this discussion, a “non-U.S. holder” is a beneficial owner of Series F Warrants or shares of our common stock that is neither a U.S. holder nor an entity treated as a partnership for U.S. federal income tax purposes.

Exercise of Series F Warrants

A non-U.S. holder generally will not be subject to U.S. federal income tax on the exercise of Series F Warrants into shares of our common stock. However, if a cashless exercise of the Series F Warrants results in a taxable exchange, as described in “— Tax Considerations Applicable to U.S. holders — Sale or Other Disposition, Exercise or Expiration of Series F Warrants,” the rules described below under “Sale or Other Disposition of Common Stock or Series F Warrants” would apply.

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Constructive Dividends on Series F Warrants

As described in the section entitled “Dividend Policy,” we do not expect to pay any cash dividends on our common stock in the foreseeable future. However, if the exercise price of a Series F Warrant is adjusted as a result of certain events affecting our common stock (or in certain circumstances, there is a failure to make adjustments), such adjustments may result in the deemed payment of a taxable dividend to a non-U.S. holder. Any resulting withholding tax attributable to deemed dividends may be collected from other amounts payable or distributable to, or other assets of, the non-U.S. holder. See the section above entitled “—Tax Considerations Applicable to U.S. Holders—Constructive Dividends on Series F Warrants.” Non-U.S. holders should consult their tax advisors regarding the proper treatment of any adjustments to the exercise price of the Series F Warrants.

Distributions on Common Stock

As described in the section entitled “Dividend Policy,” we do not expect to pay any cash dividends on our common stock in the foreseeable future. However, if we do make distributions of cash or property on our common stock, such distributions will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts not treated as dividends for U.S. federal income tax purposes will constitute a return of capital and first be applied against and reduce a non-U.S. holder’s adjusted tax basis in its common stock, as the case may be, but not below zero. Any excess will be treated as capital gain and will be treated as described below in the section relating to the sale or disposition of our common stock. Because we may not know the extent to which a distribution is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of the withholding rules discussed below we or the applicable withholding agent may treat the entire distribution as a dividend.

Dividends paid to a non-U.S. holder of our common stock that are not effectively connected with the non-U.S. holder’s conduct of a trade or business within the United States will be subject to U.S. federal withholding tax at a rate of 30% of the gross amount of the dividends (or such lower rate specified by an applicable income tax treaty).

Non-U.S. holders will be entitled to a reduction in or an exemption from withholding on dividends as a result of either (a) an applicable income tax treaty or (b) the non-U.S. holder holding our common stock in connection with the conduct of a trade or business within the United States and dividends being effectively connected with that trade or business. To claim such a reduction in or exemption from withholding, the non-U.S. holder must provide the applicable withholding agent with a properly executed (a) IRS Form W-8BEN or W-8BEN-E (or other applicable documentation) claiming an exemption from or reduction of the withholding tax under the benefit of an income tax treaty between the United States and the country in which the non-U.S. holder resides or is established or (b) IRS Form W-8ECI stating that the dividends are not subject to withholding tax because they are effectively connected with the conduct by the non-U.S. holder of a trade or business within the United States. These certifications must be provided to the applicable withholding agent prior to the payment of dividends and must be updated periodically. Non-U.S. holders that do not timely provide the applicable withholding agent with the required certification, but that qualify for a reduced rate under an applicable income tax treaty, may obtain a refund of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS. Non-U.S. holders should consult their tax advisors regarding their entitlement to benefits under any applicable tax treaties.

If dividends paid to a non-U.S. holder 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, the non-U.S. holder maintains a permanent establishment in the United States to which such dividends are attributable), then, although exempt from U.S. federal withholding tax (provided the non-U.S. holder provides appropriate certification, as described above), the non-U.S. holder will be subject to U.S. federal income tax on such dividends on a net income basis at the regular graduated rates. In addition, a non-U.S. holder that is a corporation

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may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on its effectively connected earnings and profits for the taxable year that are attributable to such dividends, as adjusted for certain items. Non-U.S. holders should consult their tax advisors regarding their entitlement to benefits under any applicable income tax treaty.

Sale or Other Disposition of Common Stock or Series F Warrants

A non-U.S. holder will not be subject to U.S. federal income tax on any gain realized upon the sale, redemption or other taxable disposition of our Series F Warrants or our common stock unless:

• the gain is 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, the non-U.S. holder maintains a permanent establishment in the United States to which such gain is attributable);

• the non-U.S. holder is a nonresident alien individual present in the United States for 183 days or more during the taxable year of the disposition and certain other requirements are met; or

• our Series F Warrants or our common stock constitute a U.S. real property interest (“USRPI”) by reason of our status as a U.S. real property holding corporation (“USRPHC”) for U.S. federal income tax purposes.

Gain described in the first bullet point above generally will be subject to U.S. federal income tax on a net income basis at the regular graduated rates. A Non-U.S. holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on such effectively connected gain, as adjusted for certain items.

A non-U.S. holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on any gain derived from the disposition, which may be offset by certain U.S.-source capital losses of the non-U.S. holder (even though the individual is not considered a resident of the United States), provided the non-U.S. holder has timely filed U.S. federal income tax returns with respect to such losses.

With respect to the third bullet point above, we believe we are not currently and do not anticipate becoming a USRPHC. Because the determination of whether we are a USRPHC depends on the fair market value of our USRPIs relative to the fair market value of our other business assets and our non- U.S. real property interests, however, there can be no assurance we are not a USRPHC or will not become one in the future.

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

Information Reporting and Backup Withholding

A non-U.S. holder will not be subject to backup withholding with respect to distributions on our common stock we make to the non-U.S. holder (including constructive dividends with respect to the Series F Warrants) provided the applicable withholding agent does not have actual knowledge or reason to know such holder is a United States person and the holder certifies its non-U.S. status, such as by providing a valid IRS Form W-8BEN, W-8BEN-E or W-8ECI, or other applicable certification. However, information returns generally will be filed with the IRS in connection with any distributions (including deemed distributions) made on our common stock and Series F Warrants to the non-U.S. holder, regardless of whether any tax was actually withheld.

Information reporting and backup withholding may apply to the proceeds of a sale or other taxable disposition of our common stock or Series F Warrants within the United States, and information reporting may (although backup withholding generally will not) apply to the proceeds of a sale or other taxable disposition of our

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common stock or Series F Warrants outside the United States conducted through certain U.S.- related financial intermediaries, in each case, unless the beneficial owner certifies under penalty of perjury that it is a non-U.S. holder on IRS Form W-8BEN or W-8BEN-E, or other applicable form (and the payor does not have actual knowledge or reason to know that the beneficial owner is a U.S. person) or such owner otherwise establishes an exemption. Proceeds of a disposition of our common stock or Series F Warrants conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

Copies of information returns that are filed with the IRS may also be made available under the provisions of an applicable treaty or agreement to the tax authorities of the country in which the non-U.S. holder resides or is established.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a non-U.S. holder’s U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Additional Withholding Tax on Payments Made to Foreign Accounts

Withholding taxes may be imposed under Sections 1471 to 1474 of the Code (such Sections commonly referred to as the Foreign Account Tax Compliance Act (“FATCA”)) on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends (including deemed dividends) on, or (subject to the proposed Treasury Regulations discussed below) gross proceeds from the sale or other disposition of, Series F Warrants or our common stock paid to, a “foreign financial institution” or a “non-financial foreign entity” (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any “substantial United States owners” (as defined in the Code) or furnishes identifying information regarding each substantial United States owner, or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by certain “specified United States persons” or “United States owned foreign entities” (each as defined in the Code), annually report certain information about such accounts, and withhold 30% on certain payments to non-compliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

Under the applicable Treasury Regulations and administrative guidance, withholding under FATCA generally applies to payments of dividends (including deemed dividends). While withholding under FATCA would have applied also to payments of gross proceeds from the sale or other disposition of our common stock or Series F Warrants on or after January 1, 2019, proposed Treasury Regulations eliminate FATCA withholding on payments of gross proceeds entirely. Taxpayers generally may rely on these proposed Treasury Regulations until final Treasury Regulations are issued. Because we may not know the extent to which a distribution is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of these withholding rules we or the applicable withholding agent may treat the entire distribution as a dividend. Prospective investors should consult their tax advisors regarding the potential application of these withholding provisions.

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UNDERWRITING

Subject to the terms and conditions set forth in the underwriting agreement, dated February 8, 2022, between us and Maxim Group LLC (“Maxim”), we have agreed to sell to Maxim, and Maxim has agreed to purchase from us, 51,250,000 shares of our common stock and 51,250,000 Series F Warrants to purchase shares of our common stock, at the public offering price less the underwriting discount and commissions set forth on the cover page of this prospectus supplement.

The underwriting agreement provides that the obligations of Maxim are subject to certain conditions precedent such as the receipt by Maxim of officers’ certificates and legal opinions and approval of certain legal matters by its counsel. The underwriting agreement provides that Maxim will purchase all of the shares of common stock and Series F Warrants if any of them are purchased. If Maxim defaults, the underwriting agreement provides that the underwriting agreement may be terminated. We have agreed to indemnify Maxim and certain of its controlling persons against certain liabilities, including liabilities under the Securities Act, and to contribute to payments that Maxim may be required to make in respect of those liabilities.

Maxim has advised us that, following the completion of this offering, it currently intends to make a market in the common stock as permitted by applicable laws and regulations. However, Maxim is not obligated to do so, and Maxim may discontinue any market-making activities at any time without notice in its sole discretion. Accordingly, no assurance can be given as to the liquidity of the trading market for the common stock or shares of common stock underlying the Series F Warrants, that you will be able to sell any of the common stock or shares of common stock underlying the Series F Warrants held by you at a particular time or that the prices that you receive when you sell will be favorable.

Maxim is offering the shares of common stock and Series F Warrants subject to its acceptance of the shares of common stock and Series F Warrants from us and subject to prior sale. Maxim reserves the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Option to Purchase Additional Shares

We have granted to the underwriter an option, exercisable 30 days from the date of this prospectus supplement, to purchase, from time to time, in whole or in part, up to an aggregate of 7,687,500 shares and/or 7,687,500 Series F Warrants from us at the price set forth on the cover page of this prospectus supplement for Units, and at the prices of $0.29 per share and $0.01 per warrant for shares and Series F Warrants purchased separately, respectively.

Commission and Expenses

The underwriter has advised us that it proposes to offer the shares of common stock and accompanying warrants to the public at the initial public offering price set forth on the cover page of this prospectus supplement and to certain dealers, at that price less a concession not in excess of $0.00975 per share of common stock and accompanying warrant. After the offering, the initial public offering price and concession to dealers may be reduced by the underwriter. No such reduction will change the amount of proceeds to be received by us as set forth on the cover page of this prospectus.

The following table shows the public offering price, the underwriting discounts and commissions that we are to pay the underwriter and the proceeds, before expenses, to us in connection with this offering.

	Per Unit		Total
Public offering price	$	0.30	$	15,375,000
Underwriting discounts and commissions	$	0.0165	$	845,625
Proceeds before expenses, to us	$	0.2835	$	14,529,375

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We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $450,000. Included in this amount is $150,000 for the fees and expenses of the counsel to Maxim in connection with the offering. In accordance with FINRA Rule 5110, Maxim’s reimbursed fees and expenses are deemed underwriting compensation for this offering.

Listing

Our common stock is listed on The Nasdaq Capital Market under the trading symbol “ZSAN.”

Stamp Taxes

If you purchase shares of common stock or Series F Warrants offered in this prospectus supplement, you may be required to pay stamp taxes and other charges under the laws and practices of the country of purchase, in addition to the offering price listed on the cover page of this prospectus supplement.

No Sales of Similar Securities

We, our officers and our directors have agreed, subject to certain specified exceptions, not to directly or indirectly, for 120 days (in our case) and 90 days (in the case of our directors and officers) after the date of the underwriting agreement:

• sell, offer, contract or grant any option to sell (including any short sale), pledge, transfer, establish an open “put equivalent position” within the meaning of Rule 16a-l(h) under the Exchange Act, or otherwise dispose of, any shares of common stock, options or warrants to acquire shares of common stock, or securities exchangeable or exercisable for or convertible into shares of common stock currently or hereafter owned either of record or beneficially,

• enter into any swap, hedge or other agreement or transaction that transfers, in whole or in part, the economic consequence of ownership of common stock, or securities exchangeable or exercisable for or convertible into shares of common stock, or

• publicly announce an intention to do any of the foregoing for the same period without the prior written consent of Maxim.

In addition, we and each such person agrees that, without the prior written consent of Maxim, we or such other person will not, during the restricted period, make any demand for, or exercise any right with respect to, the registration of any shares of common stock or any security convertible into or exercisable or exchangeable for common stock.

The restrictions in the immediately preceding paragraph do not apply in certain circumstances, including: (a) transfers as a bona fide gift or gifts; (b) transfers to any trust for the direct or indirect benefit of such person or the immediate family or such purposes; (c) transfers pursuant to a qualified domestic order or in connection with a divorce settlement; (d) transfers by will or intestate succession to the legal representative, heir, beneficiary or immediate family of such person upon the death of such person; (e) transfers to such person’s direct or indirect affiliates, limited partners, limited liability company members or stockholders, or, if such person is a trust, to the beneficiaries of such trust; (f) transfers to the Company as forfeitures to satisfy tax withholding obligations of such person in connection with the vesting or exercise of equity awards pursuant to the Company’s equity incentive plan; (g) transfers to cash exercise an option to purchase shares of common stock granted under any equity incentive plan or stock purchase plan of the Company; (h) transfers to establish a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of common stock, provided no sales take place under such plans during the lock-up period; or (i) sales to cover tax withholding obligations upon the vesting of restricted stock units granted under Company equity incentive or stock purchase plans.

Maxim may, in its sole discretion and at any time or from time to time before the termination of the lock-up period, release all or any portion of the securities subject to lock-up agreements. There are no existing agreements between Maxim and any of our stockholders who will execute a lock-up agreement, providing consent to the sale of shares prior to the expiration of the lock-up period.

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Stabilization

Maxim has advised us that they, pursuant to Regulation M under the Exchange Act, may engage in short sale transactions, stabilizing transactions or the imposition of penalty bids in connection with this offering. These activities may have the effect of stabilizing or maintaining the market price of our common stock at a level above that which might otherwise prevail in the open market. Establishing short sales positions may involve either “covered” short sales or “naked” short sales.

“Covered” short sales are sales made in an amount not greater than the underwriter’s option to purchase additional shares of our common stock in this offering. The underwriter may close out any covered short position by either exercising their option to purchase additional shares of our common stock or purchasing shares of our common stock in the open market. In determining the source of shares to close out the covered short position, the underwriter will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which it may purchase shares through the option to purchase additional shares.

“Naked” short sales are sales in excess of the option to purchase additional shares of our common stock. The underwriter must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriter is concerned that there may be downward pressure on the price of the shares of our common stock in the open market after pricing that could adversely affect investors who purchase in this offering.

Maxim may close out any short position by purchasing shares of our common stock in the open market.

A stabilizing bid is a bid for the purchase of shares of common stock on behalf of the underwriter for the purpose of fixing or maintaining the price of the common stock. As a result, the price of our common stock may be higher than the price that might otherwise exist in the open market.

Neither we nor Maxim make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our common stock. Maxim is not obligated to engage in these activities and, if commenced, any of the activities may be discontinued at any time.

Passive Market Making

The underwriter may also engage in passive market making transactions in our common stock on the Nasdaq Capital Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of shares of our common stock in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker’s bid, that bid must then be lowered when specified purchase limits are exceeded. Passive market making may cause the price of our common stock to be higher than the price that otherwise would exist in the open market in the absence of those transactions. The underwriter is not required to engage in passive market making and, if commenced, may end passive market making activities at any time.

Electronic Distribution

A prospectus in electronic format may be made available by e-mail, on the web sites or through online services maintained by Maxim or its affiliates. In those cases, prospective investors may view offering terms online and may be allowed to place orders online. Maxim may agree with us to allocate a specific number of shares of securities for sale to online brokerage account holders. Any such allocation for online distributions will be made by Maxim on the same basis as other allocations. Other than the prospectus in electronic format, the information on the Maxim’s web site and any information contained in any other web site maintained by Maxim is not part of this prospectus, has not been approved and/or endorsed by us or Maxim and should not be relied upon by investors.

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Other Activities and Relationships

Maxim and certain of its respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Maxim and certain of its respective affiliates have, from time to time, performed, and may in the future perform, various commercial and investment banking and financial advisory services for us and our affiliates, for which Maxim received or will receive customary fees and expenses.

In the ordinary course of their various business activities, Maxim and certain of its respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments issued by us and our affiliates. If Maxim or its respective affiliates have a lending relationship with us, they routinely hedge their credit exposure to us consistent with their customary risk management policies. Maxim and its respective affiliates may hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities or the securities of our affiliates, including potentially the securities offered hereby. Any such short positions could adversely affect future trading prices of the common stock offered hereby. Maxim and certain of 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 securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Notice to Investors

Canada

The securities may be sold in Canada only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31 103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33 105 Underwriting Conflicts (NI 33 105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriters conflicts of interest in connection with this offering.

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LEGAL MATTERS

The validity of the securities offered hereby will be passed upon for us by Latham & Watkins LLP. Covington & Burling LLP, New York, New York is acting as counsel to the underwriter in connection with this offering.

EXPERTS

Our financial statements, incorporated by reference in this prospectus supplement, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report. Such financial statements are incorporated by reference in reliance upon the report of such firm given their authority as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

We have filed with the SEC a registration statement on Form S-3 under the Securities Act, of which this prospectus supplement and the accompanying base prospectus form a part. The rules and regulations of the SEC allow us to omit from this prospectus supplement and the accompanying base prospectus certain information included in the registration statement. For further information about us and the securities we are offering under this prospectus supplement and the accompanying base prospectus, you should refer to the registration statement and the exhibits and schedules filed with the registration statement. With respect to the statements contained in this prospectus supplement and the accompanying base prospectus regarding the contents of any agreement or any other document, in each instance, the statement is qualified in all respects by the complete text of the agreement or document, a copy of which has been filed as an exhibit to the registration statement.

We file reports, proxy statements and other information with the SEC under the Securities Exchange Act of 1934, as amended. The SEC maintains an Internet website that contains reports, proxy statements and other information about issuers, like us, that file electronically with the SEC. The address of that website is www.sec.gov.

The SEC allows us to “incorporate by reference” the information we file with them which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus supplement and the accompanying base prospectus. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying base prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future information filed (rather than furnished) with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act between the date of this prospectus supplement and the termination of this offering, provided, however, that we are not incorporating any information furnished under Item 2.02 or Item 7.01 of any current report on Form 8-K:

• our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021;

• our Definitive Proxy Statement on Schedule 14A (other than information furnished rather than filed), filed with the SEC on April 28, 2021, as supplemented by the supplements to the proxy statement filed with the SEC on May  25, 2021 and June 21, 2021;

• our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2021, June 30, 2021 and September 30, 2021, filed with the SEC on May  12, 2021, August  10, 2021 and November 10, 2021, respectively;

• our Current Reports on Form 8-K filed with the SEC on January  4, 2021, January  6, 2021, February  1, 2021, February  22, 2021, March  4, 2021, March  11, 2021 (at 16:22:05), April  13, 2021, April  26, 2021, May  25, 2021, June  1, 2021, June  21, 2021, June  28, 2021, July  2, 2021, October  4, 2021, October  6, 2021, October  29, 2021, November  17, 2021, November  30, 2021, December  13, 2021, January  5, 2022, January  24, 2022 and January 31, 2022; and

• the description of our common stock contained in our Registration Statement on Form 8-A, filed with the SEC on July 25, 2014 (File No.  001-36570) (as updated by the description of our common stock contained in Exhibit 4.2 to our Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 13, 2020), including any amendments or reports filed for the purpose of updating such description.

These documents may also be accessed on our website at www.zosanopharma.com. Except as otherwise specifically incorporated by reference in this prospectus supplement and the accompanying base prospectus, information contained in, or accessible through, our website is not a part of this prospectus supplement and the accompanying base prospectus.

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We will furnish without charge to you, upon written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents by writing or telephoning us at the following address:

Zosano Pharma Corporation

34790 Ardentech Court

Fremont, CA 94555

(510) 745-1200

Attention: Chief Financial Officer

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PROSPECTUS

Zosano Pharma Corporation

$150,000,000

Common Stock

Preferred Stock

Debt Securities

Warrants

Units

We may offer and sell up to $150,000,000 in the aggregate of the securities identified above from time to time in one or more offerings. This prospectus provides you with a general description of the securities.

Each time we offer and sell securities, we will provide a supplement to this prospectus that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGE 5 OF THIS PROSPECTUS AND ANY SIMILAR SECTION CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our common stock is listed on the Nasdaq Capital Market under the symbol “ZSAN.” On July 1, 2021, the closing price of our common stock on the Nasdaq Capital Market was $0.9306 per share.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is July 14, 2021.

TABLE OF CONTENTS

	Page
About This Prospectus		1
Where You Can Find More Information; Incorporation by Reference		2
The Company		4
Risk Factors		5
Use of Proceeds		6
Description of Capital Stock		7
Description of Debt Securities		9
Description of Warrants		17
Description of Units		19
Global Securities		20
Plan of Distribution		24
Legal Matters		26
Experts		26

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission (the “SEC”), using a “shelf” registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings up to a total dollar amount of $150,000,000 of securities as described in this prospectus. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific 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 or free writing prospectus may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement or free writing prospectus, you should rely on the prospectus supplement or free writing prospectus, as applicable. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement (and any applicable free writing prospectuses), together with the additional information described under the heading “Where You Can Find More Information; Incorporation by Reference.”

We have not authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus, any applicable prospectus supplement or any free writing prospectuses prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate only as of the date on its respective cover, that the information appearing in any applicable free writing prospectus is accurate only as of the date of that free writing prospectus, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates. This prospectus incorporates by reference, and any prospectus supplement or free writing prospectus may contain and incorporate by reference, market data and industry statistics and forecasts that are based on independent industry publications and other publicly available information. Although we believe these sources are reliable, we do not guarantee the accuracy or completeness of this information and we have not independently verified this information. In addition, the market and industry data and forecasts that may be included or incorporated by reference in this prospectus, any prospectus supplement or any applicable free writing prospectus may involve estimates, assumptions and other risks and uncertainties and are subject to change based on various factors, including those discussed under the heading “Risk Factors” contained in this prospectus, the applicable prospectus supplement and any applicable free writing prospectus, and under similar headings in other documents that are incorporated by reference into this prospectus. Accordingly, investors should not place undue reliance on this information.

When we refer to “we,” “our,” “us” and the “Company” in this prospectus, we mean Zosano Pharma Corporation, unless otherwise specified. When we refer to “you,” we mean the potential holders of the applicable series of securities.

This prospectus contains references to our trademarks and to trademarks belonging to other entities, which are protected under applicable intellectual property laws. Solely for convenience, trademarks and trade names referred to in this prospectus, including logos, artwork and other visual displays, may appear without the ^® or ™ symbols, but such references are not intended to indicate that we or their respective owners will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to these trademarks and trade names. We do not intend our use or display of other companies’ trade names or trademarks to imply a relationship with, or endorsement or sponsorship of us by, any such companies.

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WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

We file annual, quarterly and other reports, proxy statements and other information with the SEC. The SEC maintains a website that contains reports, proxy and information statements and other information about issuers, such as us, who file electronically with the SEC. The address of that website is http://www.sec.gov.

Our website address is www.zosanopharma.com. The information on our website, however, is not, and should not be deemed to be, a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement or documents incorporated by reference in the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may obtain a copy of the registration statement through the SEC’s website, as provided above.

Incorporation by Reference

The SEC’s rules allow us to “incorporate by reference” information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in this prospectus or a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or a subsequently filed document incorporated by reference modifies or replaces that statement.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below that have previously been filed with the SEC (but excluding any information in such documents that has been furnished to, rather than filed with, the SEC):

• our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021;

• our Definitive Proxy Statement on Schedule 14A (other than information furnished rather than filed), filed with the SEC on April  28, 2021, as supplemented by the supplements to the proxy statement filed with the SEC on May  25, 2021 and June 21, 2021;

• our Quarterly Report on Form 10-Q for the quarter ended March  31, 2021, filed with the SEC on May 12, 2021;

• our Current Reports on Form 8-K filed with the SEC on January 4, 2021, January  6, 2021, February  1, 2021, February  22, 2021, March  4, 2021, March  11, 2021 (at 16:22:05), April  13, 2021, April  26, 2021, May  25, 2021, June  1, 2021, June  21, 2021 and June 28, 2021; and

• the description of our common stock contained in our registration statement on Form 8-A, filed with the SEC on July 25, 2014 (File No. 001-36570) (as updated by the description of our common stock contained in Exhibit  4.2 to our Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 13, 2020), including any amendments or reports filed for the purpose of updating such description.

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All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), prior to the termination of this offering, including all such documents we may file with the SEC after the date of the initial registration statement and prior to the effectiveness of the registration statement, but excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus and deemed to be part of this prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus by writing or telephoning us at the following address:

Zosano Pharma Corporation

34790 Ardentech Court

Fremont, CA 94555

(510) 745-1200

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus or any accompanying prospectus supplement.

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THE COMPANY

We are a clinical-stage biopharmaceutical company focused on providing rapid systemic administration of therapeutics and other bioactive molecules to patients using our proprietary transdermal microneedle system.

We were incorporated under the laws of the State of Delaware as ZP Holdings, Inc. in January 2012, and changed our name to Zosano Pharma Corporation in June 2014. Our business was spun out of ALZA Corporation, a subsidiary of Johnson & Johnson, in October 2006. We were originally incorporated under the name The Macroflux Corporation, and changed our name to Zosano Pharma, Inc. in 2007 following the spin-off from Johnson & Johnson. In April 2012, in a transaction to recapitalize the business, a wholly-owned subsidiary of ZP Holdings was merged with and into Zosano Pharma, Inc., whereby Zosano Pharma, Inc. was the surviving entity and became a wholly-owned subsidiary of ZP Holdings. In June 2014, Zosano Pharma, Inc. changed its name to ZP Opco, Inc. ZP Group LLC, a former subsidiary that was originally formed as a joint venture with Asahi Kasei Pharmaceuticals USA (Asahi), ceased operations in December 2013 and was dissolved on December 30, 2016. On November 1, 2017, ZP Opco, Inc. merged with and into Zosano Pharma Corporation, with Zosano Pharma Corporation as the surviving corporation of the merger.

Our principal executive offices are located at 34790 Ardentech Court, Fremont, California 94555. Our telephone number is (510) 745-1200. Our website address is www.zosanopharma.com. The information contained on our website is not incorporated by reference into this prospectus. We have included our website address as an inactive textual reference only.

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RISK FACTORS

Investment in any securities offered pursuant to this prospectus and the applicable prospectus supplement involves risks. You should carefully consider the risk factors incorporated by reference to our most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q, and any subsequent Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus, and all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in the applicable prospectus supplement and any applicable free writing prospectus before acquiring any of such securities. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.

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USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

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DESCRIPTION OF CAPITAL STOCK

The following is a summary of all material characteristics of our capital stock as set forth in our amended and restated certificate of incorporation and our amended and restated bylaws. The summary does not purport to be complete and is qualified in its entirety by reference to our amended and restated certificate of incorporation and amended and restated bylaws, each of which are incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and the applicable provisions of Delaware law.

General

Our authorized capital stock consists of 250,000,000 shares of common stock, par value $0.0001 per share, and 5,000,000 shares of preferred stock, par value $0.0001 per share, all of which shares of preferred stock are undesignated.

Common Stock

Voting rights. Holders of our common stock are entitled to one vote per share held of record on all matters to be voted upon by our stockholders. The election of directors by our stockholders is determined by a plurality of the votes of the shares present in person, by remote communication, if applicable, or represented by proxy at the meeting and entitled to vote generally on the election of directors. Other matters subject to a vote by our stockholders are decided by the affirmative vote of the majority of shares present in person, by remote communication, if applicable, or represented by proxy at the meeting and entitled to vote generally on such matter. Our common stock does not have cumulative voting rights.

Dividend rights. Subject to preferences that may be applicable to the holders of any outstanding shares of our preferred stock, the holders of our common stock are entitled to receive such lawful dividends as may be declared by our Board of Directors.

Liquidation and dissolution. In the event of our liquidation, dissolution or winding up, and subject to the rights of the holders of any outstanding shares of our preferred stock, the holders of shares of our common stock will be entitled to receive pro rata all of our remaining assets available for distribution to our stockholders.

Other rights and restrictions. Our amended and restated certificate of incorporation does not permit us to redeem shares of our common stock at our election, provide for a sinking fund with respect to our common stock or provide for the granting of preemptive rights to any stockholder. All outstanding shares are fully paid and nonassessable.

Preferred Stock

Pursuant to our amended and restated certificate of incorporation, our Board of Directors is authorized, without stockholder approval, from time to time to issue up to 5,000,000 shares of preferred stock in one or more series, each of the series to have such rights and preferences, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, as the Board of Directors may determine. The rights of the holders of common stock will be subject to, and may be adversely affected by, the rights of holders of any preferred stock that we may issue in the future. The issuance of preferred stock, while providing desirable flexibility in connection with possible acquisitions and other corporate purposes, could have the effect of making it more difficult for others to acquire, or of discouraging others from attempting to acquire, a majority of our outstanding voting stock. We have no current plans to issue any shares of preferred stock.

Anti-Takeover Effects of Provisions of Delaware Law and Our Charter and By-laws

Provisions of Delaware law and our amended and restated certificate of incorporation and amended and restated bylaws could make it more difficult to acquire us by means of a tender offer, a proxy contest, open

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market purchases, removal of incumbent directors and otherwise. These provisions, summarized below, are expected to discourage types of coercive takeover practices and inadequate takeover bids and to encourage persons seeking to acquire control of us to first negotiate with us. 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 takeover or acquisition proposals because negotiation of these proposals could result in an improvement of their terms.

We must comply with Section 203 of the Delaware General Corporation Law, an anti-takeover law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years following the date the person became an interested stockholder, unless the business combination or the transaction in which the person became an interested stockholder is approved in a prescribed manner. Generally, a “business combination” includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to an interested stockholder. An “interested stockholder” includes a person who, together with affiliates and associates, owns, or did own within three years before the determination of interested stockholder status, 15% or more of the corporation’s voting stock. The existence of this provision generally will have an anti-takeover effect for transactions not approved in advance by the Board of Directors, including discouraging attempts that might result in a premium over the market price for the shares of common stock held by stockholders.

Our amended and restated certificate of incorporation and our amended and restated bylaws require that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of the stockholders and may not be effected by a consent in writing. In addition, special meetings of our stockholders may be called only by the Board of Directors and some of our officers. Our amended and restated bylaws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of stockholders, including proposed nominations of candidates for election to our Board of Directors. Our amended and restated certificate of incorporation and amended and restated bylaws also provide for our Board of Directors to be divided into three classes, with each class serving staggered three-year terms. These provisions may have the effect of deterring hostile takeovers or delaying changes in our control or management.

Listing on the Nasdaq Capital Market

Our common stock is listed on the Nasdaq Capital Market under the symbol “ZSAN.”

Authorized but Unissued Shares

The authorized but unissued shares of common stock and preferred stock are available for future issuance without stockholder approval, subject to any limitations imposed by the Nasdaq Listing Rules. These additional shares may be used for a variety of corporate finance transactions, acquisitions and employee benefit plans. The existence of authorized but unissued and unreserved common stock and preferred stock could make it more difficult or discourage an attempt to obtain control of us by means of a proxy contest, tender offer, merger or otherwise.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

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DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement or free writing prospectus, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and a third party to be identified therein, as trustee. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement and you should read the indenture for provisions that may be important to you. In the summary below, we have included references to the section numbers of the indenture so that you can easily locate these provisions. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors and set forth or determined in the manner provided in a resolution of our board of directors, in an officer’s certificate or by a supplemental indenture. (Section 2.2) The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. (Section 2.1) We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities, if applicable:

• the title and ranking of the debt securities (including the terms of any subordination provisions);

• the price or prices (expressed as a percentage of the principal amount) at which we will sell the debt securities;

• any limit on the aggregate principal amount of the debt securities;

• the date or dates on which the principal of the securities of the series is payable;

• the rate or rates (which may be fixed or variable) per annum or the method used to determine the rate or rates (including any commodity, commodity index, stock exchange index or financial index) at which the debt securities will bear interest, the date or dates from which interest will accrue, the date or dates on which interest will commence and be payable and any regular record date for the interest payable on any interest payment date;

• the place or places where principal of, and interest, if any, on the debt securities will be payable (and the method of such payment), where the securities of such series may be surrendered for registration of transfer or exchange, and where notices and demands to us in respect of the debt securities may be delivered;

• the period or periods within which, the price or prices at which and the terms and conditions upon which we may redeem the debt securities;

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• any obligation we have to redeem or purchase the debt securities pursuant to any sinking fund or analogous provisions or at the option of a holder of debt securities and the period or periods within which, the price or prices at which and in the terms and conditions upon which securities of the series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;

• the dates on which and the price or prices at which we will repurchase debt securities at the option of the holders of debt securities and other detailed terms and provisions of these repurchase obligations;

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

• whether the debt securities will be issued in the form of certificated debt securities or global debt securities;

• the portion of principal amount of the debt securities payable upon declaration of acceleration of the maturity date, if other than the principal amount;

• the currency of denomination of the debt securities, which may be United States Dollars or any foreign currency, and if such currency of denomination is a composite currency, the agency or organization, if any, responsible for overseeing such composite currency;

• the designation of the currency, currencies or currency units in which payment of principal of, premium and interest on the debt securities will be made;

• if payments of principal of, premium or interest on the debt securities will be made in one or more currencies or currency units other than that or those in which the debt securities are denominated, the manner in which the exchange rate with respect to these payments will be determined;

• the manner in which the amounts of payment of principal of, premium, if any, or interest on the debt securities will be determined, if these amounts may be determined by reference to an index based on a currency or currencies or by reference to a commodity, commodity index, stock exchange index or financial index;

• any provisions relating to any security provided for the debt securities;

• any addition to, deletion of or change in the Events of Default described in this prospectus or in the indenture with respect to the debt securities and any change in the acceleration provisions described in this prospectus or in the indenture with respect to the debt securities;

• any addition to, deletion of or change in the covenants described in this prospectus or in the indenture with respect to the debt securities;

• any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents with respect to the debt securities;

• the provisions, if any, relating to conversion or exchange of any debt securities of such series, including if applicable, the conversion or exchange price and period, provisions as to whether conversion or exchange will be mandatory, the events requiring an adjustment of the conversion or exchange price and provisions affecting conversion or exchange;

• any other terms of the debt securities, which may supplement, modify or delete any provision of the indenture as it applies to that series, including any terms that may be required under applicable law or regulations or advisable in connection with the marketing of the securities; and

• whether any of our direct or indirect subsidiaries will guarantee the debt securities of that series, including the terms of subordination, if any, of such guarantees. (Section 2.2)

We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

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If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of and any premium and interest on any series of debt securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

Each debt security will be represented by either one or more global securities registered in the name of The Depository Trust Company (the “Depositary”), or a nominee of the Depositary (we will refer to any debt security represented by a global debt security as a “book-entry debt security”), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a “certificated debt security”) as set forth in the applicable prospectus supplement. Except as set forth under the heading “Global Debt Securities and Book-Entry System” below, book-entry debt securities will not be issuable in certificated form.

Certificated Debt Securities. You may transfer or exchange certificated debt securities at any office we maintain for this purpose in accordance with the terms of the indenture. (Section 2.4) No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange. (Section 2.7)

You may effect the transfer of certificated debt securities and the right to receive the principal of, premium and interest on certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

Global Debt Securities and Book-Entry System. Each global debt security representing book-entry debt securities will be deposited with, or on behalf of, the Depositary, and registered in the name of the Depositary or a nominee of the Depositary. Please see “Global Securities.”

Covenants

We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities. (Article IV)

No Protection in the Event of a Change of Control

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Consolidation, Merger and Sale of Assets

We may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to any person (a “successor person”) unless:

• we are the surviving corporation or the successor person (if other than Zosano Pharma Corporation) is a corporation organized and validly existing under the laws of any U.S. domestic jurisdiction and expressly assumes our obligations on the debt securities and under the indenture; and

• immediately after giving effect to the transaction, no Default or Event of Default, shall have occurred and be continuing.

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Notwithstanding the above, any of our subsidiaries may consolidate with, merge into or transfer all or part of its properties to us. (Section 5.1)

Events of Default

“Event of Default” means with respect to any series of debt securities, any of the following:

• default in the payment of any interest upon any debt security of that series when it becomes due and payable, and continuance of such default for a period of 30 days (unless the entire amount of the payment is deposited by us with the trustee or with a paying agent prior to the expiration of the 30-day period);

• default in the payment of principal of any security of that series at its maturity;

• default in the performance or breach of any other covenant or warranty by us in the indenture (other than a covenant or warranty that has been included in the indenture solely for the benefit of a series of debt securities other than that series), which default continues uncured for a period of 60 days after we receive written notice from the trustee or Zosano Pharma Corporation and the trustee receive written notice from the holders of not less than 25% in principal amount of the outstanding debt securities of that series as provided in the indenture;

• certain voluntary or involuntary events of bankruptcy, insolvency or reorganization of Zosano Pharma Corporation;

• any other Event of Default provided with respect to debt securities of that series that is described in the applicable prospectus supplement. (Section 6.1)

No Event of Default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an Event of Default with respect to any other series of debt securities. (Section 6.1) The occurrence of certain Events of Default or an acceleration under the indenture may constitute an event of default under certain indebtedness of ours or our subsidiaries outstanding from time to time.

We will provide the trustee written notice of any Default or Event of Default within 30 days of becoming aware of the occurrence of such Default or Event of Default, which notice will describe in reasonable detail the status of such Default or Event of Default and what action we are taking or propose to take in respect thereof. (Section 6.1)

If an Event of Default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than 25% in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal of (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an Event of Default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all Events of Default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. (Section 6.2) We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an Event of Default.

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The indenture provides that the trustee may refuse to perform any duty or exercise any of its rights or powers under the indenture unless the trustee receives indemnity satisfactory to it against any cost, liability or expense which might be incurred by it in performing such duty or exercising such right or power. (Section 7.1(e)) Subject to certain rights of the trustee, 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. (Section 6.12)

No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

• that holder has previously given to the trustee written notice of a continuing Event of Default with respect to debt securities of that series; and

• the holders of not less than 25% in principal amount of the outstanding debt securities of that series have made written request, and offered indemnity or security satisfactory to the trustee, to the trustee to institute the proceeding as trustee, and the trustee has not received from the holders of not less than a majority in principal amount of the outstanding debt securities of that series a direction inconsistent with that request and has failed to institute the proceeding within 60 days. (Section 6.7)

Notwithstanding any other provision in the indenture, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, premium and any interest on that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment. (Section 6.8)

The indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. (Section 4.3) If a Default or Event of Default occurs and is continuing with respect to the securities of any series and if it is known to a responsible officer of the trustee, the trustee shall mail to each Securityholder of the securities of that series notice of a Default or Event of Default within 90 days after it occurs or, if later, after a responsible officer of the trustee has knowledge of such Default or Event of Default. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any Default or Event of Default (except in payment on any debt securities of that series) with respect to debt securities of that series if the trustee determines in good faith that withholding notice is in the interest of the holders of those debt securities. (Section 7.5)

Modification and Waiver

We and the trustee may modify, amend or supplement the indenture or the debt securities of any series without the consent of any holder of any debt security:

• to cure any ambiguity, defect or inconsistency;

• to comply with covenants in the indenture described above under the heading “Consolidation, Merger and Sale of Assets”;

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

• to add guarantees with respect to debt securities of any series or secure debt securities of any series;

• to surrender any of our rights or powers under the indenture;

• to add covenants or events of default for the benefit of the holders of debt securities of any series;

• to comply with the applicable procedures of the applicable depositary;

• to make any change that does not adversely affect the rights of any holder of debt securities;

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• to provide for the issuance of and establish the form and terms and conditions of debt securities of any series as permitted by the indenture;

• to effect the appointment of a successor trustee with respect to the debt securities of any series and to add to or change any of the provisions of the indenture to provide for or facilitate administration by more than one trustee; or

• to comply with requirements of the SEC in order to effect or maintain the qualification of the indenture under the Trust Indenture Act. (Section 9.1)

We may also modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

• reduce the amount of debt securities whose holders must consent to an amendment, supplement or waiver;

• reduce the rate of or extend the time for payment of interest (including default interest) on any debt security;

• reduce the principal of or premium on or change the fixed maturity of any debt security or reduce the amount of, or postpone the date fixed for, the payment of any sinking fund or analogous obligation with respect to any series of debt securities;

• reduce the principal amount of discount securities payable upon acceleration of maturity;

• waive a default in the payment of the principal of, premium or interest on any debt security (except a rescission of acceleration of the debt securities of any series by the holders of at least a majority in aggregate principal amount of the then outstanding debt securities of that series and a waiver of the payment default that resulted from such acceleration);

• make the principal of or premium or interest on any debt security payable in currency other than that stated in the debt security;

• make any change to certain provisions of the indenture relating to, among other things, the right of holders of debt securities to receive payment of the principal of, premium and interest on those debt securities and to institute suit for the enforcement of any such payment and to waivers or amendments; or

• waive a redemption payment with respect to any debt security. (Section 9.3)

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. (Section 9.2) The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on any debt security of that series; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration. (Section 6.13)

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

Legal Defeasance. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (subject to certain exceptions). We will be so discharged upon the irrevocable deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single

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currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money or U.S. government obligations in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the United States Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable United States federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred. (Section 8.3)

Defeasance of Certain Covenants. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

• we may omit to comply with the covenant described under the heading “Consolidation, Merger and Sale of Assets” and certain other covenants set forth in the indenture, as well as any additional covenants which may be set forth in the applicable prospectus supplement; and

• any omission to comply with those covenants will not constitute a Default or an Event of Default with respect to the debt securities of that series (“covenant defeasance”).

The conditions include:

• depositing with the trustee money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal of, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities; and

• delivering to the trustee an opinion of counsel to the effect that the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit and related covenant defeasance and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit and related covenant defeasance had not occurred. (Section 8.4)

No Personal Liability of Directors, Officers, Employees or Securityholders

None of our past, present or future directors, officers, employees or securityholders, as such, will have any liability for any of our obligations under the debt securities or the indenture or for any claim based on, or in respect or by reason of, such obligations or their creation. By accepting a debt security, each holder waives and releases all such liability. This waiver and release is part of the consideration for the issue of the debt securities. However, this waiver and release may not be effective to waive liabilities under U.S. federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

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Governing Law

The indenture and the debt securities, including any claim or controversy arising out of or relating to the indenture or the securities, will be governed by the laws of the State of New York.

The indenture will provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to the indenture, the debt securities or the transactions contemplated thereby.

The indenture will provide that any legal suit, action or proceeding arising out of or based upon the indenture or the transactions contemplated thereby may be instituted in the federal courts of the United States of America located in the City of New York or the courts of the State of New York in each case located in the City of New York, and we, the trustee and the holder of the debt securities (by their acceptance of the debt securities) irrevocably submit to the non-exclusive jurisdiction of such courts in any such suit, action or proceeding. The indenture will further provide that service of any process, summons, notice or document by mail (to the extent allowed under any applicable statute or rule of court) to such party’s address set forth in the indenture will be effective service of process for any suit, action or other proceeding brought in any such court. The indenture will further provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the courts specified above and irrevocably and unconditionally waive and agree not to plead or claim any such suit, action or other proceeding has been brought in an inconvenient forum. (Section 10.10)

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DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of shares of our common stock or preferred stock or of debt securities. We may issue warrants independently or together with other securities, and the warrants may be attached to or separate from any offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and the investors or a warrant agent. The following summary of material provisions of the warrants and warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to a particular series of warrants. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. We urge you to read the applicable prospectus supplement and any related free writing prospectus, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants.

The particular terms of any issue of warrants will be described in the prospectus supplement relating to the issue. Those terms may include:

• the number of shares of common stock or preferred stock purchasable upon the exercise of warrants to purchase such shares and the price at which such number of shares may be purchased upon such exercise;

• the designation, stated value and terms (including, without limitation, liquidation, dividend, conversion and voting rights) of the series of preferred stock purchasable upon exercise of warrants to purchase preferred stock;

• the principal amount of debt securities that may be purchased upon exercise of a debt warrant and the exercise price for the warrants, which may be payable in cash, securities or other property;

• the date, if any, on and after which the warrants and the related debt securities, preferred stock or common stock will be separately transferable;

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

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

• United States Federal income tax consequences applicable to the warrants; and

• any additional terms of the warrants, including terms, procedures, and limitations relating to the exchange, exercise and settlement of the warrants.

Holders of equity warrants will not be entitled:

• to vote, consent or receive dividends;

• receive notice as stockholders with respect to any meeting of stockholders for the election of our directors or any other matter; or

• exercise any rights as stockholders of the Company.

Each warrant will entitle its holder to purchase the principal amount of debt securities or the number of shares of preferred stock or common stock at the exercise price set forth in, or calculable as set forth in, the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

A holder of warrant certificates may exchange them for new warrant certificates of different denominations, present them for registration of transfer and exercise them at the corporate trust office of the warrant agent or any

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other office indicated in the applicable prospectus supplement. Until any warrants to purchase debt securities are exercised, the holder of the warrants will not have any rights of holders of the debt securities that can be purchased upon exercise, including any rights to receive payments of principal, premium or interest on the underlying debt securities or to enforce covenants in the applicable indenture. Until any warrants to purchase common stock or preferred stock are exercised, the holders of the warrants will not have any rights of holders of the underlying common stock or preferred stock, including any rights to receive dividends or payments upon any liquidation, dissolution or winding up on the common stock or preferred stock, if any.

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DESCRIPTION OF UNITS

We may issue units consisting of any combination of the other types of securities offered under this prospectus in one or more series. We may evidence each series of units by unit certificates that we will issue under a separate agreement. We may enter into unit agreements with a unit agent. Each unit agent will be a bank or trust company that we select. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units.

The following description, together with the additional information included in any applicable prospectus supplement, summarizes the general features of the units that we may offer under this prospectus. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreements that contain the terms of the units. Specific unit agreements will contain additional important terms and provisions and we will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from another report that we file with the SEC, the form of each unit agreement relating to units offered under this prospectus.

If we offer any units, certain terms of that series of units will be described in the applicable prospectus supplement, including, without limitation, the following, as applicable:

• the title of the series of units;

• identification and description of the separate constituent securities comprising the units;

• the price or prices at which the units will be issued;

• the date, if any, on and after which the constituent securities comprising the units will be separately transferable;

• a discussion of certain United States federal income tax considerations applicable to the units; and

• any other terms of the units and their constituent securities.

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GLOBAL SECURITIES

Book-Entry, Delivery and Form

Unless we indicate differently in any applicable prospectus supplement or free writing prospectus, the securities initially will be issued in book-entry form and represented by one or more global notes or global securities, or, collectively, global securities. The global securities will be deposited with, or on behalf of, The Depository Trust Company, New York, New York, as depositary (“DTC”), and registered in the name of Cede & Co., the nominee of DTC. Unless and until it is exchanged for individual certificates evidencing securities under the limited circumstances described below, a global security may not be transferred except as a whole by the depositary to its nominee or by the nominee to the depositary, or by the depositary or its nominee to a successor depositary or to a nominee of the successor depositary.

DTC has advised us that it is:

• a limited-purpose trust company organized under the New York Banking Law;

• a “banking organization” within the meaning of the New York Banking Law;

• a member of the Federal Reserve System;

• a “clearing corporation” within the meaning of the New York Uniform Commercial Code; and

• a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act.

DTC holds securities that its participants deposit with DTC. DTC also facilitates the settlement among its participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in participants’ accounts, thereby eliminating the need for physical movement of securities certificates. “Direct participants” in DTC include securities brokers and dealers, including underwriters, banks, trust companies, clearing corporations and other organizations. DTC is a wholly-owned subsidiary of The Depository Trust & Clearing Corporation, or DTCC. DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others, which we sometimes refer to as indirect participants, that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly. The rules applicable to DTC and its participants are on file with the SEC.

Purchases of securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of the actual purchaser of a security, which we sometimes refer to as a beneficial owner, is in turn recorded on the direct and indirect participants’ records. Beneficial owners of securities will not receive written confirmation from DTC of their purchases. However, beneficial owners are expected to receive written confirmations providing details of their transactions, as well as periodic statements of their holdings, from the direct or indirect participants through which they purchased securities. Transfers of ownership interests in global securities are to be accomplished by entries made on the books of participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except under the limited circumstances described below.

To facilitate subsequent transfers, all global securities deposited by direct participants with DTC will be registered in the name of DTC’s partnership nominee, Cede & Co., or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee will not change the beneficial ownership of the securities. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts the securities are credited, which may or may not be the beneficial owners. The participants are responsible for keeping account of their holdings on behalf of their customers.

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So long as the securities are in book-entry form, you will receive payments and may transfer securities only through the facilities of the depositary and its direct and indirect participants. We will maintain an office or agency in the location specified in the prospectus supplement for the applicable securities, where notices and demands in respect of the securities and the indenture may be delivered to us and where certificated securities may be surrendered for payment, registration of transfer or exchange.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any legal requirements in effect from time to time.

Redemption notices will be sent to DTC. If less than all of the securities of a particular series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in the securities of such series to be redeemed.

Neither DTC nor Cede & Co. (or such other DTC nominee) will consent or vote with respect to the securities. Under its usual procedures, DTC will mail an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns the consenting or voting rights of Cede & Co. to those direct participants to whose accounts the securities of such series are credited on the record date, identified in a listing attached to the omnibus proxy.

So long as securities are in book-entry form, we will make payments on those securities to the depositary or its nominee, as the registered owner of such securities, by wire transfer of immediately available funds. If securities are issued in definitive certificated form under the limited circumstances described below and unless if otherwise provided in the description of the applicable securities herein or in the applicable prospectus supplement, we will have the option of making payments by check mailed to the addresses of the persons entitled to payment or by wire transfer to bank accounts in the United States designated in writing to the applicable trustee or other designated party at least 15 days before the applicable payment date by the persons entitled to payment, unless a shorter period is satisfactory to the applicable trustee or other designated party.

Redemption proceeds, distributions and dividend payments on the securities will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC’s practice is to credit direct participants’ accounts upon DTC’s receipt of funds and corresponding detail information from us on the payment date in accordance with their respective holdings shown on DTC records. Payments by participants to beneficial owners will be governed by standing instructions and customary practices, as is the case with securities held for the account of customers in bearer form or registered in “street name.” Those payments will be the responsibility of participants and not of DTC or us, subject to any statutory or regulatory requirements in effect from time to time. Payment of redemption proceeds, distributions and dividend payments to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC, is our responsibility, disbursement of payments to direct participants is the responsibility of DTC, and disbursement of payments to the beneficial owners is the responsibility of direct and indirect participants.

Except under the limited circumstances described below, purchasers of securities will not be entitled to have securities registered in their names and will not receive physical delivery of securities. Accordingly, each beneficial owner must rely on the procedures of DTC and its participants to exercise any rights under the securities and the indenture.

The laws of some jurisdictions may require that some purchasers of securities take physical delivery of securities in definitive form. Those laws may impair the ability to transfer or pledge beneficial interests in securities.

DTC may discontinue providing its services as securities depositary with respect to the securities at any time by giving reasonable notice to us. Under such circumstances, in the event that a successor depositary is not obtained, securities certificates are required to be printed and delivered.

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As noted above, beneficial owners of a particular series of securities generally will not receive certificates representing their ownership interests in those securities. However, if:

• DTC notifies us that it is unwilling or unable to continue as a depositary for the global security or securities representing such series of securities or if DTC ceases to be a clearing agency registered under the Exchange Act at a time when it is required to be registered and a successor depositary is not appointed within 90 days of the notification to us or of our becoming aware of DTC’s ceasing to be so registered, as the case may be;

• we determine, in our sole discretion, not to have such securities represented by one or more global securities; or

• an Event of Default has occurred and is continuing with respect to such series of securities,

we will prepare and deliver certificates for such securities in exchange for beneficial interests in the global securities. Any beneficial interest in a global security that is exchangeable under the circumstances described in the preceding sentence will be exchangeable for securities in definitive certificated form registered in the names that the depositary directs. It is expected that these directions will be based upon directions received by the depositary from its participants with respect to ownership of beneficial interests in the global securities.

Euroclear and Clearstream

If so provided in the applicable prospectus supplement, you may hold interests in a global security through Clearstream Banking S.A. (“Clearstream”), or Euroclear Bank S.A./N.V., as operator of the Euroclear System (“Euroclear”), either directly if you are a participant in Clearstream or Euroclear or indirectly through organizations which are participants in Clearstream or Euroclear. Clearstream and Euroclear will hold interests on behalf of their respective participants through customers’ securities accounts in the names of Clearstream and Euroclear, respectively, on the books of their respective U.S. depositaries, which in turn will hold such interests in customers’ securities accounts in such depositaries’ names on DTC’s books.

Clearstream and Euroclear are securities clearance systems in Europe. Clearstream and Euroclear hold securities for their respective participating organizations and facilitate the clearance and settlement of securities transactions between those participants through electronic book-entry changes in their accounts, thereby eliminating the need for physical movement of certificates.

Payments, deliveries, transfers, exchanges, notices and other matters relating to beneficial interests in global securities owned through Euroclear or Clearstream must comply with the rules and procedures of those systems. Transactions between participants in Euroclear or Clearstream, on one hand, and other participants in DTC, on the other hand, are also subject to DTC’s rules and procedures.

Investors will be able to make and receive through Euroclear and Clearstream payments, deliveries, transfers and other transactions involving any beneficial interests in global securities held through those systems only on days when those systems are open for business. Those systems may not be open for business on days when banks, brokers and other institutions are open for business in the United States.

Cross-market transfers between participants in DTC, on the one hand, and participants in Euroclear or Clearstream, on the other hand, will be effected through DTC in accordance with the DTC’s rules on behalf of Euroclear or Clearstream, as the case may be, by their respective U.S. depositaries; however, such cross-market transactions will require delivery of instructions to Euroclear or Clearstream, as the case may be, by the counterparty in such system in accordance with the rules and procedures and within the established deadlines (European time) of such system. Euroclear or Clearstream, as the case may be, will, if the transaction meets its settlement requirements, deliver instructions to its U.S. depositary to take action to effect final settlement on its behalf by delivering or receiving interests in the global securities through DTC, and making or receiving payment in accordance with normal procedures for same-day fund settlement. Participants in Euroclear or Clearstream may not deliver instructions directly to their respective U.S. depositaries.

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Due to time zone differences, the securities accounts of a participant in Euroclear or Clearstream purchasing an interest in a global security from a direct participant in DTC will be credited, and any such crediting will be reported to the relevant participant in Euroclear or Clearstream, during the securities settlement processing day (which must be a business day for Euroclear or Clearstream) immediately following the settlement date of DTC. Cash received in Euroclear or Clearstream as a result of sales of interests in a global security by or through a participant in Euroclear or Clearstream to a direct participant in DTC will be received with value on the settlement date of DTC but will be available in the relevant Euroclear or Clearstream cash account only as of the business day for Euroclear or Clearstream following DTC’s settlement date.

Other

The information in this section of this prospectus concerning DTC, Clearstream, Euroclear and their respective book-entry systems has been obtained from sources that we believe to be reliable, but we do not take responsibility for this information. This information has been provided solely as a matter of convenience. The rules and procedures of DTC, Clearstream and Euroclear are solely within the control of those organizations and could change at any time. Neither we nor the trustee nor any agent of ours or of the trustee has any control over those entities and none of us takes any responsibility for their activities. You are urged to contact DTC, Clearstream and Euroclear or their respective participants directly to discuss those matters. In addition, although we expect that DTC, Clearstream and Euroclear will perform the foregoing procedures, none of them is under any obligation to perform or continue to perform such procedures and such procedures may be discontinued at any time. Neither we nor any agent of ours will have any responsibility for the performance or nonperformance by DTC, Clearstream and Euroclear or their respective participants of these or any other rules or procedures governing their respective operations.

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PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods or through underwriters or dealers, through agents and/or directly to one or more purchasers. The securities may be distributed 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.

Each time that we sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms and conditions of the offering of such securities, including the offering price of the securities and the proceeds to us, if applicable.

Offers to purchase the securities being offered by this prospectus may be solicited directly. Agents may also be designated to solicit offers to purchase the securities from time to time. Any agent involved in the offer or sale of our securities will be identified in a prospectus supplement.

If a dealer is utilized in the sale of the securities being offered by this prospectus, the securities will be sold to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

If an underwriter is utilized in the sale of the securities being offered by this prospectus, an underwriting agreement will be executed with the underwriter at the time of sale and the name of any underwriter will be provided in the prospectus supplement that the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we or the purchasers of securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or commissions. The underwriter may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for which they may act as agent. Unless otherwise indicated in a prospectus supplement, an agent will be acting on a best efforts basis and a dealer will purchase securities as a principal, and may then resell the securities at varying prices to be determined by the dealer.

Any compensation paid to underwriters, dealers or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers will be provided in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act of 1933, as amended (the “Securities Act”), and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We may enter into agreements to indemnify underwriters, dealers and agents against civil liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make in respect thereof and to reimburse those persons for certain expenses.

Any common stock will be listed on the Nasdaq Capital Market, but any other securities may or may not be listed on a national securities exchange. To facilitate the offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than were sold to them. In these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment

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option, if any. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement so indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be named in the applicable prospectus supplement (or a post-effective amendment). In addition, we may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus and an applicable prospectus supplement. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business for which they receive compensation.

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LEGAL MATTERS

Latham & Watkins LLP will pass upon certain legal matters relating to the issuance and sale of the securities offered hereby on behalf of Zosano Pharma Corporation. 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 incorporated in this Registration Statement by reference from the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in its report, which is incorporated herein by reference (which report expresses an unqualified opinion on the financial statements and includes an explanatory paragraph referring to the Company’s ability to continue as a going concern). Such financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

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51,250,000 Units Each Consisting of One Share of Common Stock and One Series F Warrant to Purchase One Share of Common Stock

Prospectus Supplement

Sole Book-Running Manager

Maxim Group LLC

February 8, 2022