F-star Therapeutics (FSTX) 424B5 Prospectus supplement for primary offering

Filed pursuant to Rule 424(b)(5)
Registration No. 333-218399

PROSPECTUS SUPPLEMENT

(To prospectus dated June 12, 2017)

3,000,000 Shares

Spring Bank Pharmaceuticals, Inc.

Common Stock

We are offering 3,000,000 shares of our common stock pursuant to this prospectus supplement. Our common stock is listed on the Nasdaq Capital Market under the symbol “SBPH.” On August 8, 2018, the last reported sale price of shares of our common stock on the Nasdaq Capital Market was $14.10 per share.

Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on page S-8 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement and accompanying prospectus.

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

	PER SHARE		TOTAL
Public offering price	$	12.50	$	37,500,000
Underwriting discounts and commissions(1)	$	0.75	$	2,250,000
Proceeds to Spring Bank Pharmaceuticals, Inc., before expenses	$	11.75	$	35,250,000

(1) See “Underwriting” beginning on pageS-18 of this prospectus supplement for a description of the compensation payable to the underwriters.

Delivery of the shares of common stock is expected to be made on or about August 13, 2018. We have granted the underwriters a30-day option from the date of this prospectus supplement to purchase up to 450,000 additional shares of our common stock. If the underwriters exercise the option in full, the underwriting discounts and commissions payable by us will be $2,587,500, and the total proceeds to us, before expenses, will be $40,537,500.

Joint Book-Running Managers

Jefferies Piper Jaffray

Prospectus Supplement dated August 8, 2018

TABLE OF CONTENTS

PROSPECTUS SUPPLEMENT

ABOUT THIS PROSPECTUS SUPPLEMENT	S-1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS	S-3
PROSPECTUS SUPPLEMENT SUMMARY	S-4
THE OFFERING	S-7
RISK FACTORS	S-8
USE OF PROCEEDS	S-10
DILUTION	S-11
PRICE RANGE OF OUR COMMON STOCK	S-12
DIVIDEND POLICY	S-13
MATERIAL U.S. FEDERAL TAX CONSIDERATIONS	S-14
UNDERWRITING	S-18
LEGAL MATTERS	S-26
EXPERTS	S-26
WHERE YOU CAN FIND MORE INFORMATION	S-26
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	S-27

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts and is part of the registration statement (No.333-218399) that we filed with the Securities and Exchange Commission, or the SEC, using a “shelf” registration process. The first part is this prospectus supplement, which describes the specific terms of this common stock offering and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference herein. The second part, the accompanying prospectus dated June 12, 2017, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying prospectus or any document incorporated by reference herein or therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement; provided that 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 the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

Neither we nor the underwriters have authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus supplement, the accompanying prospectus or in any free writing prospectus 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. The information contained in this prospectus supplement or the accompanying prospectus, or incorporated by reference herein or therein is accurate only as of the respective dates thereof, regardless of the time of delivery of this prospectus supplement and the accompanying prospectus or of any sale of our common stock. It is important for you to read and consider all information contained in this prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, in making your investment decision. You should also read and consider the information in the documents to which we have referred you in the sections entitled “Where You Can Find More Information” and “Incorporation of Certain Information by Reference” in this prospectus supplement and in the accompanying prospectus.

This prospectus supplement and the accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer to purchase, the securities offered by this prospectus supplement and the accompanying prospectus in any jurisdiction to or from any person to whom or from whom it is unlawful to make such offer or solicitation of an offer in such jurisdiction. We are not, and the underwriters are not, offering to sell, and seeking offers to buy, shares of our common stock in jurisdictions where offers and sales are prohibited. The distribution of this prospectus supplement and the accompanying prospectus and the offering of the common stock in certain jurisdictions may be restricted by law. No action is being taken in any jurisdiction outside the United States to permit a public offering of the securities or possession or distribution of this prospectus supplement or the accompanying prospectus in that jurisdiction. Persons who come into possession of this prospectus supplement or the accompanying prospectus in jurisdictions outside the United States are required to inform themselves about and to observe any restrictions as to this offering and the distribution of this prospectus supplement or the accompanying prospectus applicable to that jurisdiction.

Unless otherwise stated, all references in this prospectus supplement and the accompanying prospectus to “we,” “us,” “our,” “Spring Bank,” “the Company” and similar designations refer, collectively, to Spring Bank Pharmaceuticals, Inc., and its subsidiaries.

Market data and industry statistics and forecasts used throughout this prospectus supplement are based on the good faith estimates of management, which in turn are based upon management’s reviews of independent industry

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publications, reports by market research firms, and other independent and publicly available sources. Although we are not aware of any misstatements regarding the industry data that we present in this prospectus supplement, our estimates involve risks and uncertainties and are subject to change based on various factors, including those discussed under “Risk Factors,” “Special Note Regarding Forward-Looking Statements” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form10-K for the fiscal year ended December 31, 2017, incorporated by reference in this prospectus supplement, as well as our subsequent filings with the SEC also incorporated by reference herein.

We own or have rights to trademarks, trade names and service marks that we use in connection with the operation of our business, including our corporate name, logos and website names. Other trademarks, trade names and service marks appearing in this prospectus are the property of their respective owners. Solely for convenience, the trademarks and trade names in this prospectus may be referred to without the^® and ™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein include “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. All statements, other than statements of historical facts, included in this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans, objectives of management and expected market growth are forward-looking statements. The words “anticipate,” “believe,” “contemplate,” “estimate,” “expect,” “forecast,” “intend,” “may,” “plan,” “predict,” “project,” “target,” “potential,” “will,” “would,” “could,” “should,” “continue” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. These forward-looking statements include, among other things, statements about:

∎ preclinical study data and clinical trial data, and the success, cost and timing of our product development activities and current and future clinical trials;

∎ the timing of and our ability to obtain and maintain regulatory approvals for any of our product candidates;

∎ whether our product candidates will satisfactorily demonstrate safety and efficacy to the FDA and other comparable regulatory organizations;

∎ our ability to identify and develop new product candidates;

∎ our intellectual property position;

∎ our commercialization, marketing and manufacturing capabilities and strategy;

∎ our ability to develop sales and marketing capabilities;

∎ our ability to identify, recruit and retain key personnel;

∎ our financial performance and our ability to fund our working capital requirements;

∎ developments and projections relating to our competitors in the industry;

∎ our expectations regarding the time during which we will be an emerging growth company under the Jumpstart Our Business Startups Act of 2012, or the JOBS Act;

∎ our expectations related to the use of proceeds from this offering; and

∎ our estimates regarding expenses, future revenue, capital requirements and needs for additional financing.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included in this prospectus supplement, the accompanying prospectus, and the information incorporated by reference herein and therein, particularly in the “Risk Factors” sections of this prospectus supplement, the accompanying prospectus and of our Annual Report on Form10-K for the year ended December 31, 2017, which is incorporated by reference herein, that could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments that we may make.

You should read this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein completely and with the understanding that our actual future results may be materially different from what we expect. Any forward-looking statement speaks only as of the date of this prospectus supplement. We do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights selected information contained elsewhere in this prospectus supplement and the accompanying prospectus and in the documents we incorporate by reference. This summary does not contain all of the information you should consider before investing in our common stock. You should read this entire prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, carefully, especially the risks of investing in our common stock discussed under “Risk Factors” beginning on pageS-8 of this prospectus supplement and the “Risk Factors” section of our Annual Report on Form10-K for the year ended December 31, 2017, along with our consolidated financial statements and notes to those consolidated financial statements, before making an investment decision.

About Spring Bank Pharmaceuticals

We are a clinical-stage biopharmaceutical company engaged in the discovery and development of a novel class of therapeutics using our proprietary small molecule nucleic acid hybrid, or SMNH, chemistry platform. Our SMNH compounds are synthetic nucleotide segments that are designed to mimic the interactions of nucleic acids with proteins. We design our SMNH compounds to selectively target and modulate the activity of specific proteins implicated in various disease states. We are developing our lead SMNH product candidate, inarigivir soproxil, or inarigivir, for the treatment of chronic hepatitis B virus, or HBV. We have designed our antiviral product candidates, including inarigivir, to selectively activate within infected cells the cellular protein, retinoic acid-inducible gene 1(RIG-I), to inhibit viral replication and to cause the induction of intracellular interferon signaling pathways for antiviral defense. We believe that inarigivir, as aRIG-I agonist, if approved, could play an important role in antiviral therapy as a result of its dual mechanism of action that is designed to selectively modulate the body’s immune response and inhibit viral replication. We are also developing additional SMNH product candidates, including our lead STING (STimulator of INterferon Genes) agonist product candidate, SB 11285, which is an immunotherapeutic agent for the potential treatment of selected cancers.

In April 2017, the World Health Organization, or WHO, Global Hepatitis Report estimated that 257 million people are chronically infected with chronic HBV worldwide, and nearly 900,000 people worldwide die every year due to complications from chronic HBV infection despite the availability of vaccines against the virus. There is no approved cure for chronic HBV and currently approved direct-acting antiviral therapies for the treatment of chronic HBV lack a broadly sustained response following the discontinuation of treatment.

We are developing inarigivir, an orally-administered investigational selective immunomodulator, as a potential backbone in a combinatorial treatment for chronic HBV, with a goal to accelerate and substantially increase functional cure rates in a simple, safe and selective manner. We are currently conducting a global Phase 2 multi-center clinical trial of inarigivir, which we refer to as the ACHIEVE trial. We are also pursuing the development of SB 9225, aco-formulation of inarigivir with tenofovir disoproxil fumarate, as a potential fixed-dose combination product for the treatment of patients with chronic HBV. In addition to the ACHIEVE trial, we continue to explore collaborations, including with siRNA compounds targeting hepatitis B surface antigen, or HBsAg, as well as other antiviral and immunomodulatory mechanisms, and we anticipate that inarigivir will be included in a “triple combination” clinical trial with an siRNA compound or a different mechanism in the first half of 2019. We believe the immunomodulatory activity of inarigivir could become a key component of a future combinatorial treatment for patients infected with chronic HBV, increasing the percentage of chronic HBV patients who achieve a functional cure.

In addition to inarigivir, we are developing our lead STING agonist product candidate, SB 11285, as a potential next-generation immunotherapeutic agent for the treatment of selected cancers. In our preclinical studies in multiple tumor-derived cell lines, SB 11285 has been observed to cause the induction of cytokines consistent with engagement of the target, as well as cell death and apoptosis. Based on our preclinical studies performed to date, SB 11285 has reduced tumor volumes, without dose-limiting toxicities, in multiple rodent

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tumor models when administered intravenously or intratumorally. These findings lead us to believe that SB 11285 has the potential to be administered clinically by either route of administration, and that SB 11285 may be used to target a variety of tumors at various anatomic sites and, if approved, has the potential to be used in combination with other therapeutic modalities to enhance efficacy. We are currently advancing the SB 11285 program with preclinical, toxicology, and process development efforts. Subject to the results of these preclinical studies, we anticipate that we will submit a clinical trial application for SB 11285 by early 2019, and, if approved, initiate a Phase 1b clinical trial in cancer later in the first half of 2019.

Recent Developments

On August 2, 2018, we announced results from the third cohort (inarigivir 100mg) of Part A of the ACHIEVE trial. In the third cohort, 20 patients were randomized; 17 on inarigivir 100mg (13 HBeAg-positive, 4 HBeAg-negative) and 3 on placebo. The primary endpoints, safety and antiviral activity, were achieved at both week 12 (inarigivir monotherapy) and week 24 (following the switch to Gilead Science’s Viread^® 300mg (tenofovir disoproxil fumarate, or TDF) after week 12). Inarigivir was well tolerated with no serious adverse events observed. Overall, treatment-emergent adverse events ranged from mild to moderate in severity, with no observed interferon-like side effects or clinical or biochemical events above Grade 3. One HBeAg-negative patient on inarigivir alone had an ALT flare >200 IU with reductions in HBV DNA and HBsAg consistent with previously described inarigivir immune flares. We observed a maximum reduction in both HBV DNA and HBV RNA by up to 2.76log₁₀ and 5.0log₁₀, respectively. Overall, mean HBV DNA reduction at week 12 was 1.0log₁₀, with a mean 0.55log₁₀ reduction in HBeAg-positive patients and a mean 2.26log₁₀ reduction in HBeAg-negative patients, which was significantly superior(t-test: p=0.006) to combined placebo from all groups (n=11). Similar log reductions were seen for the secondary endpoint of HBV RNA reduction, with a mean 0.6log₁₀ reduction in HBeAg-positive patients and a mean 1.4log₁₀ reduction in HBeAg-negative patients. Three patients had a greater than 0.5log₁₀ reduction in HBsAg at either week 12 or week 24. Overall, 13 of 47 (28%) of inarigivir-treated patients in the ACHIEVE trial have had a predefined HBsAg response of 0.5log₁₀ decrease, with a mean decrease in the responder group of 0.8log₁₀ (range 0.5 – 1.4log₁₀) at either week 12 or week 24 after the switch to TDF.

Inarigivir responses have been proportional to the baseline HBsAg level and we believe are reflective of the mechanism of action of inarigivir as an immunomodulator. Baseline HBsAg level < 10,000 IU (4log₁₀) has been the strongest predictor of response to inarigivir across all cohorts for HBV DNA and HBV RNA reductions irrespective of HBeAg status. We believe this response is consistent with the known role of HBsAg as a down regulator of the host immune response to HBV.

We have randomized the majority of the patients in the fourth and final cohort (inarigivir 200mg) of the ACHIEVE trial and anticipate that we will havetop-line results by the end of 2018 and 24 week results in the first half of 2019.

In July 2017, we entered into a clinical trial supply and collaboration agreement with Gilead Sciences, Inc., or Gilead, under which Gilead is funding and conducting a Phase 2 clinical trial examining the co-administration of inarigivir and Vemlidy^® 25 mg (tenofovir alafenamide) in patients infected with chronic HBV. We anticipate that we will have initial results from the inarigivir 50mg + Vemlidy^® trial in the first half of 2019. On August 2, 2018, we announced the expansion of the clinical trial being undertaken by Gilead to include two additional cohorts. The new second cohort of the study will assess inarigivir 200mgco-administered with Vemlidy^®, subject to independent regulator assessments of the safety of inarigivir at the 200mg dose. Additionally, a new third cohort has been added to examine the administration of inarigivir 100mg in chronic HBV patients currently treated with nucleoside/tide analogues (a “Nuc-suppressed” population).

The expansion of the inarigivir + Vemlidy^®co-administration program means that the planned Part B of the ACHIEVE trial evaluating inarigivir with Viread^® 300mg is no longer necessary, which allows us to conclude the ACHIEVE trial when the fourth cohort (200mg) of Part A is completed. This expansion also permits us to advance our inarigivir development program into multiple planned Phase 2b/3 programs in early 2019.

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Currently-planned clinical trials include: 1) inarigivir monotherapy as anadd-on to Nuc-suppressed HBV patients (“Suppress and Shock”) and 2) HBV patients who stop Nuc therapy (“Stop and Shock”). In addition to advancing inarigivir into a Phase 2b/3 program, we plan to initiate a Phase 2b trial with SB 9225, the investigational fixed-dose combination of inarigivir and tenofovir disoproxil fumarate, fortreatment-naïve HBV patients.

Our Corporate Information

We were incorporated under the laws of the Commonwealth of Massachusetts as Spring Bank Technologies, Inc. on October 7, 2002. On May 12, 2008, we filed a certificate of incorporation in the State of Delaware and changed our state of incorporation to Delaware and our name to Spring Bank Pharmaceuticals, Inc. Our principal executive offices are located at 35 Parkwood Drive, Suite 210, Hopkinton, MA 01748, and our telephone number is (508)473-5993. Our website address iswww.springbankpharm.com. The information contained in, or accessible through, our website does not constitute a part of this prospectus.

Implications of Being an Emerging Growth Company

The Jumpstart Our Business Startups Act of 2012, or the JOBS Act, was enacted in April 2012 with the intention of encouraging capital formation in the United States and reducing the regulatory burden on newly public companies that qualify as “emerging growth companies.” We are an emerging growth company within the meaning of the JOBS Act. As an emerging growth company, we may take advantage of certain exemptions from various public reporting requirements, including the requirement that our internal control over financial reporting be audited by our independent registered public accounting firm pursuant to Section 404 of the Sarbanes-Oxley Act of 2002, certain requirements related to the disclosure of executive compensation in this prospectus and in our periodic reports and proxy statements, and the requirement that we hold a nonbinding advisory vote on executive compensation and any golden parachute payments. We may choose to take advantage of some, all or none of these reduced burdens until we are no longer an emerging growth company. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests.

We will remain an emerging growth company until the earliest to occur of:

∎ the last day of the fiscal year in which we have $1.07 billion or more in annual gross revenue;

∎ the date we qualify as a “large accelerated filer,” with at least $700 million of equity securities held by non- affiliates;

∎ the date on which we have issued, in any three-year period, more than $1.0 billion innon-convertible debt securities; or

∎ the last day of the fiscal year ending after the fifth anniversary of the closing of our initial public offering.

Section 102(b)(1) of the JOBS Act exempts emerging growth companies from being required to comply with new or revised financial accounting standards until private companies (that is, those that have not had a registration statement under the Securities Act of 1933, as amended, or the Securities Act, declared effective or do not have a class of securities registered under the Securities Exchange Act of 1934, as amended, or the Exchange Act) are required to comply with the new or revised financial accounting standard. We have chosen to “opt out” of the extended transition periods available under the JOBS Act for complying with new or revised accounting standards. Section 107 of the JOBS Act provides that our decision to opt out of the extended transition periods for complying with new or revised accounting standards is irrevocable.

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THE OFFERING

Common stock offered by us 3,000,000 shares

Common stock to be outstanding immediately after this offering 16,182,567 shares (or 16,632,567 shares if the underwriters exercise in full their option to purchase additional shares)

Option to purchase additional shares We have granted the underwriters an option to purchase up to 450,000 additional shares of our common stock. This option is exercisable, in whole or in part, for a period of 30 days from the date of this prospectus supplement.

Use of Proceeds We estimate that the net proceeds to us from the shares sold by us to the underwriters in this offering, after deducting estimated offering expenses payable by us, will be approximately $35.0 million ($40.3 million if the underwriters exercise their option to purchase additional shares in full). We currently intend to use the net proceeds from this offering to fund clinical trials, nonclinical studies, research and development and for general corporate purposes. See “Use of Proceeds” for more information.

Risk Factors Investing in our common stock involves a high degree of risk. You should read the “Risk Factors” section of this prospectus supplement, as well as those risk factors that are incorporated by reference in this prospectus supplement and the accompanying prospectus, for a discussion of factors to consider carefully before deciding to purchase shares of our common stock.

Nasdaq Capital Market symbol “SBPH”

The number of shares of our common stock to be outstanding after this offering is based on 13,182,567 shares of our common stock issued and outstanding as of June 30, 2018 and excludes:

∎ 1,338,565 shares of our common stock issuable upon the exercise of stock options outstanding as of June 30, 2018, at a weighted-average exercise price of $11.21 per share;

∎ 1,787,124 shares of our common stock issuable upon the exercise of warrants outstanding as of June 30, 2018, at a weighted-average exercise price of $11.22 per share; and

∎ 956,290 shares of common stock available for future issuance under our Amended and Restated 2015 Stock Incentive Plan as of June 30, 2018.

Unless otherwise indicated, this prospectus supplement reflects and assumes the following:

∎ no exercise of outstanding stock options or warrants described above;

∎ no purchases of shares of our common stock by our existing stockholders in this offering; and

∎ no exercise by the underwriters of their option to purchase additional shares of our common stock.

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RISK FACTORS

Investing in our common stock involves a high degree of risk. Before investing in our common stock, you should consider carefully the risks described below and under the heading “Risk Factors” in our Annual Report on Form10-K for the year ended December 31, 2017, filed with the Securities and Exchange Commission, or SEC, on February 20, 2018, and our Quarterly Report on Form10-Q for the quarter ended June 30, 2018, filed with the SEC on August 2, 2018, which are incorporated by reference into this prospectus supplement, together with the other information contained in this prospectus supplement, the accompanying prospectus and in our other filings with the SEC that we have incorporated by reference in this prospectus supplement and the accompanying prospectus. If any of these risks occur, our business, financial condition, results of operations and future growth prospects could be materially and adversely affected. In these circumstances, the market price of our common stock could decline, and you may lose all or part of your investment.

Risks Related to this Offering

If you purchase shares of common stock in this offering, you will suffer immediate and substantial dilution in the book value of your investment.

The price per share of our common stock in this offering may exceed the net tangible book value per share of our common stock outstanding prior to this offering. Therefore, if you purchase shares of our common stock in this offering, you may pay a price per share that substantially exceeds our net tangible book value per share after this offering. To the extent shares are issued under outstanding options at exercise prices lower than the price of our common stock in this offering, you will incur further dilution. See the section entitled “Dilution” below for a more detailed illustration of the dilution you would incur if you participate in 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 at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price per share paid by investors in this offering.

We have broad discretion in the use of our cash and cash equivalents, including the net proceeds we receive in this offering, and may not use them effectively.

Our management has broad discretion to use our cash and cash equivalents, including the net proceeds we receive in this offering, to fund our operations and could spend these funds in ways that do not improve our results of operations or enhance the value of our common stock. The failure by our management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our common stock to decline and delay the development of our drug candidates. Pending their use to fund our operations, we may invest our cash and cash equivalents, including the net proceeds from this offering, in a manner that does not produce income or that loses value.

Sales of a significant number of shares of our common stock in the public markets, or the perception that such sales could occur, 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 intend to sell shares, could reduce the market price of our common stock. After this offering, assuming that the underwriters do not exercise their option to purchase additional shares, we will have outstanding 16,182,567 shares of common stock based on 13,182,567 shares outstanding as of June 30, 2018. This includes the shares that we are selling in this offering, which may be resold in the public market immediately without restriction, unless purchased by our affiliates. Of the remaining shares, approximately 1,470,307 shares are subject to a contractuallock-up with the underwriters for this offering for 90 days immediately following the date of the final prospectus supplement for this offering. The representatives of the underwriters may, in their discretion, release the restrictions on any such shares at any time without notice. After the earlier of the expiration of, or release from, thelock-up period, the holders of these shares may at any time decide to sell their shares in the public market.

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Because we have no current plans to pay cash dividends on our common stock for the foreseeable future, you may not receive any return on investment unless you sell your common stock for a price greater than that which you paid for it.

We intend to retain future earnings, if any, for future operations and expansion of our business and have no current plans to pay any cash dividends for the foreseeable future. The declaration, amount and payment of any future dividends on shares of common stock will be at the sole discretion of our Board of Directors. Our Board of Directors may take into account general and economic conditions, our financial condition, and results of operations, our available cash and current and anticipated cash needs, capital requirements, contractual, legal, tax and regulatory restrictions, implications on the payment of dividends by us to our stockholders or by our subsidiaries to us and such other factors as our Board of Directors may deem relevant. In addition, our ability to pay dividends may be limited by covenants of any future indebtedness we or our subsidiaries incur. As a result, you may not receive any return on an investment in our common stock unless you sell our common stock for a price greater than that which you paid for it.

If securities analysts do not publish research or reports about our business or if they downgrade our stock or our sector, our stock price and trading volume could decline.

The trading market for our common stock relies in part on the research and reports that industry or financial analysts publish about us or our business. We do not control these analysts. Furthermore, if one or more of the analysts who do cover us downgrades our stock or our industry, or the stock of any of our competitors, or publish inaccurate or unfavorable research about our business, the price of our stock could decline. If one or more of these analysts ceases coverage of the Company or fails to publish reports on us regularly, we could lose visibility in the market, which in turn could cause our stock price or trading volume to decline.

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USE OF PROCEEDS

We estimate that the net proceeds from the sale of shares of common stock to the underwriters in this offering will be approximately $35.0 million ($40.3 million if the underwriters’ option to purchase additional shares is exercised in full), after deducting estimated offering expenses payable by us.

We currently intend to use the net proceeds from this offering to fund clinical trials, nonclinical studies, research and development and for general corporate purposes. The expected use of net proceeds from this offering represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our development, feedback from regulatory authorities, the status of and results from clinical trials, as well as any collaborations that we may enter into with third parties for our drug candidates, and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering. 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 net proceeds.

Pending use of the proceeds as described above, we intend to invest the proceeds in a variety of capital preservation investments, including short-term, interest-bearing instruments, investment-grade and U.S. government securities.

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DILUTION

If you invest in this offering, your ownership interest will be diluted immediately to the extent of the difference between the public offering price per share and theas-adjusted net tangible book value per share of our common stock after giving effect to this offering. We calculate net tangible book value per share by dividing the net tangible book value, which is tangible assets less total liabilities, by the number of outstanding shares of our common stock. Dilution represents the difference between the portion of the amount per share paid by purchasers of shares in this offering and the as adjusted net tangible book value per share of our common stock immediately after giving effect to this offering. Our net tangible book value as of June 30, 2018 was approximately $30.7 million, or $2.33 per share.

After giving effect to the sale of our common stock pursuant to this prospectus supplement and accompanying prospectus in the aggregate amount of $35.0 million at an offering price of $12.50 per share, and after deducting commissions and estimated aggregate offering expenses payable by us, our net tangible book value as of June 30, 2018 would have been $65.6 million, or $4.06 per share of common stock. This represents an immediate increase in the net tangible book value of $1.73 per share to our existing stockholders and an immediate dilution in net tangible book value of $8.44 per share to new investors. The following table illustrates this per share dilution:

Offering price per share			$	12.50
Net tangible book value per share as of June 30, 2018	$	2.33
Increase per share attributable to new investors	$	1.73
As adjusted net tangible book value per share as of June 30, 2018 after giving effect to this offering			$	4.06
Dilution per share to new investors purchasing shares in this offering			$	8.44

If the underwriters exercise their option to purchase 450,000 additional shares of our common stock in full at the public offering price of $12.50 per share, the net tangible book value per share after giving effect to the offering would be $4.26 per share. This represents an immediate increase in as adjusted net tangible book value of $1.93 per share to existing stockholders and an immediate dilution in net tangible book value of $8.24 per share to new investors purchasing shares of our common stock in this offering.

The above discussion and table are based on 13,182,567 shares of our common stock issued and outstanding as of June 30, 2018 and excludes the following:

∎ 1,338,565 shares of our common stock issuable upon the exercise of stock options outstanding as of June 30, 2018, at a weighted-average exercise price of $11.21 per share;

∎ 1,787,124 shares of our common stock issuable upon the exercise of warrants outstanding as of June 30, 2018, at a weighted-average exercise price of $11.22 per share; and

∎ 956,290 shares of common stock available for future issuance under our Amended and Restated 2015 Stock Incentive Plan as of June 30, 2018.

To the extent that any options or warrants are exercised, new equity awards are granted under our equity incentive plans or we otherwise issue additional shares of common stock in the future, there will be further dilution to new investors.

In addition, we may choose to raise additional capital due to market conditions or strategic considerations, even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

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PRICE RANGE OF OUR COMMON STOCK

Our common stock began trading on The Nasdaq Capital Market on May 6, 2016 under the symbol “SBPH.” Prior to that time, there was no established public trading market for our common stock. The following table sets forth the high and low sale prices per share for our common stock on The Nasdaq Capital Market for the quarterly periods indicated:

	HIGH		LOW
Year ended December 31, 2016
First Quarter		N/A		N/A
Second Quarter (1)	$	11.75	$	8.77
Third Quarter	$	13.25	$	7.62
Fourth Quarter	$	12.49	$	7.14
Year ending December 31, 2017
First Quarter	$	11.71	$	6.31
Second Quarter	$	16.51	$	7.95
Third Quarter	$	16.97	$	11.25
Fourth Quarter	$	18.93	$	11.56
Year ending December 31, 2018
First Quarter	$	15.95	$	10.81
Second Quarter	$	15.57	$	11.62
Third Quarter (through August 8, 2018)	$	15.00	$	10.92

(1) Represents the period from May 6, 2016, the date on which our common stock first began to trade on the Nasdaq Capital Market after the pricing of our initial public offering, through June 30, 2016, the end of our second fiscal quarter.

On August 8, 2018, the last reported sale price of our common stock on The Nasdaq Capital Market was $14.10 per share. As of August 7, 2018, there were 86 holders of record of our common stock. The actual number of stockholders is greater than this number of record holders and includes stockholders who are beneficial owners, but whose shares are held in street name by brokers and other nominees. This number of holders of record also does not include stockholders whose shares may be held in trust by other entities.

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DIVIDEND POLICY

We have not declared or paid any cash dividends on our capital stock since our inception. We currently intend to retain future earnings, if any, to finance the operation and expansion of our business and do not anticipate paying any cash dividends 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 current or future financing instruments, provisions of applicable law and other factors the board deems relevant.

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MATERIAL U.S. FEDERAL TAX CONSIDERATIONS

The following is a discussion of material U.S. federal income and estate tax considerations applicable tonon-U.S. holders with respect to their ownership and disposition of shares of our common stock. This discussion is for information only and is not tax advice. Accordingly, all prospectivenon-U.S. holders of our common stock should consult their own tax advisors with respect to the U.S. federal, state, local andnon-U.S. tax consequences of the purchase, ownership and disposition of our common stock. For purposes of this discussion, anon-U.S. holder means a beneficial owner (other than a partnership or other pass-through entity) of our common stock who is not, for U.S. federal income tax purposes:

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

∎ a corporation, or other entity treated as a corporation for U.S. federal income tax purposes, created or organized in the United States or under the laws of the United States or of 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 if (1) a U.S. court is able to exercise primary supervision over the trust’s administration and one or more U.S. persons have the authority to control all of the trust’s substantial decisions or (2) the trust has a valid election in effect under applicable U.S. Treasury Regulations to be treated as a U.S. person.

This discussion is based on current provisions of the Code, existing and proposed U.S. Treasury Regulations promulgated thereunder, current administrative rulings and judicial decisions, all as in effect as of the date of this prospectus supplement, all of which are subject to change or to differing interpretation, possibly with retroactive effect. Any change could alter the tax consequences tonon-U.S. holders described in this prospectus supplement. In addition, there can be no assurance that the Internal Revenue Service, which we refer to as the IRS, will not challenge one or more of the tax consequences described herein. We assume in this discussion that anon-U.S. holder holds 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 aspects of U.S. federal income and estate taxation that may be relevant to a particularnon-U.S. holder in light of thatnon-U.S. holder’s individual circumstances nor does it address the alternative minimum tax, the Medicare tax on net investment income, or any aspects of U.S. state, local ornon-U.S. taxes. This discussion also does not consider any specific facts or circumstances that may apply to anon-U.S. holder and does not address the special tax rules applicable to particularnon-U.S. holders, such as:

∎ banks, insurance companies or other financial institutions;

∎ tax-exempt organizations;

∎ brokers or dealers in securities or currencies;

∎ pension plans;

∎ controlled foreign corporations;

∎ passive foreign investment companies;

∎ owners that have elected to mark securities to market or that hold our common stock as part of a straddle, hedge, conversion transaction, synthetic security or other integrated investment;

∎ persons deemed to sell our stock under a constructive sale provision of the Code;

∎ holders who have acquired our common stock through the exercise of a stock option or otherwise as compensation; and

∎ certain U.S. expatriates.

In addition, this discussion does not address the tax treatment of partnerships or persons who hold our common stock through partnerships or other entities or arrangements that are treated as pass-through entities for U.S. federal income tax purposes. A partner in a partnership or other pass-through entity that will hold our common stock should consult his, her or its own tax advisor regarding the tax consequences of acquiring, holding and disposing of our common stock through a partnership or other pass-through entity, as applicable.

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Distributions on Our Common Stock

Distributions on our common stock generally 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. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as atax-free return of thenon-U.S. holder’s investment, up to such holder’s tax basis in the common stock. Any remaining excess will be treated as capital gain, subject to the tax treatment described below in “Gain on Sale, Exchange or Other Taxable Disposition of Our Common Stock.” Any such distributions will also be subject to the discussion below under the section titled “Withholding and Information Reporting Requirements—FATCA.”

Subject to the discussion below on effectively connected income, dividends paid to anon-U.S. holder generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence. Anon-U.S. holder of our common stock who claims the benefit of an applicable income tax treaty between the United States and such holder’s country of residence generally will be required to provide a properly executed IRS FormW-8BEN orW-8BEN-E (or successor form) and satisfy applicable certification and other requirements. Anon-U.S. holder that is eligible for a reduced rate of U.S. withholding tax under an income tax treaty may be able to obtain a refund or credit of any excess amounts withheld by timely filing the required information with the IRS.Non-U.S. holders are urged to consult their tax advisors regarding their entitlement to benefits under an applicable income tax treaty.

Dividends that are treated as effectively connected with a trade or business conducted by anon-U.S. holder within the United States and, if an applicable income tax treaty so provides, that are attributable to a permanent establishment or a fixed base maintained by thenon-U.S. holder within the United States, are generally exempt from the 30% withholding tax if thenon-U.S. holder satisfies applicable certification and disclosure requirements. However, such U.S. effectively connected income, net of specified deductions and credits, is generally taxed at the same graduated U.S. federal income tax rates applicable to United States persons (as defined in the Code). Any U.S. effectively connected income received by anon-U.S. holder that is a corporation may also, under certain circumstances, be subject to an additional “branch profits tax” at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence.

Gain on Sale, Exchange or Other Taxable Disposition of Our Common Stock

Subject to the discussion below under “Withholding and Information Reporting Requirements—FATCA,” in general, anon-U.S. holder will not be subject to any U.S. federal income tax on any gain realized upon such holder’s sale, exchange or other taxable disposition of shares of our common stock unless:

∎ the gain is effectively connected with thenon-U.S. holder’s conduct of a U.S. trade or business and, if an applicable income tax treaty so provides, is attributable to a permanent establishment or a fixed base maintained by suchnon-U.S. holder in the United States, in which case thenon-U.S. holder generally will be taxed at the graduated U.S. federal income tax rates applicable to United States persons (as defined in the Code) and, if thenon-U.S. holder is a foreign corporation, the branch profits tax described above in “Distributions on Our Common Stock” also may apply;

∎ thenon-U.S. holder is a nonresident alien individual who is present in the United States for 183 days or more in the taxable year of the disposition and certain other conditions are met, in which case thenon-U.S. holder will be subject to a 30% tax (or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence) on the net gain derived from the disposition, which may be offset by certain U.S. source capital losses of thenon-U.S. holder, if any; or

∎ we are, or have been, at any time during the five-year period preceding such disposition (or thenon-U.S. holder’s holding period, if shorter) a “U.S. real property holding corporation,” unless our common stock is regularly traded on an established securities market and thenon-U.S. holder holds no more than 5% of our outstanding common stock, directly or indirectly, during the shorter of the5-year period ending on the date of the disposition or the period that thenon-U.S. holder held our common stock. If we are determined to be a U.S. real property holding corporation and the foregoing exception does not apply, then thenon-U.S. holder generally will be taxed on its net gain derived from the disposition at the graduated U.S. federal income tax rates applicable to United States persons (as defined in the Code). Generally, a corporation is a

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U.S. real property holding corporation only if the fair market value of its U.S. real property interests equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other assets used or held for use in a trade or business. Although there can be no assurance, we do not believe that we are, or have been, a U.S. real property holding corporation, or that we are likely to become one in the future. No assurance can be provided that our common stock will be regularly traded on an established securities market for purposes of the rules described above.

Backup Withholding and Information Reporting

We must report annually to the IRS and to eachnon-U.S. holder the gross amount of the distributions on our common stock paid to such holder and the tax withheld, if any, with respect to such distributions.Non-U.S. holders may have to comply with specific certification procedures to establish that the holder is not a United States person (as defined in the Code) in order to avoid backup withholding at the applicable rate with respect to dividends on our common stock. Generally, anon-U.S. holder will comply with such procedures if it provides a properly executed IRS FormW-8BEN orW-8BEN-E (or other applicable FormW-8) or otherwise meets documentary evidence requirements for establishing that it is anon-U.S. holder, or otherwise establishes an exemption. Dividends paid tonon-U.S. holders subject to withholding of U.S. federal income tax, as described above in “Distributions on Our Common Stock,” generally will be exempt from U.S. backup withholding.

Information reporting and backup withholding will generally apply to the proceeds of a disposition of our common stock by anon-U.S. holder effected by or through the U.S. office of any broker, U.S. or foreign, unless the holder certifies its status as anon-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to anon-U.S. holder where the transaction is effected outside the United States through anon-U.S. office of a broker. However, for information reporting purposes, dispositions effected through anon-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker.Non-U.S. holders should consult their own tax advisors regarding the application of the information reporting and backup withholding rules to them.

Copies of information returns that are filed with the IRS may be made available to the tax authorities of the country in which thenon-U.S. holder resides or is incorporated under the provisions of a specific treaty or agreement.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to anon-U.S. holder can be refunded or credited against thenon-U.S. holder’s U.S. federal income tax liability, if any, provided that an appropriate claim is timely filed with the IRS.

Withholding and Information Reporting Requirements—FATCA

Sections 1471 to 1474 of the Code (referred to as the Foreign Account Tax Compliance Act, or FATCA) generally impose a U.S. federal withholding tax at a rate of 30% on payments of dividends on, and, after December 31, 2018, gross proceeds from the sale or other disposition of, our common stock paid to certain foreign entities, unless (i) if the foreign entity is a “foreign financial institution,” such foreign entity undertakes certain due diligence, reporting, withholding, and certification obligations, (ii) if the foreign entity is not a “foreign financial institution,” such foreign entity identifies certain of its U.S. investors, if any, or (iii) the foreign entity is otherwise exempt under FATCA. If the payee is a foreign financial institution and is subject to the diligence, reporting, withholding, and certification requirements in (i) 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 tonon-compliant foreign financial institutions and certain other account holders. An intergovernmental agreement between the United States and an applicable foreign country may modify the FATCA rules described above.Non-U.S. holders should consult their own tax advisors regarding the possible implications of FATCA onnon-U.S. holders’ investment in our common stock and the entities (including financial intermediaries) through which they hold our common stock.

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U.S. Federal Estate Tax

Shares of our common stock that are owned or treated as owned at the time of death by an individual who is not a citizen or resident of the United States, as specifically defined for U.S. federal estate tax purposes, are considered U.S. situs assets and will be included in the individual’s gross estate for U.S. federal estate tax purposes. Such shares, therefore, may be subject to U.S. federal estate tax, unless an applicable estate tax or other treaty provides otherwise.

The preceding discussion of material U.S. federal tax considerations is for information only. It is not tax advice. Prospective investors should consult their own tax advisors regarding the particular U.S. federal, state, local andnon-U.S. tax consequences of purchasing, owning, and disposing of our common stock, including the consequences of any proposed changes in applicable laws.

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UNDERWRITING

Subject to the terms and conditions set forth in the underwriting agreement among us and Jefferies LLC and Piper Jaffray & Co., as the representatives of the underwriters named below and the joint book-running managers of this offering, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the respective number of shares of common stock shown opposite its name below:

UNDERWRITER	NUMBER OF SHARES
Jefferies LLC		1,612,500
Piper Jaffray & Co.		1,387,500
Total		3,000,000

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

The underwriters have advised us that, following the completion of this offering, they currently intend to make a market in the common stock as permitted by applicable laws and regulations. However, the underwriters are not obligated to do so, and the underwriters may discontinue any market-making activities at any time without notice in their sole discretion. Accordingly, no assurance can be given as to the liquidity of the trading market for the common stock, that you will be able to sell any of the common stock held by you at a particular time or that the prices that you receive when you sell will be favorable.

The underwriters are offering the shares of common stock subject to their acceptance of the shares of common stock from us and subject to prior sale. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commission and Expenses

The underwriters have advised us that they propose to offer the shares of common stock to the public at the public offering price set forth on the cover page of this prospectus and to certain dealers, which may include the underwriters, at that price less a concession not in excess of $0.45 per share of common stock. After the offering, the public offering price, concession and reallowance to dealers may be reduced by the representatives. No such reduction will change the amount of proceeds to be received by us as set forth on the cover page of this prospectus.

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The following table shows the public offering price, the underwriting discounts and commissions that we are to pay the underwriters and the proceeds, before expenses, to us in connection with this offering. Such amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase additional shares.

	PER SHARE				TOTAL
	WITHOUT OPTION TO PURCHASE ADDITIONAL SHARES		WITH OPTION TO PURCHASE ADDITIONAL SHARES		WITHOUT OPTION TO PURCHASE ADDITIONAL SHARES		WITH OPTION TO PURCHASE ADDITIONAL SHARES
Public offering price	$	12.50	$	12.50	$	37,500,000	$	43,125,000
Underwriting discounts and commissions paid by us	$	0.75	$	0.75	$	2,250,000	$	2,587,500
Proceeds to us, before expenses	$	11.75	$	11.75	$	35,250,000	$	40,537,500

We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $250,000. We have also agreed to reimburse the underwriters for certain of their expenses in an amount up to $25,000.

Listing

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

Stamp Taxes

If you purchase shares of common stock offered in this prospectus, 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.

Option to Purchase Additional Shares

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus, to purchase, from time to time, in whole or in part, up to an aggregate of 450,000 shares from us at the public offering price set forth on the cover page of this prospectus, less underwriting discounts and commissions. If the underwriters exercise this option, each underwriter will be obligated, subject to specified conditions, to purchase a number of additional shares proportionate to that underwriter’s initial purchase commitment as indicated in the table above.

No Sales of Similar Securities

We, our executive officers and our directors have agreed, subject to specified exceptions, not to directly or indirectly:

∎ lend, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock or any securities convertible into or exercisable or exchangeable for our common stock,

∎ enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of our common stock or such other securities,

∎ or make any demand for or exercise any right with respect to the registration of any shares of our common stock or any security convertible into or exercisable or exchangeable for our common stock

for a period of 90 days after the date of this prospectus without the prior written consent of Jefferies LLC and Piper Jaffray & Co.

This restriction terminates after the close of trading of the common stock on and including the 90^th day after the date of this prospectus.

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Jefferies LLC and Piper Jaffray & Co. may, in their sole discretion and at any time or from time to time before the termination of the90-day period, release all or any portion of the securities subject tolock-up agreements.

Stabilization

The underwriters have advised us that they, pursuant to Regulation M under the Securities Exchange Act of 1934, as amended, certain persons participating in the offering may engage in short sale transactions, stabilizing transactions, syndicate covering 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 the 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 underwriters’ option to purchase additional shares of our common stock in this offering. The underwriters 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 underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they 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 underwriters 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 underwriters are 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.

A stabilizing bid is a bid for the purchase of shares of common stock on behalf of the underwriters for the purpose of fixing or maintaining the price of the common stock. A syndicate covering transaction is the bid for or the purchase of shares of common stock on behalf of the underwriters to reduce a short position incurred by the underwriters in connection with the offering. Similar to other purchase transactions, the underwriter’s purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our common stock or preventing or retarding a decline in the market price of our 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. A penalty bid is an arrangement permitting the underwriters to reclaim the selling concession otherwise accruing to a syndicate member in connection with the offering if the common stock originally sold by such syndicate member are purchased in a syndicate covering transaction and therefore have not been effectively placed by such syndicate member.

Neither we, nor any of the underwriters 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. The underwriters are not obligated to engage in these activities and, if commenced, any of the activities may be discontinued at any time.

Electronic Distribution

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

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Other Activities and Relationships

The underwriters and certain of their 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. The underwriters and certain of their 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 they received or will receive customary fees and expenses.

In the ordinary course of their various business activities, the underwriters and certain of their 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 the underwriters or their respective affiliates have a lending relationship with us, they routinely hedge their credit exposure to us consistent with their customary risk management policies. The underwriters and their 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 common stock offered hereby. Any such short positions could adversely affect future trading prices of the common stock offered hereby. The underwriters and certain of their respective 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.

Selling Restrictions

Notice to Canadian Residents

Resale Restrictions

The distribution of the shares of common stock in Canada is being made only in the provinces of Ontario, Quebec, Alberta and British Columbia on a private placement basis exempt from the requirement that we prepare and file a prospectus with the securities regulatory authorities in each province where trades of these securities are made. Any resale of the shares of common stock in Canada must be made under applicable securities laws which may vary depending on the relevant jurisdiction, and which may require resales to be made under available statutory exemptions or under a discretionary exemption granted by the applicable Canadian securities regulatory authority. Purchasers are advised to seek legal advice prior to any resale of the securities.

Representations of Canadian Purchasers

By purchasing the shares of common stock in Canada and accepting delivery of a purchase confirmation, a purchaser is representing to us, the selling stockholders and the dealer from whom the purchase confirmation is received that:

∎ the purchaser is entitled under applicable provincial securities laws to purchase the shares of common stock without the benefit of a prospectus qualified under those securities laws as it is an “accredited investor” as defined under National Instrument45-106—Prospectus Exemptions,

∎ the purchaser is a “permitted client” as defined in National Instrument31-103—Registration Requirements, Exemptions and Ongoing Registrant Obligations,

∎ where required by law, the purchaser is purchasing as principal and not as agent, and

∎ the purchaser has reviewed the text above under Resale Restrictions.

Conflicts of Interest

Canadian purchasers are hereby notified that the underwriter is relying on the exemption set out in section 3A.3 or 3A.4, if applicable, of National Instrument33-105—Underwriting Conflictsfrom having to provide certain conflict of interest disclosure in this document.

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Statutory Rights of Action

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if the offering memorandum (including any amendment thereto) such as this document 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 of these securities in Canada 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.

Enforcement of Legal Rights

All of our directors and officers as well as the experts named herein may be located outside of Canada and, as a result, it may not be possible for Canadian purchasers to effect service of process within Canada upon us or those persons. All or a substantial portion of our assets and the assets of those persons may be located outside of Canada and, as a result, it may not be possible to satisfy a judgment against us or those persons in Canada or to enforce a judgment obtained in Canadian courts against us or those persons outside of Canada.

Taxation and Eligibility for Investment

Canadian purchasers of the shares of common stock should consult their own legal and tax advisors with respect to the tax consequences of an investment in the shares of common stock in their particular circumstances and about the eligibility of the shares of common stock for investment by the purchaser under relevant Canadian legislation.

Notice to Investors in the European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a Relevant Member State) an offer to the public of any shares of our common stock has not been made and may not be made in that Relevant Member State prior to the publication of a prospectus in relation to the shares of our common stock which has been approved by the competent authority in that Relevant Member State or, where appropriate, approved in another Relevant Member State and notified to the competent authority in that Relevant Member State, all in accordance with the Prospectus Directive, except that an offer to the public in that Relevant Member State of any shares of our common stock may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that Relevant Member State:

(a) to any legal entity which is a qualified investor as defined in the Prospectus Directive;

(b) to fewer than 100, or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the underwriter for any such offer; or

(c) in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of shares of our common stock shall result in a requirement for the publication by us or the underwriter of a prospectus pursuant to Article 3 of the Prospectus Directive or a supplemental prospectus pursuant to Article 16 of the Prospectus Directive or any measure implementing the Prospectus Directive in a Relevant Member State and each person who initially acquires any shares of our common stock or to whom any offer is made will be deemed to have represented, acknowledged and agreed with the underwriter and us that it is a qualified investor within the meaning of the law of the Relevant Member State implementing Article 2(1)(e) of the Prospectus Directive or any measure implementing the Prospectus Directive in any Relevant Member State.

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of our common stock in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares of our common stock to be offered so as to enable an investor to decide to purchase any shares of our common stock, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State. The expression “Prospectus Directive” means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and includes any relevant implementing measure in the Relevant Member State, and the expression “2010 PD Amending Directive” means Directive 2010/73/EU.

In the case of any shares of our common stock being offered to a financial intermediary as that term is used in Article 3(2) of the Prospectus Directive, such financial intermediary will also be deemed to have represented,

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acknowledged and agreed that the shares of our common stock acquired by it in the offer have not been acquired on anon-discretionary basis on behalf of, nor have they been acquired with a view to their offer or resale to persons in circumstances which may give rise to an offer of any shares of our common stock to the public other than their offer or resale in a Relevant Member State to qualified investors as so defined or in circumstances in which the prior consent of the underwriter has been obtained to each such proposed offer or resale. We, the underwriter and its affiliates, and others will rely upon the truth and accuracy of the foregoing representations, acknowledgements and agreements. Notwithstanding the above, a person who is not a qualified investor and who has notified the underwriter of such fact in writing may, with the prior consent of the underwriter, be permitted to acquire shares of our common stock in the offer.

Notice to Investors in the United Kingdom

The underwriters:

∎ have only communicated or caused to be communicated and will only communicate or cause to be communicated any invitation or inducement to engage in investment activity (within the meaning of section 21 of Financial Services and Markets Act 2000, as amended, or the FSMA) in connection with the sale or issue of common stock in circumstances in which section 21 of FSMA does not apply to such underwriter; and

∎ have complied with, and will comply with all applicable provisions of FSMA with respect to anything done by it in relation to the shares of common stock in, from, or otherwise involving the United Kingdom.

This prospectus is directed solely at persons (i) who are outside the United Kingdom or (ii) in the United Kingdom, who: (A) have professional experience in matters relating to investments and who fall within the definition of “investment professionals” in Article 19(5) of the Financial Services and Markets Act (Financial Promotion) Order 2005, or the Order, (B) are high net worth entities and other persons falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). Accordingly, by accepting delivery of this prospectus, the recipient warrants and acknowledges that it is such a relevant person.

This prospectus must not be acted on or relied on by persons who are not relevant persons. Any investment or investment activity to which this prospectus relates is available only to relevant persons and will be engaged in with relevant persons only.

Notice to Investors in Switzerland

This document is not intended to constitute an offer or solicitation to purchase or invest in the shares described herein. The shares may not be publicly offered, sold or advertised, directly or indirectly, in, into or from Switzerland and will not be listed on the SIX Swiss Exchange or on any other exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the shares constitutes a prospectus as such term is understood pursuant to article 652a or article 1156 of the Swiss Code of Obligations or a listing prospectus within the meaning of the listing rules of the SIX Swiss Exchange or any other regulated trading facility in Switzerland, and neither this document nor any other offering or marketing material relating to the shares may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, nor the Company nor the shares have been or will be filed with or approved by any Swiss regulatory authority. The shares are not subject to the supervision by any Swiss regulatory authority, e.g., the Swiss Financial Markets Supervisory Authority FINMA, or FINMA, and investors in the shares will not benefit from protection or supervision by such authority.

Notice to Investors in Australia

This prospectus is not a disclosure document for the purposes of Australia’s Corporations Act 2001 (Cth) of Australia, or Corporations Act, has not been lodged with the Australian Securities & Investments Commission and is only directed to the categories of exempt persons set out below. Accordingly, if you receive this prospectus in Australia:

You confirm and warrant that you are either:

∎ a “sophisticated investor” under section 708(8)(a) or (b) of the Corporations Act;

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∎ a “sophisticated investor” under section 708(8)(c) or (d) of the Corporations Act and that you have provided an accountant’s certificate to the company which complies with the requirements of section 708(8)(c)(i) or (ii) of the Corporations Act and related regulations before the offer has been made; or

∎ a “professional investor” within the meaning of section 708(11)(a) or (b) of the Corporations Act.

To the extent that you are unable to confirm or warrant that you are an exempt sophisticated investor or professional investor under the Corporations Act any offer made to you under this prospectus is void and incapable of acceptance.

You warrant and agree that you will not offer any of the shares issued to you pursuant to this prospectus for resale in Australia within 12 months of those securities being issued unless any such resale offer is exempt from the requirement to issue a disclosure document under section 708 of the Corporations Act.

Notice to Investors in Hong Kong

No securities have been offered or sold, and no securities may be offered or sold, in Hong Kong, by means of any document, other than to persons whose ordinary business is to buy or sell shares or debentures, whether as principal or agent; or to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32) of Hong Kong. No document, invitation or advertisement relating to the securities has been issued or may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted under the securities laws of Hong Kong) other than with respect to securities which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance.

This prospectus has not been registered with the Registrar of Companies in Hong Kong. Accordingly, this prospectus may not be issued, circulated or distributed in Hong Kong, and the securities may not be offered for subscription to members of the public in Hong Kong. Each person acquiring the securities will be required, and is deemed by the acquisition of the securities, to confirm that he is aware of the restriction on offers of the securities described in this prospectus and the relevant offering documents and that he is not acquiring, and has not been offered any securities in circumstances that contravene any such restrictions.

Notice to Investors in Singapore

This prospectus has not been and will not be lodged or registered with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or the invitation for subscription or purchase of the securities may not be issued, circulated or distributed, nor may the securities be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to the public or any member of the public in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore, or the SFA, (ii) to a relevant person as defined under Section 275(2), or any person pursuant to Section 275(1A) of the SFA, and in accordance with the conditions, specified in Section 275 of the SFA, or (iii) otherwise pursuant to, and in accordance with the conditions of any other applicable provision of the SFA.

Where the securities are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

∎ a corporation (which is not an accredited investor as defined under Section 4A of the SFA) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

∎ a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary is an accredited investor,

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shares, debentures and units of shares and debentures of that corporation or the beneficiaries’ rights and interest in that trust shall not be transferable for six months after that corporation or that trust has acquired the Offer Shares under Section 275 of the SFA except:

∎ to an institutional investor under Section 274 of the SFA or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than $200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets, and further for corporations, in accordance with the conditions, specified in Section 275 of the SFA;

∎ where no consideration is given for the transfer; or

∎ where the transfer is by operation of law.

Notice to Investors in Japan

The offering has not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948 of Japan, as amended), or FIEL, and the underwriters will not offer or sell any securities, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan), or to others forre-offering or resale, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the FIEL and any other applicable laws, regulations and ministerial guidelines of Japan.

Notice to Investors in Israel

This document does not constitute a prospectus under the Israeli Securities Law, 5728-1968, or the Securities Law, and has not been filed with or approved by the Israel Securities Authority. In the State of Israel, this document is being distributed only to, and is directed only at, and any offer of the shares is directed only at, investors listed in the first addendum, or the Addendum, to the Israeli Securities Law, consisting primarily of joint investment in trust funds, provident funds, insurance companies, banks, portfolio managers, investment advisors, members of the Tel Aviv Stock Exchange, underwriters, venture capital funds, entities with equity in excess of NIS 50 million and “qualified individuals”, each as defined in the Addendum (as it may be amended from time to time), collectively referred to as qualified investors (in each case purchasing for their own account or, where permitted under the Addendum, for the accounts of their clients who are investors listed in the Addendum). Qualified investors will be required to submit written confirmation that they fall within the scope of the Addendum, are aware of the meaning of same and agree to it.

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LEGAL MATTERS

The validity of the shares of common stock offered hereby will be passed upon for us by Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts. The underwriters are being represented in connection with this offering by Latham  & Watkins LLP, Chicago, Illinois.

EXPERTS

The consolidated financial statements of Spring Bank Pharmaceuticals, Inc. and its subsidiaries as of December 31, 2017 and 2016 and for each of the years in thetwo-year period ended December 31, 2017 incorporated in this prospectus by reference from the Spring Bank Pharmaceuticals, Inc. Annual Report on Form10-K for the year ended December 31, 2017 have been audited by RSM US LLP, an independent registered public accounting firm, as stated in their report thereon incorporated herein by reference, and have been incorporated in this prospectus and registration statement in reliance upon such report and upon the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the reporting requirements of the Exchange Act and file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy these reports, proxy statements and other information at the SEC’s public reference facilities at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at1-800-SEC-0330 for more information about the operation of the public reference facilities. SEC filings are also available at the SEC’s web site athttp://www.sec.gov.

We also maintain a website atwww.springbankpharm.com, through which you can access our SEC filings. The information set forth on our website is not part of this prospectus supplement or the accompanying prospectus.

This prospectus supplement is part of a registration statement we filed with the SEC. This prospectus supplement and the accompanying prospectus omit some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information on us and our consolidated subsidiaries and the securities we are offering. Statements in this prospectus supplement and the accompanying prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings. You should review the complete document to evaluate these statements. You can obtain a copy of the registration statement from the SEC at the address listed above or from the SEC’s website.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference in this prospectus supplement and the accompanying prospectus much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus supplement and the accompanying prospectus is considered to be part of this prospectus supplement and the accompanying prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus supplement and the accompanying prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus supplement and the accompanying prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus supplement, the accompanying prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus supplement and the accompanying prospectus incorporate by reference the documents listed below (FileNo. 001-37718) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) until the offering of the securities under the registration statement is terminated or completed:

∎ our Annual Report on Form10-K for the year ended December 31, 2017 filed with the SEC on February 20, 2018;

∎ our Quarterly Reports on Form10-Q for the quarters ended (i) March 31, 2018 filed with the SEC on April 27, 2018, as amended by our Amended Quarterly Report on Form10-Q/A filed with the SEC on May 4, 2018, and (ii) June 30, 2018 filed with the SEC on August 2, 2018;

∎ the portions of our definitive proxy statement on Schedule 14A filed with the SEC on April 27, 2018 that are deemed “filed” with the SEC under the Exchange Act;

∎ our Current Reports on Form8-K filed with the SEC on March 5, 2018, March 14, 2018, April 10, 2018 and June 19, 2018;

∎ the description of our common stock contained in our Registration Statement on Form8-A filed on March 14, 2016, including any amendments or reports filed for the purpose of updating such description; and

∎ all reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act after the date of this prospectus and prior to the termination or completion of the offering of securities under this prospectus shall be deemed to be incorporated by reference in this prospectus and to be a part hereof from the date of filing such reports and other documents.

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or phone number:

Spring Bank Pharmaceuticals, Inc.

35 Parkwood Drive, Suite 210

Hopkinton, Massachusetts 01748

Attention: Corporate Secretary

Telephone: (508)473-5993

You may also access these documents on our website,http://www.springbankpharm.com. The information contained on, or that can be accessed through, our website is not a part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

You should rely only on information contained in, or incorporated by reference into, this prospectus and any prospectus supplement. We have not authorized anyone to provide you with information different from that contained in this prospectus or incorporated by reference in this prospectus. We are not making offers to sell the securities in any jurisdiction in which such an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such offer or solicitation.

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PROSPECTUS

$150,000,000

COMMON STOCK

PREFERRED STOCK

DEBT SECURITIES

WARRANTS

RIGHTS

PURCHASE CONTRACTS

UNITS

This prospectus will allow us to issue, from time to time at prices and on terms to be determined at or prior to the time of the offering, up to $150,000,000 of any combination of the securities described in this prospectus, either individually or in units. We may also offer common stock or preferred stock upon conversion of or exchange for the debt securities; common stock upon conversion of or exchange for the preferred stock; common stock, preferred stock or debt securities upon the exercise of warrants, rights or performance of purchase contracts; or any combination of these securities upon the performance of purchase contracts.

This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. We will provide you with the specific terms of any offering in one or more supplements to this prospectus. The prospectus supplements will also describe the specific manner in which these securities will be offered and may also supplement, update or amend information contained in this document. You should read this prospectus and any prospectus supplement, as well as any documents incorporated by reference into this prospectus or any prospectus supplement, carefully before you invest.

Our securities may be sold directly by us to you, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus and in the applicable prospectus supplement. If any underwriters or agents are involved in the sale of our securities with respect to which this prospectus is being delivered, the names of such underwriters or agents and any applicable fees, commissions or discounts and over- allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds that we expect to receive from such sale will also be set forth in a prospectus supplement.

Our common stock is listed on The NASDAQ Capital Market under the symbol “SBPH.” On May 31, 2017, the last reported sale price of our common stock was $12.41 per share. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on The NASDAQ Capital Market or any securities market or other securities exchange of the securities covered by the prospectus supplement. Prospective purchasers of our securities are urged to obtain current information as to the market prices of our securities, where applicable.

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks that we have described on page 6 of this prospectus under the caption “Risk Factors.” We may include specific risk factors in supplements to this prospectus under the caption “Risk Factors.” This prospectus may not be used to sell our securities unless accompanied by a prospectus supplement.

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

The date of this prospectus is June 12, 2017.

TABLE OF CONTENTS

	PAGE
ABOUT THIS PROSPECTUS		1
PROSPECTUS SUMMARY		2
RISK FACTORS		6
RATIO OF EARNINGS TO FIXED CHARGES		6
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		7
USE OF PROCEEDS		8
PLAN OF DISTRIBUTION		9
DESCRIPTION OF COMMON STOCK		11
DESCRIPTION OF PREFERRED STOCK		12
DESCRIPTION OF DEBT SECURITIES		13
DESCRIPTION OF WARRANTS		19
DESCRIPTION OF RIGHTS		20
DESCRIPTION OF PURCHASE CONTRACTS		22
DESCRIPTION OF UNITS		23
CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF INCORPORATION AND BYLAWS		24
LEGAL MATTERS		27
EXPERTS		27
WHERE YOU CAN FIND MORE INFORMATION		27
INCORPORATION OF DOCUMENTS BY REFERENCE		28

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. Under this shelf registration process, we may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants, rights or purchase contracts to purchase any of such securities, either individually or in units, in one or more offerings, with a total value of up to $150,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering.

This prospectus does not contain all of the information included in the registration statement. For a more complete understanding of the offering of the securities, you should refer to the registration statement, including its exhibits. The prospectus supplement may also add, update or change information contained or incorporated by reference in this prospectus. However, no prospectus supplement will offer a security that is not registered and described in this prospectus at the time of its effectiveness. This prospectus, together with the applicable prospectus supplements and the documents incorporated by reference into this prospectus, includes all material information relating to the offering of securities under this prospectus. You should carefully read this prospectus, the applicable prospectus supplement, the information and documents incorporated herein by reference and the additional information under the heading “Where You Can Find More Information” before making an investment decision.

You should rely only on the information we have provided or incorporated by reference in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with information different from that contained or incorporated by reference in this prospectus. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained or incorporated by reference in this prospectus. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus or any prospectus supplement is accurate only as of the date on the front of the document and that any information we have incorporated herein by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus or any sale of a security.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference in the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus may not be used to consummate sales of our securities, unless it is accompanied by a prospectus supplement. To the extent there are inconsistencies between any prospectus supplement, this prospectus and any documents incorporated by reference, the document with the most recent date will control.

Unless the context otherwise requires, “Spring Bank,” “SBPH,” “the Company,” “we,” “us,” “our” and similar terms refer to Spring Bank Pharmaceuticals, Inc. and our subsidiaries.

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PROSPECTUS SUMMARY

The following is a summary of what we believe to be the most important aspects of our business and the offering of our securities under this prospectus. We urge you to read this entire prospectus, including the more detailed consolidated financial statements, notes to the consolidated financial statements and other information incorporated by reference from our other filings with the SEC or included in any applicable prospectus supplement. Investing in our securities involves risks. Therefore, carefully consider the risk factors set forth in any prospectus supplements and in our most recent annual and quarterly filings with the SEC, as well as other information in this prospectus and any prospectus supplements and the documents incorporated by reference herein or therein, before purchasing our securities. Each of the risk factors could adversely affect our business, operating results and financial condition, as well as adversely affect the value of an investment in our securities.

About Spring Bank Pharmaceuticals

We are a clinical-stage biopharmaceutical company engaged in the discovery and development of a novel class of therapeutics using our proprietary small molecule nucleic acid hybrid, or SMNH, chemistry platform. Our SMNH compounds are small segments of nucleic acids that we design to selectively target and modulate the activity of specific proteins implicated in various disease states. We are developing our most advanced SMNH product candidate, SB 9200, for the treatment of certain viral diseases. We have designed SB 9200 to selectively activate within infected cells the cellular proteins, retinoic acid-inducible gene 1(RIG-I) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2), to inhibit viral replication and to cause the induction of intracellular interferon signaling pathways for antiviral defense. We believe that SB 9200 may play an important role in antiviral therapy by modulating the body’s immune response through its mechanisms of action to fight viral infections. We are also developing other SMNH product candidates, including SB 11285, an immunotherapeutic agent for the treatment of selected cancers through the activation of the STimulator of INterferon Genes, or STING, pathway.

SB 9200

We are currently developing SB 9200 for the treatment of chronic hepatitis B virus, or HBV. We are conducting a Phase 2a multi-center clinical trial of SB 9200 in Canada, Hong Kong, Korea and Taiwan. The trial is a randomized, placebo-controlled, multiple ascending dose trial in up to 80non-cirrhotic patients infected with chronic HBV using doses of 25 mg, 50 mg, 100 mg and 200 mg of SB 9200 as a monotherapy administered daily for 12 weeks. Following this treatment, all patients will receive treatment with the oral antiviral agent tenofovir disoproxil fumarate (marketed as Viread^®, which we refer to as Viread) as a monotherapy for 12 weeks. Patients will be sequentially enrolled into one of the four dose cohorts and randomized between a SB 9200 dose group or placebo on a 4:1 basis. Patients will be stratified based on HBeAg+/- status. HBeAg is anon-structural protein whose presence in blood, or HBeAg+, is indicative of actively replicating virus. The primary endpoints of the Phase 2a clinical trial are safety and reduction in HBV DNA frompre-treatment levels with multiple exploratory secondary endpoints, including reduction or loss of hepatitis B surface antigen, or HBsAg, and HBeAg, both of which are important markers of viral replication and early surrogate markers for functional cure. In June 2016, we initiated our Phase 2a ACHIEVE clinical trial innon-cirrhotic patients infected with chronic HBV, and in May 2017, we reportedtop-line results from the first SB 9200 monotherapy dosing cohort of the Phase 2a clinical trial, which indicated that a low dose (25mg) of SB 9200 alone showed a favorable safety profile and antiviral activity against HBV DNA and HBsAg.

We are also pursuing the development of theco-formulation of SB 9200 with entecavir (marketed as Baraclude^®, which we refer to as Baraclude) and Viread as potential fixed-dose combination products for the treatment of patients with chronic HBV who may benefit from the combined use of SB 9200 as an immunomodulatory agent, and Baraclude or Viread, as the antiviral agent. We anticipate that the fixed-dose combination product could result in enhanced patient compliance and potentially allow for the delivery of lower doses of the individual compounds for equivalent efficacy and a more favorable safety profile. We have

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conducted early development work onco-formulations with Baraclude and Viread and believe that SB 9200 and these antiviral agents are compatible in the same formulation. We believe that the immunomodulatory activity provided by SB 9200 could be a key component of a future combinatorial treatment of patients infected with chronic HBV, which could increase the percentage of chronic HBV patients who achieve a functional cure. We have entered into collaborations and seek to enter into additional collaborations with third parties that are investigating and/or developing compounds for the treatment of chronic HBV with different pharmacological mechanisms of action than SB 9200. Pursuant to this strategy, we entered into agreements with Arrowhead Pharmaceuticals, Inc. and Arbutus Biopharma Corporation.

SB 11285

We are developing SB 11285, a novel proprietary STING agonist, as a potential immunotherapeutic agent for the treatment of selected cancers. Recent published scientific literature indicates that the activation of the STING pathway can result in the induction of cellular interferons and cytokines and promote an aggressive and strong anti-tumor response through the induction of innate and adaptive immune response.In our studies performed inin vitro cancer models, SB 11285 was shown to cause the induction of interferon and other cytokines and cell death, or apoptosis, of multiple tumor-derived cell lines. We continue to conduct preclinical studies of SB 11285 in multiplein vivo cancer models. In March 2017, we presented data from certain of thesein vivo studies at the 2017 Keystone Symposia on Cancer Immunology and Immunotherapy indicating that SB 11285 showed anti-tumor activity in a 4T1 breast cancer syngeneic mouse model and an A20 lymphoma model.

Additional Information

For additional information related to our business and operations, please refer to the reports incorporated herein by reference, including our Annual Report on Form10-K for the year ended December 31, 2016, as described under the caption “Incorporation of Documents by Reference” on page 28 of this prospectus.

Risks Associated with Our Business

Our business is subject to numerous risks and uncertainties, including those highlighted in the section entitled “Risk Factors” immediately following this prospectus summary. Some of these risks are:

∎ we have a history of limited operations, have incurred significant losses since our inception, expect to incur losses for the foreseeable future and may never achieve or maintain profitability;

∎ we will need additional funding to complete the development of our product candidates and, if our products are approved by the FDA or other applicable regulatory authorities, before we can expect to become profitable from the commercial sale of our products. If we are unable to raise capital when needed, we could be forced to delay, reduce or eliminate our product development programs or commercialization efforts;

∎ our business currently depends substantially on the success of clinical trials for SB 9200, which is still under development. If we are unable to obtain regulatory approval for, or successfully commercialize SB 9200, our business will be materially harmed;

∎ we are very early in our development efforts and our product candidates may not be successful in later stage clinical trials. As a result, they may never be approved as marketable therapeutics;

∎ we rely, and expect to continue to rely, on third parties to conduct our clinical trials and to manufacture our product candidates for preclinical and clinical testing. These third parties may not perform satisfactorily, which could delay our product development activities;

∎ if we are unable to adequately protect our proprietary technology, or obtain and maintain issued patents which are sufficient to protect our product candidates, others could compete against us more directly, which would have a material adverse impact on our business, results of operations, financial condition and prospects; and

∎ we may not be able to retain key executives or to attract, retain and motivate key personnel.

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It is difficult to predict the time and cost of product candidate development and subsequently obtaining regulatory approval.

Our Corporate Information

We were incorporated under the laws of the Commonwealth of Massachusetts as Spring Bank Technologies, Inc. on October 7, 2002. On May 12, 2008, we filed a certificate of incorporation in the State of Delaware and changed our state of incorporation to Delaware and our name to Spring Bank Pharmaceuticals, Inc. Our principal executive offices are located at 86 South Street, Hopkinton, MA 01748, and our telephone number is(508) 473-5993. Our website address is www.springbankpharm.com. The information contained in, or accessible through, our website does not constitute a part of this prospectus.

All brand names or trademarks appearing in this prospectus are the property of their respective holders. Use or display by us of other parties’ trademarks, trade dress, or products in this prospectus is not intended to, and does not, imply a relationship with, or endorsements or sponsorship of, us by the trademark or trade dress owners.

Implications of Being an Emerging Growth Company

The Jumpstart Our Business Startups Act of 2012, or the JOBS Act, was enacted in April 2012 with the intention of encouraging capital formation in the United States and reducing the regulatory burden on newly public companies that qualify as “emerging growth companies.” We are an emerging growth company within the meaning of the JOBS Act. As an emerging growth company, we may take advantage of certain exemptions from various public reporting requirements, including the requirement that our internal control over financial reporting be audited by our independent registered public accounting firm pursuant to Section 404 of the Sarbanes-Oxley Act of 2002, certain requirements related to the disclosure of executive compensation in this prospectus and in our periodic reports and proxy statements, and the requirement that we hold a nonbinding advisory vote on executive compensation and any golden parachute payments. We may choose to take advantage of some, all or none of these reduced burdens until we are no longer an emerging growth company. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests. .

We will remain an emerging growth company until the earliest to occur of:

∎ the last day of the fiscal year in which we have approximately $1.0 billion or more in annual gross revenue;

∎ the date we qualify as a “large accelerated filer,” with at least $700 million of equity securities held bynon-affiliates;

∎ the date on which we have issued, in any three-year period, more than $1.0 billion innon-convertible debt securities; or

∎ the last day of the fiscal year ending after the fifth anniversary of the closing of our initial public offering.

Section 102(b)(1) of the JOBS Act exempts emerging growth companies from being required to comply with new or revised financial accounting standards until private companies (that is, those that have not had a registration statement under the Securities Act of 1933, as amended, or the Securities Act, declared effective or do not have a class of securities registered under the Securities Exchange Act of 1934, as amended, or the Exchange Act) are required to comply with the new or revised financial accounting standard. We have chosen to “opt out” of the extended transition periods available under the JOBS Act for complying with new or revised accounting standards. Section 107 of the JOBS Act provides that our decision to opt out of the extended transition periods for complying with new or revised accounting standards is irrevocable.

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Offerings Under This Prospectus

Under this prospectus, we may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants, rights or purchase contracts to purchase any of such securities, either individually or in units, with a total value of up to $150,000,000, from time to time at prices and on terms to be determined by market conditions at the time of the offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

∎ designation or classification;

∎ aggregate principal amount or aggregate offering price;

∎ maturity, if applicable;

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

∎ redemption, conversion or sinking fund terms, if any;

∎ voting or other rights, if any; and

∎ conversion or exercise prices, if any.

The prospectus supplement also may add, update or change information contained in this prospectus or in documents we have incorporated by reference into this prospectus. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

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

∎ the names of those agents or underwriters;

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

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

∎ the net proceeds to us.

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

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RISK FACTORS

Investing in our securities involves significant risk. The prospectus supplement applicable to each offering of our securities will contain a discussion of the risks applicable to an investment in Spring Bank. Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading “Risk Factors” in the applicable prospectus supplement, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus. You should also consider the risks, uncertainties and assumptions discussed under the heading “Risk Factors” included in our most recent annual report on Form10-K, as revised or supplemented by our subsequent quarterly reports on Form10-Q or our current reports on Form8-K that we have filed with the SEC, all of which are incorporated herein by reference, and which may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.

RATIO OF EARNINGS TO FIXED CHARGES

Any time debt securities or preferred securities are offered pursuant to this prospectus, we will provide a table setting forth our ratio of earnings to fixed charges, or combined fixed charges and preference dividends to earnings, if applicable, on a historical basis in the applicable prospectus supplement, if required.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains forward-looking statements. All statements other than statements of historical facts contained in this prospectus, including statements regarding our future results of operations and financial position, business strategy, product candidates, product approvals, research and development costs, timing and likelihood of success, plans and objectives of management for future operations and future results of anticipated products, are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions. The forward-looking statements in this prospectus are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this prospectus and are subject to a number of risks, uncertainties and assumptions described under the sections in our periodic report reports, including our Annual Report on Form10-K for the fiscal year ended December 31, 2016, entitled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as other sections elsewhere in this prospectus, any accompanying prospectus supplement and the documents or reports incorporated by reference in this prospectus.

Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, you should not rely on these forward-looking statements as predictions of future events. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise.

You should read this prospectus, any accompanying prospectus supplement, the documents that we reference in this prospectus and the documents we have filed as exhibits to the registration statement with the understanding that our actual future results may be materially different from what we expect. We qualify all of our forward-looking statements by these cautionary statements.

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USE OF PROCEEDS

Unless otherwise indicated in the applicable prospectus supplement, we intend to use any net proceeds from the sale of securities under this prospectus to fund activities relating to the development and commercialization of our product candidates, and for other general corporate purposes, including, but not limited to, working capital, capital expenditures, investments, acquisitions, should we choose to pursue any, and collaborations. We have not determined the amounts we plan to spend on any of the areas listed above or the timing of these expenditures. As a result, our management will have broad discretion to allocate the net proceeds, if any, we receive in connection with securities offered pursuant to this prospectus for any purpose. Pending application of the net proceeds as described above, we may initially invest the net proceeds in short-term, investment-grade, interest-bearing securities or apply them to the reduction of short-term indebtedness. Additional information on the use of proceeds from the sale of securities offered by this prospectus may be set forth in the prospectus supplement relating to that offering.

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PLAN OF DISTRIBUTION

We may offer securities under this prospectus from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods. We may sell the securities (1) through underwriters or dealers, (2) through agents or (3) directly to one or more purchasers, or through a combination of such methods. We may distribute the securities from time to time in one or more transactions at:

∎ a fixed price or prices, which may be changed from time to time;

∎ market prices prevailing at the time of sale;

∎ prices related to the prevailing market prices; or

∎ negotiated prices.

We may directly solicit offers to purchase the securities being offered by this prospectus. We may also designate agents to solicit offers to purchase the securities from time to time, and may enter into arrangements for“at-the-market,” equity line or similar transactions. We will name in a prospectus supplement any underwriter or agent involved in the offer or sale of the securities.

If we utilize a dealer in the sale of the securities being offered by this prospectus, we will sell the securities 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 we utilize an underwriter in the sale of the securities being offered by this prospectus, we will execute an underwriting agreement with the underwriter at the time of sale, and we will provide the name of any underwriter in the prospectus supplement which 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 the 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 the underwriter may compensate those dealers in the form of discounts, concessions or commissions.

With respect to underwritten public offerings, negotiated transactions and block trades, we will provide in the applicable prospectus supplement information regarding any compensation we pay 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. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of 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.

If so indicated in the applicable prospectus supplement, we will authorize underwriters, dealers or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in each applicable prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in each applicable prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:

∎ the purchase by an institution of the securities covered under that contract shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that institution is subject; and

∎ if the securities are also being sold to underwriters acting as principals for their own account, the underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

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One or more firms, referred to as “remarketing firms,” may also offer or sell the securities, if a prospectus supplement so indicates, in connection with a remarketing arrangement upon their purchase. Remarketing firms will act as principals for their own accounts or as our agents. These remarketing firms will offer or sell the securities in accordance with the terms of the securities. Each prospectus supplement will identify and describe any remarketing firm and the terms of its agreement, if any, with us and will describe the remarketing firm’s compensation. Remarketing firms may be deemed to be underwriters in connection with the securities they remarket. Remarketing firms may be entitled under agreements that may be entered into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

Certain underwriters may use this prospectus and any accompanying prospectus supplement for offers and sales related to market-making transactions in the securities. These underwriters may act as principal or agent in these transactions, and the sales will be made at prices related to prevailing market prices at the time of sale. Any underwriters involved in the sale of the securities may qualify as “underwriters” within the meaning of Section 2(a)(11) of the Securities Act. In addition, the underwriters’ commissions, discounts or concessions may qualify as underwriters’ compensation under the Securities Act and the rules of the Financial Industry Regulatory Authority, Inc., or FINRA.

Shares of our common stock sold pursuant to the registration statement of which this prospectus is a part will be authorized for listing and trading on The NASDAQ Capital Market. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on The NASDAQ Capital Market or any securities market or other securities exchange of the securities covered by the prospectus supplement. Underwriters may make a market in our common stock, but will not be obligated to do so and may discontinue any market making at any time without notice. We can make no assurance as to the liquidity of or the existence, development or maintenance of trading markets for any of the securities.

In order to facilitate the offering of the 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 we 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 option. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing the applicable security in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if the 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.

The underwriters, dealers and agents may engage in other transactions with us, or perform other services for us, in the ordinary course of their business.

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DESCRIPTION OF COMMON STOCK

We are authorized to issue 200,000,000 shares of common stock, par value $0.0001 per share. As of May 15, 2017, we had 9,426,238 shares of common stock outstanding and approximately 142 stockholders of record.

The following summary of certain provisions of our common stock does not purport to be complete. You should refer to the section of this prospectus entitled “Certain Provisions of Delaware Law and of the Company’s Certificate of Incorporation and Bylaws” and our restated certificate of incorporation and our restated bylaws, both of which are included as exhibits to the registration statement of which this prospectus is a part. The summary below is also qualified by provisions of applicable law.

General

The holders of common stock are entitled to one vote per share on all matters submitted to a vote of our stockholders and do not have cumulative voting rights. An election of directors by our stockholders shall be determined by a plurality of the votes cast by the stockholders entitled to vote on the election. Other matters shall be decided by the affirmative vote of our stockholders having a majority in voting power of the votes cast by the stockholders present or represented and voting on such matter, except as otherwise disclosed below.

Our bylaws provide that the holders of a majority of the outstanding shares of our common stock, if present in person or by proxy, represent a quorum for the transaction of business at stockholders meetings, except where a separate vote by a class of capital stock is required, the holders of a majority in voting power of such class, if present by remote communication or by proxy, represent a quorum for such matter. Subject to preferences that may be applicable to any preferred stock outstanding at the time, the holders of outstanding shares of common stock are entitled to receive ratably any dividends declared by our board of directors. In the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preference of any then-outstanding shares of preferred stock. Holders of our common stock do not have preemptive or conversion rights, or other subscription rights. There are no redemption provisions applicable to the common stock.

Stock Options and Warrants

As of May 15, 2017, we had outstanding options to purchase 955,565 shares of our common stock at a weighted average price $10.70 per share. All of our stock options expire 10 years after their grant date.

As of May 15, 2017, we had outstanding warrants to purchase 1,798,084 shares of our common stock at exercise prices ranging from $10.79 to $16.00 per share. Warrants to purchase 125,000 shares of our common stock will expire on August 1, 2018, warrants to purchase 28,347 shares of our common stock will expire on May 5, 2021 and warrants to purchase 1,644,737 shares of our common stock will expire on November 23, 2021.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A., with offices at 250 Royall Street, Canton, Massachusetts 02021.

Stock Exchange Listing

Our common stock is listed for quotation on The NASDAQ Capital Market under the symbol “SBPH.”

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DESCRIPTION OF PREFERRED STOCK

We are authorized to issue 10,000,000 shares of preferred stock, par value $0.0001 per share. As of the date of this prospectus, no shares of our preferred stock were outstanding or designated. The following summary of certain provisions of our preferred stock does not purport to be complete. You should refer to our restated certificate of incorporation and our restated bylaws, both of which are included as exhibits to the registration statement of which this prospectus is a part. The summary below is also qualified by provisions of applicable law.

General

Our board of directors may, without further action by our stockholders, from time to time, direct the issuance of shares of preferred stock in series and may, at the time of issuance, determine the rights, preferences and limitations of each series, including voting rights, dividend rights and redemption and liquidation preferences. Satisfaction of any dividend preferences of outstanding shares of preferred stock would reduce the amount of funds available for the payment of dividends on shares of our common stock. Holders of shares of preferred stock may be entitled to receive a preference payment in the event of any liquidation, dissolution orwinding-up of our company before any payment is made to the holders of shares of our common stock. In some circumstances, the issuance of shares of preferred stock may render more difficult or tend to discourage a merger, tender offer or proxy contest, the assumption of control by a holder of a large block of our securities or the removal of incumbent management. Upon the affirmative vote of our board of directors, without stockholder approval, we may issue shares of preferred stock with voting and conversion rights which could adversely affect the holders of shares of our common stock.

If we offer a specific series of preferred stock under this prospectus, we will describe the terms of the preferred stock in the prospectus supplement for such offering and will file a copy of the restated certificate establishing the terms of the preferred stock with the SEC. To the extent required, this description will include:

∎ the title and stated value;

∎ the number of shares offered, the liquidation preference, if any, per share and the purchase price;

∎ the dividend rate(s), period(s) and/or payment date(s), or method(s) of calculation for such dividends;

∎ whether dividends will be cumulative ornon-cumulative and, if cumulative, the date from which dividends will accumulate;

∎ the procedures for any auction and remarketing, if any;

∎ the provisions for a sinking fund, if any;

∎ the provisions for redemption, if applicable;

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

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

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

∎ voting rights, if any, of the preferred stock;

∎ a discussion of any material and/or special U.S. federal income tax considerations applicable to the preferred stock;

∎ the relative ranking and preferences of the preferred stock as to dividend rights and rights upon liquidation, dissolution or winding up of the affairs of the Company; and

∎ any material limitations on issuance of any class or series of preferred stock ranking pari passu with or senior to the series of preferred stock as to dividend rights and rights upon liquidation, dissolution or winding up of the Company.

Transfer Agent and Registrar

The transfer agent and registrar for our preferred stock will be set forth in the applicable prospectus supplement.

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DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future debt securities we may offer pursuant to this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. If we so indicate in a prospectus supplement, the terms of any debt securities offered under such prospectus supplement may differ from the terms we describe below, and to the extent the terms set forth in a prospectus supplement differ from the terms described below, the terms set forth in the prospectus supplement shall control.

We may sell from time to time, in one or more offerings under this prospectus, debt securities, which may be senior or subordinated. We will issue any such senior debt securities under a senior indenture that we will enter into with a trustee to be named in the senior indenture. We will issue any such subordinated debt securities under a subordinated indenture, which we will enter into with a trustee to be named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement, of which this prospectus is a part. We use the term “indentures” to refer to either the senior indenture or the subordinated indenture, as applicable. The indentures will be qualified under the Trust Indenture Act of 1939, as in effect on the date of the indenture. We use the term “debenture trustee” to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all the provisions of the indenture applicable to a particular series of debt securities.

General

Each indenture provides that debt securities may be issued from time to time in one or more series and may be denominated and payable in foreign currencies or units based on or relating to foreign currencies. Neither indenture limits the amount of debt securities that may be issued thereunder and each indenture provides that the specific terms of any series of debt securities shall be set forth in, or determined pursuant to, an authorizing resolution and/or a supplemental indenture, if any, relating to such series.

We will describe in each prospectus supplement the following terms relating to a series of debt securities:

∎ the title or designation;

∎ the aggregate principal amount and any limit on the amount that may be issued;

∎ the currency or units based on or relating to currencies in which debt securities of such series are denominated and the currency or units in which principal or interest or both will or may be payable;

∎ whether we will issue the series of debt securities in global form, the terms of any global securities and who the depositary will be;

∎ the maturity date and the date or dates on which principal will be payable;

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

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

∎ the terms of the subordination of any series of subordinated debt;

∎ the place or places where payments will be payable;

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

∎ the date, if any, after which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional redemption provisions;

∎ the date, if any, on which, and the price at which we are obligated, pursuant to any mandatory sinking fund provisions or otherwise, to redeem, or at the holder’s option to purchase, the series of debt securities;

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∎ whether the indenture will restrict our ability to pay dividends, or will require us to maintain any asset ratios or reserves;

∎ whether we will be restricted from incurring any additional indebtedness;

∎ a discussion of any material or special U.S. federal income tax considerations applicable to a series of debt securities;

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

∎ any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities.

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.

Conversion or Exchange Rights

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

Consolidation, Merger or Sale; No Protection in Event of a Change of Control or Highly Leveraged Transaction

The indentures do not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate.

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

Events of Default Under the Indenture

The following are events of default under the indentures with respect to any series of debt securities that we may issue:

∎ if we fail to pay interest when due and our failure continues for 90 days and the time for payment has not been extended or deferred;

∎ if we fail to pay the principal, or premium, if any, when due and the time for payment has not been extended or delayed;

∎ if we fail to observe or perform any other covenant set forth in the debt securities of such series or the applicable indentures, other than a covenant specifically relating to and for the benefit of holders of another series of debt securities, and our failure continues for 90 days after we receive written notice from the debenture trustee or holders of not less than a majority in aggregate principal amount of the outstanding debt securities of the applicable series; and

∎ if specified events of bankruptcy, insolvency or reorganization occur as to us.

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. The occurrence of an event of default may constitute an event of default under any bank credit agreements we may have in existence from time to time. In addition, the occurrence of certain events of default or an acceleration under the indenture may constitute an event of default under certain of our other indebtedness outstanding from time to time.

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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 a majority in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the debenture trustee if given by the holders), declare to be due and payable immediately the principal (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) of and premium and accrued and unpaid interest, if any, on all debt securities of that series. Before a judgment or decree for payment of the money due has been obtained with respect to debt securities of any series, the holders of a majority in principal amount of the outstanding debt securities of that series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) may rescind and annul the acceleration if all events of default, other than thenon-payment of accelerated principal, premium, if any, and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the applicable indenture (including payments or deposits in respect of principal, premium or interest that had become due other than as a result of such acceleration). 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.

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

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

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

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

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

∎ the holders of at least a majority in aggregate principal amount of the outstanding debt securities of that series have made written request, and such holders have offered reasonable indemnity to the debenture trustee to institute the proceeding as trustee; and

∎ the debenture trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series (or at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) other conflicting directions within 60 days after the notice, request and offer.

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

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

Modification of Indenture; Waiver

The debenture trustee and we may change the applicable indenture without the consent of any holders with respect to specific matters, including:

∎ to fix any ambiguity, defect or inconsistency in the indenture; and

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∎ to change anything that does not materially adversely affect the interests of any holder of debt securities of any series issued pursuant to such indenture.

In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) that is affected. However, the debenture trustee and we may make the following changes only with the consent of each holder of any outstanding debt securities affected:

∎ extending the fixed maturity of the series of debt securities;

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

∎ reducing the principal amount of discount securities payable upon acceleration of maturity;

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

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

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. 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 or in respect of a covenant or provision, which cannot be modified or amended without the consent of the holder of each outstanding debt security of the series affected;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.

Discharge

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

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

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

∎ maintain paying agencies;

∎ hold monies for payment in trust;

∎ compensate and indemnify the trustee; and

∎ appoint any successor trustee.

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

Form, Exchange, and Transfer

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

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

Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange or in the applicable indenture, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges. We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

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

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

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

Information Concerning the Debenture Trustee

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

Payment and Paying Agents

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

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

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

Governing Law

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

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Subordination of Subordinated Debt Securities

Our obligations pursuant to any subordinated debt securities will be unsecured and will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of senior indebtedness we may incur. It also does not limit us from issuing any other secured or unsecured debt.

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DESCRIPTION OF WARRANTS

General

We may issue warrants to purchase shares of our common stock, preferred stock and/or debt securities in one or more series together with other securities or separately, as described in the applicable prospectus supplement. Below is a description of certain general terms and provisions of the warrants that we may offer. Particular terms of the warrants will be described in the warrant agreements and the prospectus supplement relating to the warrants.

The applicable prospectus supplement will contain, where applicable, the following terms of and other information relating to the warrants:

∎ the specific designation and aggregate number of, and the price at which we will issue, the warrants;

∎ the currency or currency units in which the offering price, if any, and the exercise price are payable;

∎ the designation, amount and terms of the securities purchasable upon exercise of the warrants;

∎ if applicable, the exercise price for shares of our common stock and the number of shares of common stock to be received upon exercise of the warrants;

∎ if applicable, the exercise price for shares of our preferred stock, the number of shares of preferred stock to be received upon exercise, and a description of that series of our preferred stock;

∎ if applicable, the exercise price for our debt securities, the amount of debt securities to be received upon exercise, and a description of that series of debt securities;

∎ the date on which the right to exercise the warrants will begin and the date on which that right will expire or, if you may not continuously exercise the warrants throughout that period, the specific date or dates on which you may exercise the warrants;

∎ whether the warrants will be issued in fully registered form or bearer form, in definitive or global form or in any combination of these forms, although, in any case, the form of a warrant included in a unit will correspond to the form of the unit and of any security included in that unit;

∎ any applicable material U.S. federal income tax consequences;

∎ the identity of the warrant agent for the warrants and of any other depositaries, execution or paying agents, transfer agents, registrars or other agents;

∎ the proposed listing, if any, of the warrants or any securities purchasable upon exercise of the warrants on any securities exchange;

∎ if applicable, the date from and after which the warrants and the common stock, preferred stock and/or debt securities will be separately transferable;

∎ if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

∎ information with respect to book-entry procedures, if any;

∎ the anti-dilution provisions of the warrants, if any;

∎ any redemption or call provisions;

∎ whether the warrants may be sold separately or with other securities as parts of units; and

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

Transfer Agent and Registrar

The transfer agent and registrar for any warrants will be set forth in the applicable prospectus supplement.

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DESCRIPTION OF RIGHTS

General

We may issue rights to our stockholders to purchase shares of our common stock, preferred stock or the other securities described in this prospectus. We may offer rights separately or together with one or more additional rights, debt securities, preferred stock, common stock, warrants or purchase contracts, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following description sets forth certain general terms and provisions of the rights to which any prospectus supplement may relate. The particular terms of the rights to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the rights so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the rights, rights agreement or rights certificates described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable rights agreement and rights certificate for additional information before you decide whether to purchase any of our rights. We will provide in a prospectus supplement the following terms of the rights being issued:

∎ the date of determining the stockholders entitled to the rights distribution;

∎ the aggregate number of shares of common stock, preferred stock or other securities purchasable upon exercise of the rights;

∎ the exercise price;

∎ the aggregate number of rights issued;

∎ whether the rights are transferrable and the date, if any, on and after which the rights may be separately transferred;

∎ the date on which the right to exercise the rights will commence, and the date on which the right to exercise the rights will expire;

∎ the method by which holders of rights will be entitled to exercise;

∎ the conditions to the completion of the offering, if any;

∎ the withdrawal, termination and cancellation rights, if any;

∎ whether there are any backstop or standby purchaser or purchasers and the terms of their commitment, if any;

∎ whether stockholders are entitled to oversubscription rights, if any;

∎ any applicable material U.S. federal income tax considerations; and

∎ any other terms of the rights, including terms, procedures and limitations relating to the distribution, exchange and exercise of the rights, as applicable.

Each right will entitle the holder of rights to purchase for cash the principal amount of shares of common stock, preferred stock or other securities at the exercise price provided in the applicable prospectus supplement. Rights may be exercised at any time up to the close of business on the expiration date for the rights provided in the applicable prospectus supplement.

Holders may exercise rights as described in the applicable prospectus supplement. Upon receipt of payment and the rights certificate properly completed and duly executed at the corporate trust office of the rights agent or any other office indicated in the prospectus supplement, we will, as soon as practicable, forward the shares of common stock, preferred stock or other securities, as applicable, purchasable upon exercise of the rights. If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than stockholders, to or through agents, underwriters or dealers or through a combination of such methods, including pursuant to standby arrangements, as described in the applicable prospectus supplement.

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Rights Agent

The rights agent for any rights we offer will be set forth in the applicable prospectus supplement.

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DESCRIPTION OF PURCHASE CONTRACTS

We may issue purchase contracts, including contracts obligating holders to purchase from us, and for us to sell to holders, a specific or variable number of our debt securities, shares of common stock, preferred stock, warrants or rights, or securities of an entity unaffiliated with us, or any combination of the above, at a future date or dates. Alternatively, the purchase contracts may obligate us to purchase from holders, and obligate holders to sell to us, a specific or variable number of our debt securities, shares of common stock, preferred stock, warrants, rights or other property, or any combination of the above. The price of the securities or other property subject to the purchase contracts may be fixed at the time the purchase contracts are issued or may be determined by reference to a specific formula described in the purchase contracts. We may issue purchase contracts separately or as a part of units each consisting of a purchase contract and one or more of our other securities described in this prospectus or securities of third parties, including U.S. Treasury securities, securing the holder’s obligations under the purchase contract. The purchase contracts may require us to make periodic payments to holders or vice versa and the payments may be unsecured orpre-funded on some basis. The purchase contracts may require holders to secure the holder’s obligations in a manner specified in the applicable prospectus supplement.

The applicable prospectus supplement will describe the terms of any purchase contracts in respect of which this prospectus is being delivered, including, to the extent applicable, the following:

∎ whether the purchase contracts obligate the holder or us to purchase or sell, or both purchase and sell, the securities subject to purchase under the purchase contract, and the nature and amount of each of those securities, or the method of determining those amounts;

∎ whether the purchase contracts are to be prepaid;

∎ whether the purchase contracts are to be settled by delivery, or by reference or linkage to the value, performance or level of the securities subject to purchase under the purchase contract;

∎ any acceleration, cancellation, termination or other provisions relating to the settlement of the purchase contracts;

∎ any applicable material U.S. federal income tax considerations; and

∎ whether the purchase contracts will be issued in fully registered or global form.

The preceding description sets forth certain general terms and provisions of the purchase contracts to which any prospectus supplement may relate. The particular terms of the purchase contracts to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the purchase contracts so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the purchase contracts described in a prospectus supplement differ from any of the terms described above, then the terms described above will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable purchase contract for additional information before you decide whether to purchase any of our purchase contracts.

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DESCRIPTION OF UNITS

The following description, together with the additional information that we include in any applicable prospectus supplements, summarizes the material terms and provisions of the units that we may offer under this prospectus. While the terms we have summarized below will apply generally to any units that we may offer under this prospectus, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement. The terms of any units offered under a prospectus supplement may differ from the terms described below.

We will incorporate by reference from reports that we file with the SEC, the form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements, before the issuance of the related series of units. The following summaries of material terms and provisions of the units are subject to, and qualified in their entirety by reference to, all the provisions of the unit agreement and any supplemental agreements applicable to a particular series of units. We urge you to read the applicable prospectus supplements related to the particular series of units that we may offer under this prospectus, as well as any related free writing prospectuses and the complete unit agreement and any supplemental agreements that contain the terms of the units.

General

We may issue units consisting of common stock, preferred stock, one or more debt securities, warrants, rights or purchase contacts for the purchase of common stock, preferred stock and/or debt securities in one or more series, in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each security included in the unit. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time or at any time before a specified date.

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

∎ the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;

∎ any provisions of the governing unit agreement that differ from those described below; and

∎ any provisions for the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units.

The provisions described in this section, as well as those set forth in any prospectus supplement or as described under “Description of Common Stock,” “Description of Preferred Stock,” “Description of Debt Securities,” “Description of Warrants,” “Description of Rights” and “Description of Purchase Contracts” will apply to each unit, as applicable, and to any common stock, preferred stock, debt security, warrant, right or purchase contract included in each unit, as applicable.

Unit Agent

The name and address of the unit agent for any units we offer will be set forth in the applicable prospectus supplement.

Issuance in Series

We may issue units in such amounts and in such numerous distinct series as we determine.

Enforceability of Rights by Holders of Units

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

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CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF INCORPORATION AND BYLAWS

Anti-Takeover Provisions

The provisions of Delaware law, our restated certificate of incorporation and our restated bylaws may have the effect of delaying, deferring or discouraging another person from acquiring control of our company.

Delaware Law

Section 203 of the Delaware General Corporation Law prevents some Delaware corporations from engaging, under some circumstances, in a business combination, which includes a merger or sale of at least 10% of the corporation’s assets with any interested stockholder, meaning a stockholder who, together with affiliates and associates, owns or, within three years prior to the determination of interested stockholder status, did own 15% or more of the corporation’s outstanding voting stock, unless:

∎ the transaction is approved by the board of directors prior to the time that the interested stockholder became an interested stockholder;

∎ upon consummation of the transaction which resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced; or

∎ at or subsequent to such time that the stockholder became an interested stockholder the business combination is approved by the board of directors and authorized at an annual or special meeting of stockholders by at leasttwo-thirds of the outstanding voting stock that is not owned by the interested stockholder.

If Section 203 applied to us, the restrictions could prohibit or delay mergers or other takeover or change in control attempts and, accordingly, could discourage attempts to acquire us.

Restated Certificate of Incorporation and Restated Bylaw Provisions

Our restated certificate of incorporation and our restated bylaws include a number of provisions that may have the effect of deterring hostile takeovers or delaying or preventing changes in control of our management team, including the following:

∎ Board of Directors Vacancies. Our restated certificate of incorporation and restated bylaws authorize only our board of directors to fill vacant directorships. In addition, the number of directors constituting the full board of directors shall not be changed without the affirmative vote of the board of directors. These provisions hinder a stockholder from increasing the size of our board of directors and gaining control of our board of directors by filling the resulting vacancies with its own nominees.

∎ Classified Board. Our restated certificate of incorporation and proposed restated bylaws provide that our board of directors is classified into three classes of directors. The existence of a classified board could delay a successful tender offeror from obtaining majority control of our board of directors, and the prospect of that delay might deter a potential offeror. Pursuant to Delaware law, the directors of a corporation having a classified board may be removed by the stockholders only for cause, and pursuant to our restated certificate of incorporation, by the affirmative vote of at leastsixty-six and two thirds percent (66 2/3%) of the votes that all stockholders would be entitled to cast in an election of directors. In addition, stockholders will not be permitted to cumulate their votes for the election of directors.

∎ Stockholder Action; Special Meeting of Stockholders.Our restated certificate of incorporation provides that our stockholders may not take action by written consent, but may only take action at annual or special meetings of our stockholders. Our restated certificate of incorporation further provides that special meetings of our stockholders may be called only by a majority of our board of directors, the chairman of our board of directors and our chief executive officer, or upon the request of the holders of a majority of our issued and outstanding common stock.

∎ Advance Notice Requirements for Stockholder Proposals and Director Nominations. Our restated bylaws provide advance notice procedures for stockholders seeking to bring business before our annual meeting of stockholders, or to nominate candidates for election as directors at our annual meeting of stockholders. Our

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restated bylaws also specify certain requirements regarding the form and content of a stockholder’s notice. These provisions may preclude our stockholders from bringing matters before our annual meeting of stockholders or from making nominations for directors at our annual meeting of stockholders.

∎ Issuance of Undesignated Preferred Stock. Under our restated certificate of incorporation, our board of directors has the authority, without further action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by the board of directors. The existence of authorized but unissued shares of preferred stock enables our board of directors to render more difficult or to discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest or otherwise.

∎ Exclusive Forum. Our restated certificate of incorporation specifies that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for: (i) any derivative action or proceeding brought on behalf of the corporation; (ii) any action asserting a claim of breach of a fiduciary duty owed by any director, officer or other employee of the corporation to the corporation or the corporation’s stockholders; (iii) any action asserting a claim arising pursuant to any provision of the DGCL; and (iv) any action asserting a claim governed by the internal affairs doctrine. We believe this provision benefits us by providing increased consistency in the application of Delaware law by chancellors particularly experienced in resolving corporate disputes, efficient administration of cases on a more expedited schedule relative to other forums and protection against the burdens of multi-forum litigation. However, the provision may have the effect of discouraging lawsuits against our directors and officers. The enforceability of similar choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection with any applicable action brought against us, a court could find the choice of forum provisions contained in our restated certificate of incorporation to be inapplicable or unenforceable in such action.

Limitation of Liability and Indemnification

As permitted by Delaware law, we have adopted provisions in our certificate of incorporation that limit or eliminate the personal liability of our directors. Our restated certificate of incorporation limits the liability of directors to the maximum extent permitted by Delaware law. Delaware law provides that directors of a corporation will not be personally liable for monetary damages for breaches of their fiduciary duties as directors, except liability for:

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

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

∎ any unlawful payments related to dividends or unlawful stock repurchases, redemptions or other distributions; or

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

These limitations do not apply to liabilities arising under federal securities laws and do not affect the availability of equitable remedies, including injunctive relief or rescission. If Delaware law is amended to authorize the further elimination or limiting of a director, then the liability of our directors will be eliminated or limited to the fullest extent permitted by Delaware law as so amended.

As permitted by Delaware law, our certificate of incorporation also provides that:

∎ we will indemnify our directors and officers to the fullest extent permitted by law;

∎ we may indemnify our other employees and other agents to the same extent that we indemnify our officers and directors, unless otherwise determined by our board of directors; and

∎ we will advance expenses to our directors and officers in connection with legal proceedings in connection with a legal proceeding to the fullest extent permitted by law.

The indemnification provisions contained in our certificate of incorporation are not exclusive. In addition, we have entered into indemnification agreements with each of our directors and executive officers. Each of these indemnification agreements provides, among other things, that we will indemnify such director or executive officer to the fullest extent permitted by law for claims arising in his or her capacity as a director or officer, as applicable,

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provided that he or she acted in good faith and in a manner that he or she reasonably believed to be in, or not opposed to, our best interests and, with respect to any criminal proceeding, had no reasonable cause to believe that his or her conduct was unlawful. Each of these indemnification agreements provide that in the event that we do not assume the defense of a claim against a director or officer, as applicable, we will be required to advance his or her expenses in connection with his or her defense, provided that he or she undertakes to repay all amounts advanced if it is ultimately determined that he or she is not entitled to be indemnified by us.

We believe that these provisions and agreements are necessary to attract and retain qualified persons as directors and officers. Insofar as indemnification for liabilities arising under the Securities Act of 1933, which we refer to as the Securities Act, may be permitted to directors, officers or persons controlling our company pursuant to the foregoing provisions, we understand that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

In addition, we maintain standard policies of insurance under which coverage is provided to our directors and officers against losses arising from claims made by reason of breach of duty or other wrongful act, and to us with respect to payments which may be made by us to such directors and officers pursuant to the above indemnification provisions or otherwise as a matter of law.

The foregoing discussion of our restated certificate of incorporation, restated bylaws, indemnification agreements and Delaware law is not intended to be exhaustive and is qualified in its entirety by such restated certificate of incorporation, restated bylaws, indemnification agreements or law.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, we have been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

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LEGAL MATTERS

Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts, will pass upon the validity of the issuance of the securities to be offered by this prospectus.

EXPERTS

The consolidated financial statements of Spring Bank Pharmaceuticals, Inc. and its subsidiaries as of December 31, 2016 and 2015 and for each of the years in thetwo-year period ended December 31, 2016, incorporated by reference in this prospectus and registration statement from the Spring Bank Pharmaceuticals, Inc.’s Annual Report on Form10-K for the year ended December 31, 2016, have been audited by RSM US LLP, an independent registered public accounting firm, as stated in their report thereon incorporated herein by reference, and have been incorporated in this prospectus and registration statement in reliance upon such report and upon the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, and file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy these reports, proxy statements and other information at the SEC’s public reference facilities at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at1-800-SEC-0330 for more information about the operation of the public reference facilities. SEC filings are also available at the SEC’s web site athttp://www.sec.gov. This prospectus is only part of a registration statement on FormS-3 that we have filed with the SEC under the Securities Act of 1933, as amended, and therefore omits certain information contained in the registration statement. We have also filed exhibits and schedules with the registration statement that are excluded from this prospectus, and you should refer to the applicable exhibit or schedule for a complete description of any statement referring to any contract or other document. You may inspect a copy of the registration statement, including the exhibits and schedules, without charge, at the public reference room or obtain a copy from the SEC upon payment of the fees prescribed by the SEC.

We also maintain a website atwww.springbankpharm.com, through which you can access our SEC filings. The information set forth on our website is not part of this prospectus.

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INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information that we file with them. Incorporation by reference allows us to disclose important information to you by referring you to those other documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We filed a registration statement on FormS-3 under the Securities Act of 1933, as amended, with the SEC with respect to the securities we may offer pursuant to this prospectus. This prospectus omits certain information contained in the registration statement, as permitted by the SEC. You should refer to the registration statement, including the exhibits, for further information about us and the securities we may offer pursuant to this prospectus. Statements in this prospectus regarding the provisions of certain documents filed with, or incorporated by reference in, the registration statement are not necessarily complete and each statement is qualified in all respects by that reference. Copies of all or any part of the registration statement, including the documents incorporated by reference or the exhibits, may be obtained upon payment of the prescribed rates at the offices of the SEC listed above in “Where You Can Find More Information.” The documents we are incorporating by reference are:

∎ our Annual Report onForm 10-K for the year ended December 31, 2016 filed with the SEC on February 14, 2017;

∎ our Quarterly Report on Form10-Q for the quarter ended March 31, 2017 filed with the SEC on April 28, 2017;

∎ the portions of our definitive proxy statement on Schedule 14A filed with the SEC on April 28, 2017 that are deemed “filed” with the SEC under the Exchange Act;

∎ our Current Report on Form8-K filed with the SEC on May 23, 2017;

∎ the description of our common stock contained in our Registration Statement on Form8-A filed on March 14, 2016, including any amendments or reports filed for the purpose of updating such description; and

∎ all reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act after the date of this prospectus and prior to the termination or completion of the offering of securities under this prospectus shall be deemed to be incorporated by reference in this prospectus and to be a part hereof from the date of filing such reports and other documents.

Unless otherwise noted, the SEC file number for each of the documents listed above is001-37718.

In addition, all reports and other documents filed by us pursuant to the Exchange Act after the date of the initial registration statement and prior to effectiveness of the registration statement shall be deemed to be incorporated by reference into this prospectus.

Any statement contained in this prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or any other subsequently filed document that is deemed to be incorporated by reference into this prospectus modifies or supersedes the statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

You may request, orally or in writing, a copy of any or all of the documents incorporated herein by reference. These documents will be provided to you at no cost, by contacting:

Spring Bank Pharmaceuticals, Inc.

86 South Street

Hopkinton, Massachusetts 01748

Attention: Corporate Secretary

Telephone: (508)473-5993

You may also access these documents on our website,http://www.springbankpharm.com. The information contained on, or that can be accessed through, our website is not a part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

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You should rely only on information contained in, or incorporated by reference into, this prospectus and any prospectus supplement. We have not authorized anyone to provide you with information different from that contained in this prospectus or incorporated by reference in this prospectus. We are not making offers to sell the securities in any jurisdiction in which such an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such offer or solicitation.

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3,000,000 Shares

Spring Bank Pharmaceuticals, Inc.

Common Stock

PROSPECTUS SUPPLEMENT

Joint Book-Running Managers

Jefferies Piper Jaffray

August 8, 2018