Table of Contents

As filed with the Securities and Exchange Commission on August 30, 2019May 28, 2020

Registration No. 333-333-238204

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 1

to

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

PHIO PHARMACEUTICALS CORP.

(Exact name of Registrant as specified in its charter)

257 Simarano Drive, Suite 101

Marlborough, Massachusetts 01752

(508) 767-3861

(Address, including zip code, and telephone number, including area code, of Registrant’s principal executive offices)

Gerrit Dispersyn, Dr. Med. Sc.

President & CEO

Phio Pharmaceuticals Corp.

257 Simarano Drive, Suite 101

Marlborough, Massachusetts 01752

(508) 767-3861

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Copies to:

Ryan A. Murr

Gibson, Dunn & Crutcher LLP

555 Mission Street, Suite 3000

San Francisco, CA 94105

Telephone: (415) 393-8373

Facsimile: (415) 374-8430

Approximate date of commencement of proposed sale to the public:

As soon as practicable after the effective date of this Registration Statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.☒x

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

CALCULATION OF REGISTRATION FEE

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities, nor doesand it seekis not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated August 30, 2019May         , 2020

PRELIMINARY PROSPECTUSPreliminary Prospectus

Up to 8,125,946 Shares of Common Stock

This

Up to 1,841,544 Shares of Common Stock

Pursuant to this prospectus, covers the offer and saleselling stockholders identified herein (the “Selling Stockholders”) are offering on a resale basis an aggregate of up to 8,125,9461,841,544 shares of our common stock, $0.0001 par value by Lincoln Park Capital Fund, LLC$0.0001 per share (the “Common Stock), of Phio Pharmaceuticals Corp. (“Lincoln ParkPhio,” “we,” “our” or the “Selling StockholderCompany”).

The, a Delaware corporation, 1,713,064 shares of common stock being offeredwhich are issuable upon the exercise of outstanding warrants (the “Warrants”) purchased pursuant to a securities purchase agreement by and among the Company and the Selling Stockholder have been or may be issued pursuant to the purchase agreementStockholders, dated August 7, 2019 that we entered into with Lincoln Park (as amended on August 20, 2019, theMarch 31, 2020 (the “Purchase Agreement”). See “The Lincoln Park Transaction” for a description as well as 128,480 shares of which are issuable upon the exercise of Warrants issued to the Company’s financial advisor in connection with the Purchase Agreement and “Selling Stockholder” for additional information regarding Lincoln Park. The prices at which Lincoln Park may sell the Shares will be determined by the prevailing market price for the Shares or in negotiated transactions.

Agreement. We are not selling any securities under this prospectus and will not receive any of the proceeds from the sale of the Shares by the Selling Stockholder.Stockholders of the Common Stock. Upon any exercise of the Warrants by payment of cash, however, we will receive the exercise price of the Warrants.

The Selling StockholderStockholders may sell or otherwise dispose of the shares of common stock described inCommon Stock covered by this prospectus in a number of different ways and at varying prices. See “Plan of Distribution” forWe provide more information about how the Selling StockholderStockholders may sell the shares of common stock being registered pursuant to this prospectus. The Selling Stockholder is an “underwriter” within the meaning of Section 2(a)(11)or otherwise dispose of the Securities ActCommon Stock covered by this prospectus in the section entitled “Plan of 1933, as amended (the “Securities Act”).

Distribution” on page 9. Discounts, concessions, commissions and similar selling expenses attributable to the sale of Common Stock covered by this prospectus will be borne by the Selling Stockholders. We will pay theall expenses (other than discounts, concessions, commissions and similar selling expenses) relating to the registration underof the Common Stock with the Securities Act of the offer and sale by Lincoln Park of the shares covered by this prospectus, including legal and accounting fees.Exchange Commission.

Our common stock is currently quotedlisted on theThe Nasdaq Capital Market under the symbol “PHIO”. The closing“PHIO.” On May 27, 2020, the last reported sale price of our common stock on August 29, 2019, as reported byThe Nasdaq Capital Market was $0.3301$2.35 per share.

Investing in our securities involves a high degree of risk. In reviewing this prospectus,Before making any investment in these securities, you should consider carefully the risks and uncertainties described in the section entitled “Risk Factors”“Risk Factors” beginning on page 46 of this prospectus.

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 securities are not being offered in any jurisdiction where the offer is not permitted.

The date of this prospectus is May   , 20192020

TABLE OF CONTENTS

We have not authorized anyone to provide you with information other than that contained or incorporated by reference in this 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 to you. We are not offering to sell, and the Selling Stockholder is not offering to sell, securities in any jurisdictions where offers and sales are not permitted. The information contained or incorporated by reference in this prospectus or any free writing prospectus is accurate only as of its date, regardless of its time of delivery or any sale of our securities. Our business, financial condition, results of operations, and prospects may have changed since that date.

We urge you to carefully read this prospectus and any prospectus supplement, together with the information incorporated herein by reference as described under the heading “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

No action is being taken in any jurisdiction outside the United States to permit an offering of our securities or possession or distribution of this prospectus in that jurisdiction. Persons who come into possession of this 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 applicable to that jurisdiction.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSCautionary Note Regarding Forward-Looking Statements

This prospectus contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as “intends,” “believes,” “anticipates,” “indicates,” “plans,” “expects,” “suggests,” “may,” “would,” “should,” “potential,” “designed to,” “will”“will,” “ongoing,” “estimate,” “forecast,” “predict,” “could,” and similar references, although not all forward-looking statements contain these words. Forward-looking statements are neither historical facts nor assurances of future performance. These statements are based only on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, projections, anticipated events and trends, the economy and other future conditions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of our control. Risks that could cause actual results to vary from expected results expressed in our forward-looking statements include, but are not limited to:

Our actual results and financial condition may differ materially from those indicated in the forward-looking statements as a result of the foregoing factors, as well as those identified in this prospectus under the heading “Risk Factors” and in other filings the Company periodically makes with the Securities and Exchange Commission.Commission (the “SEC”). Therefore, you should not rely unduly on any of these forward-looking statements. Forward-looking statements contained in this prospectus speak as of the date hereof and the Company does not undertake to update any of these forward-looking statements to reflect a change in its views or events or circumstances that occur after the date of this report.

Prospectus Summary

The following summary highlights certain information contained elsewhere in this prospectus and the documents incorporated by reference herein. This summary provides an overview of selected information and does not contain all of the information you should consider in making your investment decision. Therefore, you should read the entire prospectus and the documents incorporated by reference herein carefully before investing in our securities. Investors should carefully consider the information set forth under “Risk Factors” beginning on page 46 of this prospectus and the financial statements and other information incorporated by reference in this prospectus. In this prospectus, unless otherwise noted, (1) the term “Phio” refers to Phio Pharmaceuticals Corp. and our subsidiary, MirImmune, LLC and (2) the terms “Company,” “we,” “us,” and “our” refer to the ongoing business operations of Phio and MirImmune, LLC, whether conducted through Phio or MirImmune, LLC.

Overview

Phio Pharmaceuticals Corp. is a biotechnology company developing the next generation of immuno-oncology therapeutics based on our self-delivering RNAi (“sd-rxRNA^®INTASYL™”) therapeutic platform. The Company'sOur efforts are focused on silencing tumor-induced suppression of the immune system through our proprietary sd-rxRNAINTASYL platform with utility in immune cells and/orand the tumor micro-environment. Our goal is to maximize the power of our sd-rxRNAdevelop powerful INTASYL therapeutic compounds by weaponizingthat can weaponize immune effector cells to overcome tumor immune escape, thereby providing patients a powerful new treatment option that goes beyond current treatment modalities.

Our development efforts are based on our broadly patented sd-rxRNAINTASYL technology platform. Our sd-rxRNAINTASYL compounds do not require a delivery vehicle to penetrate into tissues and cells and are designed to “silence” or down-regulate, the expression of a specific gene which is over-expressed in cancer. We believe that our sd-rxRNAINTASYL platform uniquely positions the Company in the field of immuno-oncology because of this and the following reasons:

The self-delivering nature of our compounds makes sd-rxRNAINTASYL ideally suited for use with adoptive cell transfer (“ACT”) treatments and direct therapeutic use. ACT consists of the infusion of immune cells with antitumor properties. These cells can be derived from unmodified (i.e. naturally occurring) immune cells, immune cells isolated from resected tumors, or genetically engineered immune cells recognizing tumor neoantigens/neoepitopesneoantigen/neoepitope cells.

Currently, ACT therapies for the treatment of solid tumors face several hurdles. Multiple inhibitory mechanisms restrain immune cells used in ACT from effectively eradicating tumors, including immune checkpoints, reduced cell fitness and cell persistence. Furthermore, the immunosuppressive tumor micro-environment (the “TME”) can pose a formidable barrier to immune cell infiltration and function.

Phio hasWe have developed a product platform based on our sd-rxRNAINTASYL technology that allows easy, precise, rapid, and selective non-genetically modified programming of ACT cells (ex-vivoex vivo, during manufacturing) and of the TME (in vivo, by local application), resulting in improved cell-based immunotherapy.

Adoptive Cell Transfer

ACT includes a number of different types of immunotherapy treatments. These treatments use immune cells, that are grown in a lab to large numbers, followed by administering them to the body to fight the cancer cells. Sometimes, immune cells that naturally recognize a tumor are used, while other times immune cells are modified or “engineered” to make them recognize and kill the cancer cells. There are several types of ACT, including: a.) non-engineered cell therapy in which immune cells are grown from the patient’s tumor or blood, such as tumor infiltrating lymphocytes (“TILs”), or from donor blood or tissue such as natural killer (“NK”) cells, dendritic cells (“DC”) and macrophages, and b.) engineered immune cells that are genetically modified to recognize specific tumor proteins and to remain in an activated state (such as T cell receptor technology (“TCRs”), chimeric antigen receptor (“CAR”) T cells, or CAR-NK cells).

In ACT, immune cells are isolated from patients, donors or retrieved from allogeneic immune cell banks. The immune cells are then expanded and modified before being returned and used to treat the patient. We believe our INTASYL compounds are ideally suited to be used in combination with ACT, in order to make these immune cells more effective.

Our approach builds on well-established methodologies of ACT and involves the treatment of immune cells with our INTASYL compoundsex vivo while they are grown in the lab and before administering them to the patient. Because our INTASYL compounds do not require a delivery vehicle to penetrate into the cells, we are able to enhance the function of these cells by merely adding our INTASYL compounds during the expansion process and without the need for genetic engineering. This step uses our INTASYL technology to reduce or eliminate the expression of genes that make the immune cells less effective. For example, with our INTASYL compounds, we can reduce the expression of immunosuppressive proteins by the therapeutic immune cells, potentially enabling them to overcome tumor resistance mechanisms and thus improving their ability to destroy the tumor cells. In various types of immune cells tested to date, INTASYL treatment results in potent silencing while maintaining close to 100% transfection efficiency and nearly full cell viability. After enhancing these cellsex vivo, they are returned to the patient for treatment.

Our lead product candidate and most advanced program being developed in ACT is PH-762, an INTASYL compound that targets the checkpoint protein PD-1. Checkpoint proteins, such as PD-1, normally act as a type of “off switch” that prevents T cells from attacking certain cells, such as cancer cells, in the body. Our T cells are immune cells that protect the body from cancer cells and are important for the activation of immune cells to fight infection.

Data developed by Phio and with collaborators has shown that PH-762 can silence PD-1 checkpoint expression, thereby removing the “off switch” and resulting in enhanced T cell activation and tumor cytotoxicity. Data released in November 2019 further supported the application of INTASYL technology in immunotherapy of cancer. PH-762 was shown to silence the expression of PD-1 in target human T cells in a potent and durable manner suitable for both ACT and intra-tumoral injection and was also shown to increase function of patient derived TILs for ACT.

We are also developing our INTASYL compound PH-804 for use in ACT. PH-804 targets the suppressive immune receptor TIGIT, which is a checkpoint protein present on T cells and NK cells. To date, we have shown that PH-804 can silence the expression of TIGIT in NK cells and T cells, overcoming their “off switch” and the cells becoming “weaponized” to kill cancer cells.

Our third recently announced product candidate is PH-894, an INTASYL compound that targets BRD4, a regulator of gene expression impacting cell differentiation. In previous studies, PH-894 has been shown to improve T cell function and persistence by differentiating T cells into a more active state (effector memory phenotype). Data, completed in partnership with the Karolinska Institutet, presented in November 2019 demonstrated that the application of PH-894, was shown to silence BRD4 in human T cells during expansion for ACT, which has the potential to confer superior anti-tumor activity. With this data, as well as results with several compounds in both T cells and NK cells, we announced the expansion of our collaboration with the Karolinska Institutet in November 2019 to build upon these findings and develop INTASYL compounds for additional information abouttargets and cell types toward clinical application in areas of the Karolinska Institutet’s ongoing clinical research.

In March 2020, we entered into a collaboration and option agreement with Medigene AG and the Helmholtz Zentrum München (“HMGU”). This three-way collaboration expands upon our outstanding research agreement with HMGU to design and develop novel candidates for the use of INTASYL compounds in ACT to enhance immune cell function. Under the agreement, Medigene AG will contribute expertise regarding clinical development, as well as proprietary research material and has the option to an exclusive license for the clinical and/or commercial development of the potential immune cell enhancers.

Tumor Micro-Environment

The TME is the environment that surrounds and feeds a tumor, including normal cells, blood vessels, immune cells, and the extracellular matrix. The TME is an immunosuppressive microenvironment that inhibits the immune system’s natural ability to recognize and destroy tumor cells by negatively impacting how immunosuppressive cells are being attracted and activated. Reprogramming different components of the TME may overcome resistance to immunotherapy. Such reprogramming of the TME by INTASYL compounds through direct local administration into the tumor, could potentially become an important form of therapy. The Company has previously shown in a clinical setting that our INTASYL compounds are safe and well-tolerated following local administration, therefore we believe that our INTASYL technology can not only be used with ACT, but can also be used as an independent therapeutic platform.

We have pipeline programs in place for the development of INTASYL compounds for direct administration into the tumor, including the use of PH-762, PH-804 and PH-894 forin situ transfection and activation of immune cells in the TME.

Data presented in January 2020 fromin vivo studies performed by the Company please refershowed that intra-tumoral injection of a mouse version of PH-804 reduced the tumor growth in colorectal carcinoma tumor bearing mice, which was shown to other documents we have filedinhibit tumor growth and was correlated with the Securitiessilencing of TIGIT mRNA expression and Exchange Commission and that are incorporated by reference into this prospectus, as listed underin increase in cytotoxic effector T cells in the heading “Incorporation of Certain Information by Reference.”TME.

Building on the animal data with PH-804, the Company conducted several animal studies with a mouse version of PH-762 and with PH-894 in a validated mouse model of hepatocellular carcinoma. These studies showed that a local administration of the mouse version of PH-762 or PH-894 through intra-tumoral injection resulted in potent anti-tumoral effects. The treated animals showed a complete and statistically significant inhibition of tumor growth, whereas placebo treated animals displayed exponential tumor growth. The preclinical findings demonstrate that direct injection of INTASYL compounds can successfully infiltrate solid tumors and impact the TME by activating the immune response in animal models of solid tumors resulting in reduced tumor growth. This is one of the key challenges for many other immunotherapy platforms to be able to achieve an adequate therapeutic effect in solid tumors.

We are also investigating other relevant compounds for TME targets, such as PH-790, an INTASYL compound targeting PD-L1. PD-L1 is a protein formed by cancer cells that activate the PD-1 “off switch” on immune cells. Our approach with PH-790 is to block the formation of the PD-L1 protein, which may prevent cancer cells from inactivating T cells and attack the cancer, and will be evaluated alongside PH-762.

Corporate Information

We were incorporated in the state of Delaware in 2011 as RXi Pharmaceuticals Corporation. On November 19, 2018, the Company changed its name to Phio Pharmaceuticals Corp., to reflect its transition from a platform company to one that is fully committed to developing groundbreaking immuno-oncology therapeutics. Our executive offices are located at 257 Simarano Drive, Suite 101, Marlborough, MA 01752, and our telephone number is (508) 767-3861. The Company’s website address ishttp://www.phiopharma.com. Our website and the information contained on that site, or connected to that site, is not part of or incorporated by reference into this prospectus.

Our certificate of incorporation provides that the Court of Chancery of the State of Delaware is the exclusive forum for the following types of actions or proceedings: any derivative action or proceeding brought on behalf of the Company, any action asserting a claim of breach of a fiduciary duty owed by any director, officer or other employee of the Company to the Company or the Company’s stockholders, any action asserting a claim against the Company arising pursuant to any provision of the Delaware General Corporation Law or the Company’s certificate of incorporation or bylaws, or any action asserting a claim against the Company governed by the internal affairs doctrine. Despite the fact that our certificate of incorporation provides for this exclusive forum provision to be applicable to the fullest extent permitted by applicable law, Section 27 of the Securities and Exchange Act of 1934, as amended (the “Exchange Act”), creates exclusive federal jurisdiction over all suits brought to enforce any duty or liability created by the Exchange Act or the rules and regulations thereunder and Section 22 of the Securities Act of 1933, as amended (the “Securities Act”), creates concurrent jurisdiction for federal and state courts over all suits brought to enforce any duty or liability created by the Securities Act or the rules and regulations thereunder. As a result, this provision of our certificate of incorporation would not apply to claims brought to enforce a duty or liability created by the Securities Act, Exchange Act, or any other claim for which the federal courts have exclusive jurisdiction.

THE OFFERING

RISK FACTORS

Investing in our securities involves a high degree of risk. Before investing in our securities, you should carefully consider the risks, uncertainties and assumptions described belowcontained in this prospectus and discussed under the heading “Risk Factors” included in our most recent Annual Report on Form 10-K for the year ended December 31, 2018,2019, as revised or supplemented by subsequent filings, which are on file with the Securities and Exchange CommissionSEC and are incorporated herein by reference, and which may be amended, supplemented or superseded from time to time by other reports we file with the Securities and Exchange CommissionSEC in the future.

Our business, financial condition, results of operations and future growth prospects could be materially and adversely affected by any of these risks. In these circumstances, the market price of our common stockCommon Stock could decline, and you may lose all or part of your investment. The risks and uncertainties incorporated by reference into this prospectus are not the only ones we face. Additional risks and uncertainties not presently known or which we consider immaterial as of the date hereof may also have an adverse effect on our business.investment.

Risks Related to This Offering

The sale or issuance of our common stock to Lincoln Park may cause dilution and the sale of the shares of common stock acquired by Lincoln Park, or the perception that such sales may occur, could cause the price of our common stock to fall.

On August 7, 2019, we entered into the Purchase Agreement with Lincoln Park, pursuant to which Lincoln Park has committed to purchase up to $10,000,000 of our common stock. Upon the execution of the Purchase Agreement, we issued 500,000 Commitment Shares to Lincoln Park as a fee for its commitment to purchase shares of our common stock under the Purchase Agreement. The remaining shares of our common stock that may be issued under the Purchase Agreement may be sold by us to Lincoln Park at our discretion from time to time over a 30-month period commencing after the satisfaction of certain conditions set forth in the Purchase Agreement, including that the SEC has declared effective the registration statement that includes this prospectus, and subject to applicable Nasdaq limits on the number of shares that we can sell to Lincoln Park, absent stockholder approval. The purchase price for the shares that we may sell to Lincoln Park under the Purchase Agreement will fluctuate based on the price of our common stock. Depending on market liquidity at the time, sales of such shares may cause the trading price of our common stock to fall.

We generally have the right to control the timing and amount of any future sales of our shares to Lincoln Park. Additional sales of our common stock, if any, to Lincoln Park will depend upon market conditions and other factors to be determined by us. We may ultimately decide to sell to Lincoln Park all, some, or none of the additional shares of our common stock that may be available for us to sell pursuant to the Purchase Agreement. If and when we do sell shares to Lincoln Park, after Lincoln Park has acquired the shares, Lincoln Park may resell all, some or none of those shares at any time or from time to time in its discretion. Therefore, sales to Lincoln Park by us could result in substantial dilution to the interests of other holders of our common stock. Additionally, the sale of a substantial number of shares of our common stock to Lincoln Park, or the anticipation of such sales, could make it more difficult for us to sell equity or equity-related securities in the future at a time and at a price that we might otherwise wish to effect sales.

We may require additional financing to sustain our operations and without it we may not be able to continue operations.

The Company believes that its existing cash, and the potential proceeds available under the Purchase Agreement with Lincoln Park (assuming the Company is able to access the full amount), should be sufficient to fund the Company’s operations for at least the next twelve months. We have generated significant losses to date and expect to continue to incur significant operating losses as we advance our product candidates through drug development and the regulatory process. In the future, we will be dependent on obtaining funding from third parties, such as proceeds from the issuance of debt, sale of equity, funded research and development programs and payments under partnership and collaborative agreements, in order to maintain our operations and meet our obligations to licensors. There is no guarantee that debt, additional equity or other funding will be available to us on acceptable terms, or at all.

The extent we rely on Lincoln Park as a source of funding will depend on a number of factors including, the prevailing market price of our common stock and the extent to which we are able to secure working capital from other sources. If obtaining sufficient funding from Lincoln Park were to prove unavailable or prohibitively dilutive, we will need to secure another source of funding in order to satisfy our working capital needs. Even if we sell all $10,000,000 under the Purchase Agreement to Lincoln Park, we may still need additional capital to fully implement our business, operating and development plans. Should the financing we require to sustain our working capital needs be unavailable or prohibitively expensive when we require it, the consequences could be a material adverse effect on our business, operating results, financial condition and prospects.

USE OF PROCEEDS

This prospectus relates to shares of our common stock that may be offered and sold from time to time by Lincoln Park. We will receive no proceeds from the sale of shares of common stock by Lincoln Park in this offering. We may receive up to $10,000,000 in aggregate gross proceeds from any sales of our common stock to Lincoln Park under the Purchase Agreement after the date of this prospectus. We will pay the expenses relating to the registration under the Securities Act of the offer and sale by Lincoln Park of the shares covered by this prospectus, including legal and accounting fees.

Use of Proceeds

We will not receive any of the proceeds from the sale of the Common Stock by the Selling Stockholders. The shares offered hereby are issuable upon the exercise of the Warrants. Upon exercise of such Warrants for cash, we will receive the applicable cash exercise price paid by the holders of the Warrants.

DIVIDEND POLICY

We have never paid any cash dividends and do not anticipate paying any cash dividends on our common stock in the foreseeable future. We expect to retain future earnings, if any, for use in our development activities and the operation of our business. The payment of any future dividends will be subject to the discretion of our Board of Directors and will depend, among other things, upon our results of operations, financial condition, cash requirements, prospects and other factors that our Board of Directors may deem relevant.

lincoln park Transaction

General

On August 7, 2019, we entered into a purchase agreement with Lincoln Park, which, as amended on August 20, 2019, we refer to in this prospectus as the “Purchase Agreement,” pursuant to which Lincoln Park has agreed to purchase from us up to an aggregate of $10,000,000 of our common stock (subject to certain limitations) from time to time over the term of the Purchase Agreement. Also on August 7, 2019, we entered into a registration rights agreement with Lincoln Park, which we refer to in this prospectus as the “Registration Rights Agreement,” pursuant to which we have filed with the SEC the registration statement that includes this prospectus to register for resale under the Securities Act of 1933, as amended, or the “Securities Act,” the shares of common stock that have been or may be issued to Lincoln Park under the Purchase Agreement.

Following the execution of the Purchase Agreement, we issued 500,000 shares of common stock to Lincoln Park as consideration for its commitment to purchase shares of our common stock under the Purchase Agreement, which we refer to in this prospectus as the “Commitment Shares.” We do not have the right to commence any sales of our common stock to Lincoln Park under the Purchase Agreement until certain conditions set forth in the Purchase Agreement, all of which are outside of Lincoln Park’s control, have been satisfied, including that the registration statement of which this prospectus is a part is declared effective by the Securities and Exchange Commission.

Thereafter, under the terms and subject to the conditions of the Purchase Agreement, we have the right to sell to Lincoln Park, and Lincoln Park is obligated to purchase, up to $10,000,000 of shares of our common stock, subject to certain limitations set forth in the Purchase Agreement, from time to time, over a 30-month period.

Under the Purchase Agreement, on any business day selected by the Company, the Company may direct Lincoln Park to purchase shares of our common stock in amounts up to 200,000 shares (or up to $50,000 in shares of common stock, whichever is greater) in a “regular purchase,” which amounts may be increased to up to 500,000 shares provided the market price of our common stock at the time of sale exceeds is not below certain threshold prices, as set forth in the Purchase Agreement, subject in each case to $1,000,000 in total purchase proceeds per purchase date. In addition to regular purchases, the Company may also direct Lincoln Park to purchase additional amounts as accelerated purchases or as additional purchases if the Company has utilized the Regular Purchase Amount in full and if the closing sale price of the Common Stock exceeds certain threshold prices, as set forth in the Purchase Agreement. The purchase price of the shares that may be sold to Lincoln Park under the Purchase Agreement will be based on the market price of our common stock preceding the time of sale as computed under the Purchase Agreement.

In accordance with applicable rules of The Nasdaq Capital Market, the Purchase Agreement also limits the Company’s issuance of shares of Common Stock to Lincoln Park thereunder to 5,015,730 shares of Common Stock, representing 19.99% of the shares of Common Stock outstanding on the date of the Purchase Agreement (the “Exchange Cap”) unless (a) stockholder approval is obtained to issue more than such amount or (b) the average price of all applicable sales of our common stock to Lincoln Park under the Purchase Agreement equals or exceeds the lower of (i) the closing price of our common stock on the Nasdaq Capital Market immediately preceding August 7, 2019 plus an incremental amount or (ii) the average of the closing price of our common stock on the Nasdaq Capital Market for the five Business Days immediately preceding August 7, 2019 plus an incremental amount, such that issuances and sales of our common stock to Lincoln Park under the Purchase Agreement would be exempt from the Exchange Cap limitation under applicable Nasdaq rules.

The Purchase Agreement also prohibits us from directing Lincoln Park to purchase any shares of common stock if those shares, when aggregated with all other shares of our common stock then beneficially owned by Lincoln Park and its affiliates, would result in Lincoln Park and its affiliates having beneficial ownership, at any single point in time, of more than 9.99% of the then total outstanding shares of our common stock, as calculated pursuant to Section 13(d) of the Securities Exchange Act of 1934, as amended, or the “Exchange Act,” and Rule 13d-3 thereunder, which limitation we refer to as the “Beneficial Ownership Cap”.

There are no trading volume requirements or restrictions under the Purchase Agreement, and we will control the timing and amount of any sales of our common stock to Lincoln Park. We may at any time in our sole discretion terminate the Purchase Agreement without fee, penalty or cost upon one business days’ notice. There are no restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement or Registration Rights Agreement, other than a prohibition on entering into any “Variable Rate Transaction,” as defined in the Purchase Agreement. Lincoln Park may not assign or transfer its rights and obligations under the Purchase Agreement.

A total of 8,125,946 shares of our common stock are being offered under this prospectus, which may be less than the amount of shares issuable under the Purchase Agreement. As of August 23, 2019, there were 25,591,197 shares of our common stock outstanding, of which 25,124,081 shares were held by non-affiliates. If all of the 8,125,946 shares offered by Lincoln Park under this prospectus were issued and outstanding as of August 23, 2019, such shares would represent 24% of the total number of shares of our common stock outstanding and 25% of the total number of outstanding shares held by non-affiliates, in each case as of the date hereof; however, these percentages do not give effect to the prohibition contained in the Purchase Agreement that prevents us from selling and issuing to Lincoln Park shares of our common stock that would cause us to exceed the Exchange Cap or that would cause Lincoln Park and its affiliates to exceed the Beneficial Ownership Cap.

If we elect to issue and sell more than the 8,125,946 shares offered under this prospectus to Lincoln Park, which we have the right, but not the obligation, to do, we must first register for resale under the Securities Act any such additional shares, which could cause additional substantial dilution to our stockholders. The number of shares ultimately offered for resale by Lincoln Park is dependent upon the number of shares we sell to Lincoln Park under the Purchase Agreement.

Issuances of our common stock in this offering will not affect the rights or privileges of our existing stockholders, except that the economic and voting interests of each of our existing stockholders will be diluted as a result of any such issuance. Although the number of shares of common stock that our existing stockholders own will not decrease, the shares owned by our existing stockholders will represent a smaller percentage of our total outstanding shares after any such issuance to Lincoln Park.

Purchase of Shares Under the Purchase Agreement

Under the Purchase Agreement, on any business day selected by us, we may direct Lincoln Park to purchase up to 200,000 shares of our common stock on any such business day, which we refer to as a “Regular Purchase,” provided, however, that (i) the Regular Purchase may be increased to up to 300,000 shares, provided that the closing sale price is not below $0.60 on the purchase date, (ii) the Regular Purchase may be increased to up to 400,000 shares, provided that the closing sale price is not below $0.80 on the purchase date, and (iii) the Regular Purchase may be increased to up to 500,000 shares, provided that the closing sale price is not below $1.00 on the purchase date. In each case, the maximum amount of any single Regular Purchase may not exceed $1,000,000 per purchase. The purchase price per share for each such Regular Purchase will be equal to the lower of:

In addition to Regular Purchases described above, we may also direct Lincoln Park, on any business day on which we have properly submitted a Regular Purchase for the full amount of our common stock permitted on such business day, to purchase an additional amount of our common stock, which we refer to as an “Accelerated Purchase,” not to exceed the lesser of:

The purchase price per share for each such Accelerated Purchase will be equal to the lower of:

We may also direct Lincoln Park, not later than 1:00 p.m., Eastern time, on a business day on which an Accelerated Purchase has been completed and all of the shares to be purchased thereunder have been delivered to Lincoln Park in accordance with the Purchase Agreement prior to such time on such business day to purchase an additional amount of our common stock, which we refer to as an Additional Accelerated Purchase, of up to the lesser of:

The purchase price per share for each such Additional Accelerated Purchase will be equal to the lower of:

The Company has the right, in its sole discretion, to set a minimum price threshold for each Accelerated Purchase and Additional Accelerated Purchase in the notice provided with respect to such Accelerated Purchase and Additional Accelerated Purchase, and the Company may direct multiple Regular, Accelerated and Additional Accelerated Purchases in a day provided that delivery of shares has been completed with respect to any prior Regular, Accelerated and Additional Accelerated Purchases that Lincoln Park has purchased.

In the case of the Regular Purchases, Accelerated Purchases and Additional Accelerated Purchases, the purchase price per share will be equitably adjusted for any reorganization, recapitalization, non-cash dividend, stock split, reverse stock split or other similar transaction occurring during the business days used to compute the purchase price.

Other than as described above, there are no trading volume requirements or restrictions under the Purchase Agreement, and we will control the timing and amount of any sales of our common stock to Lincoln Park.

Events of Default

Events of default under the Purchase Agreement include the following:

Lincoln Park does not have the right to terminate the Purchase Agreement upon any of the events of default set forth above. During an event of default, all of which are outside of Lincoln Park’s control, we may not direct Lincoln Park to purchase any shares of our common stock under the Purchase Agreement.

Our Termination Rights

We have the unconditional right, at any time, for any reason and without any payment or liability to us, to give notice to Lincoln Park to terminate the Purchase Agreement. In the event of bankruptcy proceedings by or against us, the Purchase Agreement will automatically terminate without action of any party.

No Short-Selling or Hedging by Lincoln Park

Lincoln Park has agreed that neither it nor any of its affiliates shall engage in any direct or indirect short-selling or hedging of our common stock during any time prior to the termination of the Purchase Agreement.

Prohibitions on Variable Rate Transactions

There are no restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement or Registration Rights Agreement other than a prohibition on entering into a “Variable Rate Transaction,” as defined in the Purchase Agreement.

Effect of Performance of the Purchase Agreement on Our Stockholders

All 8,125,946 shares registered in this offering which have been or may be issued or sold by us to Lincoln Park under the Purchase Agreement are expected to be freely tradable. It is anticipated that shares registered in this offering will be sold over a period of up to 30 months commencing on the date that the registration statement including this prospectus becomes effective. The sale by Lincoln Park of a significant amount of shares registered in this offering at any given time could cause the market price of our common stock to decline and to be highly volatile. Sales of our common stock to Lincoln Park, if any, will depend upon market conditions and other factors to be determined by us. We may ultimately decide to sell to Lincoln Park all, some or none of the additional shares of our common stock that may be available for us to sell pursuant to the Purchase Agreement. If and when we do sell shares to Lincoln Park, after Lincoln Park has acquired the shares, Lincoln Park may resell all, some or none of those shares at any time or from time to time in its discretion. Therefore, sales to Lincoln Park by us under the Purchase Agreement may result in substantial dilution to the interests of other holders of our common stock. In addition, if we sell a substantial number of shares to Lincoln Park under the Purchase Agreement, or if investors expect that we will do so, the actual sales of shares or the mere existence of our arrangement with Lincoln Park may make it more difficult for us to sell equity or equity-related securities in the future at a time and at a price that we might otherwise wish to effect such sales. However, we have the right to control the timing and amount of any additional sales of our shares to Lincoln Park and the Purchase Agreement may be terminated by us at any time at our discretion without any cost to us.

Pursuant to the terms of the Purchase Agreement, we have the right, but not the obligation, to direct Lincoln Park to purchase up to $10,000,000 of our common stock, exclusive of the 500,000 shares issued to Lincoln Park on such date as a commitment fee. Depending on the price per share at which we sell our common stock to Lincoln Park pursuant to the Purchase Agreement, we may need to sell to Lincoln Park under the Purchase Agreement more shares of our common stock than are offered under this prospectus in order to receive aggregate gross proceeds equal to the $10,000,000 total commitment available to us under the Purchase Agreement. If we choose to do so, we must first register for resale under the Securities Act such additional shares of our common stock, which could cause additional substantial dilution to our stockholders. The number of shares ultimately offered for resale by Lincoln Park under this prospectus is dependent upon the number of shares we direct Lincoln Park to purchase under the Purchase Agreement.

The Purchase Agreement prohibits us from issuing or selling to Lincoln Park under the Purchase Agreement (i) any shares of our common stock if those shares, when aggregated with all other shares of our common stock then beneficially owned by Lincoln Park and its affiliates, would exceed the Beneficial Ownership Cap and (ii) shares of our common stock in excess of the Exchange Cap, unless we obtain stockholder approval to issue shares in excess of the Exchange Cap or the average price of all applicable sales of our common stock to Lincoln Park under the Purchase Agreement equals or exceeds the lower of (a) the closing price of our common stock on the Nasdaq Capital Market immediately preceding August 7, 2019 plus an incremental amount or (b) the average of the closing price of our common stock on the Nasdaq Capital Market for the five Business Days immediately preceding August 7, 2019 plus an incremental amount, such that the transactions contemplated by the Purchase Agreement are exempt from the Exchange Cap limitation under applicable NASDAQ rules.

The following table sets forth the amount of gross proceeds we would receive from Lincoln Park from our sale of shares to Lincoln Park under the Purchase Agreement at varying purchase prices: