GeneralThe number of shares of our common stock outstanding referenced above is based on 24,027,891 shares of common stock outstanding as of March 31, 2023, and excludes the following as of March 31, 2023:

Unless otherwise indicated, all information contained in this prospectus assumes or gives effect to no exercise of the outstanding options or warrants described above.

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THE LINCOLN PARK TRANSACTION

General

On October 18, 2019,May 8, 2023, we entered into the Purchase Agreement with Lincoln Park, pursuant to which providesLincoln Park has agreed to purchase from us up to an aggregate of $26.0 million of our common stock (subject to certain limitations) from time to time over the term of the Purchase Agreement.

Also on May 8, 2023, we entered into the Registration Rights Agreement, pursuant to which we filed with the SEC the registration statement of which this prospectus forms a part to register under the Securities Act for resale by Lincoln Park up to 5,000,000 shares of common stock, consisting of (i) the 599,216 Commitment Shares that uponwe previously issued to Lincoln Park on May 8, 2023 as consideration for its commitment to purchase shares of our common stock at our direction from time to time after the Commencement Date under the Purchase Agreement and (ii) up to 4,400,784 shares of our common stock that we may elect to sell to Lincoln Park, in our sole discretion, from time to time from and after the Commencement Date under the Purchase Agreement, including the Initial Purchase Shares.

We do not have the right to commence any sales of common stock to Lincoln Park under the Purchase Agreement until all of the conditions set forth in the Purchase Agreement have been satisfied on the Commencement Date, including that the registration statement of which this prospectus forms a part is declared effective by the SEC and a final prospectus relating thereto is filed with the SEC. On the Commencement Date, at our discretion, we intend to issue and sell the Initial Purchase Shares, under the terms and subject to the conditions and limitations set forth therein, Aspire Capital is committed to purchase up to an aggregate of $15.0 million of our shares of common stock over the term of the Purchase Agreement. In consideration for entering into the Purchase Agreement, concurrently with the execution of the Purchase Agreement, we issued to Aspire CapitalLincoln Park. From and after the 142,658 shares of our common stock as a commitment fee. Concurrently with entering into the Purchase Agreement, we also entered into the Registration Rights Agreement, in which we agreed to file one or more registration statements as permissible and necessary to register under the Securities Act, the sale of the shares of our common stock that have been and may be issued to Aspire Capital under the Purchase Agreement.

We previously registered the sale of up to 1,642,658 shares of our common stock under the Securities Act by Aspire Capital, all of which we have previously issued to Aspire Capital pursuant to the Purchase Agreement for aggregate proceeds of approximately $3.3 million, and approximately $11.7 million of common stock remains available for sale. Accordingly, pursuant to the Purchase Agreement and the Registration Rights Agreement, we are registering 6,192,087 shares of our common stock under the Securities Act, which we may issue to Aspire Capital after this registration statement is declared effective under the Securities Act. All 6,192,087 shares of common stock are being offered pursuant to this prospectus. Under the Purchase Agreement, we have the right but not the obligation to issue more than the 6,192,087 shares of common stock included in this prospectus to Aspire Capital under some circumstances.  

However, pursuant to the Purchase Agreement, the aggregate number of sharesCommencement Date, on any business day that we may issue to Aspire Capital under the Purchase Agreement may in no case exceed 1,099,527 shares of our common stock (which is equal to 19.99% of the common stock outstanding as of April 29, 2020) unless (i) stockholder approval is obtained to issue more, in which case this 1,099,527 share limitation will not apply, or (ii) stockholder approval has not been obtained and at any time the 1,099,527 share limitation is reached and at all times thereafter the average price paid for all shares issued under the Purchase Agreement is equal to or greater than $1.89, referred toselect as the Minimum Price; provided that at no one point in time shall Aspire Capital (together with its affiliates) beneficially own more than 19.99% of our common stock.

After the SEC has declared effective the registration statement of which this prospectus is a part, on any trading daypurchase date therefor on which the closing sale price of our common stock is not less than $0.25 per share,below the Floor Price, we have the right, inmay, from time to time and at our sole discretion for a period of up to present Aspire Capital with a Purchase Notice, directing Aspire Capital (as principal)36-months after the Commencement Date, by written notice delivered by us to Lincoln Park, direct Lincoln Park to purchase up to 15,000125,000 shares of common stock (subject to adjustment as set forth in the Purchase Agreement) in a Regular Purchase, at a purchase price per share that will be determined and fixed in accordance with the Purchase Agreement at the time we deliver such written notice to Lincoln Park on the purchase date for such Regular Purchase. The maximum share limit for a Regular Purchase shall be increased to higher share threshold amounts in the Purchase Agreement, up to a maximum share limit of 175,000 shares of common stock (subject to adjustment as set forth in the Purchase Agreement), with the applicable maximum share limit determined by whether the closing price for our common stock on the applicable purchase date exceeds certain price thresholds set forth in the Purchase Agreement. In any case, however, Lincoln Park’s maximum purchase commitment in any single Regular Purchase may not exceed $1.0 million. The purchase price per share of common stock sold in each such Regular Purchase, if any, will be based on market prices of the common stock over a specified period immediately preceding the time of sale as computed under the Purchase Agreement.

In addition, at our discretion, Lincoln Park has committed to purchase other “accelerated amounts” and/or “additional accelerated amounts” under certain circumstances. We will control the timing and amount of any sales of our common stock to Lincoln Park. The purchase price per share of common stock sold in each such accelerated purchase and additional accelerated purchase, if any, will be based on market prices of the common stock on the applicable purchase dates for such accelerated purchases and additional accelerated purchases as computed under the Purchase Agreement.

Under the applicable Nasdaq listing rules, in no event may we issue to Lincoln Park under the Purchase Agreement more than the Exchange Cap limit of 4,809,486 shares of our common stock, which number of shares is equal to 19.99% of the shares of common stock outstanding immediately prior to the execution of the Purchase Agreement, unless (i) we first obtain stockholder approval to issue shares of common stock in excess of the Exchange Cap in accordance with applicable Nasdaq listing rules, or (ii) at the time we have issued shares of common stock equal to the Exchange Cap and at all times thereafter, the average price per businessshare of common stock for all shares of common stock sold by us to Lincoln Park under the Purchase Agreement equals or exceeds $0.8225 per share (representing the lower of the official closing price of the common stock on Nasdaq on the trading day upimmediately preceding the date of the Purchase Agreement and the average official closing price of the common stock on Nasdaq for the five consecutive trading days ending on the trading day immediately preceding the date of the Purchase Agreement, as adjusted under applicable Nasdaq rules to $15.0 milliontake into account the issuance of Commitment Shares to Lincoln Park for non-cash consideration), such that the Exchange Cap limitation would no longer apply to issuances and sales of common stock by us to Lincoln Park under the Purchase Agreement under applicable Nasdaq listing rules.

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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 common stock then beneficially owned by Lincoln Park (as calculated pursuant to Section 13(d) of the Exchange Act and Rule 13d-3 thereunder), would result in Lincoln Park beneficially owning more than the Beneficial Ownership Cap of 9.99% of the outstanding shares of common stock.

We will control the timing and amount of any sales of common stock to Lincoln Park pursuant to the Purchase Agreement. Lincoln Park has no right to require us to sell any shares of common stock to Lincoln Park under the Purchase Agreement, but Lincoln Park is obligated to make purchases of common stock as we direct, upon the terms and subject to the satisfaction of the conditions set forth in the Purchase Agreement. Neither we nor Lincoln Park may assign or transfer our respective rights and obligations under the Purchase Agreement; provided, however, that any transaction, whether by merger, reorganization, restructuring or consolidation, financing or otherwise, whereby we remain the surviving entity immediately after such transaction shall not be deemed an assignment by us. No provision of the Purchase Agreement or the Registration Rights Agreement may be modified or waived by us or Lincoln Park.

Actual sales of shares of common stock by us to Lincoln Park under the Purchase Agreement will depend on a variety of factors to be determined by us from time to time, including, among others, market conditions, the trading price of the common stock and determinations by us as to the appropriate sources of funding for us and our operations.

As consideration for Lincoln Park’s commitment to purchase shares of common stock from us at our direction from time to time from and after the Commencement Date pursuant to the Purchase Agreement, promptly following our execution of the Purchase Agreement and the Registration Rights Agreement, we issued 599,216 Commitment Shares to Lincoln Park on May 8, 2023. All 599,216 Commitment Shares that we issued to Lincoln Park are included in the 5,000,000 shares of common stock being registered under the Securities Act for resale by Lincoln Park under the registration statement of which this prospectus forms a part.

As of May 16, 2023, there were 24,746,044 shares of common stock outstanding (which includes the 599,216 Commitment Shares we issued to Lincoln Park on May 8, 2023 in consideration of Lincoln Park’s obligation to purchase shares of our common stock at our direction under the Purchase Agreement). Although the Purchase Agreement provides that we may, in our discretion, from time to time after the aggregate overdate of this prospectus and during the term of the Purchase Agreement, at a Purchase Price calculated by referencedirect Lincoln Park to the prevailing market price of our common stock over the preceding 10-business day period (as more specifically described below); however, no sale pursuant to a Purchase Notice may exceed $500,000 per trading day.

In addition, on any date on which we submit a Purchase Notice for 15,000 shares to Aspire Capital, we also have the right, in our sole discretion, to present Aspire Capital with a VWAP Purchase Notice directing Aspire Capital to purchase an amount of stock equal to up to 30% of the aggregate shares of our common stock tradedfrom us in one or more purchases under the Purchase Agreement, for a maximum aggregate purchase price of up to $26.0 million, only 5,000,000 shares of common stock (599,216 of which represent the Commitment Shares that have been issued by us to Lincoln Park on May 8, 2023, for which we will receive no cash proceeds) are being registered for resale under the Nasdaq Capital Market on the next trading day, subjectregistration statement of which this prospectus forms a part. If, in addition to the VWAP599,216 Commitment Shares that are currently outstanding, all of the additional 4,400,784 shares of common stock offered for resale by Lincoln Park under this prospectus (without taking into account the 19.99% Exchange Cap limitation applicable to issuances and sales of common stock under the Purchase Share Volume MaximumAgreement) were issued and outstanding as of May 16, 2023, such shares would represent approximately 17.15% of the VWAP Minimum Price Threshold. The VWAP Purchase Price is calculated by reference to the prevailing market pricetotal number of shares of our common stock (as more specifically described below).outstanding as of May 16, 2023.

The Purchase Agreement provides that we and Aspire Capital shall not effect any salesPurchases of Shares of our Common Stock under the Purchase Agreement

The Initial Purchase

On the Commencement Date upon our request, Lincoln Park will purchase the Initial Purchase Shares at the Initial Purchase Price, which equals the lesser of (i) the closing sale price of the common stock on the business day immediately preceding the Commencement Date and (ii) the average of the closing sales prices of the common stock for the 10 consecutive business days ending on the business day immediately preceding the Commencement Date.

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Regular Purchases

On the first business day following the Commencement Date, on any business day that we select as the purchase date wheretherefor on which the closing sale price of our common stock is less thannot below the Floor Price. TherePrice (and provided all shares of common stock subject to all prior Regular Purchases that we have effected under the Purchase Agreement, if any, have been received by Lincoln Park before we deliver notice to Lincoln Park for such Regular Purchase in accordance with the Purchase Agreement), we may, by written notice delivered by us to Lincoln Park, direct Lincoln Park to purchase up to 125,000 shares of common stock on such purchase date in a Regular Purchase, provided, however, that the maximum number of shares we may sell to Lincoln Park in a Regular Purchase may be increased to:

In any case, however, Lincoln Park’s maximum purchase commitment in any single Regular Purchase may not exceed $1.0 million.

The purchase price per share of common stock sold in each such Regular Purchase, if any, will be equal to the lower of:

Accelerated Purchases

In addition to Regular Purchases described above, on any purchase date for a Regular Purchase on which we have properly submitted a Regular Purchase notice directing Lincoln Park to purchase the maximum number of shares of our common stock that we are then permitted to include in a single Regular Purchase notice (and provided all shares of common stock subject to all prior Regular Purchases, Accelerated Purchases and Additional Accelerated Purchases that we have effected under the Purchase Agreement prior to such purchase date, if any, have been received by Lincoln Park before we deliver notice to Lincoln Park for such Accelerated Purchase in accordance with the Purchase Agreement), we may, by written notice delivered by us to Lincoln Park simultaneously with such Regular Purchase notice for such corresponding Regular Purchase, direct Lincoln Park to purchase an additional amount of our common stock, which we refer to as an Accelerated Purchase, on the next business day following such purchase date for such corresponding Regular Purchase, which we refer to as the Accelerated Purchase Date, not to exceed the lesser of:

The purchase price per share for the shares of common stock subject to an Accelerated Purchase will be equal to 97% of the lower of:

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Additional Accelerated Purchases

We may also direct Lincoln Park, by written notice delivered to Lincoln Park prior to 1:00 p.m., Eastern time, on the same Accelerated Purchase Date on which an Accelerated Purchase Measurement Period for an Accelerated Purchase has ended prior to such time (and provided all shares of common stock subject to all prior Regular Purchases, Accelerated Purchases and Additional Accelerated Purchases that we have effected under the Purchase Agreement, including those prior Accelerated Purchases and Additional Accelerated Purchases effected on the same Accelerated Purchase Date as the applicable Additional Accelerated Purchase, if any, have been received by Lincoln Park in accordance with the Purchase Agreement before we deliver notice to Lincoln Park for such Additional Accelerated Purchase), to purchase an additional amount of our common stock on such same Accelerated Purchase Date, which we refer to as an Additional Accelerated Purchase, of up to the lesser of:

The purchase price per share for the shares subject to an Additional Accelerated Purchase will be equal to 97% of the lower of:

We may, in our sole discretion, submit multiple Additional Accelerated Purchase notices to Lincoln Park prior to 1:00 p.m., Eastern time, on a single Accelerated Purchase Date, again provided all shares of common stock subject to all prior Regular Purchases, Accelerated Purchases and Additional Accelerated Purchases, including those prior Accelerated Purchases and Additional Accelerated Purchases effected on the same Accelerated Purchase Date as the applicable Additional Accelerated Purchase have been properly delivered to Lincoln Park in accordance with the Purchase Agreement prior to such time.

In the case of the Initial Purchase, Regular Purchases, Accelerated Purchases and Additional Accelerated Purchases, the purchase prices per share of common stock to be sold therein will be equitably adjusted for any reorganization, recapitalization, non-cash dividend, 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 Aspire Capital. AspireLincoln Park.

Events of Default

“Events of Default” under the Purchase Agreement include, among others, the following:

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Lincoln Park does not have the right to requireterminate the Purchase Agreement upon the occurrence of any salesof the Events of Default set forth above, all of which are outside of Lincoln Park’s control, although the Purchase Agreement would automatically terminate without any action of us or Lincoln Park in the event of any voluntary or involuntary bankruptcy proceedings by or against us butthat are not discharged within 90 days. So long as an Events of Default has occurred and is obligatedcontinuing, or if any event which, after notice and/or lapse of time, would reasonably be expected to make purchases frombecome an Event of Default has occurred and is continuing, 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, as we directto terminate the Purchase Agreement upon one business day’s prior written notice to Lincoln Park. In the event of any voluntary or involuntary bankruptcy proceedings by or against us that are not discharged within 90 days, the Purchase Agreement would automatically terminate without any action of us or Lincoln Park. No termination of the Purchase Agreement will be effective during the pendency of any Regular Purchase, Accelerated Purchase or Additional Accelerated Purchase that has not then fully settled in accordance with the Purchase Agreement.

No Short-Selling or Hedging by Lincoln Park

Lincoln Park has represented to us that at no time prior to the time of execution of the Purchase Agreement has Lincoln Park or its agents, representatives or affiliates engaged in or effected, in any manner whatsoever, directly or indirectly, any short sale (as such term is defined in Rule 200 of Regulation SHO under the Exchange Act) of our common stock or any hedging transaction, which establishes a net short position with respect to our common stock. Lincoln Park agreed that during the term of the Purchase Agreement, it, its agents, representatives or affiliates will not enter into or effect, directly or indirectly, any of the foregoing transactions.

Prohibitions on Variable Rate Transactions

There are no limitations on use of proceeds, financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the Purchase Agreement.

Aspire Capital may not assign its rightsAgreement or obligations underRegistration Rights Agreement, except we are prohibited, subject to certain exceptions, until the Purchase Agreement. The Purchase Agreement may be terminated by us at any time, at our discretion, without any penaltylater of May 8, 2026 or cost to us.

Purchase of Shares under the Purchase Agreement

Under the Purchase Agreement, on any trading day selected by us on which the closing sale price of our common stock exceeds $0.25 per share, we may direct Aspire Capital to purchase up to 15,000 shares of our common stock per trading day. The Purchase Price of such shares is equal to the lesser of:

In addition, on any date on which we submit a Purchase Notice to Aspire Capital for the purchase of up to 15,000 shares, we also have the right to direct Aspire Capital to purchase an amount of stock equal to up to 30%36-month anniversary of the aggregate sharesCommencement Date, irrespective of our common stock traded on the Nasdaq Capital Market on the next trading day, subject to the VWAP Purchase Share Volume Maximum and the VWAP Minimum Price Threshold, which is equal to the greater of (a) 80% of the closing price of our common stock on the business day immediately preceding the VWAP Purchase Date or (b) such higher price as set forth by us in the VWAP Purchase Notice. The VWAP Purchase Price of such shares is the lower of:

The Purchase Price will be adjusted for any reorganization, recapitalization, non-cash dividend, stock split, or other similar transaction occurring during the trading day(s) used to compute the Purchase Price. We may deliver multiple Purchase Notices and VWAP Purchase Notices to Aspire Capital from time to time during the termearlier termination of the Purchase Agreement, so long asfrom effecting or entering into any agreement to effect an “equity line of credit” or other substantially similar equity line of credit offering with another third party in which we may offer, issue or sell, and the most recentpurchaser is irrevocably bound to purchase, has been completed.

Minimum Share Price

Under the Purchase Agreement, we and Aspire Capital may not effect any sales of shares of our common stock under the Purchase Agreement on any trading day that the closing sale price of ouror equities convertible or exercisable into common stock is less than $0.25 per share.at a future determined price.

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Events of Default

Generally, Aspire Capital may terminate the Purchase Agreement upon the occurrence of any of the following, among other, events of default:

Our Termination Rights

The Purchase Agreement may be terminated by us at any time, at our discretion, without any penalty or cost to us.

No Short-Selling or Hedging by Aspire Capital

Aspire Capital has agreed that neither it nor any of its agents, representatives and 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.

Effect of Performance of the Purchase Agreement on Our Stockholders

TheAll shares of our common stock being registered for resale hereunder which may be issued or sold by us to Lincoln Park under the Purchase Agreement does not limit the ability of Aspire Capitalare expected to sell any or all of the 6,192,087 shares registered in this offering.be freely tradable. It is anticipated that shares registered in this offering will be sold from time to time over a period of up to approximately 23 months from36-months commencing on the date that the registration statement of which this prospectus. The sale by Aspire Capital ofprospectus forms a significant amountpart becomes effective.

Pursuant to the Purchase Agreement, we will have discretion, subject to market demand, to vary the timing, prices, and numbers of shares registered in this offering at any given time could cause the market pricesold to Lincoln Park. Sales of our common stock, if any, to decline and/orLincoln Park under the Purchase Agreement will depend upon market conditions and other factors to be highly volatile. Aspire Capitaldetermined by us. We may ultimately purchasedecide to sell to Lincoln Park all, some or none of the 6,192,087shares of our common stock that may be available for us to sell to Lincoln Park pursuant to the Purchase Agreement. Because the purchase price per share to be paid by Lincoln Park for the shares of common stock registered inthat we may elect to sell to Lincoln Park under the Purchase Agreement, if any, will fluctuate based on the market prices of our common stock at the time we elect to sell shares to Lincoln Park pursuant to the Purchase Agreement, if any, it is not possible for us to predict, as of the date of this offering. After itprospectus and prior to any such sales, the number of shares of common stock that we will sell to Lincoln Park under the Purchase Agreement, the purchase price per share that Lincoln Park will pay for shares purchased from us under the Purchase Agreement, or the aggregate gross proceeds that we will receive from those purchases by Lincoln Park under the Purchase Agreement.

If and when we do elect to sell shares of our common stock to Lincoln Park pursuant to the Purchase Agreement, after Lincoln Park has acquired such shares, itLincoln Park may sellresell all, some or none of such shares. Therefore,shares at any time or from time to time in its discretion and at different prices. As a result, investors who purchase shares from Lincoln Park in this offering at different times will likely pay different prices for those shares, and so may experience different levels of dilution and in some cases substantial dilution and different outcomes in their investment results. Investors may experience a decline in the value of the shares they purchase from Lincoln Park in this offering as a result of future sales to Aspire Capitalmade by us pursuant to Lincoln Park at prices lower than the prices such investors paid for their shares in this offering.

Moreover, although the Purchase Agreement alsoprovides that we may, result in substantial dilutionour discretion, from time to time after the date of this prospectus and during the term of the Purchase Agreement, direct Lincoln Park to purchase shares of our common stock from us in one or more purchases under the Purchase Agreement, for a maximum aggregate purchase price of up to $26.0 million, only 5,000,000 shares of common stock (599,216 of which represent the Commitment Shares that have been issued by us to Lincoln Park on May 8, 2023, for which we will receive no cash proceeds) are being registered for resale under the registration statement of which this prospectus forms a part.Therefore, only 4,400,784 of such shares of common stockrepresent shares that we may issue and sell to Lincoln Park for cash consideration in purchases under the Purchase Agreement from time to time, at our sole discretion, during the 36-month period commencing on the Commencement Date. If after the Commencement Date we elect to sell to the interestsselling stockholder all of other holdersthe 4,400,784 shares of common stock being registered for resale under this prospectus that are available for sale by us to the selling stockholder in purchases under the Purchase Agreement, depending on the market prices of our common stock. However, we havestock at the righttime of such sales, the actual gross proceeds from the sale of all such shares may be substantially less than the $26.0 million total purchase commitment available to control the timing and amount of any sales of our shares to Aspire Capital andus under the Purchase Agreement, may be terminated bywhich could materially adversely affect our liquidity.

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If it becomes necessary for us at any time at our discretion without any penalty or cost to us.

Percentageissue and sell to Lincoln Park shares of Outstanding Shares after Giving Effectcommon stock in excess of the Exchange Cap under the Purchase Agreement in order to receive aggregate gross proceeds equal to $26.0 million under the Purchased Shares IssuedPurchase Agreement, then for so long as the Exchange Cap continues to Aspire Capital

In connection with entering intoapply to issuances and sales of common stock under the Purchase Agreement, we authorized the salemust first obtain stockholder approval to Aspire Capital of up to $15.0 million of ourissue shares of common stock. However,stock in excess of the Exchange Cap in accordance with applicable Nasdaq listing rules. Furthermore, if we estimateelect to issue and sell to Lincoln Park more than the 4,400,784 shares of our common stock that we willmay elect to issue and sell no more than 6,192,087 shares to Aspire CapitalLincoln Park under the Purchase Agreement all ofthat are being registered for resale by Lincoln Park hereunder, which are included in this offering. Subject to any required

approval by our board of directors, we have the right, but not the obligation, to issuedo, we must first file with the SEC one or more thanadditional registration statements to register under the 6,192,087Securities Act for resale by Lincoln Park such additional shares of our common stock we wish to Aspire Capitalsell from time to time under the Purchase Agreement, under some circumstances. Inwhich the eventSEC must declare effective, in each case before we may elect to issue more than 6,192,087sell any additional shares of our common stock to Lincoln Park under the Purchase Agreement. Any issuance and sale by us under the Purchase Agreement we will be required to fileof a new registration statement and have it declared effective by the SEC. The number of shares ultimately offered for sale by Aspire Capital in this offering is dependent upon the number of shares purchased by Aspire Capital under the Purchase Agreement as well as the price per share at which shares are sold to Aspire Capital under the Purchase Agreement. The following table sets forth the number and percentage of outstanding shares to be held by Aspire Capital after giving effect to the salesubstantial amount of shares of common stock soldin addition to Aspire Capital at varying purchase prices, but assumingthe 4,400,784 shares of common stock that we will notmay elect to issue and sell in excess of 1,099,527 shares of our common stock (which is equal to 19.99% of the common stock outstanding as of April 29, 2020) unless the average price paid for all shares issuedLincoln Park under the Purchase Agreement is equalthat are being registered for resale by Lincoln Park hereunder could cause additional substantial dilution to or greater than $1.89 per share:

_USE OF PROCEEDS

This prospectus relates to shares of our common stock that may be offered and sold from time to time by Aspire Capital. We will not receive any proceeds upon the sale of shares by Aspire Capital. However, we may receive gross proceeds of up to $15.0 million from the sale of shares under the Purchase Agreement to Aspire Capital, including proceeds that we have already received thereunder. As of the date hereof, we have sold approximately $3.3 million of common stock under the Purchase Agreement, and approximately $11.7 million of common stock remains available for sale. The proceeds will be used for the advancement of our research and development activities, working capital and general corporate purposes. This anticipated use of net proceeds from the sale of our common stock to Aspire Capital under the Purchase Agreement represents our intentions based upon our current plans and business conditions.

_SELLING STOCKHOLDERstockholders.

The selling stockholder may from time to time offer and sell any or all of the shares of our common stock set forth below pursuant to this prospectus. When we refer to the “selling stockholder” in this prospectus, we mean the entity listed in the table below, and its respective pledgees, donees, permitted transferees, assignees, successors and others who later come to hold any of the selling stockholder’s interests in shares of our common stock other than through a public sale.

The following table sets forth, as of the date of this prospectus, the name of the selling stockholder for whom we are registering shares for sale to the public, the number of shares of common stock beneficially ownedultimately resold by the selling stockholder prior toLincoln Park through this offering,prospectus is dependent upon the total number of shares of common stock, if any, we elect to issue and sell to Lincoln Park under the Purchase Agreement from and after Commencement and during the term of the Purchase Agreement. Issuances of our common stock to Lincoln Park under the Purchase Agreement will not affect the rights or privileges of our existing stockholders, except that the selling stockholder may offer pursuant to this prospectuseconomic 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 our common stock that our existing stockholders own will not decrease, the selling stockholder will beneficially own after this offering. Except as noted below, the selling stockholder does not have, or within the past three years has not had, any material relationship with us or anyshares of our predecessors or affiliatescommon stock owned by our existing stockholders will represent a smaller percentage of our total outstanding shares of our common stock after any such issuance of shares of our common stock to Lincoln Park under the Purchase Agreement.

The following table sets forth the amount of gross proceeds we would receive from Lincoln Park from our sale of up to 4,400,784 shares of our common stock (which excludes the 599,216 Commitment Shares that we issued to Lincoln Park on May 8, 2023, for which we will receive no cash proceeds) that we are registering hereby that we may issue and sell to Lincoln Park in the selling stockholder is not or was not affiliated with registered broker-dealers.future under the Purchase Agreement at varying purchase prices from and after the Commencement Date:

Based

(1) Although the Purchase Agreement provides that we may sell up to $26.0 million of our common stock to Lincoln Park, we are only registering 5,000,000 shares of our common stock for resale under the registration statement of which this prospectus forms a part, including the 599,216 Commitment Shares that we issued to Lincoln Park on May 8, 2023 in consideration of Lincoln Park’s commitment to purchase shares of our common stock at our direction under the Purchase Agreement, for which we will receive no cash proceeds. Therefore, only 4,400,784 of such shares represent shares that we may issue and sell to Lincoln Park for cash consideration in purchases under the Purchase Agreement from time to time (including pursuant to the Initial Purchase), at our sole discretion, during the 36-month period commencing on the information providedCommencement Date, which may or may not cover all the shares of our common stock we ultimately sell to usLincoln Park under the Purchase Agreement, if any, depending on the purchase price per share. We have included in this column only the 4,400,784 shares that we may issue and sell to Lincoln Park for cash

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consideration in purchases under the Purchase Agreement that are being registered for resale in the offering made by this prospectus (excluding the 599,216 Commitment Shares), giving effect to the Exchange Cap but without regard for the Beneficial Ownership Cap.

(2) The denominator is based on 24,746,044 shares of our common stock outstanding as of May 16, 2023 (which includes the 599,216 Commitment Shares we issued to Lincoln Park on May 8, 2023, promptly following our execution of the Purchase Agreement), adjusted to include the number of shares of our common stock set forth in the adjacent column. The numerator is based on the number of shares of our common stock set forth in the adjacent column.

(3) The closing sale price per share of our common stock on May 18, 2023.

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SELLING STOCKHOLDER

This prospectus relates to the possible resale by the selling stockholder, assumingLincoln Park, of up to 5,000,000 shares of our common stock, consisting of: (i) 599,216 Commitment Shares that we issued to Lincoln Park as consideration for its commitment to purchase shares of our common stock under the selling stockholder sells allPurchase Agreement and (ii) up to 4,400,784 shares of common stock that we have reserved for issuance and sale to Lincoln Park under the Purchase Agreement from time to time from and after the Commencement Date, if and when we determine to sell shares of our common stock to Lincoln Park under the Purchase Agreement.

We are filing the registration statement of which this prospectus forms a part pursuant to the provisions of the Registration Rights Agreement, which we entered into with Lincoln Park on May 8, 2023 concurrently with our execution of the Purchase Agreement, in which we agreed to provide certain registration rights with respect to resales by Lincoln Park of the shares of our common stock beneficially owned by it that have been registered by us and doesor may be issued to Lincoln Park under the Purchase Agreement. The selling stockholder may sell some, all or none of the shares of common stock included in this prospectus. We do not acquire any additional shares during the offering,know how long the selling stockholder will not own any shares, as reflected in the column entitled “Beneficial Ownership After This Offering.” We cannot advise you as to whether the selling stockholder will in fact sell any or all of such shares of common stock. In addition, the selling stockholder may have sold, transferred or otherwise disposed of, or may sell, transfer or otherwise dispose of, at any time and from time to time,hold the shares of our common stock before selling them, and we currently have no agreements, arrangements or understandings with the selling stockholder regarding the sale of any of the shares of common stock. See “Plan of Distribution.”

The table below sets forth, to our knowledge, information concerning the beneficial ownership of shares of our common stock by the selling stockholder as of May 16, 2023. The percentages of shares owned before and after the offering are based on 24,746,044 shares of common stock outstanding as of May 16, 2023, which includes the 599,216 Commitment Shares that we issued to Lincoln Park on May 8, 2023 following our execution of the Purchase Agreement on May 8, 2023. The information in transactions exemptthe table below with respect to the selling stockholder has been obtained from the selling stockholder.

Beneficial ownership is determined in accordance with the rules of the SEC and includes voting or investment power with respect to shares. The inclusion of any shares in this table does not constitute an admission of beneficial ownership for the person named below.

(1) Josh Scheinfeld and Jonathan Cope, the Managing Members of Lincoln Park Capital, LLC, the manager of Lincoln Park Capital Fund, LLC, are deemed to be beneficial owners of all of the shares of common stock owned by Lincoln Park Capital Fund, LLC. Messrs. Cope and Scheinfeld have shared voting and investment power over the shares being offered under this prospectus filed with the SEC in connection with the transactions contemplated under the Purchase Agreement. Neither Lincoln Park Capital, LLC nor Lincoln Park Capital Fund, LLC is a licensed broker dealer or an affiliate of a licensed broker dealer.

(2) Represents the 599,216 Commitment Shares that we issued to Lincoln Park on May 8, 2023 as consideration for its commitment to purchase our common stock at our direction under the Purchase Agreement. In accordance with Rule 13d-3(d) under the Exchange Act, we have excluded from the number of shares of our common stock beneficially owned prior to the offering all of the 4,400,784 shares of our common stock that we may issue and sell to Lincoln Park pursuant to the Purchase Agreement from and after the Commencement Date that are being registered for resale under the registration requirementsstatement of which this prospectus forms a part, because the issuance and sale of such shares to Lincoln Park under the Purchase Agreement is solely at our discretion and is subject to certain conditions, the satisfaction of all of which are outside of Lincoln Park’s control, including the registration statement of which this prospectus forms a part becoming and remaining effective under the Securities Act. Furthermore, under the terms of the Purchase Agreement, issuances and sales of shares of our common stock to Lincoln Park under the Purchase Agreement are subject to certain limitations on the amounts we may sell to Lincoln Park at any time, including the Exchange Cap and the Beneficial Ownership Cap. See the description under the heading “The Lincoln Park Transaction“ for more information about the Purchase Agreement.

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(3) Although the Purchase Agreement provides that we may sell up to $26.0 million of our common stock to Lincoln Park, we are only registering 5,000,000 shares of our common stock for resale under this prospectus, including the 599,216 Commitment Shares that we issued to Lincoln Park on May 8, 2023 as consideration for its commitment to purchase our common stock at our direction under the Purchase Agreement, for which we will receive no cash proceeds. Therefore, only 4,400,784 of such shares represent shares that we may issue and sell to Lincoln Park for cash consideration in purchases under the Purchase Agreement from time to time, at our sole discretion, during the 36-month period commencing on the Commencement Date. 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 full $26.0 million available to us under the Purchase Agreement, including pursuant to the Initial Purchase. If we choose to do so, we must first register for resale under the Securities Act aftersuch additional shares. The number of shares ultimately offered for resale by Lincoln Park is dependent upon the date onnumber of shares we sell to Lincoln Park under the Purchase Agreement.

(4) Assumes the sale of all shares of our common stock registered for resale by the selling stockholder pursuant to the registration statement of which it providedthis prospectus forms a part, although the information set forth in the table below.selling stockholder is under no obligation known to us to sell any shares of common stock at any particular time.

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PLAN OF DISTRIBUTION

The shares of our common stock offered by this prospectus are being offered by the selling stockholder, Lincoln Park. The shares may be sold or distributed from time to time by the selling stockholder directly to one or more purchasers or through brokers, dealers, or underwriters who may act solely as agents at market prices prevailing at the time of sale, at prices related to the prevailing market prices, at negotiated prices, or at fixed prices, which may be changed. The sale of theour common stock offered by this prospectus maycould be effected in one or more of the following methods:

In order to comply with the securities laws of certain states, if applicable, the shares of our common stock offered by this prospectus may be sold only through registered or licensed brokers or dealers. In addition, in certain states, the shares of our common stock offered by this prospectus may not be sold unless they have been registered or qualified for sale in the state or an exemption from the state’s registration or qualification requirement is available and complied with.

Lincoln Park is an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act.

The selling stockholder may transfer the sharesLincoln Park has informed us that it intends to use an unaffiliated broker-dealer to effectuate all sales, if any, of our common stock by other meansthat it has acquired and may in the future acquire from us pursuant to the Purchase Agreement. Such sales will be made at prices and at terms then prevailing or at prices related to the then current market price. Each such unaffiliated broker-dealer will be an underwriter within the meaning of Section 2(a)(11) of the Securities Act. Lincoln Park has informed us that each such broker-dealer will receive commissions from Lincoln Park that will not described in this prospectus.exceed customary brokerage commissions.

Brokers, dealers, underwriters or agents participating in the distribution of the shares as agentsof our common stock offered by this prospectus may receive compensation in the form of commissions, discounts, or concessions from the selling stockholder and/or purchasers, of the common stock for whom the broker-dealers may act as agent. Aspire Capital has informed us that each such broker-dealer will receive commissions from Aspire Capital which will not exceed customary brokerage commissions.

The selling stockholder and its affiliates have agreed not to engage in any direct or indirect short selling or hedgingagent, of shares of our common stock sold by Lincoln Park through this prospectus. The compensation paid to any such particular broker-dealer by any such purchasers of shares of our common stock sold by Lincoln Park may be less than or in excess of customary commissions. Neither we nor Lincoln Park can presently estimate the amount of compensation that any agent will receive from any purchasers of shares of our common stock sold by Lincoln Park.

We know of no existing arrangements between Lincoln Park or any other stockholder, broker, dealer, underwriter or agent relating to the sale or distribution of the shares of our common stock offered by this prospectus.

We may from time to time file with the SEC one or more supplements to this prospectus or amendments to the registration statement of which this prospectus forms a part to amend, supplement or update information contained in this prospectus, including, if and when required under the Securities Act, to disclose certain information relating to a particular sale of shares of our common stock offered by this prospectus by the selling stockholder, including the names of any brokers, dealers, underwriters or agents participating in the distribution of such shares of our common stock by the selling stockholder, any compensation paid by Lincoln Park to any such brokers, dealers, underwriters or agents, and any other required information.

We will pay the expenses incident to the registration under the Securities Act of the offer and sale of the shares of our common stock included in this prospectus by Lincoln Park. We estimate total expenses for the offering will be approximately $120,353.

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We have agreed to indemnify Lincoln Park and certain other persons against certain liabilities in connection with the offering of shares of our common stock offered by this prospectus, including liabilities arising under the Securities Act or, if such indemnity is unavailable, to contribute amounts required to be paid in respect of such liabilities. Lincoln Park has agreed to indemnify us against liabilities under the Securities Act that may arise from certain written information furnished to us by Lincoln Park specifically for use in this prospectus or, if such indemnity is unavailable, to contribute amounts required to be paid in respect of such liabilities.

Lincoln Park has represented to us that at no time prior to the Purchase Agreement has Lincoln Park or its agents, representatives or affiliates engaged in or effected, in any manner whatsoever, directly or indirectly, any short sale (as such term is defined in Rule 200 of Regulation SHO of the Exchange Act) of our common stock or any hedging transaction, which establishes a net short position with respect to our common stock. Lincoln Park agreed that during the term of the Purchase Agreement.

The selling stockholder is an “underwriter” within the meaningAgreement, it, its agents, representatives or affiliates will not enter into or effect, directly or indirectly, any of the Securities Act. We have agreed to provide indemnification and contribution to the selling stockholder against certain civil liabilities, including liabilities under the Securities Act.foregoing transactions.

We have advised the selling stockholderLincoln Park that while it is engaged in a distribution of the shares included in this prospectus, it is required to comply with Regulation M promulgated under the Exchange Act. With certain exceptions, Regulation M precludes the selling stockholder, any affiliated purchasers, and any broker-dealer or other person who participates in the distribution from bidding for or purchasing, or attempting to induce any person to bid for or purchase any security which is the subject of the distribution until the entire distribution is complete. Regulation M also prohibits any bids or purchases made in order to stabilize the price of a security in connection with the distribution of that security. All of the foregoing may affect the marketability of the sharessecurities offered herebyby this prospectus.

We may suspend the sale of shares by the selling stockholder pursuant to this prospectus for certain periods of time for certain reasons, including if the prospectus is required to be supplemented or amended to include additional material information.

This offering as it relates to Aspire Capital will terminate on the date that all shares of our common stock offered by this prospectus have been sold by Aspire Capital.Lincoln Park.

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LEGAL MATTERS

The validity of the common stock offered hereby is being passed upon for us by Cooley LLP, San Diego, California.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2019,2022, as set forth in their report (which contains an explanatory paragraph describing conditions that raise substantial doubt about the Company’s ability to continue as a going concern as described in Note 1 to the consolidated financial statements), which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our consolidated financial statements are incorporated by reference in reliance on Ernst & Young LLP’s report, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-1 under the Securities Act, with respect to the common stock being offered by this prospectus. This prospectus does not contain all of the information in the registration statement and its exhibits. For further information with respect to us and the securities offered by this prospectus, we refer you to the registration statement and its exhibits. Statements contained in this prospectus as to the contents of any contract or any other document referred to are not necessarily complete, and in each instance, we refer you to the copy of the contract or other document filed as an exhibit to the registration statement. Each of these statements is qualified in all respects by this reference.

We are subject to the information and periodic reporting requirements of the Exchange Act, and we file periodicannual, quarterly and current reports, proxy statements and other information with the SEC. The SEC maintains a website that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC, including us. The address of the SEC website is www.sec.gov. You can read our SEC filings, including the registration statement, over the Internet at the SEC’s website at www.sec.gov.such address. You may also request a copy of these filings, at no cost, by writing us at 4350 La Jolla Village Drive, Suite 800, San Diego, California 92122 or telephoning us at (858) 550-0780.

We also maintain a website at www.traconpharma.com, at which you may access these materials free of charge after theythey are electronically filed with, or furnished to, the SEC. The information contained in, or that can be accessed through, our website is not incorporated by reference in, and is not part of, this prospectus.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate“incorporate by reference”reference” information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The SEC file number for the documents incorporated by reference in this prospectus is 001-36818. The information incorporated by reference is considered to be part of this prospectus.

We incorporate by reference into this prospectus and the registration statement of which this prospectus formforms a part the information or documents listed below that we have filed with the SEC, and any future filings we will make with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act after the date of the initial filing of the registration statement of which this prospectus isforms a part and prior to effectiveness of such registration statement, and until the termination of the offering of the shares covered by this prospectus (other than information furnished under Item 2.02 or Item 7.01 of any current reports on Form 8-K):