Common Stock	12 Months Ended
Dec. 31, 2020
Common Stock
Common Stock	8. Common Stock Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to the preferential dividend rights of the preferred stockholders. Through December 31, 2020, no dividends have been declared for shares of common stock. Public Offering of Common Stock—February 2019 On February 5, 2019, the Company completed the 2019 Public Offering whereby the Company issued 7,557,142 shares of its common stock at a price of $1.75 per share, which included 985,714 shares issued pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock, each share issued with a warrant to purchase one share of common stock. Each warrant has an exercise price of $1.95 per share with an exercise period expiring seven years from the date of issuance. The aggregate net proceeds received by the Company from the 2019 Public Offering were approximately $12,122, net of underwriting discounts and commissions and estimated offering expenses payable by the Company. Issuance of Common Stock under Distribution Agreement—2019 On September 7, 2018, the Company filed a Prospectus Supplement to register the offer and sale of shares of common stock having an aggregate offering price of up to $30,000 pursuant to the terms of a distribution agreement, or the Distribution Agreement, with Raymond James & Associates, Inc. During the year ended December 31, 2019, the Company issued 1,033,147 shares under the Distribution Agreement, for net proceeds of $1,923. In June 2020, the Company terminated the Distribution Agreement and did not issue any shares under the Distribution Agreement during the year ended December 31, 2020. Lincoln Park Purchase Agreements On July 10, 2019, the Company entered into a Commitment Purchase Agreement and a Registration Rights Agreement with Lincoln Park, pursuant to which the Company has the right to sell to Lincoln Park up to $20,000 in shares of its common stock, $0.001 par value per share, subject to certain limitations and conditions set forth in the Commitment Purchase Agreement. As consideration for Lincoln Park’s commitment to purchase shares of common stock pursuant to the Commitment Purchase Agreement, the Company issued to Lincoln Park 330,000 shares of common stock. The Company did not receive any cash proceeds from the issuance of such shares. During the year ended December 31, 2020, the Company did not issue any shares under the Commitment Purchase Agreement. On July 11, 2019, the Company entered into a Registered Offering Purchase Agreement, under which the Company agreed to sell to Lincoln Park, and Lincoln Park agreed to purchase 571,429 shares of common stock, at a price of $1.75 per share for an aggregate purchase price of $1,000. January 2020 Private Placement On January 3, 2020, the Company issued and sold 1,421,801 shares of its Series A Preferred Stock at a purchase price of $10.54 per share, 1,137,442 shares of its Series B Preferred Stock at a purchase price of $10.55 per share, and one (1) share of its Special Voting Stock, entitling the purchaser of Series A Preferred Stock to elect one member of the Company’s board of directors, for aggregate net proceeds to the Company of approximately $25,322. On March 5, 2020, the Company’s stockholders approved the conversion of the Series A Preferred Stock into a pre-funded warrant to purchase 14,413,902 shares of common stock at an exercise price of $0.001 per share and the conversion of the Series B Preferred Stock into 11,531,133 shares of its common stock, par value $0.001 per share. Each investor also received the Coverage Warrants to purchase an equal number of shares at an exercise price of $2.11 per share. In connection with the January 2020 Private Placement, Series A Preferred Stock holders and Series B Preferred Stock holders were entitled to cash dividends at a fixed cumulative percentage of 8% per annum plus any dividends declared on outstanding common stock on an as-converted basis, effective on the issuance date of the Series A Preferred Stock and Series B Preferred Stock. The cash dividends were converted to shares of common stock upon the conversion of the Series A Preferred Stock to pre-funded warrants and Series B Preferred Stock to common stock. During the year ended December 31, 2020, the Company recorded $372 of Series A Preferred Stock and Series B Preferred Stock dividends, which qualify as cumulative dividends, and in the calculation of EPS are subtracted from net income in arriving at income attributable to common stockholders. The Company determined that the embedded conversion features of the Series A Preferred Stock and Series B Preferred Stock to receive the Coverage Warrants each met the definition of a contingent beneficial conversion feature and should be accounted for separately as a derivative. The recognition of the beneficial conversion feature occurred upon the conversion of the Series A Preferred Stock into pre-funded warrants and Series B Preferred Stock into common stock and the issuance of the Coverage Warrants. The Company measured the contingent beneficial conversion features’ intrinsic values on January 3, 2020 and determined that the beneficial conversion features were valued at $5,226 for Series A and $4,173 for Series B, respectively. Upon conversion, the discount originated by the contingent beneficial conversion feature, at its intrinsic value for Series A Preferred Stock and Series B Preferred Stock, was immediately recognized as a dividend. The dividend is reflected as an adjustment to basic and diluted net loss per share attributable to common stockholders. Public Offering of Common Stock — June 2020 On June 22, 2020, the Company completed the 2020 Public Offering, whereby the Company issued 20,250,000 shares of its common stock at $2.00 per share and, in lieu of common stock, issued certain investors 2,250,000 of its June 2020 Pre-funded Warrants. The June 2020 Pre-funded Warrants have an exercise price of $0.001 per share, expire on June 22, 2027 and qualify for equity classification. On June 25, 2020, the underwriters exercised their right to purchase 3,375,000 additional shares of the Company’s common stock at the public offering price per share of common stock, less underwriting discounts and commissions. The aggregate net proceeds received by the Company from the 2020 Public Offering were approximately $48,276, net of underwriting discounts and commissions and offering expenses payable by the Company.

8. Common Stock

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to the preferential dividend rights of the preferred stockholders. Through December 31, 2020, no dividends have been declared for shares of common stock.

Public Offering of Common Stock—February 2019

On February 5, 2019, the Company completed the 2019 Public Offering whereby the Company issued 7,557,142 shares of its common stock at a price of $1.75 per share, which included 985,714 shares issued pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock, each share issued with a warrant to purchase one share of common stock. Each warrant has an exercise price of $1.95 per share with an exercise period expiring seven years from the date of issuance. The aggregate net proceeds received by the Company from the 2019 Public Offering were approximately $12,122, net of underwriting discounts and commissions and estimated offering expenses payable by the Company.

Issuance of Common Stock under Distribution Agreement—2019

On September 7, 2018, the Company filed a Prospectus Supplement to register the offer and sale of shares of common stock having an aggregate offering price of up to $30,000 pursuant to the terms of a distribution agreement, or the Distribution Agreement, with Raymond James & Associates, Inc. During the year ended December 31, 2019, the Company issued 1,033,147 shares under the Distribution Agreement, for net proceeds of $1,923. In June 2020, the Company terminated the Distribution Agreement and did not issue any shares under the Distribution Agreement during the year ended December 31, 2020.

Lincoln Park Purchase Agreements

On July 10, 2019, the Company entered into a Commitment Purchase Agreement and a Registration Rights Agreement with Lincoln Park, pursuant to which the Company has the right to sell to Lincoln Park up to $20,000 in shares of its common stock, $0.001 par value per share, subject to certain limitations and conditions set forth in the Commitment Purchase Agreement. As consideration for Lincoln Park’s commitment to purchase shares of common stock pursuant to the Commitment Purchase Agreement, the Company issued to Lincoln Park 330,000 shares of common stock. The Company did not receive any cash proceeds from the issuance of such shares. During the year ended December 31, 2020, the Company did not issue any shares under the Commitment Purchase Agreement.

On July 11, 2019, the Company entered into a Registered Offering Purchase Agreement, under which the Company agreed to sell to Lincoln Park, and Lincoln Park agreed to purchase 571,429 shares of common stock, at a price of $1.75 per share for an aggregate purchase price of $1,000.

January 2020 Private Placement

On January 3, 2020, the Company issued and sold 1,421,801 shares of its Series A Preferred Stock at a purchase price of $10.54 per share, 1,137,442 shares of its Series B Preferred Stock at a purchase price of $10.55 per share, and one (1) share of its Special Voting Stock, entitling the purchaser of Series A Preferred Stock to elect one member of the Company’s board of directors, for aggregate net proceeds to the Company of approximately $25,322.

On March 5, 2020, the Company’s stockholders approved the conversion of the Series A Preferred Stock into a pre-funded warrant to purchase 14,413,902 shares of common stock at an exercise price of $0.001 per share and the conversion of the Series B Preferred Stock into 11,531,133 shares of its common stock, par value $0.001 per share. Each investor also received the Coverage Warrants to purchase an equal number of shares at an exercise price of $2.11 per share.

In connection with the January 2020 Private Placement, Series A Preferred Stock holders and Series B Preferred Stock holders were entitled to cash dividends at a fixed cumulative percentage of 8% per annum plus any dividends declared on outstanding common stock on an as-converted basis, effective on the issuance date of the Series A Preferred Stock and Series B Preferred Stock. The cash dividends were converted to shares of common stock upon the conversion of the Series A Preferred Stock to pre-funded warrants and Series B Preferred Stock to common stock. During the year ended December 31, 2020, the Company recorded $372 of Series A Preferred Stock and Series B Preferred Stock dividends, which qualify as cumulative dividends, and in the calculation of EPS are subtracted from net income in arriving at income attributable to common stockholders.

The Company determined that the embedded conversion features of the Series A Preferred Stock and Series B Preferred Stock to receive the Coverage Warrants each met the definition of a contingent beneficial conversion feature and should be accounted for separately as a derivative. The recognition of the beneficial conversion feature occurred upon the conversion of the Series A Preferred Stock into pre-funded warrants and Series B Preferred Stock into common stock and the issuance of the Coverage Warrants. The Company measured the contingent beneficial conversion features’ intrinsic values on January 3, 2020 and determined that the beneficial conversion features were valued at $5,226 for Series A and $4,173 for Series B, respectively. Upon conversion, the discount originated by the contingent beneficial conversion feature, at its intrinsic value for Series A Preferred Stock and Series B Preferred Stock, was immediately recognized as a dividend. The dividend is reflected as an adjustment to basic and diluted net loss per share attributable to common stockholders.

Public Offering of Common Stock — June 2020

On June 22, 2020, the Company completed the 2020 Public Offering, whereby the Company issued 20,250,000 shares of its common stock at $2.00 per share and, in lieu of common stock, issued certain investors 2,250,000 of its June 2020 Pre-funded Warrants. The June 2020 Pre-funded Warrants have an exercise price of $0.001 per share, expire on June 22, 2027 and qualify for equity classification.

On June 25, 2020, the underwriters exercised their right to purchase 3,375,000 additional shares of the Company’s common stock at the public offering price per share of common stock, less underwriting discounts and commissions. The aggregate net proceeds received by the Company from the 2020 Public Offering were approximately $48,276, net of underwriting discounts and commissions and offering expenses payable by the Company.