Stockholders' Equity | 8 . Stockholders’ Equity Authorized, Issued, and Outstanding Common Stock The Company’s authorized common stock has a par value of $0.001 per share and consists of 100,000,000 shares as of June 30, 2022, and December 31, 2021; 32,596,403 and 28,705,334 shares were issued and outstanding at June 30, 2022, and December 31, 2021, respectively. The following table summarizes common stock share activity for the three and six months ended June 30, 2022 and 2021 (dollars in thousands): Three Months Ended June 30, 2022 Shares of Common Stock Common Stock Additional Paid-in Capital Accumulated Deficit Total Stockholders’ Equity Balance, March 31, 2022 29,221,158 $ 32 $ 403,825 $ (364,930 ) $ 38,927 Net loss — — — (13,345 ) (13,345 ) Stock-based compensation expense — — 1,100 — 1,100 Common stock issued, net of expenses 3,358,333 4 18,794 — 18,798 Common stock issued for vested restricted stock units 16,912 — — — — Balance, June 30, 2022 32,596,403 $ 36 $ 423,719 $ (378,275 ) $ 45,480 Three Months Ended June 30, 2021 Shares of Common Stock Common Stock Additional Paid-in Capital Accumulated Deficit Total Stockholders’ Equity Balance, March 31, 2021 20,625,637 $ 21 $ 357,192 $ (331,289 ) $ 25,924 Net income — — — 1,658 1,658 Stock-based compensation expense — — 542 — 542 Common stock issued, net of expenses 2,516,802 5 3,410 — 3,415 Common stock issued for vested restricted stock units 5,113 — 15 — 15 Vested Loan Agreement warrants — — 766 — 766 Balance, June 30, 2021 23,147,552 $ 26 $ 361,925 $ (329,631 ) $ 32,320 Six Months Ended June 30, 2022 Shares of Common Stock Common Stock Additional Paid-in Capital Accumulated Deficit Total Stockholders’ Equity Balance, December 31, 2021 28,705,334 $ 32 $ 400,705 $ (359,479 ) $ 41,258 Net loss — — — (18,796 ) (18,796 ) Stock-based compensation expense — — 2,022 — 2,022 Common stock issued through employee stock purchase plan 3,120 — 10 — 10 Common stock issued, net of expesnes 3,845,943 4 20,911 — 20,915 Common stock issued for vested restricted stock units 42,006 — — — — Vested Loan Agreement warrants — — 71 — 71 Balance, June 30, 2022 32,596,403 $ 36 $ 423,719 $ (378,275 ) $ 45,480 Six Months Ended June 30, 2021 Shares of Common Stock Common Stock Additional Paid-in Capital Accumulated Deficit Total Stockholders’ Equity Balance, December 31, 2020 19,663,698 $ 20 $ 349,351 $ (326,613 ) $ 22,758 Net loss — — — (3,018 ) (3,018 ) Stock-based compensation expense — — 940 — 940 Common stock issued through employee stock purchase plan 2,184 — 9 — 9 Common stock issued, net of expenses 2,516,802 5 3,407 — 3,412 Common stock issued for conversion of April 2020 Notes 959,080 1 7,452 — 7,453 Common stock issued for vested restricted stock units 5,788 — — — — Vested Loan Agreement warrants — — 766 — 766 Balance, June 30, 2021 23,147,552 $ 26 $ 361,925 $ (329,631 ) $ 32,320 Shares Reserved for Future Issuance The Company had reserved shares of common stock for future issuance as follows: June 30, 2022 December 31, 2021 Outstanding stock options 2,129,002 1,542,126 Outstanding restricted stock units 1,024,929 133,834 Warrants to purchase common stock associated with March 2018 public offering – Series 2 798,810 798,810 Warrants to purchase common stock associated with December 2020 public offering - Series 2 6,800,000 6,800,000 Prefunded warrants to purchase common stock associated with December 2020 public offering 3,200,000 3,200,000 Warrants to purchase common stock associated with April 2022 Public Offering 15,000,000 — Prefunded warrants to purchase common stock associated with April 2022 Public Offering 11,666,667 — Warrants to purchase common stock associated with Loan Agreement 198,819 170,410 Warrant to purchase common stock associated with Danforth 50,000 50,000 For possible future issuance for the conversion of the March 2019 Notes 1,138,200 1,138,200 For possible future issuance under 2014 Plan (Note 9) 34,206 295,220 For possible future issuance under employee stock purchase plan 3,714 3,893 For possible future issuance under 2015 Plan (Note 9) 124,250 235,000 Total common shares reserved for future issuance 42,168,597 14,367,493 April 2022 Public Offering On April 22, 2022, the Company entered into an Equity Underwriting Agreement (the “Underwriting Agreement”) with Guggenheim Securities, LLC, as representative of the several underwriters (the “Underwriters”), relating to the offering, issuance and sale (the “April 2022 Public Offering”) of (a) seven-year term and an exercise price of $ The prefunded warrants are classified as equity in accordance with ASC 815, Derivatives and Hedging Common Stock Purchase Agreement and Sales Agreement On April 10, 2020, the Company entered into the Common Stock Purchase Agreement with Aspire Capital (the “Common Stock Purchase Agreement”) pursuant to which the Company has the right to sell to Aspire Capital from time to time in its sole discretion up to $20.0 million in shares of the Company’s common stock over the next 30 months, subject to certain limitations and conditions set forth in the Common Stock Purchase Agreement. During the three and six months ended June 30, 2022, the Company sold zero and 375,000 of its common stock under the Common Stock Purchase Agreement for gross proceeds of zero and $1.5 million, respectively, and the Company did not sell any shares of common stock under the Common Stock Purchase Agreement in the comparable prior year periods. During the three and six months ended June 30, 2022, the Company sold zero and 137,610 shares of its common stock and received net proceeds of zero and $0.7 million, respectively, under the SM with and . During the three and six months ended June 30, 2021, the Company sold 96,668 shares of its common stock and received net proceeds of $0.8 million under the Warrants Associated with the March 2018, December 2020 and April 2022 Public Offerings The outstanding warrants associated with the March 2018 and December 2020 public offerings contain a provision where the warrant holder has the option to receive cash, equal to the Black-Scholes fair value of the remaining unexercised portion of the warrant, as cash settlement in the event that there is a fundamental transaction (contractually defined to include various merger, acquisition or stock transfer activities). Due to this provision, ASC 480, Distinguishing Liabilities from Equity, The outstanding warrants associated with the April 2022 public offering meet the definition of a derivative pursuant to ASC 815, Derivatives and Hedging , and do not meet the derivative scope exception given the warrants do not qualify under the indexation guidance. As a result, the April 2022 public offering warrants were initially recognized as liabilities and measured at fair value using the Black-Scholes valuation model. Issuance costs of $1.7 million initially allocated to the April 2022 public offering warrants were written off and recognized in the warrant liabilities fair value adjustment in the three and six months ended June 30, 2022. Warrants Associated with Loan Agreement In connection with the entry into the Loan Agreement, the Company issued to each of Hercules and SVB a warrant (collectively, the “Warrants”) to purchase shares of the Company’s common stock, par value $0.001 per share (the “Shares”). The amount of shares that may be purchased for the Warrants, collectively between Hercules and SVB, will not exceed 0.04 multiplied by the aggregate amount of the term loan advances, divided by the exercise price of the Warrants. At the closing of the Loan Agreement, the Company issued 113,607 warrants to purchase shares of the Company’s common stock and recognized the initial warrants at their relative fair value in shareholder's equity. Upon the funding of the $ 10.0 million and $ 5.0 million for the second and third tranches in June 2021 and March 2022, respectively, the associated warrant liabilities of $ 0.3 million and $ 0.1 million, respectively, were reclassed to additional paid in capital at settlement. In June 2021 and March 2022, 56,803 and 28,409 warrants to purchase shares of the Company’s common stock were issued upon vesting of the second and third tranches, respectively. |