Stockholders' Equity	12 Months Ended
Dec. 31, 2019
Stockholders' Equity
Stockholders' Equity	10. Stockholders’ Equity Common Stock Each holder of common stock shall be entitled to one vote for each share of common stock held of record by such holder on all matters on which stockholders generally are entitled to vote. Common stockholders are entitled to receive dividends when and if declared by the board of directors, out of any funds legally available. As of December 31, 2019, no dividends have been declared or paid. Initial Public Offering On September 28, 2018, the Company completed an initial public offering in which the Company issued and sold 5,000,000 shares of its common stock, at a public offering price of $15.00 per share, for gross proceeds of $75.0 million. The Company received approximately $65.6 million in net proceeds after deducting underwriting discounts and commissions and offering costs. In connection with this financing, all outstanding shares of Preferred Stock, including accrued dividends, converted into 8,084,414 shares of the Company’s common stock. Aspire Common Stock Purchase Agreement In October 2019, the Company entered into a common stock purchase agreement, or CSPA, with Aspire Capital Fund, LLC, or Aspire, which provided that, upon the terms and subject to the conditions and limitations set forth therein, Aspire is committed to purchase up to an aggregate of $20.0 million of shares of the Company’s common stock over the 30-month term of the CSPA. Under the CSPA, on any trading day selected by the Company on which the closing price of its common stock is equal to or greater than $0.25 per share, the Company has the right, in its sole discretion, to present Aspire with a purchase notice directing Aspire to purchase up to 50,000 shares of common stock per business day, at a purchase price equal to the lesser of the lowest sale price of common stock on the purchase date, or the arithmetic average of the three lowest closing sale prices during the 10 consecutive business days ending on the trading day immediately preceding the purchase date. The Company and Aspire also may mutually agree to increase the number of shares that may be sold to as much as 2,000,000 shares per business day. In addition, on any date on which the Company submits a purchase notice to Aspire in an amount equal to 50,000 shares, the Company also has the right, in its sole discretion, to present Aspire with a volume-weighted average price purchase notice, or the VWAP Purchase Notice, directing Aspire to purchase an amount of stock equal to up to 30% of the aggregate shares of the Company’s common stock traded on its principal market on the next trading day, or the VWAP Purchase Date, subject to a maximum number of shares the Company may determine. The purchase price per share pursuant to such VWAP Purchase Notice is generally 97% of the volume-weighted average price for the Company’s common stock traded on its principal market on the VWAP Purchase Date. The Company controls the timing and amount of any sales to Aspire, and is not limited with respect to use of proceeds or by any financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the CSPA. The CSPA may be terminated by the Company at any time, at its discretion, without any cost to the Company. Aspire has no trading volume requirements or restrictions, and has no right to require any sales by the Company but is obligated to make purchases as directed by the Company in accordance with the CSPA. Aspire 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 common stock during any time prior to the termination of the CSPA. As consideration for Aspire’s obligation under the CSPA, the Company issued 104,167 shares of common stock to Aspire as a commitment fee, or the Commitment Shares. This $0.6 million commitment fee and $0.1 million in other transaction costs were deferred and will be charged against the gross proceeds received upon exercise by the Company as costs of equity financing within additional paid-in capital. The CSPA further provides that the number of shares that may be sold pursuant to the CSPA will be limited to 2,626,165 shares, including the Commitment Shares, which represents 19.99% of the Company’s outstanding shares of common stock as of October 21, 2019, unless stockholder approval is obtained to issue more than 19.99%. This limitation will not apply under certain circumstances specified in the CSPA. As of December 31, 2019, 50,000 shares had been purchased by Aspire pursuant to the CSPA resulting in gross proceeds of $0.3 million. Concurrently with entering into the CSPA, the Company also entered into a registration rights agreement with Aspire, pursuant to which the Company filed with the SEC a prospectus supplement to the Company’s effective shelf registration statement on Form S-3 (File No. 333-234041), registering all of the shares of common stock that may be offered to Aspire from time to time under the CSPA, including the Commitment Shares.

10. Stockholders’ Equity

Common Stock

Each holder of common stock shall be entitled to one vote for each share of common stock held of record by such holder on all matters on which stockholders generally are entitled to vote. Common stockholders are entitled to receive dividends when and if declared by the board of directors, out of any funds legally available. As of December 31, 2019, no dividends have been declared or paid.

Initial Public Offering

On September 28, 2018, the Company completed an initial public offering in which the Company issued and sold 5,000,000 shares of its common stock, at a public offering price of $15.00 per share, for gross proceeds of $75.0 million. The Company received approximately $65.6 million in net proceeds after deducting underwriting discounts and commissions and offering costs. In connection with this financing, all outstanding shares of Preferred Stock, including accrued dividends, converted into 8,084,414 shares of the Company’s common stock.

Aspire Common Stock Purchase Agreement

In October 2019, the Company entered into a common stock purchase agreement, or CSPA, with Aspire Capital Fund, LLC, or Aspire, which provided that, upon the terms and subject to the conditions and limitations set forth therein, Aspire is committed to purchase up to an aggregate of $20.0 million of shares of the Company’s common stock over the 30-month term of the CSPA. Under the CSPA, on any trading day selected by the Company on which the closing price of its common stock is equal to or greater than $0.25 per share, the Company has the right, in its sole discretion, to present Aspire with a purchase notice directing Aspire to purchase up to 50,000 shares of common stock per business day, at a purchase price equal to the lesser of the lowest sale price of common stock on the purchase date, or the arithmetic average of the three lowest closing sale prices during the 10 consecutive business days ending on the trading day immediately preceding the purchase date. The Company and Aspire also may mutually agree to increase the number of shares that may be sold to as much as 2,000,000 shares per business day.

In addition, on any date on which the Company submits a purchase notice to Aspire in an amount equal to 50,000 shares, the Company also has the right, in its sole discretion, to present Aspire with a volume-weighted average price purchase notice, or the VWAP Purchase Notice, directing Aspire to purchase an amount of stock equal to up to 30% of the aggregate shares of the Company’s common stock traded on its principal market on the next trading day, or the VWAP Purchase Date, subject to a maximum number of shares the Company may determine. The purchase price per share pursuant to such VWAP Purchase Notice is generally 97% of the volume-weighted average price for the Company’s common stock traded on its principal market on the VWAP Purchase Date.

The Company controls the timing and amount of any sales to Aspire, and is not limited with respect to use of proceeds or by any financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the CSPA. The CSPA may be terminated by the Company at any time, at its discretion, without any cost to the Company. Aspire has no trading volume requirements or restrictions, and has no right to require any sales by the Company but is obligated to make purchases as directed by the Company in accordance with the CSPA. Aspire 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 common stock during any time prior to the termination of the CSPA.

As consideration for Aspire’s obligation under the CSPA, the Company issued 104,167 shares of common stock to Aspire as a commitment fee, or the Commitment Shares. This $0.6 million commitment fee and $0.1 million in other transaction costs were deferred and will be charged against the gross proceeds received upon exercise by the Company as costs of equity financing within additional paid-in capital.

The CSPA further provides that the number of shares that may be sold pursuant to the CSPA will be limited to 2,626,165 shares, including the Commitment Shares, which represents 19.99% of the Company’s outstanding shares of common stock as of October 21, 2019, unless stockholder approval is obtained to issue more than 19.99%. This limitation will not apply under certain circumstances specified in the CSPA. As of December 31, 2019, 50,000 shares had been purchased by Aspire pursuant to the CSPA resulting in gross proceeds of $0.3 million.

Concurrently with entering into the CSPA, the Company also entered into a registration rights agreement with Aspire, pursuant to which the Company filed with the SEC a prospectus supplement to the Company’s effective shelf registration statement on Form S-3 (File No. 333-234041), registering all of the shares of common stock that may be offered to Aspire from time to time under the CSPA, including the Commitment Shares.