Stockholders’ Equity	9 Months Ended
Sep. 30, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock As of September 30, 2020 and December 31, 2019, there were 2,000,000 shares of preferred stock, $0.0001 par value per share, authorized and no shares of preferred stock issued or outstanding. Common Stock As of September 30, 2020 and December 31, 2019, there were 170,000,000 shares of common stock, $0.0001 par value per share, authorized and 93,573,165 and 65,378,890 shares issued and outstanding, respectively. Controlled Equity Offering (or "At the Market" Offering) On March 22, 2019, the Company entered into a sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (the “Agent”), pursuant to which the Company may offer and sell from time to time shares of the Company’s common stock through the Agent. The offering and sale of up to $40.0 million of the shares has been registered under the Securities Act of 1933, as amended (the "Securities Act"), pursuant to the Company’s registration statement on Form S-3 (File No. 333-227363), which was originally filed with the SEC on September 14, 2018 and declared effective by the SEC on October 1, 2018, the base prospectus contained within the registration statement, and a prospectus supplement that was filed with the SEC on March 22, 2019. Sales of the shares, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an “at the market" offering as defined in Rule 415(a) of the Securities Act, including sales made directly through the Nasdaq Global Market or on any other existing trading market for the Company’s common stock. The Company intends to use the proceeds from the offering for working capital and other general corporate purposes. The Company may suspend or terminate the Sales Agreement at any time. During the year ended December 31, 2019, the Company sold 1,840,443 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $5,383,079, at a weighted average selling price of approximately $2.92. The Company paid $309,479 in commissions and offering fees related to the sale of the common stock. For the nine months ended September 30, 2020, the Company sold 1,128,608 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $2,325,478, at a weighted average selling price of approximately $2.06. The Company paid $63,000 in commissions and offering fees related to the sale of common stock. Approximately $32.3 million remains available for sale under this facility. We are not required to sell any shares at any time during the term of the facility. Our ability to sell common stock under the facility may be limited by several factors including, among other things, the trading volume of our common stock and certain black-out periods that we may impose upon the facility, among other things. Public Offering of Common Stock On February 4, 2020, the Company entered into an underwriting agreement with Cantor Fitzgerald & Co., as underwriter, pursuant to which the Company agreed to issue and sell an aggregate of up to 3,670,212 shares of its common stock, which included 478,723 optional shares that may be sold pursuant to an over-allotment option granted to the underwriters. On February 6, 2020, the Company closed the sale of 3,191,489 shares of its common stock at the public offering price of $2.22 per share (the "Offering"). On February 19, 2020, the underwriter exercised its over-allotment option to purchase an additional 478,723 shares at a price of $2.22 per share, which closed on February 21, 2020. The Company raised a total of $8.0 million, net of issuance costs of $0.1 million, relating to the sale of the common stock in the Offering. The Offering was made pursuant to the Company’s effective Registration Statement on Form S-3 (File No. 333-227363), which was previously filed with the SEC. On September 23, 2020, the Company entered into a Securities Purchase Agreement (the “2020 Purchase Agreement”) with certain purchasers named therein, pursuant to which the Company agreed to issue and sell to several institutional and accredited investors in a registered direct offering, 21,818,544 shares of common stock and warrants to purchase up to 23,178,509 shares of common stock (the “Warrants”) at a combined purchase price equal to $1.51 per share. Each Warrant is exercisable for one share of common stock at an exercise price of $1.80 per share. The Warrants are immediately exercisable and will expire on September 25, 2022. The Company also offered to certain purchasers pre-funded warrants to purchase up to an aggregate of 1,360,265 shares of common stock (the “Pre-Funded Warrants”), in lieu of shares of common stock. The purchase price of each Pre-Funded Warrant is equal to the price at which a share of common stock is sold to the public in the offering, minus $0.001, and the exercise price of each Pre-Funded Warrant is $0.001 per share. The Pre-Funded Warrants were exercised in conjunction with the issuance of common stock under the Securities Purchase Agreement. The Company received gross proceeds of approximately $35.0 million in connection with the offering, before deducting placement agent fees and related offering expenses of approximately $2.3 million. A holder (together with its affiliates) may not exercise any portion of the Warrant to the extent that the holder would own more than 9.99% (or, at the holder’s option upon issuance, 4.99%) of the Company’s outstanding common stock immediately after exercise, as such percentage ownership is determined in accordance with the terms of the Warrant or Pre-Funded Warrant. The Company agreed to pay H.C. Wainwright & Co., LLC (the "Placement Agent") a cash fee of 6.0% of the aggregate gross proceeds raised in the offering, minus $420,000 payable by the Company to a financial advisory firm for services related to the offering. In addition, the Company agreed to pay the Placement Agent (i) 6.0% of the aggregate gross proceeds to be received, if any, from the cash exercise of any Warrants through December 25, 2021 and (ii) 4.0% of the aggregate gross proceeds to be received, if any, from the cash exercise of any Warrants subsequent to December 25, 2021. The Company also agreed to pay the Placement Agent non-accountable expenses of $50,000 as well as $12,900 for the clearing fees of the Placement Agent in connection with the offering. The Company has accounted for the common stock for the 2020 Purchase Agreement as equity on the accompanying consolidated balance sheets as of September 30, 2020. The amount allocated to common stock was $26.1 million. This allocation is equal to the total proceeds of $35.0 million less the amount allocated to Warrants of $8.9 million and is also net of the direct and incremental costs associated with the 2020 Purchase Agreement of $2.3 million. The Black-Scholes pricing model was used to calculate the value of Warrants relating to the 2020 Purchase Agreement.

As of September 30, 2020 and December 31, 2019, there were 2,000,000 shares of preferred stock, $0.0001 par value per share, authorized and no shares of preferred stock issued or outstanding.

As of September 30, 2020 and December 31, 2019, there were 170,000,000 shares of common stock, $0.0001 par value per share, authorized and 93,573,165 and 65,378,890 shares issued and outstanding, respectively.

On March 22, 2019, the Company entered into a sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (the “Agent”), pursuant to which the Company may offer and sell from time to time shares of the Company’s common stock through the Agent. The offering and sale of up to $40.0 million of the shares has been registered under the Securities Act of 1933, as amended (the "Securities Act"), pursuant to the Company’s registration statement on Form S-3 (File No. 333-227363), which was originally filed with the SEC on September 14, 2018 and declared effective by the SEC on October 1, 2018, the base prospectus contained within the registration statement, and a prospectus supplement that was filed with the SEC on March 22, 2019.

Sales of the shares, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an “at the market" offering as defined in Rule 415(a) of the Securities Act, including sales made directly through the Nasdaq Global Market or on any other existing trading market for the Company’s common stock. The Company intends to use the proceeds from the offering for working capital and other general corporate purposes. The Company may suspend or terminate the Sales Agreement at any time.

During the year ended December 31, 2019, the Company sold 1,840,443 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $5,383,079, at a weighted average selling price of approximately $2.92. The Company paid $309,479 in commissions and offering fees related to the sale of the common stock. For the nine months ended September 30, 2020, the Company sold 1,128,608 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $2,325,478, at a weighted average selling price of approximately $2.06. The Company paid $63,000 in commissions and offering fees related to the sale of common stock. Approximately $32.3 million remains available for sale under this facility.

We are not required to sell any shares at any time during the term of the facility. Our ability to sell common stock under the facility may be limited by several factors including, among other things, the trading volume of our common stock and certain black-out periods that we may impose upon the facility, among other things.

On February 4, 2020, the Company entered into an underwriting agreement with Cantor Fitzgerald & Co., as underwriter, pursuant to which the Company agreed to issue and sell an aggregate of up to 3,670,212 shares of its common stock, which included 478,723 optional shares that may be sold pursuant to an over-allotment option granted to the underwriters. On February 6, 2020, the Company closed the sale of 3,191,489 shares of its common stock at the public offering price of $2.22 per share (the "Offering").

On February 19, 2020, the underwriter exercised its over-allotment option to purchase an additional 478,723 shares at a price of $2.22 per share, which closed on February 21, 2020. The Company raised a total of $8.0 million, net of issuance costs of $0.1 million, relating to the sale of the common stock in the Offering. The Offering was made pursuant to the Company’s effective Registration Statement on Form S-3 (File No. 333-227363), which was previously filed with the SEC.

On September 23, 2020, the Company entered into a Securities Purchase Agreement (the “2020 Purchase Agreement”) with certain purchasers named therein, pursuant to which the Company agreed to issue and sell to several institutional and accredited investors in a registered direct offering, 21,818,544 shares of common stock and warrants to purchase up to 23,178,509 shares of common stock (the “Warrants”) at a combined purchase price equal to $1.51 per share. Each Warrant is exercisable for one share of common stock at an exercise price of $1.80 per share. The Warrants are immediately exercisable and will expire on September 25, 2022.

The Company also offered to certain purchasers pre-funded warrants to purchase up to an aggregate of 1,360,265 shares of common stock (the “Pre-Funded Warrants”), in lieu of shares of common stock. The purchase price of each Pre-Funded Warrant is equal to the price at which a share of common stock is sold to the public in the offering, minus $0.001, and the exercise price of each Pre-Funded Warrant is $0.001 per share. The Pre-Funded Warrants were exercised in conjunction with the issuance of common stock under the Securities Purchase Agreement. The Company received gross proceeds of approximately $35.0 million in connection with the offering, before deducting placement agent fees and related offering expenses of approximately $2.3 million.

A holder (together with its affiliates) may not exercise any portion of the Warrant to the extent that the holder would own more than 9.99% (or, at the holder’s option upon issuance, 4.99%) of the Company’s outstanding common stock immediately after exercise, as such percentage ownership is determined in accordance with the terms of the Warrant or Pre-Funded Warrant.

The Company agreed to pay H.C. Wainwright & Co., LLC (the "Placement Agent") a cash fee of 6.0% of the aggregate gross proceeds raised in the offering, minus $420,000 payable by the Company to a financial advisory firm for services related to the offering.

In addition, the Company agreed to pay the Placement Agent (i) 6.0% of the aggregate gross proceeds to be received, if any, from the cash exercise of any Warrants through December 25, 2021 and (ii) 4.0% of the aggregate gross proceeds to be received, if any, from the cash exercise of any Warrants subsequent to December 25, 2021. The Company also agreed to pay the Placement Agent non-accountable expenses of $50,000 as well as $12,900 for the clearing fees of the Placement Agent in connection with the offering.

The Company has accounted for the common stock for the 2020 Purchase Agreement as equity on the accompanying consolidated balance sheets as of September 30, 2020. The amount allocated to common stock was $26.1 million. This allocation is equal to the total proceeds of $35.0 million less the amount allocated to Warrants of $8.9 million and is also net of the direct and incremental costs associated with the 2020 Purchase Agreement of $2.3 million. The Black-Scholes pricing model was used to calculate the value of Warrants relating to the 2020 Purchase Agreement.