Common and Preferred Stock	12 Months Ended
Dec. 31, 2019
Equity [Abstract]
Common and Preferred Stock	10. Common and Preferred Stock The Company is authorized to issue 280,000,000 shares of common stock, par value $0.01 per share, and 10,000,000 shares of undesignated preferred stock, par value $0.01 per share, issuable in one or more series as designated by the Company’s board of directors. No other class of capital stock is authorized. As of December 31, 2019 and 2018, 211,787,573 and 187,029,967 shares of common stock, respectively, were issued and outstanding and no shares of preferred stock were outstanding. In February 2018, the Company entered into a controlled equity offering sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor Fitzgerald”), as sales agent, pursuant to which the Company may offer and sell, from time to time, through Cantor Fitzgerald, shares of the Company’s common stock having an aggregate offering price of up to $50.0 million or such other amount as may be permitted by the Sales Agreement. Under the Sales Agreement, Cantor Fitzgerald may sell shares by any method deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act of 1933, as amended. For the year ended December 31, 2019, the Company sold an aggregate of 2,584,964 shares of the Company’s common stock at an average purchase price of $1.24 per share for an aggregate gross proceeds of approximately $3.2 million pursuant to the Sales Agreement. For the year ended December 31, 2018, the Company sold an aggregate of 1,028,432 shares of the Company’s common stock at an average purchase price of $2.03 per share for an aggregate gross proceeds of approximately $2.1 million pursuant to the Sales Agreement. In April 2018, the Company entered into securities purchase agreements with certain institutional investors. Pursuant to the terms of the purchase agreements, the Company sold to the purchasers in a registered offering an aggregate of 14,000,000 shares of the Company’s common stock and warrants to purchase up to an aggregate of 14,000,000 shares of the Company’s common stock at a combined purchase price of $2.00 per share and accompanying warrant. The shares of common stock and the warrants were immediately separable. The warrants became exercisable at a price of $2.38 per share beginning on October 9, 2018 and expired unexercised on April 9, 2019. The net proceeds to the Company from the offering were approximately $26.4 million. The offering closed on April 9, 2018. In December 2018, the Company entered into an underwriting agreement with Leerink Partners LLC relating to the issuance and sale in a public offering of 26,666,667 shares of the Company’s common stock and warrants to purchase up to an aggregate of 26,666,667 shares of the Company’s common stock (the “December warrants”) at a combined purchase price of $1.50 per share and accompanying warrant. The shares of common stock and the December warrants were immediately separable. The December warrants were immediately exercisable at issuance at a price of $1.60 per share and had an expiry date of December 26, 2019. The net proceeds to the Company from the offering were approximately $37.3 million. The Company determined that the December warrants met the criteria for equity classification and accounted for such warrants in additional paid-in capital. In July 2019, the Company repurchased 3,333,334 December warrants for consideration of approximately $0.4 million, for which $0.2 million was recognized as a reduction to additional paid-in capital on the consolidated balance sheet and $0.2 million was recognized as other expense on the consolidated statement of operations for cash paid in excess of fair value. On December 23, 2019, the Company and one holder of a December warrant to purchase 11,750,000 shares of the Company’s common stock (the “Warrant Shares”) agreed to amend their December warrant to provide that (i) the exercise price per share for 4,500,000 Warrant Shares would be equal to $1.311 but only with respect to a cash exercise of such December warrant on December 23, 2019 and (ii) if the holder purchased at least 4,500,000 Warrant Shares pursuant to a timely cash exercise of such December warrant, the termination date of such December warrant would be extended to June 26, 2020. The Company determined that the modified December warrants met the criteria for equity classification and the incremental fair value of approximately $0.7 million was recognized as additional paid-in capital. On December 23, 2019, 4,500,000 Warrant Shares were exercised by the holder at $1.311 per share for an aggregate exercise price of $5.9 million. On December 26, 2019, 11,583,333 December warrants expired unexercised. As of December 31, 2019, 7,250,000 Warrant Shares remained available for purchase by such holder until June 26, 2020 at a price of $1.60 per share. For the year ended December 31, 2018, the Company received $0.4 million from the market price stock purchase plan for 230,445 shares. There were no market price stock purchase plan transactions for the year ended December 31, 2019.

Common and Preferred Stock

12 Months Ended

Dec. 31, 2019

10. Common and Preferred Stock

The Company is authorized to issue 280,000,000 shares of common stock, par value $0.01 per share, and 10,000,000 shares of undesignated preferred stock, par value $0.01 per share, issuable in one or more series as designated by the Company’s board of directors. No other class of capital stock is authorized. As of December 31, 2019 and 2018, 211,787,573 and 187,029,967 shares of common stock, respectively, were issued and outstanding and no shares of preferred stock were outstanding.

In February 2018, the Company entered into a controlled equity offering sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor Fitzgerald”), as sales agent, pursuant to which the Company may offer and sell, from time to time, through Cantor Fitzgerald, shares of the Company’s common stock having an aggregate offering price of up to $50.0 million or such other amount as may be permitted by the Sales Agreement. Under the Sales Agreement, Cantor Fitzgerald may sell shares by any method deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act of 1933, as amended. For the year ended December 31, 2019, the Company sold an aggregate of 2,584,964 shares of the Company’s common stock at an average purchase price of $1.24 per share for an aggregate gross proceeds of approximately $3.2 million pursuant to the Sales Agreement. For the year ended December 31, 2018, the Company sold an aggregate of 1,028,432 shares of the Company’s common stock at an average purchase price of $2.03 per share for an aggregate gross proceeds of approximately $2.1 million pursuant to the Sales Agreement.

In April 2018, the Company entered into securities purchase agreements with certain institutional investors. Pursuant to the terms of the purchase agreements, the Company sold to the purchasers in a registered offering an aggregate of 14,000,000 shares of the Company’s common stock and warrants to purchase up to an aggregate of 14,000,000 shares of the Company’s common stock at a combined purchase price of $2.00 per share and accompanying warrant. The shares of common stock and the warrants were immediately separable. The warrants became exercisable at a price of $2.38 per share beginning on October 9, 2018 and expired unexercised on April 9, 2019. The net proceeds to the Company from the offering were approximately $26.4 million. The offering closed on April 9, 2018.

In December 2018, the Company entered into an underwriting agreement with Leerink Partners LLC relating to the issuance and sale in a public offering of 26,666,667 shares of the Company’s common stock and warrants to purchase up to an aggregate of 26,666,667 shares of the Company’s common stock (the “December warrants”) at a combined purchase price of $1.50 per share and accompanying warrant. The shares of common stock and the December warrants were immediately separable. The December warrants were immediately exercisable at issuance at a price of $1.60 per share and had an expiry date of December 26, 2019. The net proceeds to the Company from the offering were approximately $37.3 million. The Company determined that the December warrants met the criteria for equity classification and accounted for such warrants in additional paid-in capital. In July 2019, the Company repurchased 3,333,334 December warrants for consideration of approximately $0.4 million, for which $0.2 million was recognized as a reduction to additional paid-in capital on the consolidated balance sheet and $0.2 million was recognized as other expense on the consolidated statement of operations for cash paid in excess of fair value. On December 23, 2019, the Company and one holder of a December warrant to purchase 11,750,000 shares of the Company’s common stock (the “Warrant Shares”) agreed to amend their December warrant to provide that (i) the exercise price per share for 4,500,000 Warrant Shares would be equal to $1.311 but only with respect to a cash exercise of such December warrant on December 23, 2019 and (ii) if the holder purchased at least 4,500,000 Warrant Shares pursuant to a timely cash exercise of such December warrant, the termination date of such December warrant would be extended to June 26, 2020. The Company determined that the modified December warrants met the criteria for equity classification and the incremental fair value of approximately $0.7 million was recognized as additional paid-in capital. On December 23, 2019, 4,500,000 Warrant Shares were exercised by the holder at $1.311 per share for an aggregate exercise price of $5.9 million. On December 26, 2019, 11,583,333 December warrants expired unexercised. As of December 31, 2019, 7,250,000 Warrant Shares remained available for purchase by such holder until June 26, 2020 at a price of $1.60 per share.

For the year ended December 31, 2018, the Company received $0.4 million from the market price stock purchase plan for 230,445 shares. There were no market price stock purchase plan transactions for the year ended December 31, 2019.