Convertible Preferred Stock and Stockholders’ Equity	12 Months Ended
Dec. 31, 2018
Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity	7. Convertible Preferred Stock and Stockholders’ Equity As of December 31, 2015, the Company had 2,172,520 shares of Series A convertible preferred stock outstanding and 4,999,976 shares of Series B convertible preferred stock outstanding with a related carrying value of $13.6 million and $44.7 million, respectively. Immediately prior to the closing of the Company’s initial public offering (“IPO”) in April 2016, all of the outstanding convertible preferred stock was automatically converted into 7,172,496 shares of common stock on a one-to-one basis, with the aggregate total carrying value of $58.3 million reclassified to common stock and additional paid-in capital. As of December 31, 2018 and 2017, there were no shares of preferred stock outstanding. On April 12, 2016, the Company closed an IPO of its common stock, which resulted in the sale of 5,481,940 shares of its common stock at a public offering price of $10.00 per share, including 481,940 shares of common stock issued upon the partial exercise by the underwriters of their option to purchase additional shares. The Company received $47.3 million in aggregate cash proceeds, net of underwriting discounts and commissions of $3.8 million and offering costs of $3.7 million incurred by the Company. In connection with the IPO, the Company amended its Restated Certificate of Incorporation to change the authorized capital stock to 510,000,000 shares of which 500,000,000 shares are designated as common stock and 10,000,000 shares are designated as preferred stock, all with a par value of $0.0001 per share. Each holder of common stock is entitled to one vote for each share of common stock held. The Company’s common stock is not entitled to preemptive rights, and is not subject to conversion, redemption or sinking fund provisions. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of common stock are entitled to receive dividends out of funds legally available if the board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that the board of directors may determine. As of December 31, 2018, no common stock dividends have been declared by the board of directors. Follow-on Public Offerings In June 2017, the Company issued and sold 3,000,000 shares of common stock in an underwritten public offering pursuant to a shelf registration statement on Form S-3 at a public offering price of $4.10 per share. The net proceeds to the Company from this public offering was $11.4 million, after deducting underwriting discounts and commissions of $0.6 million and offering costs of $0.3 million. In April 2018, the Company issued and sold 5,046,510 shares of common stock in an underwritten public offering pursuant to a shelf registration statement on Form S-3 at a public offering price of $8.00 per share, including 546,510 shares of common stock issued upon the partial exercise by the underwriters of their option to purchase additional shares. The net proceeds to the Company from this public offering was $37.7 million, after deducting underwriting discounts and commissions of $2.4 million and offering costs of $0.3 million. At-The-Market Offering In May 2017, the Company entered into a sales agreement with JonesTrading Institutional Services LLC, as sales agent and underwriter, pursuant to which the Company may issue and sell shares of its common stock for an aggregate offering price of $20.0 million under an at-the-market (“ATM’) offering program. In October 2018, the Company sold 1,845,820 shares of common stock in a single transaction pursuant to the ATM at an offering price of $9.21 per share for gross proceeds of $17.0 million, resulting in net proceeds of $16.4 million after deducting underwriting fees and offering expenses. The Company subsequently terminated the ATM sales agreement with JonesTrading in December 2018 and entered into a sales agreement with Jeffries LLC, as sales agent and underwriter, to issue and sell shares of the Company’s common stock for an aggregate offering price of $60.0 million under an ATM offering program.

Convertible Preferred Stock and Stockholders’ Equity

12 Months Ended

Dec. 31, 2018

Convertible Preferred Stock and Stockholders’ Equity

7. Convertible Preferred Stock and Stockholders’ Equity

As of December 31, 2015, the Company had 2,172,520 shares of Series A convertible preferred stock outstanding and 4,999,976 shares of Series B convertible preferred stock outstanding with a related carrying value of $13.6 million and $44.7 million, respectively. Immediately prior to the closing of the Company’s initial public offering (“IPO”) in April 2016, all of the outstanding convertible preferred stock was automatically converted into 7,172,496 shares of common stock on a one-to-one basis, with the aggregate total carrying value of $58.3 million reclassified to common stock and additional paid-in capital. As of December 31, 2018 and 2017, there were no shares of preferred stock outstanding.

On April 12, 2016, the Company closed an IPO of its common stock, which resulted in the sale of 5,481,940 shares of its common stock at a public offering price of $10.00 per share, including 481,940 shares of common stock issued upon the partial exercise by the underwriters of their option to purchase additional shares. The Company received $47.3 million in aggregate cash proceeds, net of underwriting discounts and commissions of $3.8 million and offering costs of $3.7 million incurred by the Company.

In connection with the IPO, the Company amended its Restated Certificate of Incorporation to change the authorized capital stock to 510,000,000 shares of which 500,000,000 shares are designated as common stock and 10,000,000 shares are designated as preferred stock, all with a par value of $0.0001 per share. Each holder of common stock is entitled to one vote for each share of common stock held. The Company’s common stock is not entitled to preemptive rights, and is not subject to conversion, redemption or sinking fund provisions. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of common stock are entitled to receive dividends out of funds legally available if the board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that the board of directors may determine. As of December 31, 2018, no common stock dividends have been declared by the board of directors.

Follow-on Public Offerings

In June 2017, the Company issued and sold 3,000,000 shares of common stock in an underwritten public offering pursuant to a shelf registration statement on Form S-3 at a public offering price of $4.10 per share. The net proceeds to the Company from this public offering was $11.4 million, after deducting underwriting discounts and commissions of $0.6 million and offering costs of $0.3 million.

In April 2018, the Company issued and sold 5,046,510 shares of common stock in an underwritten public offering pursuant to a shelf registration statement on Form S-3 at a public offering price of $8.00 per share, including 546,510 shares of common stock issued upon the partial exercise by the underwriters of their option to purchase additional shares. The net proceeds to the Company from this public offering was $37.7 million, after deducting underwriting discounts and commissions of $2.4 million and offering costs of $0.3 million.

At-The-Market Offering

In May 2017, the Company entered into a sales agreement with JonesTrading Institutional Services LLC, as sales agent and underwriter, pursuant to which the Company may issue and sell shares of its common stock for an aggregate offering price of $20.0 million under an at-the-market (“ATM’) offering program. In October 2018, the Company sold 1,845,820 shares of common stock in a single transaction pursuant to the ATM at an offering price of $9.21 per share for gross proceeds of $17.0 million, resulting in net proceeds of $16.4 million after deducting underwriting fees and offering expenses.

The Company subsequently terminated the ATM sales agreement with JonesTrading in December 2018 and entered into a sales agreement with Jeffries LLC, as sales agent and underwriter, to issue and sell shares of the Company’s common stock for an aggregate offering price of $60.0 million under an ATM offering program.