Common stock	12 Months Ended
Dec. 31, 2018
Common stock
Common stock	Note 12. Common stock On July 28, 2015, the Company closed its initial public offering (“IPO”) whereby the Company sold 5,520,000 shares of common stock, at a public offering price of $15.00 per share, which includes 720,000 shares of common stock resulting from the underwriters’ exercise of their over‑allotment option at the IPO price on July 23, 2015. Proceeds from the Company’s IPO, net of underwriting discounts and commissions and other offering costs, were $75.0 million. In connection with the IPO, the Company’s Board of Directors approved a 1‑for‑2.4 reverse stock split of the Company’s common stock which also resulted in a proportional adjustment to the conversion ratios of the preferred stock and the preferred stock warrants. All references to common stock and per share amounts in these condensed financial statements and accompanying footnotes have been retroactively adjusted for all periods presented to give effect to this reverse stock split. In February 2017, the Company closed an underwritten public offering of 5,750,000 shares of its common stock at a public offering price of $5.00 per share, which included 750,000 shares of its common stock resulting from the underwriters’ exercise of their over-allotment option on February 17, 2017. Deerfield, the Company’s senior lender, participated in the purchase of the Company’s common shares as part of this public offering, and as a result, was classified as a related party at the time of the corresponding transactions. The net proceeds to the Company from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company, were approximately $26.7 million. On June 30, 2017, the Company closed an underwritten public offering of 4,800,000 shares of its common stock at a public offering price of $6.25 per share for total proceeds of $30.0 million before estimated offering costs of $0.2 million. The Company also granted the underwriters a 30-day option to purchase up to an additional 720,000 shares of its common stock which was exercised in full on July 26, 2017. The net proceeds to the Company through July 26, 2017 from this offering, after deducting offering expenses payable by the Company, were approximately $34.3 million. The shares of common stock for both the June 2017 and February 2017 offerings were offered pursuant to a shelf registration statement on Form S-3, including a base prospectus, filed by the Company on August 1, 2016, and declared effective by the SEC on August 12, 2016. This shelf registration statement covers the offering, issuance and sale by the Company of up to an aggregate of $125.0 million of its common stock, preferred stock, debt securities, warrants and/or units (the “Shelf”). The Company simultaneously entered into a sales agreement with Cowen and Company, LLC, as sales agent, to provide for the offering, issuance and sale by the Company of up to $40.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “Sales Agreement”). During the year ended December 31, 2017, the Company sold an aggregate 749,639 shares of common stock under the Sales Agreement, at an average sale price of approximately $5.01 per share for gross proceeds of $3.7 million and net proceeds of $3.6 million and paying total compensation to the sales agent of approximately $0.1 million. On October 26, 2017, Deerfield provided a conversion notice electing to convert the entire $6.6 million of Convertible Notes into shares of the Company’s common stock at a conversion price of $7.08 per share. The conversion price was based on 95% of the average of the volume weighted average prices per share of the Company’s common stock on the NASDAQ Global Market for the three trading day period immediately preceding such conversion. This resulted in issuing 929,967 shares of the Company’s common stock to Deerfield on this date and the Convertible Notes were cancelled. During the year ended December 31, 2018, the Company sold an aggregate 651,525 shares of common stock under the Sales Agreement, at an average sale price of approximately $6.25 per share for gross proceeds of $4.1 million and net proceeds of $3.9 million and paying total compensation to the sales agent and other costs of approximately $0.2 million. On November 5, 2018, the Company filed Supplement No. 1 to the prospectus dated August 12, 2016, which reduced the size of the continuous offering by the Company under such prospectus relating to the offering of Common Stock pursuant to the Sales Agreement. Following the reduction, the Company is authorized to issue up to $7,825,113 of its common stock pursuant to the Sales Agreement (inclusive of amounts previously sold thereunder prior to the date hereof). Aggregate gross proceeds of sales of the Company’s common stock under the Sales Agreement total $7,825,113, and sales of common stock under the Sales Agreement have been suspended. On November 8, 2018, the Company closed an underwritten public offering of 19,999,999 shares of its common stock at a public offering price of $2.30 per share, which includes 2,608,695 shares of its common stock resulting from the underwriters’ exercise of their over-allotment option at the public offering price. The net proceeds to the Company from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company were approximately $43.4 million. This offering met the criteria for the November Offering. As of December 31, 2018, $5.2 million of the Company’s common stock, preferred stock, debt securities, warrants and/or units remained available to be sold pursuant to the Shelf. During the year ended December 31, 2018, the Company issued 26,991 shares of common stock pursuant to the conversion of vested RSUs and 832 shares of common stock pursuant to the exercise of vested stock options.

Note 12. Common stock

On July 28, 2015, the Company closed its initial public offering (“IPO”) whereby the Company sold 5,520,000 shares of common stock, at a public offering price of $15.00 per share, which includes 720,000 shares of common stock resulting from the underwriters’ exercise of their over‑allotment option at the IPO price on July 23, 2015. Proceeds from the Company’s IPO, net of underwriting discounts and commissions and other offering costs, were $75.0 million.

In connection with the IPO, the Company’s Board of Directors approved a 1‑for‑2.4 reverse stock split of the Company’s common stock which also resulted in a proportional adjustment to the conversion ratios of the preferred stock and the preferred stock warrants. All references to common stock and per share amounts in these condensed financial statements and accompanying footnotes have been retroactively adjusted for all periods presented to give effect to this reverse stock split.

In February 2017, the Company closed an underwritten public offering of 5,750,000 shares of its common stock at a public offering price of $5.00 per share, which included 750,000 shares of its common stock resulting from the underwriters’ exercise of their over-allotment option on February 17, 2017. Deerfield, the Company’s senior lender, participated in the purchase of the Company’s common shares as part of this public offering, and as a result, was classified as a related party at the time of the corresponding transactions. The net proceeds to the Company from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company, were approximately $26.7 million.

On June 30, 2017, the Company closed an underwritten public offering of 4,800,000 shares of its common stock at a public offering price of $6.25 per share for total proceeds of $30.0 million before estimated offering costs of $0.2 million. The Company also granted the underwriters a 30-day option to purchase up to an additional 720,000 shares of its common stock which was exercised in full on July 26, 2017. The net proceeds to the Company through July 26, 2017 from this offering, after deducting offering expenses payable by the Company, were approximately $34.3 million.

The shares of common stock for both the June 2017 and February 2017 offerings were offered pursuant to a shelf registration statement on Form S-3, including a base prospectus, filed by the Company on August 1, 2016, and declared effective by the SEC on August 12, 2016. This shelf registration statement covers the offering, issuance and sale by the Company of up to an aggregate of $125.0 million of its common stock, preferred stock, debt securities, warrants and/or units (the “Shelf”). The Company simultaneously entered into a sales agreement with Cowen and Company, LLC, as sales agent, to provide for the offering, issuance and sale by the Company of up to $40.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “Sales Agreement”).

During the year ended December 31, 2017, the Company sold an aggregate 749,639 shares of common stock under the Sales Agreement, at an average sale price of approximately $5.01 per share for gross proceeds of $3.7 million and net proceeds of $3.6 million and paying total compensation to the sales agent of approximately $0.1 million.

On October 26, 2017, Deerfield provided a conversion notice electing to convert the entire $6.6 million of Convertible Notes into shares of the Company’s common stock at a conversion price of $7.08 per share. The conversion price was based on 95% of the average of the volume weighted average prices per share of the Company’s common stock on the NASDAQ Global Market for the three trading day period immediately preceding such conversion. This resulted in issuing 929,967 shares of the Company’s common stock to Deerfield on this date and the Convertible Notes were cancelled.

During the year ended December 31, 2018, the Company sold an aggregate 651,525 shares of common stock under the Sales Agreement, at an average sale price of approximately $6.25 per share for gross proceeds of $4.1 million and net proceeds of $3.9 million and paying total compensation to the sales agent and other costs of approximately $0.2 million.

On November 5, 2018, the Company filed Supplement No. 1 to the prospectus dated August 12, 2016, which reduced the size of the continuous offering by the Company under such prospectus relating to the offering of Common Stock pursuant to the Sales Agreement. Following the reduction, the Company is authorized to issue up to $7,825,113 of its common stock pursuant to the Sales Agreement (inclusive of amounts previously sold thereunder prior to the date hereof). Aggregate gross proceeds of sales of the Company’s common stock under the Sales Agreement total $7,825,113, and sales of common stock under the Sales Agreement have been suspended.

On November 8, 2018, the Company closed an underwritten public offering of 19,999,999 shares of its common stock at a public offering price of $2.30 per share, which includes 2,608,695 shares of its common stock resulting from the underwriters’ exercise of their over-allotment option at the public offering price. The net proceeds to the Company from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company were approximately $43.4 million. This offering met the criteria for the November Offering.

As of December 31, 2018, $5.2 million of the Company’s common stock, preferred stock, debt securities, warrants and/or units remained available to be sold pursuant to the Shelf.

During the year ended December 31, 2018, the Company issued 26,991 shares of common stock pursuant to the conversion of vested RSUs and 832 shares of common stock pursuant to the exercise of vested stock options.