Capital structure

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Common stock

In January 2019, the Company closed an underwritten public offering of its common stock pursuant to a registration statement on Form S-3. The Company issued and sold an aggregate of 7,563,725 shares of common stock under the registration statement at a public offering price of $30.20 per share, including 843,725 shares issued upon exercise by the underwriter of its option to purchase additional shares in February 2019. The Company received net proceeds of $224.2 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

In August 2019, the Company entered into an At the Market Offering Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald and RBC Capital Markets, LLC (together, the “Sales Agents”), pursuant to which, the Company may offer and sell shares of its common stock, having an aggregate offering price of up to $125.0 million from time to time through the Sales Agents by any method that is deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, pursuant to a registration statement on Form S-3. During the twelve month period ending December 31, 2019, the Company issued and sold an aggregate of 63,926 shares of common stock pursuant to the Sales Agreement at a weighted average public offering price of $46.60 per share. The Company received net proceeds of $2.6 million after deducting agent discounts and commissions and other offering expenses payable by the Company.

In September 2019, the Company closed an underwritten public offering of its common stock pursuant to a registration statement on Form S-3. The Company issued and sold an aggregate of 2,475,248 shares of common stock under the registration statement at a public offering price of $40.40 per share. The offering included an option to purchase up to an additional 371,287 shares for a period of 30 days following the offering. This option was not exercised by the underwriter. The Company received net proceeds of $97.0 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

In April 2018, the Company closed an underwritten public offering of its common stock pursuant to a registration statement on Form S-3. The Company issued and sold an aggregate of 4,600,000 shares of common stock under the registration statement at a public offering price of $27.04 per share, including 600,000 shares issued upon exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds of approximately $117.9 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

As of December 31, 2019, the Company’s number of authorized shares of common stock was 125,000,000.

Warrants

During the year ended December 31, 2019, all of the Company’s outstanding warrants expired, and the Company wrote off the remaining liability, which was immaterial. All of the Company’s outstanding warrants are classified as liabilities as of December 31, 2018 because they contain non-standard antidilution provisions. The fair value of the warrants as of December 31, 2018 was immaterial.

The following is a summary of the Company’s outstanding warrants as of December 31, 2018:



	Warrant shares	Exercise price		Expiration
Common stock	7,030	$	128	September 2019
Common stock	130	$	2,520	August 2019