Stock award plan

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

On March 5, 2013, the Company’s Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards in the aggregate of 739,937 shares of common stock. On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan.

In 2009, the Company’s shareholders approved the 2009 Equity and Long-Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards, subject to certain adjustments and annual increases. In May 2013, the Company’s Board of Directors and stockholders increased by 2,500,000 the number of shares authorized under the 2009 Equity and Long Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards. There are no additional shares available for issuance under this plan.

In May 2013, the Company’s Board of Directors and stockholders approved the 2013 Long Term Incentive Plan, which became effective upon the closing of the Company’s initial public offering. The 2013 Long Term Incentive Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards and other stock-based awards. The number of shares of common stock reserved for issuance under the 2013 Long Term Incentive Plan is the sum of (1) 122,296 shares of common stock available for issuance under the Company’s 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan, (2) the number of shares (up to 3,040,444 shares) equal to the sum of the number of shares of common stock subject to outstanding awards under the Company’s 1998 Employee, Director and Consultant Stock Option Plan, 2009 Equity and Long Term Incentive

Plan and 2013 Stock Incentive Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right plus (3) an annual increase, to be added on the first day of each fiscal year until the expiration of the 2013 Long Term Incentive Plan, equal to the lowest of 2,500,000 shares of common stock, 4% of the number of shares of common stock outstanding on the first day of the fiscal year and an amount determined by the Company’s Board of Directors. As of June 30, 2019, awards for 302,538 shares of common stock are available for issuance.

From January 1, 2019 through June 30, 2019, the Company issued a total of 2,845,620 stock options to various employees. Of those, 579,700 were inducement grants for non-statutory stock options. The inducement grant awards were made pursuant to the Nasdaq Listing Rule 5635(c)(4) inducement grant exception as a material component of the Company's new hires’ employment compensation and not under the 2013 Long Term Incentive Plan.

A summary of stock option activity is as follows:



	Number of options		Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value (in thousands)

Outstanding at December 31, 2018	8,534,358		$	28.58
Granted	2,845,620		$	33.54
Exercised	(311,002	)	$	16.50
Forfeited/Cancelled	(215,675	)	$	36.10
Outstanding at June 30, 2019	10,853,301		$	30.07	7.59 years	$	178,906
Vested or Expected to vest at June 30, 2019	5,334,168		$	29.22	9.01 years	$	84,446
Exercisable at June 30, 2019	5,138,717		$	30.90	5.98 years	$	88,423

The fair value of grants made in the six months ended June 30, 2019 was contemporaneously estimated on the date of grant using the following assumptions:



		Six months ended June 30, 2019
Risk-free interest rate		1.98 - 2.63%
Expected volatility		61.90 - 63.09%
Expected term		6.11 years

The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the six-month period ended June 30, 2019 was $20.01 per share.

The Company uses the “simplified method” to determine the expected term of options. Under this method, the expected term represents the average of the vesting period and the contractual term. The expected volatility of share options was estimated based on a historical volatility analysis of peers that were similar to the Company with respect to industry, stage of life cycle, size, and financial leverage. The risk-free rate of the option is based on U.S. Government Securities Treasury Constant Maturities yields at the date of grant for a term similar to the expected term of the option.

Restricted Stock Awards—Restricted stock awards are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock awards, which has been determined based upon the market value of the Company’s shares on the grant date, is expensed over the vesting period.

Restricted Stock Units—Restricted stock units are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock units, which has been determined based upon the market value of the Company’s shares on the grant date, is expensed over the vesting period.

The following table summarizes information on the Company’s restricted stock awards and units:



	Restricted Stock Awards and Units
	Number of Shares		Weighted Average Grant Date Fair Value
January 1, 2019	571,479		$	17.61
Granted	304,549		$	32.94
Vested	(179,577	)	$	17.54
Forfeited	(31,449	)	$	21.47
Unvested at June 30, 2019	665,002		$	24.45

Stock Appreciation Rights—SARs entitle the holder to receive, upon exercise, an amount of the Company's common stock or cash (or a combination thereof) determined by reference to appreciation, from and after the date of grant, in the fair market value of a share of the Company's common stock over the measurement price based on the exercise date.

In May 2016, a total of 897,290 SARs were granted to non-executive employees (the "2016 SARs"). The 2016 SARs will vest annually in equal installments over four years and will be settled in cash on each vest date, requiring the Company to remeasure the SARs at each reporting period until vesting occurs. For the six month period ended June 30, 2019, a total of 157,930 SARs vested. For the three and six month periods ended June 30, 2019, the Company recorded $0.9 million and $1.9 million, respectively, in compensation expense related to the 2016 SARs.

Employee Stock Purchase Plan—In June 2016, the Company established an Employee Stock Purchase Plan (“ESPP” or the "Plan”) for certain eligible employees. The Plan is administered by the Company’s Board of Directors or a committee appointed by the Company's Board of Directors. The total number of shares available for purchase under the Plan is one million shares of the Company’s common stock. Employees may participate over a six-month period through payroll withholdings and may purchase, at the end of the six-month period, the Company’s common stock at a purchase price of at least 85% of the closing price of a share of the Company’s common stock on the first business day of the offering period or the closing price of a share of the Company’s common stock on the last business day of the offering period, whichever is lower. No participant will be granted a right to purchase the Company’s common stock under the Plan if such participant would own more than 5% of the total combined voting power of the Company or any subsidiary of the Company after such purchase. For the three and six month periods ended June 30, 2019, the Company recorded $0.3 million and $0.6 million, respectively, in compensation expense related to the ESPP.

The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units and the ESPP as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	5,516	$	3,932	$	10,203	$	7,678
Selling, general and administrative	5,404		4,152		9,981		8,153
Total	$	10,920	$	8,084	$	20,184	$	15,831

As of June 30, 2019, there was approximately $105.8 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 2009 Equity and Long Term Incentive Plan, the 2013 Long Term Incentive Plan and equity awards made pursuant to the Nasdaq Listing Rule 5635(c)(4) inducement grant exception for new hires. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 3.10 years.