The Company’s Board of Directors, or Board, and stockholders previously approved the 2014 Equity Incentive Plan, or the 2014 Plan, which became effective on March 21, 2014. As of March 31, 2019, the total number of shares of common stock available for issuance under the 2014 Plan was approximately 711,484. Unless the Board provides otherwise, beginning on January 1, 2015, and continuing until the expiration of the 2014 Plan, the total number of shares of common stock available for issuance under the 2014 Plan will automatically increase annually on January 1 by 4.5% of the total number of issued and outstanding shares of common stock as of December 31 of the immediately preceding year.

In March 2014, the Board and stockholders approved the 2014 Employee Stock Purchase Plan, or the ESPP, which became effective as of March 5, 2014. The Company initially reserved a total of 150,000 shares of common stock for issuance under the ESPP. Unless the Board provides otherwise, beginning on January 1, 2015, and continuing until the expiration of the ESPP, the total number of shares of common stock available for issuance under the ESPP will automatically increase annually on January 1 by the lesser of (i) 1% of the total number of issued and outstanding shares of common stock as of December 31 of the immediately preceding year, or (ii) 300,000 shares of common stock.

As part of the Merger, the Company assumed the 2010 Stock Option Plan (the “2010 Plan”) from Private Aravive. The Company has reserved a total of 600,000 shares of common stock for issuance under the 2010 Plan. As of March 31, 2019, the total number of shares of common stock available for issuance under the 2010 Plan was approximately 108,839. The 2010 Plan provides for granting of equity awards, including restricted stock and incentive and nonqualified stock options to purchase common stock, to employees, directors, officers and independent consultants of the Company. Options granted to employees and consultants under the Plan generally vest 25% after one year of service, and ratably on a monthly basis over the following three years. Options expire ten years from the date of grant.

As part of the Merger, the Company assumed the 2017 Stock Option Plan (the “2017 Plan”) from Private Aravive. The Company has reserved a total of approximately 461,000 shares of common stock for issuance under the 2017 Plan. As of March 31, 2019, the total number of shares of common stock available for issuance under the 2017 Plan was approximately 551,133. The 2017 Plan provides for granting of equity awards, including restricted stock and incentive and nonqualified stock options to purchase common stock, to employees, directors, officers and independent consultants of the Company. Options granted to employees and consultants under the Plan generally vest 25% after one year of service, and ratably on a monthly basis over the following three years. Options expire ten years from the date of grant.

						Weighted
						Average
				Weighted		Remaining		Aggregate
				Average		Contractual		Intrinsic
	Number of			Exercise		Life		Value
	Shares			Price		(in years)		(in thousands)
Balances, January 1, 2019		1,515,923		$	18.65
Options granted		396,128			5.52
Options cancelled		(60,917	)		89.77
Balances, March 31, 2019		1,851,134		$	13.50		7.2	$	8,424
Outstanding and expected to vest as of March 31, 2019		1,816,265		$	13.60		7.2	$	8,380
Exercisable as of March 31, 2019		1,449,684		$	14.06		6.6	$	7,897

During the three months ended March 31, 2019, the Company granted stock options to officers, directors and employees to purchase shares of common stock with a weighted-average grant date fair value of $5.52 per share. The fair value is being expensed over the vesting period of the options, which is usually 4 years on a straight-line basis as the services are being provided. No tax benefits were realized from options and other share-based payment arrangements during the periods.

As of March 31, 2019, total unrecognized employee stock-based compensation related to stock options granted was $3.3 million, which is expected to be recognized over the weighted-average remaining vesting period of 3.5 years.

The fair value of employee stock options was estimated using the Black-Scholes model with the following weighted-average assumptions:

	March 31,
	2019
Expected volatility		111.0	%
Risk-free interest rate		2.5	%
Dividend yield		0.0	%
Expected life (in years)		6.0

Restricted stock units are shares of common stock which are forfeited if the employee leaves the Company prior to vesting. These stock units offer employees the opportunity to earn shares of the Company’s stock over time, rather than options that give the employee the right to purchase stock at a set price. As a result of these restricted stock units, the Company recognized $0.4 million and $1.2 million, in compensation expense during the three months ended March 31, 2019 and 2018, respectively. As all of the restricted stock vests through 2018 and beyond, the Company will continue to recognize stock-based compensation expense related to the grants of these restricted stock units. If all of the remaining restricted stock units that were granted in prior years vest, the Company will recognize approximately $1.9 million in compensation expense over a weighted average remaining period of 2 years. However, no compensation expense will be recognized for restricted stock units that do not vest.