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Equity Plans (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Activity under Stock Option Plan

Activity under the Company’s equity incentive plans is set forth below:

							Options Outstanding
	Options Available for Grant			Options Outstanding			Weighted- Average Exercise Price Per Share				Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (1)
													(in millions)
Balances at December 31, 2016	164,328			2,393,829			$	10.39			8.79
Additional options authorized	668,891			—
Options granted	(403,000	)		403,000			$	12.08
Options exercised	—			(173,155	)		$	1.50
Options forfeited	85,930			(85,930	)		$	16.79
Balances at September 30, 2017	516,149			2,537,744			$	11.05			8.55		$	20.2
Options exercisable at September 30, 2017				811,539			$	8.72			8.03		$	8.2
Options vested and expected to vest at September 30, 2017				2,537,744			$	11.05			8.55		$	20.2

____________________

⁽¹⁾ The aggregate intrinsic values were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on September 30, 2017. The calculation excludes options with an exercise price higher than the closing price of the Company's common stock on September 30, 2017.

Schedule of Stock-based Compensation Expense for Employees and Non-employees for Stock Options and the 2016 ESPP

Total stock-based compensation expense was as follows (in thousands):

	Three Months Ended September 30,								Nine Months Ended September 30,
	2017				2016				2017				2016
Research and development	$	600			$	285			$	1,399			$	360
General and administrative	607				163				1,653				250
Total stock-based compensation expense	$	1,207			$	448			$	3,052			$	610

Employee and Director [Member]

Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions

The fair value of employee and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Expected term (in years)	6.08		4.16 - 5.70		5.50 - 6.08		4.16 - 5.94
Expected volatility	62.1%		62.8%		62.1% - 65.4%		62.5% - 64.8%
Risk-free interest rate	2.00%		1.38%		1.88% - 2.07%		1.27% - 1.38%
Dividend yield	—		—		—		—

X

- Definition

Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed.

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Tabular disclosure for share-based compensation plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value.

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Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.

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