Stock Incentive Plans (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2017

Dec. 31, 2016

Summary of incentive plan activity

	Shares Available for Grant		Stock Options Outstanding		RSUs Outstanding	Weighted Average Stock Option Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Combined Incentive Plan Balance—December 31, 2016	39,988		2,571,220		20,789	$	2.52	8.77	$	—
2014 Stock Incentive Plan Activity:
Additional shares authorized	280,142
Options granted	(18,000	)	18,000			0.71
Options cancelled	60,570		(60,570	)		1.67
Combined Incentive Plan Balance—March 31, 2017	362,700		2,528,650		20,789	$	2.53	8.71	$	53,824
Options vested and exercisable—March 31, 2017			1,107,583			$	3.36	8.05	$	3,872
Options vested and expected to vest—March 31, 2017			2,237,254			$	2.55	8.66	$	45,912

	Shares Available for Grant			Stock Options Outstanding			RSUs Outstanding			Weighted Average Stock Option Exercise Price		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
2013 Equity Incentive Plan Balance—December 31, 2014		119,077			659,554			68,902		$	2.67
Additional shares authorized		—
Options granted		(176,364	)		176,364			—		$	7.00
Options cancelled		95,784			(95,784	)		—		$	2.53
Options available for grant cancelled upon IPO		(51,863	)		—
Options cancelled post-IPO not rolled back into the 2013 Plan		—			(42,128	)
Options exercised		—			(5,000	)		—		$	2.53
RSUs granted		(1,484	)		—			1,484
RSUs cancelled		14,850			—			(14,850	)
2013 Equity Incentive Plan Balance—December 31, 2015		—			693,006			55,536		$	3.74
2014 Stock Stock Plan Balance—December 31, 2014		—
Shares authorized		333,333
Options granted		(241,500	)		241,500					$	4.32
Options cancelled		15,000			(15,000	)				$	5.09
Combined Incentive Plan Balance—December 31, 2015		106,833			919,506			55,536		$	3.87		8.81	$	—
2013 Equity Incentive Plan Activity:
Options cancelled not rolled back into the 2013 Plan					(127,629	)				$	4.19
RSUs vested and released								(27,768	)
RSUs cancelled								(6,979	)
2014 Stock Incentive Plan Activity:
Additional shares authorized		1,712,498
Options granted		(1,927,121	)		1,927,121					$	1.97
Options cancelled		147,778			(147,778	)				$	2.28
Combined Incentive Plan Balance—December 31, 2016		39,988			2,571,220			20,789		$	2.52		8.77
Options vested and exercisable—December 31, 2016					983,147					$	3.41		8.25	$	—
Options vested and expected to vest—December 31, 2016					2,163,246					$	2.52		8.73	$	—

Summary of stock-based compensation expense

	Three Months Ended
	March 31,
	2017		2016
Research and development expense	$	65,799	$	25,333
Sales and marketing expense	7,658		8,681
General and administrative expense	154,579		69,528
Total	$	228,036	$	103,542

	Years Ended December 31,
	2016		2015
Research and development expense	$	181,489	$	472,145
Sales and marketing expense		73,679		54,115
General and administrative expense		462,759		465,905
Total	$	717,927	$	992,165

Employee stock options

Schedule of estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model

	Three months ended
	March 31,
	2017		2016
Weighted-average volatility	74.26	%	—
Weighted-average expected term (years)	5.82		—
Risk-free interest rate	1.98	%	—
Expected dividend yield	—		—

	Years Ended December 31,
	2016	2015
Weighted-average volatility	66.25 - 72.08%	55.43 - 61.51%
Weighted-average expected term (years)	5.00 - 5.82	5.15 - 5.82
Risk-free interest rate	1.10 - 2.15%	1.60 - 1.84%
Expected dividend yield	—	—

Non-employee stock options

Schedule of estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model

	Three months ended
	March 31,
	2017	2016
Weighted-average volatility	—	78.51	%
Weighted-average expected term (years)	—	9.44
Risk-free interest rate	—	1.74	%
Expected dividend yield	—	—

	Years Ended December 31,
	2016	2015
Weighted-average volatility	78.30 - 80.04%		76.63	%
Weighted-average expected term (years)	9.19 - 10.00		9.69
Risk-free interest rate	1.32 - 2.46%		2.25	%
Expected dividend yield	—		—