Note 8 - Stock-based Compensation

9 Months Ended

Sep. 30, 2018

Notes to Financial Statements

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

8.

Stock-Based Compensation

A summary of stock option activity under our

2011

Equity Incentive Plan (

“2011

Plan”) for the

nine

months ended

September 30, 2018

is presented below (in thousands, except per share and contractual life data).

				Weighted		Weighted Average
				Average		Remaining
	Number of			Exercise Price		Contractual
	Shares			Per Share		Life (in Years)
Options outstanding as of December 31, 2017		5,675		$	4.87		7.40
Granted		3,139		$	1.94
Exercised		(76	)	$	1.95
Forfeited or expired		(1,157	)	$	4.15
Options outstanding as of September 30, 2018		7,581		$	3.80		7.04
Options exercisable as of September 30, 2018		2,943		$	6.06		4.34

The estimated aggregate intrinsic value of stock options exercisable as of

September 30, 2018

was

$0.1

million. As of

September 30, 2018,

there was

$4.9

million of total unrecognized compensation cost related to outstanding stock options that will be recognized over a weighted average period of

2.82

years.

During the

nine

months ended

September 30, 2018,

we granted stock options to purchase

3,138,752

shares of common stock to certain employees, board members and a contractor. The options are exercisable for a period of

ten

years from the date of grant at prices ranging from

$1.69

to

$2.07

per share, which was the fair value of our common stock on the respective grant dates. The options generally vest over a period of

four

years. The fair value of these options, calculated using the Black-Scholes option-pricing model, was determined to be

$3.8

million (

$0.96

to

$1.30

per share) using the following assumptions: expected term of

5.50

to

6.11

years, volatility of

48.0%

to

67.0%,

risk-free interest rate of

2.3%

to

3.0%,

and expected dividend rate of

0.0%.

 

During the

nine

months ended

September 30, 2018,

we recorded

$0.4

million of stock-based compensation expense related to stock option modifications for executive transitions.

The following table summarizes restricted stock unit (“RSU”) activity for the

nine

months ended

September 30, 2018 (

in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2017		83		$	12.43
Awarded		—			—
Vested and released		(36	)		12.43
Forfeited/canceled		—			—
Outstanding as of September 30, 2018		47		$	12.43

As of

September 30, 2018,

there was

$0.5

million of total unrecognized compensation cost related to the outstanding RSUs that will be recognized over a weighted average period of

0.9

years.

We adopted an employee stock purchase plan in

June 2015

for all eligible employees. At

September 30, 2018

the maximum number of shares that

may

be issued under the plan is

1,550,000.

During the

nine

months ended

September 30, 2018,

225,887

shares were issued under the stock purchase plan.

Stock-based compensation expense recognized for stock-based awards in the condensed consolidated statements of operations for the

three

and

nine

months ended

September 30, 2018

and

2017

was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of sales	$	74	$	36	$	201	$	184
Research and development		110		71		321		203
Clinical and regulatory		19		42		122		135
Selling and marketing		165		116		380		321
General and administrative		509		640		1,765		1,978
Total	$	877	$	905	$	2,789	$	2,821