Note 7 - Stock-based Compensation

9 Months Ended

Sep. 30, 2017

Notes to Financial Statements

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

7. Stock-based Compensation

Stock Options

The following table summarizes stock option activity for employees and non-employees:

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2016		2,166,254		$	8.55		7.1	$	124
Granted		719,337
Exercised		(74,001	)
Forfeited		(30,272	)
Expired		(97,406	)
Outstanding at September 30, 2017		2,683,912		$	7.18		7.4	$	140
Exercisable at September 30, 2017		1,384,925		$	8.00		6.2	$	98
Vested or expected to vest at September 30, 2017 (1)		2,683,912		$	7.18		7.4	$	140

__________________

(

1

) Represents the number of vested options at

September 30, 2017

plus the number of unvested options expected to vest based on the unvested options outstanding at

September 30, 2017.

Employee Stock Purchase Plan

The

2014

Employee Stock Purchase Plan (ESPP) initially authorized the issuance of up to

140,500

shares of Common Stock. The number of shares increases each

January 1,

commencing on

January 1, 2015

and ending on (and including)

January 1, 2024,

by an amount equal to the lesser of

one

percent of the outstanding shares as of the end of the immediately preceding fiscal year,

281,000

shares, or any lower amount determined by the Company’s Board of Directors prior to each such

January

1st.

The Company’s Board of Directors has determined there was to be

no

increase on

January 1, 2017.

As of

September 30, 2017,

the

2014

ESPP authorized the issuance of up to

304,991

shares of Common Stock. The

sixth

offering under the

2014

ESPP began on

July 1, 2017

and ends on

December 31, 2017.

No

shares and

45,047

shares were issued during the

three

and

nine

months ended

September 30, 2017

under the

2014

ESPP. The Company incurred

$18,000

and

$0.1

million in stock-based compensation expense related to the

2014

ESPP for the

three

and

nine

months ended

September 30, 2017,

respectively. The Company incurred

$30,000

and

$62,000

in stock-based compensation expense related to the

2014

ESPP for the

three

and

nine

months ended

September 30, 2016,

respectively.

Common Stock

The Company has the following shares reserved for future issuance:

	September 30, 2017		December 31, 2016
Stock-based compensation awards		3,587,144		2,982,470
Employee Stock Purchase Plan		247,774		292,821
Total		3,834,918		3,275,291