Note 9 - Stock-Based Compensation

12 Months Ended

Dec. 31, 2016

Notes to Financial Statements

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

9.

          Stock-Based Compensation

Stock Option Plans

We use the Black-Scholes model for determining the grant date fair value of our stock option grants. This model utilizes certain information, such as the interest rate on a risk-free security with a term generally equivalent to the expected life of the option being valued and requires certain other assumptions, such as the expected amount of time an option will be outstanding until it is exercised or expired, to calculate the fair value of stock options granted. The significant assumptions we used in our fair value calculations were as follows:

	2016			2015			2014
Weighted average risk-free interest rates		2.26	%		1.99	%		1.98	%
Expected dividend yield		0.0	%		0.0	%		0.0	%
Expected life of option (yrs )	7.0			7.0			7.0
Expected volatility		88.72	%		91.43	%		94.88	%

Stock-based compensation expense related to our stock option plans was

$54,805,

$67,905,

and

$101,191

during the years ended

December

31,

2016,

2015

and

2014,

respectively. Stock option expense is allocated to research and development expense or to general and administrative expense based on the nature of the services provided by the related individuals. For the

three

years ended

December

31,

2016,

stock option expense was allocated as follows:

	2016		2015		2014
General and administrative expense	$	31,191	$	45,822	$	69,057
Research and development expense		23,614		22,083		32,134
Total stock option expense	$	54,805	$	67,905	$	101,191

As of

December

31,

2016,

there was

$132,032

of unrecognized compensation expense related to stock-based compensation arrangements pursuant to our stock option plans. The unrecognized compensation expense is expected to be recognized over a weighted average remaining period of

2.5

years.

Additional information concerning our stock options for the years ended

December

31,

2016,

2015

and

2014

is as follows:

	2016		2015		2014
Weighted average fair value of options granted	$	0.05	$	0.09	$	0.14
Intrinsic value of options exercised		-0-		-0-		-0-
Total fair value of options vested		54,757		66,622		97,707

Other Non-E

mp

loyee Stock-Based C

ompensation

We recorded general and administrative expense of

$100,000

during the year ended

December

31,

2015

related to the issuance of our common stock in exchange for services rendered by non-employees.

We recorded general and administrative expense of

$912,862,

$-

0

-, and

$277,912

during the years ended

December

31,

2016,

2015

and

2014,

respectively, related to modifications made to certain stock purchase warrants.