Note 7 - Stockholders' Equity

3 Months Ended

Mar. 31, 2016

Notes to Financial Statements

Stockholders' Equity Note Disclosure [Text Block]

7.     Stockholders’ Equity

Preferred Stock Transactions

During January and February 2016 we issued an aggregate of 1,400,000 shares of our common stock related to conversions of 132 shares our Series C Convertible Preferred Stock. As of March 31, 2016, there are 100 shares of our Series B Convertible Preferred Stock outstanding, and 2,868 shares of our Series C Convertible Preferred Stock outstanding, convertible into 285,714 and 30,460,662 shares of our common stock, respectively.

Common Stock Transactions

In addition to common stock issued pursuant to the conversion of our Series C Convertible Preferred Stock described above, in February 2016 we issued an aggregate of 3,664,588 shares of our common stock related to exercises of stock purchase warrants as described below.

Stock Options

We maintain a stock option plan that provides the Board of Directors broad discretion in creating equity incentives for employees, officers, directors and consultants.

The following table presents a summary of stock option transactions during the three months ended March 31, 2016:

	Number of Shares		Weighted Average Exercise Price
Outstanding at December 31, 2015		1,705,500	$	2.41
Granted		--		--
Exercised		--		--
Forfeited or expired		--		--
Outstanding at March 31, 2016		1,705,500	$	2.41
Exercisable at March 31, 2016		915,561	$	4.35

Stock Purchase Warrants

The following table presents a summary of stock purchase warrant transactions during the three months ended March 31, 2016:

	Number of Shares			Weighted Average Exercise Price
Outstanding at December 31, 2015		56,442,157		$	0.14
Granted		--			--
Exercised		(3,664,588	)		0.065
Forfeited or expired		--			--
Outstanding at March 31, 2016		52,777,569		$	0.14
Exercisable at March 31, 2016		39,775,491		$	0.15

On February 15, 2016, we entered into an agreement with certain warrant holders (the “Holders”) with respect to amending the terms of our Series E Warrants. Pursuant to the agreement, we agreed to extend the term of the Series E Warrants to August 27, 2016, and we agreed to the payment to each Holder of a warrant exercise fee of $0.02916 per share for each share purchased upon exercise of the Series E Warrants. The Holders agreed to promptly exercise an aggregate of 3,664,588 Series E Warrants, for which we received $238,198 in total net proceeds (after deduction of the warrant exercise fee). We recorded non-cash general and administrative expense of $469,799 associated with the warrant modifications.

Stock-Based Compensation Expense

As described above, during the three month period ended March 31, 2016, we recorded $238,198 of stock-based compensation expense related to warrant modifications. During the three month periods ended March 31, 2016 and 2015, we recorded stock-based compensation expense related to stock options of $13,686 and $16,902, respectively. Stock-based compensation expense related to stock options is recognized on a straight-line basis over the requisite service period for the award and is allocated to research and development expense or general and administrative expense based upon the related employee classification. As of March 31, 2016, there was $81,658 of unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted average period of 2.0 years.

Common Stock Reserved

A summary of our common stock reserved for future issuance is as follows as of March 31, 2016:

Series B Convertible Preferred Stock	285,714
Series C Convertible Preferred Stock	30,460,663
Common Stock Purchase Warrants	52,777,569
Equity Incentive Plans	1,722,529
Total	85,246,475