Stockholders’ Equity

Common Stock Transactions

During

March

2017,

we issued an aggregate of

983,334

shares of common stock related to the exercise of stock purchase warrants, resulting in total net proceeds of

$49,167.

Stock Options

The following table presents a summary of our stock option transactions during the

three

months ended

March

31,

2017:

	Number of Shares			Weighted Average Exercise Price
Outstanding at December 31, 2016		3,499,475		$	1.21
Granted		--			--
Exercised		--			--
Forfeited or expired		(115,200	)		17.75
Outstanding at March 31, 2017		3,384,275		$	0.64
Exercisable at March 31, 2017		2,191,281		$	1.69

Stock Purchase Warrants

The following table presents a summary of stock purchase warrant transactions during the

three

months ended

March

31,

2017:

	Number of Shares			Weighted Average Exercise Price
Outstanding at December 31, 2016		32,751,578		$	0.07
Granted		--			--
Exercised		(983,334	)		0.05
Forfeited or expired		(1,112,001	)		0.57
Outstanding at March 31, 2017		30,656,243		$	0.05
Exercisable at March 31, 2017		30,656,243		$	0.05

Stock-Based Compensation Expense

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

$14,580

and

$13,686

during the

three

-month periods ended

March

31,

2017

and

2016,

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,

2017,

there was

$117,404

of unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted average period of

2.3

years.

In addition to the expense associated with our stock option plans, during the

three

-month period ended

March

31,

2016

we recorded stock-based compensation expense of

$469,799

(allocated to general and administrative expense) related to modifications made to certain stock purchase warrants.

Common Stock Reserved

A summary of our common stock reserved for future issuance as of

March

31,

2017

is as follows:

Series B Convertible Preferred Stock			285,714
Series C Convertible Preferred Stock			57,363,520
Common Stock Purchase Warrants			30,656,243
Equity Incentive Plans			4,590,300
Total			92,895,777