Note 13 - Warrants

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Warrants [Text Block]

13.

WARRANTS

As more fully described in Note

10,

the Company completed a series of equity financing transactions in

201

7

and

2016

that included the issuance of warrants to purchase

9,231,628

and

1,147,595

shares, respectively, of the Company’s common stock. Investors exercised warrants to purchase

7,617,147

shares of common stock providing

$22.0

million in gross proceeds to the Company during

2017.

We did

not

have any option or warrant exercises during

2016

other than

17,857

shares related to the Pre-funded Series B Warrants as discussed more fully in Note

10.

Following is a summary of all warrant activity for the

two

years ended

December 31,

201

7:

Warrants	Number of Warrants Issued			Weighted Average Exercise Price
Warrants outstanding at January 1, 2016		421,015		$	58,88
Warrants issued in connection with 2016 equity transactions		1,147,595		$	2.03
Warrants exercised during 2016		(17,857	)	$	0.14
Warrants expired during 2016		(62,795	)	$	209.23
Warrants outstanding at December 31, 2016		1,487,958		$	9.39
Warrants issued in connection with 2017 equity transactions		9,231,628		$	3.46
Warrants exercised during 2017		(7,617,147	)	$	2.89
Warrants expired during 2017		(44,037	)	$	174.58
Warrants outstanding at December 31, 2017		3,058,402		$	5.29
Aggregate intrinsic value of outstanding warrants at December 31, 201 7	$	37,143
Weighted average remaining contractual terms (years)		3.5