Note 5 - Stockholders' Equity and Common Stock Warrants

3 Months Ended

Mar. 31, 2020

Notes to Financial Statements

Stockholders' Equity Note Disclosure [Text Block]

5. Stockholders' Equity and Common Stock Warrants

2019

Common Stock Offerings

In

December 2019,

the Company completed an offering (the

“December 2019

Offering”) of

6,266,787

shares of its common stock and warrants to purchase

6,266,787

shares of common stock. The shares of common stock and warrants were sold for a combined purchase price of

$0.5585

per share for net proceeds of

$3.0

million. The

December 2019

Offering warrants are exercisable beginning on the date of their issuance until

June 13, 2025

at an initial exercise price equal to

$0.4335

per share.

In addition, at the closing of the

December 2019

Offering, the Company issued warrants to purchase up to

313,339

shares of common stock to designees of the placement agent. The placement agent's warrants have an exercise price of

$0.6981

per share and a term of

five

years from the date of issuance.

In

November 2019,

the Company completed a registered direct public offering (the

“November 2019

Offering”) of

5,104,429

shares of its common stock, and

6,324,143

pre-funded warrants each to purchase

one

share of common stock, together with warrants to purchase up to

22,857,144

shares of common stock at a combined public offering price of

$0.35

per share and associated warrants for total net proceeds of

$3.3

million. The warrants were issued with an exercise price of

$0.35

per warrant and are exercisable beginning on their date of issuance. Of the warrants issued,

11,428,572

have a term of

18

months and

11,428,572

have a term of

five

years. During the year ended

December 31, 2019,

11,091,716

of those warrants were exercised for proceeds of

$3.9

million.

In addition, at the closing of the

November 2019

Offering, the Company issued warrants to purchase up to

571,429

shares of common stock to designees of the placement agent. The placement agent's warrants have an exercise price of

$0.4375

per share and a term of

five

years from the date of issuance.

In

May 2019,

the Company completed a registered direct public offering (the

“May 2019

Offering”) of

1,317,060

shares of common stock and a private placement of warrants to purchase

1,317,060

shares of common stock. The shares of common stock and warrants were sold for a combined purchase price of

$4.895

for total net proceeds of

$5.6

million. The warrants are exercisable beginning on the date of their issuance until

November 29, 2024

at an initial exercise price equal to

$5.00.

In addition, at the closing of the

May 2019

Offering, the Company issued warrants to purchase up to

65,853

shares of common stock to designees of the placement agent. The placement agent's warrants have an exercise price of

$6.11875

per share and a term of

five

years from the date of issuance.

Common Stock Warrants

As of

March 31, 2020,

the Company had the following warrants outstanding to acquire shares of its common stock:

	Outstanding		Range of exercise price per share			Expiration dates
Common stock warrants issued in 2017 related to Series A convertible preferred stock offering		903,870		$33.30		March 2022
Common stock warrants issued in 2018 related to the common stock offering		1,181,375	$12.00	-	$15.00	January 2023
Common stock warrants issued related to the May 2019 Offering		1,382,913	$5.00	-	$6.11875	May and December 2024
Common stock warrants issued related to the November 2019 Offering		11,212,786	$0.35	-	$0.4375	May 2024
Common stock warrants issued related to the December 2019 Offering		6,580,126	$0.4335	-	$0.6981	December 2024 and June 2025
		21,261,070

During the

three

months ended

March 

31,

2020,

no

warrants expired, and

1,124,071

warrants were exercised at an exercise price of

$0.35

per warrant.