Stockholders’ equity

Recent issuances

On February 12, 2020, the Company completed a public offering of 10,350,000 Common Shares. Net proceeds to the Company were $14.5 million after deducting discounts, fees, and expenses.

Warrants

The following table summarizes information about outstanding warrants at March 31, 2020:



	Number of warrant shares	Weighted average exercise price
Outstanding at December 31, 2019	1,662,304		$3.25
Outstanding at March 31, 2020	1,662,304		$3.25
Exercisable at March 31, 2020	1,662,304		$3.25

Share-based compensation

Restricted stock

A summary of the Company’s shares of restricted stock as of March 31, 2020, is as follows:



	Shares		Weighted average grant date fair value
Balance at December 31, 2019	39,900			$3.51
Granted	100,319		1.88
Vested	(40,626	)	2.01
Balance at March 31, 2020	99,593			$2.00

During the three months ended March 31, 2020 and 2019, the Company expensed $84 thousand and $91 thousand, respectively, related to the restricted stock awards. At March 31, 2020, the balance of unearned share-based compensation to be expensed in future periods related to the restricted stock awards is $196 thousand. The period over which the unearned share-based compensation is expected to be earned is approximately 3.0 years.

Stock options

The Company’s option activity is summarized as follows:



	Number of options		Weighted average exercise price
Outstanding at December 31, 2019	573,925			$4.94
Issued	98,458		1.97
Expired	(14,835	)	11.62
Outstanding at March 31, 2020	657,548			$4.35
Exercisable at March 31, 2020	524,398			$4.93

Unless otherwise indicated, options issued to employees, members of the Board of Directors, and non-employees are vested over one to three years and are exercisable for a term of ten years from the date of issuance.

The fair values of stock option grants to employees and members of the Board of Directors during 2020 were measured on the date of grant using Black-Scholes, with the following weighted average assumptions:



	March 2020	January 2020
Expected volatility	102%	101%
Risk free interest rate	0.66%	1.67%
Expected dividend yield	0%	0%
Expected life (in years)	5	5

The weighted average fair value of stock options granted during the three months ended March 31, 2020, was $1.48.

The total intrinsic value of all options outstanding was $0 and $1 thousand at March 31, 2020, and December 31, 2019, respectively. The total intrinsic value of exercisable options was $0 at March 31, 2020, and December 31, 2019, respectively.

The following table summarizes information about options outstanding and exercisable at March 31, 2020:



Weighted average exercise price of outstanding options	Number of options outstanding	Weighted average remaining estimated life (in years)	Number of options exercisable	Weighted average exercise price of outstanding and exercisable options
$1.88 - $2.50	525,519	9.0	392,369
$3.30 - $6.90	37,139	2.3	37,139
$7.50 - $10.80	21,303	4.1	21,303
$14.20 - $23.40	73,587	6.1	73,587
	657,548		524,398	$4.93

Total share-based compensation on stock options amounted to $121 thousand and $48 thousand for the three months ended March 31, 2020 and 2019, respectively. At March 31, 2020, the balance of unearned share-based compensation to be expensed in future periods related to unvested share-based awards was $204 thousand. The period over which the unearned share-based compensation is expected to be earned is approximately 3.0 years.