Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2020

Stockholders' Equity

Schedule of warrants outstanding and exercisable for purchase of common stock

	Number of Shares
	March 31,	December 31,	Weighted-Average
Description	2020	2019	Exercise Price		Expiration Date
Liability-classified Warrants
December 2019 Series B1 warrants (1)	2,368,400	2,368,400		$ 1.52	Dec 2026
	2,368,400	2,368,400
Equity-classified Warrants
May 2013 warrants	1,949,754	1,949,754		$ 0.08	None
September 2013 warrants	514,756	514,756		$ 0.08	None
February 2014 warrants	266,006	266,006		$ 0.08	None
	2,730,516	2,730,516
Total outstanding	5,098,916	5,098,916

The Series B1 warrants are exercisable for either common stock (exercise price of $1.52) or Series B1 Convertible Preferred Stock (exercise price of $152) at the discretion of the warrant holder.