Warrants to Acquire Shares of Common Stock (Tables)

9 Months Ended

Sep. 30, 2020

Warrants and Rights Note Disclosure [Abstract]

The following is a summary of the activity of the Company's warrants to acquire shares of common stock for the nine months ended September 30, 2020 (in thousands):


Warrant Issuance	Outstanding, December 31, 2019	Granted	Exercised	Canceled/Expired	Outstanding, September 30, 2020	Expiration
July 2020 PIPE Offering	—	2,744	—	—	2,744	August 2025
January 2020 Offering	—	819	—	—	819	July 2025
Pre-funded January 2020 Offering	—	449	(449)	—	—	July 2025
June 2019 Offering	2	—	—	—	2	June 2024

March 2019 Exercise Agreement	63	—	—	—	63	March 2024
July 2018 Offering	208	—	—	—	208	July 2023

Series A Convertible Preferred	19	—	—	—	19	September 2023
2017 Equilibria	6	—	—	—	6	December 2022
Galena February 2017	1	—	—	—	1	February 2022
Galena Other	3	—	—	(1)	2	January 2022






	302	4,012	(449)	(1)	3,864

Fair Value of Warrants is Estimated Using Black-Scholes Option Pricing Model

The fair value of the warrants is estimated using a Black-Scholes pricing model with the following inputs:


As of September 30, 2020

Warrant Issuance	Outstanding (in thousands)	Strike price (per share)		Expected term (years)	Volatility %		Risk-free rate %
Series A Convertible Preferred	19	$	7.50	3.00	131.54	%	0.16	%
Galena February 2017	1	$	1,650.00	1.37	135.60	%	0.13	%
Galena Other	2	$	30,901.09	1.29	135.60	%	0.13	%




As of December 31, 2019
Warrant Issuance	Outstanding (in thousands)	Strike price (per share)		Expected term (years)	Volatility %		Risk-free rate %
Series A Convertible Preferred	19	$	7.50	3.75	112.84	%	1.64	%
Galena February 2017	1	$	1,650.00	2.12	114.91	%	1.64	%
Galena Other	3	$	41,494.00	1.43	114.91	%	1.64	%

Changes in Fair Value of Warrant Liability

The changes in fair value of the warrant liability for the nine months ended September 30, 2020 were as follows (in thousands):


Warrant Issuance	Warrant liability, December 31, 2019		Fair value of warrants granted		Fair value of warrants exercised		Adjustment to exercise price of warrants		Change in fair value of warrants		Warrant liability, September 30, 2020
Series A Convertible Preferred	$	52	$	—	$	—	$	—	$	(25)	$	27
Galena February 2017	—		—		—		—		—		—





	$	52	$	—	$	—	$	—	$	(25)	$	27