Warrants (Tables)

9 Months Ended

Sep. 30, 2020

Warrant [Abstract]

Summary of Assumptions using Black- Scholes Option Pricing Model to estimate fair value

The aggregate fair value of the 2018 Offering Warrants of $7.4 million was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Upon Issuance
Common Stock Warrants:
Expected term (in years)		7.0
Expected volatility (%)	62.5%
Risk-free interest rate (%)	2.8%
Expected dividend yield (%)	0%

The fair value of the 2016 and 2017 Placement Warrants at September 30, 2020 and December 31, 2019, respectively, was estimated using the Black-Scholes option-pricing model and the following weighted-average assumptions:

	2017 Placement Warrants				2016 Placement Warrants
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Expected term (in years)		3.3		4.0		2.9		3.6
Expected volatility	77.9%		68.0%		77.0%		67.5%
Risk-free interest rate	0.2%		1.7%		0.2%		1.6%
Expected dividend yield	0.0%		0.0%		0.0%		0.0%

Schedule of Key Terms of Placement Warrants

The key terms of the 2017 and 2016 Placement Warrants are as follows:

	Issuance Date	Term	Exercise Price Per Share		Warrants Exercised during the Nine Months Ended September 30, 2020		Warrants Outstanding at September 30, 2020
2017 Placement Warrants	January 2017	7 years	$	3.17		—		1,618,890
2016 Placement Warrants	August and September 2016	7 years	$	2.95		—		537,263
Total						—		2,156,153