Warrant Liabilities (Tables)

12 Months Ended

Dec. 31, 2018

Series C Warrant [Member]

Fair Value of Convertible Preferred Stock Warrant Liability

The Company used the following inputs.

	December 31, 2018			December 31, 2017
Volatility		90	%		90	%
Contractual term (years)		1.17			2.17
Expected dividend yield		—	%		—	%
Risk-free rate		2.60	%		1.57	%

2017 PIPE Warrant Liability [Member]

Fair Value of Convertible Preferred Stock Warrant Liability

The following summarizes certain key assumptions used in estimating the fair values.

	December 31, 2018			December 31, 2017
Volatility		75	%		67	%
Contractual term (years)		0.8			0.8
Expected dividend yield		—	%		—	%
Risk-free rate		2.51	%		1.76	%

2018 PIPE Warrant Liability [Member]

Fair Value of Convertible Preferred Stock Warrant Liability

The following summarizes certain key assumptions used in estimating the fair values.

	December 31, 2018			December 19, 2018 (date of issue)
Volatility		75	%		75	%
Contractual term (years)		5.0			5.0
Expected dividend yield		—	%		—	%
Risk-free rate		2.51	%		2.62	%