Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2019

Change in Derivative Liability

The change in the derivative liability for the years ended December 31, 2019, 2018 and 2017 consists of the following:

	Fair Value
Balance, December 31, 2016	$	862
Dividends		267
Change in fair value		1,295
Balance, December 31, 2017	$	2,424
Dividends		223
Change in fair value		(158	)
Settlement of a related party relationship		(2,489	)
Balance, December 31, 2018	$	—
Dividends		—
Change in fair value		—
Balance, December 31, 2019	$	—

Series 1 Preferred Stock

Fair Value Assumptions Used in Probability Weighted Approach and Monte Carlo Simulation Model

The fair value of the Series 1 preferred stock dividends was estimated using a probability-weighted approach and a Monte Carlo simulation model. The fair value of the embedded derivatives was estimated using the “with” and “without” method where the preferred stock was first valued with all of its features (“with” scenario) and then without derivatives subject to the valuation analysis (“without” scenario). The fair value of the derivatives was then estimated as the difference between the fair value of the preferred stock in the “with” scenario and the preferred stock in the “without” scenario. The model also takes into account, management estimates of clinical success/failure based upon market studies and probability of potential conversion and liquidation events. If these estimates were different, the valuations would change, and that change could be material. Inputs to the models included the following:

	December 31,
	2018
Risk-free interest rate	2.50 - 3.13%
Expected dividend rate	0
Expected volatility	77.6 - 82.4%
Preferred stock conversion limit - percentage of outstanding common stock	19.90%
Preferred conversion floor price	$1.00