Warrants (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Common Stock Warrants Outstanding

The following common stock warrants were outstanding at December 31, 2018:

	Number of Common Stock Warrants		Per Share Exercise Price		Issuance Date	Expiration Date
Replacement warrants issued in connection with the Mergers		155	$	483.00	March 3, 2012	March 3, 2022
Issued with redeemable preferred stock*		1,612		80.10	August 16, 2017	August 16, 2022
Issued with common units in Unit Offering		2,516,250		4.18	October 2, 2018	October 2, 2023
Underwriter warrant issued with public offering		196,650		6.25	October 2, 2018	September 28, 2021
Issued with common units in Registered Direct Offering		4,629,630		5.40	October 10, 2018	October 10, 2023
Total		7,344,297
*Liability classified warrants

The following common stock warrants were outstanding at December 31, 2017:

	Number of Common Stock Warrants		Per Share Exercise Price		Issuance Date	Expiration Date
Replacement warrants issued in connection with the Mergers		155	$	483.00	March 3, 2012	March 3, 2022
Issued with redeemable preferred stock*		78,181		80.10	August 16, 2017	August 16, 2022
Total		78,336
*Liability classified warrants

Summary of Key Assumptions Used in Calculating Marketability Discount

This amount is considered a marketability discount calculated based on an analysis of the leak out provision provided for in the exchange agreements. The key assumptions used in calculating the marketability discount were:

Holding period, in years	0.03
Risk free rate	1.77	%
Dividend yield	0	%
Volatility	109.9	%

Summary of Income Statement Effect of Changes in Outstanding Warrants

The following is a summary of the income statement effect of changes in the Company’s outstanding warrants:

	Twelve Months Ended December 31, 2018
Changes in fair value of warrants	$	(9,160	)
Loss on warrants exchanged		(2,688,012	)
Transaction costs		(181,312	)
Change in fair value of warrant liability, including gain (loss) on exchange	$	(2,878,484	)

Summary of Warrant Activity

A summary of warrant activity during the years ended December 31, 2018 and 2017 is as follows:

	Year Ended December 31,
	2018			2017
Warrants outstanding, January 1		78,336			20,404
Issuances		7,342,530			79,840
Replacement warrants issued in connection with the Mergers		—			155
Exercises, conversions and exchanges		(76,569	)		(22,063	)
Warrants outstanding, December 31		7,344,297			78,336

Assumptions Used to Estimate Fair Value of Embedded Redemption Derivative Financial Instrument

The fair value used to determine the initial carrying value of the embedded redemption derivative financial instrument was measured using Level 3 inputs and was estimated using the Monte Carlo simulation valuation model. The assumptions used to estimate the fair value of the embedded redemption derivative financial instrument at December 31, 2017 and as of the redeemable preferred stock issuance date were as follows:

	December 31, 2017
Expected volatility		59.60	%
Incremental borrowing rate		12.00	%
Risk-free interest rate		1.59	%

Summary of Periodic Changes in Fair Value of Warrant Liability

The periodic changes in the fair value of the warrant liability is as follows:

Balance, January 1, 2017	$	—
Issuance		3,498,632
Changes in fair value		(97,763	)
Balance, December 31, 2017		3,400,869
Warrants settled upon exchange		(3,345,029	)
Changes in fair value		9,160
Balance, December 31, 2018	$	65,000

Black Scholes Option Pricing Model [Member]

Assumptions Used to Estimate Fair Value of Embedded Redemption Derivative Financial Instrument

The fair value used to determine the initial carrying value of the August 2017 warrants was measured using Level 3 inputs and was estimated using the Black-Scholes option pricing model. The following assumptions were used to estimate the fair value of the August 2017 warrants outstanding during the years ended December 31, 2018 and 2017:

	March 9, 2017 Issuance
Expected volatility		84.40	%
Expected term (years)		5.00
Risk-free interest rate		2.13	%
Expected dividend yield		0.00	%

Monte Carlo Simulation Model [Member]

Assumptions Used to Estimate Fair Value of Embedded Redemption Derivative Financial Instrument

The following assumptions were used to estimate the fair value of warrants classified as a liability using the Monte Carlo simulation valuation model with Level 3 inputs at December 31, 2018, December 31, 2017, and the redeemable preferred stock issuance date of August 16, 2017 were as follows:

	December 31, 2018			December 31, 2017			August 16, 2017
Expected volatility		93.90	%		91.30	%		86.90	%
Expected term (years)		3.60			4.60			5.00
Risk-free interest rate		2.48	%		2.16	%		1.76	%
Expected dividend yield		0.00	%		0.00	%		0.00	%