EXHIBIT 12.1

Statement of Computation of Ratio of Earnings to Fixed Charges and Ratio of Combined
Fixed Charges and Preferred Stock Dividends

(in thousands, except ratios)

	Year Ended December 31,															Six Months Ended June 30,
	2013			2014			2015			2016			2017			2018
EARNINGS
Net (loss)	$	(25,382	)	$	(12,035	)	$	(27,660	)	$	(52,894	)	$	(92,064	)	$	(57,175	)
Plus:
Fixed Charges (see below)	$	504		$	21		$	85		$	190		$	327		$	158
Total (loss) to cover fixed charges	$	(24,878	)	$	(12,014	)	$	(27,575	)	$	(52,704	)	$	(92,064	)	$	(57,017	)
FIXED CHARGES
Interest expense	$	446		$	-		$	-		$	-		$	-		$	-
Amortization of debt discount	$	-		$	-		$	-		$	-		$			$	-
Rental expenses representative of an interest factor (1)	$	58		$	21		$	85		$	190		$	327		$	158
Total fixed charges	$	504		$	21		$	85		$	190		$	327		$
Preferred dividends	$	-		$	-		$	-		$	-		$	-		$
DEFICIENCY OF EARNINGS TO COVERED CHARGES	$	(25,382	)	$	(12,035	)	$	(27,660	)	$	(52,894	)	$	(92,064	)	$	(57,175	)
RATIO OF EARNINGS TO FIXED CHARGES																	-
RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED DIVIDENDS																	-

(1)       Represents the estimated interest factor associated with certain facility lease expenses at an assumed rate of 33% of total rent expense, which management believes is a reasonable estimation of the interest factor.