Exhibit 12.1

Computation of Ratio of Earnings to Fixed Charges

	Year ended December 31,
	2011			2012			2013			2014			2015
Fixed charges:
Interest expense	$	90		$	86		$	82		$	108		$	1,365
Estimate of interest expense within rental expense		220			104			84			266			339
Total fixed charges	$	310		$	190		$	166		$	374		$	1,704
Earnings before fixed charges:
Net loss before provision for income taxes	$	(2,318	)	$	(121,287	)	$	(111,985	)	$	(135,789	)	$	(220,030	)
Add fixed charges		310			190			166			374			1,704
Total earnings (loss) before fixed charges	$	(2,008	)	$	(121,097	)	$	(111,819	)	$	(135,415	)	$	(218,326	)
Deficiency of earnings to cover fixed charges:	$	(2,318	)	$	(121,287	)	$	(111,985	)	$	(135,789	)	$	(220,030	)