SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Common Shares Excluded from the Calculation of Net Loss Per Common Share

The following table sets forth for the periods presented the potential common shares (prior to consideration of the treasury stock method) excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive, in thousands:

	At September 30,
	2018		2017
Options to purchase common stock		12,676		11,905
Unvested restricted common stock		16		159
		12,692		12,064

Cumulative Effect and Impact on Condensed Consolidated Balance Sheet and Consolidated Statement of Comprehensive Loss for Adoption of New Revenue Standard

The following table summarizes the cumulative effect to our condensed consolidated balance sheet upon the adoption of the new revenue standard on January 1, 2018, in thousands:

Condensed Consolidated Balance Sheet	Balance at December 31, 2017			Adjustments			Balance at January 1, 2018
Deferred revenue, current portion	$	41,705		$	(34,463	)	$	7,242
Deferred revenue, net of current portion	$	43,075		$	(33,747	)	$	9,328
Accumulated deficit	$	(2,147,685	)	$	68,210		$	(2,079,475	)

In accordance with the new revenue standard requirements, the following tables summarize the impact of adoption on our condensed consolidated balance sheet and condensed consolidated statement of comprehensive loss, in thousands:

	At September 30, 2018
Condensed Consolidated Balance Sheet	As Reported			Balances Without Adoption of New Revenue Standard			Effect of Change Higher/(Lower)
Deferred revenue, current portion	$	3,444		$	3,444		$	—
Deferred revenue, net of current portion	$	1,623		$	19,615		$	(17,992	)
Accumulated deficit	$	(2,629,531	)	$	(2,647,608	)	$	(18,077	)

	Three Months Ended September 30, 2018
Condensed Consolidated Statement of Comprehensive Loss	As Reported			Balances Without Adoption of New Revenue Standard			Effect of Change Higher/(Lower)
Net revenues from collaborators	$	1,609		$	2,307		$	(698	)
Net loss	$	(245,282	)	$	(244,584	)	$	698
Net loss per common share - basic and diluted	$	(2.43	)	$	(2.43	)	$	—

	Nine Months Ended September 30, 2018
Condensed Consolidated Statement of Comprehensive Loss	As Reported			Balances Without Adoption of New Revenue Standard			Effect of Change Higher/(Lower)
Net revenues from collaborators	$	53,415		$	103,548		$	(50,133	)
Net loss	$	(550,056	)	$	(499,923	)	$	50,133
Net loss per common share - basic and diluted	$	(5.48	)	$	(4.98	)	$	0.50