5.Debt

On June 29, 2012, the Company and its domestic subsidiaries, as co-borrowers, entered into a Loan and Security Agreement with Hercules Technology Growth Capital, Inc. (“Hercules”) that originally allowed the Company to borrow up to $20.0 million (“Loan Agreement”) at an interest rate of 9.25%. Most recently, on December 15, 2014, the Company and Hercules entered into a third amendment (the “Third Amendment”) to the Loan Agreement. In connection with the Third Amendment, the Company paid a commitment fee of $25,000, and at the closing, paid a facility fee of $125,000. Under the Third Amendment, the amount of borrowings was increased by $5.0 million to a total of $25.0 million and the interest-only period was extended through December 31, 2015. In addition, in the event the Company receives at least $90.0 million in cash proceeds from the completion of certain types of equity financings, subordinated debt financings, and/or up-front cash payments from corporate transactions prior to December 31, 2015, the Company has the option to extend the maturity date of the loan to January 1, 2018. If the Company elects to exercise such option, it must pay Hercules a $250,000 fee. The Company completed an equity financing in April 2015 in excess of $90.0 million (see Note 10 for more information).

The following table presents the components of the Company’s debt balance as of March 31, 2015 (in thousands):

Debt:
Notes payable	$	25,000
Accretion of end of term charge	333
Issuance fees paid to lender	(231		)
Discount from warrant	(113		)
Current portion of long-term debt	(24,989		)
Long-term debt	$	—

As of March 31, 2015, future principal repayments of the debt for each of the years ending December 31, 2015 and 2016 were as follows (in thousands):

Year Ending in December 31:
2015	$	—
2016 (due in full January 1, 2016)	25,000
	$	25,000

The estimated fair value of the debt (categorized as a Level 2 liability for fair value measurement purposes) is determined using current market factors and the ability of the Company to obtain debt at comparable terms to those that are currently in place. The Company believes the estimated fair value at March 31, 2015 approximates the carrying amount.