10. INDEBTEDNESS

2024 Convertible Notes

In November 2017, the Company issued $570.0 million senior notes due on November 15, 2024 (the “2024 Notes”). The 2024 Notes were issued at face value and bear interest at the rate of 1.50% per annum, payable semi-annually in cash on each May 15 and November 15, commencing on May 15, 2018. There are no principal payments due prior to maturity. Upon conversion, the Company may pay cash, shares of its common stock or a combination of cash and stock, as determined by the Company in its discretion. The 2024 Notes may be convertible into 7,763,552 shares of the Company’s common stock under certain circumstances prior to maturity at a conversion rate of 13.621 shares per $1,000 principal amount of the 2024 Notes, which represents a conversion price of $73.42 per share. The Company recorded a total debt discount of $171.8 million upon issuance of the 2024 Notes, consisting of an equity component of $161.2 million and debt issuance costs of $10.6 million. The debt discount is being amortized under the effective interest method and recorded as additional non-cash interest expense over the life of the 2024 Notes. The effective interest rate on the liability component of the 2024 Notes for the year ended December 31, 2017 was 6.9%. The fair value of the 2024 Notes is $1.3 billion as of September 30, 2018. It is based on open market trades and is classified as level 1 in the fair value hierarchy.

Term Loan

In July 2017, the Company entered into an amended and restated credit agreement (the “Amended and Restated Credit and Security Agreement”) which provides a term loan (“July 2017 Term Loan”) of $60.0 million with MidCap Financial Trust (“MidCap”). Borrowings under the Amended and Restated Credit and Security Agreement bear interest at a rate per annum equal to 6.25%, plus the one-month London Interbank Offered Rate (“LIBOR”). Commencing on July 1, 2018, and continuing for the remaining thirty six months of the facility, the Company was required to make monthly principal payments of approximately $0.8 million, set forth in the Amended and Restated Credit and Security Agreement, subject to certain adjustments as described therein.

Revolving Line of Credit

In July 2017, the Company entered into a revolving credit and security agreement (the “Revolving Credit Agreement”) which provides an aggregate revolving loan commitment of $40.0 million (which may be increased by an additional tranche of $20.0 million) with MidCap. Borrowings under the Revolving Credit Agreement bear interest at a rate of 3.95%, plus the one-month LIBOR. In addition to paying interest on the outstanding principal under the Revolving Credit Agreement, the Company paid $0.2 million of origination fee, which was 0.50% of the amount of the revolving loan. The Company recognized this origination fee as an other asset and it was being amortized to interest expense over the term of the line-of-credit. Additionally, the Company was liable for unused line fees, minimum balance fees, collateral fees, deferred revolving loan original fees, etc.

In September 2018, the Company terminated the Amended and Restated Credit and Security Agreement and the Revolving Credit Agreement with MidCap and paid off the remaining outstanding balance of principal and accrued and unpaid interest on the July 2017 Term Loan. As a result, the Company recorded a debt extinguishment loss of $2.3 million primarily related to the write-off of unamortized debt issuance costs and prepayment fees.

As of September 30, 2018, the Company recorded approximately $415.4 million as long-term debt on the unaudited condensed consolidated balance sheets related to the 2024 Notes. The following table summarizes the Company’s debt facilities for the periods indicated:

	As of September 30, 2018			As of December 31, 2017
	(in thousand)
Par value of the 2024 Notes		570,000			570,000
Unamortized discount - equity component		(144,999	)		(158,890	)
Unamortized discount - debt issuance costs		(9,555	)		(10,449	)
Net carrying value of convertible debt		415,446			400,661
Other debt facilities		—			30,390
Net carrying value of total debt facilities		415,446			431,051

For the three months and nine months ended September 30, 2018, the Company recorded $10.7 million and $26.5 million in interest expense, respectively. For the three months and nine months ended September 30, 2017, the Company recorded $0.8 million and $1.2 million in interest expense, respectively.