not consecutive, during any 30 consecutive VWAP Trading Day period commencing on or after the date we first issued the 2019 Notes. (Mandatory Conversion Option).
Upon conversion, converting noteholders will be entitled to receive accrued interest on their converted 2019 Notes. In addition, if the 2019 Notes are converted with a conversion date that is on or prior to November 1, 2020, other than in connection with our exercise of our Mandatory Conversion Option then the consideration due upon any such conversion will also include a cash interest make-whole payment for all future scheduled interest payments on the converted 2019 Notes through November 1, 2020 (2019 Notes Interest Make-Whole Provision).
We assessed all terms and features of the 2019 Notes in order to identify any potential embedded features that would require bifurcation. As part of this analysis, we assessed the economic characteristics and risks of the 2019 Notes, including the conversion, put and call features. In consideration of the 2019 Notes Interest Make-Whole Provision, we concluded the provision required bifurcation as a derivative. It was determined that the fair value of the derivative upon the November 14, 2019 and December 23, 2019 issuance of the 2019 Notes was $0.2 million in aggregate; and we recorded this amount as a derivative liability and the offsetting amount as a debt discount as a reduction to the carrying value of the 2019 Notes on the closing dates. It was determined that the fair value of the derivative at December 31, 2019 was $0.5 million.
During the first three months of six month period ended June 30, 2020, 2019 Note holders converted $57.4 million aggregate principal of 2019 Notes in exchange for 34,796,350 shares of common stock and $1.8 million of cash for 2019 Interest Make-Whole Provision. We recorded the change in fair value of the 2019 Interest Make-Whole Provision of $1.3 million for the six months ended June 30, 2020 as other expense in the condensed consolidated statement of operations and comprehensive loss. We determined that all other features of the 2019 Notes were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to our condensed consolidated financial statements. As of June 30, 2020, all 2019 Notes have converted into shares of common stock.
As of June 30, 2020, there was $28.3 million aggregate principal amount outstanding of the 2018 Notes compared to $28.3 million and $57.4 million aggregate principal amount outstanding of the 2018 Notes and 2019 Notes, respectively, for a total of $85.7 million aggregate principal amount outstanding as of December 31, 2019.
On March 21, 2017 (Closing Date), we entered into a term loan facility of up to $25.0 million with Hercules, a Maryland corporation. The term loan facility is governed by a loan and security agreement, dated March 21, 2017 (the Original Loan Agreement), which originally provided for up to four separate advances, of which an aggregate of $15.0 million were drawn down during the year ended December 31, 2017. The Original Loan Agreement was amended on January 4, 2018, March 6, 2018, October 11, 2018, April 23, 2019, and November 14, 2019 (the Amended Loan Agreement) to increase the total borrowing limit under the Original Loan Agreement from up to $25.0 million to up to $75.0 million, pursuant to certain conditions of funding.
Per the terms of the Amended Loan Agreement, the we may borrow up to an aggregate of $75.0 million, of which $35.0 million was outstanding immediately as of April 23, 2019 (Fourth Amendment Date) (Amended Term A Loan) as a result of the existing outstanding principal of term loans of $25.0 million being converted into the Amended Term A Loan, and an additional $10.0 million being drawn on the Fourth Amendment Date. The remaining $40.0 million of borrowing capacity may be drawn in multiple tranches comprised of (i) a term loan in an amount of up to $15.0 million upon us generating cumulative net product revenues (as defined in the Amended Loan Agreement) of either (a) $37.5 million on or before April 30, 2020 or (b) $50.0 million on or before June 30, 2020 (Amended Term B Loan), and (ii) a term loan in an amount of up to $25.0 million available through December 31, 2021, subject to Hercules’ approval and certain other conditions specified in the Amended Loan Agreement (the Amended Term C Loan, and together with the Amended Term A Loan and Amended Term B Loan, the Amended Term Loan). As of June 30, 2020, the funding conditions for the Amended Term B Loan have not been met and expired on June 30, 2020. As of June 30, 2020, we have borrowed a total of $35.0 million in term loans.
The Amended Term Loan will mature on December 1, 2022. Each advance accrues interest at a floating per annum rate equal to the greater of (a) 9.75% or (b) the lesser of (i) 12.00% and (ii) the sum of (x) 9.75% plus (y) (A) the