4. Term Loan

On February 5, 2016, we entered into a loan and security agreement with Hercules Capital, Inc. (formerly known as Hercules Technology Growth Capital, Inc.) ("HC"), as administrative agent and lender, and Hercules Technology III, L.P., as lender ("Hercules"), pursuant to which the lenders made term loans to us on February 8, 2016 in the aggregate principal amount of $25 million (the "Term Loans").

The Term Loans bear interest at the daily variable rate per annum equal to 6.0% plus the prime rate, or 10.25%, whichever is greater. We are required to make interest-only payments on the Term Loans through February 28, 2017, and beginning on March 1, 2017 blended equal monthly installments of principal amortization and accrued interest until the maturity date of the Term Loans on February 1, 2020. Under the terms of the loan, we are required to maintain a minimum cash balance equal to the greater of (i) $10 million or (ii) forward three months projected cash burn. As security under our obligations, we issued to the lenders warrants to purchase a total of 105,691 shares of our common stock at an exercise price of $12.30. These warrants are classified as equity warrants with a fair value of $633,749. All outstanding principal and accrued interest on the term loans will be due and payable in full on the maturity date of February 1, 2020.

On July 28, 2017, we entered into a First Amendment to Loan and Security Agreement with Hercules to amend our existing long-term loan facility (the "Loan Agreement"). The amendment provides for our payment, on July 28, 2017, of $5.0 million in outstanding principal and unpaid interest due under the Loan Agreement, plus a $100,000 prepayment charge, and for our repayment, on or prior to September 30, 2017, of an additional $5.0 million outstanding principal and unpaid interest due under the Loan Agreement, plus a second $100,000 prepayment charge. Both those additional payments were made this quarter. We also agreed to an updated schedule of monthly payments and a new maturity date of August 1, 2018. Pursuant to the amendment, a portion of the warrants (representing 80% of the total number of shares issuable upon exercise of the warrants) was amended to change the exercise price of that portion of the warrants from $12.30 per share to $4.62 per share, which was calculated based upon the 30-day volume-weighted average price of our common stock over the 30-day period beginning 15 days before the July 28, 2017 announcement of the NantCell license transaction. We evaluated the amended debt agreement under ASC 470 and determined it to be a modification and that in accordance with accounting guidance for debt modifications, the incremental fair value of the repriced warrants of $77,000 and the $200,000 fee paid to the lender was recorded as additional loan discount to be recognized using the interest method over the remaining life of the loan. The payment schedule was changed and the future principal payments as of September 30, 2017 are $1.0 million for the remainder of 2017 and $10.0 million in 2018.

As security for our obligations under the loan and securities agreement, we granted HC, as administrative agent, a security interest in substantially all of our existing and after-acquired assets except for our intellectual property and certain other excluded assets. The loan and security agreement contains customary representations, warranties and covenants.

	September 30, 2017			December 31, 2016
Term Loan Principal – Current	$	10,999,522		$	6,214,057
End Fee Payable		1,771,250			—
Issuance Cost/Loan Discount – Current		(1,718,067	)		(732,401	)
Term Loan, Net – Current	$	11,052,705		$	5,481,656

Long Term Loan Principal	$	—		$	18,785,943
End Fee Payable		—			1,771,250
Long Term Loan Discount/Issuance Cost		—			(2,072,683	)
Long Term Loan, Net	$	—		$	18,484,510

The interest expense on the loan for the three-month and nine-month periods ended September 30, 2017 was $828,120 and $2,999,230, respectively, as compared to $781,038 and $1,939,186 for comparative 2016 periods.