Carrying amount of principal borrowings consist of the following (in thousands):

	September 30, 2020			December 31, 2019
Mann Group promissory notes	$	70,025		$	70,020
Midcap Credit Facility		39,346			38,851
Senior notes (December 2020 note and 2024 convertible notes)		7,581			10,028
PPP Loan		4,873			—
Total debt — net carrying amount		121,825			118,899
Less current portion of long-term debt		(45,379	)		(5,028	)
Long-term debt	$	76,446		$	113,871

Amount Due

Terms

September 30, 2020

December 31, 2019

Annual Interest Rate

Maturity Date

Conversion Price

Mann Group convertible

note

$35.0 million (plus $2.9 million accrued interest paid-in-kind)

$35.0 million (plus $1.0 million accrued interest paid-in-kind)

7.00%

November 2024

$2.50

per share

Mann Group non-

convertible note

$35.1 million (plus $2.9 million accrued interest paid-in-kind)

$35.1 million (plus $1.0 million accrued interest paid-in-kind)

7.00%

November 2024

N/A

MidCap Credit

Facility

$40.0 million

one-month

LIBOR (2% floor)

plus 6.75%

August 2024

N/A

2024 convertible notes

$5.0 million

5.75%

November 2024

$3.00

per share

June 2020 note

—

$2.6 million

—

June 2020

N/A

December 2020 note

$2.6 million

—

December 2020

N/A

PPP Loan

$4.9 million

—

0.98%

April 2022

N/A

The maturities of our borrowings as of September 30, 2020 are as follows (in thousands):

	Amounts
2020	$	4,254
2021		6,881
2022		14,146
2023		13,333
2024		83,940
Thereafter		—
Total principal payments		122,554
Unamortized discount		(306	)
Unamortized debt issuance costs		(423	)
Total debt — net carrying amount	$	121,825

Current Portion of Long-Term Debt — As of September 30, 2020, the current portion of long-term debt was $45.4 million and consisted of $40.0 million of the MidCap Credit Facility, $3.5 million of the PPP Loan and $2.6 million of the December 2020 note.

MidCap Credit Facility — In August 2019, the Company closed the MidCap Credit Facility, which provides a secured term loan facility with an aggregate principal amount of up to $75.0 million. The Company borrowed the first advance of $40.0 million (“Tranche 1”) on August 6, 2019. Under the terms of the MidCap Credit Facility, the second advance of $10.0 million (“Tranche 2”) was available to the Company until April 15, 2020, provided that the Company had achieved Afrezza net revenue of at least $30.0 million on a trailing twelve month basis by that date (which was not achieved). The third advance of $25.0 million (“Tranche 3”) will be available to the Company until June 30, 2021, subject to the satisfaction of certain milestone conditions associated with Afrezza trailing net revenue and certain milestone conditions related to the Company’s collaboration with United Therapeutics (see Note 7 – Collaboration and Licensing Arrangements). In August 2019, the Company recognized a $1.5 million commitment asset and a $0.4 million other asset for deferred debt issuance costs related to the future funding commitments of the MidCap Credit Facility. The Company determined that such milestone conditions related to Afrezza trailing net revenue were unlikely to be achieved. As a result, the Company recognized an asset impairment of $1.9 million during the second quarter of 2020.

In December 2019, the Company entered into an amendment to the MidCap Credit Facility, pursuant to which the parties agreed to (i) amend the financial covenant relating to trailing twelve month minimum Afrezza Net Revenue (as defined in the MidCap Credit Facility) requirements, (ii) add a condition to the third advance of $25.0 million that requires the Company achieve certain amounts of Afrezza Net Revenue, and (iii) increase the exit fee from 6.00% to 7.00% of the principal amount of all term loans advanced to the Company under the MidCap Credit Facility.

In August 2020, the Company entered into an amendment to the MidCap Credit Facility, pursuant to which the parties agreed that no breach of the minimum Afrezza net revenue covenant for any trailing twelve-month reporting period between July 31, 2020 and November 30, 2020 will be deemed to occur if the Company delivers satisfactory evidence that it had unrestricted cash of at least $40.0 million. Without this amendment, the Company would have been in violation of the minimum Afrezza net revenue covenant as of September 30, 2020. After the November 30, 2020 reporting period, the amendment will expire and a breach of the minimum Afrezza net revenue covenant is probable. The Company intends to amend the MidCap Credit Facility to address this probable covenant violation; however, such amendment, if completed, would occur after the date of this report. Accordingly, the $40.0 million outstanding principal under the MidCap Credit Facility was classified as current debt in the September 30, 2020 balance sheet, even though the 36 equal monthly principal payments remain payable over the period of September 1, 2021 through August 1, 2024. This debt will continue to be classified as current unless the MidCap Credit Facility is further amended or the debt is repaid.

Tranche 1 and, if borrowed, Tranche 3, each accrue interest at an annual rate equal to one-month LIBOR plus 6.75%, subject to a one-month LIBOR floor of 2.00%. Interest on each term loan advance is due and payable monthly in arrears. Principal on the term loan advance under Tranche 1 is payable in 36 equal monthly installments beginning September 1, 2021, until paid in full on August 1, 2024, and principal on any term loan advance under Tranche 3 is payable beginning on the later of (i) September 1, 2021, and (ii) the first day of the first full calendar month immediately following such term loan advance, in an amount equal to the outstanding term loan advance in respect of Tranche 3 divided by the number of full calendar months remaining before August 1, 2024. The Company has the option to prepay the term loans, in whole or in part, subject to early termination fees in an amount equal to 3.00% of principal prepaid if prepayment occurs on or prior to the first anniversary of the closing date, 2.00% of principal prepaid if prepayment occurs after the first anniversary of the closing date but on or prior to the second anniversary of the closing date, and 1.00% of principal prepaid if prepayment occurs after the second anniversary of the closing date and prior to or on the third anniversary of the closing date. In connection with execution of the MidCap Credit Facility, the Company paid MidCap a $0.4 million origination fee.

The Company’s obligations under the MidCap Credit Facility are secured by a security interest on substantially all of its assets, including intellectual property.

The MidCap Credit Facility contains customary affirmative covenants and customary negative covenants limiting the Company’s ability and the ability of the Company’s subsidiary to, among other things, dispose of assets, undergo a change in control, merge or consolidate, make acquisitions, incur debt, incur liens, pay dividends, repurchase stock and make investments, in each case subject to certain exceptions. The Company must also comply with a financial covenant relating to trailing twelve month minimum Afrezza net revenue, tested on a monthly basis, and a minimum cash covenant of $15.0 million at all times, and $20.0 million at all times following the funding of Tranche 3. For any trailing twelve-month reporting period between July 31, 2020 and November 30, 2020, the minimum Afrezza net revenue test will be deemed to occur if the Company delivers satisfactory evidence that it had unrestricted cash of at least $40.0 million. As of September 30, 2020, the Company was in compliance with the financial and minimum cash covenants.

The MidCap Credit Facility also contains customary events of default relating to, among other things, payment defaults, breaches of covenants, a material adverse change, listing of the Company’s common stock, bankruptcy and insolvency, cross defaults with certain material indebtedness and certain material contracts, judgments, and inaccuracies of representations and warranties. Upon an event of default, the agent and the lenders may declare all or a portion of the Company’s outstanding obligations to be immediately due and payable and exercise other rights and remedies provided for under the MidCap Credit Facility. During the existence of an event of default, interest on the term loans could be increased by 2.00%.

The Company also agreed to issue warrants to purchase shares of the Company’s common stock (the “MidCap warrants”) upon the drawdown of each term loan advance under the MidCap Credit Facility in an aggregate amount equal to 3.25% of the amount drawn, divided by the exercise price per share for that tranche. The exercise price per share is equal to the volume-weighted average closing price of the Company’s common stock for the ten business days immediately preceding the second business day before the issue date. As a result of Tranche 1, the Company issued warrants to purchase an aggregate of 1,171,614 shares of the Company’s common stock, at an exercise price equal to $1.11 per share. The MidCap warrants are immediately exercisable and expire on the earlier to occur of the seventh anniversary of the respective issue date or, in certain circumstances, the closing of a merger, sale or other consolidation transactions in which the consideration is cash, stock of a publicly traded acquirer, or a combination thereof.

The Company determined that these warrants met the criteria for equity classification and accounted for such warrants in additional paid-in capital.

Senior Notes — As of September 30, 2020 and December 31, 2019, there was $7.6 million and $10.2 million, respectively, of principal amount of senior notes outstanding.

In August 2019, the Company entered into a privately-negotiated exchange agreement with the holder of the 5.75% Convertible Senior Subordinated Exchange Notes due 2021 (the “2021 notes”), pursuant to which, among other things, the Company (i) repaid $1.5 million in cash to such holder, (ii) issued 4,017,857 shares of the Company’s common stock to such holder (at a conversion price of $1.12 per share), (iii) issued 5.75% Convertible Senior Subordinated Exchange Notes due November 2024 (the “2024 convertible notes”) to such holder in the principal amount of $5.0 million and (iv) issued a $2.6 million note due June 2020 (the “June 2020 note”), a $2.6 million note due December 2020 (the “December 2020 note”, and together with the June 2020 note, the “2020 notes”), all in exchange for the cancellation of the $18.7 million in principal amount of the 2021 notes. The 2020 notes may be prepaid at any time on or prior to their respective maturity dates of June 30, 2020 and December 31, 2020 at the option of the Company. On June 24, 2020, the Company prepaid the June 2020 note with the issuance of 1,235,094 shares of the Company’s common stock, pursuant to the Company’s election and in accordance with the terms of the June 2020 note. On October 9, 2020, the Company prepaid the December 2020 note with the issuance of 1,377,356 shares of the Company’s common stock, pursuant to the Company’s election and in accordance with the terms of the December 2020 note. The number of shares issued for the prepayments on June 24, 2020 and October 9, 2020 were determined based on the Company’s closing stock price on the settlement date. As a result of the prepayment of the December 2020 note on October 9, 2020, the Company recognized a de minimis amount of loss on extinguishment related to unamortized debt discount.

The 2024 convertible notes were issued pursuant to an indenture, dated as of August 6, 2019, between the Company and U.S. Bank National Association, as trustee (the “Indenture”). The 2024 convertible notes are the Company’s general, unsecured obligations, and are subordinated in right of payment to the indebtedness incurred pursuant to the MidCap Credit Facility. The 2024 convertible notes rank equally in right of payment with the Company’s other unsecured senior debt. The 2024 convertible notes accrue interest at the rate of 5.75% per year on the principal amount, payable semiannually in arrears on February 15 and August 15 of each year, beginning February 15, 2020, with interest accruing from August 6, 2019. Interest on the 2024 convertible notes will be payable in cash or, at the option of the Company if certain conditions are met, in shares of the Company’s common stock at a price per share equal to the last reported sale price on the trading day immediately prior to the interest payment date. The 2024 convertible notes will mature on the earlier of (i) November 4, 2024 or (ii) the 91^st day after the payment in full of, and termination and discharge of all obligations (other than contingent indemnity obligations) under the MidCap Credit Facility.

The 2024 convertible notes are convertible, at the option of the holder, at any time on or prior to the close of business on the business day immediately preceding the stated maturity date, into shares of the Company’s common stock at a conversion rate of 333.3333 shares per $1,000 principal amount of 2024 convertible notes, which is equal to a conversion price of approximately $3.00 per share.

If certain bankruptcy and insolvency-related events of default occur, the principal of, and accrued and unpaid interest on, all of the then outstanding 2024 convertible notes shall automatically become due and payable. If an event of default other than certain bankruptcy and insolvency-related events of defaults occurs and is continuing, the Trustee or the holders of at least 25% in aggregate principal amount of the then-outstanding 2024 convertible notes, by written notice to the Trustee, may declare the 2024 convertible notes due and payable at their principal amount plus any accrued and unpaid interest, and thereupon the Trustee may, at its discretion, proceed to protect and enforce the rights of the holders by the appropriate judicial proceedings. Notwithstanding the foregoing, the Indenture provides that, to the extent the Company elects, the sole remedy for an event of default relating to certain failures by the Company to comply with certain reporting covenants in the Indenture will, for the first 180 days after such event of default, consist exclusively of the right to receive additional interest on the 2024 convertible notes. The 2024 convertible notes also contain certain cross default provisions related to other debt obligations.

If the Company undergoes certain fundamental changes, except in certain circumstances, each holder of 2024 convertible notes will have the option to require the Company to repurchase all or any portion of that holder’s 2024 convertible notes. The fundamental change repurchase price will be 100% of the principal amount of the 2024 convertible notes to be repurchased plus accrued and unpaid interest, if any.

The Company may elect at its option to cause all or any portion of the 2024 convertible notes to be mandatorily converted in whole or in part at any time prior to the close of business on the business day immediately preceding the maturity date, if the last reported sale price of its common stock equals or exceeds 120% of the conversion price then in effect for at least 10 trading days in any 20 trading day period, ending within five business days prior to the date of the mandatory conversion notice.

Mann Group promissory notes — In August 2019, the Company entered into a privately-negotiated exchange agreement with The Mann Group LLC (the “Mann Group”), pursuant to which, among other things, the Company (i) repaid $3.0 million in cash to the Mann Group, (ii) issued 7,142,857 shares of the Company’s common stock to the Mann Group (at a conversion price of $1.12 per share), (iii) issued a $35.0 million note that is convertible into shares of the Company’s common stock at $2.50 per share (the “Mann Group convertible note”) and (iv) issued a non-convertible note to the Mann Group in an aggregate principal amount of $35.1 million (the “Mann Group non-convertible note” and, together with the Mann Group convertible note, the “Mann Group promissory notes”), all in exchange for the cancellation of the $71.5 million in principal and approximately $9.5 million in accrued interest paid-in-kind under the existing Mann Group loan arrangement.

The Mann Group promissory notes each accrue interest at the rate of 7.00% per year on the principal amount, payable quarterly in arrears on the first day of each calendar quarter beginning October 1, 2019.

The Mann Group convertible note will mature on November 3, 2024. The principal and any accrued and unpaid interest under the Mann Group convertible note may be converted, at the option of the Mann Group, at any time on or prior to the close of business on the business day immediately preceding the stated maturity date, into shares of the Company’s common stock at a conversion rate of 400 shares per $1,000 of principal and/or accrued and unpaid interest, which is equal to a conversion price of $2.50 per share. The conversion rate will be subject to adjustment under certain circumstances described in the Mann Group convertible note. Interest on the Mann Group convertible note will be payable in kind by adding the amount thereof to the principal amount; provided that with respect to interest accruing from and after January 1, 2021, the Company may, at its option, elect to pay any such interest on any interest payment date, if certain conditions are met, in shares of the Company’s common stock at a price per shall equal to the last reported sale price on the trading day immediately prior to the payment date.

The Mann Group non-convertible note will mature on the earlier of (i) November 3, 2024 or (ii) the 90th day after the repayment in full, and termination and discharge of all obligations (other than contingent indemnity obligations) under the MidCap Credit Facility. Interest on the Mann Group non-convertible note will be payable in kind by adding the amount thereof to the principal amount; provided that MannKind may, at its option, elect to pay any such interest on any interest payment date, if certain conditions are met, in shares of MannKind’s common stock at a price per shall equal to the last reported sale price on the trading day immediately prior to the interest payment date.

PPP Loan – On April 10, 2020, the Company received the proceeds from the PPP Loan from JPMorgan Chase Bank, N.A., as lender, in the amount of approximately $4.9 million pursuant to the PPP of the CARES Act. The PPP Loan matures on April 9, 2022 and bears interest at a rate of 0.98% per annum. The PPP Loan is evidenced by a promissory note dated April 9, 2020, which contains customary events of default relating to, among other things, payment defaults and breaches of representations and warranties. The PPP Loan may be prepaid by the Company at any time prior to maturity with no prepayment penalties. All or a portion of the PPP Loan may be forgiven by the U.S. Small Business Administration (“SBA”) upon application to the lender by the Company beginning 60 days after loan approval, but not later than ten months after the end of the Company’s covered period, and upon documentation of expenditures in accordance with the SBA requirements. Principal and interest payments can be deferred up to ten months after the end of the Company’s covered period unless the Company is notified earlier of its loan forgiveness status. In the event the SBA does not authorize loan forgiveness, the deferred principal and interest will be payable to the lender and the Company will then make equal monthly payments as required to fully amortize the remaining principal amount by April 9, 2022.

Under the CARES Act, loan forgiveness is available for the sum of documented payroll costs, covered rent payments, covered interest and covered utilities during the 24-week period (or eight-week period at the Company’s option) beginning on the date of loan approval. For purposes of the CARES Act, payroll costs exclude compensation of an individual employee in excess of $100,000, prorated annually. Not more than 40% of the forgiven amount may be for non-payroll costs. Forgiveness is reduced if full-time headcount declines, or if salaries and wages for employees with salaries of $100,000 or less annually are reduced by more than 25%. In the event the PPP Loan, or any portion thereof, is forgiven pursuant to the PPP, the amount forgiven is applied to outstanding principal. Any unforgiven portion of the PPP Loan will be payable in accordance with the terms of the promissory note as described above.

The Company used all proceeds from the PPP Loan to retain employees, maintain payroll and make lease, interest and utility payments.

Amortization of the premium and accretion of debt issuance costs related to all borrowings for the three and nine months ended September 30, 2020 and 2019 are as follows (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
	2020			2019			2020			2019
Accretion of debt discount	$	53		$	8		$	232		$	149
Amortization of debt issuance cost		(27	)		(34	)		(82	)		(84	)
Amortization of debt premium		—			(858	)		—			(1,049	)

Milestone Rights — As of September 30, 2020 and December 31, 2019, the remaining Milestone Rights liability balance was $7.3 million, which was based on initial fair value estimates calculated using the income approach and reduced by milestone achievement payments made. During the third quarter of 2019, the Company achieved the first Afrezza net sales milestone specified by the Milestone Rights. The Company currently estimates that it will reach the next milestone in the first quarter of 2021, at which point the Company will be required to make a $5.0 million payment in the following quarter. The carrying value of the Milestone Rights liability related to this $5.0 million payment is approximately $1.3 million, which represents the fair value related to this payment that was determined in 2013 (the most recent measurement date). Accordingly, approximately $1.3 million in value related to the next milestone payment was recorded in accrued expenses and other current liabilities and the remaining long-term portion of $5.9 million is included as Milestone Rights liability in the accompanying condensed consolidated balance sheets as of September 30, 2020.

The agreement with the Milestone Purchasers that provides for the Milestone Rights includes customary representations and warranties and covenants by the Company, including restrictions on transfers of intellectual property related to Afrezza. The Milestone Rights are subject to acceleration in the event the Company transfers its intellectual property related to Afrezza in violation of the terms of such agreement. The Company has initially recorded the Milestone Rights at their estimated fair value.