7. Borrowings

Borrowings consist of the following (in thousands):

	December 31,
	2017			2016
Facility Financing Obligation (2019 Notes and Tranche B Notes)
Principal amount	$	54,407		$	75,000
Unamortized debt issuance costs and debt discount		(1,662	)		(3,661	)
Net carrying amount	$	52,745		$	71,339
Senior Convertible Notes (2021 Notes)
Principal amount	$	23,690		$	27,690
Unamortized premium		721			426
Unaccreted debt issuance costs		—			(481	)
Net carrying amount	$	24,411		$	27,635
Note payable to principal stockholder - net carrying amount	$	79,666		$	49,521

Facility Financing Obligation (2019 Notes and Tranche B Notes) – As of December 31, 2017, there were $39.4 million principal amount of 2019 notes and $15.0 million principal amount of Tranche B notes outstanding. As of December 31, 2016, there were $55.0 million principal amount of 2019 notes and $20.0 million principal amount of Tranche B notes outstanding. The 2019 notes accrue interest at annual rate of 9.75% and the Tranche B notes accrue interest at an annual rate of 8.75%. Interest is paid quarterly in arrears on the last day of each March, June, September and December.

On April 18, 2017, the Company entered into an Exchange Agreement with Deerfield pursuant to which the Company agreed to, among other things, (i) repay $4.0 million principal amount under the Tranche B notes; (ii) exchange $1.0 million principal amount under the Tranche B notes for 869,565 shares of the Company’s common stock (the “Tranche B Exchange Shares”); and (iii) exchange $5.0 million principal amount under the 2019 notes for 4,347,826 shares of the Company’s common stock (together with the “Tranche B Exchange Shares,” the “April Exchange Shares”). The exchange price for the Exchange Shares was $1.15 per share.

The Company determined that, since the principal amount repaid and exchanged under the Tranche B notes and the principal amount exchanged under the 2019 notes represented the principal amount that would have otherwise become due and payable in May and July of 2017 under the Tranche B notes and 2019 notes, respectively, the extinguishment of the May and July 2017 payments was not considered to be a troubled debt restructuring. Accordingly, the Company accounted for the transaction by recording a loss on extinguishment of debt of $0.3 million at April 18, 2017 which was calculated as the difference between the reacquisition price and the net carrying value of the related debt. The reacquisition price was calculated using the $4.0 million cash repayment and the fair value of the April Exchange Shares on April 18, 2017. The fair value of the April Exchange Shares was determined to be $1.22 per share representing the closing trading price of the Company’s common stock on The NASDAQ Global Market on April 18, 2017.

On June 29, 2017, the Company entered into the Third Amendment with Deerfield, pursuant to which the Company agreed to, among other things, (i) exchange $5.0 million principal amount under the Company’s 2019 notes for 3,584,230 shares of the Company’s common stock (the “June Exchange Shares”) at an exchange price of $1.395 per share and (ii) amend the Facility Agreement with Deerfield, to (A) defer the payment of $10.0 million in principal amount of the 2019 notes from the original July 18, 2017 due date to August 31, 2017, which was further deferred to October 31, 2017 upon the Company’s delivery on August 31, 2017 and October 30, 2017 of a written certification to Deerfield that certain conditions had been met, including that no event of default under the Facility Agreement had occurred, Michael E. Castagna remains the Company’s Chief Executive Officer, the Company received the advance from The Mann Group (see Note 6 — Related-Party Arrangements), the Company had at least $10.0 million in cash and cash equivalents on hand, no material adverse effect on the Company had occurred, the engagement letter between the Company and Greenhill & Co., Inc. (“Greenhill”) remained in full force and effect and Greenhill had remained actively engaged in exploring capital structure and financial alternatives on behalf of the Company in accordance with such engagement letter (collectively, the “Extension Conditions”), and (B) amend the Company’s financial covenant under the Facility Agreement to provide that, if the Extension Conditions remain satisfied, the obligation under the Facility Agreement to maintain at least $25.0 million in cash and cash equivalents as of the end of each quarter, was be reduced to $10.0 million as of August 31, 2017, September 30, 2017, October 31, 2017 and December 31, 2017 if certain conditions were met. We met the conditions at each of these month-ends.

The Company determined that since the principal amount repaid and exchanged under the 2019 notes represented the principal amount that would have otherwise become due and payable under the 2019 notes, the $5.0 million prepayment was not considered to be a troubled debt restructuring. Accordingly, the Company accounted for the transaction by recording a loss on extinguishment of debt of $0.5 million on June 29, 2017 which was calculated as the difference between the reacquisition price and the net carrying value of the related debt. The net carrying value of the related debt includes the acceleration of the debt discount and issuance costs amounting to approximately $0.3 million as a result of the transaction. The reacquisition price was calculated using the fair value of the June Exchange Shares on June 29, 2017. The fair value of the Exchange Shares was determined to be $1.45 per share representing the closing trading price of the Company’s common stock on The NASDAQ Global Market on June 29, 2017.

On October 23, 2017, the Company and MannKind LLC entered into a Fourth Amendment to the Facility Agreement, pursuant to which the parties (i) deferred the payment of $10.0 million in principal amount (the “October Payment”) of the Facility Financing Obligation from October 31, 2017 to January 15, 2018 (further extended to January 19 ,2018 under the Fifth Amendment and May 6, 2018 under the Sixth Amendment to the Facility Agreement – See Note 20 - Subsequent Events), with the Company depositing an amount of cash equal to the October Payment into an escrow account until the October Payment has been satisfied in full (subject to early release to the extent that portions of the October Payment are satisfied through the exchange of principal for shares of the Company’s common stock), and (ii) amended and restated the Facility Financing Obligation and the Tranche B notes to provide that Deerfield may convert the principal amount under such notes from time to time into an aggregate of up to 4,000,000 shares of the Company’s common stock after the effective date of the Fourth Amendment. The conversion price will be the greater of (i) the average of the volume weighted average price per share of the Company’s common stock for the three trading day period immediately preceding the date of any election by Deerfield to convert principal amounts of such notes and (ii) $3.25 per share, subject to adjustment under certain circumstances. Any conversions of principal by Deerfield under such notes will be applied first to reduce the October Payment, and after the October Payment has been satisfied, to reduce other principal payments due under the 2019 notes or the Tranche B notes.

The Company determined that the Fourth Amendment did not include any concessions and that the addition of the conversion option was not substantive and therefore it was not considered to be a troubled debt restructuring. Accordingly, the Company accounted for the transaction as a modification. On November 6, 2017 Deerfield converted 1,720,846 shares under the conversion feature at a price of $3.25/share, redeeming $5,592,750 of principal.

As of December 31, 2017, there was $39.4 million principal amount of 2019 notes and $15.0 million principal amount of Tranche B notes outstanding. The 2019 notes accrue interest at an annual rate of 9.75% and the Tranche B notes accrue interest at an annual rate of 8.75%. Interest is paid quarterly in arrears on the last day of each March, June, September and December. The Facility Financing Obligation principal repayment schedule is comprised of payments which began on July 1, 2016 and end on December 9, 2019. As of December 31, 2017, future payments for the years ending December 31, 2018, and 2019 are $24.4 million and $30.0 million, respectively.

In connection with the Facility Agreement, on July 1, 2013, the Company entered into a Milestone Rights Purchase Agreement (the “Milestone Agreement”) with Deerfield and Horizon Santé FLML SÁRL (collectively, the “Milestone Purchasers”), which requires the Company to make contingent payments to the Milestone Purchasers, totaling up to $90.0 million, upon the Company achieving specified commercialization milestones (the “Milestone Rights”). The Milestone Rights were initially recorded as a short-term liability equal to $3.2 million included in accrued expenses and other current liabilities and a long-term liability equal to $13.1 million included in other liabilities in the accompanying consolidated balance sheets. During the first quarter of 2015, a milestone triggering event was achieved following the Afrezza launch on February 3, 2015, which resulted in a $5.8 million incremental charge to interest expense due to the increase in carrying value of the liability to the $10.0 million milestone payment made in February 2015.

As of December 31, 2017 and 2016, the remaining milestone rights liability balance was $8.9 million. The Company currently estimates that it will reach the next milestone in the third quarter of 2018, at which point the Company will be required to make a $5 million payment. The carrying value of the milestone rights liability related to this $5 million payment is $1.6 million, which represents the fair value related to this payment that was determined in 2013 (the most recent measurement date). Accordingly, $1.6 million in value related to the next milestone payment was recorded in accrued expenses and other current liabilities as of December 31, 2017. Furthermore, $7.2 million and $8.9 million was recorded in milestone rights liability and other liabilities, which is non-current, in the accompanying consolidated balance sheets as of December 31, 2017 and 2016, respectively.

Accretion of debt issuance cost and debt discount in connection with the Facility Agreement does not include the acceleration of the debt discount and issuance costs related to the transactions disclosed above as the amounts were included in the loss on extinguishment of debt in the consolidated statement of operations. Accretion of debt issuance cost and debt discount during the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	December 31,
	2017		2016		2015
Accretion expense - debt issuance cost	$	31	$	35		35
Accretion expense - debt discount	$	1,700	$	1,722		1,553

The Facility Agreement includes customary representations, warranties and covenants, including a restriction on the incurrence of additional indebtedness. As discussed in Note 1 – Description of Business, the Company will need to raise additional capital to support its current operating plans. Due to the uncertainties related to maintaining sufficient resources to comply with the aforementioned covenant, the Facility Financing Obligation has been classified as a current liability in the accompanying consolidated balance sheets as of December 31, 2017 and 2016. In the event of non-compliance, Deerfield may declare all or any portion of the Facility Financing Obligation to be immediately due and payable.

Milestone Rights — The Milestone Agreement 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 the Milestone Agreement. The Company initially recorded the Milestone Rights at their estimated fair value.

Security Agreement — In connection with the Facility Agreement and Milestone Agreement, the Company and its subsidiary, MannKind LLC, entered into a Guaranty and Security Agreement (the “Security Agreement”) with Deerfield and Horizon Santé FLML SÁRL (collectively, the “Purchasers”), pursuant to which the Company and MannKind LLC each granted the Purchasers a security interest in substantially all of their respective assets, including respective intellectual property, accounts receivables, equipment, general intangibles, inventory and investment property, and all of the proceeds and products of the foregoing. The Security Agreement includes customary covenants by the Company and MannKind LLC, remedies of the Purchasers and representations and warranties by the Company and MannKind LLC. The security interests granted by the Company and MannKind LLC will terminate upon repayment of the Facility Financing Obligation, if applicable, in full.

Embedded Derivatives — The Company identified and evaluated a number of embedded features in the notes issued under the Facility Agreement to determine if they represented embedded derivatives that are required to be separated from the notes and accounted for as freestanding instruments. The Company analyzed the Tranche B notes and identified embedded derivatives which required separate accounting. All of the embedded derivatives were determined to have a de minimis value as of December 31, 2017 and 2016.

Senior Convertible Notes Due 2021 — On October 23, 2017, the Company entered into exchange agreements with the holders of the Company’s 5.75% Senior Convertible Notes due 2018 (the “2018 notes”), pursuant to which the Company agreed to exchange all of the outstanding 2018 notes in the aggregate principal amount of $27,690,000 for (i) 23,690,000 aggregate principal amount of Senior Convertible notes due 2021 (the “2021 notes”) and (ii) an aggregate of 973,236 shares of its common stock. In addition, the conversion rate was adjusted from $34 per share to $5.15 per share. The 2021 notes were issued at the closing of the exchange on October 23, 2017. The Company analyzed this exchange and concluded that the exchange represents an extinguishment of the 2018 notes and recorded a $0.8 loss on extinguishment of debt. In addition unamortized debt issuance costs of $0.3 million and unamortized debt premium of $0.2 million were also written-off during the last quarter of fiscal year 2017.

The 2021 notes are the Company’s general, unsecured, senior obligations, except that they are subordinated in right of payment to the Facility Financing Obligation. The 2021 notes rank equally in right of payment with the Company’s other unsecured senior debt. The 2021 notes bear interest at the rate of 5.75% per year on the principal amount, payable semiannually in arrears in cash or, at the option of the Company if certain conditions are met, in shares of the Company’s common stock (the “Interest Shares”), on February 15 and August 15 of each year, beginning February 15, 2018, with interest accruing from August 15, 2017. The aggregate number of Interest Shares that the Company may issue may not exceed 13,648,300, unless the Company receives stockholder approval to issue Interest Shares in excess of such number in accordance with the listing standards of the NASDAQ Global Market. Accrued interest related to these notes is recorded in accrued expenses and other current liabilities on the accompanying consolidated balance sheets.

The 2021 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 an initial conversion rate of 194.1748 shares per $1,000 principal amount of 2021 notes, which is equal to the initial conversion price of approximately $5.15 per share. The conversion rate is subject to adjustment under certain circumstances described in an indenture governing the 2021 notes.

If the Company undergoes certain fundamental changes, except in certain circumstances, each holder of 2021 notes will have the option to require the Company to repurchase all or any portion of that holder’s 2021 notes. The fundamental change repurchase price will be 100% of the principal amount of the 2021 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 2021 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 exceeds 120% of the conversion price then in effect for at least 10 trading days in any 20 consecutive trading day period, ending within five business days prior to the date of the mandatory conversion notice. The redemption price is equal the sum of 100% of the principal amount of the 2021 notes to be redeemed, plus accrued and unpaid interest. Under the terms of the indenture, the conversion option can be net-share settled and the maximum number of shares that could be required to be delivered under the indenture is fixed and less than the number of authorized and unissued shares less the maximum number of shares that could be required to be delivered during the term of the 2021 notes under existing commitments. Applying the Company’s sequencing policy, the Company performed an analysis at the time of the offering of the 2021 notes and each reporting date since and has concluded that the number of available authorized shares at the time of the offering and each reporting date since was sufficient to deliver the number of shares that could be required to be delivered during the term of the 2021 notes under existing commitments.

The 2021 notes provide that upon an acceleration of certain indebtedness, including the 2019 notes and the Tranche B notes issued to Deerfield pursuant to the Facility Agreement, the holders may elect to accelerate the Company’s repayment obligations under the notes if such acceleration is not cured, waived, rescinded or annulled.

As a result of the exchange of the 2021 notes during the last quarter of 2017, the Company recorded approximately $0.8 million in debt premium, which is recorded with the 2021 notes, in the accompanying consolidated balance sheets. The premium is being accreted to interest expense using the effective interest method over the term of the 2021 notes.

Accretion of debt issuance costs in connection with the 2018 notes during the years ended December 31, 2017 and 2016 was $0.2 million and $0.3 million, respectively. Amortization of the 2018 notes premium during the years ended December 31, 2017 and 2016 was $0.2 million and $0.2 million, respectively. Amortization of the 2021 notes premium during the year ended December 31, 2017 was $0.03 million.

Refer to Note 6 — Related-Party Arrangements for information regarding the Note payable to principal stockholder.