Our borrowing instruments are recorded at their carrying values in the balance sheets, which may differ from their respective fair values. The fair values of outstanding borrowings, which are classified as Level 2, approximate their carrying values as of December 31, 2021 and 2020, based on interest rates currently available for similar borrowings and were (in thousands):


	As of December 31,
	2021				2020
	Carrying Value		Fair Value		Carrying Value		Fair Value
Borrowings	$	10,012	$	10,012	$	27,766	$	27,766

The financial liabilities that are measured and recorded at estimated fair value on a recurring basis consist of our contingent consideration associated with our acquisition of Indi, and prior to the completion of our IPO in October 2020, the warrant liability, put option liability and contingent value rights granted to certain holders of our convertible preferred stock and debt instruments, which were accounted for as liabilities and remeasured through our statements of operations. The table below presents the reported fair values of contingent consideration, which is classified as Level 3 in the fair value hierarchy, as of the dates indicated (in thousands):


	As of December 31,
Description	2021		2020
Current portion of contingent consideration	$	17,764	$	—
Contingent consideration		16,028		29,932
Total contingent consideration	$	33,792	$	29,932

The following table presents the changes in contingent consideration for the year ended December 31, 2021 (in thousands):


	Year Ended
Level 3 Rollforward	December 31, 2021
Beginning balances - January 1, 2021	$	29,932
Changes in fair value		1,622
Interest expense		2,238
Ending balances - December 31, 2021	$	33,792

The following table presents the changes in these financial liabilities for the year ended December 31, 2020 (in thousands):


	For the Year Ended December 31, 2020
Level 3 Rollforward	Contingent Consideration		Put Option Liability			Warrant Liability			Contingent Value Rights
Beginning balances - January 1, 2020	$	29,114	$	3,261		$	372		$	60
Additions		—		3,389			—			—
Changes in fair value		818		—			1,252			(60	)
Reclassified to additional paid-in capital		—		(6,650	)		(1,624	)		—
Ending balances - December 31, 2020	$	29,932	$	—		$	—		$	—

In connection with the acquisition of Indi in 2018, the Company recorded contingent consideration for amounts contingently payable to Indi's selling shareholders pursuant to the terms of the asset purchase agreement (Indi APA). The contingent consideration arrangement requires additional consideration to be paid by the Company to Indi upon attainment of a three-consecutive month gross margin target of $2.0 million within the seven-year period after the acquisition date. Under the terms of the agreement, when the gross margin target was met the Company was required to issue 2,520,108 shares of common stock. For the six months following the achievement of the gross margin target, Indi had the option to require the Company to redeem these common shares for $37.0 million in cash over eight equal quarterly installments. If Indi elected to not exercise its option, the Company had 12 months to repurchase the common stock in two equal and consecutive quarterly cash installments totaling $37.0 million.

The Company met the gross margin target of $2.0 million for three consecutive months during the three months ended June 30, 2021. The Company entered into an amendment to the original agreement in August 2021 in which all parties agreed to forgo the issuance of common stock and agreed that the Company will in lieu thereof make six quarterly installments of approximately $4.6 million beginning in January 2022 and a final payment of approximately $9.3 million in July 2023 for a total of $37.0 million. The aggregate amount of payments owed by the Company under this amendment is the same as if Indi had exercised the put right or the Company had exercised the call right provided for in the original agreement. Our ability to make these payments are subject to consent from our lender under the 2021 Term Loan and related amendments (see Note 8 - Debt). We obtained consent and subsequently made the first milestone payment of $4.6 million in January 2022 and we are in discussions with our lender to obtain consents for future payments.

The significant unobservable inputs used in the measurement of fair value include the probability of successful achievement of the specified product gross margin targets, the period in which the targets were expected to be achieved, and discount rates which ranged from 11% to 13.5%. As a result of the achievement of the gross margin target, the only significant unobservable input used in the measurement of fair value includes the discount rate since all other inputs became fixed and determinable. Significant increases or decreases in the discount rate would result in a significantly higher or lower fair value measurement.

Contingent consideration expected to be paid in the next twelve months is recorded in the balance sheets as ‘Current portion of contingent consideration’ while the remaining amount to be paid is recorded as ‘Contingent consideration’ within non-current liabilities. The net change to contingent consideration through the date the gross margin target was met is recorded as operating expenses in the statements of operations. Subsequent changes to the contingent consideration following the achievement of the gross margin target are recorded as ‘Interest expense’ in the statements of operations resulting from the passage of time and fixed payment schedule. The net change to contingent consideration recorded as operating expenses during the years ended December 31, 2021 and 2020 was a loss of $1.6 million and $0.8 million, respectively. The amount recorded as ‘Interest expense’ during the year ended December 31, 2021 was $2.2 million.

The put option liability was valued based on the calculated returns as a result of the various discounts included in the Company’s convertible notes payable and the related probability assessments of the various settlement scenarios. During 2020, the Company recognized an addition to the put option liability of $3.4 million in connection with a favorable conversion rate granted to holders of issued convertible debt. The put option liability was settled upon the closing of the Company’s IPO in October 2020 and reclassified to additional paid-in capital.

In connection with entering into the 2018 Notes, the Company issued to the lender a warrant to purchase 613,333 shares of Series G convertible preferred stock, at an exercise price of $0.75 per share, subject to adjustment upon specified dilutive issuances. The warrant was immediately exercisable upon issuance and expires on February 23, 2028. The estimated fair value of the warrant on the issuance date of $0.3 million was recorded as a debt discount and as a preferred stock warrant liability. Through the effective date of the Company’s IPO, the Series G warrants were remeasured to an estimate of fair value using a Black Scholes pricing model. As a result of the Company’s IPO, the preferred stock warrants were automatically converted to warrants to purchase 103,326 shares of common stock with a weighted average exercise price of $4.46 and were also transferred to additional paid-in capital. During 2020, the Company recorded an increase in the value of the warrant liability of $1.3 million.

In addition to the shares of Series F Preferred Stock that were issued in January 2016, investors who purchased more than their pro‑rata amount in the financing described above received a calculated number of contingent value rights (CVRs). In connection with the Series F financing, the Company issued 3,999 CVRs originally valued at $0.5 million. One CVR represents 0.00375% of the Company’s interest in the drug ficlatuzumab. The initial estimated value of the CVRs were recorded as a liability and as a reduction to the Series F proceeds. Upon receipt by the Company or a milestone, royalty, or any other type of payment from the Company’s ownership rights in the drug, the Company was required to make a cash payment to the CVR holders equal to 15% of net proceeds, as defined. In September 2020, the Company exercised its opt-out right with AVEO Oncology (AVEO) for the payment of 50% of development and regulatory costs for ficlatuzumab. As a result, the CVRs were settled effective December 2, 2020. See Note 15 – Commitments and Contingencies for a discussion of the Co-Development Agreement with AVEO.

Our non-financial assets, which primarily consist of property and equipment, goodwill, and other intangible assets, are not required to be carried at fair value on a recurring basis and are reported at carrying value. There were no changes to the valuation methods during the periods presented.