Note 8—OMIDRIA Royalty Obligation 

On September 30, 2022, we sold to DRI a portion of our future OMIDRIA royalty receipts for a purchase price of $125.0 million and recorded an OMIDRIA royalty obligation for the same amount. On February 1, 2024, DRI purchased our remaining U.S. OMIDRIA royalty receipts through December 31, 2031 for $115.5 million in cash under the Amendment. The Amendment eliminated the previously existing annual caps on royalty payments after January 1, 2024, and provides that DRI receives all royalties on U.S. net sales of OMIDRIA payable between January 1, 2024 and December 31, 2031. We accounted for the Amendment as a modification of our existing debt from DRI. The OMIDRIA royalty obligation is valued based on our estimates of future OMIDRIA royalties and is amortized through December 31, 2031. All royalties earned on OMIDRIA sales within the U.S. through December 31, 2031 are remitted by Rayner to an escrow account established by Omeros, from which payments are made to DRI. DRI has no recourse to our assets other than in its interest in OMIDRIA royalties.

We currently retain the right to receive all royalties payable by Rayner on any ex-U.S. net sales. After December 31, 2031, we retain the right to receive all global royalties payable by Rayner on net sales of OMIDRIA. To date, international royalties have not been significant. DRI has no recourse to our assets other than its interest in OMIDRIA royalties.

We are entitled to receive a separate milestone payment ranging between $8.0 million and $27.5 million if U.S. net sales of OMIDRIA reach applicable thresholds ranging between a total of $181.0 million and $185.0 million in the aggregate for any period of four consecutive quarters prior to January 1, 2028, although we do not expect to receive this milestone based on current U.S. net sales of OMIDRIA.

The changes in the OMIDRIA royalty obligation during the three months ended March 31, 2026 are as follows (in thousands):

The OMIDRIA royalty obligation is classified as a Level 3 liability as its valuation requires substantial judgment and estimation of factors that are not currently observable in the market. The fair value of the OMIDRIA royalty obligation is determined by calculating the net present value of our estimated future OMIDRIA cash flows using the interest rate at inception of our royalty purchase agreement with DRI, adjusted for the change in the prime rate through the measurement date. As of March 31, 2026 and December 31, 2025, the approximate fair value of our obligation was $160.7 million and $166.7 million, respectively.

Interest expense is comprised of the effective interest component of any cash payment remitted through an administrative agent to DRI, based on an implied effective interest rate of 9.92%, and any remeasurement adjustments taken during the period. Remeasurements are non-cash adjustments to the OMIDRIA royalty obligation reflecting changes in forecasted cash flows stemming from the OMIDRIA contract royalty asset. For the three months ended March 31, 2026 and 2025, interest expense is as follows:

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As of March 31, 2026, the expected scheduled principal and interest payments are as follows: