OMEROS CORP

Note 1—Organization and Basis of Presentation

General

Omeros Corporation (“Omeros,” the “Company” or “we”) is an innovative, commercial-stage biotechnology company that discovers and develops first-in-class protein and small-molecule therapeutics for large-market and orphan indications, with particular emphasis on complement-mediated diseases, cancers, and addictive or compulsive disorders.

Our clinical-stage development programs include: narsoplimab, our antibody targeting mannan-binding lectin-associated serine protease 2 (“MASP-2”), the effector enzyme of the lectin pathway of complement; OMS1029, our long-acting antibody targeting MASP-2; and OMS527, our phosphodiesterase 7 (“PDE7”) inhibitor program. During 2025, we entered into an Asset Purchase and License Agreement (“APLA”) with Novo Nordisk Health Care AG (“Novo Nordisk”) for exclusive global rights in all indications to develop and commercialize zaltenibart, also known as OMS906, our lead antibody targeting mannan-binding lectin-associated serine protease-3 (“MASP-3”), the key activator of the alternative pathway of complement. We retain rights to our MASP-3 small-molecule program, including the ability to develop and commercialize small-molecule MASP-3 inhibitors across a range of therapeutic areas, including, but not limited to, ophthalmology, neurology, gastrointestinal disorders, dermatology, musculoskeletal diseases, and oncology. We also retain rights to develop our “grandfathered” MASP-3 antibodies, with temporal and indication restrictions on commercialization, and for use in advancing our small-molecule therapeutics.

FDA Approval of YARTEMLEA®

On December 23, 2025, FDA approved YARTEMLEA® (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (“TA-TMA”). TA-TMA is a severe and often-fatal complication of hematopoietic stem cell transplantation in adults and children, driven by systemic endothelial injury triggered by conditioning regimens, immunosuppressants, infection, graft-versus-host disease, and other transplant-related factors. Activation of the lectin pathway of complement plays a central role in disease pathogenesis. YARTEMLEA selectively inhibits MASP-2, blocking pathway activation while preserving classical and alternative complement pathway functions important for host defense. In TA-TMA, MASP-2 inhibition prevents lectin pathway-mediated cellular injury, including endothelial damage in small blood vessels, and thrombus formation.

YARTEMLEA is the first and only approved inhibitor of the lectin pathway of complement. YARTEMLEA is approved for the treatment of TA-TMA in adults and in children ages two years and older.

Commercial distribution and sales of YARTEMLEA commenced in January 2026.

A marketing authorization application (“MAA”) for YARTEMLEA in TA-TMA has been submitted to the European Medicines Agency (“EMA”) and is being reviewed under EMA’s centralized review procedure, which allows review of a single marketing authorization application. If the MAA is approved, it would authorize the product to be marketed in all European Union (“EU”) member states and European Economic Area countries. The European Commission has granted narsoplimab designation as an orphan medicinal product for treatment in hematopoietic stem cell transplantation. For commercialization of YARTEMLEA outside the U.S., we are evaluating potential partnerships, including broad ex-U.S. and regional collaborations.

Sale of Zaltenibart

On November 25, 2025, we completed a transaction (the “Transaction”) pursuant to the APLA between Omeros and Novo Nordisk, dated October 10, 2025, in which Novo Nordisk received exclusive global rights in all indications to develop and commercialize our lead investigational MASP-3 inhibitor, zaltenibart (formerly OMS906), and certain related compounds and products. Zaltenibart is a first-in-class, late-stage clinical humanized monoclonal antibody targeting MASP-3, the most upstream and key activator of the alternative pathway of the complement system. Zaltenibart has shown multiple potential advantages over other alternative pathway inhibitors in development and on the market.

At the closing of the Transaction, we received an upfront cash payment of $240.0 million. In addition, we are eligible to receive (i) up to $510.0 million in one-time milestone payments upon the first achievement by Novo Nordisk or its affiliates or sublicensees of each of the development and approval milestone events as set forth in the APLA and (ii) up to $1.3 billion in one-time milestone payments upon the first achievement by Novo Nordisk or its affiliates or sublicensees of certain sales-based milestone events as set forth in the APLA. We are also eligible under the APLA to receive tiered royalties on annual net sales of products at percentage rates ranging from high single digit to high teens, subject to reduction in certain circumstances, as set forth in the APLA. In total, we are eligible to receive up to an additional $1.8 billion in potential development and commercial milestones, plus tiered royalties on net sales.

Pursuant to the APLA, we sold and transferred, and Novo Nordisk purchased, zaltenibart and certain related assets, and the parties agreed to grant and receive certain intellectual property licenses to facilitate the continued development and commercialization activities of both companies. We retain rights to our MASP-3 small-molecule program unrelated to zaltenibart, including the ability to develop and commercialize small-molecule MASP-3 inhibitors, across a range of therapeutic areas, including, but not limited to, ophthalmology, neurology, gastrointestinal disorders, dermatology, musculoskeletal diseases and oncology. We also retain rights to our “grandfathered” MASP-3 antibodies, with temporal and indication restrictions on commercialization and for use in advancing our small-molecule therapeutics.

In accordance with the APLA, at the closing of the Transaction, Omeros and Novo Nordisk entered into a transition services agreement (the “Transition Services Agreement”) pursuant to which we are providing certain transition services to Novo Nordisk to facilitate the transfer of the acquired assets and liabilities under the APLA and to provide for the continued operation of relevant studies and program activities during the applicable term. Subject to certain exceptions and limitations, Novo Nordisk reimburses us for costs and expenses we incur under the Transition Services Agreement, including third-party costs and expenses, costs associated with delivery of transition services by Omeros personnel on an hourly basis at rates specified in the Transition Services Agreement, and for our inventories of zaltenibart drug substance and product.

Other Development Programs

Our lectin pathway program also includes OMS1029, our long-acting antibody targeting MASP-2. We have completed Phase 1 clinical trials evaluating both single-ascending and multiple ascending doses of OMS1029. Results of these studies support once-quarterly dosing administered either intravenously or subcutaneously. OMS1029 has been well tolerated to date with no safety concerns identified. We are working to finalize selection of an indication and initiate Phase 2 clinical development of OMS1029. In addition, we have selected a development candidate for our MASP-2 small molecule program, which is advancing to Investigational New Drug (“IND”)-enabling studies targeting once-daily oral administration.

Our PDE7 inhibitor program, which we refer to as OMS527, comprises multiple PDE7 inhibitor compounds and is based on our discoveries of previously unknown links between PDE7 and any addiction or compulsive disorder, and between PDE7 and any movement disorder. In April 2023, we were awarded a grant from the National Institute on Drug Abuse (“NIDA”), to develop an orally administered PDE7 inhibitor compound for the treatment of cocaine use disorder. NIDA awarded the grant to us for a total of $6.24 million over three years, of which we have claimed and received $2.3 million of funding to date. FDA subsequently requested additional nonclinical information prior to initiating the clinical in-patient study. Following a meeting with FDA to discuss that request, we are working with FDA to streamline the path to initiate the in-patient clinical trial, which is targeted for initiation by year-end 2026.

We also have various programs in preclinical research and development. We continue to progress preclinical studies within our novel oncology program, which is focused on developing novel, proprietary large molecule therapeutics designed to selectively target and kill dividing cancer cells. We have completed selection of a drug development candidate, and IND-enabling studies are underway for this program, which we refer to as OncotoX-AML. Acute myeloid leukemia (“AML”), an aggressive and highly fatal bone marrow and blood cancer, is the lead indication for development.

We are also advancing our targeted complement activating therapy (“T-CAT”) platform: a new class of recombinant antibodies intended for broad action against pathogens, including bacteria, fungi, viruses, and parasites. T-CAT is designed to harness complement activation to kill pathogens directly, which represents a novel approach to infectious disease treatment. Our initial focus is on T-CAT’s potential against multidrug-resistant organisms.

Basis of Presentation

Our condensed consolidated financial statements include the financial position and results of operations of Omeros and our wholly owned subsidiaries. All inter-company transactions have been eliminated. The accompanying condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments and non-recurring adjustments, considered necessary for the fair presentation of such information. Our financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”).

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant items subject to such estimates include revenue recognition and the valuations of the OMIDRIA contract royalty asset, the OMIDRIA royalty obligation, and the embedded derivatives associated with our debt. We base our estimates on historical experience and on various other factors that we believe are reasonable under the circumstances; however, actual results could differ from these estimates.

Note 2—Significant Accounting Policies

Segment Reporting

We operate inone business segment focusing on the research, discovery, development and commercialization of small-molecule and protein therapeutics targeting immunologic diseases, including complement-mediated diseases and cancers related to dysfunction of the immune system, as well as addictive and compulsive disorders. The Company defines its operating segment based on internally reported financial information that is regularly used by the Chief Operating Decision Maker (“CODM”) to analyze performance, make decisions and allocate resources. The Company’s CODM is our Chief Executive Officer. For the three months ended March 31, 2026, the Company has identifiedone operating and reporting segment. The CODM reviews net income (loss) and expenses reported on the condensed consolidated statement of operations and comprehensive income (loss). The measurement of segment assets is reported on the condensed consolidated balance sheet as total consolidated assets. All long-lived assets are held in the U.S. Our segment net income (loss) aligns with our condensed consolidated statement of operations and comprehensive income (loss).

Revenue Recognition

When we enter into a customer contract, we perform the following five steps: (i) identify the contract with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation.

Product Sales, Net

We generally recognize revenue from product sales when the product is delivered to our wholesalers and title to the product is transferred, upon which we have satisfied our performance obligations. Fulfillment activities by the wholesalers are not considered to be a separate performance obligation. Product revenue is recorded net of variable consideration, including wholesaler distribution fees, chargebacks, returns and discounts. We estimate variable consideration using the expected value approach. This estimate is based on several factors, including: historical return rates, expiration date by product and estimated levels of inventory in the wholesale channel. Since there is often a timing lag between the product sale and the settlement of accruals relating to these programs, our net product revenue may incorporate revisions of accruals for several periods. We include such estimates in the transaction price only to the extent that it is probable that a significant reversal of revenue will not occur when the uncertainty associated with the variable consideration is subsequently resolved.

Given the limited commercialization history of YARTEMLEA, our estimates of variable consideration require judgment and are subject to change as additional data becomes available. We recognize adjustments to net product revenue in the period in which changes in estimates become known.

Chargebacks

Chargebacks represent discounts provided to eligible covered entities under government programs, including the 340B Drug Pricing Program (“340B”) and the Medicaid Drug Rebate Program (“Medicaid”). In addition, we are subject to pricing obligations under our Federal Supply Schedule agreement with the U.S. government (the “FSS Agreement”), which establishes maximum prices for sales to certain federal agencies and may give rise to additional discounts and rebates. Chargebacks are recorded as a reduction of gross product revenue at the time of sale. Reserves for chargebacks are generally recorded as reductions of accounts receivable, while reserves for Medicaid rebates and patient co-pay assistance, if applicable, are recorded as accrued liabilities.

Chargeback estimates are based on statutory pricing requirements applicable to the 340B program and expected utilization by covered entities. Given the limited commercial history of our recently launched product, these estimates require significant judgment, including assumptions related to future utilization patterns and channel inventory. Estimates are reassessed at each reporting period and adjusted as necessary based on actual experience, changes in 340B utilization, and other relevant factors.

In addition to 340B chargebacks and Medicaid rebates, we maintain programs that may result in additional variable consideration, including a patient co-pay assistance program. There was no activity under the Medicaid and co-pay assistance program during the three months ended March 31, 2026, and, accordingly, no material related reductions to gross product revenue were recorded. We will continue to evaluate these programs as utilization evolves and will recognize the related reductions to revenue in the period in which they occur.

Distribution Fees and Return Allowances

We pay distribution fees to wholesalers for services they perform on our behalf. These fees are calculated based on the wholesalers’ average acquisition cost of purchases of YARTEMLEA, exclusive of any chargebacks. We estimate these amounts at the time of sale to the wholesaler and record them as a reduction in product sales in the same period the related revenue is recognized.

We allow for the return of product up to 12 months past its expiration date or for product that is damaged. In estimating product returns, we take into consideration our return experience to date, the remaining shelf-life of product we have previously sold, inventory in the wholesale channel, and our expectation that product is typically not held by health care providers based on the frequency of their reorders. There wereno product returns in the three months ended March 31, 2026. Due to the ordering patterns associated with transplant centers and the extended shelf life of YARTEMLEA, returns are expected to be limited; however, our estimates may change as commercial experience matures.

Cost of Product Sales

Cost of product sales includes third-party manufacturing, royalties based on net product sales, and other costs directly related to the production and distribution of YARTEMLEA. We expensed as research and development expense all costs associated with the manufacture of YARTEMLEA produced prior to FDA approval. As a result, the cost basis of inventory available for sale at the time of commercialization was minimal, and cost of product sales is correspondingly low during the initial period following launch. Following FDA approval, we capitalize direct manufacturing costs as inventory and recognize these amounts in cost of product sales when the related inventory is sold. Accordingly, cost of product sales and gross margin during the initial periods following commercialization may not be indicative of future periods as we begin capitalizing and expensing post‑approval manufacturing costs.

Research and Development

Research and development expenses are comprised primarily of contracted research and development activities, clinical trial study and manufacturing costs prior to approval; consulting services; contract milestones; materials and supplies; costs for personnel, including salaries, benefits, and stock-based compensation; depreciation; an allocation of our occupancy costs; and other expenses incurred to sustain our overall research and development programs. Advance payments for goods or services that will be used for future research and development activities are deferred and then recognized as an expense as the related goods are delivered or the services are performed. All other research and development costs are expensed as incurred.

Selling, General and Administrative

Selling, general and administrative expenses are comprised primarily of marketing expenses; professional and legal services; patent costs; and salaries, benefits, and stock-based compensation costs for marketing and other personnel not directly engaged in research and development. Additionally, selling, general and administrative expenses include depreciation, an allocation of our occupancy costs, and other general corporate expenses. Advertising costs are expensed as incurred.

Stock-Based Compensation

Stock-based compensation expense is recognized for all share-based payments, including grants of stock option awards and restricted stock units based on estimated fair values. The fair value of our stock is calculated using the Black-Scholes option-pricing model, which requires assumptions around volatility, forfeiture rates, risk-free interest rate and expected term. Compensation expense is recognized over the requisite service periods, which is generally the vesting period, using the straight-line method. Forfeiture expense is estimated at the time of grant and revised in subsequent periods if actual forfeitures differ from those estimates.

Income Taxes

Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their tax basis. Deferred tax assets and liabilities are measured using enacted tax rates applied to taxable income in the years in which those temporary differences are expected to be recovered or settled. We recognize the effect of income tax positions only if those positions are more likely than not to be sustained upon an examination by the relevant taxing authority. A valuation allowance is established when it is more likely than not that the deferred tax assets will not be realized.

Asset Sale Transactions

The Company evaluates transactions involving the sale of our compounds, products or drug programs to determine whether such arrangements represent a sale of a business or a sale of a nonfinancial asset. Transactions that do not meet the definition of a business are accounted for as the sale of a nonfinancial asset under Accounting Standards Codification (“ASC”) 610‑20,Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets.

Upon transfer of control of the compound, product or drug program asset to a counterparty, the Company recognizes consideration received. Any excess of consideration over the carrying value of the asset sold is recognized as a gain in the condensed consolidated statements of operations.

Potential Milestone Income

The APLA with Novo Nordisk includes variable consideration in the form of milestone payments that are contingent upon the achievement of specified development, regulatory or commercialization events. The Company applies the variable consideration and constraint guidance in ASC 606,Revenue from Contracts with Customers, by analogy. At contract inception and throughout the term of the arrangement, the Company assesses whether the achievement of each milestone is probable and estimates variable consideration using the most likely amount method. Contingent milestone payments are excluded from the transaction price until the related milestone is achieved and it is probable that a significant reversal of cumulative revenue recognized will not occur.

Amounts are included in the transaction price only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company re-evaluates the transaction price at each reporting period, including the estimated variable consideration and the application of the constraint, to reflect changes in circumstances. Factors considered in these evaluations include the clinical or technical complexity of the milestone, the stage of development, and the risk of regulatory approval. Because of the risk that products in development will not receive regulatory approval, we generally do not recognize any contingent payments that would be due to us until regulatory approval.

Discontinued Operations

We review the presentation of planned or completed business dispositions in the condensed consolidated financial statements based on the available information and events that have occurred. The review consists of evaluating whether the business meets the definition of a component for which the operations and cash flows are clearly distinguishable from the other components of the business and, if so, whether it is anticipated that after the disposal the cash flows of the component would be eliminated from continuing operations and whether the disposition represents a strategic shift that has a major effect on operations and financial results. Planned or completed business dispositions are presented as discontinued operations when all the criteria described above are met.

We determined that the zaltenibart Transaction with Novo Nordisk did not meet the above criteria. As such, we recorded the gain on sale of zaltenibart in Other Income in our condensed consolidated statement of operations and comprehensive loss for the year ended December 31, 2025.

On December 23, 2021, we closed on an Asset Purchase Agreement (the “Asset Purchase Agreement”) with Rayner Surgical Inc. (“Rayner”) for the sale of our commercial product OMIDRIA, which we record as an OMIDRIA contract asset on our condensed consolidated balance sheet. As a result of the divestiture, the results of OMIDRIA activities are classified as discontinued operations in our condensed consolidated statement of operations and comprehensive income (loss) and excluded from continuing operations for all periods presented. We have rights to receive future royalties from Rayner on OMIDRIA net sales at royalty rates that vary based on geography and certain regulatory contingencies. Therefore, future OMIDRIA royalties are treated as variable consideration. The sale of OMIDRIA qualified as an asset sale under GAAP. To measure the OMIDRIA contract royalty asset, we use the expected value approach, which is the sum of the discounted probability-weighted royalty payments we would receive using a range of potential outcomes, to the extent that it is probable that a significant reversal in the amount of cumulative income recognized will not occur.

All U.S. royalties received from Rayner through December 31, 2031 are remitted by Rayner to an escrow account established by Omeros, from which payments are made to DRI Healthcare Acquisition LP (“DRI”) and are entirely pass-through in nature to the Company. These payments comprise interest expense, with the remainder treated as a reduction of the OMIDRIA royalty obligation. The amount recorded in discontinued operations in future periods will reflect interest earned on the outstanding OMIDRIA contract royalty asset at 11.0% and any amounts we receive that are different from the expected royalties. The OMIDRIA contract royalty asset is re-measured quarterly using the expected value approach, which incorporates actual results and future expectations. (For further details see “Note 7 — Discontinued Operations —Sale of OMIDRIA”).

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 an Amended and Restated Royalty Purchase Agreement (the “Amendment”). The Amendment eliminated the previously existing annual caps on royalty payments 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.

To the extent our estimates of future royalties differ materially from the previous estimates, we will adjust for future OMIDRIA royalties to the present value of the revised estimated cash flows, discounted at the implied effective interest rate of 10.27% utilizing the cumulative catch-up method. We record interest expense as a component within continuing operations. Any such remeasurement adjustment is recognized as non-cash interest expense within continuing operations (see “Note 8 - OMIDRIA Royalty Obligation”).

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments

Cash and cash equivalents include highly liquid instruments with a maturity of three months or less on the date of purchase, which can be easily converted into cash without a significant impact on their value. Short-term investment securities are classified as held-to-maturity, except for money market funds, which are classified as available-for-sale. Investments classified as available-for-sale are measured at fair value. Investments classified as held-to-maturity are carried at cost. Amortization, accretion, interest, and dividends, realized gains and losses and declines in value judged to be other-than-temporary are included within other income.

The cost of securities sold is based on the specific-identification method. Investments with maturities of less than one year, or those for which management intends to use the investments to fund current operations, are included in current assets. We evaluate whether an investment is other-than-temporarily impaired based on the specific facts and circumstances. Factors that are considered in determining whether an other-than-temporary decline in value has occurred include: the market value of the security in relation to its cost basis; the financial condition of the investee; and the intent and ability to retain the investment for a sufficient period of time to allow for recovery in the market value of the investment. Restricted investments held in money-market funds include security deposits on our office lease.

Investment income, which is included as a component of other income, consists primarily of interest earned.

Receivables

Receivables relates primarily to sales of YARTEMLEA to wholesalers and include estimated chargebacks and product returns that are expected to be settled through reductions in receivables, royalties receivable from Rayner on sales of OMIDRIA and receivables from Novo Nordisk for work performed under the Transition Services Agreement. Considering the nature of our receivables, including that trade receivables are primarily due from a limited number of customers, we recorded no material allowance for expected credit losses as of March 31, 2026 and December 31, 2025, respectively.

Property and Equipment, Net

Property and equipment are stated at cost, and depreciation is calculated using the straight-line method over the estimated useful life of the assets, which is generally between three andten years. Expenditures for repairs and maintenance are expensed as incurred.

Inventory

Inventory is stated at the lower of cost or market determined on a specific identification basis in a manner that approximates the first-in, first-out (FIFO) method. Costs include amounts related to third-party manufacturing, transportation and internal labor and overhead. Capitalization of costs as inventory begins when regulatory approval of the product candidate is reasonably assured in the U.S. or the EU. We expense inventory costs related to product candidates as research and development expenses prior to receiving regulatory approval in the applicable territory. Inventory is reduced to net realizable value for excess and obsolete inventories based on forecasted demand.

Debt

The Company accounts for its convertible debt at carrying value, net of applicable discounts, premiums and debt issuance costs. These instruments are recognized as a single liability on the condensed consolidated balance sheets unless specific features require treatment under separate accounting guidance. Debt issuance costs, which include legal, accounting, and underwriting fees directly attributable to the financing, are presented as a direct deduction from the carrying amount of the convertible debt. These costs and any original issue discounts are amortized to interest expense over the contractual term of the debt using the effective interest method.

The Company classifies convertible debt as long-term or current based on the remaining maturity and the status of the conversion features at the balance sheet date. If the holders of the debt possess the right to convert the instrument into shares of the Company’s common stock within one year of the balance sheet date, or if the debt is otherwise callable, the respectivecarrying value of the converted debt is classified as current. The Company performs a periodic evaluation of the conversion conditions to ensure proper classification and to determine if the debt should be measured based on its settlement value. Upon conversion, the carrying value of the debt, including any unamortized costs, is typically reclassified to stockholders’ equity, and no gain or loss is recognized unless the conversion includes an inducement.

In February 2026, we repaid in full the remaining $17.1 million principal balance outstanding on our 2026 Notes upon maturity. On November 25, 2025, concurrent with the closing of the sale of zaltenibart to Novo Nordisk under the APLA, the Company repaid in full the $67.1 million principal balance outstanding under the Company’s Credit and Guarantee Agreement with certain funds managed by Athyrium Capital Management, LP and certain funds managed by Highbridge Capital Management, LLC, as lenders (the “Term Loan”). As of March 31, 2026, the Company has outstanding one series of convertible notes, which mature on June 15, 2029 (the “2029 Notes”) with an outstanding principal balance of $70.8 million. (For further details, see “Note 6 – Debt”).

Embedded Derivatives

We account for convertible instruments in accordance with ASC 470-20,Debt with Conversion and Other Options, when we determine that embedded conversion features do not require bifurcation from the host instrument. We account for convertible instruments (when we have determined that the embedded conversion options should be bifurcated from their host instruments) in accordance with ASC 815 –Derivative and Hedge Accounting (“ASC 815”). Under ASC 815, proceeds received upon the issuance of the hybrid contract are allocated between the fair value of the notes and the fair value of the derivative. The derivative is subsequently marked-to-market at each reporting date based on current fair value, with the changes in fair value reported in the condensed consolidated statements of operations and comprehensive loss.

The embedded derivative on our 2029 Notes represents the conversion feature and interest make-whole feature available to holders of the 2029 Notes allowing them to convert the notes into cash, common stock and/or a combination thereof. The embedded derivative on our Term Loan was eliminated upon repayment on November 25, 2025. (For further details, see “Note 4 – Fair Value Measurements” and “Note 6 – Debt”).

Right-of-Use Assets and Related Lease Liabilities

We record operating leases as right-of-use assets and recognize the related lease liabilities equal to the fair value of the lease payments using our incremental borrowing rate when the implicit rate in the lease agreement is not readily available. We recognize variable lease payments when incurred. Costs associated with operating lease assets are recognized on a straight-line basis within operating expenses over the term of the lease.

We record finance lease obligations as a component of property and equipment and amortize these assets within operating expenses on a straight-line basis to their residual values over the shorter of the term of the underlying lease or the estimated useful life of the equipment. The interest component of finance lease obligations is included in interest expense and recognized using the effective interest method over the lease term.

We account for leases with initial terms of 12 months or less as an operating expense.

Common Stock Repurchases

We have repurchased shares of our common stock from time to time under authorization made by our Board of Directors. Under applicable Washington State law, repurchased shares are retired and not presented separately as treasury stock in the condensed consolidated financial statements.

Financial Instruments and Concentrations of Credit Risk

Cash and cash equivalents, receivables, accounts payable and accrued liabilities, which are recorded at invoiced amount or cost, approximate fair value based on the short-term nature of these financial instruments. The fair value of short-term investments is based on quoted market prices. Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash and cash equivalents, short-term investments and receivables. Cash and cash equivalents are held by financial institutions and are federally insured up to certain limits. At times, our cash and cash equivalents balance held at a financial institution may exceed the federally insured limits. To limit the credit risk, we invest our excess cash in high-quality securities such as money market mutual funds, certificates of deposit and U.S. treasury bills.

Recent Accounting Pronouncements

In November 2024, the Financial Accounting Standards Board (“FASB”) issued ASU 2024-03,Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40):Disaggregation of Income Statement Expense (“ASU 2024-03”), requiring public entities to disclose additional information about specific expense categories in the notes to the financial statements on an interim and annual basis. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026, and for interim periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2024-03 on its consolidated financial statements.

In December 2025, the FASB issued ASU 2025-10,Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities(“ASU 2025-10”), which establishes authoritative guidance on the recognition, measurement, presentation, and disclosure of government grants. Under ASU 2025-10, government grants are recognized when it is probable that the entity will both comply with the conditions of the grant and the grant will be received. The ASU provides specific accounting models for grants related to assets and grants related to income, including options to recognize government grants as deferred income or as a reduction of the asset’s cost basis. The ASU also requires enhanced disclosures regarding the nature of government grants, significant terms and conditions, accounting policies applied, and amounts recognized in the financial statements. ASU 2025-10 is effective for fiscal years beginning after December 15, 2028, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2025-10 on its consolidated financial statements.

In December 2025, the FASB issued ASU 2025-11,Interim Reporting (Topic 270): Narrow-Scope Improvements (“ASU 2025-11”), which clarifies the guidance in Topic 270 to improve the consistency of interim financial reporting. The ASU provides a comprehensive list of required interim disclosures and introduces a disclosure principle requiring entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASU 2025-11 is effective for fiscal years beginning after December 15, 2027, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2025-11 on its consolidated financial statements.

Note 3—Net Income (Loss) Per Share

Basic net income (loss) per share (“Basic EPS”) is computed by dividing net income (loss) by the weighted average number of common shares outstanding during the period. Diluted net loss per share (“Diluted EPS”) is computed by dividing net income (loss) by the weighted average number of common shares and potentially dilutive common shares outstanding during the period. Our potentially dilutive securities include common shares related to our stock options calculated using the treasury stock method and convertible senior notes calculated using the if-converted method. In periods where we have a net loss from continuing operations but overall net income, we do not compute Diluted EPS because the effect would be antidilutive. When there is a net loss, potentially dilutive securities, like stock options or convertible debt, are typically excluded from the diluted net loss per share calculation. Potentially dilutive securities excluded from Diluted EPS are calculated based on a weighted average of days in the quarter from when the respective transactions occurred and are shown as follows:

Note 4—Fair-Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The accounting standard establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs, where available. The following summarizes the three levels of inputs required:

Level 1—Observable inputs for identical assets or liabilities, such as quoted prices in active markets;

Level 2—Inputs other than quoted prices in active markets that are either directly or indirectly observable; and

Level 3—Unobservable inputs in which little or no market data exists, therefore they are developed using estimates and assumptions developed by us, which reflect those that a market participant would use.

We review the fair value hierarchy classification on a quarterly basis. Changes in the observability of valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy. There have been no transfers of assets or liabilities between fair value measurement classifications during the three months ended March 31, 2026.

Our fair value hierarchy for our financial assets and liabilities measured at fair value on a recurring basis are as follows:

Cash held in demand deposit accounts of $1.9 million and $9.7 million is excluded from our fair-value hierarchy disclosure as of March 31, 2026 and December 31, 2025, respectively. The carrying amounts reported in the accompanying condensed consolidated balance sheets for receivables, accounts payable and accrued liabilities, and other current monetary assets and liabilities approximate fair value.

All our investments, which are classified as Level 1 assets, are short-term and held in our name. Money market funds are classified as available-for-sale.

Our embedded derivative is classified as a Level 3 liability. (For further details see “Note 6 – Debt”).

The fair value of our embedded derivative was determined using the Discounted Cash Flow model with the following key assumptions:

Changes in valuation assumptions could have a significant impact on the 2029 Note conversion option derivative. The Company can provide no assurance that changes in yield or in our stock price would not have a significant impact on the derivative in the future. An increase in our stock price volatility could increase the valuation of the 2029 Note conversion option derivative, whereas an increase in interest rates could decrease the valuation of the 2029 Note conversion option derivative. (For further details see “Note 6 — Debt”).

The following table sets forth the change in the fair value of the 2029 Note conversion option derivative for the three months ended March 31, 2026:

Note 5—Certain Balance Sheet Accounts

OMIDRIA Contract Royalty Asset

The OMIDRIA contract royalty asset consists of the following:

See “Note 7 — Discontinued Operations – Sale of OMIDRIA” for discussion regarding the estimated fair value of our OMIDRIA contract royalty asset.

The OMIDRIA contract royalty obligation consists of the following:

See “Note 8 — OMIDRIA Royalty Obligation” for further details.

Receivables

Receivables consist of the following:

Trade receivables represents sales of YARTEMLEA to wholesalers and include reductions for estimated chargebacks. OMIDRIA royalty receivables represent approximately two months of royalty earnings from Rayner. All U.S. royalties received from Rayner are remitted by Rayner to an escrow account, established by Omeros, from which payments are made on our behalf to DRI. These payments are entirely pass-through in nature to the Company with DRI as the recipient.

Property and Equipment, Net

Property and equipment, net consists of the following:

For the three months ended March 31, 2026 and 2025, depreciation and amortization expense was $0.2 million and $0.3 million, respectively.

Accrued Expenses

Accrued expenses consist of the following:

Deferred income as of March 31, 2026 and December 31, 2025 primarily related to billings to Novo Nordisk under the Transition Services Agreement.

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Note 6—Debt

Convertible senior notes, net, balances are comprised of the following:

2029 Notes

Exchange of 2026 Notes for 2029 Notes

On May 14, 2025, we completed the exchange (the “Convertible Note Exchange”) of $70.8 million in aggregate principal amount of our 2026 Notes on a one-for-one basis for newly-issued 2029 Notes. The Convertible Note Exchange was conducted with a limited number of holders of the 2026 Notes pursuant to exchange agreements dated as of May 12, 2025. The 2029 Notes are convertible at the option of the holders into shares of common stock, cash or a combination thereof, as elected by the Company, at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date.

The 2029 Notes were issued pursuant to an Indenture, dated as of August 14, 2020 (the “Base Indenture”), between the Company and Computershare Trust Company, National Association, as successor to Wells Fargo Bank, National Association, as trustee (the “Trustee”), as supplemented by a Second Supplemental Indenture, dated as of May 14, 2025 (the “Second Supplemental Indenture”), between the Company and the Trustee (the Base Indenture, as amended and supplemented by the Second Supplemental Indenture, the “Indenture”). The 2029 Notes will mature on June 15, 2029 unless earlier converted, redeemed or repurchased in accordance with their terms prior to such date.

Embedded Derivative

The embedded derivative on the 2029 Notes includes both a derivative for the interest make-whole feature and a derivative for the conversion feature available to holders allowing them to convert their notes to common stock, cash or a combination thereof. At each reporting date, we remeasure the embedded derivative instruments to fair market value. At contract inception, we recorded a net $23.0 million embedded derivative as a component of our 2029 Notes to the condensed consolidated balance sheet. At March 31, 2026 and December 31, 2025, the fair market value of our embedded derivative was $84.0 million and $157.2 million, respectively. We recorded a $73.1 million non-cash gain on the remeasurement of the embedded derivative in our condensed consolidated statement of operations and comprehensive income for the three months ended March 31, 2026. Increases or decreases in our stock price may materially affect the value of the derivative, and are shown as gains or losses in our condensed consolidated statement of operations and comprehensive income (loss).

Interest Make Whole Feature

Holders who convert their 2029 Notes prior to June 1, 2029 (except for any conversion in connection with a make-whole fundamental change) are entitled to an interest make-whole payment equal to the sum of the remaining scheduled payments of interest that would have been made had the 2029 Notes remained outstanding from their conversion date through the earlier of (i) the date that is 18 months following their conversion date, and (ii)June 15, 2029, the maturity date.

Conversion Feature

The 2029 Notes are convertible at the option of the holder into shares of common stock, cash or a combination thereof at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date. The Company elects whether the conversion occurs in common stock, cash or a combination thereof. The conversion rate is 161.81 shares of our common stock per $1,000 of note principal (equivalent to an initial conversion price of approximately $6.18 per share of common stock), which equals approximately 11.5 million shares issuable upon conversion. The conversion rate is subject to adjustment in certain circumstances as described in the Indenture.

The amount outstanding on the 2029 Notes is as follows:

As of March 31, 2026, our only debt commitment relates to the 2029 Notes, which mature on June 15, 2029.

Interest on the 2029 Notes is payable semi-annually in arrears at a rate of 9.50% per annum on each June 15 and December 15, beginning on December 15, 2025. The carrying value of the 2029 Notes includes a discount which we amortize over the duration of the term as non-cash interest expense in the consolidated statement of operations and comprehensive loss. Due to the discount amortization on the 2029 Notes, interest expense is currently being recognized at an implied effective interest rate of 1.82%.

The following table sets forth interest expense recognized related to the 2029 Notes:

The 2029 Notes are redeemable, in whole or in part, at our option at any time, and from time to time, on or after June 20, 2027 and on or before the 50 th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the 2029 Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date, but only if the last reported sale price per share of our common stock exceeds 130% of the conversion price on (i) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date we send the related redemption notice and (ii) the trading day immediately before the date we send such notice. In addition, calling any 2029 Note for redemption would constitute a “make-whole fundamental change” (as defined in the Indenture) with respect to that 2029 Note, in which case the conversion rate applicable to the conversion of that 2029 Note would be increased in certain circumstances if it is converted after it is called for redemption.

The 2029 Notes are structurally subordinated to all existing and future indebtedness and other liabilities, including trade payables, and (to the extent we are not a holder thereof) preferred equity, if any, of our subsidiaries.

Term Loan

On June 3, 2024, we entered into a Credit and Guarantee Agreement with funds managed by Athyrium Capital Management LP and funds managed by Highbridge Capital Management, LLC, as lenders, pursuant to which we had an outstanding Term Loan of $67.1 million.

The Transaction with Novo Nordisk, which closed on November 25, 2025, provided us with $240.0 million in upfront cash of which we used a portion at the time of closing to repay the entire $67.1 million outstanding principal amount of the Term Loan, along with a related prepayment premium, certain expenses and accrued and unpaid interest.

The following table sets forth interest expense recognized related to the Term Loan:

2026 Convertible Senior Notes

We had outstanding convertible senior notes that accrued interest at an annual rate of 5.25% per annum, payable semi-annually in arrears on February 15 and August 15 of each year. The 2026 Notes matured on February 15, 2026 and were paid in full at that time.

Amounts outstanding on our 2026 Notes as of March 31, 2026 and December 31, 2025 are as follows:

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The following table sets forth interest expense recognized related to the 2026 Notes:

Note 7—Discontinued Operations - Sale of OMIDRIA

On December 23, 2021, we sold the rights to OMIDRIA and related assets to Rayner, which is reported as discontinued operations in our condensed consolidated statements of operations and comprehensive loss and excluded from continuing operations for all periods presented.

The results of operations for OMIDRIA are recorded as income from discontinued operations for all periods presented in the condensed consolidated statements of operations and comprehensive loss are as follows:

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The following is a roll-forward of the OMIDRIA contract royalty asset (in thousands):

We remeasure the OMIDRIA contract royalty asset on a quarterly basis using the expected value approach, which incorporates actual results and future expectations.

Cash flow from discontinued operations is as follows:

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Net cash provided by discontinued operations primarily represents royalties received from Rayner. ​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.

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:

Note 9—Lease Liabilities

We have an operating lease for our office and laboratory facilities with an initial term that ends in November 2027 andtwo options to extend the lease term, each by an additional five years. Restricted investments of $1.1 million represent the security deposit on our office and laboratory facilities. We have finance leases for certain laboratory and office equipment that have lease terms expiring through October 2029.

Supplemental lease information is as follows:

The supplemental cash flow information related to leases is as follows:

Note 10—Commitments and Contingencies

Good and Service Contracts

We have various agreements with third parties that collectively require payment of termination fees totaling $25.8 million as of March 31, 2026 if we cancel the work within specific time frames, either prior to commencing or during performance of the contracted services.

Development Milestones and Product Royalties

We have entered a variety of development, collaboration, licensing or similar agreements with third parties under which we have accessed technology or services in connection with our development assets and programs. Some of these agreements require milestone payments based on achievements of development, regulatory or sales milestones, and/or very low-single digit royalties on net income or net sales of the relevant product. For the three months ended March 31, 2026 and 2025, royalties on sales of YARTEMLEA and development milestone expenses were not significant.

Note 11—Shareholders’** Deficit**

Common Stock

At-the-Market Sales Agreement - We have an “at the market” (“ATM”) facility agreement under which we have the capability to sell shares of our common stock, from time to time, through an ATM equity offering program. On November 14, 2025, the Company filed a shelf registration statement and prospectus supplement renewing the ATM for an aggregate offering price of up to $150.0 million. As of the date of this report, we have $150.0 million in shares of our common stock available to sell under our ATM program.

Share Repurchase Program - On November 29, 2025, the Board of Directors approved a share repurchase program under which we are permitted to repurchase from time to time up to $100.0 million of our common stock in the open market or through privately negotiated transactions. For the three months ended March 31, 2026, we repurchased and retired 0.4 million shares of common stock at an average cost of $11.70 for an aggregate purchase price of $4.2 million.

Note 12—Stock-Based Compensation

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Our equity incentive plans provide for the grant of incentive and non-qualified stock options, restricted stock awards, restricted stock units, and other stock awards to employees, non-employee directors, and consultants.

Stock-based compensation is as follows:

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The following assumptions were applied to all stock option grants:

Expected volatility is based on the historical volatility of our stock price weighted by grant issuances over the reporting period. We estimated the expected life of the stock options granted using the historical exercise behavior of option holders. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Forfeiture expense is estimated at the time of grant and revised in subsequent periods if actual forfeitures differ from those estimates.

Stock option activity for all stock plans and related information is as follows:

Of the 17.2 million common stock options outstanding as of March 31, 2026, options to purchase 6.0 million shares have an exercise price per share above $10.56, which was the closing price of our stock on the Nasdaq Global Market on March 31, 2026.

As of March 31, 2026, there were 4.9 million unvested options outstanding that will vest over a weighted-average period of 2.5 years. The total estimated compensation expense yet to be recognized on outstanding options is $11.4 million.

As of March 31, 2026, the total number of shares of common stock available for grant was 3.9 million.