Note 1 - Organization and Basis of Presentation	12 Months Ended
Dec. 31, 2023
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Note 1—Organization and Basis of Presentation General Omeros Corporation (“Omeros,” the “Company” or “we”) is a clinical-stage biopharmaceutical company committed to discovering, developing and commercializing small-molecule and protein therapeutics for large-market as well as orphan indications targeting immunologic disorders including complement-mediated diseases, cancers, and addictive and compulsive disorders. We marketed our first drug product OMIDRIA® (phenylephrine and ketorolac intraocular solution) 1% / 0.3% for use during cataract surgery or intraocular lens replacement in the United States (the “U.S.”) until we sold OMIDRIA and related business assets on December 23, 2021 (see “Sale of OMIDRIA Assets” below for additional information). Our pipeline of clinical-stage development programs includes: 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; OMS906, our antibody targeting mannan-binding lectin-associated serine protease-3 ("MASP-3"), the key activator of the alternative pathway of complement; and OMS527, our phosphodiesterase 7 ("PDE7") inhibitor program. Clinical development of narsoplimab is currently focused primarily on hematopoietic stem cell transplant-associated thrombotic microangiopathy ("TA-TMA"). Our Biologics License Application ("BLA") for narsoplimab in TA-TMA is anticipated to be resubmitted with additional information to support potential approval of narsoplimab in this indication. In October 2023, we announced the results of a pre-specified interim analysis of our Phase 3 ARTEMIS-IGAN trial evaluating narsoplimab for the treatment of immunoglobulin A ("IgA") nephropathy. Topline results showed that narsoplimab did not reach statistically significant improvement over placebo on the primary endpoint of reduction in proteinuria. Based on this result, we have discontinued the ARTEMIS-IGAN clinical trial. Phase 1 and Phase 2 clinical programs are underway in our other clinical-stage assets. Sale of OMIDRIA Assets 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. Rayner paid us $126.0 million in cash at closing, and we retained all outstanding accounts receivable, accounts payable and accrued expenses as of the closing date. Additionally, we are entitled to future royalty payments on net sales of OMIDRIA. Under the Asset Purchase Agreement, Omeros is entitled to receive a milestone payment of $200.0 million (the “Milestone Payment”) following an event (the "Milestone Event") that establishes separate payment for OMIDRIA for a continuous period of at least four years when furnished in the ambulatory surgery center (“ASC”) setting. In December 2022, the Milestone Event occurred and we recorded a $200.0 million milestone receivable. We received the Milestone Payment in February 2023. As a result of the divestiture, the results of OMIDRIA operations (e.g., revenues and operating costs) have been reclassified to discontinued operations in our consolidated statements of operations and comprehensive income (loss) and excluded from continuing operations for all periods presented (See“Note 7 – Discontinued Operations – Sale of OMIDRIA ”). Basis of Presentation Our 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 consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). Liquidity and Capital Resources As of December 31, 2023, we had cash, cash equivalents and short-term investments of $171.8 million. Our cash provided by operations for the year ended December 31, 2023 was $74.7 million and included our 2023 net loss for the year of $117.8 million and collection of the $200.0 million Milestone Payment in the first quarter of 2023. We extinguished $95.0 million outstanding of convertible senior notes at maturity in November 2023. In February 2024, we received $115.5 million upon the sale to DRI Healthcare Acquisition LP ("DRI") of substantially all of our expected remaining U.S.-only Rayner OMIDRIA royalty receipts payable through December 31, 2031 (see “Note 8 - OMIDRIA Royalty Obligation”). Historically, we have incurred net losses from continuing operations and negative operating cash flows. We have not yet established an ongoing source of revenue sufficient to cover our operating costs; therefore, we potentially need to continue to raise additional capital to accomplish our business plan and to retire our outstanding convertible senior notes due in 2026. We plan to continue to fund our operations for at least the next twelve months with our existing cash and investments and the $115.5 million we received in February 2024 from DRI. We have a sales agreement to sell shares of our common stock, from time to time, in an “at the market” equity offering facility through which we may offer and sell shares of our common stock equaling an aggregate amount up to $150.0 million. Should it be determined to be strategically advantageous, we could pursue debt financings as well as public and private offerings of our equity securities, similar to those we have previously completed, or other strategic transactions, which may include licensing a portion of our existing technology. Should it be necessary to manage our operating expenses, we could also reduce our projected cash requirements by delaying clinical trials, reducing selected research and development efforts, or implementing other restructuring activities. Segments We operate in one segment. Management uses cash flow as the primary measure to manage our business and does not segment our business for internal reporting or decision-making. 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 OMIDRIA contract royalty asset valuation, stock-based compensation expense, and accruals for clinical trials and manufacturing of drug product. 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 1 - Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

Note 1—Organization and Basis of Presentation

General

Omeros Corporation (“Omeros,” the “Company” or “we”) is a clinical-stage biopharmaceutical company committed to discovering, developing and commercializing small-molecule and protein therapeutics for large-market as well as orphan indications targeting immunologic disorders including complement-mediated diseases, cancers, and addictive and compulsive disorders. We marketed our first drug product OMIDRIA® (phenylephrine and ketorolac intraocular solution) 1% / 0.3% for use during cataract surgery or intraocular lens replacement in the United States (the “U.S.”) until we sold OMIDRIA and related business assets on December 23, 2021 (see “Sale of OMIDRIA Assets” below for additional information).

Our pipeline of clinical-stage development programs includes: 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; OMS906, our antibody targeting mannan-binding lectin-associated serine protease-3 ("MASP-3"), the key activator of the alternative pathway of complement; and OMS527, our phosphodiesterase 7 ("PDE7") inhibitor program.

Clinical development of narsoplimab is currently focused primarily on hematopoietic stem cell transplant-associated thrombotic microangiopathy ("TA-TMA"). Our Biologics License Application ("BLA") for narsoplimab in TA-TMA is anticipated to be resubmitted with additional information to support potential approval of narsoplimab in this indication. In October 2023, we announced the results of a pre-specified interim analysis of our Phase 3 ARTEMIS-IGAN trial evaluating narsoplimab for the treatment of immunoglobulin A ("IgA") nephropathy. Topline results showed that narsoplimab did not reach statistically significant improvement over placebo on the primary endpoint of reduction in proteinuria. Based on this result, we have discontinued the ARTEMIS-IGAN clinical trial.

Phase 1 and Phase 2 clinical programs are underway in our other clinical-stage assets.

Sale of OMIDRIA Assets

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. Rayner paid us $126.0 million in cash at closing, and we retained all outstanding accounts receivable, accounts payable and accrued expenses as of the closing date. Additionally, we are entitled to future royalty payments on net sales of OMIDRIA.

Under the Asset Purchase Agreement, Omeros is entitled to receive a milestone payment of $200.0 million (the “Milestone Payment”) following an event (the "Milestone Event") that establishes separate payment for OMIDRIA for a continuous period of at least four years when furnished in the ambulatory surgery center (“ASC”) setting. In December 2022, the Milestone Event occurred and we recorded a $200.0 million milestone receivable. We received the Milestone Payment in February 2023.

As a result of the divestiture, the results of OMIDRIA operations (e.g., revenues and operating costs) have been reclassified to discontinued operations in our consolidated statements of operations and comprehensive income (loss) and excluded from continuing operations for all periods presented (See“Note 7 – Discontinued Operations – Sale of OMIDRIA ”).

Basis of Presentation

Our 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 consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”).

Liquidity and Capital Resources

As of December 31, 2023, we had cash, cash equivalents and short-term investments of $171.8 million. Our cash provided by operations for the year ended December 31, 2023 was $74.7 million and included our 2023 net loss for the year of $117.8 million and collection of the $200.0 million Milestone Payment in the first quarter of 2023. We extinguished $95.0 million outstanding of convertible senior notes at maturity in November 2023. In February 2024, we received $115.5 million upon the sale to DRI Healthcare Acquisition LP ("DRI") of substantially all of our expected remaining U.S.-only Rayner OMIDRIA royalty receipts payable through December 31, 2031 (see “Note 8 - OMIDRIA Royalty Obligation”).

Historically, we have incurred net losses from continuing operations and negative operating cash flows. We have not yet established an ongoing source of revenue sufficient to cover our operating costs; therefore, we potentially need to continue to raise additional capital to accomplish our business plan and to retire our outstanding convertible senior notes due in 2026. We plan to continue to fund our operations for at least the next twelve months with our existing cash and investments and the $115.5 million we received in February 2024 from DRI. We have a sales agreement to sell shares of our common stock, from time to time, in an “at the market” equity offering facility through which we may offer and sell shares of our common stock equaling an aggregate amount up to $150.0 million. Should it be determined to be strategically advantageous, we could pursue debt financings as well as public and private offerings of our equity securities, similar to those we have previously completed, or other strategic transactions, which may include licensing a portion of our existing technology. Should it be necessary to manage our operating expenses, we could also reduce our projected cash requirements by delaying clinical trials, reducing selected research and development efforts, or implementing other restructuring activities.

Segments

We operate in one segment. Management uses cash flow as the primary measure to manage our business and does not segment our business for internal reporting or decision-making.

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 OMIDRIA contract royalty asset valuation, stock-based compensation expense, and accruals for clinical trials and manufacturing of drug product. 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.