# EDGAR Filing Document

**Accession Number:** 0001285819
**File Stem:** 0001437749-25-038758
**Filing Date:** 2025-12
**Character Count:** 23441
**Document Hash:** ab93ebb9d035b40c5c744d759b64c2bf
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001437749-25-038758.hdr.sgml**: 20251229

**ACCESSION NUMBER**: 0001437749-25-038758

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 15

**CONFORMED PERIOD OF REPORT**: 20251224

**ITEM INFORMATION**: Other Events

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20251229

**DATE AS OF CHANGE**: 20251229

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** OMEROS CORP
- **CENTRAL INDEX KEY:** 0001285819
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 911663741
- **STATE OF INCORPORATION:** WA
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-34475
- **FILM NUMBER:** 251602443

**BUSINESS ADDRESS:**
- **STREET 1:** 201 ELLIOTT AVENUE WEST
- **CITY:** SEATTLE
- **STATE:** WA
- **ZIP:** 98119
- **BUSINESS PHONE:** 206-676-5000

**MAIL ADDRESS:**
- **STREET 1:** 201 ELLIOTT AVENUE WEST
- **CITY:** SEATTLE
- **STATE:** WA
- **ZIP:** 98119

?xml version='1.0' encoding='ASCII'? omer20251218_8k.htm

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**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**WASHINGTON, D.C. 20549**

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**FORM 8-K**

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**CURRENT REPORT**

**Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934**

**Date of Report (Date of earliest event reported):** December 24, 2025

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## OMEROS CORPORATION
**(Exact name of Registrant as Specified in Its Charter)**

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| | | |
|:---|:---|:---|
| **Washington** | **001-34475** | **91-1663741** |
| **(State or Other Jurisdiction**<br> **of Incorporation)** | **(Commission File Number)** | **(IRS Employer**<br> **Identification No.)** |
| **201 Elliott Avenue West**<br> **Seattle, WA** |  | **98119** |
| **(Address of Principal Executive Offices)** |  | **(Zip Code)** |

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**Registrant**'**s Telephone Number, Including Area Code: (206) 676-5000**

**(Former Name or Former Address, if Changed Since Last Report)**

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities Registered Pursuant to Section 12(b) of the Act:

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| | | |
|:---|:---|:---|
| Title of each class | Trading Symbol(s) | Name of each exchange on which registered |
| Common stock, $0.01 par value per share | OMER | The Nasdaq Stock Market LLC |

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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

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**Item** 8**.01. Other Events.**

On December 24, 2025, Omeros Corporation (the "Company" or "we") issued a press release announcing that the U.S. Food and Drug Administration (FDA) has approved YARTEMLEA® (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), an often-fatal complication of stem-cell transplantation driven by activation of the lectin pathway of complement. A revised version of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The December 24, 2025 press release was revised to reflect the new date for the YARTEMLEA® approval-related conference call and to provide supplemental information regarding the experts quoted in the press release. No other changes were made.

**Item 9.01. Financial Statements and Exhibits.**

(d) Exhibits.

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| | |
|:---|:---|
| **Exhibit**<br> **Number** | **Description** |
| 99.1 | [Press Release dated December 24, 2025 (as revised)](ex_902630.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

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**SIGNATURES**

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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| | | |
|:---|:---|:---|
|  | **OMEROS CORPORATION** | **OMEROS CORPORATION** |
| Date: December 29, 2025 | By: | /s/ Gregory A. Demopulos |
|  |  | Gregory A. Demopulos, M.D. |
|  |  | President, Chief Executive Officer and |
|  |  | Chairman of the Board of Directors |

---

## Exhibit 99.1

**Exhibit 99.1**

![omeroslogo_2.jpg](omeroslogo_2.jpg)

**FDA Approves Omeros**' **YARTEMLEA**® – **First and Only Therapy Indicated for TA-TMA**

*– Omeros to Host Conference Call Wednesday, January 7, 2026 at 4:30 p.m. ET* –

● **First and only approved option:** YARTEMLEA® is the only approved treatment for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) and is indicated for adults and children ages two years and older.

● **High complete response (CR) rates:** YARTEMLEA-treated patients achieved CR rates of 61% in the pivotal trial and 68% in the Expanded Access Program (EAP) among those with evaluable patient-level response data; CR defined as improvement in key laboratory values *plus* either improved organ function or transfusion independence.

● **Strong survival benefit:** 100-day survival from TA-TMA diagnosis, based on all-cause mortality, was 73% in the pivotal trial and 74% in evaluable EAP patients; all patients met international harmonization criteria for high-risk TA-TMA.

● **Safety profile and Prescribing Information highlights:** The only approved TA-TMA therapy, YARTEMLEA has no Boxed Warning and no Risk Evaluation and Mitigation Strategy (REMS), and vaccinations are not required prior to treatment. Serious infections and other adverse reactions, regardless of causality, have occurred in patients treated with YARTEMLEA; see <u>Important Safety Information</u> for details.

SEATTLE, December 24, 2025 -- Omeros Corporation (NASDAQ: OMER) today announced that the U.S. Food and Drug Administration (FDA) has approved YARTEMLEA® (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), an often-fatal complication of stem-cell transplantation driven by activation of the lectin pathway of complement. YARTEMLEA is the first and only approved lectin pathway inhibitor. YARTEMLEA selectively inhibits MASP-2, the effector enzyme of the lectin pathway, blocking pathway activation while preserving classical and alternative complement functions important for host defense. YARTEMLEA is approved for use in adults and in children ages two years and older.

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"This approval is a long-awaited breakthrough in hematopoietic cell transplantation and TA-TMA care," stated Miguel-Angel Perales, M.D., Chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center. "Until now, we've lacked an effective TA-TMA therapy and relied largely on supportive measures such as modifying calcineurin inhibitors, which can significantly increase the risk of life-threatening graft-versus-host disease. Based on a compelling data package, narsoplimab delivers robust response rates and improved survival in TA-TMA, with a favorable benefit-risk profile and a safety profile consistent with that seen in patients undergoing hematopoietic stem cell transplantation. As the first and only drug approved for TA-TMA, narsoplimab is a practice-changing advance for patients facing this devastating complication."

Approval of YARTEMLEA was based on results from a single-arm, open-label study in adults with TA-TMA (the TA-TMA Study; N=28), supported by additional data from an expanded access program (EAP; N=221 adult and pediatric patients). In the EAP, 19 patients (13 adult and 6 pediatric) had evaluable patient-level response data.

Efficacy was assessed by TMA complete response (CR), defined as improvement in key laboratory markers of TMA (platelet counts and LDH levels) together with either improved organ function or transfusion independence. CR was achieved in 17/28 patients (61%) in the TA-TMA Study and 13/19 evaluable EAP patients (68%). Across the TA-TMA Study and the EAP, 100-day survival from the time of TMA diagnosis (based on all-cause mortality) was 73% (95% confidence interval CI: 52, 86) and 74% (95% CI: 48, 88), respectively. All patients met international harmonization criteria for high-risk TA-TMA, classifying each patient as having a poor prognosis and high risk of death.

In peer-reviewed publications, treatment with YARTEMLEA was associated with a three- to fourfold lower risk of mortality compared with an external control cohort.<sup>1</sup> In the EAP, YARTEMLEA was used both as first-line therapy and in high-risk TA-TMA patients who had failed or discontinued one or more prior regimens, namely off-label complement inhibitors and/or defibrotide. In these previously refractory high-risk patients, YARTEMLEA was associated with 50 percent one-year survival, compared with historical one-year survival rates reported as less than 20 percent.<sup>2 3 4 5</sup> 

"Just as in adults, YARTEMLEA's indication to treat TA-TMA in children two years of age and older is tremendously important," said Michelle Schoettler, M.D., Assistant Professor of Pediatric Oncology and Hematopoietic Cellular Therapy at Emory University. "Peer-reviewed clinical publications in TA-TMA have steadily advanced our understanding of the disease in children – its biology, diagnostic criteria, and increasing recognition – and have revealed the limitations and risks of relying on off-label options in this setting. Across the published pediatric experience, YARTEMLEA has produced strong and consistent benefit, including in very high-risk children with organ dysfunction and in those who have failed prior complement-inhibition therapy. When used first-line, YARTEMLEA has been associated with approximately 75 percent one-year survival; and even in children refractory to one or more off-label complement inhibitors, one-year survival is approximately triple historical rates that have remained below 20 percent. My clinical experience with YARTEMLEA through the expanded access program, including in very young patients, has reinforced that it needs to be readily available for children when TA-TMA emerges. With this approval, effective TA-TMA therapy can become the pediatric standard instead of the exception – and that will save children's lives."

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All patients in the TA-TMA Study had multiple risk factors for poor outcomes, and adverse reactions were reported regardless of causality or relatedness to YARTEMLEA. The most common adverse reactions (≥20%) were viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia. Serious adverse reactions occurred in 61% of YARTEMLEA-treated patients; those reported in >5% included acute kidney injury, confusional state, acute respiratory failure, neutropenic sepsis, septic shock, pulmonary edema, and vomiting. Fatal adverse reactions were reported in 7% of patients, including neutropenic sepsis and septic shock. No new clinically significant safety signals were identified in patients treated with YARTEMLEA in the EAP.

Following FDA approval of YARTEMLEA, Omeros is finalizing preparations for its U.S. product launch planned for January 2026. Dedicated U.S. billing and reimbursement codes are now in place, including:

● **Diagnosis Code:** ICD-10-CM code M31.11 specific to the diagnosis of "Hematopoietic Stem Cell Transplantation-Associated Thrombotic Microangiopathy"

● **Procedure Codes:** ICD-10-PCS codes XW03357 and XW04357 for introduction of narsoplimab monoclonal antibody into a peripheral vein or into a central vein, respectively

The YARTEMLEAssist™ patient support program is expected to be available in the first quarter of 2026. Providers and patient representatives can call 1-844-YARTEM1 (1-844-927-8361) for personalized services, including identifying potential financial assistance options.

"FDA's approval of YARTEMLEA marks a defining milestone for Omeros and, more importantly, for patients and families facing TA-TMA," said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. "After years of work and close collaboration with the transplant community, we can now offer the first FDA-approved therapy for this frequently fatal complication, with robust response data and a benefit-risk profile that supports confident use in both adults and children. With our U.S. launch planned for January 2026, our focus is on ensuring rapid, reliable access so that YARTEMLEA can be used when TA-TMA is recognized and time is critical. We are deeply grateful to the patients, caregivers, investigators, and clinical teams who made this approval possible, and we are committed to bringing YARTEMLEA to every eligible patient who needs it."

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TA-TMA can occur after both autologous and allogeneic hematopoietic stem cell transplantation, with higher prevalence following allogeneic transplant. Approximately 30,000 allogeneic transplants are performed each year in the U.S. and Europe. Recent studies estimate that TA-TMA develops in up to 56 percent of allogeneic transplant recipients.

A marketing authorization application for YARTEMLEA for the treatment of TA-TMA is currently under review by the European Medicines Agency with a decision expected in mid-2026.

**Important Safety Information for YARTEMLEA**®<br>**WHAT IS YARTEMLEA**®**?**

YARTEMLEA is a MASP-2 inhibitor indicated for the treatment of adults and children ages two years and older with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA).

**IMPORTANT SAFETY INFORMATION**

**Contraindications**

None.

**Warnings and Precautions**

Serious and life-threatening infections have occurred in patients treated with YARTEMLEA.

● In clinical trials in patients with TA-TMA, serious infections (regardless of causality) were reported in 36% (10/28) of patients receiving YARTEMLEA. Reported serious infections included sepsis, viral infections, pneumonia, bacteremia, fungal infection, gastroenteritis, respiratory tract infection, and urosepsis.

● If YARTEMLEA is administered to patients with active infections, monitor closely for worsening infection and treat promptly.

**Adverse Reactions**

The most common adverse reactions (≥20%), regardless of causality or relatedness to YARTEMLEA, were viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia.

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**Use in Specific Populations**

**Pregnancy:** Available data on the use of YARTEMLEA in pregnant women are insufficient to inform a drug-associated risk of major birth defects and miscarriage or adverse maternal or fetal outcomes.

**Lactation:** There are no data on the presence of YARTEMLEA in human milk, the effects on the breastfed child, or the effects on milk production.

**Pediatric Use:** The safety and effectiveness of YARTEMLEA for treatment of TA-TMA have been established in pediatric patients 2 years of age and older. The safety and effectiveness of YARTEMLEA have not been established in pediatric patients younger than 2 years of age.

**Geriatric Use:** Clinical studies of YARTEMLEA did not include sufficient numbers of patients 65 years of age and older to determine whether they respond differently than younger patients.

**To report suspected adverse reactions, contact Omeros Corporation at 1-844-YARTEM1 (1-844-927-8361), or contact FDA at 1-800-FDA-1088 or through FDA MedWatch.**

**Please see** <u>**Full Prescribing Information**</u> **for YARTEMLEA.**

**About YARTEMLEA**®

YARTEMLEA® (narsoplimab-wuug), a fully human monoclonal antibody, is the first and only approved inhibitor of the lectin pathway of complement. YARTEMLEA inhibits mannan-binding lectin-associated serine protease-2 (MASP-2), the effector enzyme of the lectin pathway. In hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), MASP-2 inhibition prevents lectin pathway-mediated cellular injury, including endothelial damage in small blood vessels, and thrombus formation. By selectively blocking activation of the lectin pathway, YARTEMLEA preserves classical and alternative pathway activity, including functions essential to the adaptive immune response.

YARTEMLEA is approved by the U.S. FDA for the treatment of TA-TMA in adults and in children ages two years and older. A marketing authorization application for YARTEMLEA for TA-TMA is under review by the European Medicines Agency (EMA) with a decision expected in mid-2026.

YARTEMLEA has received breakthrough therapy and orphan drug designations from the FDA for TA-TMA, and the EMA has granted it orphan drug designation in hematopoietic stem-cell transplantation.

YARTEMLEA is the first and only approved therapy for TA-TMA.

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**About Hematopoietic Stem Cell Transplant-Associated Thrombotic Microangiopathy**

Hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) is a severe and often-fatal complication of hematopoietic stem cell transplantation in adults and children. TA-TMA is driven by systemic endothelial injury triggered by conditioning regimens, immunosuppressants, infection, graft-versus-host disease, and other transplant-related factors, with activation of the lectin pathway of complement playing a central role in disease pathogenesis.

TA-TMA can occur following both autologous and allogeneic transplant, with higher prevalence after allogeneic procedures. Approximately 30,000 allogeneic transplants are performed annually in the U.S. and Europe. Recent studies estimate that TA-TMA develops in up to 56 percent of allogeneic transplant recipients. Mortality in severe TA-TMA can exceed 90 percent, and survivors frequently face long-term renal complications, including dialysis dependence.

YARTEMLEA® is the only approved treatment for TA-TMA.

**Conference Call and Webcast** <br> **Wednesday, January 7, 2026 at 4:30 p.m. Eastern Time**

Omeros management will host a conference call on January 7, 2026 at 4:30 p.m. Eastern Time to discuss the approval of YARTEMLEA®.

**Live webcast:** Access the live webcast at <u>https://investor.omeros.com/upcoming-events</u>.

**Conference call (phone):** To join by phone, participants must register at <u>https://register-conf.media-server.com/register/BI860d4c7c1e5d4bb1a77988a530e78171</u> to receive a unique PIN. After registering, you may either:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. dial in using the conference line and PIN provided at the registration site; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. select the "Call Me" option to receive an automated call to the phone number that you provide.

If you lose your PIN or registration confirmation email, please re-register to receive a new PIN.

**Replay:** A replay will be made available at <u>https://investor.omeros.com/archived-events</u>.

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**About Omeros Corporation**

Omeros is an innovative biotechnology company that discovers, develops, and commercializes first-in-class small-molecule and protein therapeutics for large-market and orphan indications, with particular emphasis on complement-mediated diseases, cancers, and addictive or compulsive disorders. Omeros' lead lectin pathway inhibitor YARTEMLEA®, which inhibits the pathway's effector enzyme MASP-2, is FDA-approved for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in adult and pediatric patients ages two years and older, with a planned U.S. launch in January 2026. A marketing authorization application for YARTEMLEA in TA-TMA is currently under review by the European Medicines Agency, with a decision expected in mid-2026. OMS1029, Omeros' long-acting MASP-2 inhibitor, has successfully completed Phase 1 clinical trials.

Under a recently announced asset purchase and licensing agreement, Novo Nordisk acquired global rights to zaltenibart (formerly OMS906), a MASP-3 inhibitor in clinical development for PNH and other alternative pathway indications, along with associated intellectual property and related assets. Omeros' pipeline also includes OMS527, a phosphodiesterase 7 inhibitor in clinical development for cocaine use disorder and fully funded by the National Institute on Drug Abuse, as well as a growing portfolio of novel molecular and cellular oncology programs. For more information about Omeros and its programs, visit <u>www.omeros.com</u>.

**References**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. Matsui H, Arai Y, Kanda J, et al. Survival in adults with high risk TA-TMA - a comparative analysis of narsoplimab versus supportive care. *Blood Adv*. 2025. doi:10.1182/bloodadvances.2025017540. **  

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. Schoettler ML, Pusarla SK, Nangia N, et al. Narsoplimab results in excellent survival in adults and children with hematopoietic cell transplant associated thrombotic microangiopathy (TA-TMA). *Am J Hematol*. 2025;100(11):2040-2051. doi:10.1002/ajh.70044.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. Schoettler ML, French K, Harris A, et al. D-dimer and sinusoidal obstructive syndrome-novel poor prognostic features of thrombotic microangiopathy in children after hematopoietic cellular therapy in a single institution prospective cohort study. *Am J Hematol*. 2024;99(3):370-379. doi:10.1002/ajh.27186.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4. Benítez Carabante MI, Bueno D, Alonso García L, et al. Use of eculizumab in pediatric patients with high-risk transplantation-associated thrombotic microangiopathy: outcomes and risk factors associated with response and survival. A retrospective study on behalf of the spanish group for hematopoietic transplantation and cellular therapy (GETH-TC). *Transplant Cell Ther*. 2024 Jun;30(6):601.e1-601.e13. doi: 10.1016/j.jtct.2024.03.019.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5. Acosta-Medina AA, Sridharan M, Go RS, et al. Clinical outcomes and treatment strategies of adult transplant-associated thrombotic microangiopathy: external validation of harmonizing definitions and high-risk criteria. *Am J Hematol*. 2025;100(5):830-839. doi:10.1002/ajh.27651.

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**Forward-Looking Statements**

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*Dr. Miguel-Angel Perales has previously received advisory services compensation from, and holds a financial interest in, Omeros. Dr. Michelle Schoettler has previously received advisory services compensation from Omeros.*

Jennifer Cook Williams<br> Cook Williams Communications, Inc.<br> Investor and Media Relations<br> <u>IR@omeros.com</u>