European Medicines Agency CHMP Recommends EU Approval of Partner Therapeutics IMREPLYS® (sargramostim, rhu GM-CSF) to Treat Exposure to Myelosuppressive Doses of Radiation (Haematopoietic Sub-synd...

LEXINGTON, Mass., June 20, 2025 /PRNewswire/ -- Partner Therapeutics, Inc. (PTx) today announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) has recommended approval of PTx's Marketing Authorisation Application (MAA) for IMREPLYS^® (sargramostim, rhu GM-CSF), the same formulation that was approved by the U.S. Food and Drug Administration (FDA) under the brand name LEUKINE^® in 2018. IMPREPLYS would be indicated for treatment of patients of all ages acutely exposed to myelosuppressive doses of radiation with Haematopoietic Sub-syndrome of Acute Radiation Syndrome (H-ARS). Approval by the European Commission (EC) is expected within 67 days of the CHMP recommendation. EC approval will enable sales, including government procurement for stockpiling, of IMREPLYS in all European Union (EU) member states, as well as Norway, Iceland, and Liechtenstein.

"We are grateful to the EMA for their support leading to this approval recommendation for IMREPLYS, which will enable access to the product throughout Europe for treatment of citizens for radiation injuries," said John L. McManus, President, Health Security and Critical Care of PTx. "Threats of use of tactical nuclear weapons underscore the importance of preparedness. The likelihood that initial medical treatment will occur in a severe, limited-resource environment complicates response planning and requires therapies that can be effective with minimal to no supportive care. Preparedness through stockpiling of such therapeutic solutions is intended to help reduce mortality if an event occurs that results in exposure to acute or sudden high-dose radiation. The approval recommendation from the EMA is an important step in PTx's international strategy for IMREPLYS to be available in the European market and beyond."

ABOUT IMREPLYS / LEUKINE (sargramostim)
Sargramostim is a human granulocyte-macrophage colony-stimulating growth factor (GM-CSF) produced by recombinant DNA technology in a yeast (S. cerevisiae) expression system. The binding to GM-CSF receptors expressed on the surface of target cells (haematopoietic progenitors and mature immune cells), initiates an intracellular signalling cascade which induces the cellular responses (i.e., division, maturation, activation). GM-CSF is a multilineage factor and, in addition to dose-dependent effects on the myelomonocytic lineage, it can promote the proliferation and maturation of megakaryocytic and erythroid progenitors. Sargramostim (LEUKINE) was approved by the US Food and Drug Administration in 2018 to increase survival in adult and pediatric patients from birth to 17 years of age acutely exposed to myelosuppressive doses of radiation (Hematopoietic Syndrome of Acute Radiation Syndrome [H-ARS]). 
The product is commercially available in the United States under the brand name LEUKINE. LEUKINE will continue to be accessible through a named patient program operated by Tanner Pharma Group outside of the United States, including in the European Union for named patient use outside of the H-ARS indication.

In the European Union, Iceland, Norway, and Liechtenstein, upon approval by the EC, IMPREPLYS would be indicated:

• For treatment of patients of all ages acutely exposed to myelosuppressive doses of radiation with Haematopoietic Sub-syndrome of Acute Radiation Syndrome (H-ARS).

In the United States, LEUKINE is indicated:

• To shorten time to neutrophil recovery and to reduce the incidence of severe and life-threatening infections and infections resulting in death following induction chemotherapy in adult patients 55 years and older with acute myeloid leukemia (AML).
• For the mobilization of hematopoietic progenitor cells into peripheral blood for collection by leukapheresis and autologous transplantation in adult patients.
• For the acceleration of myeloid reconstitution following autologous bone marrow or peripheral blood progenitor cell transplantation in adult and pediatric patients 2 years of age and older.
• For the acceleration of myeloid reconstitution following allogeneic bone marrow transplantation in adult and pediatric patients 2 years of age and older.
• For treatment of delayed neutrophil recovery or graft failure after autologous or allogeneic bone marrow transplantation in adult and pediatric patients 2 years of age and older.
• To increase survival in adult and pediatric patients from birth to 17 years of age acutely exposed to myelosuppressive doses of radiation (Hematopoietic Syndrome of Acute Radiation Syndrome [H-ARS]).

Important Safety Information for LEUKINE (sargramostim)
Contraindications

• Do not administer LEUKINE to patients with a history of serious allergic reaction, including anaphylaxis, to human granulocyte-macrophage colony-stimulating factor, sargramostim, yeast-derived products, or any other component of LEUKINE.

Warnings and Precautions

• Serious hypersensitivity reactions, including anaphylactic reactions, have been reported with LEUKINE. If a serious allergic or anaphylactic reaction occurs, immediately discontinue LEUKINE therapy, and institute medical management. Discontinue LEUKINE permanently for patients with serious allergic reactions.
• LEUKINE can cause infusion-related reactions that may be characterized by respiratory distress, hypoxia, flushing, hypotension, syncope, and/or tachycardia. Observe closely during infusion, particularly in patients with preexisting lung disease; dose adjustment or discontinuation may be needed.
• LEUKINE should not be administered simultaneously with or within 24 hours preceding cytotoxic chemotherapy or radiotherapy or within 24 hours following chemotherapy.
• Edema, capillary leak syndrome, and pleural or pericardial effusions have been reported in patients after LEUKINE administration. LEUKINE should be used with caution in patients with preexisting fluid retention, pulmonary infiltrates, or congestive heart failure. Such patients should be monitored.
• Supraventricular arrhythmia has been reported in uncontrolled studies during LEUKINE administration, particularly in patients with a history of cardiac arrhythmia. Use LEUKINE with caution in patients with preexisting cardiac disease.
• If absolute neutrophil count (ANC) > 20,000 cells/mm3 or if white blood cell (WBC) counts > 50,000/mm3, LEUKINE administration should be interrupted, or the dose reduced by half. Monitor complete blood counts (CBC) with differential twice per week.
• Discontinue LEUKINE therapy if tumor progression, particularly in myeloid malignancies, is detected during LEUKINE treatment.
• Treatment with LEUKINE may induce neutralizing anti-drug antibodies. Use LEUKINE for the shortest duration needed.
• Avoid administration of solutions containing benzyl alcohol (including LEUKINE for injection reconstituted with Bacteriostatic Water for Injection, USP [0.9 % benzyl alcohol]) to neonates and low birth weight infants.

Drug Interactions

• Avoid the concomitant use of LEUKINE and products that induce myeloproliferation. Monitor for clinical and laboratory signs of excess myeloproliferative effects.

Adverse Reactions
Adverse events occurring in >10% of patients receiving LEUKINE in controlled clinical trials and reported at a higher frequency than in placebo patients are:

• In recipients of autologous bone marrow transplantation (BMT)–asthenia, malaise, diarrhea, rash, peripheral edema, urinary tract disorder
• In recipients of allogeneic BMT–abdominal pain, chills, chest pain, diarrhea, nausea, vomiting, hematemesis, dysphagia, GI hemorrhage, pruritus, bone pain, arthralgia, eye hemorrhage, hypertension, tachycardia, bilirubinemia, hyperglycemia, increased creatinine, hypomagnesemia, edema, pharyngitis, epistaxis, dyspnea, insomnia, anxiety, high glucose, low albumin
• In patients with AML–fever, weight loss, nausea, vomiting, anorexia, skin reactions, metabolic laboratory abnormalities, edema

Please see full Prescribing Information for LEUKINE at www.leukine.com.

ABOUT PARTNER THERAPEUTICS
Partner Therapeutics, Inc. (PTx), an integrated biotechnology company, focuses on development and commercialization of late-stage therapeutics to improve health outcomes in treatment of cancer and other serious diseases. The company believes in delivering products and supporting medical teams with the purpose of achieving superior outcomes for patients and their families. Visit www.partnertx.com.

Reference
LEUKINE (sargramostim) injection - Full Prescribing Information available at: https://www.leukine.com/prescribing-information.pdf

PARTNER THERAPEUTICS^®, IMREPLYS^®, and LEUKINE^® are registered trademarks owned by Partner Therapeutics, Inc. ©2025 Partner Therapeutics, All rights reserved.

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