Partner Therapeutics announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency has recommended approval of the company's Marketing Authorisation Application for IMREPLYS® (sargramostim, rhu GM-CSF) to treat patients of all ages acutely exposed to myelosuppressive doses of radiation with Haematopoietic Sub-syndrome of Acute Radiation Syndrome (H-ARS). The recommendation represents a significant milestone for radiation emergency preparedness in Europe.
IMREPLYS contains the same formulation that was approved by the U.S. Food and Drug Administration under the brand name LEUKINE® in 2018. European Commission approval is expected within 67 days of the CHMP recommendation, which will enable sales and government procurement for stockpiling across all European Union member states, as well as Norway, Iceland, and Liechtenstein.
Strategic Importance for European Preparedness
"Threats of use of tactical nuclear weapons underscore the importance of preparedness," said John L. McManus, President, Health Security and Critical Care of Partner Therapeutics. "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."
The approval recommendation supports Partner Therapeutics' international strategy to make IMREPLYS available in the European market and beyond. McManus emphasized that preparedness through stockpiling of therapeutic solutions is intended to help reduce mortality if an event occurs that results in exposure to acute or sudden high-dose radiation.
Mechanism of Action and Clinical Profile
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 compound binds to GM-CSF receptors expressed on the surface of target cells, including haematopoietic progenitors and mature immune cells, initiating an intracellular signalling cascade that induces cellular responses such as division, maturation, and activation.
As a multilineage factor, GM-CSF demonstrates dose-dependent effects on the myelomonocytic lineage and can promote the proliferation and maturation of megakaryocytic and erythroid progenitors. This broad hematopoietic activity makes it particularly valuable for treating radiation-induced bone marrow suppression.
Current Market Access and Indications
The product is commercially available in the United States under the brand name LEUKINE, with multiple approved indications including shortening time to neutrophil recovery in acute myeloid leukemia patients, mobilization of hematopoietic progenitor cells, and acceleration of myeloid reconstitution following bone marrow transplantation.
LEUKINE continues 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.
Safety Profile and Contraindications
The safety profile includes contraindications for patients with a history of serious allergic reactions to human GM-CSF, sargramostim, yeast-derived products, or any component of LEUKINE. Serious hypersensitivity reactions, including anaphylactic reactions, have been reported and require immediate discontinuation and medical management.
Additional warnings include potential infusion-related reactions characterized by respiratory distress, hypoxia, flushing, hypotension, syncope, and tachycardia. The drug should not be administered simultaneously with or within 24 hours of cytotoxic chemotherapy or radiotherapy. Other precautions include monitoring for edema, capillary leak syndrome, cardiac arrhythmias, and excessive myeloproliferation.
