Exceptional Use Recommendation for Nuclear Emergency Drug

The European Medicines Agency’s (EMA) Committee for Medicinal Products for Human Use (CHMP) has recommended an exceptional circumstances marketing authorization for Imreplys. The drug — active ingredient sargramostim and manufactured by Partner Therapeutics Ltd — is intended to treat people with hematopoietic acute radiation syndrome (H-ARS) following acute exposure to myelosuppressive doses of radiation. 

H-ARS occurs when radiation suppresses bone marrow hematopoiesis, leading to an increased risk for infection and bleeding. It occurs after whole-body radiation doses of about 1-6 Gy, most often associated with acute exposure following radiologic or nuclear emergencies. Sargramostim, a granulocyte-macrophage colony-stimulating factor, counteracts H-ARS by inducing the bone marrow to produce immune-protective leukocytes, including granulocytes, macrophages, and monocytes, as well as red blood cells and platelets.

The positive opinion means that Imreplys is now indicated for treatment of patients of all ages with H-ARS following acute exposure to myelosuppressive doses of radiation. It has also been used in the US in patients aged 2 years or older to prevent serious infection in conditions such as leukemia, bone marrow transplant, and prechemotherapy blood cell collection. 

As well as the infection risk, symptoms of H-ARS may include those of anemia, petechiae, and prolonged bleeding, starting 1-6 hours after exposure and lasting up to 2 days.

Exceptional Circumstances Authorization Recommended

Medicines can be authorized under exceptional circumstances, subject to certain specific obligations where the applicant was unable to provide comprehensive data on the efficacy and safety of the medicine under normal conditions of use. This may be because the condition that the drug is to be used for is too rare for extensive data gathering; because of limited scientific knowledge in the area concerned; or because collection of full information is not possible or is unethical. Exceptional circumstances authorization must be reviewed annually.

The CHMP said that three randomized, blinded, placebo-controlled studies in rhesus monkeys who received H-ARS-inducing total body irradiation showed that Imreplys increased 60-day survival rates compared with placebo. Studies had also shown faster recovery of absolute neutrophil counts and platelets, reduced infection rates, and fewer signs of sepsis. 

The most common side effects with Imreplys include fever, diarrhea, vomiting, skin reactions, rash, asthenia, metabolic laboratory abnormalities, malaise, high glucose, abdominal pain, weight loss, low albumin, pruritus, gastrointestinal hemorrhage, chills, pharyngitis, bone pain, chest pain, hypomagnesemia, hematemesis, arthralgia, anxiety, and eye hemorrhage.

Use Governed by Radiologic/Nuclear Emergency Recommendations

The EMA said that Imreplys will be available as a 250 μg powder for solution for injection and should be used in accordance with official radiologic/nuclear emergency recommendations.

Detailed recommendations for the use of the product will be described in the summary of product characteristics (SmPC), which will be published on the EMA website in all official European Union languages after the marketing authorization has been granted by the European Commission.