The European Commission granted a marketing authorisation valid throughout the European Union for Ristempa on 13 April 2015. Ristempa contains the active substance pegfilgrastim and is used in cancer patients to help with some of the side effects of their treatment. Ristempa is used to reduce the duration of neutropenia and the occurrence of febrile neutropenia (neutropenia with fever). The drug cannot be used in patients with chronic myeloid leukaemia. It also cannot be used in patients with myelodysplastic syndromes. Ristempa is available as a solution for injection in pre-filled syringes containing 6 mg pegfilgrastim. It is given as a single 6 mg injection under the skin around 24 hours after the end of each cycle of chemotherapy. Patients can inject themselves if they have been trained appropriately. Pegfilgrastim consists of filgrastim which is very similar to a human protein called granulocyte colony stimulating factor (G‑CSF), that has been ‘pegylated’ (attached to a chemical called polyethylene glycol). Filgrastim works by stimulating the bone marrow to produce more white blood cells, increasing white blood cell counts and treating neutropenia.

Filgrastim has been available in other medicines in the European Union (EU) for a number of years. Because it is pegylated in pegfilgrastim, the rate at which the medicine is removed from the body is decreased, allowing the medicine to be given less often. Ristempa has been studied in two main studies involving 467 patients with breast cancer who were being treated with cytotoxic chemotherapy. In both studies, a single injection of Ristempa was compared with multiple daily injections of filgrastim during each of four chemotherapy cycles. The main measure of effectiveness was the duration of severe neutropenia during the first cycle of chemotherapy.

Ristempa was as effective as filgrastim in reducing the duration of severe neutropenia. In both studies, the patients had severe neutropenia for around 1.7 days during their first chemotherapy cycle, compared with around five to seven days when neither medicine is used. The most common side effects with Ristempa (seen in more than 1 in 10 patients) are bone and muscle pain, headache and nausea (feeling sick).