The European Commission granted a marketing authorisation valid throughout the European Union for Imbruvica on 21 October 2014. Imbruvica is a cancer medicine (designated as orphan drug) that is used to treat two types of blood cancer: chronic lymphocyticleukaemia and mantle cell lymphoma; both are cancers affecting a type of white blood cells called B lymphocytes. In chronic lymphocytic leukaemia, Imbruvica is used in patients who have received at least one previous treatment, and in patients who have genetic mutations in their cancer cells called 17p deletion or TP53 mutation that make them unsuitable for treatment with a combination of chemotherapy medicines and immunotherapy (treatments that stimulate the immune system to kill cancer cells). In mantle cell lymphoma, Imbruvica is used in patients whose disease does not respond to or has come back after previous treatment. The active substance in Imbruvica, ibrutinib, works by blocking an enzyme called Bruton’s tyrosine kinase (Btk), which is mostly found in B lymphocytes. Btk promotes survival of B lymphocytes and their migration to the organs where these cells normally divide. By blocking Btk, ibrutinib decreases survival and migration of B lymphocytes, thereby delaying the progression of the cancer. In a main study involving 391 patients with chronic lymphocytic leukaemia that did not respond to or had come back after previous treatment, Imbruvica was shown to be more effective than ofatumumab (another cancer medicine) at delaying progression of the cancer. After 1 year of treatment, around 66% of patients receiving Imbruvica were still alive with their disease not having progressed compared with around 6% of patients receiving ofatumumab. Imbruvica was also more effective than ofatumumab in the subgroup of patients with the 17p deletion/TP53 mutation. Imbruvica was also investigated in a main study involving 111 patients with mantle cell lymphoma that did not respond to or had come back after previous  treatment. In this study Imbruvica was not compared with any other treatment. Results of the study showed Imbruvica to be effective, with around 68% of patients having either a complete or partial response to treatment: 21% of patients had a complete response (i.e. disappearance of all signs of cancer following treatment) and 47% had a partial response (i.e. the patient improved but some signs of the disease remained). The average duration of response to treatment was 17.5 months. The most common side effects are diarrhoea, musculoskeletal pain (pain in muscles and bones), upper respiratory tract infections (colds), bruising, rash, nausea (feeling sick), pyrexia (fever), neutropenia (low levels of neutrophils, a type of white blood cell) and constipation. The most serious side effects are anaemia (low red blood cell counts), neutropenia, pneumonia (lung infection) and thrombocytopenia (low blood platelet counts).