Positive data have been reported from a phase II study of an investigational orally administered tyrosine kinase inhibitor, masitinib, in imatinib resistant gastrointestinal stromal tumours (GIST).

The study involved 44 patients with inoperable, locally advanced or metastatic GIST whose disease had progressed on imatinib (400 to 800 mg/day).They were assigned to either masitinib (n= 23) 12 mg/kg/day or sunitinib (n= 21) until progression. After a median follow-up of 14 months, median overall survival was not reached for masitinib vs. 15 months for sunitinib (p=0.022). After 18 months, 79% of patients treated with masitinib were still alive, vs. 20% for patients treated with sunitinib. After 2 years, 53% of patients treated with masitinib were still alive, vs. 0% on sunitinib. There was a lower occurrence of severe adverse events in the masitinib group; the most common masitinib related adverse events were nausea, diarrhoea and asthenia.

Full data have been submitted for publication to the American Society of Clinical Oncology (ASCO) 2012 Annual Meeting. Masitinib has received orphan drug designation in the treatment of GIST from both the FDA and EMA.