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Masitinib mesylate in imatinib-resistant advanced GIST: A randomized phase II trial.
Session Type and Session Title:
Oral Abstract Session, Sarcoma
J Clin Oncol 30, 2012 (suppl; abstr 10007)
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Background: Masitinib is an oral tyrosine kinase inhibitor with greater in vitro activity and selectivity than imatinib against wild-type and juxtamembrane mutations of KIT (Dubreuil, 2009, PLoSONE). This trial studied efficacy and safety of masitinib at 12 mg/kg/day and sunitinib at 50 mg/day for the treatment of imatinib-resistant GIST. Methods: Patients with inoperable, locally advanced or metastatic GIST and showing disease progression while treated with imatinib 400 mg/day received either masitinib or sunitinib until progression. Primary endpoint was PFS evaluated with RECIST with OS as a secondary endpoint. Based upon an 80% power to detect with a Fleming design a median PFS ≥3 months (alpha 10%, unilateral), a population of 44 patients (22 per arm) was required. Stratification was applied based on mutation status. Results: 44 patients (exon 11 [66%], exon 9 [11%], wild-type or other [5%], not done at baseline [18%]) were randomized into masitinib (n=23) or sunitinib (n=21) treatment-arms from 9 centers between 02/2009 and 09/2011. After a median follow-up of 14 months, median PFS was 3.9 months (95%CI [2.6;8.1]) for masitinib vs 3.8 months [1.9;11] for sunitinib. Of those patients progressing under masitinib, 88% received sunitinib in third line. Median OS was not reached (NR) (95%CI [21;NR]) for masitinib vs 15 months [9.4;22] for sunitinib. The 18-month and 24-month OS rates for masitinib vs sunitinib were 79% (95%CI [53;92]) vs 20% [1.5;55], and 53% (95%CI [9.5;84]) vs 0%, respectively. Similar results were seen in the exon 11 subpopulation with median OS for masitinib NR (95%CI [NR;NR]) vs 15 months [9.6;22] for sunitinib. The safety profile of masitinib was better than sunitinib with a lower occurrence of severe related adverse events (AEs) (17% vs 52%) and related AEs leading to discontinuation (0% vs 9.5%). In masitinib treated patients, nausea, diarrhea and asthenia were the most common related AEs. Conclusions: Although PFS curves looked similar, this study apparently showed a longer survival in the masitinib treatment-arm with a better safety profile than sunitinib. Masitinib may potentially offer patients a new active compound for advanced GIST in the second-line setting.
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