BACKGROUND KIT has been suggested to be a potential therapeutic target for malignant melanoma. We evaluated the antitumor activity and safety of the KIT inhibitor nilotinib in metastatic melanoma patients harboring KIT gene mutations or amplifications.

METHODS We conducted a phase II multicenter trial of nilotinib in metastatic malignant melanoma with KIT mutations or amplifications. Patients received 400 mg oral nilotinib twice daily. The primary endpoint was response rate, and if seven or more responders were observed from the cumulative 36 patients, nilotinib would be considered worthy of further testing in this study population.

RESULTS Between October 2009 and June 2013, 176 patients underwent molecular screening for KIT gene aberrations, and 42 patients harboring KIT gene mutations and/or amplification were enrolled in the study. Overall, 25 (59.5%), 15 (35.7%), and 2 (4.8%) patients had KIT mutations, KIT amplifications, and both KIT mutations and amplification, respectively. Of the 42 enrolled patients, 1 patient achieved complete response, 6 patients achieved partial response, and 17 patients achieved stable disease, resulting in an overall response rate of 16.7% (95% confidence interval [CI]: 5.4%-28.0%) and a disease control rate of 57.1% (95% CI: 42.1%-72.1%). The median duration of response was 34 weeks (range: 5-55 weeks). Of the 7 responders, 6 patients had KIT mutations (exon 11: 5 patients; exon 17: 1 patient), and 1 patient had KIT amplification only.

CONCLUSION Although this study did not meet its primary endpoint of response rate, nilotinib showed durable response in a subset of metastatic melanoma patients with specific KIT mutations.

IMPLICATIONS FOR PRACTICE KIT aberration can be detected in a subset of metastatic melanoma patients. This phase II trial showed that nilotinib demonstrates durable response in a subset of patients with KIT mutations. The safety profile was very tolerable. This study suggests that a KIT inhibitor may benefit a small subset of metastatic melanoma patients with KIT mutations.