BKM120 combined with vemurafenib in vemurafenib-refractory BRAF mutant metastatic melanoma: Two cases.

Abstract

e20010 Background: PTEN loss and PI3K activation are common in BRAF mutant metastatic melanoma, and PI3K activation has been implicated as a cause of acquired resistance to BRAF inhibitors. Two vemurafenib refractory were treated with the potent BRAF inhibitor, vemurafenib, and the pan-class I PI3K inhibitor BKM120. Methods: The study enrolled BRAF-V600E/K mutant metastatic melanoma patients with an ECOG PS ≥ 2 and adequate organ function. Vemurafenib refractory BRAF-V600E/K mutant melanoma patients started both vemurafenib twice daily and BKM120 daily on cycle 1, day 1 after a vemurafenib washout of at least 14 days. Serial biopsies prior to treatment, on cycle 1 day 15, and at progression were obtained for pharmacodynamics analysis in patients with visible or palpable tumors. Results: 3 BRAF inhibitor refractory patients were treated on study with vemurafenib 720 mg PO bid and BKM120 60 mg PO daily. One patient was inevaluable due to non-compliance and had minimal exposure to study drug. Pre-treatment biopsy specimens were available in the remaining 2 vemurafenib-refractory patients. Both patient expressed PTEN at baseline and had demonstrable pAKT and pS6 staining. One patient had a mixed response to treatment with a 35.9% reduction in target lesions and two new small subcutaneous lesions. This patient also developed dose limiting febrile neutropenia on trial. The second patient tolerated treatment well but had widespread disease progression at 8 weeks. Conclusions: Combination therapy with vemurafenib and BKM120 in BRAF-V600E/K mutant melanoma led to substantial regression of several tumors in a PTEN+ patient with prior disease progression on vemurafenib alone. A phase I dose escalation trial in ongoing. Clinical trial information: NCT01512251.