COMBI-MB: A phase II study of combination dabrafenib (D) and trametinib (T) in patients (pts) with BRAF V600–mutant (mut) melanoma brain metastases (MBM).

Abstract

9506 Background: CNS metastases are common and associated with very poor prognosis in pts with metastatic melanoma (MM). In the phase II BREAK-MB trial, D had clinical activity in BRAF V600–mut MBM. D + T has shown superiority over D alone in pts with BRAF V600–mut mm without MBM; however, efficacy of this regimen on MBM has not been characterized. Here, we report results from a phase II trial of D + T in BRAFV600–mut MBM (COMBI-MB; NCT02039947). Methods: This open-label, phase II study evaluated D 150 mg BID + T 2 mg QD in 4 MBM cohorts: (A) BRAFV600E, asymptomatic MBM, no prior local treatment (Tx); (B) BRAFV600E, asymptomatic MBM, prior local Tx; (C) BRAFV600D/K/R, asymptomatic MBM, with or without prior local Tx; and (D) BRAFV600D/E/K/R, symptomatic MBM, with or without prior local Tx. The primary objective was intracranial response rate (IRR) in cohort A (null hypothesis, IRR ≤ 35%). Secondary endpoints included IRR in cohorts B, C, and D; extracranial (ERR) and overall (ORR) response rates; intracranial (IDCR), extracranial (EDCR), and overall (ODCR) disease control rates; duration of IR, ER, and OR; PFS; OS; and safety. Results: 125 pts were enrolled (A, n = 76; B, n = 16; C, n = 16; D, n = 17). In cohort A, median age was 52, 53% were male, and 37% had LDH > ULN. At data cutoff (28 Nov 2016; median f/u, 9.0 mo), in cohort A, investigator-assessed IRR was 58% (IDCR, 78%), ERR was 55% (EDCR, 80%), and ORR was 58% (ODCR, 80%). Median duration of IR, ER, and OR was 6.5 mo (95% CI, 4.9-10.3), 10.2 mo (95% CI, 6.5-13.0), and 6.5 mo (95% CI, 4.9-10.3), respectively. Median PFS was 5.6 mo (95% CI, 5.3-7.4). Independent review supported these results. 6-mo OS was 79%; with 31 pts (41%) still in f/u, preliminary median OS was 10.8 mo (95% CI, 8.7-19.6). Efficacy in cohorts B, C, and D will be reported. AEs across cohorts (any, 98%; grade 3/4, 48%) were consistent with prior D + T studies; 10% of pts (8% in cohort A) discontinued due to AEs. Conclusions: In this first report of a phase II trial evaluating a BRAF and MEK inhibitor combination in BRAFV600–mut MBM, the primary endpoint was met. Promising IRR and IDCR were seen with D + T, but responses appear less durable than reported for mm without MBMs. No unexpected safety issues were observed. Clinical trial information: NCT02039947.