Zarour, Hassane M.

LBA9000^ Background: The humanized monoclonal IgG4 anti-PD-1 antibody MK-3475 has demonstrated durable antitumor activity in MEL and NSCLC. We evaluated MK-3475 efficacy and safety in a pooled analysis of 411 MEL pts. Methods: A nonrandomized cohort of ipilimumab-naive (IPI-N) and IPI-treated (IPI-T) pts treated with MK-3475 10 mg/kg Q2W, 10 mg/kg Q3W, or 2 mg/kg Q3W and randomized cohorts of IPI-N and IPI-T pts treated with 2 Q3W or 10 Q3W were included. Response was assessed every 12 wk by RECIST 1.1 by independent central review and by immune-related response criteria (irRC) by investigator. Results: 162 pts were treated at 2 Q3W, 192 at 10 Q3W, and 57 at 10 Q2W. 190 pts were IPI-N and 221 were IPI-T. As of the 10/18/2013 cutoff, all pts had ≥6 mo follow-up and >75% had ≥9 mo follow-up. Among the 365 pts with measurable disease at baseline, ORR by RECIST was 40% (95% CI 32%-48%) in IPI-N and 28% (95% CI 22%-35%) in IPI-T pts. Responses were durable (88% ongoing at analysis). Median PFS by RECIST was 24 wk in IPI-N and 23 wk in IPI-T pts. Median OS was not reached, with 1-y OS of 71% in all pts. Benefit was observed by both RECIST and irRC at all doses and schedules in IPI-N and IPI-T pts (Table). MK-3475 demonstrated activity in all major subgroups irrespective of ECOG PS, LDH levels, BRAFmutation, M stage, and number and type of prior therapy. Overall, 12% of pts experienced drug-related grade 3/4 AEs and 4% discontinued due to a drug-related AE. There were no drug-related deaths. Conclusions: MK-3475 showed durable responses and a manageable safety profile across dose and schedules in IPI-N and IPI-T MEL pts. The observed efficacy and safety suggest MK-3475 may be an appropriate treatment for all pts with MEL. Clinical trial information: NCT01295827. [Table: see text]

Abstract Background: Previous data on the relationship between PD-L1 expression and activity of anti-PD-1 and anti-PD-L1 antibodies have been conflicting. MK-3475, a humanized monoclonal IgG4 antibody against PD-1, has demonstrated durable antitumor activity in MEL and NSCLC. We evaluated tumor PD-L1 expression and its relationship with outcomes in a phase I clinical trial of MK-3475. We also evaluated T cell activation as a pharmacodynamic marker of MK-3475 activity. Methods: 135 MEL pts received MK-3475 10 mg/kg Q2W, 10 mg/kg Q3W, or 2 mg/kg Q3W. Tumor response was assessed by RECIST 1.1 per independent central review, including requirement for a confirmatory CT scan. Pretreatment biopsy was required. Serial blood samples were collected before infusion at the start of cycles 1-5 (Q2W dosing) or 1-4 (Q3W dosing). Tumor PD-L1 expression was assessed by IHC. A preliminary cutoff of 1% of stained cells was used to define PD-L1 positivity. Absolute CD4+ and CD8+ T cell counts and the percentage of activated (HLA-DR as marker) CD4+ and CD8+ T cells in peripheral blood were assessed by multiplex flow cytometry (n = 101). Results: Median PFS was 36 weeks, 6-month overall survival (OS) rate was 89%, and 12-month OS rate was 81%. Median duration of response and OS were not reached. In the 116 pts with measurable disease, ORR was 41%. PFS and response rate were significantly associated with tumor PD-L1 expression (Table). At week 6, a statistically significant percent increase from baseline in the percentage of activated (HLA-DR+) CD4+ and CD8+ T cells was observed at all doses (pooled mean percent change [SE], +24.0% [4.7%] for HLA-DR+/CD8+, +17.5% [2.7%] for HLA-DR+/CD4+). Conclusions: Tumor PD-L1 expression levels were associated with tumor response and PFS in MEL pts treated with MK-3475; activity was also observed in pts with low PD-L1 expression. As assessed by HLA-DR expression, post-treatment T cell activation in the circulating pool was increased at all doses tested. Patients WithMeasurable Disease and Interpretable PD-L1 IHC ResultsPatients With InterpretablePD-L1 IHC Results and PFS and OS Data PD-L1 TumorExpressionNORR, n (%)NPFS at 6 months, % (95% CI)Median PFSOS at 6 months, % (95% CI)Median OSPositive (membrane staining in ≥1% of cells)5529 (53)6058 (47-72)10.6 mo93(87-100)Not reachedNegative (membrane staining in <1% of cells)161* (6)2232 (16-64)2.9 mo75(58-97)Not reachedHR (95% CI) for PD-L1-positive vs negative____0.54(0.28-1.05)_0.67(0.25-1.83)One-sidedP value(PD-L1 association test)_<0.004 (logistic regression)__0.034(Cox regression)_0.220(Cox regression)*IPI-pretreated patient who received MK-3475 10 mg/kg Q2W. Citation Format: Adil I. Daud, Omid Hamid, Antoni Ribas, F. Stephen Hodi, Wen-Jen Hwu, Richard Kefford, Jedd Wolchok, Peter Hersey, Jeffrey S. Weber, Richard Joseph, Tara C. Gangadhar, Roxana S. Dronca, Amita Patnaik, Hassane Zarour, Anthony M. Joshua, Kevin Gergich, Dianna Wu, Jared K. Lunceford, Kenneth Emancipator, Marisa Dolled-Filhart, Nicole Li, Scot Ebbinghaus, S. Peter Kang, Caroline Robert. Antitumor activity of the anti-PD-1 monoclonal antibody MK-3475 in melanoma(MEL): Correlation of tumor PD-L1 expression with outcome. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT104. doi:10.1158/1538-7445.AM2014-CT104