BackgroundIn the KEYNOTE-022 study, pembrolizumab with dabrafenib and trametinib (triplet) improved progression-free survival (PFS) versus placebo with dabrafenib and trametinib (doublet) without reaching statistical significance. Mature results on PFS, duration of response (DOR), and overall survival (OS) are reported.MethodsThe double-blind, phase 2 part of KEYNOTE-022 enrolled patients with previously untreated BRAFV600E/K-mutated advanced melanoma from 22 sites in seven countries. Patients were randomly assigned 1:1 to intravenous pembrolizumab (200 mg every 3 weeks) or placebo plus dabrafenib (150 mg orally two times per day) and trametinib (2 mg orally one time a day). Primary endpoint was PFS. Secondary endpoints were objective response rate, DOR, and OS. Efficacy was assessed in the intention-to-treat population, and safety was assessed in all patients who received at least one dose of study drug. This analysis was not specified in the protocol.ResultsBetween November 30, 2015 and April 24, 2017, 120 patients were randomly assigned to triplet (n=60) or doublet (n=60) therapy. With 36.6 months of follow-up, median PFS was 16.9 months (95% CI 11.3 to 27.9) with triplet and 10.7 months (95% CI 7.2 to 16.8) with doublet (HR 0.53; 95% CI 0.34 to 0.83). With triplet and doublet, respectively, PFS at 24 months was 41.0% (95% CI 27.4% to 54.2%) and 16.3% (95% CI 8.1% to 27.1%); median DOR was 25.1 months (95% CI 14.1 to not reached) and 12.1 months (95% CI 6.0 to 15.7), respectively. Median OS was not reached with triplet and was 26.3 months with doublet (HR 0.64; 95% CI 0.38 to 1.06). With triplet and doublet, respectively, OS at 24 months was 63.0% (95% CI 49.4% to 73.9%) and 51.7% (95% CI 38.4% to 63.4%). Grade 3–5 treatment-related adverse events (TRAEs) occurred in 35 patients (58%, including one death) receiving triplet and 15 patients (25%) receiving doublet.ConclusionIn BRAFV600E/K-mutant advanced melanoma, pembrolizumab plus dabrafenib and trametinib substantially improved PFS, DOR, and OS with a higher incidence of TRAEs. Interpretation of these results is limited by the post hoc nature of the analysis.

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9516 Background: KEYNOTE-022 (NCT02130466) was a phase 1/2 study of pembro + dab + tram or pembro + tram in patients (pts) with unresectable stage III/IV melanoma (parts 1-3) or solid tumors (parts 4 and 5). In previous analyses of pts with BRAFV600E/K -mutant melanoma, pembro + dab + tram was shown to have manageable safety in parts 1-3, albeit with a higher incidence of TRAEs in part 3, and substantially improved PFS, DOR, and OS vs placebo + dab + tram in part 3, although the primary end point of a statistically significant improvement in PFS was not met. Long-term follow-up of pts with BRAFV600E/K-mutant melanoma in parts 1-3 are presented. Methods: Eligible pts were ≥18 y with unresectable stage III/IV BRAFV600E/K-mutant melanoma, ≥1 measurable lesion per RECIST v1.1, ECOG PS 0/1, and no prior systemic therapy for advanced disease. In parts 1 and 2, which involved dose finding and confirmation, pts received pembro 2 mg/kg IV Q3W + dab 150 mg PO BID + tram 2 mg PO QD (MTD). In part 3, pts were randomized 1:1 to pembro + dab + tram at MTD or placebo + dab + tram. Primary end points were safety, tolerability, and MTD (parts 1 and 2); ORR per RECIST v1.1 by investigator review (part 2); and PFS per RECIST v1.1 by investigator review (part 3). Data cutoff was July 14, 2021. Results: Median (range) study follow-up was 72.9 mo (68.4-84.5) in parts 1 and 2 (n = 15) and 61.2 mo (50.7-67.5) for all pts (n = 120; 60 each arm) in part 3. Safety of pembro + dab + tram in parts 1 and 2 was consistent with prior reports; grade 3/4 TRAEs occurred in 11 pts (73%), and no additional DLTs occurred. ORR in parts 1 and 2 was 67% (95% CI, 38-88), which was similar to that reported at an earlier data cut (73% [95% CI, 45-92]); median DOR was 19.4 mo (95% CI, 2.8-NR), median OS was NR (95% CI, 10.3-NR), 48-mo OS rate was 60%, median PFS was 15.2 mo (95% CI, 4.2-NR), and 48-mo PFS rate was 28% (Ribas A et al. Nat Med. 2019;25:936-940). In part 3, median PFS was 17.0 mo (95% CI, 11.3-NR) for pembro + dab + tram vs 9.9 mo (95% CI, 6.7-15.6) for placebo + dab + tram (HR, 0.46; 95% CI, 0.29-0.74) and 24-mo PFS rate was 47% vs 16%, and median OS was 46.3 mo (95% CI, 23.9-NR) vs 26.3 mo (95% CI, 18.2-38.6); and 24-mo OS rate was 63% vs 52%, respectively. ORR was 65% (95% CI, 52-77) for pembro + dab + tram vs 72% (95% CI, 59-83) for placebo + dab + tram; median DOR was 30.2 mo (95% CI, 14.1-NR) vs 12.1 mo (95% CI, 6.0-15.7). Safety in part 3 was similar to prior reports; grade 3-5 TRAEs occurred in 42 pts (70%) in the pembro + dab + tram arm vs 27 pts (45%) in the placebo + dab + tram arm (Ferrucci PF et al. J Immunother Cancer. 2020;8:e001806). No additional grade 5 TRAEs occurred (1 grade 5 pneumonitis had occurred at prior analysis). Conclusions: At long-term follow-up, first-line pembro + dab + tram continued to show improved PFS, DOR, and OS compared with placebo + dab + tram in pts with BRAFV600E/K-mutant melanoma. TRAEs were more common with pembro + dab + tram but no new safety signals were identified. Clinical trial information: NCT02130466.

9500 Background: The phase 3 double-blind EORTC 1325/KEYNOTE-054 trial evaluated pembrolizumab (pembro) vs placebo in stage III cutaneous melanoma patients (pts) with complete resection of lymph nodes. Pembro improved RFS (hazard ratio [HR] 0.57) and DMFS (HR 0.60) (Eggermont, NEJM 2018, TLO 2021). In the pembro group, the incidence of immune related AE (irAE) grade 1-5 was 37%, and of grade 3-5 was 7%. We present the safety profile, response rate and PFS for the subset of pts who had a recurrence and crossed over or were rechallenged with pembrolizumab, within protocol. Methods: Pts were randomized to receive iv. pembro 200 mg (N=514) or placebo (N=505) every 3 weeks for a total of 18 doses (~1 year). Upon recurrence with no brain metastases, pts with an ECOG PS 0-2 were eligible to enter part 2 of the study, i.e. to receive pembro 200 mg iv. every 3 weeks for a maximum of 2 years, for crossover (those who received placebo) or rechallenge (those who recurred ≥6 months after completing one year of pembro therapy). Treatment was stopped in case of disease progression (RECIST 1.1) or unacceptable toxicity. Results: At the clinical cut-off (16-Oct-2020), 298 (59%) pts had a disease recurrence in the placebo group; 155 pts participated in the crossover part 2 of the trial. A total of 297 (58%) pts completed the 1-yr pembro adjuvant treatment, of whom 47 had a recurrence ≥6 mths from the stop of treatment and 20 entered in the rechallenge part of the trial. Among 175 pts who started pembro in Part 2, 160 discontinued due to completion of therapy (N=24), disease progression (N=88), toxicity (N=20), investigator's decision (N=21), or other reason (N=7); 15 pts were still on-treatment. Results for the 2 groups are provided in the table. The median number of doses was 12 and 5.5, respectively (resp), and the median follow-up was 41 and 19 mts, resp. Among the 175 pts, 51 (29%) had a grade 1-4 irAE (by group: 47 [30%] and 4 [20%] resp) and 11 (6%) a grade 3-4 irAE. Conclusions: Pembrolizumab treatment after crossover yielded a 39% ORR in evaluable pts and an overall 3-yr PFS of ̃32%, but after rechallenge the efficacy was lower. Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA The median PFS (95% CI) from start of Part 2 was 14 (5-27) and 8 (5-15) mts for stage III-resected and III/IV various, resp. Among the 80 stage IV crossover pts with evaluable disease, 31 (39%) had an objective response: 14 (18%) CR, 17 (21%) PR. The 2-yr PFS rate from response was 69% (95% CI 48-83%). For these 80 pts, the median PFS was 6.1 mts and the 3-yr PFS rate was 31% (95% CI 21-41%). Among 9 stage IV rechallenged pts with an evaluable disease, 1 (11%) reached CR, 3 had SD and 5 PD. Clinical trial information: NCT02362594. [Table: see text]