Triplet combination treatments with pembrolizumab (pembro) for anti–PD-(L)1–refractory advanced melanoma: Preliminary results of the phase 1/2 KEYMAKER-U02A study.

9506 Background: Anti–PD-(L)1–refractory melanoma is a major challenge, and immunotherapy combination treatment may be useful in this patient population. The phase 1/2 KEYMAKER-U02A (NCT04305041) is a multi-arm, open-label, adaptive umbrella study designed to evaluate pembro + investigational agents for the treatment of anti–PD-(L)1–refractory melanoma. We report results from arm 1 (pembro + quavonlimab qmab (anti-CTLA4) + vibostolimab vibo (anti-TIGIT)), arm 2 pembro + qmab + lenvatinib [len (TKI)), and arm 3 (pembro + ATRA all-trans retinoic acid) of KEYMAKER-U02A. Methods: In all arms, adults had stage III/IV melanoma, ≥1 measurable lesion per RECIST v1.1, an Eastern Cooperative Oncology Group performance status score of 0 or 1, and disease progression on anti–PD-(L)1 therapy alone or in combination. Pts were randomized equally to open arms. In arm 1, pts received pembro 200 mg IV Q3W + qmab 25 mg IV Q6W + vibo 200 mg IV Q3W. In arm 2, pts received pembro 400 mg IV Q6W + qmab 25 mg IV Q6W + len 20 mg PO QD. In arm 3, pts received pembro 400 mg IV Q6W + ATRA 150 mg/m 2 /day PO for 3 days Q3W. Pts received treatment for up to 2 y or until intolerable toxicity, disease progression, or pt withdrawal. Primary end points were safety and ORR per RECIST v1.1 by blinded independent central review (BICR). DOR per RECIST v1.1 by BICR was the secondary end point. PFS per RECIST v1.1 by BICR and OS were exploratory end points. Enrollment was planned for a maximum of 20 pts in each arm and enrollment could continue to up to 40 pts if an ORR of > 20% (5/20) was observed. Enrollment would then continue up to 100 pts if an ORR of ≥35% (14/40) was observed. Results: At data cutoff (Oct 18, 2022), 40 pts had been assigned to arms 1 and 2 and 20 pts to arm 3. Median (range) follow-up was 18.4 (1.7-24.5) mo in arm 1, 18.5 mo (1.6-25.4) in arm 2, and 2.7 mo (0.8-3.5) in arm 3. Efficacy is reported in the table. Treatment-related adverse events (TRAEs) occurred in 35 pts (88%) in arm 1, 38 pts (95%) in arm 2, and 15 pts (75%) in arm 3. Grade 3-5 TRAEs occurred in 11 pts (28%) in arm 1, 23 pts (58%) in arm 2, and 3 pts (15%) in arm 3; 1 pt in arm 2 died from a grade 5 TRAE (immune-mediated nephritis). Conclusions: Although objective responses were observed in some pts with anti–PD-(L)1–refractory melanoma, protocol-prespecified criteria for enrollment expansion were not met in any arm. The safety profile was manageable. Additional arms will be reported for this pt population with a high unmet need. Clinical trial information: NCT04305041 . Table: see text