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Background: DUR is a human IgG1 monoclonal antibody (mAb) that blocks PD-L1. TRE is a human IgG2 mAb inhibitor of CTLA-4. Blocking these checkpoints can result in antitumor activity in some solid tumors. The targets for DUR and TRE are non-redundant, providing sound rationale for clinical testing of the combination.
Methods: This is an ongoing Phase 1, multicenter, open label study (NCT01975831) with a dose escalation (3+3 design) and subsequent expansion phase. Patients (pts) with renal cell carcinoma (RCC), cervical (CC), colorectal (CRC), non-triple-negative breast (NTNBC), ovarian (OC), non-small cell lung, or head and neck cancer are eligible. Primary endpoints are safety/tolerability and identification of maximum tolerated dose (MTD) of the combination. Secondary objectives include tumor response and progression-free/overall survival.
Results: As of 16 Dec 2016, 105 pts were treated. DUR 1500 mg every 4 weeks (Q4W) and TRE 75 mg Q4W X 4 was the regimen used for opening the expansion phase. Dose-limiting toxicities were reported in 4 pts: diarrhea, colitis, abnormal liver function tests (abn LFTs), and hyponatremia. The majority of treatment-related AEs (TRAEs) were Grades (Gr) 1 and 2. TRAEs ≥ Gr 3 were reported in 12 pts; the majority were diarrhea/colitis (n = 5) and abn LFTs (n = 4) and responded to established treatment algorithms. There was 1 Gr 5 TRAE: multi organ failure. No new toxicities were identified. The preliminary responses by tumor type with n ≥ 10 pts are shown in the table below. Responses were seen in OC and RCC at the Cohort 2 dose escalation level (DUR 1/TRE 3 mg/kg). There were 4 cases of SD > 24 weeks: CC, n=2; CRC, n=1; OC, n=1. PD-L1 status was not tested.
Conclusions: The DUR + TRE combination has a manageable safety profile, with preliminary evidence of clinical activity. These data support continued study of the combination therapy; the study is ongoing.
Margaret K Callahan