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A phase Ia study of MPDL3280A (anti-PDL1): Updated response and survival data in urothelial bladder cancer (UBC).
Background: PD-L1 may contribute to immune escape in UBC, a disease of high mutational complexity and immunogenicity. MPDL3280A was designed to restore T cell–mediated antitumor activity by blocking PD-L1 binding to PD-1 and B7.1 receptors. Methods: Previously treated, metastatic UBC pts were enrolled in an expansion cohort and received 15 mg/kg or 1200 mg IV MPDL3280A q3w. Efficacy-evaluable pts had ≥ 12 wk of follow-up (dosed by Jun 9, 2014; Sep 2, 2014 cutoff). ORR was assessed by RECIST v1.1 (unconfirmed), and archival biopsies were centrally evaluated for PD-L1 tumor-infiltrating immune cell (IC) expression by IHC. In-tumor gene expression and peripheral biomarkers were assessed as exploratory analyses in a subset of pts. Results: Updated analyses include 85 efficacy-evaluable, selectively enrolled UBC pts; 46 were PD-L1 IHC 2/3, 38 were IHC 0/1 and 1 had unknown IHC status. Median age was 66 y (36-89 y), and 75% were male. Baseline visceral mets were present in 77% of pts; 98% received ≥ 1 prior therapy (eg platinum in 93%). The ORR for IHC 2/3 pts was 46% (95% CI 31-61%; 6 CRs, 15 PRs), and for IHC 0/1 pts was 16% (95% CI 6-31%; 6 PRs) with median response durations not yet reached (IHC 2/3 pts, 0+ to 54+ wk; IHC 0/1 pts, 4+ to 33+ wk). Median PFS was 24 wk (95% CI 12-NE) for IHC 2/3 pts and 8 wk (95% CI 6-12 wk) for IHC 0/1 pts. 24-wk OS rates for IHC 2/3 and 0/1 pts were 85% (95% CI 74-96%) and 71% (95% CI 54-88%), respectively, with the medians not yet reached (3 to 72+ wk and 2+ to 51+ wk, respectively). Pts with visceral mets had ORRs of 32% (IHC 2/3: 3 CRs, 7 PRs; n = 31) and 12% (IHC 0/1: 4 PRs; n = 33). Median safety follow-up was 16 wk (3-73 wk). Drug-related AEs occurred in 64% of 87 safety-evaluable pts (most often fatigue, asthenia, nausea); 8% had a related G3-4 AE. 12% of pts had an immune-related AE. No related deaths were seen. Responders had lower myeloid gene expression at baseline (eg Cox-2, IL8; IL1B) and decreased circulating inflammatory and tumor markers (eg CRP; HCG, CA 19-9, CA-125) by cycle 2. Conclusions: MPDL3280A was well tolerated and had durable activity in UBC pts. Response, PFS and OS data are promising for IHC 2/3 and IHC 0/1 UBC pts vs historic controls. Response also correlated with in-tumor and blood-based biomarkers. Clinical trial information: NCT01375842
Abstracts by Daniel Peter Petrylak:
A multicohort phase I study of ramucirumab (R) plus pembrolizumab (P): Interim safety and clinical activity in patients with urothelial carcinoma.Meeting: 2017 Genitourinary Cancers Symposium | Abstract No: 349
Antigen spread (AgS) after sipuleucel-T (sip-T): A cross-trial comparison of 4 sip-T clinical trials of patients (pts) with prostate cancer (PC).Meeting: 2017 Genitourinary Cancers Symposium | Abstract No: 143
Atezolizumab (atezo) in patients with metastatic urothelial carcinoma (mUC): A 2-year clinical update from a phase Ia study.Meeting: 2017 Genitourinary Cancers Symposium | Abstract No: 290