Clinical activity, safety, and biomarkers of MPDL3280A, an engineered PD-L1 antibody in patients with locally advanced or metastatic CRC, gastric cancer (GC), SCCHN, or other tumors.

3622 Background: PD-L1 has been reported to be expressed broadly in human cancer and can lead to inhibition of anti-tumor T-cell responses. MPDL3280A, a human monoclonal antibody containing an engineered Fc-domain designed to optimize efficacy and safety, targets PD-L1, blocking PD-L1 from binding its receptors, including PD-1 and B7.1. Pts with a broad range of tumors were examined in an expansion study with MPDL3280A. Methods: Pts with locally advanced or metastatic tumors received MPDL3280A administered IV q3w. Pts were treated for up to 1 y. Response was assessed by RECIST v1.1. Results: As of Jan 10, 2013, 20 pts with tumor types other than NSCLC, RCC and mM were evaluable for safety and treated at doses of 0.01-20 mg/kg (≤1 [n=3], 3 [n=1], 10 [n=3] and 20 mg/kg [n=13]). Median pt age was 67 y (range 26-80 y), 100% were PS 0-1, 90% had prior surgery and 45% had prior radiotherapy. 95% of pts received prior systemic therapy. Pts received MPDL3280A treatment for a median of 96 days (range 22-330). The incidence of all G3/4 AEs, regardless of attribution, was 50%. No G3-5 pneumonitis or diarrhea was reported. Confirmed RECIST responses were observed in several tumor types, including CRC, GC and SCCHN. Additionally, antitumor activity (tumor shrinkage that has not yet met criteria for a RECIST response) has been observed in sarcoma and lymphoma. Analysis of biomarker data from archival tumors revealed that all pts reported to have RECIST response had baseline tumors that were PD-L1 positive. Updated data will be presented. Conclusions: Treatment with MPDL3280A was well tolerated, with no pneumonitis-related deaths. Rapid responses were observed in pts with CRC, GC and SCCHN. PD-L1 tumor status appears to correlate with responses to MPDL3280A. These data suggest that PD-L1 is a conserved mechanism for mediating tumor immune escape across a range of tumor types. MPDL3280A may be broadly active as anti-cancer therapy in PD-L1–expressing tumors, supporting further investigation. Clinical trial information: NCT01375842.