A study of MPDL3280A, an engineered PD-L1 antibody in patients with locally advanced or metastatic tumors.

3000 Background: Tumor PD-L1 mediates cancer immune evasion. Therefore, inhibition of PD-L1 binding represents an attractive strategy to restore tumor-specific T-cell immunity.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. Methods: A study was conducted with MPDL3280A administered IV q3w in pts with locally advanced or metastatic solid tumors, including 3+3 dose-escalation and expansion cohorts. ORR was assessed by RECIST v1.1 and includes u/cCR and u/cPR. Results: As of Jan 10, 2013, 171 pts were evaluable for safety. Administered doses include ≤1 (n=9), 3 (n=3), 10 (n=35), 15 (n=57) and 20 mg/kg (n=67). Pts in the dose-escalation cohorts did not experience DLTs. No MTD was identified. Pts had received MPDL3280A for a median duration of 127 days (range 1-330). 39% of pts reported G3/4 AEs, regardless of attribution. AEs of special interest included hepatitis, rash and colitis. No G3-5 pneumonitis was observed. MPDL3280A PK was linear at doses ≥1 mg/kg. 122 pts enrolled prior to Jul 1, 2012 were evaluable for efficacy. RECIST responses were observed in multiple tumor types including NSCLC, RCC, melanoma, CRC and gastric cancer. An ORR of 21% (25/122) was observed in nonselected solid tumors, including several pts who demonstrated tumor shrinkage within days of initiating treatment. Additional pts had delayed responses after apparent radiographic progression (not included in the ORR). Some responders demonstrated prolonged SD prior to RECIST responses. The 24-week PFS was 44%. Pts with PD-L1–positive tumors (from archival samples) showed an ORR of 39% (13/33) and a PD rate of 12% (4/33). In contrast, patients with PD-L1–negative tumors showed an ORR of 13% (8/61) and a PD rate of 59% (36/61). As of the cutoff date, all responses are ongoing or improving. Updated data will be presented. Conclusions: MPDL3280A was well tolerated, with no pneumonitis-related deaths. Durable responses were observed in a variety of tumors. PD-L1 tumor status appears to correlate with responses to MPDL3280A. PK supports q3w dosing at 15 mg/kg or fixed-dose equivalent. Clinical trial information: NCT01375842.