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3548 Background: Panitumumab is a fully human monoclonal antibody directed against EGFr. We investigated panitumumab antitumor activity in pts who failed prior therapy and had EGFr tumor expression levels ≥ 10%. Methods: In this multicenter, phase 2 study of 300 planned pts, pts had documentation of disease progression (PD) during or following adequate doses of fluoropyrimidine, irinotecan, and oxaliplatin (centrally confirmed refractory disease CCRD), 2–3 prior regimens, ECOG score 0–2, and EGFr staining (by IHC) in ≥ 10% of evaluable tumor cells. Pts received panitumumab at 6 mg/kg Q2W until PD. Tumor assessments (modified WHO, blinded central review) were taken periodically from wk 8–48 until PD. Study endpoints were objective response rate (ORR) at wk 16 (+ ≥ 4 wk confirmation; primary) and ORR throughout study, response duration, progression-free survival (PFS) time, survival time, and safety (secondary). Results: In this interim analysis (5/05), 91 enrolled pts received ≥ 1 dose of panitumumab (safety set); 39 had ≥ 20 wks before the cutoff and CCRD (efficacy set). The efficacy set consisted of 23M/16W, mean (SD) age of 58.6 (10.1) years, 82% white, 95% ECOG ≤ 1, 74% colon cancer and 26% rectal cancer; all had ≥ 2 prior regimens (equivalent characteristics for safety set). At wk 16, 3 (8%) had a partial response, 8 (21%) had stable disease, and 19 (49%) had PD as best OR (9 not done/unevaluable). At the time of this interim analysis, response durations were 12.4, 13.2, and 14.0 wks. In the safety set, 96% had at least 1 treatment-related adverse event (24% grade gr 3, 1% gr 4, 1% gr 5). Integument and eye toxicities were: 96% skin, 30% nail, 8% eye, 5% hair, and 7% chelitis. 25 (27%) had diarrhea (3 gr 3); 11 (12%) had hypomagnesemia (3 gr 3/4). One pt had a gr 3 hypersensitivity reaction considered related to panitumumab, received medication, and the event resolved; this pt continued treatment with premedication; no further reactions occurred. In 66 pts with both a baseline and postdose sample, no human anti-human antibodies to panitumumab were detected.Additional data will be presented. Conclusions: Panitumumab has antitumor activity and is well tolerated in pts with EGFr tumor expression levels ≥ 10% who failed standard chemotherapy. Table: see text
Berlin et al. (Tue,) studied this question.