Safety of panitumumab, a fully human monoclonal antibody against the epidermal growth factor receptor (EGFr), in patients (pts) with metastatic colorectal cancer (mCRC) across clinical trials

Abstract

4138 Background: Panitumumab is indicated in pts with EGFr-expressing mCRC refractory to chemotherapy. We present a summary of safety with panitumumab monotherapy in mCRC pts across 10 clinical trials. Methods: Data were pooled from pts enrolled in 10 clinical trials (including 2 extension studies). Pts received at least 1 dose of panitumumab at 2.5 mg/kg QW, 6 mg/kg Q2W, or 9 mg/kg Q3W. Adverse events were graded using NCI-CTC or CTCAE criteria. Results: A total of 920 mCRC pts were included in this analysis: 60% were male; 88% were white; median age (range) was 61 (20, 88) years. All pts had prior therapy; 77% had failed prior fluoropyrimidine, irinotecan, and/or oxaliplatin. Most (80%) pts received panitumumab 6 mg/kg Q2W; 17% and 3% of pts received panitumumab 2.5 mg/kg QW and 9 mg/kg Q3W, respectively. Median (range) follow-up time was 21 (1–124) weeks. A total of 7264 panitumumab infusions were administered with a median (range) of 5 (1–94) infusions/pt. Treatment-related adverse events (AE) were experienced by 94% (grade = 3, 20%) of pts. All pts had = 1 AE. The most common AEs were skin-related and GI toxicities ( table ). Skin-related AEs resulted in discontinuation in 2% of pts. Overall, 12% of pts discontinued panitumumab due to toxicity. Four (0.4%) pts had grade = 3 infusion reactions. In pts with postdose samples (n = 613), increased and persistent postdose levels of anti-panitumumab antibodies were detected in 0.5% of pts by ELISA and in 4.6% of pts by Biacore assay. Conclusions: Skin toxicity was common, but rarely treatment-limiting. Most AEs were mild to moderate and infrequently resulted in discontinuation. Infusion reactions and formation of anti-panitumumab antibodies were rare. The safety profile of 9 mg/kg Q3W panitumumab appeared consistent with other dosages; however, because of the small pt size further evaluation is needed. Panitumumab at 2.5 mg/kg QW and 6 mg/kg Q2W was well tolerated across 10 clinical studies. [Table: see text] No significant financial relationships to disclose.