Vectibix and irinotecan – pro

Lay Summary: Some important questions have been raised about the combination of irinotecan and panitumumab.

Vectibix is a recombinant, human IgG2 kappa monoclonal antibody that binds specifically to the human Epidermal Growth Factor Receptor (EGFR). Vectibix is specifically indicated for for the treatment of EGFR-expressing, metastatic colorectal carcinoma with disease progression on or following fluoropyrimidine-, oxaliplatin-, and irinotecan- containing chemotherapy regimens.

Vectibix™ treatment can cause diarrhea and, in combination with irinotecan, appears to increase the incidence and severity of chemotherapy-induced diarrhea. Amgen recently discontinued a trial due to toxicity, the phase IIIb Panitumumab Advanced Colorectal Cancer Evaluation (PACCE) trial is a disappointing setback. PACCE was evaluating the addition of Vectibix to a regimen of standard oxaliplatin- or irinotecan-based chemotherapy and bevacizumab. It was halted after preliminary review of data from a pre-planned interim efficacy analysis, scheduled after the first 231 events (death or disease progression), revealed a statistically significant difference in progression-free survival (PFS) and overall survival in favor of the control arm and higher toxicity in the Vectibix arm. Total enrollment of this trial had reached 1,054. Amgen is continuing phase III trials of Vectibix as a single biologic combined with chemotherapy as a first- or second-line treatment. No other clinical trials are being modified at this time, however, Amgen is evaluating data across all trials. Vectibix is approved as a third line treatment for metastatic, refractory CRC expressing EGFR. I was not able to find any trials on Vectibix and irinotecan.

Wainberg Z, Hecht JR Panitumumab in colon cancer: a review and summary of ongoing trials. Expert opinion on biological therapy. 2006 Nov;6(11):1229-35.

Saif MW, Cohenuram M Role of panitumumab in the management of metastatic colorectal cancer. Clinical Colorectal Cancer 2006 Jul;6(2):118-24

Gibson TB, Ranganathan A, Grothey A Randomized phase III trial results of panitumumab, a fully human anti-epidermal growth factor receptor monoclonal antibody, in metastatic colorectal cancer. Clinical colorectal cancer 2006 May;6(1):29-31.

Tyagi P Recent results and ongoing trials with panitumumab (ABX-EGF), a fully human anti-epidermal growth factor receptor antibody, in metastatic colorectal cancer Clinical colorectal cancer 2005 May;5(1):21-3.

Vectibix, prescribing information

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