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Amgen, Abgenix Drug Charts Lone-Wolf Route

Their colorectal cancer drug could shrink tumors on its own.

While many drugs presented at this year's American Society of Clinical Oncology meeting are being proposed for use in combination with other treatments, an experimental cancer drug from






may actually shrink tumors all on its own.

According to trial results presented Tuesday at the ASCO annual meeting in Orlando, Fla., panitumumab, administered as a monotherapy in patients with metastatic colorectal cancer, showed evidence of antitumor activity after standard chemotherapy was unsuccessful. The study involved patients with late-stage disease, where multiple types of chemotherapy weren't effective.

Of patients with metastatic colorectal cancer tumors, expressing the epidermal growth-factor receptor protein, who received the drug, disease stabilization was observed in 29% of patients. Median progression-free survival time was 13.6 weeks, and overall survival time was 37.6 weeks in patients who took the drug.




Erbitux, an EGFR-targeted monoclonal antibody, is made up of human-mouse hybrid cells, panitumumab is made of fully human cells. Using Abgenix's XenoMouse technology, panitumumab is created in mice but doesn't contain mouse proteins.

Some researchers say panitumumab has a modestly superior safety profile compared with Erbitux, which may cause allergic reactions when the body rejects mouse proteins as foreign. One out of the 150 patients in the panitumumab trial experienced an infusion response, characterized by hypertension. The patient was pretreated with intravenous Benadryl and allowed to continue infusions of panitumumab.

A skin rash was observed as a side effect in 95% of patients. The skin rash occurred in proportion with the exposure to the drug and was possibly a sign that the drug was working, according to Dr. Imtiaz Malik, lead investigator in the trial.

The colorectal cancer trial is ongoing, but final results are expected in a matter of weeks, Amgen says. Researchers are also conducting studies to determine optimal dosing schedules.

Panitumumab is also in trials combining the drug with



Avastin and one of two chemotherapies, either Eloxatin (oxaliplatin), made by



, or Camptosar from