Amgen announces promising interim colorectal cancer data

Panitumumab is an investigational fully human monoclonal antibody that targets the epidermal growth factor receptor (EGFr). Results from both studies suggest that the antitumor activity of panitumumab was independent of tumor EGFr expression levels in patients with metastatic colorectal cancer who have failed standard chemotherapy.

The first study, known as the 250 study, examined metastatic colorectal cancer patients with either low or negative (less than 1% positive cells) levels of tumor EGFr staining, while the second, the 167 study, evaluated patients with tumor EGFr levels of at least 10%. Both ongoing multicenter, open-label, phase II trials are examining the antitumor activity of panitumumab in patients who have failed standard chemotherapy, including oxaliplatin and irinotecan.

Patients in both studies receive panitumumab at 6mg/kg every two weeks until disease progression or drug intolerability. Tumor assessments are conducted by an independent central radiological review board from week eight until disease progression. The primary study endpoint is objective response at week 16 and secondary endpoints include objective response rate throughout study, duration of response, progression-free survival, overall survival, and safety.

At the time of the interim analysis, the 250 study had enrolled 88 patients, with 23 evaluable for response. Data show that 13% of those who received panitumumab monotherapy had a partial response, including two patients with tumor cells negative for EGFr staining. Stable disease was observed in 30% of patients. The median progression-free survival time was 13.3 weeks.

Study 167 had enrolled 91 patients, and 39 were evaluable for response at the time of interim analysis. At week 16, 8% of patients demonstrated a partial response, 21% had stable disease and 49% had disease progression. The median progression-free survival time was 7.6 weeks.