A colorectal cancer drug developed by Amgen and partner Abgenix has exceeded expectations in Phase III trial, reducing disease progression by 46% in a hard-to-treat population of patients who had failed first- and second-line treatment.

The reduction in progression-free survival seen with panitumumab - the first fully-human antibody to inhibit the epidermal growth factor receptor (EGFr) - exceeded the pre-specified endpoint for showing effectiveness in the study (a 33% improvement) by some margin, said the two companies. A secondary endpoint of tumour response rate, assessed using radiology, was also met.

There was no data yet on overall patient survival said Amgen and Abgenix, as this analysis will take place 12 months after the last patient was randomised.

If approved, panitumumab will compete with another EGFr-blocking antibody, Erbitux (cetuximab), developed by Bristol-Myers Squibb and ImClone and German firm Merck KGaA. Erbitux is also approved as a third-line therapy, so the success of panitumumab in the marketplace could hinge on price in the first instance.

Erbitux is priced at around $4,200 per month, according to analysts at Lehman Brothers, who believe panitumumab will be pitched as early as possible at second-line therapy, which may require a lower dose and so carry a lower monthly cost.

As a third-line treatment panitumumab could find it hard to catch up with Erbitux, which reported third-quarter sales of $107 million for B-MS and 59 million euros for Merck [[31/10/05b]] [[25/10/05f]].

Lehman Brothers suggest that panitumumab would have peak annual turnover of $220 million as third-line treatment but could rake in as much as $900 million as first- or second-line therapy for colorectal cancer. Meanwhile, B-MS, Merck and ImClone are also pursuing approval for Erbitux in earlier-stage colorectal cancer patients, with Phase III trials ongoing.

Amgen and Abgenix won US fast-track approval for panitumumab for the treatment patients with advanced colorectal cancer who have failed on standard chemotherapy in August [[03/08/05f]]. Amgen and Abgenix say they are working towards initiating the submission of the Biologics License Application to the FDA for the product in patients who have failed prior standard chemotherapy, including oxaliplatin and irinotecan, by the end of 2005. The completed submission of the BLA is expected in the first quarter of 2006.