Panitumumab Data and the Implications for Erbitux (ABGX, AMGN, IMCL)

Last Thursday, Amgen (ticker: AMGN) and Abgenix (ticker: ABGX) released positive clinical results from the Phase 3 study of panitumumab in metastatic colorectal cancer.

The companies released top-line data that showed a statistically significant 46% reduction in tumor progression versus patients that received best supportive care. This result exceeded the pre-specified measure of 33%. Roger Perlmutter, EVP of R&D at Amgen stated on his company's conference call:

"I guess I should mention that we powered this study to see a 33% retardation in progression. Our study was so positive at the 46% level that we can actually exclude 33% below the lower bound. So our 95% confidence limits don't even include the therapeutic effect that we were testing were much better than that. And that was extremely gratifying to all of us who looked at this dataset. We were quite amazed."

(Quotes are from the CCBN StreetEvents transcript.)

In other words, the panitumumab data was a home run.

What does this mean for Imclone's (ticker: IMCL) Erbitux? Let's compare the characteristics of the two drugs.

Efficacy. Panitumumab has clinical data showing a strong survival benefit whereas Erbitux does not.

Safety. Panitumumab is associated with less injection site reactions than Erbitux.

Convenience. Panitumumab can be dosed once every two weeks versus once a week for Erbitux, which gives panitumumab the same dosing schedule as current chemotherapy regimens.

Cost. Dosing regimen with panitumumab requires less drug than Erbitux. Panitumumab is dosed at 6mg/kg once every two weeks whereas Erbitux requires a 400mg/m2 loading dose followed by 250mg/m2 every week. Assuming the average patient weighs 70kg and 1.8m2, the average weekly dose for panitumumab is about 210mg versus 484mg for Erbitux. As a result, Amgen/Abgenix can price panitumumab below Erbitux and still maintain a higher profit margin.

I don’t think it can be put any clearer – Erbitux is in big trouble.

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