The two currently available monoclonal antibodies being used to treat metastatic colorectal cancer, ImClone's Erbitux and Genentech's Avastin, operate very differently from one another with very different side-effects when halting progress of the disease once it has begun its spread throughout the body. And Erbitux is decidedly less onerous a treatment, making the Priority Review announcement from FDA especially important to potentially millions of cancer sufferers worldwide each year.

Erbitux slows cancer growth by targeting a protein found on the surface of some cells called the epidermal growth factor receptor while Avastin shuts down the process whereby tumors grow new blood vessels to help them receive the nutrients they need to survive and grow. But, only Avastin is currently approved by the FDA. Patients who received Avastin plus chemotherapy drugs (IFL) had an overall response rate of 39%, while the Erbitux studies showed a response rate of 21% without any chemotherapy drugs. Besides not having to go through chemo, the side effects of Erbitux are less alarming that Avastin. Erbitux has side effect like skin problems, fatigue and weakness, constipation and fever. However, Avastin, while it also has some more common and milder side effects such as those listed above, the treatment can also produce holes in the colon requiring surgical repair, heart failure, kidney damage, and the decreased ability to heal wounds.(read more)