Genentech's Avastin: An "Eye Opening" Disclosure?

Thursday, 1 Nov 2007 | 9:44 AM ET

Yet another chapter in the unfolding saga of Genentech's Avastin being used instead of Lucentis to treat age-related macular degeneration (AMD).

The other day I blogged about the new "Open Letter" on the company's homepage announcing that it's delaying the implementation of its attempted crackdown on the cheaper, similar cancer drug (Avastin) being used instead of the much more expensive eye drug (Lucentis) for the leading cause of adult-onset blindness.

Well, yesterday Genentech updated the letter with a thick paragraph detailing the molecular differences between Avastin and Lucentis. I wonder if the legal or the marketing department--or both--were behind the addition. Yes, it's pretty dense subject matter for the layman (you might need to read it a couple of times), but I think it reveals some interesting information that, as far as I know, hasn't been laid out like this before. Here's the new graf:

"While we can't be certain of the precise effects of any of the differences between Lucentis and Avastin, it is important to emphasize that Lucentis is purposefully different in fundamental ways from Avastin. While both drugs target and inactivate VEGF (Vascular Endothelial Growth Factor), Lucentis was engineered from the outset, because of the proposed limited space available within the eye, to bind more tightly to its target. (In fact, it binds more than ten-fold more tightly than does Avastin.) To reduce the theoretical possibility of increased inflammation in the eye, the apparent pro-inflammatory components of the antibody, present within Avastin, were removed. Finally, to facilitate the movement and distribution of Lucentis throughout the eye, and to reduce its time of circulation in the serum (where one seeks to minimize the drug's concentration, relative to the eye), the size of the molecule was reduced by more than 65 percent; this change results in a reduction of serum half-life of more than 100-fold."

I'm not a lawyer, but my takeaway is that Genentech is possibly doing a little legal "CYA" spelling out that doctors and patients may be substituting one drug for the other at their own risk and it is trying to dispel the notion that the two drugs are essentially the same. That said, I doubt it will result in significantly less use of Avastin for Lucentis unless the company's new crackdown is successful. It's now set to take effect on New Year's Day.

Questions? Comments? Pharma@cnbc.com