Genentech's Rituxan Faces Stiff Competition

As you can imagine, injecting someone with mouse antibodies can cause some allergic reactions. HuMax doesn't appear to have the same issue because it is a fully human antibody, so the drug could be safer and have fewer side effects than Rituxan.

Again, Genentech's Benyunes emphasizes Rituxan's track record. One million patients have been treated with Rituxan over the past 10 years. "If you're a cancer patient and you have data that shows this could improve your survival and something else that says well, we don't know what the long-term effects are in survival, but it may slightly reduce the risk of side effects, you look at that differently," he said. "As a physician, I'm much more interested in a new agent that is going to improve survival." Benyunes added, "Unless the toxicity of a drug is really something I'm concerned about, I don't want to spend a lot of time trying to reduce adverse events."

Rituxan May Pave Way for HuMax

It's difficult to gauge just how an approval of HuMax will impact Rituxan revenue because Genentech doesn't break down sales between NHL and CLL. However, the current consensus estimate for Genmab's 2008 revenue is $425 million (with a high estimate of $700 million-plus), nearly all of that coming from HuMax.

One should assume that a nice chunk of HuMax's sales will come at the expense of Rituxan. It seems likely that Genentech could suffer a hit to its top line in 2008. But that kind of hit's not going to bankrupt the San Francisco-based drugmaker, which is expected to rake in nearly $13 billion in sales in 2008. If, however, phase III results turn out as positive as earlier trials, HuMax could eat into more of Rituxan's sales than most think.