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Biotech / Medical : CLTR COULTER PHARMACEUTICAL -- Ignore unavailable to you. Want to Upgrade?

To: Grainne who wrote (67)	12/3/1997 1:07:00 PM
From: Pseudo Biologist	Read Replies (2) \| Respond to of 666

Christine, Rituxan is a chimeric "naked" antibody while Bexxar is a 100% mouse radiolabeled antibody. Chimeric means that most of the non-binding part of the antibody has been replaced, using genetic engineering, by human sequences; this makes the antibody able of (1) evading a lot of potential immune response by a patient, (2) stay in circulation for a longer time; i.e., over a week or so, and (3) interact better with other components of the immune system. On the other hand, arming an antibody with, in Bexxar's case radioactive Iodine-131, makes it a better killing machine. Both antibodies recognize a molecule called CD20, which is expressed in most B-cells, and non-Hodgkins is a B-cell lymphoma. As far as I remember, Bexxar has been tested in a very similar population as Rituxan (i.e., patients who have relapsed from other therapies), but preliminary results look better than Rituxan's. Coulter also compared Bexxar with and without radioactive label, and from a small number of patients the trend is for the the "with" treatment to work better. For the reasons stated above unlabeled Bexxar is not the best surrogate for Rituxan, however. Given Bexxar apparent better profile, one can speculate that it can be used in larger patient populations like (1) newly diagnosed patients and (2) patients with more aggressive, so-called intermediate and high-grade, forms of the disease (most of the testing for all these molecules has been done in patients with low-grade disease). Of newly diagnosed patients (about 50 thousand per year in the US), only about 40-50% fit the low-grade profile. Your question on remission vs. cure cannot be answered yet. I understand that some of the early Rituxan patients are still in remission after more than a year, but this also means some have relapsed. With the 1995 or so FDA guidelines new cancer therapies do not have to "prove" very long-term effects. Comparing Bexxar and Rituxan, I see the main problem for the former the fact that Rituxan will be in the market in a couple of weeks (it was launched in Switzerland today), while Bexxar is still in the late stages of a pivotal phase III trial; even if everything goes smoothly Bexxar will not be in the market within the next 12-18 months. Rituxan is also being tested (phase II, I think) in combination with a standard chemotherapy regime (called CHOP), with very good results. With the recent FDA reforms, one can envision off-label use of that strategy soon after Rituxan hits the market; lastly IDEC has a mouse version of Rituxan, called Y2B8 (Rituxan's old name was C2B8), which is radiolabeled with Yttrium, in phase II trials. In spite of all this, and if the larger Bexxar trials confirm its apparent superiority over Rituxan, one can see big sales for Bexxar in 1999 or 2000 (by big I mean in the hundreds of millions per year); for a small company like Coulter this is very very good. PB