Biotech Values

[iwfal]

With EXEL, it's a little hard to oversell these data. The scans are remarkable and every doc I've talked to with experience using XL184 says the benefits of the drug are obvious, happen quickly, and disappear quickly when the drug is withdrawn (RDT has a randomized component that deprives non- soft-tissue progressors of drug).

While I agree the drug probably has some activity I suspect the bone scan data is not as positive as it sounds:

a) Lack of historical data - although see below cite

b) Given that bone scan is about bone remodeling, not presence of mets, the results are a wee bit odd - e.g. if it was shrinking the tumors wouldn't you expect a flare of activity at 6 weeks where the bone was healing.

http://meeting.ascopubs.org/cgi/content/abstract/28/15_suppl/4545

The interesting parts of this data are:

1) It is common sense that a flare should happen given the MOA of bone scans and there is evidence that it does with other drugs - so why isn't it occurring with XL184?

2) The number of patients who eventually show improvement in bone scan data after flare is very large - 80%. Yes, I understand it is among patients that showed PSA declines of >50%, and there are other patient groups without data, but my point is that it is a large number in a large subgroup - as to be expected from a marker of velocity, not position. (Derivatives exaggerate effect) Obviously there is a bunch of data we don't know - e.g. how much decline in BS activity? what about the patients who didn't flare and what was their BS measurement vs time? ... But all of this just goes to the lack of historical data.