Thanks for returning to the Biotech Mailbag, where I try my best to answer your biotech investment questions. This week, I'll focus on Cell Genesys ( CEGE), Encysive Pharmaceuticals ( ENCY), Gilead Sciences ( GILD) and Alexion Pharmaceuticals ( ALXN).

I'll kick off the action with a note from Dore S., who writes: "Hey Adam, your faithful herd would probably appreciate an update on Cell Genesys. The company released a Feb. 15 press release that smelled like a subset analysis but has catapulted the stock. Your two cents for all to read would be appreciated."

Dore's sense of smell is pretty good. I'm not a believer in Cell Genesys, and nothing in this latest data presentation for its GVAX prostate cancer vaccine, GVAX-Prostate, compels me to change my mind.

Last week, Cell Genesys reported that researchers analyzing blood samples from prostate cancer patients in a long-ago completed phase II study found two antibody, or immune, responses to GVAX-Prostate that correlated positively with significantly longer survival.

Interesting, except for the fact that in order to find the two antigens responsible for this immune response, the researchers looked at dozens of different antigens -- including some they previously though would be linked to an immune response -- but found nothing.

What this tells us is that Cell Genesys had to go deep-sea fishing with a very large net to find some positive data to report. That's not necessarily a bad thing, but it certainly doesn't prove that GVAX-Prostate is doing what it needs to do most -- helping prostate cancer patients live longer.

Let's not forget that we've seen this game played before. Remember Genitope ( GTOP)? It, too, tried to tie an immune response to its MyVax cancer vaccine to a positive clinical benefit for patients. In the end, MyVax turned out to be a dismal failure .

Cell Genesys is running two phase III studies of GVAX-Prostate right now, but that data's not expected until the second half of 2009.

Meantime, Cell Genesys needs to stay visible to investors today. What's one way to do this? Analyze old clinical trials over and over again to scrap together something "new" to say.

That helps put some pop into the stock in the near term, which is what happened over the past week. Shares were up more than 50% at one point.

As I write this Friday, the stock has slipped to around $2.62 after reaching as high as $3.36 on Thursday. Prior to this week, the stock hadn't seen the $3 level since early November.

But I don't think this week's data, or the increase in Cell Genesys' stock price, are indicative of what will happen when we finally see the phase III data on GVAX-Prostate. Like I said, I don't have high hopes for this cancer vaccine, especially in the first phase III trial. In my book, GVAX-Prostate doesn't win.

Pfizer's ( PFE) decision to buy Encysive Pharmaceuticals for $195 million -- essentially spare change that the drug giant found under the cushions of its reception-area couch -- finally puts to rest to one of the more pitiful biotech sagas in recent memory.

Few companies in this oh-so-fun sector of ours have managed to rack up a record of futility quite like Encysive. There are only a handful of companies that can manage to get turned down three times by the FDA for the same drug. In this case, Encysive was never able to gets its pulmonary arterial hypertension drug Thelin approved in the U.S.

So, now that Pfizer is gobbling them up for a mere $2.35 a share, we can say goodbye and thank Encysive for all the fun we've had at its expense.

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