Yesterday, tiny drug developer Trimeris (NASDAQ:TRMS) announced that it finally found a permanent CEO to help get itself in order following the resignation of its former leader a year ago.

Shares of Trimeris have floundered ever since it announced a reorganization plan last year, and sales growth of its lead drug -- HIV treatment Fuzeon -- started faltering in the U.S. and Canada.

Trimeris' new CEO, Martin Mattingly, has his work cut out for him. In the third quarter that just ended, sales of Fuzeon actually fell year over year in the U.S. The forecast for full-year Fuzeon sales growth is for a "modest" uptick over last year's worldwide sales of $249 million, thanks to sales outside the U.S. and Canada making up for the slowing down of North America sales.

U.S. and Canada
Fuzeon Sales*

Growth (YOY) 

Q3 07



Q2 07



Q1 07



Q4 06



*In millions.

Part of the problem for Trimeris and why it sports an enterprise value of about $100 million after subtracting its $63 million in cash and investments from its market cap is that there are new HIV treatments just entering the market after Pfizer's (NYSE:PFE) Selzentry and Merck's (NYSE:MRK) Isentress received marketing approval in August and last month, respectively.

Both Selzentry and Isentress target the same patient population as Fuzeon (albeit only a subset of Selzentry's patients) -- HIV patients who are not responding well to front-line antiretroviral agents like Bristol-Myers Squibb's (NYSE:BMY) Atripla.

Isentress received approval too late to affect third-quarter U.S. sales of Fuzeon, so Selzentry is likely responsible for the drop in U.S. and Canada sales last quarter. Even though Fuzeon and these new compounds are indicated for the same patient group and the new compounds are less onerous to administer, being oral compounds, there will still be a market for Fuzeon.

Some patients respond better to certain treatments, and HIV drug resistance will always be a problem necessitating the usage of different classes of therapies, so the most important thing that Trimeris' new CEO can do is make sure that doctors don't forget about Fuzeon in favor of these new and interesting large-pharma compounds.

Here's some more Foolishness on HIV and the companies fighting it: