Shares of biopharmaceutical company Trimeris Inc. soared Wednesday, a day after the company reported it moved to a profit in the third quarter on a strong showing by its HIV drug Fuzeon.

The stock gained $1.92, or 24.2 percent, to reach $9.86 in afternoon trading as volume surged to more than 15 times its average level. Shares have traded between $7.21 and $14.92 over the last 52 weeks.

The Morrisville, N.C.-based company reported a third-quarter profit late Tuesday on a doubling of revenue from royalty and collaborations. The boost came mainly from global Fuzeon sales of $63 million and its partnership with Swiss drug maker Roche Holding AG.

Analysts took a cool view of the results, predicting a likely slowing in growth of Fuzeon sales. Citing side effect issues and competition, several analysts forecast a tougher market for the drug. The big boost in profit was partly due to lighter operating expenses.

"While the focus on spending control and profitability is encouraging in the near term, absent visibility on growth drivers from Fuzeon or the pipeline, we doubt that over the long-term the earnings story is sustainable," said Morgan Stanley analyst Dr. Steven Harr.

Harr reaffirmed an "Underweight" rating for the company.

Goldman Sachs analyst Meg Malloy reaffirmed a "Neutral" rating with an $11.50 price target, saying Fuzeon growth will continue to be gradual.

"Growth has been hindered by administration and injection site reactions, despite solid efficacy and favorable guideline positioning," she said.

The company is working on developing a next-generation version of the drug and that would represent a longer term driver. Trimeris is also awaiting a Food and Drug Administration decision for Fuzeon administered through its needle-less Biojector 2000 system. The FDA has requested more safety data.

"The level of profitability should depend not only on Fuzeon growth but also on research & development spending, the latter we expect to pick up as the pipeline advances," she wrote.

ThinkEquity Partners analyst Vinny Jindal reaffirmed a "Sell" rating with a $8 price target, citing similar issues and an increasingly competitive field.