16-Week Phase II Clinical Results Presented at ICAAC

SAN FRANCISCO, CA, September 27, 1999 -- Trimeris, Inc. (Nasdaq: TRMS) and Roche announced today 16-week results from a Phase II clinical trial (T20-205) evaluating the safety and antiviral activity of T-20, a member of a new class of anti-HIV compounds known as fusion inhibitors. Unlike other anti-HIV medications, fusion inhibitors attack and block the HIV virus before it enters the host cell. Results at 16 weeks showed that 33 of 55 (60%) of heavily pre-treated patients who were given T-20 in combination with oral antiretroviral agents responded with a clinically significant reduction of HIV in the blood. Indeed, 20 of the 55 (36%) had virus levels below the level of quantification (400 copies/mL). The study is being presented today at a late-breaking session of the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

"There is currently an unmet need for new treatment options that are effective in the ever-growing number of HIV-infected patients who have cycled through available drugs. The study results are exciting because the response rates exceeded what is normally observed in this advanced patient population. We achieved these results by combining a fusion inhibitor with traditional AIDS drugs," commented lead study investigator Jay Lalezari, MD, of Quest Clinical Research in San Francisco, CA.

"This trial answered two major questions not addressed in previous trials. The first was that T-20 provides a virologic benefit through week 16 and the second was that the drug was well tolerated through week 16. No patients discontinued the trial due to T-20-related adverse events or intolerance of the twice-daily subcutaneous injection," said Sam Hopkins, senior vice president of medical affairs at Trimeris. "The results of this study now gives us the confidence to continue planning for our phase III pivotal trials. These trials, which are scheduled to begin next year, will evaluate T-20 in patients who are extensively pre-treated as well as in those with less treatment experience."

T20-205 -- Trial Design and Results

In this Phase II clinical trial, T-20 was given in combination with oral antiretrovirals to 55 HIV-1 positive adults who had previously received T-20 during earlier trials. At entry, patients had previously been treated with a median of 11 antiretrovirals and 93% had a clinical history of triple class exposure. Ninety-three percent of patients demonstrated genotypic evidence associated with resistance to protease inhibitors (median of five mutations per patient) and 87% demonstrated mutations associated with resistance to reverse transcriptase inhibitors (median of four mutations per patient).

In this protocol, patients received T-20 (50 mg/twice daily via sub-cutaneous injection) in combination with a median of four oral antiretrovirals. Combinations were individualized to each patient and were chosen based on genotypic analysis evaluating patients’ resistance to anti-HIV medications. The median baseline viral load was 79,400 copies/mL (4.9 log10 copies/mL) and median CD4+ count was 70 cells/mm3. At sixteen weeks, 33 of55 (60%) of heavily pretreated patients who were given T-20 in combination with oral anti-retrovirals responded with a clinically significant reduction of HIV in the blood (viral suppression greater than 1.0 log10 from baseline or below the level of quantification of 400 copies/mL, using the Roche Amplicor assay) Furthermore, 20 of 55 or 36% had virus levels below the level of quantification. The average decrease in viral load for all patients was greater than 90% over the 16 week period

In all clinical studies to date, most adverse events reported on T-20 were mild or moderate in severity. The most frequent adverse events included fever, headache and lymph node abnormalities, in addition to local irritation resulting from the subcutaneous injection.

"Because T-20 attacks the HIV virus before it enters the cell it works differently than currently approved anti-HIV drugs. It therefore has the potential to combat strains of the virus that have become resistant to these treatments," said Michael Saag, M.D., director of HIV outpatient care at the University of Alabama at Birmingham. "These exciting results confirm observations from prior short-term T-20 studies where a greater than 98% reduction was seen when T-20 was given alone. This current trial goes one step further in validating the T-20 proof of concept."

This past July, Trimeris and Roche signed an agreement for the full-scale clinical testing and development of Trimeris’ two novel anti-HIV fusion inhibitors, T-20 and T-1249.

Hoffmann-La Roche Inc. is a leading research-intensive pharmaceutical company that discovers, develops, manufactures and markets numerous important prescription drugs that improve, prolong and save the lives of patients with serious illnesses. Among the company’s areas of therapeutic interest are: Virology, including HIV/AIDS and hepatitis C; Infectious Diseases, including influenza; Cardiology; Neurology; Oncology; Transplantation; Dermatology; and Metabolic Diseases, including obesity and diabetes.

The company provides a wide range of medications in the United States through its marketing and sales subsidiary, Roche Laboratories Inc. Headquartered in Nutley, N.J., both companies are members of the Basel, Switzerland-based Roche Group, a global leader in health care with principal businesses in pharmaceuticals, diagnostics, vitamins, and fragrances and flavors. For more information on Roche Pharmaceuticals in the United States, visit the company’s web site at:

Trimeris is a development stage, biopharmaceutical company engaged in the discovery and development of novel therapeutic agents that block viral infection by inhibiting viral fusion with host cells. The Company’s lead product candidate, T-20, which inhibits fusion of the human immunodeficiency virus (HIV) with host cells, is currently in Phase II clinical trials and has received fast track designation from the FDA. The Company’s second fusion inhibitor product candidate, T-1249, which also inhibits HIV fusion, has received fast track designation from the FDA and is in Phase I clinical testing.

See Fusion Inhibition in the HIV Lifecycle

Note: Except for any historical information presented herein, matters presented in this release are forward-looking statements that involve risks and uncertainties. The results of the Company’s previous clinical trials are not necessarily indicative of future clinical trials, and future results could differ materially from the results presented herein. Factors that could cause or contribute to such differences include, but are not limited to, those discussed in the "Risk Factors" section included in the Company’s Form 10-Q for the three months ended March 31, 1999 filed with the Securities and Exchange Commission on May 17, 1999 and the Company’s Registration Statement on Form S-3 as declared effective by the Securities and Exchange Commission on May 26, 1999.