New Data Show FUZEON(R) Continues to Provide Significant Immune System Benefits in Patients Despite Ongoing Viral Replication

A new analysis of the TORO studies presented in an oralsession at the 15th International HIV Drug Resistance Workshop inSitges, Spain demonstrate continued CD4 cell increases in somepatients who continued with FUZEON(R) (enfuvirtide)-based regimensdespite virologic failure and FUZEON resistance. Of further note wasthe correlation of certain FUZEON resistance mutations with theobserved increases in CD4 immune cells, corroborating the findings ofother investigators presented in February 2006 at the Conference onRetroviruses and Opportunistic Infections. Co-developed by Roche andTrimeris (Nasdaq: TRMS), FUZEON is the first and only HIV fusioninhibitor. Unlike other HIV drugs that work after HIV has entered thehuman immune cell, FUZEON works by blocking the virus from enteringthe human immune cell.

"Characterizing the impact of FUZEON-related resistance mutationsis an important endeavor, both clinically and scientifically," saidCarlo Federico Perno, M.D., Ph.D., Professor of Virology at theUniversity of Rome Tor Vergata, Italy. "This new analysis from theTORO studies confirms a similar analysis from our research and showsthat FUZEON-related resistance mutations may be associated withmaintenance of CD4 cell counts or even continued CD4 improvements insome patients."

More About the Study

The new data is based on an analysis of patients who experiencedvirological failure in the TORO Phase III studies with FUZEON (n=355).Complete CD4 cell count data for up to 96 weeks following virologicfailure was available for 134 patients. Using genotypic analysis,these patients were divided into subgroups based on treatment-emergentresistance mutations to FUZEON that occur in the region of gp41 aminoacids 36-45. When compared to levels before initiation of therapy withFUZEON, patients either maintained CD4 cell gains or exhibitedstatistically significant and clinically meaningful increases in CD4cell counts over 48 weeks of additional FUZEON therapy despitevirological rebound. Of note, patients (n=58; 43%) with a particularmutation, the V38A, exhibited additional increases in CD4 cell countfor 48 weeks after virologic failure to FUZEON, while patients (n=68;51%) with other mutations including N43D maintained their CD4 cellbenefit from baseline through 48 weeks after virologic failure whileon FUZEON. Only patients with the Q40H mutation (n=8; 6%) had declinesin CD4 cells after virologic failure.

A separate poster presentation at the workshop shed further lighton one of these mutations, N43D and its ability to impact viralfitness. This work shows that this mutation causes significantstructural defects in regions of the gp41 HIV virus envelope protein,decreasing the stability of interactions which are critical for theviral fusion and entry into CD4 cells. Such structural changes to theHIV virus caused by the N43D mutation may illustrate the cost to thevirus of circumventing FUZEON in order to continue replication. Theseobservations support the important role that the envelope plays in HIVreplication and pathogenesis and point to unique contributions thatentry inhibitors may make to treatment strategies.

Resistance Profiles of Next-Generation Fusion Inhibitor Candidates

Roche and Trimeris are developing two next-generation fusioninhibitor peptide candidates, TRI-999 and TRI-1144, which wereselected by the companies for progression into full pre-clinicaldevelopment in early 2006. The compounds have shown potent antiviralactivity and durable control of HIV replication in vitro, withdesirable pharmacokinetic properties in vivo supporting the objectiveof achieving once-weekly dosing for these novel fusion inhibitors. Newdata presented at the resistance workshop show that the compoundsexhibit substantial potency and considerably greater consistency ofactivity in vitro against viruses that were sensitive to FUZEON, andmore importantly, those with substantial resistance to FUZEON.

Facts About FUZEON

Administered via one 90 mg subcutaneous injection twice-daily,FUZEON is the first and only fusion inhibitor for the treatment ofHIV. Unlike other HIV drugs that work after HIV has entered the humanimmune cell, FUZEON works outside the CD4 cell, blocking HIV fromentering the cell. For this reason, FUZEON is effective intreatment-experienced patients who have developed resistance to otheranti-HIV drugs, though patients may still develop resistance toFUZEON. FUZEON was granted accelerated approval by the U.S. Food andDrug Administration (FDA) in March 2003 on the basis of 24-week data,and was granted traditional (full) approval on Oct. 15, 2004 on thebasis of long-term 48-week data.

Recently updated Antiretroviral Treatment Guidelines from the U.S.Department of Health and Human Services (DHHS) established the use ofFUZEON and an active ritonavir-boosted PI and to achieve undetectableHIV in treatment-experienced patients. These new guidelines citedseveral recent clinical trials of new boosted PIs intreatment-experienced patients, demonstrating better and moreprolonged virologic response in patients taking FUZEON as part of aregimen that includes these new boosted PIs.

Injection Site Reactions (ISRs): ISRs are the most common adverseevents associated with FUZEON. ISRs occurred in 98% of patientsstudied and 4% discontinued FUZEON due to ISRs over 48 weeks.Signs/symptoms may include pain and discomfort, hardened skin,redness, bumps, itching and swelling. Eleven percent of patients hadlocal reactions that required analgesics or limited usual activities.

Pneumonia: An increased rate of bacterial pneumonia was observedin subjects treated with FUZEON in the Phase III clinical trialscompared to the control arm. It is unclear if the increased incidenceof pneumonia is related to FUZEON use. Patients with HIV infectionshould be carefully monitored for signs and symptoms of pneumonia.Risk factors for pneumonia included low initial CD4 cell count, highinitial viral load, intravenous drug use, smoking and a prior historyof lung disease.

Hypersensitivity Reactions: Systemic hypersensitivity reactionshave been associated with FUZEON therapy and may recur on rechallenge.Hypersensitivity reactions have included individually and incombination: rash, fever, nausea and vomiting, chills, rigors,hypotension and elevated serum liver transaminases. Other adverseevents that may be immune mediated and have been reported in subjectsreceiving FUZEON include primary immune complex reaction, respiratorydistress, glomerulonephritis and Guillain-Barre syndrome.

Other Adverse Events: The events most frequently reported inpatients receiving FUZEON plus an optimized background regimen werediarrhea (32%), nausea (23%) and fatigue (20%). These events were seenat a lower incidence in patients taking a FUZEON-based regimencompared to those receiving an optimized background regimen withoutFUZEON when taking into account the uneven number of patients in eacharm and the length of time they are in that arm. As measured in numberper 100 patient years, the incidence was: diarrhea (38 per 100patient-years in subjects receiving FUZEON-based regimens vs. 73 per100 patient-years in patients who did not receive FUZEON), nausea (27vs. 50, respectively) and fatigue (24 vs. 38, respectively).

Roche in HIV

Roche is at the forefront of efforts to combat HIV infection andAIDS, committed for 15 years to groundbreaking research anddevelopment of new drugs and diagnostic technology. The objective isto provide tailored treatment solutions and an improved standard ofcare worldwide for those people living with HIV.

Roche and Trimeris are working together to discover, develop andcommercialize the next generation of HIV fusion inhibitors.

About Roche

Hoffmann-La Roche Inc. (Roche), based in Nutley, N.J., is the U.S.pharmaceuticals headquarters of the Roche Group, one of the world'sleading research-oriented healthcare groups with core businesses inpharmaceuticals and diagnostics. For more than 100 years, the RocheGroup has been committed to developing innovative products andservices that address prevention, diagnosis and treatment of diseases,thus enhancing people's health and quality of life. An employer ofchoice, in 2005, Roche was named one of Fortune magazine's BestCompanies to Work For in America, one of the Top 20 Employers (Sciencemagazine), ranked as the No. 3 Best Company to Work For in NJ (NJ Bizmagazine), the No. 1 Company to Sell For (Selling Power), and one ofAARP's Top Companies for Older Workers. For additional informationabout the U.S. pharmaceuticals business, visit our websites:http://www.rocheusa.com or www.roche.us.

About Trimeris, Inc.

Trimeris, Inc. (Nasdaq: TRMS) is a biopharmaceutical companyengaged in the discovery, development and commercialization of noveltherapeutic agents for the treatment of viral disease. The coretechnology platform of fusion inhibition is based on blocking viralentry into host cells. FUZEON, approved in the U.S., Canada andEuropean Union, is the first in a new class of anti-HIV drugs calledfusion inhibitors. Trimeris is developing FUZEON and futuregenerations of peptide fusion inhibitors in collaboration with F.Hoffmann-La Roche Ltd. For more information about Trimeris, pleasevisit the company's Web site at http://www.trimeris.com.

Trimeris Safe Harbor Statement

This document and any attachments may contain forward-lookinginformation about the Company's financial results and businessprospects that involve substantial risks and uncertainties. Thesestatements can be identified by the fact that they use words such as"expect," "project," "intend," "plan," "believe" and other words andterms of similar meaning. Among the factors that could cause actualresults to differ materially are the following: there is uncertaintyregarding the success of research and development activities,regulatory authorizations and product commercializations; we aredependent on third parties for the sale, marketing and distribution ofour drug candidates; the results of our previous clinical trials arenot necessarily indicative of future clinical trials; and our drugcandidates are based upon novel technology, are difficult andexpensive to manufacture and may cause unexpected side effects. For adetailed description of these factors, see Trimeris' Form 10-K filedwith the Securities and Exchange Commission on March 10, 2006 and itsperiodic reports filed with the SEC.