PRNewswire - October 29, 2004

Dr. Petropoulos' talk will summarize the current state of the art regarding the assessment of viral fitness, and describe ViroLogic's ongoing research seeking to establish its Replication Capacity (RC) assay, an in vitro surrogate for viral fitness, as a clinical tool for use in the management of HIV infection. Viral fitness refers to the ability of HIV to replicate and cause disease in the infected host.

"The development of the RC assay has created the possibility that we might exploit HIV's predilection for mutation for the benefit of patients," said Dr. Petropoulos. "The recent award of a phase II Small Business Innovative Research (SBIR) grant from the National Institutes of Health allows us to initiate multiple large collaborative studies of the utility of RC focusing on specific clinical situations where we believe it may provide valuable information to clinicians. If successful, we expect RC to aid physicians in the overall optimization of therapeutic strategies against the virus and the cost-effective utilization of drugs available to patients."

As HIV mutates, it often is forced to pay a price in exchange for the development of resistance to drugs and the evasion of host immunity. Replication capacity, or fitness, represents the cost to the virus of pursuing such survival strategies. As such, alterations in viral fitness, as measured by the RC assay, may translate into better outcomes for patients as a consequence of the impaired abilities of the virus to replicate and cause disease.

The company also announced eight other presentations, including three oral and five poster presentations, related to its novel drug resistance products and technologies. The oral presentations will focus on various applications of the PhenoSense Entry assay, increasingly utilized by drug developers to assess resistance to the new entry inhibitor class of drugs as well as viral tropism for chemokine co-receptors. The poster presentations describe various aspects of genotypic and phenotypic resistance to currently available drugs, replication capacity, and resistance to CCR5 antagonists. Taken together, these nine presentations highlight ViroLogic's continued contributions to key areas of HIV research and demonstrate the Company's ongoing commitment to providing innovative solutions for patients suffering with HIV infection.

Details are as follows:

Presentation Time: Saturday, October 30, 11:30 a.m. - 1:00 p.m.

Presentation Number: H-184

Relationship Between Low Replication Capacity (RC) and Protease Inhibitor (PI) Hypersusceptibility in >3000 Clinical Samples Lacking PI Resistance Mutations

Presentation Time: Saturday, October 30, 11:30 a.m. - 1:00 p.m.

Presentation Number: H-179

Mutations in Reverse Transcriptase (RT) Associated with Reduced Susceptibility to Stavudine in HIV-1 Containing the K65R Mutation

Presentation Time: Saturday, October 30, 11:30 a.m. - 1:00 p.m.

Presentation Number: H-180

A Comparison of the Phenotypic Susceptibility Profiles of Emtricitabine (FTC) and Lamivudine (3TC)

Presentation Time: Saturday, October 30, 11:30 a.m. - 1:00 p.m.

Presentation Number: H-192

HIV Resistance to CCR5 Antagonists In Vitro Requires Multiple Mutations and Is Associated with Reduced Infectivity

Presentation Time: Saturday, October 30, 11:30 a.m. - 1:00 p.m.

Presentation Number: H-178

Characterization of Patient-Derived HIV-1 Isolates Containing the L74V or K65R Mutations in Reverse Transcriptase

Presentation Time: Sunday, October 31, 3:45 p.m. - 4:00 p.m.

Presentation Number: H-1137

HIV-1 Entry Inhibitor Escape Occurs by Multiple Molecular Mechanisms

Presentation Time: Sunday, October 31, 3:30 p.m. - 3:45 p.m.

Presentation Number: H-1136

HIV-1 Co-Receptor Tropism in Treatment Naive and Experienced Subjects

Presentation Time: Sunday, October 31, 3:15 p.m. - 3:30 p.m.

Presentation Number: H-1135

Prevalence and Predictive Factors for CCR5 and CXCR4 Co-Receptor Usage in a Large Cohort of HIV Positive Individuals

About Replication Capacity (RC)

RC provides a measure of the ability of HIV to replicate and to deplete the immune system. RC testing is only commercially available through ViroLogic and is currently provided free of charge when either of the Company's phenotypic resistance assays (PhenoSense, PhenoSense GT) is ordered.

About ViroLogic

ViroLogic is a biotechnology company advancing individualized medicine by discovering, developing and marketing innovative products to guide and improve treatment of serious viral diseases such as AIDS and hepatitis. The Company's products are designed to help doctors optimize treatment regimens that lead to better patient outcomes and reduced costs. ViroLogic's technology is also being used by numerous biopharmaceutical companies to develop new and improved anti-viral therapeutics and vaccines targeted at emerging drug-resistant viruses. More information about the Company and its technology can be found on its website at http://www.virologic.com.

Forward Looking Statements

Certain statements in this press release are forward-looking. These forward-looking statements are subject to risks and uncertainties and other factors, which may cause actual results to differ materially from anticipated results or expectations and include, but are not limited to, the timing of customer clinical trials, risks related to our pending merger with ACLARA, including the risk that the closing conditions of the merger may not be satisfied and the merger may not be completed, and that costs related to the proposed merger may adversely impact ViroLogic's financial performance and/or condition, the risk that the Company's products may not perform, the risk that collaborative studies may not proceed as planned or produce the expected results, whether ViroLogic successfully introduces new products, risks related to the implementation of the Company's distribution agreement with a national lab, whether others introduce competitive products, the risk that the Company's products may not continue to be accepted or that increased demand may not develop as anticipated, the risk that gross margins may not increase as expected, whether payors will authorize reimbursement for its products, whether the FDA or any other agency will decide to regulate ViroLogic's products or services, whether the Company will encounter problems or delays in automating its processes, whether intellectual property underlying the Company's technology is adequate, whether licenses to third party technology will be available, and whether ViroLogic will be able to raise sufficient capital when required. For a discussion of these and other factors that may cause ViroLogic's actual events to differ from those projected, please refer to the Company's most recent annual report on Form 10-K, quarterly reports on Form 10-Q, and the preliminary amended Joint Proxy/Prospectus related to the proposed merger with ACLARA, as well as other subsequent filings with the Securities and Exchange Commission.

SOURCE ViroLogic, Inc.

Web Site: http://www.virologic.com

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