By Mary Welch

ViroLogic Inc. raised $12.6 million in its second round of private equity financing to help launch the PhenoSense HIV phenotypic drug susceptibility assay.

"This has been a tremendously successful financing for us, particularly in light of the current difficult financing environment," said Martin Goldstein, president and CEO of South San Francisco-based ViroLogic. With the money, the privately held company can launch the test and pay for ongoing research into hepatitis B and hepatitis C, he said.

Founded in late 1995, ViroLogic is focused on developing phenotypic drug susceptibility tests to determine the best therapeutic choices for patients with viral diseases such as HIV and herpes, or cancer. PhenoSense HIV evaluates the susceptibility of the HIV in an infected individual to each of the 11 FDA-approved antiretroviral drugs, as well as to drug candidates.

For decades, physicians have been able to test bacteria for resistance to antibiotics by taking, for example, a sputum culture from a patient with pneumonia, thereby quickly obtaining a diagnosis of the disease as well as making recommendations for the best pharmaceutical treatment.

That has not been the case for viral diseases. Conventional viral susceptibility testing typically takes six to eight weeks, and is labor-intensive. "Our test results come back in real time, eight to 10 days," Goldstein said.

Testing Delay Allows Virus To Mutate

With conventional methods, the virus may mutate during testing, "just like it does in a body," Goldstein said. "The virus you tested for in the end may not have been the virus you started with." ViroLogic's faster test avoids that pitfall.

Because the HIV virus exists as a population of slightly different strains rather than a single strain, ViroLogic takes HIV patient blood samples and clones genes from the entire virus population. Among infected patient populations and even within infected individuals — viral evolution quickly can produce genetically distinct sub-populations of HIV, which eventually contribute to drug resistance.

The PhenoSense HIV test amplifies viral sequences from a patient's plasma. A resistance test vector is made by inserting these sequences into a viral vector with an indicator gene. ViroLogic uses luciferase, the substance that makes fireflies glow in the dark, to measure viral replication.

"If the virus replicates, light is produced," said Goldstein. "If you add an antiviral drug and it effectively inhibits viral replications, there is a decrease in light. But, if the virus is resistant to the drugs, more light is produced."

Physicians are constantly trying to find the best initial HIV combination treatments for particular patients, and to figure out follow-up options if the patient should become resistant to the regimen. More than half of HIV-infected patients treated with combination therapy regimens fail to sustain complete suppression of plasma HIV levels, usually due to the development of drug resistance.

Nicholas Hellman, vice president of clinical research for ViroLogic, said the best chance of a sustained therapeutic response comes during the first treatment regimen. "Once resistance develops, the probability of a sustained response is decreased," he said. "That's why, with so many drugs and drug combinations, getting it right from the start is so important."

Goldstein said the average cost of HIV therapy is $10,000 to $15,000 a year — an amount that could drop if physicians could make more informed treatment decisions. "Plus, the quality of life for the patient will be so much better," he said. ViroLogic expects to have PhenoSense HIV ready for marketing this year.

Participating in the financing were BB Biotech AG, of Schaffhausen, Switzerland; Capital Management Services, of Los Angeles; and Soros Fund Management, of New York. BB Biotech is a new investor. *

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