HIV Digest	HIV Digest Archive

T-20 (also known as pentafuside, previously DP-178) is a powerful new experimental antiretroviral, and the most prominent of a new class of anti-HIV drugs, the fusion inhibitors. In vitro studies previously suggested that the drug had extremely potent antiviral activity; now, final results of a pilot study in 16 people show that T-20 can reduce plasma HIV viral load by two logs through a novel mechanism of action.

As a fusion inhibitor, T-20 attacks HIV at a point in its replication cycle not yet targeted by any existing antiretroviral. The drug targets the fusion phase of HIV infection, in which the HIV virion (virus particle) fuses or binds with a new target cell, such as a CD4 T-cell. T-20 is thought to somehow interfere with the gp41 surface molecule on HIV to the extent that the virus is incapable of binding with and thereby infecting new target cells.

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In its current form, T-20 must be administered twice daily by intravenous injections or continuously by subcutaneous (under the skin) infusion.

People who took the highest dose, 100 mg twice daily, experienced the largest reductions in HIV viral load. Within 10-14 days after beginning T-20, all four developed undetectable HIV levels, or a viral load drop of nearly two logs. Of these four, three were treatment-naive; that is, they had never before taken any antiretroviral therapy. The fourth had gone through a two-week washout period during which all therapy was stopped.

Results of this trial indicate that T-20 is well-tolerated overall. No one discontinued because of adverse events and no safety problems were reported. Although a few people reported fever and headache, investigators considered these unrelated to treatment.

Viral resistance to T-20 has not yet been seen. However, the longer any individual uses any given drug, the more likely it is that resistance to that drug will develop. Longitudinal data have not yet been reported on T-20. If used for extended periods of time, T-20 will be taken in combination with other antiretroviral drugs to delay the develo pment of resistance. Since the drug has a new mechanism of action, it is unlikely to pose any problems with cross-resistance with other available antiretrovirals.

A new trial sponsored by the drug's manufacturer is currently enrolling participants. This trial is designed to evaluate antiviral suppression over a longer period of time, and to establish the best dose of T-20 for use with an infusion pump. Researchers also will evaluate whether or not the body produces antibodies against T-20.

Editor's Note: from Bulletin of Experimental Treatments for AIDS