Drug to combat AIDS virus on the anvil

Washington: In a path breaking research a new drug that could help overcome HIV’s growing resistance to existing antiviral drugs is about to be tested in combination with standard antivirals.

The drug is called PA-457 and it is the first of a new class of anti-HIV compounds called maturation inhibitors.

The drug is still in its early stages, and will not be generally available for at least three years.

Up to 80 per cent of HIV positive people on treatment show resistance to one or more of their drugs, according to Graham Allaway of Panacos Pharmaceuticals in Gaithersburg, Maryland, which is developing PA-457.

Panacos hopes to begin trials this month to test how well the drug works in patients whose existing drug regimes are failing.

PA-457 aims to overcome this resistance by attacking HIV on new front. Many existing drugs work by blocking reverse transcriptase, an enzyme that enables HIV to replicate within cell.

Others disable protease, which helps to assemble the virus into particles that infect other cells.

Recent experiments in collaboration with Michael Sakalian and his colleagues at the University of Oklahoma Health Sciences Center in Oklahoma City have shown that PA-457 works in a different way.

It attacks HIV by disrupting formation of a conical shield, called the capsid protein, which stores and protects the RNA heart of the HIV particles as they bud out from infected cells.

Previous lab experiments on infected human cells have shown that the drug defeats strains of HIV that are resistant to other anti-HIV drugs.

A small human trial of the drug, reported last August, showed that when given on its own it rapidly clears most HIV from the blood, driving down the levels tenfold in a matter of hours.

Other HIV researchers are also enthusiastic about PA-457.

"It's a truly novel new class of drugs, and I really support their development," says Charles Boucher of the University Hospital Utrecht in the Netherlands.

"If [PA-457] turns out to be non-toxic, easy to use and not to select for resistance, it will find good use," he adds.