An Aids breakthrough on the other side of=20 the world puts South Africa’s hopesin=20 perspective, writes Lesley Cowling=20
AS reports of a possible cure for Aids=20 broke in South Africa last week, at the=20 other end of the world about 2 300 HIV=20 research-ers were hearing news about=20 another potent new drug that could=20 eradicate HIV, the virus that causes Aids.
Pharmaceutical company Abbot Laboratories=20 announced at the 4th Conference on=20 Retroviruses and Opportunistic Infections=20 in Washington, DC, it had developed a new,=20 improved version of protease inhibitors,=20 the drugs hailed at last year’s Aids=20 conference in Vancouver as the possible=20 death knell of the virus.
Protease inhibitors attack the enzyme=20 protease, used by HIV to reproduce itself,=20 and so damage the virus’s ability to grow.=20 Results in the many trials of protease=20 inhibitors conducted in the past two years=20 have been spectacular, and three types were=20 licensed in countries across the world last=20 year – including South Africa.=20
But the drugs had a drawback – the virus,=20 which has an amazing ability to change=20 itself when confronted with obstacles,=20 learnt, in many cases, to adapt=20 sufficiently to overcome protease=20 inhibitors. This led to what doctors call=20 “resistance”, and many patients found HIV=20 would regain its hold on them after some=20 months or years.
But this week Abbot reported that=20 experiments with its new protease=20 inhibitor, ABT-378, on HIV grown in=20 laboratory cultures and trials on rats=20 showed the virus was not adapting and=20 overcoming ABT, and resistance to this drug=20 looked unlikely.
That problem being resolved makes protease=20 inhibitors, particularly when used with=20 other Aids drugs, the likeliest candidate=20 for an Aids cure. And it gives it the edge=20 over the yet untested and secret formula=20 Virodene in every respect except cost.
The claims made for Virodene by the=20 researchers are exciting, with certain of=20 its properties touted as being better than=20 any other drug available. But in fact, the=20 results they pointed to as unique and=20 superior have been equalled or bettered by=20 protease inhibitors in many trials. The=20 following claims have been made debatable=20 by developments in HIV treatment:
* Newspaper reports said when Virodene was=20 given to about 12 Aids patients in a drug=20 trial, it reduced their viral load (amount=20 of the virus detected in the blood)=20 “dramatically” in two to three weeks. Other=20 drugs could not do this as quickly, the=20 reports said.
Not so. A number of combination drug=20 studies, which included a protease=20 inhibitor, were presented to the Washington=20 conference last week showing that patients=20 had dramatic drops in viral loads within=20 four weeks.
For example, a study from Colorado, in=20 which nine patients were treated for four=20 weeks with the combination of a protease=20 inhibitor and a drug of the same type as=20 AZT showed a drop in viral load to=20 undetectable levels in five patients.
Scientists at the conference theorised that=20 there may be three phases of immune=20 responses associated with combination drug=20 (or antiviral) therapy. The first phase of=20 15 days marks a rapid decrease in the=20 virus’s reproduction and a surge in the=20 body’s immune responses, like large-scale=20 mobilisation of the body’s fighter CD4=20 cells. This accounts for the dramatic=20 results in the first days of a new drug=20 regime.
* Researcher Olga Visser cited a rapid rise=20 in CD4 cells (the immune cells that HIV=20 attacks and kills) in her patients as a=20 sign of Virodene’s effectiveness, but=20 acknowledged that other drugs push CD4=20 levels up higher than Virodene does. A=20 number of studies at the conference=20 confirmed this.
* Visser was quoted as saying Virodene=20 fights HIV “in areas where other drugs=20 can’t reach it, such as in the lymph=20 glands”. The report went on to say the drug=20 cocktail treatment can only fight the virus=20 in the blood.
This is not strictly accurate. Studies=20 presented to the conference showed the=20 virus is generally higher in the lymph=20 nodes than it is in the blood, and even=20 when it is undetectable in the blood, it=20 can be found in lymph nodes.
But international Aids expert Dr David Ho=20 presented a study at the conference that=20 showed if you clear the virus from the=20 blood using a drug combination that=20 includes protease inhibitors, this=20 eventually reduces or clears the virus from=20 the lymph organs. Other studies showed HIV=20 can be cleared from the semen, too.
Ho said new research suggests it may take=20 at least two to three years to clear the=20 virus from a newly infected person, not one=20 year as previously suggested. He refused to=20 speculate on how long complete viral=20 clearance might take in chronically=20 infected patients, or even whether it was=20 possible.
The fact that there are drug regimens as=20 good as, or better than, Virodene currently=20 available does not mean Virodene may not=20 prove to be a cure, too, or that research=20 into its effects should not be done.=20 Research is especially necessary because=20 the researchers say the cost of the drug=20 will be low – R80 to R160 a month, against=20 the R2 000 it currently costs Aids patients=20 for protease inhibitors, and more for=20 combination drugs.
But it will take years before Virodene has=20 been sufficiently developed to be used as a=20 treatment, and its fate is still uncertain.=20 HIV patients need treatment now, and public=20 health policy should focus not only on how=20 to bring Virodene on to the market in the=20 future, but on how to assist patients in=20 their present predicament. This means=20 looking at creative ways to fund=20 combination treatment using protease=20 inhibitors.