Progress has been made in developing drugs to treat Aids. But much less attention has been given to developing a vaccine, writes Lesley Cowling
TWO protease inhibitors – the “dramatically effective” Aids drugs – were registered in South Africa last week and a third is in the pipeline. Indinavir and ritonavir will soon be marketed under the brand names of Crixivan and Norvir; and saquinavir is currently being considered by the Medicines Control Council.
The drugs have already been registered in the US, Britain and the EU without the usual lengthy process, because early trials showed them to be remarkably effective, especially when combined with other Aids drugs.
Some studies have shown that protease inhibitors, taken with AZT, ddc or 3TC, can reduce the rate of deaths by more than two- thirds and slow the progression of the disease by more than 50%.
According to Aids information service Project Inform, “new studies of indinavir show that it combines particularly potent antiviral activity with a quite modest side- effect profile”. And Project Inform says a study of ritonavir shows that people with advanced HIV disease using the drug were significantly less likely to deteriorate or die compared to those receiving a placebo. These are significant medical advances. But applying these advances to the Aids epidemic in South Africa raises a number of issues for policymakers and local Aids experts. The first is how to get the drugs to those who need them. They are expensive – the cheapest, Crixivan, will cost $12 for a day’s supply, or R1 828,56 a month at current exchange rates.
They are not on the schedule of essential drugs at South African hospitals, which means they are not on the list of drugs supplied free to patients. The Department of Health has no plans to place them there, probably because of the enormous cost to the state. And few South Africans can afford to pay for them.
Aids activist groups in the United States charge that protease inhibitors are expensive because pharmaceutical companies are making huge profits from Aids drugs. But experts say that the situation is more complex than that.
Dr Abdul Karim, head of Epidemiology at the Medical Research Council, says the research to develop the drugs was expensive. “Of course, the pharmaceutical companies are motivated by profit, but that’s not necessarily a bad thing,” he says.
He says few government or research institutions have the resources to sink billions into research, like the pharmaceutical companies and that protease inhibitors and other Aids drugs might not be around if private companies hadn’t applied themselves to developing them.
Dr Mike Brown, medical director of Roche South Africa, says his company will not be making money on saquinavir, although they might be making money on it internationally. He says profits from the drugs are unlikely to exceed the cost of marketing them.
Brown says pharmaceutical companies take a risk when developing products, because they can never predict the long-term viability of any drug. “Drugs have a relatively limited life.”
He cites the example of AZT, once the premier Aids treatment, now overtaken by new drugs on the market.
Karim says that the advantage of a new effective drug is often seen 10 years after it is registered. Pharmaceutical companies patent their new products, but the patent expires after 10 years, and then anyone can make the drug. At this stage, prices drop substantially.
In the meantime, says Brown, the government should take a look at whether it should supply protease inhibitors. He says that although the expense may seem prohibitive, an analysis of what it costs state hospitals might show that it is more expensive to treat the opportunist diseases that are the result of HIV infection than to treat the virus itself.
If so, then medical aid companies might be persuaded to fund them, too. Obviously, this is an issue for public health policy.
An issue for local Aids researchers, on the other hand, is the question of a vaccine. Some experts argue that Africa needs a vaccine more than drug treatment, because it is much cheaper, it’s a preventative approach and it is easier to administer. “There are projects looking at vaccines, but there’s nothing on the horizon that’s a strong candidate,” says Brown.
Karim says not as much money has gone into developing a vaccine because it is not as lucrative as drug treatment. However, there is an organisation called the International Aids Vaccine Initiative and HIV expert Dr Quarraisha Karim is involved in that.
The group is trying to come up with ways to fund vaccine research, by talking to private companies, non-governmental organisations and governments.
Aids researcher Dr Lynne Morris, of the National Institute of Virology, says developing a vaccine for HIV is difficult, because the virus mutates and there are many different sub-types of HIV in different parts of the world.
Vaccines work by infecting a person with a small part of the virus so that the body develops a resistance to it and will destroy it when it appears.
Morris says that either different vaccines will have to be developed for different regions, or the vaccine will have to contain part of the virus central to all sub-types.
Vaccines are very cost-effective, once developed. “We need to find people who are willing to invest some money in it,” she says.
One possibility is getting the mining houses involved. Morris says they are already concerned about the effect HIV is having on their workforce. Miners are a high-risk group, and the mines would benefit from a vaccine.
Whatever happens, it won’t be quick. It takes years to put together a vaccine trial. And, by that time, at the rate that HIV infection is spreading in South Africa, there will be a lot fewer people who can benefit from it.