Treatment Review #17 - March 1995

Researchers are still developing new types, and testing new doses of protease inhibitors. One protease inhibitor that has been tested - and dropped by the company that makes it - caused liver problems. Another has very poor bioavailability (which means that, however much someone actually takes, enough of the drug doesn't get into their system to be effective).

In order for a drug to be made available by prescription, it must be easily absorbed by the body, and the company that makes it must be able to produce it in sufficient quantities for sale to all those for whom it is prescribed. So far, there are problems with both of these things, but testing and fine-tuning continues.

The HIV virus has become resistant to every protease inhibitor tested so far. This is why most researchers believe that, regardless of what type of protease inhibitor someone takes, it will need to be taken in combination with other anti-HIV drugs. David Ho of the Aaron Diamond Research Center in New York, along with other leading AIDS researchers, suggests that combinations of protease inhibitors may prove to be more useful than just one.

The three protease inhibitors described below so far seem to be safe, but little is known about their long term use. Hoffman-LaRoche, a large pharmaceutical company, is testing a protease inhibitor called saquinavir. Saquinavir is difficult and expensive to make. Results from clinical trials of the drug have been promising, yet they haven't shown that this is the knock-out drug everyone had hoped for - at least not at the doses being tested. The company says it will not be able to produce enough of this drug for a large distribution program until mid-1995. Still, over 4,000 people are taking this drug in Phase III clinical trials. The trials are studying saquinavir in combination with AZT, ddI, ddC and nevirapine. In earlier studies, this protease inhibitor reduced the amount of HIV in the body.

The drug company, Abbott, is also testing a protease inhibitor. Their drug, ABT-538, is beginning Phase III studies, alone and in combination with AZT. The drug has high bioavailability, with over 90% of the drug being absorbed in the body. Because earlier studies showed that ABT-538 can cause liver and eye damage, eye examinations and liver tests will be part of current and future trials.

A new study of another protease inhibitor has just opened. This one is made by Merck, the world's largest drug company. It is called L-735, 524. The drug is being studied alone and in combination with AZT and 3TC. Earlier trials showed that resistance developed quickly to L-735, and it is hoped that higher doses and combination treatment will overcome this problem. Merck gets a big star for putting this study together so quickly.

For more information about clinical trials of protease inhibitors currently looking for participants - including private and government sponsored research sites - call The Network. We can also tell you about other approved, alternative and experimental drugs.

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