MEDICAL UPDATE: Review of Some Newer Antivirals


MEDICAL UPDATE: Review of Some Newer Antivirals

Being Alive Newsletter, Being Alive/Los Angeles - June 1992
Mark Katz MD and reported by Jim Stoecker

FLT is an antiviral drug that is identical structurally to AZT, except for one different chemical group. This change appears to make FLT ten to twenty times more potent than AZT. This new antiviral may be very useful for treating patients who have developed resistance to AZT. FLT has shown no cross resistance to AZT. This means that if HIV is resistant to AZT, the virus need not be resistant to FLT. The major side effect of this new drug is, as might be expected, anemia. Right now, a Phase I study is underway that will tell us mainly if the drug is well tolerated and at what dosage.

We have been talking about tat inhibitors for some time. A Phase I study of Hoffman-LaRoche's RO5-3335 is ongoing at Johns Hopkins in Baltimore. Although we have no real efficacy data yet, we do know that the drug is well absorbed and appears to work against AZT-resistant strains of HIV. So far, no resistance to the drug has emerged, unlike that experienced during the recent Phase I testing of the "L" drugs.

We have had reports that one form of tat inhibitor stopped HIV replication in a test tube in three days or less. We now need to determine efficacy in humans. UCSD is slated to complete by summer's end a Phase I trial of tat inhibitors. We can only hope that clear efficacy will be shown. If not, further work on tat inhibitors may be shelved.

One new antiviral that has problems is nevirapine (BIRG-587). Resistance appears very rapidly and further studies of the drug may be dropped.

Finally, there are the protease inhibitors, another antiviral that we have covered extensively in past months. The problem discovered in Phase I testing is that the drug is very poorly absorbed by humans. Only about 4% of the oral dose being tested was actually usable by the body. Now the manufacturers need to reformulate their protease inhibitors as an injectable drug or a much more potent oral drug.
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