The Body Covers: The 39th Annual Meeting of the Infectious Diseases Society of America
Cutting-Edge Issues in HIV Medicine (Symposium)
October 27, 2001
He organized his summary of the new drugs by class. There was not a lot of new information, but it was a good overview. The list is long, so I will only summarize the highlights of each compound.
Protease Inhibitors in DevelopmentTipranavir
is the first non-peptidic protease inhibitor in development for the treatment of HIV-1. It is very active in the treatment of resistant virus. The main problem with tipranavir is its poor pharmacokinetics, which makes combination with ritonavir necessary. The first clinical studies were presented during the IAS Conference in Buenos Aires, and they look pretty good. Boehringer is still trying to figure out the right dosing of this drug. Phase II/III studies are ready to roll.
Atazanavir (BMS-232632) is the first once-a-day protease inhibitor. It is reasonably active against HIV (as potent as nelfinavir in trials). The main problem with this new drug is the risk of developing hyperbilirubinemia, a risk that is clearly dose-dependent. This problem makes combination with ritonavir a bad idea since toxicity would only worsen. The good news about this drug is its simplicity of use and the lack of effects in lipid metabolism.
Amprenavir pro-drug. The most unfavorable aspect of agenerase (the "parent" drug of amprenavir) is the pill burden. Full-dose agenerase requires eight large capsules (1,200mg) twice per day. Recently, everyone has been using agenerase combined with low-dose ritonavir to boost agenerase levels, increase its potency and lessen the pill burden (when combined with 100mg of ritonavir, the agenerase dose can be reduced to 600mg -- four pills -- twice a day). This formulation lowers pill burden to two pills BID.
Tibotec 114. This new protease inhibitor is very potent against resistant virus. The company is starting phase I/II studies.
Mozenavir (DMP-450) is an experimental protease inhibitor being developed by Triangle Pharmaceuticals.
NRTIs in DevelopmentDAPD
, a guanosine analogue from Triangle Pharmaceuticals, is active in vitro against both HIV-1 and HBV. It has good activity in vivo, as shown in a 14-day trial. We are all awaiting more data on this promising nucleoside.
Tenofovir is a nucleotide with a half-life of about 17 hours, allowing for once-daily regimens. This drug was just approved by the FDA. Gilead finally received a general approval for use in HIV infection, not just in cases of drug failure. Tenofovir is active against virus with nucleoside resistance, although AZT resistance probably decreases its activity.
In the NNRTI class, Dr. Eron discussed TMC 120 and 125, two NNRTIs being developed by Tibotec-Virco. They have good activity in vitro and in short clinical trials. It is unclear at this time whether these drugs are really "second-generation" NNRTIs.
New targets are being explored actively: attachment inhibitors; fusion inhibitors like T-20 and T-1249; and chemokine receptor inhibitors, the most promising being SCH-C, which recently had its phase I studies reactivated (it had cardiac toxicity at higher doses in normal hosts).
Dr. Eron concluded his talk by discussing the new class of integrase inhibitors Merck is getting ready to evaluate in clinical trials.
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