Delavirdine: a review of its use in HIV infection

Delavirdine, a bisheteroarylpiperazine derivative, is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that allosterically binds to HIV-1 reverse transcriptase, inhibiting both the RNA- and DNA-directed DNA polymerase functions of the enzyme. Delavirdine in combination with nucleoside reverse transcriptase inhibitors (NRTIs) produced sustained reductions in plasma viral loads and improvements in immunological responses in large randomised, double-blind, placebo-controlled studies of 48 to 54 weeks' duration. In patients with advanced HIV infection, triple therapy with delavirdine, zidovudine and lamivudine, didanosine or zalcitabine for 1 year significantly prolonged the time to virological failure compared with dual therapy (delavirdine plus zidovudine or 2 NRTIs; p < 0.0001). After 50 weeks' treatment, plasma HIV RNA levels were below the limit of detection (LOD; <50 copies/ml) for 40% of patients receiving triple therapy but for only 6% of those receiving dual NRTI therapy. Preliminary results suggest that delavirdine also has beneficial effects on surrogate markers as a component of protease inhibitor-containing triple or quadruple regimens. At 16 to 48 weeks, the minimum mean reduction in plasma viral load from baseline was 2.5 log10 copies/ml and mean CD4+ counts increased by 100 to 313 cells/microl. The proportion of patients with plasma HIV RNAlevels below the LOD (usually 200 to 500 copies/ml) ranged from 48 to 100% after > or = 16 weeks. Delavirdine was also effective as a component of saquinavir soft gel capsule-containing salvage regimens. Since delavirdine shares a common metabolic pathway (cytochrome P450 3A pathway) with other NNRTIs, HIV protease inhibitors and several drugs used to treat opportunistic infections in patients infected with HIV, the drug is associated with a number of pharmacokinetic interactions. Some of these drug interactions are clinically significant, necessitating dosage adjustments or avoidance of co-administration. Delavirdine is not recommended for use with lovastatin, simvastatin, rifabutin, rifampicin, sildenafil, ergot derivatives, quinidine, midazolam, carbamazepine, phenobarbital or phenytoin. Importantly, the drug favourably increases the plasma concentration of several protease inhibitors. Delavirdine is generally well tolerated. Skin rash is the most frequently reported adverse effect, occurring in 18 to 50% of patients receiving delavirdine-containing combination therapy in clinical trials. Although a high proportion of patients developed a rash, it was typically mild to moderate in intensity, did not result in discontinuation or adjustment of treatment in most patients and resolved quickly. The occurrence of Stevens-Johnson syndrome was rare (1 case in 1,000 patients). A retrospective analysis of pooled clinical trial data indicated that there was no significant difference in the incidence of liver toxicity, liver failure or noninfectious hepatitis between delavirdine-containing and non-delavirdine-containing antiretroviral treatment groups. In addition, the incidence of lipodystrophy, metabolic lipid disorders, hyperglycaemia and hypertriglyceridaemia was not significantly different between these 2 treatment groups.

CONCLUSIONS

In combination with NRTIs. delavirdine produces sustained improvements in surrogate markers of HIV disease and prolongs the time to virological failure in adult patients with HIV infection. Preliminary data of delavirdine as a component of protease inhibitor-containing triple or quadruple highly active antiretroviral therapy regimens indicate that patients achieve marked improvements in virological and immunological markers. The drug is generally well tolerated, with a transient skin rash, typically of mild to moderate intensity, being the most common adverse effect. Delavirdine is an effective component of recommended antiretroviral treatment strategies for adult patients with HIV infection and, in combination with 2 NRTIs as a first-line therapy, the drug has the advantage of sparing protease inhibitors for subsequent use. Since delavirdine favourably increases plasma concentrations of several protease inhibitors, the drug may also be beneficial as a component of salvage therapy in combination with protease inhibitors.

Pyrido [1,2a] indole derivatives identified as novel non-nucleoside reverse transcriptase inhibitors of human immunodeficiency virus type 1

Pyrido [1,2a] indole derivatives were identified as potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication during a random screening programme. The compounds showed no antiviral activity against HIV-2 or in cells chronically infected with HIV-1, but had good inhibitory effect against purified HIV-1 reverse transcriptase (RT) in an in vitro assay. They were therefore classified as non-nucleoside RT inhibitors (NNRTI). The synthesis of additional compounds of the same class revealed a structure-activity relationship. The most potent compound of the series, BCH-1, had similar antiviral activity to the licensed NNRTI nevirapine against laboratory strains of HIV-1 cultured in cell lines and primary clinical isolates of HIV-1 cultured in peripheral blood mononuclear cells. However, BCH-1 showed greater cytotoxicity, providing a narrow selectivity index in the order of 35. BCH-1 had equivalent antiviral activity against viruses resistant to the nucleoside RT inhibitors zidovudine, didanosine and lamivudine and maintained better activity (less than threefold change in IC50) than nevirapine against viruses resistant to a range of NNRTIs with the single amino acid changes L100I, K103N, E138K or Y181C in the RT. Viruses with single V106A or Y188C amino acid changes showed five- and 10-fold resistance to BCH-1, respectively, in contrast to nevirapine, which had a > 100-fold change in IC50. However, virus with both V106A and Y188C amino acid changes showed higher level resistance (> 15-fold) to BCH-1. Virus with > 10-fold resistance to BCH-1 was rapidly selected for after growth in increasing concentrations of compound and was shown to be cross-resistant to nevirapine. Sequencing of this virus revealed two amino acid changes at positions 179 (V to D) and 181 (Y to C) in the RT. BCH-1 represents a new class of NNRTI, which may act as a lead to identify more selective compounds.