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PubMed2001

Mutations at amino acid positions 63, 189, and 396 of human immunodeficiency virus type 1 reverse transcriptase (RT) partially restore the DNA polymerase activity of a Trp229Tyr mutant RT.

Trp229 is part of the nonnucleoside reverse transcriptase inhibitor (NNRTI)-binding pocket of HIV-1 reverse transcriptase (RT). It is also an important constituent of the so-called "primer grip." Using a recombinant virus assay, we tried to obtain recombinant virus containing a Trp229Phe or a Trp229Tyr mutation in its RT. Previous studies already established the very low DNA polymerase activities of both the Trp229Phe and the Trp229Tyr mutant RT enzymes. We were able to obtain a Trp229Tyr but not a Trp229Phe mutant virus. However, in addition to the Trp229Tyr mutation this mutant virus also contained an Ile63Met, a Val189Ile, and a Glu396Gly mutation in its RT. When we evaluated the quadruple mutant virus for sensitivity/resistance against a variety of NNRTIs, no significant difference with the sensitivity/resistance profile of the single Trp229Tyr mutant RT enzyme could be observed. We found that the three additional mutations partly restored the low RNA- and DNA-dependent DNA polymerase activities of the Trp229Tyr mutant enzyme. Kinetic analysis revealed that both template/primer binding and dNTP incorporation are affected by the Trp229Tyr mutation. Our findings demonstrate that a mutation at position 229 is unlikely to occur under NNRTI drug pressure due to the poor catalytic activity of the singly mutated RT and the favorable drug sensitivity profile of the mutated enzyme/viruses in both the absence and the presence of the compensatory mutations. Therefore, amino acid position 229 may be regarded as an excellent amino acid target within the NNRTI pocket for rational drug design.

Amino Acid Substitution↗

PubMed2006

Cardiovascular risk in patients with HIV Infection: impact of antiretroviral therapy.

Increased coronary heart disease risk in HIV-positive patients using antiretroviral therapy (ART) has been a controversial topic since 1998 when the dyslipidaemic effect of protease inhibitors (PIs) was recognised. Accumulating evidence suggests an association between ART and increased coronary heart disease risk. In 2003, the large, prospective D:A:D (Data Collection on Adverse Events of Anti-HIV Drugs) study reported a 26% relative increase in the rate of myocardial infarction per year of exposure during the first 4-6 years of use. As the HIV-population grows older, infectious disease specialists have to consider unfamiliar areas of internal medicine such as lipid-lowering therapy and smoking cessation. Moreover, the ART regimen itself may be a modifiable risk factor, as there are both class differences and within-class differences in the tendency to increase lipids. Most nucleoside reverse transcriptase inhibitors (NRTIs), including the newer agents tenofovir disoproxil fumarate and emtricitabine, have little or no effect on lipid levels or glucose metabolism. One exception is the highly effective NRTI stavudine, which has a dyslipidaemic profile and a negative effect on glucose metabolism. In contrast the non-nucleoside reverse transcriptase inhibitor nevirapine may increase the 'good cholesterol' high-density lipoprotein (HDL) cholesterol and thus reduce the total cholesterol : HDL cholesterol index. Most of the PIs have some dyslipidaemic effect, especially ritonavir (alone or in combination with other PIs), fosamprenavir and the novel PI tipranavir. Only atazanavir, and to some extent saquinavir, seem to have little effect on lipid levels and glucose metabolism. Studies on blood pressure in HIV-positive patients have been contradictory. Apart from a recent report from the D:A:D study where lower blood pressure was found in patients receiving NNRTIs, the influence of the individual drugs on blood pressure is unknown. When hypertension is detected in a HIV-positive patient, creatinine clearance (CL(CR)) should be calculated and the urine checked for proteinuria. When CL(CR) is <30 mL/min, tenofovir disoproxil fumarate is not recommended. Many hypertensive HIV-positive patients have proteinuria and an ACE inhibitor or an angiotensin II receptor antagonist is a better choice than a thiazide diuretic or calcium channel antagonist in these patients. In addition, physicians treating patients with ART should be especially aware of the long list of possible interactions between PIs and anti-hypertensive- and lipid-lowering drugs. This review discusses important clinical aspects of treating middle-aged HIV-positive patients who have an increased risk of experiencing a cardiovascular event.

Anti-Retroviral Agents↗

PubMed1997

New approaches to using antiretroviral therapy for the management of HIV Infection.

OBJECTIVE: To review the changes that have occurred in the past 2 years in the management of HIV infection with antiretroviral agents by contrasting the 1994 with the 1996 Guidelines. DATA SOURCES: Conference proceedings, clinical experience of the author and her colleagues, and English-language articles from the body scientific literature identified via MEDLINE, AIDSLINE, and Current Contents served as data sources. DATA SYNTHESIS: Current antiretroviral management strategies include movement away from using zidovudine monotherapy, institution of combination antiretroviral therapy earlier in HIV diseases, the use of newer agents such as lamivudine, protease inhibitors (i.e., saquinavir, ritonavir, indinavir), and nonnucleoside reverse transcriptase inhibitors (i.e., nevirapine, delavirdine), prevention of vertical transmission with zidovudine, and use of HIV-1 RNA determinations (viral load) to guide the initiation and alteration of antiretroviral therapy. These strategies represent a dramatic change from the 1994 Guideline, which recommended zidovudine monotherapy in nonpregnant and pregnant individuals whose CD4 cell counts were less than 500 cells/mm3, when many of the newer agents were not available and the assays to determine viral load were strictly investigational. CONCLUSIONS: The difference between the 1994 and 1996 Guidelines is substantial. It is likely that within a year's time, newer information on pathogenesis and antiretroviral agents in development will be known and further management strategies will need to be disseminated. Until then, the International AIDS Society--USA Guidelines for 1996 should be followed as the standard of care.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Mitochondrial DNA levels of peripheral blood mononuclear cells and subcutaneous adipose tissue from thigh, fat and abdomen of HIV-1 seropositive and negative individuals.

Mitochondrial dysfunction has been demonstrated in subcutaneous adipose tissue from lipoatrophic HIV-1-infected patients treated with nucleoside reverse transcriptase inhibitors (NRTIs). To further assess mitochondrial toxicity, mitochondrial DNA (mtDNA) copies/cell were measured in subcutaneous fat from various sites. Peripheral adipose tissues were obtained from the abdominal wall near the umbilicus, anterior lateral thigh, and dorsal cervical region of the neck of individuals from four cohorts: 1) seven lipoatrophic HIV-1-infected patients receiving a regimen with nucleoside reverse transcriptase inhibitors (NRTIs) as part of highly active antiretroviral therapy (HAART) for > 6 months; 2) seven non-lipoatrophic HIV-1-infected patients receiving NRTIs-containing HAART; 3) five HIV-1-infected patients on antiretroviral therapy < 2 weeks (naive); 4) and five HIV-1-negative participants. Along with the adipose tissue samples, peripheral blood mononuclear cells (PBMC) were also obtained from each patient for mtDNA depletion examination. Total DNA was isolated and mtDNA copies/cell quantitated by competitive and real-time PCR. MtDNA copies/cell in abdomen, thigh, and neck fat were depleted in lipoatrophic HIV-1 seropositive compared to the seropositive naive and seronegative cohorts. MtDNA copies/cell in thigh and neck fat were also decreased in non-lipoatrophic subjects exposed to NRTIs compared with NRTI-naive and HIV seronegative controls. PBMC values did not differ among the cohorts and there was no correlation with lipoatrophy state or HIV-1 serostatus. Additionally, differences in mtDNA copies/cell were observed in the fat depots from seronegative subjects. Thigh fat mtDNA levels were 45-55% lower than abdomen and neck. These studies help demonstrate that mtDNA levels can vary in different subcutaneous adipose depots suggesting possible metabolic differences.

Adipose Tissue↗

PubMed1999

HIV protease inhibitors: pharmacologic and metabolic distinctions.

In the earlier era of nucleoside analogue antiretroviral therapy, considerations of pharmacologic drug-drug interactions were only a small factor in choosing optimal therapies for patients with HIV infection. However, pharmacologic considerations are critical for selecting and managing the current multiple-drug antiretroviral regimens that include one or more HIV protease inhibitors (HPIs). Each of the available HPIs, both those that are licensed and those still under investigation, has distinct pharmacokinetic and metabolic properties that result in different dosing regimens and potential for interactions with food and other drugs. Although drug interactions are usually considered undesirable, some of the drug interactions between HPIs have beneficial effects on drug levels and total drug exposure. The non-nucleoside reverse transcriptase inhibitors also interact with HPIs. This article briefly reviews pharmacokinetic and metabolic distinctions among the newer antiretroviral agents, especially HPIs, up to the end of 1997, including selected agents that are still under investigation. As current treatment guidelines emphasize, HIV/AIDS patients typically receive several drugs; therefore, the potential for drug interactions, particularly those mediated by the P450 system in patients receiving HPIs or non-nucleoside reverse transcriptase inhibitors or both, must be appreciated by all physicians who care for patients with HIV disease.

Animals↗

PubMed2003

Tenofovir disoproxil fumarate.

OBJECTIVE: To review the pharmacology, virology, pharmacokinetics, efficacy, safety, resistance profile, and clinical use of tenofovir disoproxil fumarate. DATA SOURCES: A MEDLINE search was performed (1966-August 2002) using the following terms: tenofovir, tenofovir disoproxil fumarate, PMPA (9-(R)-[2-(phosphonomethoxy)propyl]adenine), and Viread. Abstracts from HIV-related meetings were reviewed. DATA EXTRACTION AND STUDY SELECTION: Publications and meeting abstracts regarding tenofovir were reviewed. The most recent and pertinent items were included. DATA SYNTHESIS: Tenofovir disoproxil fumarate is a nucleotide prodrug that is diphosphorylated to its active moiety, tenofovir diphosphate. In this form, tenofovir acts as a reverse transcriptase inhibitor to inhibit HIV-1 replication. In clinical trials, tenofovir was effective at suppressing HIV-1 RNA and boosting CD4+ cell counts. Tenofovir has a long intracellular half-life, which permits once-daily dosing. Since tenofovir does not interact with the cytochrome P450 pathway, it exhibits minimal drug interactions, with the exception of didanosine. Compared with other reverse transcriptase inhibitors, tenofovir may have advantages in terms of toxicity and medication adherence profiles. Ongoing studies are also analyzing tenofovir's activity against hepatitis B virus. CONCLUSIONS: Tenofovir has been shown to be active against HIV-1 in combination with other antiretrovirals. The drug's benefit as a single-agent intensifier of highly active antiretroviral therapy in treatment-experienced patients has been established, and preliminary data for treatment-naïve patients are encouraging.

Adenine↗

PubMed2006

Optimization of pyrimidinyl- and triazinyl-amines as non-nucleoside inhibitors of HIV-1 reverse transcriptase.

Non-nucleoside inhibitors of HIV-1 reverse transcriptase are being pursued through synthesis and assaying for anti-viral activity. Following computational analyses, the focus has been on the motif Het-NH-Ph-U, where Het is an aromatic heterocycle and U is an unsaturated, hydrophobic group. Previous investigations with Het=2-thiazoyl and 2-pyrimidinyl are extended here to triazinyl derivatives. The result is several NNRTIs in the 2-20 nM range with negligible cytotoxicity and auspicious predicted pharmacological properties.

Amines↗

PubMed1997

The use of new antiretroviral therapy in combination with chemotherapy.

With rapid scientific advances in HIV pathogenesis and antiretroviral therapy, the oncologist is faced with new challenges in the treatment of patients with HIV infection and malignancy. HIV infection, by causing immune dysregulation and cytokine production, may alter the natural history of certain neoplasms. Treatment of cancer with chemotherapy can also affect the course of HIV disease. The use of combination antiretroviral agents, particularly the protease inhibitors, can maximally suppress replication of HIV. Improved clinical outcome is associated with more profound decreases in plasma HIV RNA, although development of resistant strains may hinder sustained antiretroviral activity. Antiretroviral therapy should be continued during chemotherapy with the goal of achieving plasma HIV-RNA levels below 500 copies/mL. Modifications in the regimen should be done when intolerable toxicity occurs or if viral load is increased. Although information regarding the use of newer antiretroviral agents with chemotherapy is limited, the use of several reverse transcriptase inhibitors has been well tolerated in patients with AIDS-related malignancies such as Kaposi's sarcoma and lymphoma.

Anti-HIV Agents↗

PubMed1996

Highly favorable antiviral activity and resistance profile of the novel thiocarboxanilide pentenyloxy ether derivatives UC-781 and UC-82 as inhibitors of human immunodeficiency virus type 1 replication.

The novel human immunodeficiency virus type 1-specific thiocarboxanilide derivatives that contain either a substituted furanyl (UC-781) or thienyl (UC-82) ring linked to the thiocarboxy group and a pentenyloxyether chain linked to the 4-chlorophenyl ring in meta position show highly favorable antiviral properties. Compounds UC-781 and UC-82 discovered by scientists at Uniroyal Chemical Ltd. proved to be > or = 5-10-fold more inhibitory to wild-type human immunodeficiency virus type 1 strains (EC50 approximately 0.002 microgram/ml) than the thiocarboxanilide oxime ether UC-10 and other non-nucleoside reverse transcriptase inhibitors such as nevirapine, bis(heteroaryl)piperazine, and tetrahydroimidazo[4,5,l-jk][1,4]-benzodiazepin-2(1H)-one. In addition, the compounds were able to knock out virus replication in cell culture at concentrations that were 20-50-fold lower than those of nevirapine or bis(heteroaryl)piperazine. They were also highly efficient (EC50 < or = 0.02 microgram/ml) in suppressing the replication of mutant virus strains that contained mutations in their reverse transcriptase that conferred resistance to other non-nucleoside reverse transcriptase inhibitors (i.e., Tyr181 to Cys, Lys103 to Asn, Val106 to Ala, and Leu100 to Ile). The compounds selected for virus mutants that were only marginally resistant to the thiocarboxanilides ( < 10-20-fold). The antiviral activity of the compounds was only slightly affected by the presence of high concentrations of human serum, and the compounds were shown to be highly stable in the presence of human serum for at least 24 hr at room temperature.

Anilides↗

PubMed2003

The effect of HAART and HCV infection on the development of hyperglycemia among HIV-infected persons.

OBJECTIVE: To examine the prevalence and incidence of hyperglycemia among HIV-infected patients by hepatitis C virus (HCV) infection and type of highly active antiretroviral therapy (HAART). DESIGN Retrospective cohort analysis of 1230 persons on their first HAART regimen who had at least 1 random glucose measurement before and during antiretroviral therapy. METHODS: The prevalence of hyperglycemia and the incidence of hyperglycemia were compared among persons with and without HCV infection while on a protease inhibitor (PI)-containing HAART regimen, a nonnucleoside reverse transcriptase inhibitor (NNRTI)-containing regimen, or a regimen that contained both a PI and an NNRTI. Hyperglycemia was defined as either 2 random glucose levels > 11.1 mM (200 mg/dL) or documentation of the diagnosis of diabetes in the medical record. RESULTS: The prevalence of hyperglycemia was significantly higher in HCV-coinfected (5.9%) than HCV-uninfected persons (3.3%, P = 0.02). Among persons receiving HAART, both HCV coinfection (adjusted relative hazard [ARH], 2.28; 95% CI, 1.23-4.22) and PI use (ARH, 5.02; 95% CI, 1.39-18.16) were independent risk factors of developing hyperglycemia. The incidence of hyperglycemia was highest among HCV-coinfected persons receiving a PI (5.6 cases per 100-person years) and only 1 person who was neither HCV-infected nor receiving a PI developed hyperglycemia. CONCLUSION: In this urban HIV cohort, the risk of hyperglycemia was increased in HCV-coinfected patients and those prescribed a PI.

Adult↗

PubMed2004

Relative free energy of binding and binding mode calculations of HIV-1 RT inhibitors based on dock-MM-PB/GS.

Tetrahydroimidazo-[4,5,l-jk][1,4]-benzodiazepin-2-(1H)-one (TIBO) derivatives are important nonnucleoside human immunodeficiency virus-1 reverse transcriptase inhibitors (NNRTI). Several TIBO derivatives have shown high potency to inhibit reverse transcriptase (RT) and one (Tivirapine) has entered into clinical trials. The free energy of binding (FEB) is a numerical way to express the binding affinity of a ligand to its receptor and has been applied in screening candidates in rational drug design. In this work, the FEB of 42 TIBOs in RT was studied. Relative FEB is expressed in the form of a linear combination of vdW, electrostatic, solvation, and nonpolar solvation energy terms. The predicted FEB activity of the TIBOs studied has a good correlation (r(2) = 0.8680, q(2) = 0.8298) with respect to the experimental activity (pIC(50)). Based on the data reported here, the Finite Difference Poisson Boltzmann with a Gaussian Smooth Dielectric Constant Function method (PB/GS) solvation energy term is very important in predicting the binding affinity of TIBOs in RT. In summary, the Dock-Molecular Mechanics (MM)-PB/GS method is a promising technique in predicting ligand/receptor binding affinity and it can be used to screen relatively large sets of molecules in a reasonable amount of computer time.

Anti-HIV Agents↗

PubMed2002

Synthesis of substituted diarylmethylenepiperidines (DAMPs), a novel class of anti-HIV agents.

Substituted diarylmethylenepiperidines (DAMPs) were synthesized as conformationally restricted analogues of the alkenyldiarylmethane (ADAM) class of non-nucleoside reverse transcriptase inhibitors (NNRTIs). Although, like the ADAMs, the DAMPs were found to inhibit the cytopathic effect of HIV-1(RF) in CEM-SS cells, they were completely inactive as inhibitors of HIV-1 reverse transcriptase. The DAMPs were assessed for inhibition of HIV attachment and fusion. DAMP was active in both assays with IC(50) values of 26.5 microM (TI 3.8) and 12.1 microM (TI: >8), respectively. DAMP also inhibited HIV fusion with an IC(50 )12.8 microM (TI: >6), but not virus attachment. However, attempts to verify inhibition of virus attachment and fusion as antiviral targets using time-of-addition experiments failed to confirm these observations, and instead identified an antiviral target occurring after completion of reverse transcription. DAMPs, and were found to inhibit virus replication if added 8 h post virus exposure, and DAMP was equipotent at inhibition of virus replication if added 24 h after virus addition. DAMPs, and did not inhibit virus replication in TNF-alpha induced latently infected U1 cells, a model for post-integrative antiviral targets. When tested in both 3' end-processing and strand-transfer assays in the presence of HIV-1 integrase, none of the DAMPs showed any inhibitory activity, indicating that HIV-1 integrase is not involved in the mechanism of the antiviral action. Thus, the DAMPs are novel conformationally restricted analogues of the previously published ADAM series with an unidentified antiviral target bounded by the completion of reverse transcription and virus integration.

Anti-HIV Agents↗

PubMed2003

Tenofovir disoproxil fumarate (Viread) for the treatment of HIV infection.

Tenofovir disoproxil fumarate (Viread) is the first nucleotide analog reverse transcriptase inhibitor to be approved by the Food and Drug Administration for the treatment of HIV infection. It is a potent agent with a long intracellular half-life that allows for once-daily dosing. It has been well-tolerated in clinical trials to date, without evidence of long term toxicity, including the mitochondrial toxicity that has been associated with some nucleoside analog reverse transcriptase inhibitors. Since its approval in October 2001, tenofovir disoproxil fumarate has quickly become a widely used component of antiretroviral regimens for both treatment-naive and -experienced patients.

Adenine↗

PubMedDate not supplied

Synergistic antiviral effect of PEG-asparaginase (ONCASPAR), with protease inhibitor alone and in combination with RT inhibitors against HIV-1 infected T-cells: a model of HIV-1-induced T-cell lymphoma.

We evaluated the anti-HIV-1 activity of the T-cell-specific protein inhibitor PEG-asparaginase (PEG-ASNase) in human HIV-1-infected T-cells. We further examined the drug synergism between PEG-ASNase and the protease inhibitor Saquinavir (SAQ), both alone and in combination with nucleoside analog reverse transcriptase inhibitors (NRTI). Our drug synergism studies served as a model for an HIV-induced T-cell lymphoma. Phytohemagglutinin [PHA(+)] stimulated T-cells were infected with HIV-1 and then treated with one or more drugs 90 minutes from the viral exposure. To measure inhibition of viral replication, we examined HIV-1 RT and HIV-1 RNA in the supernatant and intracellularly on day 7 post-infection and drug treatment. Last, we examined the effect of administering drugs immediately after HIV-1 infection of T-cells to simulate treatment after an accidental exposure to the virus. PEG-ASNase, even when used alone, has anti-HIV-1 activity in PHA(+)-stimulated T-cells due to inhibition of protein synthesis. When the drug was used with SAQ, the combination was synergistic in inhibiting HIV-1 RT and RNA in the supernatant and intracellularly by 2.5 log10 in comparison with controls. PEG-ASNase and SAQ were even more effective in inhibiting HIV-1 replication when combined with the NRTI inhibitors azidothymidine (AZT) and (-)-beta-2',3'-dideoxy-3'-thiacytidine (3TC, lamivudine). The addition of ribonucleotide reductase inhibitor, 2-methyl-1H-isoindole-1,3-dione (MISID), further potentiated the antiviral effect of the regimen. HIV-1 RT and RNA analyses showed that the administration of the PEG-ASNase + SAQ drug combination immediately following exposure to HIV-1 completely inhibited the infection of T-cells in our in vitro T-cell model. From these results we conclude that PEG-ASNase is a valuable T-cell-specific protein inhibitor against HIV-1 infection, when used singly or in combination with a protease inhibitor, an RT inhibitor and an RR inhibitor. Since PEG-ASNase is a drug of choice for the treatment of T-cell lymphomas, a combination regimen containing PEG-ASNase could be very effective in the treatment of HIV-1-induced T-cell lymphoma and possibly AIDS. Future studies are needed in HIV-infected and/or HIV-induced T-cell lymphoma patients to investigate these findings.

Antineoplastic Agents↗

PubMed2002

Impact of NNRTI compared to PI-based highly active antiretroviral therapy on CCR5 receptor expression, beta-chemokines and IL-16 secretion in HIV-1 infection.

Interleukin-16 (IL-16) and the beta-chemokines (RANTES, monocyte chemotactic protein-1 (MCP-1), macrophage inhibitory protein (MIP)-1alpha and (MIP)-1beta) are soluble in vitro suppressors of macrophage tropic HIV-1 strains. The reduction of HIV-1 RNA plasma levels in late-stage patients receiving protease inhibitors has been associated with increased concentrations of MIP-1alpha, MIP-1beta, RANTES and IL-16 and a decrease in levels of MCP-1. We determined plasma levels of MCP-1, MIP-1alpha, MIP-1beta, RANTES and IL-16 during the first 16 weeks of highly active antiretroviral therapy (HAART) in chronic HIV-1-infected patients. Patients were administered one of two therapeutic regimens based on either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI). No differences were seen in the levels of RANTES and IL-16 over the first 16 weeks of HAART in either treatment group. MCP-1 decreased significantly in the PI-treated group over the first 16 weeks of HAART (P = 0.0003). A significant increase was observed in the levels of MIP-1alpha and MIP-1beta in the NNRTI cohort (P = 0.0010 and P = 0.0012, respectively). A significant decrease in levels of MIP-1alpha and MIP-1beta (P = 0.0015 and P = 0.0299, respectively) was observed over the 16 weeks in the PI cohort. A significant difference was seen when the levels of MIP-1alpha and MIP-1beta were compared between the NNRTI and the PI cohorts at week 16 (P = 0.04 and P = 0.05, respectively). Evaluation of CCR5 expression ex vivo revealed no difference between the two treatment groups. Patients were genotyped for CCR5 Delta32 and the incidence of heterozygosity was lower than in the HIV-1 seronegative controls (3% compared to 19%).

Adult↗

PubMed1998

Saquinavir. Clinical pharmacology and efficacy.

Saquinavir is an HIV protease inhibitor with no, or limited, effect on the activity of other structurally related human aspartic proteinases. As with other HIV protease inhibitors, saquinavir inhibits the cleavage of the gag-pol protein substrate leading to the release of structurally defective and functionally inactive viral particles. It is active on both HIV-1 and HIV-2, and also has activity on chronically infected cells and HIV strains resistant to reverse transcriptase inhibitors. Synergy of action has been observed with other antiretroviral drugs. Saquinavir is characterised by a low bioavailability which is further reduced in the fasting state. Metabolism is mainly hepatic through cytochrome P450 (CYP) 3A4, but intestinal metabolism through the same system has also been reported. To achieve higher drug plasma concentrations and increase the antiviral effect, a new formulation of saquinavir with a higher bioavailability has recently been introduced. Higher plasma drug concentrations may also be obtained by combining the drug with CYP blockers, such as ritonavir or ketoconazole. Because of its metabolic interference with the CYP system, saquinavir cannot be coadministered with astemizole, terfenadine or cisapride. Rifampicin (rifampin) is also contraindicated because coadministration can lead to decreases in saquinavir concentrations. Interactions have also been reported with other drugs metabolised through the same system, including non-nucleoside reverse transcriptase inhibitors and HIV protease inhibitors. Resistance has been observed after both in vitro and in vivo drug exposure, with a relatively specific mutation profile compared with other protease inhibitors. Saquinavir is generally well tolerated, with mild gastrointestinal symptoms representing the most commonly observed adverse effects. Although characterized by low bioavailability, in phase III trials saquinavir has been shown to have clinical efficacy in terms of survival and progression rate. As with the other protease inhibitors, saquinavir should be used in combination with other antiretroviral drugs. Current therapeutic guidelines, however, recommend the selection of an initial treatment regimen with other protease inhibitors with higher in vivo activity in terms of RNA and CD4 response. The results of ongoing studies will clarify to what extent a new saquinavir formulation, recently introduced, is superior to the previous one in terms of antiviral activity and to provide comparisons with other protease inhibitors. Further studies are also needed to define the best place of saquinavir within treatment strategies based on protease inhibitors, particularly in respect to the optimal sequence for its use with other protease inhibitors, and the dynamics of cross-resistance and its role within regimens based on the combination of protease inhibitors.

Anti-HIV Agents↗

PubMed2004

Binding of anti-HIV drugs to human serum albumin.

Human serum albumin (HSA), the most prominent protein in plasma, is best known for its exceptional ligand (i.e., drug) binding capacity. Here, values of the dissociation equilibrium constant (Kd)for the binding of HIV protease and reverse transcriptase inhibitors to HSA are reported. The binding of abacavir, atazanavir,didanosine, efavirenz, emtricitabine, lamivudine, nelfinavir,nevirapine, ritonavir, saquinavir, stavudine, zalcitabine, and zidovudine to the Sudlow site I (i.e., the warfarin cleft) located in the subdomain IIA involves the alteration of the HSA structure around Trp214 and induces intrinsic tryptophan fluorescence quenching. Accordingly, ibuprofen that primarily binds to the Sudlow site II located in the subdomain IIIA does not affect the HSA intrinsic tryptophan fluorescence and the binding of anti-HIV drugs to the Sudlow site 1. Accounting for the physiological concentration of HSA (= 7.0 x 10(-4) M), the average anti-HIV drug concentration in plasma (= 1.0 x 10(-4) M), and Kd values for the binding of anti-HIV drugs to HSA (ranging between 4.4 x 10(-5)M and 3.8 x 10(-4) M), it appears that the fraction of HIV protease and reverse transcriptase inhibitors bound to HSA ranges between 63% and 91%. This represents a significant drawback in the anti-HIV therapy and management, the anti-HIV drug concentration required to achieve 90% protease and reverse transcriptase inhibition in the presence of plasma proteins appears to be at least one order of magnitude higher than that required in their absence.

Anti-HIV Agents↗

PubMed1998

New antiretrovirals and new combinations.

The appearance in the clinic of two to three new antiretroviral agents yearly since 1995 has permitted unprecedented advances in HIV treatment. This remarkable pace of drug development is a testimony to an extraordinary international effort involving scientists, clinicians, governments, community activists and industry dedicated to the rapid and safe development of novel therapies. New drugs present the opportunity to improve HIV therapy. They also create an enormous challenge to the clinician, who must constantly assimilate data on new drugs and incorporate this information into practical management strategies. Combination therapy has proven the most effective approach to treat HIV disease. The profound and sustained viral suppression achievable with combinations such as indinavir (IDV), lamivudine (3TC) and zidovudine (ZDV) have resulted in a dramatic shift in HIV treatment paradigms over the last year. The full potential of combination therapy with available drugs has yet to be realized as only a limited number of the possible combinations incorporating new drugs have been fully tested. Even drugs available for many years may have untapped potential. Didanosine (ddI) and stavudine (d4T), once thought to be contraindicated in combination because of their overlapping peripheral neuropathy toxicity, have proven well tolerated and effective. Combination therapy can increase antiviral suppression, prevent drug resistance, optimize drug exposure and simplify dosing, but it can also result in pharmacologic antagonism, subtherapeutic drug concentrations and unexpected toxicities. Clinical studies have confirmed in vitro studies showing pharmacologic antagonism for the combination of ZDV and d4T. Combining protease inhibitors with each other or with non-nucleoside reverse transcriptase inhibitors is complicated by effects both classes of drugs have on drug metabolism and clearance. These observations underline the importance of carefully conducted clinical studies to characterize safety, pharmacokinetics and efficacy of combination therapies. In this review, we will first summarize the clinical profile of new drugs which either became commercially available last year [nelfinavir, nevirapine, delavirdine (DLV)] or are in the late stages of clinical development (DMP-266, abacavir and 141W94). Later we will summarize new data on nucleoside, protease inhibitor and non-nucleoside reverse transcriptase combination regimens. Finally, we will briefly mention new drugs in early stages of development.

Anti-HIV Agents↗