The antiretroviral agents azidothymidine, stavudine, and didanosine have the identical mutational fingerprint in the rpoB region of Escherichia coli

We looked at the mutational fingerprints of three antiretroviral (anti-HIV) agents, azidothymidine (AZT), stavudine (STAV), and didanosine (DIDA) in the rpoB system of Escherichia coli and compared them with each other and with the fingerprints of trimethoprim and of spontaneous mutations in a wild-type and a mutT background. All three agents gave virtually identical fingerprints in the wild-type background, causing only A:T→C:G changes at 3 of the 12 A:T→C:G possible sites among the total of 92 possible base substitution mutations, even though AZT and STAV are thymidine analogs but DIDA is an adenosine analog. As all three agents are reverse transcriptase inhibitors, and act as chain blockers, the common fingerprint may be a property of chain blocking agents.

Nucleoside Analogues Are Potent Inducers of Pol V-mediated Mutagenesis

Drugs targeting DNA and RNA in mammalian cells or viruses can also affect bacteria present in the host and thereby induce the bacterial SOS system. This has the potential to increase mutagenesis and the development of antimicrobial resistance (AMR). Here, we have examined nucleoside analogues (NAs) commonly used in anti-viral and anti-cancer therapies for potential effects on mutagenesis in Escherichia coli, using the rifampicin mutagenicity assay. To further explore the mode of action of the NAs, we applied E. coli deletion mutants, a peptide inhibiting Pol V (APIM-peptide) and metabolome and proteome analyses. Five out of the thirteen NAs examined, including three nucleoside reverse transcriptase inhibitors (NRTIs) and two anti-cancer drugs, increased the mutation frequency in E. coli by more than 25-fold at doses that were within reported plasma concentration range (Pl.CR), but that did not affect bacterial growth. We show that the SOS response is induced and that the increase in mutation frequency is mediated by the TLS polymerase Pol V. Quantitative mass spectrometry-based metabolite profiling did not reveal large changes in nucleoside phosphate or other central carbon metabolite pools, which suggests that the SOS induction is an effect of increased replicative stress. Our results suggest that NAs/NRTIs can contribute to the development of AMR and that drugs inhibiting Pol V can reverse this mutagenesis.

Computational drug re-purposing targeting the spike glycoprotein of SARS-CoV-2 as an effective strategy to neutralize COVID-19

COVID-19 has intensified into a global pandemic with over a million deaths worldwide. Experimental research analyses have been implemented and executed with the sole rationale to counteract SARS-CoV-2, which has initiated potent therapeutic strategy development in coherence with computational biology validation focusing on the characterized viral drug targets signified by proteomic and genomic data. Spike glycoprotein is one of such potential drug target that promotes viral attachment to the host cellular membrane by binding to its receptor ACE-2 via its Receptor-Binding Domain (RBD). Multiple Sequence alignment and relative phylogenetic analysis revealed significant sequential disparities of SARS-CoV-2 as compared to previously encountered SARS-CoV and MERS-CoV strains. We implemented a drug re-purposing approach wherein the inhibitory efficacy of a cluster of thirty known drug candidates comprising of antivirals, antibiotics and phytochemicals (selection contingent on their present developmental status in underway clinical trials) was elucidated by subjecting them to molecular docking analyses against the spike protein RBD model (developed using homology modelling and validated using SAVES server 5.0) and the composite trimeric structures of spike glycoprotein of SARS-CoV-2. Our results indicated that Camostat, Favipiravir, Tenofovir, Raltegravir and Stavudine showed significant interactions with spike RBD of SARS-CoV-2. Proficient bioavailability coupled with no predicted in silico toxicity rendered them as prospective alternatives for designing and development of novel combinatorial therapy formulations for improving existing treatment regimes to combat COVID-19.

Risk Factors for Hyperlactataemia in HIV-Infected Patients, Aquitaine Cohort, 1999–2003

The objectives of our study were to describe the characteristics of a subset of patients who had been prescribed serum lactate in clinical practice within a large cohort of HIV-infected patients and to determine the factors associated with hyperlactataemia. Hyperlactataemia (⩾T2 mmol/l) was found in 219 [29% (95% confidence interval: 25.3–31.7)] of the 768 HIV-infected participants. In multivariate analysis (logistical regression), an increased risk of hyperlactataemia was associated with increasing age, CD4 count <500/mm3, triglycerides >2.2 mmol/L, lipoatrophy and stavudine use. In a second model coding for the NRTI-based drug combinations, only those including stavudine were associated with an increased risk of hyperlactataemia. In a third model including exposure duration to NRTIs, we estimated a 20% increased risk of hyperlactataemia per year of exposure to didanosine or stavudine. The risk of hyperlactataemia could increase over time in patients treated with these drugs and is also closely associated with increased age, decreased CD4 count, lipodystrophy and increased plasma triglycerides. It could be proposed that patients having one or more of these risk factors undergo regular monitoring of plasma lactate and renal function to prevent lactic acidosis.

Reductions in Stavudine Dose Might Ameliorate Mitochondrial-Associated Complications Without Compromising Antiviral Activity

BACKGROUND

Stavudine (d4T) is a nucleoside analogue approved for the treatment of HIV infection. Concern has risen due to its association with mitochondrial toxicity. Given that the toxicity might be dose-dependent, we explored prospectively whether lowering d4T doses might improve the safety profile of the drug without compromising its antiviral activity.

METHOD

All HIV-infected patients seen at our institution during the first semester of year 2003 who were receiving a d4T-containing regimen and had plasma HIV RNA below 50 copies/mL for the previous 3 months were invited to participate in a trial in which half of patients reduced the dose of d4T from 40 to 30 mg bid (cases) and the other half continued with the same d4T dose (controls).

RESULTS

A total of 92 patients were recruited in the study: 47 cases and 45 controls. A total of 9 patients experienced virological failure during the following 12 months: 4 cases and 5 controls. No significant differences between groups were recognized for mean transaminase levels, cholesterol, triglycerides, and lactate at baseline nor over the 12-month follow-up period. Lipodystrophy was recognized in 20% of patients at baseline, without significant differences between groups, and no significant improvements were recognized in the d4T 30 mg bid arm after 12 months follow-up. However, a median significant increase of 2.23-fold in the mitochondrial DNA content in peripheral blood mononuclear cells (PBMCs) was recognized in a subset of 11 patients who reduced the d4T dose, whereas it remained unchanged in 10 controls.

CONCLUSION

A reduction in the d4T dose from 40 to 30 mg bid may ameliorate mtDNA depletion in PBMCs without compromising the antiviral activity of the drug. However, significant improvements on surrogate laboratory markers of mitochondrial toxicity or in lipoatrophy could not be recognized over 12 months follow-up.

Lipid Profile During Pregnancy in HIV-Infected Women

PURPOSE

We investigated the evolution of serum lipid levels in HIV-infected pregnant women and the potential effect of antiretroviral treatment during pregnancy using data from a national surveillance study.

METHOD

Fasting lipid measurements collected during routine care in pregnancy were used, analyzing longitudinal changes and differences in lipid values at each trimester by protease inhibitors (PIs) and stavudine use. Multivariate analyses were used to control for simultaneous factors potentially leading to hyperlipidemia. Study population included 248 women.

RESULTS

Lipid values increased progressively and significantly during pregnancy: mean increases between the first and third trimesters were 141.6 mg/dL for triglycerides (p < .001), 60.8 mg/dL for total cholesterol (p < .001), 13.7 mg/dL for HDL cholesterol (p < .001), and 17.8 mg/dL for LDL cholesterol (p = .001). At all trimesters, women on PIs had significantly higher triglyceride values compared to women not on PIs. The effect of PIs on cholesterol levels was less consistent. Stavudine showed a dyslipidemic effect at first trimester only. Multivariate analyses confirmed these observations and suggested a potential role of other cofactors in the development of hyperlipidemia during pregnancy.

CONCLUSION

The changes observed point to the need to further explore the causes and the clinical correlates of hyperlipidemia during pregnancy in women with HIV.

Long-term exposure of mice to nucleoside analogues disrupts mitochondrial DNA maintenance in cortical neurons

Nucleoside analogue reverse transcriptase inhibitor (NRTI), an integral component of highly active antiretroviral therapy (HAART), was widely used to inhibit HIV replication. Long-term exposure to NRTIs can result in mitochondrial toxicity which manifests as lipoatrophy, lactic acidosis, cardiomyopathy and myopathy, as well as polyneuropathy. But the cerebral neurotoxicity of NRTIs is still not well known partly due to the restriction of blood-brain barrier (BBB) and the complex microenvironment of the central nervous system (CNS). In this study, the Balb/c mice were administered 50 mg/kg stavudine (D4T), 100 mg/kg zidovudine (AZT), 50 mg/kg lamivudine (3TC) or 50 mg/kg didanosine (DDI) per day by intraperitoneal injection, five days per week for one or four months, and primary cortical neurons were cultured and exposed to 25 µM D4T, 50 µM AZT, 25 µM 3TC or 25 µM DDI for seven days. Then, single neuron was captured from mouse cerebral cortical tissues by laser capture microdissection. Mitochondrial DNA (mtDNA) levels of the primary cultured cortical neurons, and captured neurons or glial cells, and the tissues of brains and livers and muscles were analyzed by relative quantitative real-time PCR. The data showed that mtDNA did not lose in both NRTIs exposed cultured neurons and one month NRTIs treated mouse brains. In four months NRTIs treated mice, brain mtDNA levels remained unchanged even if the mtDNA levels of liver (except for 3TC) and muscle significantly decreased. However, mtDNA deletion was significantly higher in the captured neurons from mtDNA unchanged brains. These results suggest that long-term exposure to NRTIs can result in mtDNA deletion in mouse cortical neurons.

Comparison of tenofovir, zidovudine, or stavudine as part of first-line antiretroviral therapy in a resource-limited-setting: a cohort study

BACKGROUND

Tenofovir (TDF) is part of the WHO recommended first-line antiretroviral therapy (ART); however, there are limited data comparing TDF to other nucleoside reverse transcriptase inhibitors in resource-limited-settings. Using a routine workplace and community-based ART cohort in South Africa, we assessed single drug substitution, HIV RNA suppression, CD4 count increase, loss-from-care, and mortality between TDF, stavudine (d4T) 30 mg dose, and zidovudine (AZT).

METHODS

In a prospective cohort study we included ART naïve patients aged ≥17 years-old who initiated ART containing TDF, d4T, or AZT between 2007 and 2009. For analysis of single drug substitutions we used a competing-risks time-to-event analysis; for loss-from-care, mixed-effect Poisson modeling; for HIV RNA suppression, competing-risks logistic regression; for CD4 count slope, mixed-effects linear regression; and for mortality, proportional hazards modeling.

RESULTS

Of 6,196 patients, the initial drug was TDF for 665 (11%), d4T for 4,179 (68%), and AZT for 1,352 (22%). During the first 6 months of ART, the adjusted hazard ratio for a single drug substitution was 2.3 for d4T (95% confidence interval [CI]: 0.27, 19) and 5.2 for AZT (95% CI: 1.1, 23), compared to TDF; whereas, after 6 months, it was 10 (95% CI: 5.8, 18) and 4.4 (95% CI: 2.5, 7.8) for d4T and AZT, respectively. Virologic suppression was similar by agent; however, CD4 count rise was lowest for AZT. The adjusted hazard ratio for loss-from-care, when compared to TDF, was 1.5 (95% CI: 1.1, 1.9) for d4T and 1.2 (95% CI: 1.1, 1.4) for AZT. The adjusted hazard ratio for mortality, when compared to TDF, was 2.7 (95% CI: 2.0, 3.5) and 1.4 (95% CI: 1.3, 1.5) and for d4T and AZT, respectively.

DISCUSSION

In routine care, TDF appeared to perform better than either d4T or AZT, most notably with less drug substitution and mortality than for either other agent.

The NRTIs lamivudine, stavudine and zidovudine have reduced HIV-1 inhibitory activity in astrocytes

HIV-1 establishes infection in astrocytes and macroage-lineage cells of the central nervous system (CNS). Certain antiretroviral drugs (ARVs) can penetrate the CNS, and are therefore often used in neurologically active combined antiretroviral therapy (Neuro-cART) regimens, but their relative activity in the different susceptible CNS cell populations is unknown. Here, we determined the HIV-1 inhibitory activity of CNS-penetrating ARVs in astrocytes and macrophage-lineage cells. Primary human fetal astrocytes (PFA) and the SVG human astrocyte cell line were used as in vitro models for astrocyte infection, and monocyte-derived macrophages (MDM) were used as an in vitro model for infection of macrophage-lineage cells. The CNS-penetrating ARVs tested were the nucleoside reverse transcriptase inhibitors (NRTIs) abacavir (ABC), lamivudine (3TC), stavudine (d4T) and zidovudine (ZDV), the non-NRTIs efavirenz (EFV), etravirine (ETR) and nevirapine (NVP), and the integrase inhibitor raltegravir (RAL). Drug inhibition assays were performed using single-round HIV-1 entry assays with luciferase viruses pseudotyped with HIV-1 YU-2 envelope or vesicular stomatitis virus G protein (VSV-G). All the ARVs tested could effectively inhibit HIV-1 infection in macrophages, with EC90s below concentrations known to be achievable in the cerebral spinal fluid (CSF). Most of the ARVs had similar potency in astrocytes, however the NRTIs 3TC, d4T and ZDV had insufficient HIV-1 inhibitory activity in astrocytes, with EC90s 12-, 187- and 110-fold greater than achievable CSF concentrations, respectively. Our data suggest that 3TC, d4T and ZDV may not adequately target astrocyte infection in vivo, which has potential implications for their inclusion in Neuro-cART regimens.

From the chemistry of epoxy-sugar nucleosides to the discovery of anti-HIV agent 4'-ethynylstavudine-Festinavir

Branched sugar nucleosides have attracted much attention due to their biological activities. We have demonstrated that epoxysugar nucleosides serve as versatile precursor for the stereo-defined synthesis of these nucleoside derivatives on the basis of its ring opening with organoaluminum or organosilicon reagents. In this review article, novel methods for the synthesis of nucleoside analogues branched at the 1' and 4'-position will be described. During this study, we could discover an anti-HIV agent, 4'-ethynylstavudine (Festinavir). Festinavir showed more potent anti-HIV activity than the parent compound stavudine (d4T). Other significant properties of Festinavir are as follows: 1) much less toxic to various cells and also to mitochondorial DNA synthesis than d4T, 2) better substrate for human thymidine kinase than d4T, 3) resistant not only to chemical glycosidic bond cleavage but also to catabolism by thymidine phosphorylase, 4) the activity improves in the presence of a major mutation, K103N, associated with resistance to non-nucleoside reverse transcriptase inhibitors. Detailed profile of the antiviral activities, biology and pharmacology of Festinavir are also described.

[The influence of long-term nucleotide reverse transcriptase inhibitors on lipids metabolism in HIV/AIDS patients]

OBJECTIVE

To evaluate the influence of long-term nucleotide reverse transcriptase inhibitors (NRTIs) on lipids metabolism in HIV/AIDS patients and correlating clinical factors.

METHODS

A total of 118 HIV/AIDS patients were divided into 3 groups: untreated group (40 patients), highly active antiretroviral therapy (HAART) for 1 - 2 years group (37 patients) and HAART over 5 years group (41 patients), with 20 healthy individuals as the control group. Clinical lipodystrophy (LD) was defined as concordance between patient's report of change and physical examination. Fat mass (FM) was measured by dual-energy X-ray absorptiometry (DXA).

RESULTS

There was no significant difference in the incidence of LD between HAART for 1 - 2 years group and HAART over 5 years group (51.2% vs 40.5%, P = 0.345). The prevalence of LD was 2.4 folds with stavudine (d4T) treatment compared with zidovudine (AZT)-containing regimens (61.6% vs 23.5%, P = 0.001). Based on DXA measurements, FM of total body and limbs were significantly lower in the HAART over 5 years group than that in the control group, the untreated group and the HAART for 1 - 2 years group (P < 0.05). Trunk FM was significantly lower in the HAART over 5 years group than the untreated group and the HAART for 1 - 2 years group (P < 0.05). FM of total body and trunk were significantly lower in patients without LD in the HAART over 5 years group than patients without LD in the HAART for 1 - 2 years group (P < 0.05). FM was correlated positively with body weight and BMI. Limbs FM was correlated negatively with peripheral blood triglyceride concentration.

CONCLUSIONS

HIV/AIDS patients with NRTIs therapy have high prevalence of LD, which mainly occurs 1 - 2 years after therapy, and increases with d4T treatment compared with AZT-containing regimens. There was no significant difference in the incidence of LD between the HAART for 1 - 2 years group and the HAART over 5 years group. FM was significantly decreased after long-term HAART in the patients with or without LD. DXA can evaluate LD objectively and guide further clinical treatment.

Suppression of pre adipocyte differentiation and promotion of adipocyte death by anti-HIV drugs

In the present study, we investigated the ability of anti-HIV drugs to interfere with normal cell cycle progression and to induce oxidative stress by perturbing the redox environment. Our results provide evidence that anti-HIV drugs have a differential effect on adipocyte cell cycle and differentiation, being able to modify the response to oxidative stress through an increase of reactive oxygen species (ROS) that compromises the induction of phase-2 and antioxidant enzymes. In detail, saquinavir, efavirenz, and stavudine exert antiadipogenic influences on the model 3T3-L1 cell line, perturbing the oxidative response and inducing of apoptosis. When considered together, the effects of anti-HIV drugs on 3T3-L1 pre adipocytes are distinct but commonly antiadipogenic, thus suggesting another additional possible mechanism by which antiretroviral therapies could contribute to lipoatrophy.

Effects of daily intake of zidovudine-stavudine on rat pregnancy outcome: biological essay

PURPOSE

To evaluate the effects at term of a highly active antiretroviral drug association when administered for the whole period of rat pregnancy.

METHODS

Forty pregnant rats weighing about 200 g were randomly divided into four groups: a control group (Ctr = drug vehicle control, n=10) and three experimental groups, which were treated with an oral solution of zidovudine-stavudine (Explx = 10/1 mg/kg b.w., n=10; Exp3x = 30/3 mg/kg b.w., n=10; Exp9x = 90/9 mg/kg b.w., n=10) from "day 0" up to the 20th day of pregnancy. Maternal body weights were recorded at the start of the experiment and on the 7th, 14th and 20th day thereafter. At term (20th day) the rats were anesthetized and submitted to hysterotomy. Implantations, reabsorptions, living fetuses, placentae and intrauterine deaths were looked for and recorded. The collected fetuses and placentae were weighed and the concepts were examined by a stereoscopic microscope looking for external malformations.

RESULTS

No significant alterations due to the antiretroviral drug treatment could be detected regarding the number of implantations, fetuses, placentae, absorptions and malformations nor regarding maternal and fetal mortality.

CONCLUSIONS

Administration of the association zidovudine/stavudine for the whole period of rat pregnancy did not interfere with the maternal, fetal and placental weight gain as well as abnormalities detectable by the employed methodology.

Antiretrovirals for HIV Exposure Prophylaxis

Infection with Human Immunodeficiency Virus (HIV) remains a global public health problem. Although the epidemic has not been completely controlled, there was considerable progress in HIV prevention and treatment during the last 30 years. The modern prevention approaches are multi-component including also the administration of combinations of potent antiretroviral agents as a prophylaxis after occupational or non-occupational exposures to HIV. The aim of the current review is to present the chemical and pharmacological characteristics of antiretroviral drugs used in HIV prophylaxis and to describe briefly the medical management of exposures to potentially infectious body fluids.

HIV-1-resistance-associated mutations after failure of first-line antiretroviral treatment among children in resource-poor regions: a systematic review

HIV-positive children are at high risk of drug resistance, which is of particular concern in settings where antiretroviral options are limited. In this Review we explore resistance rates and patterns among children in developing countries in whom antiretroviral treatment has failed. We did a systematic search of online databases and conference abstracts and included studies reporting HIV-1 drug resistance after failure of first-line paediatric regimens in children (<18 years) in resource-poor regions (Latin America, Africa, and Asia). We retrieved 1312 citations, of which 30 studies reporting outcomes in 3241 children were eligible. Viruses with resistance-associated mutations were isolated from 90% (95% CI 88-93%) of children. The prevalence of mutations associated with nucleoside reverse transcriptase inhibitors was 80%, with non-nucleoside reverse transcriptase inhibitors was 88%, and with protease inhibitors was 54%. Methods to prevent treatment failure, including adequate paediatric formulations and affordable salvage treatment options are urgently needed.

[Energetic, conformational and electron density topological properties of 2',3'-didehydro-2',3'-dideoxythymidine: a quantum chemical study]

Comprehensive conformational analysis of 2',3'-didehydro-2',3'-dideoxythymidine (d4T), also known as anti-AIDS drug stavudine, has been performed for the first time at the MP2/6-311++G(d,p)//DFT B3LYP/6-31++G(d,p) level of the theory. It was established that d4T energy landscape contained 19 local minima, which corresponded to stable conformers. Eight types of specific intramolecular interactions, which govern the d4T conformational properties, were identified, namely: O5'H-O2, C1'H'-O2, C6H-O5', C6H-O4', C5'H1'-O2, C5'H2'-O2, C6H-H1'C5', C2'-O2. The obtained results confirm the actual point of view that d4T biological activity is, most likely, connected with termination of the DNA chain synthesis in the 5'-3' direction. Thus, d4T competes with canonical thymidine in binding an active site of HIV-1 reverse transcriptase.

Stavudine entrapped lipid nanoparticles for targeting lymphatic HIV reservoirs

The main objective of present research study was to evaluate the potential of lipid nanoparticles for active delivery of an antiretroviral drug to lymphatic tissues. Stavudine entrapped drug loaded solid lipid nanoparticles (SLNs) were prepared and characterized for a variety of physicochemical parameters such as appearance, particle size, polydispersity index and zeta potential. The targeting potential of the prepared nanoparticles was investigated by carrying out ex vivo cellular uptake studies in macrophages which depicted several times enhanced uptake as compared to pure drug solution. Further, the lymphatic drug levels and organ distribution studies demonstrated efficiency of the developed nanoparticles for prolonged residence in spleenic tissues. Thus it was concluded that stavudine entrapped lipid carriers can be exploited for effective and targeted delivery to cellular and anatomical HIV reservoirs and may ultimately increase the therapeutic safety and reduce side effects.

Stavudine-loaded mannosylated liposomes: in-vitro anti-HIV-I activity, tissue distribution and pharmacokinetics

Cells of the mononuclear phagocyte system (MPS) are important hosts for human immunodeficiency virus (HIV). Lectin receptors, which act as molecular targets for sugar molecules, are found on the surface of these cells of the MPS. Stavudine-loaded mannosylated liposomal formulations were developed for targeting to HIV-infected cells. The mannose-binding protein concanavalin A was employed as model system for the determination of in-vitro ligand-binding capacity. Antiretroviral activity was determined using MT-2 cell line. Haematological changes, tissue distribution and pharmacokinetic studies of free, liposomal and mannosylated liposomal drug were performed following a bolus intravenous injection in Sprague-Dawley rats. The entrapment efficiency of mannosylated liposomes was found to be 47.H ± 1.57%. Protein-carbohydrate interaction has been utilized for the effective delivery of mannosylated formulations. Cellular drug uptake was maximal when mannosylated liposomes were used. MT2 cells treated continuously with uncoated liposomal formulation had p24 levels 8–12 times lower than the level of free drug solution. Further, the mannosylated liposomes have shown p24 levels that were 14–20 and 1.42.3 times lower than the level of free drug and uncoated liposomal formulation treatment, respectively. Similar results were observed when infected MT2 cells were treated overnight. Stavudine, either given plain or incorporated in liposomes, led to development of anaemia and leucocytopenia while mannosylated liposomes overcame these drawbacks. These systems maintained a significant level of stavudine in the liver, spleen and lungs up to 12 h and had greater systemic clearance as compared with free drug or the uncoated liposomal formulation. Mannosylated liposomes have shown potential for the site-specific and ligand-directed delivery systems with desired therapeutics and better pharmacological activity.

Centrosome amplification induced by the antiretroviral nucleoside reverse transcriptase inhibitors lamivudine, stavudine, and didanosine

In cultured cells, exposure to the nucleoside reverse transcriptase inhibitor (NRTI) zidovudine (AZT) induces genomic instability, cell cycle arrest, micronuclei, sister chromatid exchanges, and shortened telomeres. In previous studies, we demonstrated AZT-induced centrosome amplification (>2 centrosomes/cell). Here, we investigate centrosome amplification in cells exposed to other commonly used NRTIs. Experiments were performed using Chinese Hamster ovary (CHO) cells, and two normal human mammary epithelial cell (NHMEC) strains: M99005 and M98040, which are high and low incorporators of AZT into DNA, respectively. Cells were exposed for 24 hr to lamivudine (3TC), stavudine (d4T), didanosine (ddI), and thymidine, and stained with anti-pericentrin antibody. Dose response curves were performed to determine cytotoxicity and a lower concentration at near plasma levels and a 10 fold higher concentration were chosen for the experiments. In CHO cells, there was a concentration-dependent, significant (P < 0.05) increase in centrosome amplification for each of the NRTIs. In NHMEC strain M99005, an NRTI-induced increase (P < 0.05) in centrosome amplification was observed for the high concentrations of each NRTI and the low doses of 3TC and ddI. In NHMEC strain M98040, the high doses of ddI and d4T showed significant increases in centrosome amplification. Functional viability of amplified centrosomes was assessed by arresting microtubule nucleation with nocodazole. In cells with more than two centrosomes, the ability to recover microtubule nucleation was similar to that of unexposed cells. We conclude that centrosome amplification is a consequence of exposure to NRTIs and that cells with centrosome amplification are able to accomplish cell division.

[Establishment of pharmacological evaluation system for non-nucleoside reverse-transcriptase inhibitors resistant HIV-1]

Consistent non-nucleoside reverse-transcriptase inhibitors (NNRTIs) resistant HIV-1 strains occurred due to the clinical use for more than ten years of efavirenz (EFV), nevirapine (NVP), and delavirdine (DLV). In this study, we established nine cell-based pharmacological models according to most NNRTIs-resistant clinical tested strains, Resistant mutations were introduced into vector, pNL4-3.Luc.R-E-, by overlapping PCR. Then, pseudovirions were produced by co-transfection of VSV-G plasmid and pNL4-3.Luc.R-E- -mut. All nine recombinant VSVG/HIV-mut pseudovirions (VSVG/HIV-wt, VSVG/HIV(-K103N), VSVG/HIV(-Y181C), VSVG/HIV(-L100I,K103N), VSVG/HIV(-Y188L), VSVG/HIV(-K103N,Y181C), VSVG/HIV(-K103N,P225H), VSVG/HIV(-K103N,Y188L), VSVG/HIV(-K103N,G109A) and VSVG/HIV(-K103N,V108I)) had high efficient infectivity. Furthermore, they all showed resistant characteristics to EFV and NVP with IC50 changes consisting with clinical reports, not to nucleoside reverse-transcriptase inhibitors (AZT and d4T). This series safe cell-based model, which could be carried out in BSL-2 laboratory, can be used for evaluating NNRTIs candidates.

Synthesis of 5-alkynylated d4T Analogues as Potential HIV-1 Reverse Transcriptase Inhibitors

A series of 2',3'-didehydro-2',3'-dideoxynucleosides substituted with an alkynylhydroxy- (6, 7, 12 and 13) and alkynylamino- (20) groups at the C-5 position were synthesized. All these five target modified nucleosides were tested for anti-human immunodeficiency virus type 1 activity in CEM-SS and MT-4 cells and unfortunately displayed no improvement in antiviral activity.

Microbicides for multidrug-resistant and multitropic HIV-1

The most common mode of acquiring HIV-1 is via sexual transmission across the genital mucosa. Topical microbicides are a promising prevention strategy for the protection against HIV infection and may ultimately have an impact on the global AIDS pandemic. The effectiveness of a microbicide to prevent HIV-1 transmission will depend on the evolutionary and genital transmission dynamics of the viral subtypes, and sexual behavioral characteristics. Contemporary antiretroviral therapy has led to virological failure as a result of HIV-1 reverse transcriptase gene mutations. The transmission of these multidrug-resistant HIV-1 variants, and the superinfection with the same or distinct HIV-1 subtypes and recombination is a formidable hindrance inherent to global microbicide development. Consequently, mechanism-based microbicides targeting both the cell-free and cell-associated HIV-1 variants and subtypes can be expected to have superior clinical efficacy and safety profiles compared with polymeric anionic microbicides. This review describes the discovery of potent anti-HIV-1 agents against multidrug-resistant and multitropic HIV-1 variants with implications for global microbicide development. Stampidine and thiourea non-nucleoside reverse transcriptase inhibitors (NNRTIs) have demonstrated highly potent activity against clinically relevant multidrug-resistant and recombinant HIV-1 isolates spanning different subtypes across several continents. Extensive preclinical studies have shown that stampidine and a candidate thiourea NNRTI (HI-443) have clinical potential as a safe combination microbicide to inhibit, prevent or treat mucosal HIV-1 infections.

Prevalence of and risk factors for HIV-associated neuropathy in Melbourne, Australia 1993-2006

OBJECTIVES

The aim of the study was to describe the prevalence of and risk factors for HIV-associated sensory neuropathy (HIV-SN) in 2006 [the era of stavudine, didanosine and zalcitabine (dNRTI)-sparing highly active antiretroviral therapy (HAART)] and to compare our findings with data obtained in the same clinic in 1993 (pre-HAART) and 2001 (frequent use of dNRTI-containing HAART).

METHODS

This was a cross-sectional comparative study using convenience sampling. HIV-positive adults attending a tertiary referral clinic over a 2-week period were screened for HIV-SN using the AIDS Clinical Trials Group screening tool. HIV-SN was defined as present if the patient had both neuropathic symptoms and abnormal signs. Demographic, clinical, laboratory and treatment data were considered as possible risk factors for HIV-SN, and results were compared with data obtained in the same clinic in 1993 and 2001.

RESULTS

One hundred patients were screened. The prevalence of HIV-SN was 42%, which was unchanged since 2001 (44%) despite a significant reduction in the use of dNRTIs. HIV-SN remained much more common than in 1993 (42% vs 13%; P<0.0001). The only independent associations with HIV-SN in 2006 were increasing patient age and a history of exposure to either stavudine or indinavir. This compares with 1993 when neuropathy was increased in those with Mycobacterium avium complex infection, and 2001 when patient age and use of stavudine and didanosine were the independent associations with HIV-SN in this clinic.

CONCLUSIONS

HIV-SN remained common among ambulatory patients in 2006 (42% prevalence) despite a significant reduction in the use of dNRTIs. In addition to patient age and stavudine exposure, indinavir use may be a risk factor for HIV-SN.

NNRTI-selected mutations at codon 190 of human immunodeficiency virus type 1 reverse transcriptase decrease susceptibility to stavudine and zidovudine

The non-nucleoside reverse transcriptase (RT) inhibitor (NNRTI)-binding pocket of HIV-1 RT spans codons 100-110, 180-190 and 220-240 and mutations in these domains are responsible for HIV-1 NNRTI resistance. Recombinant HIV-1 strains carrying G190S/A/E, G190S+T215Y, T215Y and K103N mutations were constructed to evaluate susceptibility to both NNRTIs and nucleoside RT inhibitors (NRTIs). In addition, purified recombinant RT enzymes were obtained to determine the degree of in vitro inhibition by drugs of both classes. High-level resistance to nevirapine and moderate level resistance to both stavudine and zidovudine were associated with G190S/A/E substitutions. The simultaneous presence of G190S and T215Y decreased stavudine and zidovudine susceptibility more than T215Y alone. On the other hand, G190S was associated with a marked decrease in RT catalytic efficiency, while T215Y showed a more limited effect. Interestingly, the simultaneous presence of G190S and T215Y was associated with a reduction in the impairment of the G190S-mutated enzyme. Mutations in the HIV-1 RT NNRTI binding pocket may be associated with cross-resistance to NRTI. Selection of double mutants, with further decrease in NRTI susceptibility, might be favoured by the compensatory effect of T215Y on the reduction of RT catalytic efficiency associated with G190S.

The excision mechanism in reverse transcriptase: pyrophosphate leaving and fingers opening are uncoupled events with the analogues AZT and d4T

We conducted molecular dynamics simulations of complexes of HIV-1 reverse transcriptase (RT) with the substrate and the antiretrovirals AZT and d4T for which resistance emerges via the excision mechanism. It is currently believed that excision results from the inability of AZT to translocate to the P site because of the steric hindrances imposed by the azide group. However, such explanation is far from satisfactory as d4T does not have such steric hindrances and still suffers from excision. Such contradiction motivated us for the present study. The results point to a new explanation for excision. RT preferably excises these inhibitors over the substrate as a consequence of a different pattern of hydrogen bridges they establish with the N site after incorporation. In the complexes with normal nucleotides, the fingers residues K65 and R72 establish hydrogen bonds mainly with the leaving PPi. With the inhibitors, those same residues establish hydrogen bonds primarily with the substituted nucleotides. Consequently, pyrophosphate is eliminated before the opening of the fingers domain, which allows ATP binding, with subsequent excision and development of drug resistance.

Novel drug resistance pattern associated with the mutations K70G and M184V in human immunodeficiency virus type 1 reverse transcriptase

We describe an unusual pathway of human immunodeficiency virus type 1 reverse transcriptase resistance during therapy with tenofovir-emtricitabine, characterized initially by the mutations K70E and M184V and later by K70G and M184V, with the two mutations coexisting on the same viral genome. Phenotypic resistance to lamivudine, emtricitabine, abacavir, didanosine, and tenofovir was observed, whereas susceptibility to zidovudine and stavudine was preserved.

Intracellular metabolism and persistence of the anti-human immunodeficiency virus activity of 2',3'-didehydro-3'-deoxy-4'-ethynylthymidine, a novel thymidine analog

The therapeutic benefits of current antiretroviral therapy are limited by the evolution of drug-resistant virus and long-term toxicity. Novel antiretroviral compounds with activity against drug-resistant viruses are needed. 2',3'-didehydro-3'-deoxy-4'-ethynylthymidine (4'-Ed4T), a novel thymidine analog, has potent anti-human immunodeficiency virus (HIV) activity, maintains considerable activity against multidrug-resistant HIV strains, and is less inhibitory to mitochondrial DNA synthesis in cell culture than its progenitor stavudine (D4T). We investigated the intracellular metabolism and anti-HIV activity of 4'-Ed4T. The profile of 4'-Ed4T metabolites was qualitatively similar to that for zidovudine (AZT), with the monophosphate metabolite as the major metabolite, in contrast to that for D4T, with relatively poor formation of total metabolites. The first phosphorylation step for 4'-Ed4T in cells was more efficient than that for D4T but less than that for AZT. The amount of 4'-Ed4T triphosphate (4'-Ed4TTP) was higher than that of AZTTP at 24 h in culture. There was a dose-dependent accumulation of 4'-Ed4T diphosphate and 4'-Ed4TTP on up-regulation of thymidylate kinase and 3-phosphoglycerate kinase expression in Tet-On RKO cells, respectively. The anti-HIV activity of 4'-Ed4T in cells persisted even after 48 h of drug removal from culture in comparison with AZT, D4T, and nevirapine (NVP). The order of increasing persistence of anti-HIV activity of these compounds after drug removal was 4'-Ed4T > D4T > AZT > NVP. In conclusion, with the persistence of 4'-Ed4TTP and persistent anti-HIV activity in cells, we anticipate less frequent dosing and fewer patient compliance issues than for D4T. 4'-Ed4T is a promising antiviral candidate for HIV type 1 chemotherapy.

Polymorphisms and drug resistance analysis of HIV-1 CRF01_AE strains circulating in Fujian Province, China

BACKGROUND

The database of genotypic drug resistance mutations in HIV-1 subtype B circulating in developed industrial countries has been well established; however, little is known regarding the prevalence of genotypic resistance patterns in patients harboring non-subtype-B HIV-1 variants in most Asian countries.

OBJECTIVE

To characterize the polymorphisms and emergence of drug-resistance mutations, resistance to antiretroviral drugs in naïve and pretreated patients infected with HIV-1 CRF01_AE isolates in Fujian province, China.

METHODS

HIV-1 pol amplicons from 52 pre- and 14 post-treatment samples were obtained by reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. All of the 14 antiretroviral-treated patients were under a fixed regimen of stavudine (d4T), lamivudine (3TC) and nevirapine (NVP), and they had been on treatment for a mean of 6 months (SD, 4 months). The sequence data were analyzed using the Bioedit software, and the data regarding drug resistance mutations were obtained using the Stanford software ( http://hivdb.stanford.edu ).

RESULTS

In comparison with the consensus sequence of B strains, the most common protease polymorphisms in HIV-1 CRF01_AE strains prevailing in Fujian Province, China, were I13V (76.9%), E35D (76.9%), M36I (100%), R41K (98.1%), H69K (90.4%), and L89M (96.2%). Protease mutations between CRF01_AE strains and B' variants prevailing in China were observed. The proportion of substitutions L63P, A71T/V, V77I and I93L in subtype B' sequences was considerably higher than in CRF01_AE viruses, while the proportion of L10I, M36I and K20R/I substitutions in subtype B' sequences was relatively lower than in CRF01_AE strains. A high level of resistance to nucleoside reverse transcriptase inhibitors (NRTIs) (28.6%, 4/14) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) (35.7%, 5/14) was found in treatment-experienced patients. High-level resistance to nevirapine (NVP) and lamivudine (3TC) was found in the stavudine/lamivudine/nevirapine (d4T/3TC/NVP) treatment regimen. The overall drug resistance rate was 42.9% (6/14), the resistance rates to two and to all three drugs under treatment were 14.3% (2/14) and 7.1% (1/14), respectively.

CONCLUSION

This study is the first report on polymorphisms and emergence of drug-resistance mutations in HIV-1 subtype CRF01_AE prevailing in China. These findings provide useful information on global HIV genetic variability and non-B drug resistance.

Effects of a nucleoside reverse transcriptase inhibitor, stavudine, on glucose disposal and mitochondrial function in muscle of healthy adults

Mitochondrial dysfunction may contribute to the development of insulin resistance and type 2 diabetes. Nucleoside reverse transcriptase inhibitors (NRTIs), specifically stavudine, are known to alter mitochondrial function in human immunodeficiency virus (HIV)-infected individuals, but the effects of stavudine on glucose disposal and mitochondrial function in muscle have not been prospectively evaluated. In this study, we investigated short-term stavudine administration among healthy control subjects to determine effects on insulin sensitivity. A secondary aim was to determine the effects of stavudine on mitochondrial DNA (mtDNA) and function. Sixteen participants without personal or family history of diabetes were enrolled. Subjects were randomized to receive stavudine, 30-40 mg, twice a day, or placebo for 1 mo. Insulin sensitivity determined by glucose infusion rate during the hyperinsulinemic euglycemic clamp was significantly reduced after 1-mo exposure in the stavudine-treated subjects compared with placebo (-0.8 +/- 0.5 vs. +0.7 +/- 0.3 mg.kg(-1).min(-1), P = 0.04, stavudine vs. placebo). In addition, muscle biopsy specimens in the stavudine-treated group showed significant reduction in mtDNA/nuclear DNA (-52%, P = 0.005), with no change in placebo-treated subjects (+8%, P = 0.9). (31)P magnetic resonance spectroscopy (MRS) studies of mitochondrial function correlated with insulin sensitivity measures (r2 = 0.5, P = 0.008). These findings demonstrate that stavudine administration has potent effects on insulin sensitivity among healthy subjects. Further studies are necessary to determine whether changes in mtDNA resulting from stavudine contribute to effects on insulin sensitivity.

Effects of potent antiretroviral therapy on free testosterone levels and fat-free mass in men in a prospective, randomized trial: A5005s, a substudy of AIDS Clinical Trials Group Study 384

BACKGROUND

Low testosterone levels are commonly reported in patients with advanced human immunodeficiency virus disease. The effects of initiation of different antiretroviral regimens on testosterone levels and changes in fat-free mass have not been reported.

METHODS

Antiretroviral-naive men (n=213) were randomized to receive nelfinavir, efavirenz, or both plus either zidovudine and lamivudine or stavudine and didanosine. Patients underwent measurements of metabolic parameters, including determination of free testosterone level by equilibrium dialysis and bioelectrical impedance analysis, over a 64-week period.

RESULTS

At baseline, the median free testosterone level was 92 pg/mL; the level was subnormal (i.e., <50 pg/mL) in 6%. Lower CD4 cell count at the time of study entry, higher weight, and greater age were independently associated with lower baseline free testosterone level. At week 64, the median free testosterone level increased more in zidovudine-lamivudine recipients (48 of whom had paired values available; change, +31 pg/mL) than in stavudine-didanosine recipients (57 of whom had paired values; change, +3 pg/mL; P=.001, by Wilcoxon rank sum test), and it increased more in efavirenz recipients (37 of whom had paired values; change, +30 pg/mL) than in nelfinavir recipients (28 of whom had paired values; change, -3 pg/mL; P=.05). The median fat-free mass for the entire group increased by 1.2 kg at week 64 (change, +2.0%; P<.001); the increase was greater in the zidovudine-lamivudine group (n=70; change, +1.8 kg) than in the stavudine-didanosine group (n=79; change, +0.5 kg; P=.04), and the increase was also greater for efavirenz recipients (n=53; change, +2.1 kg) than among nelfinavir recipients (n=47; change, +0.4 kg; P=.003). White race, lower CD4 cell count at study entry, assignment to the efavirenz treatment arm, and assignment to the zidovudine-lamivudine treatment arm independently predicted greater absolute change in fat-free mass at week 64.

CONCLUSIONS

Subnormal free testosterone levels occurred infrequently among these antiretroviral-naive men. Free testosterone and fat-free mass levels increased after initiation of antiretroviral therapy, with greater increases at 64 weeks among zidovudine-lamivudine recipients than among stavudine-didanosine recipients and among efavirenz recipients than among nelfinavir recipients.

Selective inhibition of porcine endogenous retrovirus replication in human cells by acyclic nucleoside phosphonates

Several anti-human immunodeficiency virus type 1 reverse transcriptase inhibitors were evaluated for their antiviral activities against porcine endogenous retrovirus in human cells. Among the test compounds, zidovudine was found to be the most active. The order of potency was zidovudine > phosphonylmethoxyethoxydiaminopyrimidine = phosphonylmethoxypropyldiaminopurine > tenofovir > or = adefovir > stavudine.

Anti-retroviral activity of GMP-grade stampidine against genotypically and phenotypically nucleoside reverse transcriptase inhibitor resistant recombinant human immunodeficiency virus. An in vitro study

The in vitro potency of GMP-grade stampidine (CAS 217178-62-6) was examined against 3 clinical HIV-1 isolates and 6 recombinant HIV-1 clones with multi-NRTI 'resistance (NRTI: nucleoside reverse transcriptase inhibitors). GMP-grade stampidine active drug substance (Lot #'s MPR-M0008.00-01 and MPR-M0008.01-01) as well as GMP-grade stampidine extracted from the clinical stampidine capsules (GMP-Grade Clinical Batch, Pharmaceutical Service Lot Number 159I0601) were highly potent and exhibited nanomolar IC50 values against clinical HIV-1 isolates as well as recombinant HIV-1 clones with multi-NRTI resistance containing common patterns of reverse transcriptase mutations responsible for NRTI resistance.

Synthesis and anti-HIV-1 activities of novel podophyllotoxin derivatives

In order to explore the range of biological activities of the podophyllotoxin compound class, a novel series of derivatives of podophyllotoxin, which were conjugates containing stavudine and different structural podophyllotoxin analogues, were designed, synthesized, and evaluated for their anti-HIV-1 activities in vitro. Among these compounds, 19d and 19c showed the highest anti-HIV-1 activities with EC(50) values of 0.17 and 0.29 microM and TI values of 466.9 and 354.5, respectively.

Comparison of the phosphorylation of 4'-ethynyl 2',3'-dihydro-3'-deoxythymidine with that of other anti-human immunodeficiency virus thymidine analogs

Thymidine analogs, including 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxy-3'-deoxythymidine (D4T), are important antiretroviral agents. To exert antiretroviral activity, these analogs undergo a stepwise phosphorylation intracellularly to the active triphosphate metabolites. We previously reported that 4'-substituted D4T with an ethynyl group (i.e., 4'-ethynyl D4T) increased the anti-human immunodeficiency virus (HIV) activity and was active against multidrug-resistant HIV strains. 4'-Ethynyl D4T is a better substrate for phosphorylation by human thymidine kinase 1 than D4T is. In this report, we first studied the enzymes involved in the phosphorylation of 4'-ethynyl D4T from monophosphate to triphosphate metabolites. The 4'-ethynyl D4TMP is phosphorylated by recombinant human TMP kinase with a K(m) of 19 +/- 4 microM and a k(cat) of 0.007 +/- 0.001 s(-1); the relative efficiency is about 9 and 15% of those of D4TMP and AZTMP, respectively. Several enzymes from crude cellular extracts, including nucleoside diphosphate kinase, pyruvate kinase, creatine kinase, and 3-phosphoglycerate kinase, could phosphorylate 4'-ethynyl D4T-diphosphate. The relative phosphorylation efficiencies of 4'-ethynyl D4TDP were about 3 to 25% of those of D4TDP and were generally similar to those of AZTDP. In T-lymphoid cell lines, there was a preponderant accumulation of 4'-ethynyl D4TMP, suggesting that TMP kinase could be the rate-limiting enzyme in the metabolism of 4'-ethynyl D4T. Although the same enzymes are involved in the stepwise phosphorylation of thymidine analogs, their behaviors in phosphorylating metabolites of 4'-ethynyl D4T are different from those of D4T and AZT. Qualitatively, the metabolism of 4'-ethynyl D4T is more similar to that of AZT than to that of its progenitor, D4T.

Enzymatically activated cycloSal-d4T-monophosphates: The third generation of cycloSal-pronucleotides

The third generation of cycloSal-pronucleotides, 5-diacetoxymethyl-cycloSal-d4T-monophosphates (5-di-AM-cycloSal-d4TMPs), is reported as a new class of "lock-in"-modified cycloSal-pronucleotides. These compounds bear an esterase-cleavable geminal dicarboxylate (acylal) attached to the aromatic ring of the saligenyl unit. The conversion into a strong acceptor group (aldehyde) leads to a strong decrease in hydrolytic stability. As a consequence, a fast release of a nucleoside monophosphate (i.e., d4TMP) follows. The concept of this enzymatic activation is proven by hydrolysis studies in phosphate buffer, cell extracts, and human serum. These investigations showed the conversion of the acylal group into a polar aldehyde by enzymatic cleavage. Besides, antiviral activities against HIV are presented.

Bis-cycloSal-d4T-monophosphates: drugs that deliver two molecules of bioactive nucleotides

Bis-cycloSal-d4T-monophosphates have been synthesized as potentially anti-HIV active "dimeric" prodrugs of 2',3'-dideoxy-2',3'-didehydrothymidine monophosphate (d4TMP). These pronucleotides display a mask-drug ratio of 1:2, a novelty in the field of pronucleotides. Both bis-cycloSal-d4TMP 6 and bis-5-methyl-cycloSal-d4TMP 7 showed increased hydrolytic stability as compared to their "monomeric" counterparts and a completely selective hydrolytic release of d4TMP. The hydrolysis pathway was investigated via 31P NMR spectroscopy. Moreover, due to the steric bulkiness, compound 6 already displayed strongly reduced inhibitor potency toward human butyrylcholinesterase (BChE), while compound 7 turned out to be devoid of any inhibitory activity against BChE. Partial separation of the diastereomeric mixture of 6 revealed strong dependence of the pronucleotides' properties on the stereochemistry at the phosphorus centers. Both 6 and 7 showed good activity against HIV-1 and HIV-2 in wild-type CEM cells in vitro. These compounds were significantly more potent than the parent nucleoside d4T 1 in HIV-2-infected TK-deficient CEM cells, indicating an efficient TK-bypass.

Synthesis and anti-human immunodeficiency virus activity of 4'-branched (+/-)-4'-thiostavudines

Motivated by our recent finding that 4'-ethynylstavudine (4) is a promising anti-human immunodeficiency virus type 1 (HIV-1) agent, we synthesized its 4'-thio analogue, as well as other 4'-thiostavudines having a carbon substituent at the 4'-position, as racemates in this study. Methyl 3-oxo-tetrahydrothiophen-2-carboxylate (5) was used as a starting material to construct the requisite 4-thiofuranoid glycal (13). Introduction of a thymine base was carried out by an electrophilic addition reaction to 13 using N-iodosuccinimide (NIS) and bis(trimethylsilyl)thymine. The desired beta-anomer (16beta) obtained as a major product in this reaction underwent ready elimination with activated Zn to give the 4'-carbomethoxy derivative (18). By using 18 as a common intermediate, 4'-carbon-substituted (CH2OH, CO2Me, CONH2, CH=CH2, CN, and C(triple bond)CH) 4'-thiostavudines were prepared. Among these six compounds, 4'-cyano (28) and 4'-ethynyl (29) analogues were found to show inhibitory activity against HIV-1 with ED50 values of 7.6 and 0.74 microM, respectively. The activity of 29 was comparable to that of stavudine, but 29 was not as active as 4. Optical resolution of 29 was briefly examined.

Options for a Second-Line Antiretroviral Regimen for HIV Type 1-Infected Patients Whose Initial Regimen of a Fixed-Dose Combination of Stavudine, Lamivudine, and Nevirapine Fails

BACKGROUND

A fixed-dose combination of stavudine, lamivudine, and nevirapine is extensively used as an antiretroviral regimen in developing countries because of its affordability. Virological failure with this regimen has become more common, and a second-line regimen needs to be prepared in the national program.

METHODS

Genotypic resistance testing was conducted among human immunodeficiency virus type 1 (HIV-1)-infected patients who experienced treatment failure with their first antiretroviral regimen (a fixed-dose combination of stavudine, lamivudine, and nevirapine) during 2003-2005. Patterns of resistance mutations and options for a second-line regimen were studied.

RESULTS

We studied 98 patients (mean age, 35.2 years), of whom, 63% were male. The median duration of antiretroviral therapy was 20 months. The median HIV-1 RNA load at the time of virological failure detection was 4.1 log copies/mL. The prevalences of patients with > or =1 major mutation conferring drug resistance to nucleoside reverse-transcriptase inhibitors and nonnucleoside reverse-transcriptase inhibitors were 95% and 92%, respectively. M184V was the most common nucleoside reverse-transcriptase inhibitor resistance mutation (observed in 89% of patients). Thymidine analogue mutations, K65R, and Q151M were observed in 37%, 6%, and 8% of patients, respectively. Patients with an HIV-1 RNA load of >4 log copies/mL at the time of treatment failure had higher prevalence of thymidine analogue mutations (P=.041), K65R (P=.031), and Q151M (P=.008) mutations. The second-line regimen was determined in a resource-limited setting where tenofovir and enfuvirtide are not available; the options were limited for 48% of patients.

CONCLUSIONS

After experiencing treatment failure with a fixed-dose combination of stavudine, lamivudine, and nevirapine, almost all patients have lamivudine and nonnucleoside reverse-transcriptase inhibitor resistance. The options for a second-line regimen are limited for one-half of these patients. In resource-limited settings where availability of antiretroviral agents is limited, strategies for prevention of HIV-1 resistance are crucial. Early detection of virological failure may provide more options and better treatment outcomes.

Relationship of mitochondrial DNA depletion and respiratory chain activity in preadipocytes treated with nucleoside reverse transcriptase inhibitors

OBJECTIVE

To study the impact of adipocyte differentiation on nucleoside reverse transcriptase inhibitor (NRTI)-mediated mitochondrial DNA (mtDNA) depletion and to correlate mtDNA depletion with the activity of the respiratory chain complexes.

METHODS

We studied adipocyte phenotype, viability, differentiation (CCAAT/enhancer-binding protein [C/EBP]-alpha and peroxisome proliferator-activated receptor [PPAR]-gamma expression), adiponectin production, mtDNA content, activity of respiratory chain complexes and citrate synthase activity in 3T3-L1 adipocytes. Cells were exposed to zidovudine (6 microM or 180 microM), stavudine (3 microM or 90 microM), and zalcitabine (0.1 microM or 3 microM) at different developmental stages for up to 2 months.

RESULTS

Zidovudine and stavudine impaired adiponectin production in vitro at therapeutic Cmax concentrations, but none of the tested NRTIs had a negative impact on adipocyte differentiation or led to mtDNA depletion at these concentrations. Susceptibility of preadipocytes to mtDNA depletion was dependent on cell proliferation and differentiation, and mtDNA depletion occurred only after exposure to high drug concentrations. Under these conditions, stavudine led to up to 80% mtDNA depletion in both dividing and differentiating preadipocytes, whereas zidovudine affected mtDNA only in the differentiating cells. Despite mtDNA depletion by NRTIs, activity of the respiratory chain complexes was found to be unimpaired.

CONCLUSIONS

We found mtDNA depletion in adipocytes but proliferation and/or differentiation of the cells seems to be a prerequisite for this phenomenon. Depletion of mtDNA up to 80%, however, was not associated with impaired respiratory chain activity in 3T3-L1 preadipocytes.

Highly selective action of triphosphate metabolite of 4'-ethynyl D4T: a novel anti-HIV compound against HIV-1 RT

2',3'-Didehydro-3'-deoxy-4'-ethynylthymidine (4'-Ed4T), is a recently discovered nucleoside reverse transcriptase inhibitor (NRTI) showing a 5- to 10-fold greater anti-human immunodeficiency virus type 1 (HIV-1) activity and less cellular and mitochondrial toxicity than its parental compound, stavudine (D4T). It is also active against a variety of NRTI-resistant HIV-1 mutants under non-cytotoxic concentrations. In this study, the effects of 4'-Ed4TTP, which is the triphosphate metabolite of 4'-Ed4T, on HIV-1 reverse transcriptase (RT) activity were investigated. We found that 4'-Ed4TTP was a substrate of HIV-1 RT serving as a DNA chain terminator, and it inhibited the DNA polymerase activity of RT more efficiently than D4TTP. The value of Ki(4'-Ed4TTP)/Km(dTTP) is 0.15 for DNA/RNA primer/template duplex (P/T), but 0.7 for DNA/DNA P/T, suggesting 4'-Ed4TTP inhibits RT more efficiently during RNA-dependent DNA synthesis than DNA-dependent DNA synthesis. 4'-Ed4TTP was also found to inhibit the 3TC (Lamivudine)-resistant RT mutant, M184V, with 3-fold less efficiency than the wild type (wt) RT. 4'-Ed4TTP showed much less inhibitory effects toward major host DNA polymerases. Overall, our results suggest that 4'-Ed4TTP is the active form for anti-HIV-1 activity via its inhibitory effect against RT.

Effect of alkyl groups on the cellular hydrolysis of stavudine phosphoramidates

We examined the effect of cellular metabolism of three alkyl-substituted amino acid ester phosphoramidate derivatives of stavudine in different cell lines. Marked cell-to-cell differences were found in both the rate of hydrolysis and chiral selectivity. This selectivity implies that different enzymes may be involved in the metabolism of these compounds depending on the cell type involved. Notably, both the methyl and ethyl substituted derivatives underwent hydrolysis in presence of various cell lines, whereas the tert-butyl substituted compound was resistant to hydrolysis implying that steric hindrance associated with this group along with electron density may play a key role in the hydrolysis profile of these compounds. Additionally we found this mimicked the hydrolysis profiles obtained for bacterial enzymes. Furthermore, our results suggest that the site of attack of the cellular enzymes is confined to the ester side chain of the molecule. This result is also consistent with our earlier observation using bacterial enzymes as well as using 'd' isomers.

Application of the cycloSal-prodrug approach for improving the biological potential of phosphorylated biomolecules

Pronucleotides represent a promising tool to improve the biological activity of nucleoside analogs in antiviral and cancer chemotherapy. The cycloSal-approach is one of several conceptually different pronucleotide systems. This approach can be applied to various nucleoside analogs. A salicyl alcohol as a cyclic bifunctional masking unit is used, and shown to afford a chemically driven release of the particular nucleotide from the lipophilic phosphate triester precursor molecule. A conceptual extension of the cycloSal-approach results in the design of "lock-in"-cycloSal-derivatives. The cycloSal-approach is not restricted to the delivery of bioactive nucleotides but also useful for the intracellular delivery of hexose-1-phosphates.

Synthesis, separation and anti-HIV activity of distereoisomers of N-[p-(4-bromophenyl) -2',3'-didehydro-3'-deoxy-5'-thymidylyl]-L-alanine methyl ester (stampidine)

The distereoisomers of stampidine (STAMP, DDE-113, HI-113, N-[p-(4-bromophenyl)-2'3'-didehydro-3'-deoxy-5'-thymidylyl]-L-alanine methyl ester, CAS 217178-62-6) were separated using two different procedures. The first method involved separation of the isomers by fractional crystallization, and the second method utilized a preparative HPLC. Both isomers were active against the HIV-1 strain HTLV(IIIB) and neither isomer was more or less active than distereoisomeric mixture of stampidine.

Stampidine as a novel nucleoside reverse transcriptase inhibit with potent anti-HIV activity

Stavudine (STV, d4T, 2',3'-didehydro-3'-deoxythymidine, CAS 3056-17-5) is a standard anti-HIV drug. Stampidine (STAMP, DDE-113, HI-113, N-[p-(4-bromophenyl)-2',3'-didehydro-3'-deoxy-5'-thymidylyl]-L-alanine methyl ester, CAS 217178-62-6) is a novel aryl phosphate derivative of stavudine with more potent anti-HIV activity and more favorable pharmacodynamic features. The remarkable potency of stampidine against clinical HIV-1 isolates with NRTI- or NNRTI-resistance (NRTI, nucleoside reverse transcriptase inhibitor; NNRTI, non-nucleoside reverse transcriptase inhibitor) warrants the further development of this new anti-HIV agent.

Potency of stampidine against multi-nucleoside reverse transcriptase inhibitor resistant human immunodeficiency viruses

The in vitro potency of stampidine (STAMP, DDE-113, HI-113, N-[p-(4-bromophenyl)-2',3'-didehydro-3'-deoxy-5'-thymidylyl]-L-alanine methyl ester, CAS 217178-62-6) was examined against 8 clinical non-B subtype HIV-1 isolates with resistance to stavudine (STV, d4T), adefovir and tenofovir, 19 clinical zidovudine-resistant HIV-1 isolates, and 6 recombinant HIV-1 clones with multi-resistance against nucleoside reverse transcriptase inhibitors. Stampidine exhibited potent anti-HIV activity against each one of these 33 HIV-1 isolates with subnanomolar to nanomolar IC50 values.

Site-specific enzymatic activation of the anti-HIV agent stampidine

Stampidine (STAMP, DDE-113, HI-113, N-[p-(4-bromophenyl)-2',3'-didehydro-3'-deoxy-5'-thymidylyl]-L-alanine methyl ester, CAS 217178-62-6) and two stampidine analogs containing ethyl or t-butyl groups were synthesized and their rates of enzymatic activation were compared side-by-side. Enzymes such as lipase, esterase and protease did not hydrolyze the butyl substituted STAMP analog. These experimental results show that the site of attack for the enzymatic hydrolysis of STAMP is the ester side chain of the molecule.

The 118I Reverse Transcriptase Mutation Is the Only Independent Genotypic Predictor of Virologic Failure to a Stavudine-Containing Salvage Therapy in HIV-1-Infected Patients

Patients infected with HIV-1 with more than 1000 HIV-1 RNA copies/mL, who were genotyped within 3 months before starting stavudine and treated for at least 3 months with a stable stavudine-containing highly active antiretroviral therapy, were selected from our database to identify the determinants of response to stavudine. Nonresponse was defined as a failure to achieve HIV-1 RNA level of less than 400 copies/mL or a reduction of more than 2 log10 by week 12. Univariate logistic analysis was used to elicit the failure-associated reverse transcriptase mutations (scored 1 to develop a genotype score). Eighty-one patients were eligible for the analysis, including 75 (93%) who previously received zidovudine. Thirty-five (43%) were nonresponders. Univariate logistic analysis revealed the following failure-associated mutations: 41L (P = 0.0001), 44D (P = 0.02), 118I (P = 0.0006), 184V (P = 0.04), 210W (P = 0.0004), and 215Y (P = 0.002) for a median stavudine score of 2. Failure was observed in 7 (18.9%) of 37 patients with a score less than 2, compared with 28 (63.6%) of 44 patients with a score of 2 or greater (P < 0.0001). The multivariable analysis showed that the 118I mutation (P = 0.04) was the only independent genotypic predictor of failing on a stavudine- containing highly active antiretroviral therapy.