Sustainable Protocol for the Synthesis of 2',3'-Dideoxynucleoside and 2',3'-Didehydro-2',3'-dideoxynucleoside Derivatives.

An improved protocol for the transformation of ribonucleosides into 2',3'-dideoxynucleoside and 2',3'-didehydro-2',3'-dideoxynucleoside derivatives, including the anti-HIV drugs stavudine (d4T), zalcitabine (ddC) and didanosine (ddI), was established. The process involves radical deoxygenation of xanthate using environmentally friendly and low-cost reagents. Bromoethane or 3-bromopropanenitrile was the alkylating agent of choice to prepare the ribonucleoside 2',3'-bisxanthates. In the subsequent radical deoxygenation reaction, tris(trimethylsilyl)silane and 1,1'-azobis(cyclohexanecarbonitrile) were used to replace hazardous Bu3SnH and AIBN, respectively. In addition, TBAF was substituted for camphorsulfonic acid in the deprotection step of the 5'-O-silyl ether group, and an enzyme (adenosine deaminase) was used to transform 2',3'-dideoxyadenosine into 2',3'-dideoxyinosine (ddI) in excellent yield.

Post-Catalytic Complexes with Emtricitabine or Stavudine and HIV-1 Reverse Transcriptase Reveal New Mechanistic Insights for Nucleotide Incorporation and Drug Resistance.

Human immunodeficiency virus 1 (HIV-1) infection is a global health issue since neither a cure nor a vaccine is available. However, the highly active antiretroviral therapy (HAART) has improved the life expectancy for patients with acquired immunodeficiency syndrome (AIDS). Nucleoside reverse transcriptase inhibitors (NRTIs) are in almost all HAART and target reverse transcriptase (RT), an essential enzyme for the virus. Even though NRTIs are highly effective, they have limitations caused by RT resistance. The main mechanisms of RT resistance to NRTIs are discrimination and excision. Understanding the molecular mechanisms for discrimination and excision are essential to develop more potent and selective NRTIs. Using protein X-ray crystallography, we determined the first crystal structure of RT in its post-catalytic state in complex with emtricitabine, (-)FTC or stavudine (d4T). Our structural studies provide the framework for understanding how RT discriminates between NRTIs and natural nucleotides, and for understanding the requirement of (-)FTC to undergo a conformation change for successful incorporation by RT. The crystal structure of RT in post-catalytic complex with d4T provides a "snapshot" for considering the possible mechanism of how RT develops resistance for d4T via excision. The findings reported herein will contribute to the development of next generation NRTIs.

Polyfluoroaromatic stavudine (d4T) ProTides exhibit enhanced anti-HIV activity.

Human Immunodeficiency Virus (HIV) damages the immune system and leads to the life-threatening acquired immunodeficiency syndrome (AIDS). Despite the advances in the field of antiretroviral treatment, HIV remains a major public health challenge. Nucleosides represent a prominent chemotherapeutic class for treating viruses, however their cellular uptake, kinase-mediated activation and catabolism are limiting factors. Herein, we report the synthesis and in vitro evaluation of stavudine (d4T) ProTides containing polyfluorinated aryl groups against two strains; HIV-1 (IIIB) and HIV-2 (ROD). ProTide 5d containing a meta-substituted pentafluorosulfanyl (3-SF5) aryl group showed superior antiviral activity over the parent d4T and the nonfluorinated analogue 5a. ProTide 5d has low nanomolar antiviral activity; (IC50 = 30 nM, HIV-1) and (IC50 = 36 nM, HIV-2) which is over tenfold more potent than d4T. Interestingly, ProTide 5d showed a significantly high selectivity indices with SI = 1753 (HIV-1) and 1461 (HIV-2) which is more than twice that of the d4T. All ProTides were screened in wild type as well as thymidine kinase deficient (TK-) cells. Enzymatic activation of ProTide 5d using carboxypeptidase Y enzyme and monitored using both 31P and 19F NMR is presented.

Establishment and characterisation of a stavudine (d4T)-induced rat model of antiretroviral toxic neuropathy (ATN) using behavioural and pharmacological methods.

Human immuno-deficiency virus (HIV) associated sensory neuropathy (SN) is a frequent complication of HIV infection. It is extremely difficult to alleviate and hence the quality of life of affected individuals is severely and adversely impacted. Stavudine (d4T) is an antiretroviral drug that was widely used globally prior to 2010 and that is still used today in resource-limited settings. Its low cost and relatively good efficacy when included in antiretroviral dosing regimens means that there is a large population of patients with d4T-induced antiretroviral toxic neuropathy (ATN). As there are no FDA approved drugs for alleviating ATN, it is important to establish rodent models to probe the pathobiology and to identify potentially efficacious new drug treatments. In the model establishment phase, d4T administered intravenously at a cumulative dose of 375 mg/kg in male Wistar Han rats evoked temporal development of sustained mechanical allodynia in the hindpaws from day 10 to day 30 after initiation of d4T treatment. As this d4T dosing regimen was also well tolerated, it was used for ATN model induction for subsequent pharmacological profiling. Both gabapentin at 30-100 mg/kg and morphine at 0.3-2 mg/kg given subcutaneously produced dose-dependent relief of mechanical allodynia with estimated ED50's of 19 mg/kg and 0.4 mg/kg, respectively. In contrast, intraperitoneal administration of meloxicam or amitriptyline up to 30 mg/kg and 7 mg/kg, respectively, lacked efficacy. Our rat model of ATN is suitable for investigation of the pathophysiology of d4T-induced SN as well as for profiling novel molecules from analgesic drug discovery programs.

Lipid levels, insulin resistance and cardiovascular risk over 96 weeks of antiretroviral therapy: a randomised controlled trial comparing low-dose stavudine and tenofovir.

BACKGROUND: HIV infection and antiretroviral treatment are associated with changes in lipid levels, insulin resistance and risk of cardiovascular disease (CVD). We investigated these changes in the first 96 weeks of treatment with low-dose stavudine or tenofovir regimens. METHODS: This is a secondary analysis of a double blind, randomised controlled trial performed in South-Africa, Uganda and India comparing low-dose stavudine (20 mg twice daily) with tenofovir in combination with efavirenz and lamivudine in antiretroviral-naïve adults (n = 1067) (Clinicaltrials.gov, NCT02670772). Over 96 weeks, data were collected on fasting lipids, glucose and insulin. Insulin resistance was assessed with the HOMA-IR index and 10-year CVD risk with the Framingham risk score (FRS). A generalized linear mixed model was used to estimate trends over time. RESULTS: Participants were on average 35.3 years old, 57.6% female and 91.8% Black African. All lipid levels increased following treatment initiation, with the sharpest increase in the first 24 weeks of treatment. The increase in all lipid subcomponents over 96 weeks was higher among those in the stavudine than the tenofovir group. Insulin resistance increased steadily with no difference detected between study groups. FRS rose from 1.90% (1.84-1.98%) at baseline to 2.06 (1.98-2.15%) at week 96 for the total group, with no difference between treatment arms (p = 0.144). Lipid changes were more marked in Indian than African participants. CONCLUSION: Lipid levels increased in both groups, with low-dose stavudine resulting in a worse lipid profile compared to tenofovir. Insulin resistance increased, with no difference between regimens. CVD risk increased over time and tended to increase more in the group on stavudine. The low CVD risk across both arms argues against routine lipid and glucose monitoring in the absence of other CVD risk factors. In high risk patients, monitoring may only be appropriate at least a year after treatment initiation.

Can We Improve Stavudine's Safety Profile in Children? Pharmacokinetics of Intracellular Stavudine Triphosphate with Reduced Dosing.

Stavudine remains a useful replacement option for treatment for HIV+ children. WHO reduced the adult dose to 30 mg twice daily, which maintains efficacy and lowers mitochondrial toxicity. We explored intracellular stavudine triphosphate levels in children receiving a reduced dose of 0.5 to 0.75 mg/kg of body weight twice daily to investigate whether a similar dose optimization can safely be made. A population pharmacokinetic model was developed to describe the pharmacokinetics of intracellular stavudine triphosphate in 23 HIV+ children and 24 HIV+ adults who received stavudine at 0.5 mg/kg and 20 mg twice daily for 7 days, respectively. Simulations were employed to optimize the pediatric dosing regimen to match exposures in adults receiving the current WHO-recommended dose of 30 mg twice daily. A biphasic disposition model with first-order appearance and disappearance described the pharmacokinetics of stavudine triphosphate. The use of allometric scaling with fat-free mass characterized well the pharmacokinetics in both adults and children, and no other significant effect could be detected. Simulations of 30 mg twice daily in adults predicted median (interquartile range [IQR]) stavudine triphosphate minimum drug concentration (Cmin) and maximum drug concentration (Cmax) values of 13 (10 to 19) and 45 (38 to 53) fmol/106 cells, respectively. Targeting this exposure, simulations in HIV+ children were used to identify a suitable weight-band dosing approach (0.5 to 0.75 mg/kg), which was predicted to achieve median (IQR) Cmin and Cmax values of 13 (9 to 18) and 49 (40 to 58) fmol/106 cells, respectively. Weight-band dosing using a stavudine dose of 0.5 to 0.75 mg/kg is proposed, and it shows comparable exposures to adults receiving the current WHO-recommended dose of 30 mg twice daily. Our pharmacokinetic results suggest that the decreased stavudine dose in children >2 years would have a reduced toxic effect while retaining antiretroviral efficacy.

Low prevalence of lipodystrophy in HIV-infected Senegalese children on long-term antiretroviral treatment: the ANRS 12279 MAGGSEN Pediatric Cohort Study.

BACKGROUND: The long-term benefits of antiretroviral treatment (ART) are associated with metabolic complications, especially lipodystrophy, which has been well described among HIV-infected adults and children on ART in developed settings. Specifically, stavudine, and to a lesser extent zidovudine and protease inhibitors (PI), have been consistently implicated in the development of lipodystrophy. In 2006, following advice from the WHO, Senegal began phasing out stavudine from first-line ART. The objectives of this cross-sectional analysis are to assess and identify risk factors affecting the prevalence of lipodystrophy in Senegalese children and adolescents on long-term ART participating in a cohort study. METHODS: Lipodystrophy was clinically assessed in two- to 18-year-old children on ART for at least six months and with no concurrent severe acute malnutrition. Risk factors for lipodystrophy were identified using stepwise multivariable logistic regression. Explanatory variables included clinical and personal data, immunovirologic status, and therapeutic history. RESULTS: Overall, 254 children were assessed for lipodystrophy. The median age was 10.9 years (IQR: 8.1-14.2) and the median duration on ART was 54 months (32-84). Only 18% had been previously treated with stavudine, with a median treatment duration of 8 months (5-25). Ongoing treatment included 76% of children receiving zidovudine (median duration of 48 months (26-74)) and 27% receiving PI (lopinavir/ritonavir; median duration of 49 months (23-59)). Mild signs of lipodystrophy were observed in 33 children (13%): 28 with lipoatrophy, 4 with lipohypertrophy and one with combined type. Boys were more likely to present with lipoatrophy than girls (aOR: 4.3, 95% CI: 1.6-11.7). Children previously treated with stavudine for ≥1 year had a greater risk for lipoatrophy than those never exposed (3.8, 1.0-14.0), although the association was weak. There was no association between lipodystrophy and age or current or cumulative treatment with lopinavir/ritonavir or zidovudine. CONCLUSIONS: We report low prevalence of mild lipodystrophy in children and adolescents on long-term ART receiving a stavudine-sparing regimen. These findings are reassuring for clinicians in low-income settings where zidovudine is massively prescribed and lopinavir/ritonavir is the only widely available PI. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01771562 (registration date: 01/18/2013).

A Direct Comparison of the Effects of the Antiretroviral Drugs Stavudine, Tenofovir and the Combination Lopinavir/Ritonavir on Bone Metabolism in a Rat Model.

Antiretroviral (ARV) treatment may induce metabolic complications in HIV patients on long-term therapy that can affect bone health. In this study, the effects of the ARVs Stavudine (d4T), Tenofovir (TDF) and Lopinavir/ritonavir (LPV/r) on bone metabolism and lipodystrophy were directly compared in rats to negate the consequences of HIV-associated confounding factors. Healthy 12-14-week-old male Wistar rats (n = 40) were divided into four treatment groups and received an oral animal equivalent dose of either Stavudine (6.2 mg/kg/day), TDF (26.6 mg/kg/day), LPV/r (70.8 mg/kg/day) or water (Control 1.5 mL water/day) for a period of 9 weeks. Whole-body DXA measurements, a biomechanical three-point breaking test and histomorphometric analysis were performed on the femurs and tibias at the end of the treatment period. Stavudine monotherapy was found to be associated with decreased femoral bone mineral density that translated into reduced bone strength, whereas histomorphometric analysis demonstrated that Stavudine induces an imbalance in bone metabolism at tissue level, evident in higher resorption (eroded surfaces, osteoclast surfaces and osteoclast number) and lower formation parameters (osteoblast surfaces and osteoid surfaces). This was less clear in the rats treated with either TDF or LPV/r. Furthermore, both Stavudine and TDF treatment resulted in significant bone marrow adiposity, although no significant redistribution of body fat was noted in the treated rats compared to controls. The data from this study suggest that in the absence of HIV-associated factors, LPV/r is less detrimental to bone metabolism compared to Stavudine and TDF.

Early Stage HIV Management and Reduction of Stavudine-Induced Hepatotoxicity in Rats by Experimentally Developed Biodegradable Nanoparticles.

The objectives of this research work were to develop optimized nanoparticulate formulations of poly (d,l-lactic-co-glycolic acid) (PLGA) (85:15) with an anti-AIDS drug stavudine and to evaluate their in-vitro uptake by the macrophages and hepatotoxicity in-vivo. Nanoparticles were prepared by nanoprecipitation method based on a factorial design with varying parameters such as the amounts of polymer and stabilizer used. Physicochemical characterizations such as drug-excipient interaction, surface morphology, particle size, and zeta potential measurements were carried out. The best formulation was selected and tagged with fluorescein isothiocyanate (FITC) for cellular uptake study of the formulation. In-vitro uptake of nanoparticles by macrophages was carried out. Formulation-induced hepatotoxicity was assessed by analyzing some serum hepatotoxic parameters and hepatic histology following 10-day treatment in comparison with the free drug. Nanoparticles exhibited smooth surface with particle size 84-238 nm, high entrapment efficiency (approx 85%), and negative surface charge. Formulations showed a sustained drug release pattern over the study period. In-vitro uptake study by macrophages exhibited a time-dependent profile. In-vivo studies on rats showed improvement in the serum parameters and maintenance of the integrity of the hepatic architecture indicating decreased hepatotoxicity with the formulations as compared to the free drug. The experimental results showed a positive outcome in the development of antiretroviral drug carrier exhibiting sustained drug release, macrophage-targeted delivery characteristics, and having reduced hepatoxicity. This could be beneficial for the management of early stage of HIV infection besides reducing the drug load for effective treatment, thereby offering an attractive option in AIDS therapy.

Higher Prevalence of Hypertension in HIV-1-Infected Patients on Combination Antiretroviral Therapy Is Associated With Changes in Body Composition and Prior Stavudine Exposure.

BACKGROUND: Individuals infected with human immunodeficiency virus (HIV) have a higher risk of cardiovascular disease, potentially partly mediated by a higher prevalence of hypertension. We therefore examined the prevalence and determinants of hypertension in HIV-1-infected patients compared with appropriate HIV-negative controls. METHODS: Data from 527 HIV-1-infected and 517 HIV-uninfected participants at the time of enrollment into the ongoing AGEhIV Cohort Study were analyzed. Hypertension was defined as systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, and/or self-reported use of antihypertensive drugs. RESULTS: Hypertension prevalence was higher among HIV-1-infected individuals compared with controls (48.2% vs 36.4%; odds ratio [OR], 1.63; 95% confidence interval [CI], 1.27-2.09). In logistic regression models adjusted for age, sex, ethnicity, family history of hypertension, smoking, alcohol use, physical activity, and body mass index, the association between HIV and hypertension remained statistically significant (ORHIV, 1.65; 95% CI, 1.25-2.19), but was attenuated after additional adjustment for waist-to-hip ratio (ORHIV, 1.29; 95% CI, .95-1.76). Among HIV-1-infected individuals, particularly among those with mono/dual nucleoside reverse transcriptase inhibitor therapy prior to combination antiretroviral therapy, stavudine exposure was independently associated with hypertension (ORstavudine, 1.54; 95% CI, 1.04-2.30). This association was attenuated after additional adjustment for either waist-to-hip ratio (ORstavudine, 1.30; 95% CI, .85-1.96) or hip circumference (ORstavudine, 1.40; 95% CI, .93-2.11). CONCLUSIONS: Our findings suggest that changes in body composition, involving both abdominal obesity and stavudine-induced peripheral lipoatrophy, might contribute to the higher prevalence of hypertension in HIV-1-infected patients. CLINICAL TRIALS REGISTRATION: NCT01466582.

Niflumic acid, a TRPV1 channel modulator, ameliorates stavudine-induced neuropathic pain.

TRP channels have been discovered as a specialized group of somatosensory neurons involved in the detection of noxious stimuli. Desensitization of TRPV1 located on dorsal root and trigeminal ganglia exhibits analgesic effect and makes it potential therapeutic target for treatment of neuropathic pain. With this background, the present study was aimed to investigate the protective effect of niflumic acid, a TRPV1 modulator, on stavudine (STV)-induced neuropathic pain in rats. Stavudine (50 mg/kg) was administered intravenously via tail vein in rats to induce neuropathic pain. Various behavioral tests were performed to access neuropathic pain (hyperalgesia and allodynia) on 7th, 14th, 21st, and 28th days. Electrophysiology (motor nerve conduction velocity; MNCV) and biochemical estimations were conducted after 28th day. Niflumic acid (10, 15, and 20 mg/kg) was administered intraperitoneally and evaluated against behavioral, electrophysiological (MNCV), and biochemical alterations in stavudine-treated rats. Pregabalin (30 mg/kg) was taken as reference standard and administered intraperitoneally. Four weeks after stavudine injection, rats developed behavioral, electrophysiological (MNCV), and biochemical (oxidative, nitrosative stress, and inflammatory cytokines, TRPV1) alterations. Niflumic acid restored core and associated symptoms of peripheral neuropathy by suppressing oxidative-nitrosative stress, inflammatory cytokines (TNF-α, IL-1ß) and TRPV1 level in stavudine-induced neuropathic pain in rats. Pharmacological efficacy of niflumic acid (20 mg/kg) was equivalent to pregabalin (30 mg/kg). In conclusion, niflumic acid attenuates STV-induced behavioral, electrophysiological and biochemical alterations by manipulating TRP channel activity in two manners: (1) direct antagonistic action against TRPV1 channels and (2) indirect inhibition of TRP channels by blocking oxidative and inflammatory surge. Therefore, NA can be developed as a potential pharmacotherapeutic adjunct for antiretroviral drug-induced neuropathy.

Changing utilization of Stavudine (d4T) in HIV-positive people in 2006-2013 in the EuroSIDA study.

OBJECTIVES: The long-term side effects of stavudine (d4T) led to recommendations in 2009 to phase out use of this drug. We aimed to describe temporal patterns of d4T use across Europe. METHODS: Patients taking combination antiretroviral therapy (cART) in EuroSIDA with follow-up after 1 January 2006 were included in the study. cART was defined as d4T-containing [d4T plus at least two other antiretrovirals (ARVs) from any class] or non-d4T-containing (at least three ARVs from any class, excluding d4T). Poisson regression was used to describe temporal changes in the prevalence of d4T use and factors associated with initiating d4T. RESULTS: A total of 5850 patients receiving cART on 1 January 2006 were included in the current analysis, rising to 7768 patients on January 1 2013. During this time, the prevalence of d4T use fell from 11.2% to 0.7%, with an overall decline of 19% per 6 months [95% confidence interval (CI) 19-20%]. d4T use declined fastest in Northern Europe [26% (95% CI 23-29%) per 6 months], and slowest in Eastern Europe [17% (95% CI 16-19%) per 6 months]. In multivariable Poisson regression models, new d4T initiations decreased by 14% per 6 months [adjusted incidence rate ratio (aIRR) 0.86; 95% CI 0.80-0.91]. Factors associated with initiating d4T were residence in Eastern Europe (aIRR 4.31; 95% CI 2.17-9.98) versus other European regions and HIV RNA > 400 copies/mL (aIRR 3.11; 95% CI 1.60-6.02) versus HIV RNA < 400 copies/mL. CONCLUSIONS: d4T use has declined sharply since 2006 to low levels in most regions; however, a low but persistent level of d4T use remains in Eastern Europe, where new d4T initiations post 2006 are also more common. The reasons for the regional differences may be multifactorial, but it is important to ensure that all clinicians treating HIV-positive patients are aware of the potential harmful effects associated with d4T.

Distal leg epidermal nerve fiber density as a surrogate marker of HIV-associated sensory neuropathy risk: risk factors and change following initial antiretroviral therapy.

Distal leg epidermal nerve fiber density (ENFD) is a validated predictor of HIV sensory neuropathy (SN) risk. We assessed how ENFD is impacted by initiation of first-time antiretroviral therapy (ART) in subjects free of neuropathy and how it is altered when mitochondrial toxic nucleoside medications are used as part of ART. Serial changes in proximal thigh and distal leg ENFD were examined over 72 weeks in 150 Thai subjects randomized to a regimen of stavudine (d4T) switching to zidovudine (ZDV) at 24 weeks vs ZDV vs tenofovir (TDF) for the entire duration of study, all given in combination with nevirapine. We found individual variations in ENFD change, with almost equal number of subjects who decreased or increased their distal leg ENFD over 72 weeks and no relationship to nucleoside backbone or to development of neuropathic signs or symptoms. Lower baseline distal leg ENFD and greater increases in mitochondrial oxidative phosphorylation complex I (CI) activity were associated with larger increases in distal leg ENFD over 72 weeks. Distal leg ENFD correlated with body composition parameters (body surface area, body mass index, height) as well as with blood pressure measurements. Assessed together with a companion cross-sectional study, we found that mean distal leg ENFD in all HIV+ subjects was lower than in HIV- subjects but similar among HIV+ groups whether ART-naïve or on d4T with/without neuropathy/neuropathic symptoms. The utility of ENFD as a useful predictor of small unmyelinated nerve fiber damage and neuropathy risk in HIV may be limited in certain populations.

A randomized clinical trial comparing metabolic parameters after 48 weeks of standard- and low-dose stavudine therapy and tenofovir disoproxil fumarate therapy in HIV-infected South African patients.

OBJECTIVES: Low-dose stavudine therapy may have a lower toxicity profile compared with standard dose. A randomized controlled trial comparing these two doses of stavudine with tenofovir disoproxil fumarate (tenofovir DF) was performed to assess the effects on anthropometry, markers of inflammation, and lipid and glucose metabolism in Black South African patients. METHODS: Sixty patients were randomized 1:1:1 to either standard-dose (30-40 mg) or low-dose (20-30 mg) stavudine or tenofovir DF (300 mg), each combined with lamivudine and efavirenz, for 48 weeks. Anthropometry, markers of inflammation, and lipid and glucose metabolism were assessed using standard techniques. RESULTS: In all three treatment arms, there was a significant increase in lipid levels over the study period. At 48 weeks, fasting glucose level (P < 0.005) and homeostasis model assessment (HOMA) score (P < 0.05) increased significantly in the standard-dose stavudine arm, as did insulin and C-peptide levels in both the standard- and low-dose stavudine arms. At week 48, a significant decrease (P < 0.05) in adiponectin was noted in the standard-dose stavudine arm, but there was an increase (P < 0.005) in the tenofovir DF arm. In both the stavudine arms, significant increases in anthropometric measures occurred at 24 weeks but these decreased by week 48. Mitochondrial toxicities occurred in both the stavudine arms. Immunological and virological outcomes were similar for all three arms. CONCLUSIONS: This study highlights the occurrence of metabolic abnormalities with both stavudine and tenofovir DF treatment. Awareness of the potential increased cardiovascular risk should be of concern with the use of both these therapies.

Impact of choice of NRTI in first-line antiretroviral therapy: a cohort analysis of stavudine vs. tenofovir.

OBJECTIVE: In April 2010, South Africa replaced stavudine with tenofovir in first-line antiretroviral therapy (ART) despite tenofovir's higher cost. We examined treatment outcomes over 24 months amongst patients initiated on tenofovir-based vs. stavudine-based first-line regimens. METHODS: Prospective cohort analysis of 3940 patients newly initiating either stavudine-based (April 2009 to March 2010) or tenofovir-based (April 2010 to March 2011) ART in Johannesburg, South Africa. Cox proportional hazards models and Fine and Gray's competing risk regression accounting for death were used to model mortality and loss to follow-up, respectively. Linear and log-binomial regression were used to evaluate associations with immunologic response and unsuppressed virus (≥ 400 copies/ml), respectively. RESULTS: About 1878 patients prescribed tenofovir and 2062 patients prescribed stavudine were included. One hundred and sixty-six (8.8%) tenofovir and 244 (11.8%) stavudine patients died. Three hundred and fifty (18.6%) tenofovir and 379 (18.4%) stavudine patients were lost to follow-up over 24 months on ART. Adjusted regression models showed tenofovir and stavudine were comparable regarding death, loss to follow-up, immunologic response and virologic status. CONCLUSIONS: We found no difference in mortality, loss to follow-up, immunological and virologic outcomes over the first 24-months on ART associated with tenofovir compared with stavudine.

Efficient syntheses of [¹¹C]zidovudine and its analogs by convenient one-pot palladium(0)-copper(I) co-mediated rapid C-[¹¹C]methylation.

The nucleosides zidovudine (AZT), stavudine (d4T), and telbivudine (LdT) are approved for use in the treatment of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections. To promote positron emission tomography (PET) imaging studies on their pharmacokinetics, pharmacodynamics, and applications in cancer diagnosis, a convenient one-pot method for Pd(0)-Cu(I) co-mediated rapid C-C coupling of [(11)C]methyl iodide with stannyl precursor was successfully established and applied to synthesize the PET tracers [(11)C]zidovudine, [(11)C]stavudine, and [(11)C]telbivudine. After HPLC purification and radiopharmaceutical formulation, the desired PET tracers were obtained with high radioactivity (6.4-7.0 GBq) and specific radioactivity (74-147 GBq/µmol) and with high chemical (>99%) and radiochemical (>99.5%) purities. This one-pot Pd(0)-Cu(I) co-mediated rapid C-[(11)C]methylation also worked well for syntheses of [methyl-(11)C]thymidine and [methyl-(11)C]4'-thiothymidine, resulting twice the radioactivity of those prepared by a previous two-pot method. The mechanism of one-pot Pd(0)-Cu(I) co-mediated rapid C-[(11)C]methylation was also discussed.

Nucleoside reverse transcriptase inhibitor resistance mutations associated with first-line stavudine-containing antiretroviral therapy: programmatic implications for countries phasing out stavudine.

BACKGROUND: The World Health Organization Antiretroviral Treatment Guidelines recommend phasing-out stavudine because of its risk of long-term toxicity. There are two mutational pathways of stavudine resistance with different implications for zidovudine and tenofovir cross-resistance, the primary candidates for replacing stavudine. However, because resistance testing is rarely available in resource-limited settings, it is critical to identify the cross-resistance patterns associated with first-line stavudine failure. METHODS: We analyzed HIV-1 resistance mutations following first-line stavudine failure from 35 publications comprising 1,825 individuals. We also assessed the influence of concomitant nevirapine vs. efavirenz, therapy duration, and HIV-1 subtype on the proportions of mutations associated with zidovudine vs. tenofovir cross-resistance. RESULTS: Mutations with preferential zidovudine activity, K65R or K70E, occurred in 5.3% of individuals. Mutations with preferential tenofovir activity, ≥ two thymidine analog mutations (TAMs) or Q151M, occurred in 22% of individuals. Nevirapine increased the risk of TAMs, K65R, and Q151M. Longer therapy increased the risk of TAMs and Q151M but not K65R. Subtype C and CRF01_AE increased the risk of K65R, but only CRF01_AE increased the risk of K65R without Q151M. CONCLUSIONS: Regardless of concomitant nevirapine vs. efavirenz, therapy duration, or subtype, tenofovir was more likely than zidovudine to retain antiviral activity following first-line d4T therapy.

Physiologically Based Pharmacokinetic (PBPK) Model of Gold Nanoparticle-Based Drug Delivery System for Stavudine Biodistribution.

Computational modelling has gained attention for evaluating nanoparticle-based drug delivery systems. Physiologically based pharmacokinetic (PBPK) modelling provides a mechanistic approach for evaluating drug biodistribution. The aim of this work is to develop a specific PBPK model to simulate stavudine biodistribution after the administration of a 40 nm gold nanoparticle-based drug delivery system in rats. The model parameters used have been obtained from literature, in vitro and in vivo studies, and computer optimization. Based on these, the PBPK model was built, and the compartments included were considered as permeability rate-limited tissues. In comparison with stavudine solution, a higher biodistribution of stavudine into HIV reservoirs and the modification of pharmacokinetic parameters such as the mean residence time (MRT) have been observed. These changes are particularly noteworthy in the liver, which presents a higher partition coefficient (from 0.27 to 0.55) and higher MRT (from 1.28 to 5.67 h). Simulated stavudine concentrations successfully describe these changes in the in vivo study results. The average fold error of predicted concentrations after the administration of stavudine-gold nanoparticles was within the 0.5-2-fold error in all of the tissues. Thus, this PBPK model approach may help with the pre-clinical extrapolation to other administration routes or the species of stavudine gold nanoparticles.

Incidence and associated factors of type 2 diabetes mellitus onset in the Brazilian HIV/AIDS cohort study.

BACKGROUND: People living with HIV (PLH) under combined antiretroviral therapy (cART) are at risk of developing type 2 diabetes mellitus (T2DM). OBJECTIVE: We examined the incidence of T2DM, associated factors and mean time to outcome in PLH under cART. METHOD: Data for this multicenter cohort study were obtained from PLH aged over 18, who started cART in 13 Brazilian sites from 2003 to 2013. Factors associated with incident T2DM were evaluated by Cox multiple regression models. RESULTS: A total of 6724 patients (30,997.93 person-years) were followed from January 2003 to December 2016. A T2DM incidence rate of 17.3/1000 person-years (95%CI 15.8-18.8) was observed. Incidence of isolated hypertriglyceridemia and impaired fasting glucose (IFG) were 84.3 (95%CI 81.1-87.6) and 14.5/1000 person-years (95%CI 13.2-15.9), respectively. Mean time to T2DM onset was 10.5 years (95%CI 10.3-10.6). Variables associated with incident T2DM were age 40-50 [Hazard Ratio (HR) 1.7, 95%CI 1.4-2.1] and ≥ 50 years (HR 2.4, 95%CI 1.9-3.1); obesity (HR 2.1, 95%CI 1.6-2.8); abnormal triglyceride/HDL-cholesterol ratio (HR 1.8, 95%CI 1.51-2.2). IFG predicted T2DM (HR 2.6, 95%CI 1.7-2.5) and occurred on average 3.3 years before diabetes onset. Exposure to stavudine for ≥ 2 years was independently associated with incident T2DM [HR 1.6, 95%CI 1.0-2.2). CONCLUSION: Brazilian PLH under cART are at significant risk of developing T2DM and share risk factors for diabetes onset with the general population, such as older age, obesity, and having metabolic abnormalities at baseline. Moreover, stavudine use was independently associated with incident T2DM. Identifying PLH at a higher risk of T2DM can help caretakers trigger health promotion and establish specific targets for implementation of preventive measures.

Stavudine exposure results in developmental abnormalities by causing DNA damage, inhibiting cell proliferation and inducing apoptosis in mouse embryos.

Stavudine is an anti-AIDS drug widely used to prevent HIV transmission from pregnant mothers to the fetuses in underdeveloped countries for its low price. However, there is still a controversy on whether stavudine affects embryo development. In the current study, embryotoxicity of stavudine was evaluated using cultured mouse embryos with the concentrations: 5, 10, 15 µM and vehicle control. The data indicated that the effect of stavudine was dose-dependent at early neurogenesis. Stavudine exposure reduced somite numbers, yolk sac diameter, crown-rump length, and increased the rate of embryonic degeneration compared with the control. We chose the lowest but clearly toxic concentration: 5 µM to investigate the molecular mechanisms of the damage. At the molecular level, stavudine produced DNA damage, increased the levels of the phospho-CHK1 and cleaved-caspase-3, and decreased the expression level of proliferating cell nuclear antigen. These changes indicated that stavudine caused a coordinated DNA damage response, inhibited cell proliferation, and induced apoptosis in the embryos. Collectively these results suggest that stavudine exposure disturbs the embryonic development, and its use in pregnant mothers should be re-examined.