Synthesis, in silico and in vitro anti-cancer studies of phosphorylated derivatives of didanosine targeting MDA-MB-231 breast cancer cell lines.

A series of new phosphorylated derivatives of didanosine were designed, synthesized and evaluated their anticancer effects on human breast cancer cells. Their binding affinities were evaluated against aromatase enzyme and the molecular docking studies demonstrated that 9a, 9h and 9i exhibited high binding interactions than the parent molecule (ddI) and other derivatives; evaluated the aromatase enzyme inhibition. The cell viability, cell proliferation, lactate dehydrogenase showed potential anti-proliferative in dose dependent manner, these results were well correlated with hoesch stain and DNA fragmentation on MDA-MB-231 breast cancer cell lines. Cytotoxicity results disclosed that tryptophan amino acid ester substituted derivative 9i showed potential cell death against MDA-MB-231 cancer cell lines. Furthermore, compound 9i has great potential significance for further investigations (in vivo).

Depletion of Mitochondrial DNA in Differentiated Retinal Pigment Epithelial Cells.

We investigated the effects of treating differentiated retinal pigment epithelial (RPE) cells with didanosine (ddI), which is associated with retinopathy in individuals with HIV/AIDS. We hypothesized that such treatment would cause depletion of mitochondrial DNA and provide insight into the consequences of degradation of RPE mitochondrial function in aging and disease. Treatment of differentiated ARPE-19 or human primary RPE cells with 200 µM ddI for 6-24 days was not cytotoxic but caused up to 60% depletion of mitochondrial DNA, and a similar reduction in mitochondrial membrane potential and NDUFA9 protein abundance. Mitochondrial DNA-depleted RPE cells demonstrated enhanced aerobic glycolysis by extracellular flux analysis, increased AMP kinase activation, reduced mTOR activity, and increased resistance to cell death in response to treatment with the oxidant, sodium iodate. We conclude that ddI-mediated mitochondrial DNA depletion promotes a glycolytic shift in differentiated RPE cells and enhances resistance to oxidative damage. Our use of ddI treatment to induce progressive depletion of mitochondrial DNA in differentiated human RPE cells should be widely applicable for other studies aimed at understanding RPE mitochondrial dysfunction in aging and disease.

Evaluation of a Library of FDA-Approved Drugs for Their Ability To Potentiate Antibiotics against Multidrug-Resistant Gram-Negative Pathogens.

The Prestwick library was screened for antibacterial activity or "antibiotic resistance breaker" (ARB) potential against four species of Gram-negative pathogens. Discounting known antibacterials, the screen identified very few ARB hits, which were strain/drug specific. These ARB hits included antimetabolites (zidovudine, floxuridine, didanosine, and gemcitabine), anthracyclines (daunorubicin, mitoxantrone, and epirubicin), and psychoactive drugs (gabapentin, fluspirilene, and oxethazaine). These findings suggest that there are few approved drugs that could be directly repositioned as adjunct antibacterials, and these will need robust testing to validate efficacy.

Synthesis and Antiviral Activity of Novel Phosphorylated Derivatives of Didanosine Against Newcastle Disease Virus in Chicken.

A series of novel phosphorylated derivatives of didanosine were designed and docking studies were performed with a fusion protein of the Newcastle disease virus (NDV), to develop antiviral compounds against NDV. Based on the docking scores and binding affinities, three derivatives were selected. These compounds were synthesized and characterized by IR, (1) H, (13) C, (31) P, and CHN analysis and mass spectra. They were assessed for their in vitro antiviral activity in DF-1 cells; DDI-10 showed better antiviral activity as evidenced by significant reduction in plaque formation and cytopathic effects. DDI-10 was further evaluated in NDV-infected chicken; the survival rates and antioxidant enzyme levels in brain, liver, and lung tissues were estimated. Superoxide dismutase and catalase were significantly raised, and lipid peroxidation and HA titer levels were decreased upon treatment with 1.5 mg/kg body weight of DDI-10 than with 3 mg/kg body weight of DDI. Further histopathological alterations in NDV-infected tissues were restored in chicken treated with DDI-10. Thus, based on the results from in silico, in vitro, and in vivo assays, the novel phosphorylated DDI-10 might be considered as potent antiviral compound for NDV infection in chicken.

Short Communication: In Vitro Accumulation of Drug Resistance Mutations in Chimeric Infectious Clones Containing Subtype B or C Reverse Transcriptase and Selected with Tenofovir or Didanosine.

Highly active antiretroviral therapy (HAART) contributed to the improvement in the life expectancy of HIV-infected patients. However, the emergence of drug-resistant mutations (DRM) is a major viral factor impacting therapeutic failure. Differences in DRM can occur among HIV-1 subtypes. We evaluate the kinetics of the selection of resistance mutations in vitro analyzing two chimeric clones that contain the reverse transcriptases of subtypes B or C (RTB' and RTC') in cells treated with increasing concentrations of tenofovir disoproxil fumarate (TDF) and didanosine (ddI). The mutation K65R is selected more quickly in RTC' than in RTB' viruses with TDF and ddI, and additional mutations (positions 45, 62, and 68) were selected after K65R fixation. Other primary mutations (M184V and Q151M) were selected with ddI treatment in conjunction with K65R only in RTC' viruses. Both patterns, M184V+K65R and Q151M+K65R, have a significant impact on NRTI resistance. Our data suggest that selection of TDF and ddI DRMs can occur earlier in subtype C HIV in patients when compared to subtype B.

Synthesis of novel 2',3'-didehydro-2',3'-dideoxyinosine phosphoramidate prodrugs and evaluation of their anticancer activity.

An efficient synthesis of 4-chlorophenyl N-alkyl phosphoramidates of 2 ',3 '-didehydro-2 ',3 '-dideoxyinosine employing 4-chlorophenyl phosphoroditetrazolide as a phosphorylating agent is reported. Improved method for the synthesis of 2 ',3 '-didehydro-2 ',3 '-dideoxyinosine starting from inosine is also described. The synthesized phosphoramidates 11-18 were examined for their cytotoxic activity in three human cancer cell lines: cervical (HeLa), oral (KB), and breast (MCF-7) employing sulforhodamine B assay. The highest activity in all investigated cancer cell lines was displayed by phosphoramidate 13 with N-n-propyl substituent.

Amino acid esters substituted phosphorylated emtricitabine and didanosine derivatives as antiviral and anticancer agents.

Owing to the promising antiviral activity of amino acid ester-substituted phosphorylated nucleosides in the present study, a series of phosphorylated derivatives of emtricitabine and didanosine substituted with bioactive amino acid esters at P-atom were synthesized. Initially, molecular docking studies were screened to predict their molecular interactions with hemagglutinin-neuraminidase protein of Newcastle disease virus and E2 protein of human papillomavirus. The title compounds were screened for their antiviral ability against Newcastle disease virus (NDV) by their in ovo study in embryonated chicken eggs. Compounds 5g and 9c exposed well mode of interactions with HN protein and also exhibited potential growth of NDV inhibition. The remaining compounds exhibited better growth of NDV inhibition than their parent molecules, i.e., emtricitabine (FTC) and didanosine (ddI). In addition, the in vitro anticancer activity of all the title compounds were screenedagainst HeLa cell lines at 10 and 100 µg/mL concentrations. The compounds 5g and 9c showed an effective anticancer activity than that of the remaining title compounds with IC50 values of 40 and 60 µg/mL, respectively. The present in silico and in ovo antiviral and in vitro anticancer results of the title compounds are suggesting that the amino acid ester-substituted phosphorylated FTC and ddI derivatives, especially 5g and 9c, can be used as NDV inhibitors and anticancer agents for the control and management of viral diseases with cancerous condition.

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.

Profile of leukocyte-endothelial cell interactions induced in venules and arterioles by nucleoside reverse-transcriptase inhibitors in vivo.

BACKGROUND: There is controversy regarding cardiovascular (CV) toxicity of the nucleoside reverse-transcriptase inhibitors used to treat human immunodeficiency virus infection. METHODS: We evaluated the effects of nucleoside reverse-transcriptase inhibitors on leukocyte-endothelium interactions, a hallmark of CV diseases, in rat mesenteric vessels using intravital microscopy and in human arterial cells using a flow chamber system. RESULTS: Abacavir and didanosine increased rolling, adhesion and emigration in rat vessels. These effects were reversed with antibodies against Macrophage-1 antigen (Mac-1) or intercellular adhesion molecule 1 and were reproduced in human cells. Lamivudine, zidovudine, emtricitabine, and tenofovir had no effects. CONCLUSIONS: Our results support the association of abacavir and didanosine with CV diseases.

Identifying chemicals with potential therapy of HIV based on protein-protein and protein-chemical interaction network.

Acquired immune deficiency syndrome (AIDS) is a severe infectious disease that causes a large number of deaths every year. Traditional anti-AIDS drugs directly targeting the HIV-1 encoded enzymes including reverse transcriptase (RT), protease (PR) and integrase (IN) usually suffer from drug resistance after a period of treatment and serious side effects. In recent years, the emergence of numerous useful information of protein-protein interactions (PPI) in the HIV life cycle and related inhibitors makes PPI a new way for antiviral drug intervention. In this study, we identified 26 core human proteins involved in PPI between HIV-1 and host, that have great potential for HIV therapy. In addition, 280 chemicals that interact with three HIV drugs targeting human proteins can also interact with these 26 core proteins. All these indicate that our method as presented in this paper is quite promising. The method may become a useful tool, or at least plays a complementary role to the existing method, for identifying novel anti-HIV drugs.

Anti-HIV efficacy and biodistribution of nucleoside reverse transcriptase inhibitors delivered as squalenoylated prodrug nanoassemblies.

Due to their hydrophilic nature, most nucleoside reverse transcriptase inhibitors (NRTIs) display a variable bioavailability after oral administration and a poor control over their biodistribution, thus hampering their access to HIV sanctuaries. The limited cellular uptake and activation in the triphosphate form of NRTIs further restrict their efficacy and favour the emergence of viral resistance. We have shown that the conjugation of squalene (sq) to the nucleoside analogues dideoxycytidine (ddC) and didanosine (ddI) leads to amphiphilic prodrugs (ddC-sq and ddI-sq) that spontaneously self-organize in water as stable nanoassemblies of 100-300 nm. These nanoassemblies can also be formulated with polyethylene glycol coupled to either cholesterol (Chol-PEG) or squalene (sq-PEG). When incubated with peripheral blood mononuclear cells (PBMCs) in vitro infected with HIV, the NRTI-sq prodrugs enhanced the antiviral efficacy of the parent NRTIs, with a 2- to 3-fold decrease of the 50% effective doses and a nearly 2-fold increase of the selectivity index. This was also the case with HIV-1 strains resistant to ddC and/or ddI. The enhanced antiviral activity of ddI-sq was correlated with an up to 5-fold increase in the intracellular concentration of the corresponding pharmacologically active metabolite ddA-TP. The ddI-sq prodrug was further investigated in vivo by the oral route, the preferred route of administration of NRTIs. Pharmacokinetics studies performed on rats showed that the prodrug maintained low amounts of free ddI in the plasma. Administration of (3)H-ddI-sq led to radioactivity levels higher in the plasma and relevant organs in HIV infection as compared to administration of free (3)H-ddI. Taken together, these results show the potential of the squalenoylated prodrugs of NRTIs to enhance their absorption and improve their biodistribution, but also to enhance their intracellular delivery and antiviral efficacy towards HIV-infected cells.

Scoring methods for building genotypic scores: an application to didanosine resistance in a large derivation set.

BACKGROUND: Several attempts have been made to determine HIV-1 resistance from genotype resistance testing. We compare scoring methods for building weighted genotyping scores and commonly used systems to determine whether the virus of a HIV-infected patient is resistant. METHODS AND PRINCIPAL FINDINGS: Three statistical methods (linear discriminant analysis, support vector machine and logistic regression) are used to determine the weight of mutations involved in HIV resistance. We compared these weighted scores with known interpretation systems (ANRS, REGA and Stanford HIV-db) to classify patients as resistant or not. Our methodology is illustrated on the Forum for Collaborative HIV Research didanosine database (N = 1453). The database was divided into four samples according to the country of enrolment (France, USA/Canada, Italy and Spain/UK/Switzerland). The total sample and the four country-based samples allow external validation (one sample is used to estimate a score and the other samples are used to validate it). We used the observed precision to compare the performance of newly derived scores with other interpretation systems. Our results show that newly derived scores performed better than or similar to existing interpretation systems, even with external validation sets. No difference was found between the three methods investigated. Our analysis identified four new mutations associated with didanosine resistance: D123S, Q207K, H208Y and K223Q. CONCLUSIONS: We explored the potential of three statistical methods to construct weighted scores for didanosine resistance. Our proposed scores performed at least as well as already existing interpretation systems and previously unrecognized didanosine-resistance associated mutations were identified. This approach could be used for building scores of genotypic resistance to other antiretroviral drugs.

Vitamin D attenuates nucleoside reverse transcriptase inhibitor induced human skeletal muscle mitochondria DNA depletion.

OBJECTIVE: To evaluate the impact of the active metabolite of vitamin D, 1α,25-dihydroxycholecalciferol (1,25D3), on nucleoside reverse transcriptase inhibitor (NRTI) induced mitochondrial DNA (mtDNA) depletion in human skeletal muscle myoblasts and myotubes. DESIGN: mtDNA was quantified in human skeletal muscle myoblasts and myotubes following 1,25D3 and NRTI treatment using real-time PCR. METHODS: Human skeletal muscle myoblasts and myotubes were treated with didanosine (ddI), stavudine (d4T), zidovudine (ZDV), lamivudine (3TC) and abacavir (ABC) alone or in combination either in the presence or absence of 1,25D3 for 5 days. Cells were harvested, DNA extracted and mtDNA quantified. RESULTS: ddI and ddI-d4T significantly decreased both myoblast and myotube mtDNA in the absence of 1,25D3 compared with untreated controls (P≤0.029). In addition, the ZDV-3TC combination resulted in a 47% decrease in myotube mtDNA (P=0.005). 1,25D3 increased myotube mtDNA levels in ddI, ZDV, 3TC, ABC, ddI-d4T, d4T-3TC, ZDV-3TC, ZDV-ABC and ZDV-3TC-ABC-containing regimens and myoblast mtDNA levels in ddI, d4T, ZDV, 3TC, ddI-d4T, ZDV-3TC and ZDV-ABC-containing regimens. Of note, 1,25D3 protected against myotube mtDNA depletion following ZDV-3TC treatment, rendering them similar to 1,25D3 untreated controls (P=0.62), and increased both myotube and myoblast mtDNA two to three-fold in ddI-containing regimens (P<0.05). CONCLUSION: 1,25D3 confers a protective effect against NRTI-induced mitochondrial toxicity in skeletal muscle myoblasts and myotubes. These findings support a protective role for vitamin D in preventing mitochondrial toxicity and suggest that supplemental vitamin D may protect against NRTI-associated mitochondrial toxicity.

VS411 reduced immune activation and HIV-1 RNA levels in 28 days: randomized proof-of-concept study for antiviral-hyperactivation limiting therapeutics.

BACKGROUND: A new class of antiretrovirals, AntiViral-HyperActivation Limiting Therapeutics (AV-HALTs), has been proposed as a disease-modifying therapy to both reduce Human Immunodeficiency Virus Type 1 (HIV-1) RNA levels and the excessive immune activation now recognized as the major driver of not only the continual loss of CD4(+) T cells and progression to Acquired Immunodeficiency Syndrome (AIDS), but also of the emergence of both AIDS-defining and non-AIDS events that negatively impact upon morbidity and mortality despite successful (ie, fully suppressive) therapy. VS411, the first-in-class AV-HALT, combined low-dose, slow-release didanosine with low-dose hydroxycarbamide to accomplish both objectives with a favorable toxicity profile during short-term administration. Five dose combinations were administered as VS411 to test the AV-HALT Proof-of-Concept in HIV-1-infected subjects. METHODS: Multinational, double-blind, 28-day Phase 2a dose-ranging Proof-of-Concept study of antiviral activity, immunological parameters, safety, and genotypic resistance in 58 evaluable antiretroviral-naïve HIV-1-infected adults. Randomization and allocation to study arms were carried out by a central computer system. Results were analyzed by ANOVA, Kruskal-Wallis, ANCOVA, and two-tailed paired t tests. RESULTS: VS411 was well-tolerated, produced significant reductions of HIV-1 RNA levels, increased CD4(+) T cell counts, and led to significant, rapid, unprecedented reductions of immune activation markers after 28 days despite incomplete viral suppression and without inhibiting HIV-1-specific immune responses. The didanosine 200 mg/HC 900 mg once-daily formulation demonstrated the greatest antiviral efficacy (HIV-1 RNA: -1.47 log(10) copies/mL; CD4(+) T cell count: +135 cells/mm(3)) and fewest adverse events. CONCLUSIONS: VS411 successfully established the Proof-of-Concept that AV-HALTs can combine antiviral efficacy with rapid, potentially beneficial reductions in the excessive immune system activation associated with HIV-1 disease. Rapid reductions in markers of immune system hyperactivation and cellular proliferation were obtained despite the fact that VS411 did not attain maximal suppression of HIV RNA, suggesting this effect was due to the HALT component. TRIAL REGISTRATION: ITEudraCT 2007-002460-98.

Submicron-size biodegradable polymer-based didanosine particles for treating HIV at early stage: an in vitro study.

Human immunodeficiency viruses (HIV) hide themselves in macrophages at the early stage of infection. Delivering drug in a sustained manner from polymeric nanoparticles in those cells could control the disease effectively. The study was intended to develop poly(d,l-lactic-co-glycolic acid)-based nanoparticles containing didanosine and to observe their uptake by macrophages in vitro. Various physicochemical evaluations related to nanoparticles, such as drug-excipient interaction, surface morphology, particle size, zeta potential, polydispersity index, drug loading, in vitro drug release and nanoparticle-uptake by macrophages in vitro were determined. Homogenising speeds and drug-polymer ratio varied drug loading and polydispersity index of nanoparticles, providing sustained drug release. Dimethyl sulphoxide/polyethylene glycol improved drug loading predominantly. Nanoparticle-uptake by macrophages was concentration dependent. Experimental nanoparticles successfully transported didanosine to macrophages in vitro, suggesting reduction of dose, thus minimising toxicity and side effects. Developed nanoparticle may control HIV infection effectively at an early stage.

Azidothymidine and other chain terminators are mutagenic for template-switch-generated genetic mutations.

The accumulation of mutations causes cell lethality and can lead to carcinogenesis. An important class of mutations, which are associated with mutational hotspots in many organisms, are those that arise by nascent strand misalignment and template-switching at the site of short repetitive sequences in DNA. Mutagens that strongly and specifically affect this class, which is mechanistically distinct from other mutations that arise from polymerase errors or by DNA template damage, are unknown. Using Escherichia coli and assays for specific mutational events, this study defines such a mutagen, 3'-azidothymidine [zidovudine (AZT)], used widely in the treatment and prevention of HIV/AIDS. At sublethal doses, AZT has no significant effect on frame shifts and most base-substitution mutations. AT-to-CG transversions and deletions at microhomologies were enhanced modestly by AZT. AZT strongly stimulated the "template-switch" class of mutations that arise in imperfect inverted repeat sequences by DNA-strand misalignments during replication, presumably through its action as a chain terminator during DNA replication. Chain-terminating 2'-3'-didehydro 3'-deoxythymidine [stavudine (D4T)] and 2'-3'-dideoxyinosine [didanosine (ddI)] likewise stimulated template-switch mutagenesis. These agents define a specific class of mutagen that promotes template-switching and acts by stalling replication rather than by direct nucleotide base damage.

E17A mutation in HIV-1 Vpr confers resistance to didanosine in association with thymidine analog mutations.

BACKGROUND: HIV-1 accessory Vpr protein is involved in the reverse transcription process and has been shown to modulate the virus mutation rate. This process may play a role in the kinetics of appearance of drug resistance mutations under antiretroviral treatment. METHODS: Vpr sequences were analyzed from plasma viruses derived from 97 HIV-1-infected individuals failing antiretroviral treatment and 63 antiretroviral-naïve patients. Vpr genetic variability was analyzed for association with specific drug treatment and drug resistance mutations. Biological and virological experiments were employed to characterize a mutation in Vpr found to be associated with virological failure. RESULTS: E17A mutation located in the first α-helix of Vpr was more prevalent in HAART-treated individuals compared to untreated individuals. E17A was associated with thymidine analog mutations (TAMs) in reverse transcriptase M41L, L210W and T215Y and with the use of didanosine in the patients' treatment histories. E17A had no impact on the biochemical and functional properties of Vpr, and did not affect kinetics of replication of wild-type or TAMs-containing viruses. However, its association with TAMs and the use of didanosine was consistent with phenotypic susceptibility assays showing a significant 3-fold decrease in didanosine susceptibility of viruses harboring Vpr E17A combined with TAMs compared to viruses harboring TAMs alone. CONCLUSION: These findings highlight a novel role of Vpr in HIV-1 drug resistance. Vpr E17A confers resistance to didanosine when associated with TAMs. Whether Vpr E17A facilitates excision of didanosine is still to be determined.

Impact of lamivudine on HIV and hepatitis B virus-related outcomes in HIV/hepatitis B virus individuals in a randomized clinical trial of antiretroviral therapy in southern Africa.

OBJECTIVE: To examine HIV and hepatitis B virus (HBV)-related outcomes in HIV/HBV-coinfected participants in the PHIDISA II study by use of HBV-active vs. non-HBV-active antiretroviral therapy (ART). DESIGN AND METHODS: PHIDISA II was a randomized study of ART therapy in HIV-infected adults employing zidovudine along with didanosine, or lamivudine along with stavudine in a factorial 2x2 design. HIV/HBV-coinfected participants by randomization received HBV-active or non-HBV-active ART. The following outcomes of interest were examined: immunological recovery and HIV RNA suppression; hepatic flare; HBV DNA suppression; and mortality. RESULTS: HIV/HBV coinfection was present in 106 of 1771 (6%) of participants. Participants with HIV/HBV coinfection were more likely to be men, and have higher baseline alanine aminotransferase, lower albumin, and lower platelets than those with HIV monoinfection. Median CD4 cell gain and HIV RNA suppression was similar across all groups. Hepatic flare was observed in 9.4% of coinfected and 0.02% monoinfected participants. HBV DNA suppression (<55 IU/ml) at week 48 was observed in only 33% of those on lamivudine vs. 13% in those on no HBV-active drugs (P = 0.13). Mortality over follow-up was significantly greater in coinfected (17%) than monoinfected (11%) participants (P = 0.04). CONCLUSION: In summary, the use of lamivudine-containing ART in HIV/HBV participants in PHIDISA II resulted in little additional benefit over that of ART itself and failed to impact on the greater mortality in this group. These data provide strong support for recent guidelines advocating the use of tenofovir in all HIV-HBV-coinfected individuals initiating ART.

Antiviral hyperactivation-limiting therapeutics as a novel class for the treatment of HIV/AIDS: focus on VS411.

INTRODUCTION: Immune activation plays a central pathogenetic role in both HIV-1 replication and depletion of CD4(+) T cells leading to disease progression and the onset of the AIDS. While current antiretroviral therapies suppress viral replication to undetectable levels, they do not normalize the excessive level of T-cell activation and proliferation. A new class of anti-HIV-1 drugs known as antiviral hyperactivation-limiting therapeutics (AV-HALTs) combines direct antiviral activity with an antiproliferative action to limit the hyperactivation of the immune system now recognized as the key driver of the progressive loss of CD4(+) T cells that occurs over the natural course of the HIV-1 infection. AREAS COVERED: Areas covered include preclinical, Phase I and Phase IIa studies of VS411, the first drug product in a novel class of anti-HIV drugs, AV-HALT agents. EXPERT OPINION: The two drug combination VS411 safely achieved the goals established for the AV-HALT class based on the results of a Phase IIA proof-of-concept study. Additional work is underway to identify and develop new agents that combine the dual attributes of AV-HALTs, direct reduction of both HIV-1 viral load and markers of excessive immune activation, in a single molecule.