Potential for new antiretrovirals to address unmet needs in the management of HIV-1 infection

Preclinical profile of BI 224436, a novel HIV-1 non-catalytic-site integrase inhibitor

BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3'-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC50s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 μM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC95 values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.

Synthesis, docking, and biological studies of phenanthrene β-diketo acids as novel HIV-1 integrase inhibitors

In the present study we report the synthesis of halogen-substituted phenanthrene β-diketo acids as new HIV-1 integrase inhibitors. The target phenanthrenes were obtained using both standard thermal- and microwave-assisted synthesis. 4-(6-Chlorophenanthren-2-yl)-2,4-dioxobutanoic acid (18) was the most active compound of the series, inhibiting both 3'-end processing (3'-P) and strand transfer (ST) with IC50 values of 5 and 1.3 μM, respectively. Docking studies revealed two predominant binding modes that were distinct from the binding modes of raltegravir and elvitegravir, and suggest a novel binding region in the IN active site. Moreover, these compounds are predicted not to interact significantly with some of the key amino acids (Q148 and N155) implicated in viral resistance. Therefore, this series of compounds can further be investigated for a possible chemotype to circumvent resistance to clinical HIV-1 IN inhibitors.

3-Hydroxy-6,7-dihydropyrimido[2,1-c][1,4]oxazin-4(9H)-ones as new HIV-1 integrase inhibitors WO2011046873 A1

Since the discovery of raltegravir, the first FDA-approved integrase inhibitor, Merck and other pharmaceutical companies have continued their research programs in order to introduce novel molecules as second generation integrase inhibitors. Elvitegravir (Japan Tobacco/Gilead) and dolutegravir (Shionogi/GlaxoSmithKline) are in advanced stages of clinical development. Bristol-Myers Squibb has developed molecules leading to BMS-707035, which was stopped at the Phase II clinical trial stage. Herein is presented the last patent from this company where, in particular, new 3-hydroxy-6,7-dihydropyrimido[2,1-c][1,4]oxazin-4(9H)-ones are synthesized and their biological properties given.

Factors associated with complete adherence to HIV combination antiretroviral therapy

PURPOSE

To assess factors associated with adherence, particularly pill burden, to combination antiretroviral therapy (cART) using multivariate models.

METHOD

A cross-sectional survey of US adults with a self-reported diagnosis of HIV/AIDS was conducted between April and May 2007. Respondents on a cART regimen of at least 2 nucleoside reverse transcriptase inhibitors plus at least 1 protease inhibitor or non-nucleoside reverse transcriptase inhibitor (n = 461) were included in the analytic sample. Multiple logistic regression models determined independent predictors of complete adherence (defined as never missing or skipping an antiretroviral dose).

RESULTS

Fifty-four percent of respondents reported complete adherence to cART. Adherent respondents reported a lower percentage of hospitalizations (11% vs 28%; P < .0001) and emergency room visits (26% vs 34%; P < .09). Respondents taking the single tablet efavirenz/emtricitabine/tenofovir fixed-dose regimen were significantly more likely to have complete adherence than respondents taking other cART regimens (odds ratio [OR] 2.1, P < .05), and higher imputed daily HIV pill count was associated with lower likelihood of complete adherence (OR 0.93, P < .05).

CONCLUSION

This study shows the negative impact of higher pill burden on medication adherence, an important factor associated with treatment outcomes in patients with HIV/AIDS.

2-hydroxyisoquinoline-1,3(2H,4H)-diones as inhibitors of HIV-1 integrase and reverse transcriptase RNase H domain: influence of the alkylation of position 4

We report herein the synthesis of a series of fifteen 2-hydroxyisoquinoline-1,3(2H,4H)-dione derivatives. Alkyl and arylalkyl groups were introduced on position 4 of the basis scaffold. All the compounds presented poor inhibitory properties against HIV-1 reverse transcriptase ribonuclease H (RNase H). Four compounds inhibited HIV-1 integrase at a low micromolar level. A docking study using the later crystallographic data available for PFV integrase allowed us to explain the slightly improved integrase inhibitory activities of 4-pentyl and 4-(3-phenylpropyl)-2-hydroxyisoquinoline-1,3(2H,4H)-diones, when compared to the basis scaffold. Physicochemical studies were consistent with 1:1 and 1:2 (metal/ligand) stoichiometries of the magnesium complexes in solution. Unfortunately all tested compounds exhibited high cellular cytotoxicity in cell culture which limited their applications as antiviral agents. However these identified integrase inhibitors provide a very good basis for the development of new hits.

Raltegravir: The evidence of its therapeutic value in HIV-1 infection

Introduction:

The antiretroviral treatment paradigm for human immunodeficiency virus-1 (HIV-1) infection has undergone a significant change with the addition of a new class of therapeutic agents targeting HIV-1 integrase (IN). IN inhibitors prevent the integration of viral DNA into the human genome and terminate the viral life cycle. As the first member of this new class of anti-HIV drugs, raltegravir has shown promising results in the clinic.

Aims:

To review the emerging evidence for the use of the IN inhibitor raltegravir in the treatment of HIV-1 infection.

Evidence review:

Strong evidence shows that raltegravir is effective in reducing the viral load to less than 50 copies/mL and increasing CD4 cell count in treatment-experienced patients with triple-drug class-resistant HIV-1 infection. Substantial evidence also indicates that while raltegravir is able to achieve treatment response in patients with drug-resistant HIV-1, it is susceptible to development of resistance. Raltegravir should be used with at least one other active drug. In addition to its use in salvage therapy upon failure of first-line antiretroviral treatment, a raltegravir-based treatment regimen may also be effective as initial therapy. Substantial evidence also shows that raltegravir-based treatment regimen is well tolerated with minimal clinically severe adverse events and toxicities. Modeling studies suggest a cost-effectiveness of US$21,339 per quality-adjusted life year gained with raltegravir use, though further direct evidence on quality of life and cost-effectiveness is needed.

Place in therapy:

Raltegravir shows significant and sustained virologic and immunologic response in combination with other antiretrovirals in treatment-experienced HIV-1 infected patients who show evidence of viral replication or multidrug-resistant HIV-1 strains, without any significant tolerability issues.

Nonnucleoside reverse transcriptase inhibitor resistance and the role of the second-generation agents

OBJECTIVE

To review the current state of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance, discuss the promising role of second-generation NNRTIs, and provide insight into their clinical utility.

DATA SOURCES

Articles were identified through searches of MEDLINE (May 2000-August 2009) and International Pharmaceutical Abstracts (May 1998-August 2009), using the key words etravirine, rilpivirine, TMC125, TMC278, diarylpyrimidine, NNRTI, and resistance.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials, resistance studies, and pharmacokinetic data were selected for review.

DATA SYNTHESIS

NNRTIs are an integral class of antiretroviral agents utilized for the treatment of HIV-1 infection. These agents have become preferred therapy options for treatment-naïve individuals per treatment guideline recommendations and have gained increased popularity over protease inhibitor-based antiretroviral therapy. However, available NNRTIs possess inherent characteristics, such as low genetic barrier to resistance and high degree of cross-resistance, that limit their use in HIV therapy. Due to the growing utilization of this highly efficacious antiretroviral class and the increased capability for resistance development, many HIV-infected patients have experienced treatment failure of an NNRTI. Cross-resistance makes other first-generation NNRTI agents unavailable for future use. Etravirine and rilpivirine are second-generation NNRTIs that are not significantly hampered by cross-resistance and possess potent antiretroviral activity against current NNRTI-resistant viral strains. These agents provide new and important therapy options for many HIV-infected patients.

CONCLUSIONS

NNRTI resistance is an increasing problem that may impair the chances for therapeutic success in HIV-infected patients. Novel agents such as etravirine and rilpivirine provide new, sensitive options for patients and significantly improve the rate of virologic suppression when appropriately applied.

Recent Advances in Pharmacotherapy

Many unique and clinically important medications were approved by the Food and Drug Administration from December 2007 through May 2008 for various conditions encountered in an internal medicine setting. These new treatments dramatically vary in their targeted body system and include agents for the cardiovascular system (nebivolol), central nervous system (desvenlafaxine), gastrointestinal tract (certolizumab, methylnaltrexone, and alvimopan), immunological function (etravirine), and metabolic function (sapropterin). This article discusses medications by their respective body system. Each review is comprised of an overview of the Food and Drug Administration–approved indication and the drug’s role in treatment of that disease state. Current dosing guidance, clinical efficacy and clinically relevant adverse drug reactions, drug interactions, contraindications, and precautions are also presented. This review is designed to focus on the new molecular entities and biological approvals clinicians may potentially encounter in an internal medicine practice.

Dynamic patterns of human immunodeficiency virus type 1 integrase gene evolution in patients failing raltegravir-based salvage therapies

OBJECTIVE

: Evaluate HIV-1 subtype B integrase gene evolution in patients failing raltegravir (RAL)-based savage regimens by clonal analysis of the replicating viral quasispecies.

DESIGN

: Seven triple class failure HIV-1 (subtype B)-infected patients, followed at San Raffaele Hospital and enrolled in the RAL Expanded Access Program (MK0518-023), were evaluated. Patients were followed up for 24-48 weeks and due to the absence of other active drugs, RAL was maintained in their regimens even if resistance mutations were detected.

METHODS

: Immunologic and virologic parameters were recorded every 4 weeks, and amplification and clonal analysis of viral populations were performed at baseline and every 4-12 weeks in all patients.

RESULTS

: Resistance to RAL appeared initially associated with selection of single variants (Y143R, Q148R N155H) in the majority of patients; however, in three patients, complex patterns of viral mutations were observed. The clonal analysis of viral quasispecies allowed to describe the evolution of each viral population and the progressive accumulation of RAL resistance-associated mutations and polymorphisms associated with therapy failure.

CONCLUSION

: The complex patterns of resistance mutations observed, including novel variants evolved under continuous RAL pressure, suggesting that they are the result of the equilibrium between drug resistance and enzyme function. Despite the efficacy of this compound, our data discourage its use in a functional monotherapy and maintaining RAL even in presence of RAL resistance-associated mutations may lead to the progressive formation of viral reservoirs with multiple integrase inhibitor-resistant variants that may limit the future efficacy of other integrase inhibitors due to cross-resistance.

The therapeutic implications of timely linkage and early retention in HIV care

Following HIV diagnosis, linkage to outpatient treatment, antiretroviral initiation, and longitudinal retention in care represent the foundation for successful treatment. While prior studies have evaluated these processes in isolation, a systematic evaluation of successive steps in the same cohort of patients has not yet been performed. To ensure optimal long-term outcomes, a better understanding of the interplay of these processes is needed. Therefore, a retrospective cohort study of patients initiating outpatient care at the University of Alabama at Birmingham 1917 HIV=AIDS Clinic between January 2000 and December 2005 was undertaken. Multivariable models determined factors associated with: late diagnosis=linkage to care (initial CD4 < 350 cells=mm3), timely antiretroviral initiation, and retention across the first two years of care. Delayed linkage was observed in two-thirds of the overall sample (n = 567) and was associated with older age (odds ratio [OR] = 1.31 per 10 years; 95%confidence interval [CI] = 1.06-1.62) and African American race (OR = 2.45; 95% CI = 1.60-3.74). Attending all clinic visits (hazard ratio [HR] = 6.45; 95% CI = 4.47-9.31) and lower initial CD4 counts led to earlier antiretroviral initiation. Worse retention in the first 2 years was associated with younger age (OR = 0.68 per 10 years;95% CI = 0.56-0.83), higher baseline CD4 count, and substance abuse (OR = 1.78; 95% CI = 1.16-2.73). Interventions to improve timely HIV diagnosis and linkage to care should focus on older patients and African Americans while efforts to improve retention should address younger patients, those with higher baseline CD4 counts, and substance abuse. Missed clinic visits represent an important obstacle to the timely initiation of antiretroviral therapy. These data inform development of interventions to improve linkage and retention in HIV care, an emerging area of growing importance.