Safety and efficacy of the HIV-1 attachment inhibitor prodrug BMS-663068 in treatment-experienced individuals: 24 week results of AI438011, a phase 2b, randomised controlled trial

Design and synthesis of Meldrum's acid based 7-azaindole anchored 1,2,3-triazole hybrids as anticancer agents

A series of Meldrum's acid, 7-azaindole and 1,2,3-triazole hybrids were synthesized and evaluated for their in vitro anticancer activity against five different cancer cell lines viz. MCF-7 (breast cancer), HeLa (cervical cancer), DU-145 (prostate cancer), HepG2 (liver cancer) and K562 (myelogenous leukemia cell). Among the series, compound 6b containing a 4-methyl substitution showed potent activity against HeLa cell line. Cell cycle analysis revealed that compound 6b induced cell cycle arrest at the G2/M phase and induced apoptosis. Apoptotic activity was further confirmed by Hoechst staining and Annexin V-FITC assay. Compound 6b has been found to exhibit higher activity in all four cell lines, with IC50 values of 6.67 ± 0.39 μM, 4.44 ± 0.32 μM, 12.38 ± 0.51 μM and 9.97 ± 0.25 μM against MCF-7, HeLa, DU-145 and HepG2 cell lines respectively. Compounds 6m (9.68 ± 0.10 μM) and 6n (9.52 ± 0.38 μM), which have dimethoxy and trimethoxy substitutions, respectively, have demonstrated significant anticancer activity against HeLa cells compared to the other cells. The molecular docking study of ligand 6b against the crystal structure of EGFR and Mcl-1 scored notable binding energy values and displayed important interactions like H-bond, π-cation and other hydrophobic interactions.

Consensus recommendations for the use of novel antiretrovirals in persons with HIV who are heavily treatment-experienced and/or have multidrug-resistant HIV-1: Endorsed by the American Academy of HIV Medicine, American College of Clinical Pharmacy

Treatment options are currently limited for persons with HIV-1 (PWH) who are heavily treatment-experienced and/or have multidrug-resistant HIV-1. Three agents have been approved by the U.S. Food and Drug Administration (FDA) since 2018, representing a significant advancement for this population: ibalizumab, fostemsavir, and lenacapavir. However, there is a paucity of recommendations endorsed by national and international guidelines describing the optimal use (e.g., selection and monitoring after initiation) of these novel antiretrovirals in this population. To address this gap, a modified Delphi technique was used to develop these consensus recommendations that establish a framework for initiating and managing ibalizumab, fostemsavir, or lenacapavir in PWH who are heavily treatment-experienced and/or have multidrug-resistant HIV-1. In addition, future areas of research are also identified and discussed.

Mechanism of action, resistance, interaction, pharmacokinetics, pharmacodynamics, and safety of fostemsavir

The Food and Drug Administration (FDA) has licensed many antiretroviral medications to treat human immunodeficiency virus type 1 (HIV-1), however, treatment options for people with multi-drug resistant HIV remain limited. Medication resistance, undesirable effects, prior tolerance, and previous interlacement incapacity to deliver new drug classes all lead to the requirement for new medication classes and drug combination therapy. Fostemsavir (FTR) is a new CD-4 attachment inhibitor medicine that was recently authorized by the United States FDA to treat HIV-1. In individuals with multidrug-resistant (MDR) HIV-1, FTR is well tolerated and virologically active. According to recent investigations, drug combination therapy can positively affect MDR-HIV. The mechanism of action, resistance, interaction, pharmacokinetics, pharmacodynamics, and safety of FTR has been highlighted in this review.

Structure-Based Identification of Natural-Product-Derived Compounds with Potential to Inhibit HIV-1 Entry

Broadly neutralizing antibodies (bNAbs) are potent in neutralizing a wide range of HIV strains. VRC01 is a CD4-binding-site (CD4-bs) class of bNAbs that binds to the conserved CD4-binding region of HIV-1 envelope (env) protein. Natural products that mimic VRC01 bNAbs by interacting with the conserved CD4-binding regions may serve as a new generation of HIV-1 entry inhibitors by being broadly reactive and potently neutralizing. This study aimed to identify compounds that mimic VRC01 by interacting with the CD4-bs of HIV-1 gp120 and thereby inhibiting viral entry into target cells. Libraries of purchasable natural products were virtually screened against clade A/E recombinant 93TH057 (PDB: 3NGB) and clade B (PDB ID: 3J70) HIV-1 env protein. Protein-ligand interaction profiling from molecular docking and dynamics simulations showed that the compounds had intermolecular hydrogen and hydrophobic interactions with conserved amino acid residues on the CD4-binding site of recombinant clade A/E and clade B HIV-1 gp120. Four potential lead compounds, NP-005114, NP-008297, NP-007422, and NP-007382, were used for cell-based antiviral infectivity inhibition assay using clade B (HXB2) env pseudotype virus (PV). The four compounds inhibited the entry of HIV HXB2 pseudotype viruses into target cells at 50% inhibitory concentrations (IC₅₀) of 15.2 µM (9.7 µg/mL), 10.1 µM (7.5 µg/mL), 16.2 µM (12.7 µg/mL), and 21.6 µM (12.9 µg/mL), respectively. The interaction of these compounds with critical residues of the CD4-binding site of more than one clade of HIV gp120 and inhibition of HIV-1 entry into the target cell demonstrate the possibility of a new class of HIV entry inhibitors.

Week 96 Genotypic and Phenotypic Results of the Fostemsavir Phase 3 BRIGHTE Study in Heavily Treatment-Experienced Adults Living with Multidrug-Resistant HIV-1

In the phase 3 BRIGHTE study in heavily treatment-experienced adults with multidrug-resistant HIV-1, fostemsavir plus optimized background therapy (OBT) resulted in sustained rates of virologic suppression through 96 weeks. HIV-1 RNA <40 copies/mL was achieved in 163/272 (60%) Randomized Cohort (RC) participants (with 1 or 2 remaining approved fully active antiretrovirals) and 37/99 (37%) Non-randomized Cohort (NRC) participants (with 0 fully active antiretrovirals). Here we report genotypic and phenotypic analyses of HIV-1 samples from 63/272 (23%) RC participants and 49/99 (49%) NRC participants who met protocol-defined virologic failure (PDVF) criteria through Week 96. The incidence of PDVF was as expected in this difficult-to-treat patient population and, among RC participants, was comparable regardless of the presence of predefined gp120 amino acid substitutions that potentially influence phenotypic susceptibility to temsavir (S375H/I/M/N/T, M426L, M434I, M475I) or baseline temsavir 50% inhibitory concentration fold change (IC₅₀ FC). The incidence of PDVF was lower among participants with higher overall susceptibility score to newly used antiretrovirals (OSS-new), indicating that OSS-new may be a preferred predictor of virologic outcome in heavily treatment-experienced individuals. Predefined gp120 substitutions, most commonly M426L or S375N, were emergent on treatment in 24/50 (48%) RC and 33/44 (75%) NRC participants with PDVF, with related increases in temsavir IC₅₀ FC. In BRIGHTE, PDVF was not consistently associated with treatment-emergent genotypic or phenotypic changes in susceptibility to temsavir or to antiretrovirals in the initial OBT. Further research will be needed to identify which factors are most likely to contribute to virologic failure in this heavily treatment-experienced population (ClinicalTrials.gov, NCT02362503).

Pharmacokinetics of Temsavir, the Active Moiety of the HIV-1 Attachment Inhibitor Prodrug, Fostemsavir, Coadministered with Cobicistat, Etravirine, Darunavir/Cobicistat, or Darunavir/Ritonavir with or without Etravirine in Healthy Participants

Fostemsavir is a prodrug of temsavir, a first-in-class attachment inhibitor that binds directly to HIV-1 gp120, preventing initial viral attachment and entry into host CD4⁺ T cells with demonstrated efficacy in phase 2 and 3. Temsavir is a P-glycoprotein and breast cancer resistance protein (BCRP) substrate; its metabolism is mediated by esterase and CYP3A4 enzymes. Drugs that induce or inhibit CYP3A, P-glycoprotein, and BCRP may affect temsavir concentrations. Understanding potential drug-drug interactions (DDIs) following fostemsavir coadministration with antiretrovirals approved for HIV-1-infected treatment-experienced patients, including darunavir plus cobicistat (DRV/c) or DRV plus low-dose ritonavir (DRV/r) and etravirine, is clinically relevant. Open-label, single-sequence, multiple-dose, multicohort DDI studies were conducted in healthy participants (n = 46; n = 32). The primary objective was to assess the effects of DRV/r, etravirine, DRV/r plus etravirine, cobicistat, and DRV/c on temsavir systemic exposures; safety was a secondary objective. Compared with fostemsavir alone, coadministration with DRV/r increased the temsavir maximum observed plasma concentration (C_max), area under the concentration-time curve in one dosing interval (AUC_tau), and plasma trough concentration (C_tau) by 52%, 63%, and 88%, respectively, while etravirine decreased the temsavir C_max, AUC_tau, and C_tau by ∼50% each. DRV/r plus etravirine increased the temsavir C_max, AUC_tau, and C_tau by 53%, 34%, and 33%, respectively. Compared with fostemsavir alone, coadministration with cobicistat increased the temsavir C_max, AUC_tau, and C_tau by 71%, 93%, and 136%, respectively; DRV/c increased the temsavir C_max, AUC_tau, and C_tau by 79%, 97%, and 124%, respectively. Fostemsavir with all combinations was generally well tolerated. No dose adjustment is required for fostemsavir when coadministered with strong CYP3A inhibitors, P-glycoprotein inhibitors, and modest inducers, including regimens with DRV/r, DRV/c, cobicistat, etravirine, and DRV/r plus etravirine based on the therapeutic margin for temsavir (ClinicalTrials.gov registration no. NCT02063360 and NCT02277600).

Fostemsavir: a first-in-class HIV-1 attachment inhibitor

PURPOSE OF REVIEW

Fostemsavir is a recently Food and Drug Administration-approved HIV-1 attachment inhibitor that binds to HIV-1 gp120 and prevents viral attachment to the cellular CD4 receptor. Here, we review the pharmacology, efficacy, tolerability, and resistance profile of fostemsavir.

RECENT FINDINGS

Fostemsavir is well tolerated and maintains virologic activity in individuals harboring multidrug-resistant HIV-1. In conjunction with optimal background therapy, a majority of heavily treatment-experienced clinical trial participants treated with fostemsavir achieved virologic suppression.

SUMMARY

The approval of fostemsavir represents an important advance for individuals harboring multidrug resistant HIV-1 due to its novel mechanism of action and lack of cross-resistance to other antiretrovirals. Further study will better define the role of resistance testing for fostemsavir and fostemsavir's potential role outside of salvage therapy in heavily treatment-experienced individuals.

Selective elimination of host cells harboring replication-competent human immunodeficiency virus reservoirs: a promising therapeutic strategy for HIV cure

ABSTRACT

Many seminal advances have been made in human immunodeficiency virus (HIV)/AIDS research over the past four decades. Treatment strategies, such as gene therapy and immunotherapy, are yielding promising results to effectively control HIV infection. Despite this, a cure for HIV/AIDS is not envisioned in the near future. A recently published academic study has raised awareness regarding a promising alternative therapeutic option for HIV/AIDS, referred to as "selective elimination of host cells capable of producing HIV" (SECH). Similar to the "shock and kill strategy," the SECH approach requires the simultaneous administration of drugs targeting key mechanisms in specific cells to efficiently eliminate HIV replication-competent cellular reservoirs. Herein, we comprehensively review the specific mechanisms targeted by the SECH strategy. Briefly, the suggested cocktail of drugs should contain (i) latency reversal agents to promote the latency reversal process in replication-competent reservoir cells, (ii) pro-apoptotic and anti-autophagy drugs to induce death of infected cells through various pathways, and finally (iii) drugs that eliminate new cycles of infection by prevention of HIV attachment to host cells, and by HIV integrase inhibitor drugs. Finally, we discuss three major challenges that are likely to restrict the application of the SECH strategy in HIV/AIDS patients.

Innovation in the discovery of the HIV-1 attachment inhibitor temsavir and its phosphonooxymethyl prodrug fostemsavir

The discovery and development of fostemsavir (2), the tromethamine salt of the phosphonooxymethyl prodrug of temsavir (1), encountered significant challenges at many points in the preclinical and clinical development program that, in many cases, stimulated the implementation of innovative solutions in order to enable further progression. In the preclinical program, a range of novel chemistry methodologies were developed during the course of the discovery effort that enabled a thorough examination and definition of the HIV-1 attachment inhibitor (AI) pharmacophore. These discoveries helped to address the challenges associated with realizing a molecule with all of the properties necessary to successfully advance through development and this aspect of the program is the major focus of this retrospective. Although challenges and innovation are not unusual in drug discovery and development programs, the HIV-1 AI program is noteworthy not only because of the serial nature of the challenges encountered along the development path, but also because it resulted in a compound that remains the first and only example of a mechanistically novel class of HIV-1 inhibitor that is proving to be very beneficial for controlling virus levels in highly treatment-experienced HIV-1 infected patients.

Identification of gp120 polymorphisms in HIV-1 B subtype potentially associated with resistance to fostemsavir

OBJECTIVES

We evaluated natural resistance to the new antiretroviral fostemsavir and its potential association with other HIV-1 gp120 polymorphisms.

METHODS

A total of 1997 HIV-1 B subtype gp120 sequences from the Los Alamos HIV Database were analysed for mutation prevalence at fostemsavir resistance-associated positions and potential association with other gp120 polymorphisms. The role of each fostemsavir resistance-related position and the correlated gp120 mutations, both in protein stability and in reducing the binding affinity between antibody and/or T cell lymphocyte epitopes and the MHC molecules, was estimated.

RESULTS

The prevalence of fostemsavir resistance mutations was as follows: L116Q (0.05%), S375H/M/T (0.55%/1.35%/17.73%, the latter being far less relevant in determining resistance), M426L (7.56%), M434I (4.21%) and M475I (1.65%). Additionally, the M426R polymorphism had a prevalence of 16.32%. A significantly higher prevalence in X4 viruses versus R5 viruses was found only for S375M (0.69% versus 3.93%, P = 0.009) and S375T (16.60% versus 22.11%, P = 0.030). Some fostemsavirv resistance positions positively and significantly correlated with specific gp120 polymorphisms: S375T with I371V; S375M with L134W, I154V and I323T; M475I with K322A; and M426R with G167N, K192T and S195N. The topology of the dendrogram suggested the existence of three distinct clusters (bootstrap ≥0.98) involving these fostemsavir resistance mutations and gp120 polymorphisms. Interestingly, all clustered mutations are localized in class I/II-restricted T cell/antibody epitopes, suggesting a potential role in immune HIV escape.

CONCLUSIONS

A low prevalence of known fostemsavir resistance mutations was found in the HIV-1 B subtype. The detection of novel HIV-1 gp120 polymorphisms potentially relevant for fostemsavir resistance deserves new in-depth in vitro investigations.

Evaluating fostemsavir as a therapeutic option for patients with HIV

ABSTRACIntroduction: Despite the unquestionable success of antiretroviral therapy achieved in recent years, there are still cases of heavily treated patients who do not achieve or struggle to maintain undetectable HIV-RNA due to drug resistance. New antiretroviral options are needed to address this issue.Area covered: The authors first provide an overview of fostemsavir and its role in the treatment of HTE PLWH. Data from pre-clinical and clinical studies are reviewed and the pharmacokinetic and farmacodynamic properties are highlited. Drug-drug interactions and safety data from available clinical studies are also discussed.Expert opinion: Fostemsavir is a promising antiretroviral belonging to the class of entry inhibitors; its novel mechanism of action represents a very important innovation. Its use will be limited to the heavy-treatment-experienced patient population. This use will have to be monitored to avoid abuse and waste of a molecule that for some patients may represent a life-saving drug.

Long-term efficacy and safety of fostemsavir among subgroups of heavily treatment-experienced adults with HIV-1

OBJECTIVES

The aim of this study was to understand how demographic and treatment-related factors impact responses to fostemsavir-based regimens.

DESIGN

BRIGHTE is an ongoing phase 3 study evaluating twice-daily fostemsavir 600 mg and optimized background therapy (OBT) in heavily treatment-experienced individuals failing antiretroviral therapy with limited treatment options (Randomized Cohort 1-2 and Nonrandomized Cohort 0 fully active antiretroviral classes).

METHODS

Virologic response rates (HIV-1 RNA <40 copies/ml, Snapshot analysis) and CD4+ T-cell count increases in the Randomized Cohort were analysed by prespecified baseline characteristics (age, race, sex, region, HIV-1 RNA, CD4+ T-cell count) and viral susceptibility to OBT. Safety results were analysed by baseline characteristics for combined cohorts (post hoc).

RESULTS

In the Randomized Cohort, virologic response rates increased between Weeks 24 and 96 across most subgroups. Virologic response rates over time were most clearly associated with overall susceptibility scores for new OBT agents (OSS-new). CD4+ T-cell count increases were comparable across subgroups. Participants with baseline CD4+ T-cell counts less than 20 cells/μl had a mean increase of 240 cells/μl. In the safety population, more participants with baseline CD4+ T-cell counts less than 20 vs. at least 200 cells/μl had grade 3/4 adverse events [53/107 (50%) vs. 24/96 (25%)], serious adverse events [58/107 (54%) vs. 25/96 (26%)] and deaths [16/107 (15%) vs. 2/96 (2%)]. There were no safety differences by other subgroups.

CONCLUSION

Week 96 results for BRIGHTE demonstrate comparable rates of virologic and immunologic response (Randomized Cohort) and safety (combined cohorts) across subgroups. OSS-new is an important consideration when constructing optimized antiretroviral regimens for heavily treatment-experienced individuals with limited remaining treatment options.

Fostemsavir: The first oral attachment inhibitor for treatment of HIV-1 infection

PURPOSE

The pharmacology, pharmacokinetics, and role in therapy of fostemsavir in management of HIV-1 infection are reviewed, with an emphasis on clinical efficacy and safety data from phase 2 and phase 3 clinical trials.

SUMMARY

Fostemsavir (Rukobia, ViiV Healthcare), is a prodrug of temsavir, a novel pyridine compound with potent activity against HIV-1. Fostemsavir, the first oral attachment inhibitor, was approved and granted the breakthrough therapy designation by the Food and Drug Administration for use in combination with other antiretroviral agents for the treatment of HIV-1 infection in heavily treatment-experienced adults. As absorption of temsavir is not altered with increased gastric pH, patients may take acid suppressive agents such as famotidine during fostemsavir therapy.Temsavir is primarily metabolized through hydrolysis but also via cytochrome P-450 (CYP) oxidation; therefore, coadministration of fostemsavir with strong CYP3A inducers such as rifampin, carbamazepine, phenytoin, mitotane, enzalutamide, or St John's wort is contraindicated because it may result in significantly lower temsavir exposure, which can ultimately impair virologic response. The most common adverse reactions associated with fostemsavir use include nausea, diarrhea, headache, abdominal pain, dyspepsia, fatigue, rash, and sleep disturbance.

CONCLUSION

Fostemsavir may be an effective option for heavily treatment-experienced adults with multidrug-resistant HIV-1 infection. Fostemsavir is a particularly attractive treatment option for patients who are no longer able to achieve viral suppression with use of currently available antiretroviral therapies and who are able to adhere to a twice-daily oral regimen.

Mechanisms underlying of antiretroviral drugs in different cellular reservoirs with a focus on macrophages

Ongoing with current combinations of antiretroviral drugs for the treatment of Human Immunodeficiency Virus (HIV) infection can successfully maintain long-term suppression of HIV-1 replication in plasma. Still, none of these therapies is capable of extinguishing the virus from the long-lived cellular reservoir, including monocyte-derived macrophages (MDM), that means the principal obstacle to HIV cure. MDM are widely distributed in all tissues and organs, including central system nervous (CNS) where they represent the most frequent HIV-infected cells that means the principal obstacle to HIV cure. Current FDA-approved antiretroviral drugs target viral reverse transcriptase, protease, integrase, and entry processes (coreceptor or fusion blockade). It is desirable to continue to develop new antiretrovirals directed against alternative targets in the virus lifecycle in order to further optimize therapeutic options, overcome resistance to existing medications, and potentially contribute to the elimination of viral reservoirs.This review provides a comprehensive overview of the activity of antiretroviral drugs (classical and upcoming) in monocytes-derived macrophages (MDM). Defining the antiviral activity of these drugs in this important cellular HIV-1 reservoir provides crucial hints about their efficacy in HIV-1 infected patients.

Fostemsavir for the treatment of HIV

Introduction: For those with heavily treatment experienced (HTE) HIV-1 and virologic failure, therapeutic options are limited. A variety of barriers such as drug resistance, side effects, past intolerance, and administration inability contribute to the need for novel drug classes in this population.Areas Covered: Herein, we review the pharmacology, clinical efficacy, and safety profile of fostemsavir, a first in its class attachment inhibitor recently FDA approved for use.Expert Opinion: Fostemsavir is a well-tolerated oral medication with relatively few drug-drug interactions. Clinical trial data demonstrates virologic and notable immunologic response in conjunction with optimal background therapy in HTE persons living with HIV. Fostemsavir exhibits no cross-resistance with other ARV classes and thus is an important advancement for patients harboring drug-resistant HIV. Further study will be needed to determine outstanding clinical questions such as the role of drug resistance testing and fostemsavir use outside of the HTE population.

Recent developments in the synthesis of azaindoles from pyridine and pyrrole building blocks

The azaindole framework is ubiquitous in bioactive natural products and pharmaceuticals. This review highlights the synthetic approaches to azaindoles with advantages and limitations, mechanistic pathways and biological importance.

Azaindole therapeutic agents

Azaindole structural framework is an integral part of several biologically active natural and synthetic organic molecules; and several FDA approved drugs for various diseases. In the last decade, quite a number of literature reports appeared describing the pharmacology, biological activity and therapeutic applications of a variety of azaindole molecules. This prompted the organic and medicinal chemistry community to develop novel synthetic methods for various azaindoles and test them for a bioactivity against a variety of biological targets. Herein, we have summarized the biological activity of therapeutically advanced clinical candidates and several preclinical candidate drugs that contain azaindole structural moiety.

Fostemsavir: A Novel Attachment Inhibitor for Patients With Multidrug-Resistant HIV-1 Infection

Objective

To review the efficacy and safety of fostemsavir (FTR) for the treatment of multidrug-resistant HIV-1 infection in heavily treatment-experienced adults who are failing their current antiretroviral regimen.

Data Sources

Clinical trials and review articles were obtained through PubMed (2015 to July 2020) using the search terms fostemsavir, BMS-663068, and GSK3684934.

Study Selection and Data Extraction

All relevant articles, trials, and abstracts in the English language were included.

Data Synthesis

FTR demonstrates a novel mechanism of action, preventing virus attachment to the host CD4 receptor. FTR extended-release 600-mg tablets every 12 hours orally has proven beneficial in obtaining viral suppression for heavily treatment-experienced patients with multidrug-resistant infection refractory to other agents, as indicated in phase 3 trials. Treatment courses were evaluated to 96 weeks with significant viral load reductions noted within the first 24 weeks. Adverse events commonly reported include nausea, vomiting, diarrhea, fatigue, and headache. Serious events and fatality were not attributed to FTR and occurred because of advancement of HIV or other acute infection.

Relevance to Patient Care and Clinical Practice

FTR presents a new treatment option for patients with multidrug resistance and intolerability to other medications. The favorable adverse effect profile of FTR alongside the limited drug interaction profile makes it a viable option in a salvage regimen.

Conclusions

FTR provides an alternative agent when composing a regimen for patients with multidrug-resistant HIV-1 infection. It is generally well tolerated, with few significant interactions, and neither renal nor hepatic dose adjustments are required.

Effects of Temsavir, Active Moiety of Antiretroviral Agent Fostemsavir, on QT Interval: Results From a Phase I Study and an Exposure-Response Analysis

Fostemsavir, a prodrug of human immunodeficiency virus attachment inhibitor temsavir (TMR), is in phase III development in combination with other antiretroviral agents for the treatment of human immunodeficiency virus type I (HIV-1) infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 infection for whom it is otherwise not possible to construct a suppressive antiviral regimen due to resistance, intolerance, or safety considerations. The proarrhythmic potential of fostemsavir was studied in a thorough QT study and exposure-response modeling was performed at therapeutic and supratherapeutic concentrations of TMR. Fostemsavir 1,200 mg b.i.d. did not result in a clinically meaningful change from placebo in baseline-adjusted Fridericia-corrected QTc (ddQTcF); however, at a supratherapeutic dose of 2,400 mg b.i.d., the upper bound of the two-sided 90% confidence interval (CI) of ddQTcF was 13.2 msec, exceeding the clinically important 10 msec threshold. A linear model of ddQTcF as a function of TMR plasma concentrations described these observations. Based on simulations with this model, TMR concentrations up to 7,500 ng/mL are expected to have an upper 90% CI bound for QTcF ≤ 10 msec. This concentration is 4.2-fold higher than the geometric mean TMR peak plasma concentration (Cmax ) of 1,770 ng/mL in heavily treatment-experienced HIV-1 infected patients administered fostemsavir 600 mg b.i.d. in the phase III BRIGHTE study (NCT02362503).

Long-Acting BMS-378806 Analogues Stabilize the State-1 Conformation of the Human Immunodeficiency Virus Type 1 Envelope Glycoproteins

During human immunodeficiency virus type 1 (HIV-1) entry into cells, the viral envelope glycoprotein (Env) trimer [(gp120/gp41)₃] binds the receptors CD4 and CCR5 and fuses the viral and cell membranes. CD4 binding changes Env from a pretriggered (state-1) conformation to more open downstream conformations. BMS-378806 (here called BMS-806) blocks CD4-induced conformational changes in Env important for entry and is hypothesized to stabilize a state-1-like Env conformation, a key vaccine target. Here, we evaluated the effects of BMS-806 on the conformation of Env on the surface of cells and virus-like particles. BMS-806 strengthened the labile, noncovalent interaction of gp120 with the Env trimer, enhanced or maintained the binding of most broadly neutralizing antibodies, and decreased the binding of poorly neutralizing antibodies. Thus, in the presence of BMS-806, the cleaved Env on the surface of cells and virus-like particles exhibits an antigenic profile consistent with a state-1 conformation. We designed novel BMS-806 analogues that stabilized the Env conformation for several weeks after a single application. These long-acting BMS-806 analogues may facilitate enrichment of the metastable state-1 Env conformation for structural characterization and presentation to the immune system.IMPORTANCE The envelope glycoprotein (Env) spike on the surface of human immunodeficiency virus type 1 (HIV-1) mediates the entry of the virus into host cells and is also the target for antibodies. During virus entry, Env needs to change shape. Env flexibility also contributes to the ability of HIV-1 to evade the host immune response; many shapes of Env raise antibodies that cannot recognize the functional Env and therefore do not block virus infection. We found that an HIV-1 entry inhibitor, BMS-806, stabilizes the functional shape of Env. We developed new variants of BMS-806 that stabilize Env in its natural state for long periods of time. The availability of such long-acting stabilizers of Env shape will allow the natural Env conformation to be characterized and tested for efficacy as a vaccine.

Fostemsavir in Adults with Multidrug-Resistant HIV-1 Infection

BACKGROUND

Among some patients with human immunodeficiency virus type 1 (HIV-1) infection who have undergone multiple antiretroviral therapies and have limited options for treatment, new classes of antiretroviral drugs with novel mechanisms of action are needed. Fostemsavir is the prodrug of temsavir, a first-in-class investigational HIV-1 attachment inhibitor.

METHODS

In this ongoing phase 3 trial in 23 countries, we enrolled patients with multidrug-resistant HIV-1 infection in two cohorts, according to their remaining treatment options. In the first cohort, we assigned (in a 3:1 ratio) patients who had the option of using at least one fully active, approved antiretroviral drug in at least one but no more than two antiretroviral classes to add either fostemsavir (at a dose of 600 mg twice daily) or placebo to their failing regimen for 8 days, followed by open-label fostemsavir plus optimized background therapy (randomized cohort). In the second cohort, patients who had no remaining antiretroviral options were started on open-label fostemsavir plus optimized background therapy on day 1 (nonrandomized cohort). The primary end point was the mean change in the HIV-1 RNA level from day 1 through day 8 in the randomized cohort.

RESULTS

A total of 371 patients were treated, including 272 in the randomized cohort and 99 in the nonrandomized cohort. At day 8, the mean decrease in the HIV-1 RNA level was 0.79 log₁₀ copies per milliliter in the fostemsavir group and 0.17 log₁₀ copies in the placebo group (P<0.001). At week 48, a virologic response (HIV-1 RNA level, <40 copies per milliliter) had occurred in 54% of the patients in the randomized cohort and in 38% of those in the nonrandomized cohort; the mean increase in the CD4+ T-cell count was 139 cells per cubic millimeter and 64 cells per cubic millimeter, respectively. Adverse events led to the discontinuation of fostemsavir in 7% of the patients. In the randomized cohort, glycoprotein 120 (gp120) substitutions were found in 20 of 47 patients (43%) with virologic failure.

CONCLUSIONS

In patients with multidrug-resistant HIV-1 infection with limited therapy options, those who received fostemsavir had a significantly greater decrease in the HIV-1 RNA level than those who received placebo during the first 8 days. Efficacy was sustained through 48 weeks. (Funded by Bristol-Myers Squibb and GSK/ViiV Healthcare; BRIGHTE ClinicalTrials.gov number, NCT02362503.).

Gp120 substitutions at positions associated with resistance to fostemsavir in treatment-naive HIV-1-positive individuals

Objectives

Fostemsavir, a novel attachment inhibitor targeting the HIV-1 gp120, has demonstrated wide in vitro activity. However, the high rate of HIV gp120 substitutions could jeopardize its efficacy. We investigated envelope (env) substitutions at positions associated with resistance to fostemsavir in patients with a new HIV-1 diagnosis according to HIV subtype and tropism.

Methods

Gp120 sequences from 409 subjects were retrospectively analysed and the presence of the L116P, A204D, S375H/M/T, M426L, M434I and M475I mutations was evaluated. Other amino acid changes at the same positions were also recorded. The variability at each amino acid position was evaluated using Shannon entropy.

Results

The frequency of mutations was: S375T (13.2%); M426L (6.8%); M434I (2.9%); M475I (2.7%); S375H (1.0%)/M (0.8%) and L116P (0.31%). Statistically significant differences were found at positions 375 (R5/non-R5 strains and B/non-B subtypes) and 426 (B/non-B subtypes); post hoc analysis revealed that significance for position 375 was steered by S375T while for position 426 significance was governed by unusual substitutions, in particular M426R (B/non-B, P &lt; 0.00001). The variability of env constant domains appeared to be more relevant in the non-B virus population.

Conclusions

In conclusion, gp120 substitutions were detected in different subtypes and in both R5 and non-R5 variants. Despite the great variability of gp120, the frequency of mutations was low overall and the predominant substitution was S375T, the role of which in reducing fostemsavir efficacy is less substantial.

Newly Developed Prodrugs and Prodrugs in Development; an Insight of the Recent Years

BACKGROUND

The design and development of prodrugs is the most common and effective strategy to overcome pharmacokinetic and pharmacodynamic drawbacks of active drugs. A respected number of prodrugs have been reached the drugs market throughout history and the recent years have witnessed a significant increase in the use of prodrugs as a replacement of their parent drugs for an efficient treatment of various ailment.

METHODS

A Scan conducted to find recent approved prodrugs and prodrugs in development.

RESULTS

Selected prodrugs were reported and categorized in accordance to their target systems.

CONCLUSIONS

the prodrug approach has shown many successes and still remains a viable and effective approach to deliver new active agents. This conclusion is supported by the recent approved prodrugs and the scan of clinical trials conducted between 2013-2018.

IgG Fc-binding motif-conjugated HIV-1 fusion inhibitor exhibits improved potency and in vivo half-life: Potential application in combination with broad neutralizing antibodies

The clinical application of conventional peptide drugs, such as the HIV-1 fusion inhibitor enfuvirtide, is limited by their short half-life in vivo. To overcome this limitation, we developed a new strategy to extend the in vivo half-life of a short HIV-1 fusion inhibitory peptide, CP24, by fusing it with the human IgG Fc-binding peptide (IBP). The newly engineered peptide IBP-CP24 exhibited potent and broad anti-HIV-1 activity with IC50 values ranging from 0.2 to 173.7 nM for inhibiting a broad spectrum of HIV-1 strains with different subtypes and tropisms, including those resistant to enfuvirtide. Most importantly, its half-life in the plasma of rhesus monkeys was 46.1 h, about 26- and 14-fold longer than that of CP24 (t1/2 = 1.7 h) and enfuvirtide (t1/2 = 3 h), respectively. IBP-CP24 intravenously administered in rhesus monkeys could not induce significant IBP-CP24-specific antibody response and it showed no obvious in vitro or in vivo toxicity. In the prophylactic study, humanized mice pretreated with IBP-CP24 were protected from HIV-1 infection. As a therapeutic treatment, coadministration of IBP-CP24 and normal human IgG to humanized mice with chronic HIV-1 infection resulted in a significant decrease of plasma viremia. Combining IBP-CP24 with a broad neutralizing antibody (bNAb) targeting CD4-binding site (CD4bs) in gp120 or a membrane proximal external region (MPER) in gp41 exhibited synergistic effect, resulting in significant dose-reduction of the bNAb and IBP-CP24. These results suggest that IBP-CP24 has the potential to be further developed as a new HIV-1 fusion inhibitor-based, long-acting anti-HIV drug that can be used alone or in combination with a bNAb for treatment and prevention of HIV-1 infection.

The Discovery and Development of Oxalamide and Pyrrole Small Molecule Inhibitors of gp120 and HIV Entry - A Review

Human immunodeficiency virus type-1 (HIV-1) is the causative agent responsible for the acquired immunodeficiency syndrome (AIDS) pandemic. More than 60 million infections and 25 million deaths have occurred since AIDS was first identified in the early 1980s. Advances in available therapeutics, in particular combination antiretroviral therapy, have significantly improved the treatment of HIV infection and have facilitated the shift from high mortality and morbidity to that of a manageable chronic disease. Unfortunately, none of the currently available drugs are curative of HIV. To deal with the rapid emergence of drug resistance, off-target effects, and the overall difficulty of eradicating the virus, an urgent need exists to develop new drugs, especially against targets critically important for the HIV-1 life cycle. Viral entry, which involves the interaction of the surface envelope glycoprotein, gp120, with the cellular receptor, CD4, is the first step of HIV-1 infection. Gp120 has been validated as an attractive target for anti-HIV-1 drug design or novel HIV detection tools. Several small molecule gp120 antagonists are currently under investigation as potential entry inhibitors. Pyrrole, piperazine, triazole, pyrazolinone, oxalamide, and piperidine derivatives, among others, have been investigated as gp120 antagonist candidates. Herein, we discuss the current state of research with respect to the design, synthesis and biological evaluation of oxalamide derivatives and five-membered heterocycles, namely, the pyrrole-containing small molecule as inhibitors of gp120 and HIV entry.

Impact of natural polymorphisms of HIV-1 non-group M on genotypic susceptibility to the attachment inhibitor fostemsavir

Background

Fostemsavir belongs to the new class of attachment inhibitors (AIs); it inhibits the entry of HIV into CD4+ T-lymphocytes by blocking conformational changes in gp120. This is a promising AI, but previous phenotypic data showed that genetically divergent HIV-1 group O could present natural resistance to this drug. These data were obtained from only two strains, which are not representative of the high intra-group genetic diversity. Moreover, no data are available concerning the other divergent HIV-1 groups (N and P).

Objectives

To further investigate the natural genotypic susceptibility of HIV-1 groups O, N and P (HIV-1 non-M) to fostemsavir, using a large set of sequences.

Methods

The frequency of eight substitutions associated with decreased susceptibility to fostemsavir (L116P, A204D, S375M/H, M426L, M434I, M475I and V506M), was investigated in 111 gp120 sequences from groups O (n = 100), N (n = 9) and P (n = 2).

Results

All HIV-1 group N sequences harboured the three substitutions S375M, M426L and M434I, whereas only 1% and 10% of HIV-1 group O sequences harboured the S375H + M426L and S375H + M434I patterns, respectively. The main genetic profile of HIV-1 groups P and O combined S375H with two atypical substitutions (M426S and M434L). Five group O sequences did not display any of the eight substitutions, but had atypical residues with unknown impact.

Conclusions

The genetic polymorphisms in the gp120 of HIV-1 non-M viruses support the hypothesis that these viruses could largely be resistant to inhibition by fostemsavir. Only 5% of group O strains could display full genetic susceptibility. Extensive phenotypic studies are now required.

Management of Virologic Failure and HIV Drug Resistance

Approximately 20% of people with HIV in the United States prescribed antiretroviral therapy are not virally suppressed. Thus, optimal management of virologic failure has a critical role in the ability to improve viral suppression rates to improve long-term health outcomes for those infected and to achieve epidemic control. This article discusses the causes of virologic failure, the use of resistance testing to guide management after failure, interpretation and relevance of HIV drug resistance patterns, considerations for selection of second-line and salvage therapies, and management of virologic failure in special populations.

Fostemsavir: a new CD4 attachment inhibitor

PURPOSE OF REVIEW

Even in the era of modern HAART, antiretroviral (ARV) failure and emergence of drug resistance is still a problem worldwide. New classes with different mechanisms of action are needed to overcome this challenge. After the integrase inhibitors were launched, more than a decade ago, no new classes were added to the ARV armamentarium.

RECENT FINDINGS

Fostemsavir (FTR) is an attachment inhibitor, active regardless of viral tropism, without cross-resistance to any of the existing ARV compounds. A phase 3 study showed a reduction in plasma viral RNA of 1.21-1.73 log10 copies/ml from baseline after 8 days of functional monotherapy; at 48 weeks, up to 82% of patients treated with FTR and an optimized background ARV regimen achieved virological suppression below 50 copies/ml.

SUMMARY

FTR is an investigational HIV drug with a novel mechanism of action that demonstrates virologic activity in HIV-infected treatment-experienced individuals.

Singularities of nevirapine metabolism: from sex-dependent differences to idiosyncratic toxicity

Nevirapine (NVP) is a first-generation non-nucleoside reverse transcriptase inhibitor widely used for the treatment and prophylaxis of human immunodeficiency virus infection. The drug is taken throughout the patient's life and, due to the availability of an extended-release formulation, it is administered once daily. This antiretroviral is one of the scarce examples of drugs with prescription criteria based on sex, in order to prevent adverse reactions. The therapy with NVP has been associated with potentially life-threatening liver and idiosyncratic skin toxicity. Multiple evidence has emerged regarding the formation of electrophilic NVP metabolites as crucial for adverse idiosyncratic reactions. The formation of reactive metabolites that yield covalent adducts with proteins has been demonstrated in patients under NVP-based treatment. Interestingly, several pharmacogenetic- and sex-related factors associated with NVP toxicity can be mechanistically explained by an imbalance toward increased formation of NVP-derived reactive metabolites and/or impaired detoxification capability. Moreover, the haptenation of self-proteins by these reactive species provides a plausible link between NVP bioactivation and immunotoxicity, further supporting the relevance of this toxicokinetics hypothesis. In the current paper, we review the existing knowledge and recent developments on NVP metabolism and their relation to NVP toxicity.

Viral Drug Resistance Through 48 Weeks, in a Phase 2b, Randomized, Controlled Trial of the HIV-1 Attachment Inhibitor Prodrug, Fostemsavir

Supplemental Digital Content is Available in the Text.

Background:

Fostemsavir is a prodrug of temsavir, an attachment inhibitor that binds to HIV-1 gp120, blocking viral attachment to host CD4⁺ T-cells. The phase 2b trial AI438011 investigated the safety, efficacy, and dose–response of fostemsavir vs ritonavir-boosted atazanavir (ATV/r) in treatment-experienced, HIV-1–infected subjects.

Methods:

Two hundred fifty-one treatment-experienced subjects with baseline (BL) susceptibility to study drugs [temsavir half-maximal inhibitory concentration (IC₅₀) <100 nM, PhenoSense Entry assay] received fostemsavir or ATV/r, each with tenofovir disoproxil fumarate + raltegravir. Subjects meeting resistance-testing criteria were assessed for emergent viral drug resistance. Changes in temsavir IC₅₀ from BL was given a conservative technical cutoff (>3-fold increase).

Results:

66/200 fostemsavir and 14/51 ATV/r subjects had resistance testing performed; 44/66 and 9/14 were successfully tested using the PhenoSense GT assay. No subjects had emergent tenofovir disoproxil fumarate or ATV resistance. Six fostemsavir-treated subjects developed emergent raltegravir resistance. 29/66 fostemsavir-treated subjects had an evaluable phenotype using PhenoSense Entry (which tests for viral susceptibility to temsavir) and 13/29 exhibited >3-fold increase in temsavir IC₅₀ from BL. gp120 population sequencing was successful in 11/13 subjects and 7 had emergent substitutions in gp120 associated with reduced temsavir susceptibility (S375, M426, or M434). However, 5/13 fostemsavir-treated subjects achieved subsequent suppression to <50 copies/mL before the week 48 database lock, regardless of key gp120 substitutions.

Conclusions:

Response rates remained similar across study arms regardless of BL nucleoside reverse transcriptase inhibitor, nonnucleoside reverse transcriptase inhibitor, and protease inhibitor resistance-associated mutations. Emergent changes in viral susceptibility occurred more frequently with fostemsavir compared with ATV/r. However, the full impact of temsavir IC₅₀ changes and emergent HIV-1 gp120 substitutions, and thus appropriate clinical cutoffs, requires further study. Fostemsavir is being evaluated in a phase 3 trial in heavily treatment-experienced subjects.

Neutralization Synergy between HIV-1 Attachment Inhibitor Fostemsavir and Anti-CD4 Binding Site Broadly Neutralizing Antibodies against HIV

Attachment inhibitor (AI) BMS-626529 (fostemsavir) represents a novel class of antiretrovirals which target human immunodeficiency virus type 1 (HIV-1) gp120 and block CD4-induced conformational changes required for viral entry. It is now in phase III clinical trials and is expected to be approved by the U.S. Food and Drug Administration (FDA) in the near future. Although fostemsavir is very potent against HIV in vitro and in vivo, a number of resistant mutants have already been identified. Broadly neutralizing HIV antibodies (bNAbs) can potently inhibit a wide range of HIV-1 strains by binding to viral Env and are very promising candidates for HIV-1 prevention and therapy. Since both target viral Env to block viral entry, we decided to investigate the relationship between these two inhibitors. Our data show that Env mutants resistant to BMS-626529 retained susceptibility to bNAbs. A single treatment of bNAb NIH45-46^G54W completely inhibited the replication of these escape mutants. Remarkable synergy was observed between BMS-626529 and CD4 binding site (CD4bs)-targeting bNAbs in neutralizing HIV-1 strains at low concentrations. This synergistic effect was enhanced against virus harboring mutations conferring resistance to BMS-626529. The mechanistic basis of the observed synergy is likely enhanced inhibition of CD4 binding to the HIV-1 Env trimer by the combination of BMS-626529 and CD4bs-targeting bNAbs. This work highlights the potential for positive interplay between small- and large-molecule therapeutics against HIV entry, which may prove useful as these agents enter clinical use.IMPORTANCE As the worldwide HIV pandemic continues, there is a continued need for novel drugs and therapies. A new class of drug, the attachment inhibitors, will soon be approved for the treatment of HIV. Broadly neutralizing antibodies are also promising candidates for HIV prevention and therapy. We investigated how this drug might work with these exciting antibodies that are very potent in blocking HIV infection of cells. These antibodies worked against virus known to be resistant to the new drug. In addition, a specific type of antibody worked really well with the new drug in blocking virus infection of cells. This work has implications for both the new drug and the antibodies that are poised to be used against HIV.

Investigational drugs in HIV: Pros and cons of entry and fusion inhibitors (Review)

Despite the profound changes and improvements reached in the field of HIV treatment, tolerability and adherence to highly active antiretroviral therapy remains a challenge. Furthermore, multi-experienced patients could take advantage of drugs with different mechanisms of action to combat the spread of resistance to actual therapy. For these reasons identification of new HIV drugs is crucial. Among all the molecules that at present are under investigation, entry and fusion inhibitors pose an interesting class owing to their peculiar characteristics, including prevention of entry of the virus into the human cells. In this study, we reviewed articles, clinical trials, and conference communications about all the drugs under investigation belonging to the class of entry and fusion inhibitors that are at least in phase I clinical trials.

Virtual Screening, Biological Evaluation, and 3D-QSAR Studies of New HIV-1 Entry Inhibitors That Function via the CD4 Primary Receptor

Human immunodeficiency virus type 1 (HIV-1) is responsible for the majority of HIV infections worldwide, and we still lack a cure for this infection. Blocking the interaction of HIV-1 and its primary receptor CD4 is one strategy for identifying new anti-HIV-1 entry inhibitors. Here we report the discovery of a novel ligand that can inhibit HIV-1 entry and infection via CD4. Biological and computational analyses of this inhibitor and its analogs, using bioactivity evaluation, Rule of Five (RO5), comparative molecular field analysis (CoMFA)/comparative molecular similarity index analysis (CoMSIA) models, and three-dimensional quantitative structure-activity relationship (3D-QSAR), singled out compound 3 as a promising lead molecule for the further development of therapeutics targeting HIV-1 entry. Our study demonstrates an effective approach for employing structure-based, rational drug design techniques to identify novel antiviral compounds with interesting biological activities.

Phase 3 Study of Ibalizumab for Multidrug-Resistant HIV-1

BACKGROUND

Ibalizumab, a humanized IgG4 monoclonal antibody, blocks the entry of human immunodeficiency virus type 1 (HIV-1) by noncompetitive binding to CD4.

METHODS

In this single-group, open-label, phase 3 study, we enrolled 40 adults with multidrug-resistant (MDR) HIV-1 infection in whom multiple antiretroviral therapies had failed. All the patients had a viral load of more than 1000 copies of HIV-1 RNA per milliliter. After a 7-day control period in which patients continued to receive their current therapy, a loading dose of 2000 mg of ibalizumab was infused; the viral load was quantified 7 days later. Through week 25 of the study, patients received 800 mg of ibalizumab every 14 days, combined with an individually optimized background regimen including at least one fully active agent. The primary end point was the proportion of patients with a decrease in viral load of at least 0.5 log₁₀ copies per milliliter from baseline (day 7) to day 14.

RESULTS

A total of 31 patients completed the study. The mean baseline viral load was 4.5 log₁₀ copies per milliliter, and the mean CD4 count was 150 per microliter. Of the 40 patients in the intention-to-treat population, 33 (83%) had a decrease in viral load of at least 0.5 log₁₀ copies per milliliter from baseline (P<0.001 for the comparison with the control period). The mean viral-load decrease was 1.1 log₁₀ copies per milliliter. During the control period, 1 patient, who received the optimized background regimen prematurely, had a decrease in viral load of 0.5 log₁₀ copies per milliliter. At week 25, patients who had received ibalizumab plus an optimized background regimen had a mean decrease of 1.6 log₁₀ copies per milliliter from baseline; 43% of the patients had a viral load of less than 50 copies per milliliter, and 50% had a viral load of less than 200 copies per milliliter. Among 10 patients who had virologic failure or rebound, in vitro testing identified 9 who had a lower degree of susceptibility to ibalizumab than at baseline. The most common adverse event was diarrhea (in 20% of patients). Four patients died from causes related to underlying illnesses; 1 had a serious adverse event (the immune reconstitution inflammatory syndrome) that was deemed to be related to ibalizumab therapy.

CONCLUSIONS

In patients with MDR HIV-1 infection who had advanced disease and limited treatment options, ibalizumab had significant antiviral activity during a 25-week study. Evidence of the emergence of diminished ibalizumab susceptibility was observed in vitro in patients who had virologic failure. (Funded by the Orphan Products Clinical Trials Grants Program of the Food and Drug Administration and TaiMed Biologics; TMB-301 ClinicalTrials.gov number, NCT02475629 .).

Discovery of the Human Immunodeficiency Virus Type 1 (HIV-1) Attachment Inhibitor Temsavir and Its Phosphonooxymethyl Prodrug Fostemsavir

The optimization of the 4-methoxy-6-azaindole series of HIV-1 attachment inhibitors (AIs) that originated with 1 to deliver temsavir (3, BMS-626529) is described. The most beneficial increases in potency and pharmacokinetic (PK) properties were attained by incorporating N-linked, sp²-hybridized heteroaryl rings at the 7-position of the heterocyclic nucleus. Compounds that adhered to a coplanarity model afforded targeted antiviral potency, leading to the identification of 3 with characteristics that provided for targeted exposure and PK properties in three preclinical species. However, the physical properties of 3 limited plasma exposure at higher doses, both in preclinical studies and in clinical trials as the result of dissolution- and/or solubility-limited absorption, a deficiency addressed by the preparation of the phosphonooxymethyl prodrug 4 (BMS-663068, fostemsavir). An extended-release formulation of 4 is currently in phase III clinical trials where it has shown promise as part of a drug combination therapy in highly treatment-experienced HIV-1 infected patients.

Inhibitors of HIV-1 Attachment: The Discovery and Development of Temsavir and its Prodrug Fostemsavir

Human immunodeficiency virus-1 (HIV-1) infection currently requires lifelong therapy with drugs that are used in combination to control viremia. The indole-3-glyoxamide 6 was discovered as an inhibitor of HIV-1 infectivity using a phenotypic screen and derivatives of this compound were found to interfere with the HIV-1 entry process by stabilizing a conformation of the virus gp120 protein not recognized by the host cell CD4 receptor. An extensive optimization program led to the identification of temsavir (31), which exhibited an improved antiviral and pharmacokinetic profile compared to 6 and was explored in phase 3 clinical trials as the phosphonooxymethyl derivative fostemsavir (35), a prodrug designed to address dissolution- and solubility-limited absorption issues. In this drug annotation, we summarize the structure-activity and structure-liability studies leading to the discovery of 31 and the clinical studies conducted with 35 that entailed the development of an extended release formulation suitable for phase 3 clinical trials.

Advanced Prodrug Strategies in Nucleoside and Non-Nucleoside Antiviral Agents: A Review of the Recent Five Years

Background: Poor pharmacokinetic profiles and resistance are the main two drawbacks from which currently used antiviral agents suffer, thus make them excellent targets for research, especially in the presence of viral pandemics such as HIV and hepatitis C. Methods: The strategies employed in the studies covered in this review were sorted by the type of drug synthesized into ester prodrugs, targeted delivery prodrugs, macromolecular prodrugs, other nucleoside conjugates, and non-nucleoside drugs. Results: Utilizing the ester prodrug approach a novel isopropyl ester prodrug was found to be potent HIV integrase inhibitor. Further, employing the targeted delivery prodrug zanamivir and valine ester prodrug was made and shown a sole delivery of zanamivir. Additionally, VivaGel, a dendrimer macromolecular prodrug, was found to be very efficient and is now undergoing clinical trials. Conclusions: Of all the strategies employed (ester, targeted delivery, macromolecular, protides and nucleoside analogues, and non-nucleoside analogues prodrugs), the most promising are nucleoside analogues and macromolecular prodrugs. The macromolecular prodrug VivaGel works by two mechanisms: envelope mediated and receptor mediated disruption. Nucleotide analogues have witnessed productive era in the recent past few years. The era of non-interferon based treatment of hepatitis (through direct inhibitors of NS5A) has dawned.

Crystal structures of trimeric HIV envelope with entry inhibitors BMS-378806 and BMS-626529

The HIV-1 envelope (Env) spike is a conformational machine that transitions between prefusion (closed, CD4- and CCR5-bound) and postfusion states to facilitate HIV-1 entry into cells. Although the prefusion closed conformation is a potential target for inhibition, development of small-molecule leads has been stymied by difficulties in obtaining structural information. Here, we report crystal structures at 3.8-Å resolution of an HIV-1-Env trimer with BMS-378806 and a derivative BMS-626529 for which a prodrug version is currently in Phase III clinical trials. Both lead candidates recognized an induced binding pocket that was mostly excluded from solvent and comprised of Env elements from a conserved helix and the β20-21 hairpin. In both structures, the β20-21 region assumed a conformation distinct from prefusion-closed and CD4-bound states. Together with biophysical and antigenicity characterizations, the structures illuminate the allosteric and competitive mechanisms by which these small-molecule leads inhibit CD4-induced structural changes in Env.

Synthesis, Antiviral Potency, in Vitro ADMET, and X-ray Structure of Potent CD4 Mimics as Entry Inhibitors That Target the Phe43 Cavity of HIV-1 gp120

In our attempt to optimize the lead HIV-1 entry antagonist, NBD-11021, we present in this study the rational design and synthesis of 60 new analogues and determination of their antiviral activity in a single-cycle and a multicycle infection assay to derive a comprehensive structure-activity relationship (SAR). Two of these compounds, NBD-14088 and NBD-14107, showed significant improvement in antiviral activity compared to the lead entry antagonist in a single-cycle assay against a large panel of Env-pseudotyped viruses. The X-ray structure of a similar compound, NBD-14010, confirmed the binding mode of the newly designed compounds. The in vitro ADMET profiles of these compounds are comparable to that of the most potent attachment inhibitor BMS-626529, a prodrug of which is currently undergoing phase III clinical trials. The systematic study presented here is expected to pave the way for improving the potency, toxicity, and ADMET profile of this series of compounds with the potential to be moved to the early preclinical development.

Significant publications on infectious diseases pharmacotherapy in 2015

PURPOSE

The most important articles on infectious diseases (ID) pharmacotherapy published in the peer-reviewed literature in 2015, as nominated and selected by panels of pharmacists and others with ID expertise, are summarized.

SUMMARY

Members of the Houston Infectious Diseases Network were asked to nominate articles published in prominent peer-reviewed journals in 2015 that were thought to have a major impact in the field of ID pharmacotherapy. A list of 55 nominated articles on general ID-related topics and 10 articles specifically related to human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS) was compiled. In a national online survey, members of the Society of Infectious Diseases Pharmacists (SIDP) were asked to select from the list 10 general ID articles believed to have made a significant contribution to the field of ID pharmacotherapy and 1 article contributing to HIV/AIDS pharmacotherapy. Of the 361 SIDP members surveyed, 153 (42%) and 76 (21%) participated in the selection of general ID-related articles and HIV/AIDS-related articles, respectively. The 11 highest-ranked publications (10 general ID-related articles and 1 HIV/AIDS-related article) are summarized here.

CONCLUSION

With the growing number of significant ID-related publications each year, it can be challenging to stay current with the literature. This review of important ID pharmacotherapy publications in 2015 may be helpful in identifying key articles and lessening this burden.

Role of phenotypic investigation in the era of routine genotypic HIV-1 drug resistance testing

The emergence of drug resistance can seriously compromise HIV type-1 therapy and decrease therapeutic options. Resistance testing is highly recommended to guide treatment decisions and drug activity can be accurately predicted in the clinical setting through genotypic assays. While phenotypic systems are not suitable for monitoring drug resistance in routine laboratory practice, genotyping can misclassify unusual or complex mutational patterns, particularly with recently approved antivirals. In addition, phenotypic assays remain fundamental for characterizing candidate antiretroviral compounds. This review aims to discuss how phenotypic assays contributed to and still play a role in understanding the mechanisms of resistance of both licensed and investigational HIV type-1 inhibitors.

Model-Based Phase 3 Dose Selection for HIV-1 Attachment Inhibitor Prodrug BMS-663068 in HIV-1-Infected Patients: Population Pharmacokinetics/Pharmacodynamics of the Active Moiety, BMS-626529

BMS-663068 is an oral prodrug of the HIV-1 attachment inhibitor BMS-626529, which prevents viral attachment to host CD4(+) T cells by binding to HIV-1 gp120. To guide dose selection for the phase 3 program, pharmacokinetic/pharmacodynamic modeling was performed using data from two phase 2 studies with HIV-1-infected subjects (n = 244). BMS-626529 population pharmacokinetics were described by a two-compartment model with first-order elimination from the central compartment, zero-order release of prodrug from the extended-release formulation into a hypothetical absorption compartment, and first-order absorption into the central compartment. The covariates of BMS-663068 formulation type, lean body mass, baseline CD8(+) T-cell percentage, and ritonavir coadministration were found to be significant contributors to intersubject variability. Exposure-response analyses showed a relationship between the loge-transformed concentration at the end of a dosing interval (Ctau) normalized for the protein binding-adjusted BMS-626529 half-maximal (50%) inhibitory concentration (PBAIC50) and the change in the HIV-1 RNA level from the baseline level after 7 days of BMS-663068 monotherapy. The probability of achieving a decline in HIV-1 RNA level of >0.5 or >1.0 log10 copies/ml as a function of the loge-transformed PBAIC50-adjusted Ctau after 7 days of monotherapy was 99 to 100% and 57 to 73%, respectively, for proposed BMS-663068 doses of 400 mg twice daily (BID), 600 mg BID (not studied in the phase 2b study), 800 mg BID, 600 mg once daily (QD), and 1,200 mg QD. On the basis of a slight advantage in efficacy of BID dosing over QD dosing, similar responses for the 600- and 800-mg BID doses, and prior clinical observations, BMS-663068 at 600 mg BID was predicted to have the optimal benefit-risk profile and selected for further clinical investigation. (The phase 2a proof-of-concept study AI438006 and the phase 2b study AI438011 are registered at ClinicalTrials.gov under numbers NCT01009814 and NCT01384734, respectively.).

Aloperine and Its Derivatives as a New Class of HIV-1 Entry Inhibitors

A quinolizidine-type alkaloid aloperine was found to inhibit HIV-1 infection by blocking HIV-1 entry. Aloperine inhibited HIV-1 envelope-mediated cell-cell fusion at low micromolar concentrations. To further improve the antiviral potency, more than 30 aloperine derivatives with a variety of N12-substitutions were synthesized. Among them, 12d with an N-(1-butyl)-4-trifluoromethoxy-benzamide side chain showed the most potent anti-HIV-1 activity with EC50 at 0.69 μM. Aloperine derivatives inhibited both X4 and R5 HIV-1 Env-mediated cell-cell fusions. In addition, both BMS-806, a compound representing a class of HIV-1 gp120-targeting small molecules in clinical trials, and resistant and sensitive HIV-1 Env-mediated cell-cell fusions were equally sensitive to aloperine derivatives. These results suggest that aloperine and its derivatives are a new class of anti-HIV-1 entry inhibitors.