Ibalizumab in Multidrug-Resistant HIV - Accepting Uncertainty

Human Immunodeficiency Virus Persistence in the Spleen: Opportunities for Pharmacologic Intervention

The persistence of HIV in the spleen, despite combination antiretroviral therapy, is not well understood. Sustained immune dysregulation and delayed immune recovery, in addition to immune cell exhaustion, may contribute to persistence of infection in the spleen. Eliminating HIV from this secondary lymphoid organ will require a thorough understanding of antiretroviral (ARV) pharmacology in the spleen, which has been minimally investigated. Low ARV exposure within the spleen may hinder the achievement of a functional or sterilizing cure if cells are not protected from HIV infection. In this study, we provide an overview of the anatomy and physiology of the spleen, review the evidence of the spleen as a site for persistence of HIV, discuss the consequences of persistence of HIV in the spleen, address challenges to eradicating HIV in the spleen, and examine opportunities for future curative efforts.

Double Arylation of the Indole Side Chain of Tri- and Tetrapodal Tryptophan Derivatives Renders Highly Potent HIV-1 and EV-A71 Entry Inhibitors†

We have recently described a new generation of potent human immunodeficiency virus (HIV) and EV-A71 entry inhibitors. The prototypes contain three or four tryptophan (Trp) residues bearing an isophthalic acid moiety at the C2 position of each side-chain indole ring. This work is now extended by both shifting the position of the isophthalic acid to C7 and synthesizing doubly arylated C2/C7 derivatives. The most potent derivative (50% effective concentration (EC₅₀) HIV-1, 6 nM; EC₅₀ EV-A71, 40 nM), 33 (AL-518), is a C2/C7 doubly arylated tetrapodal compound. Its superior anti-HIV potency with respect to the previous C2-arylated prototype is in consonance with its higher affinity for the viral gp120. 33 (AL-518) showed comparable antiviral activities against X4 and R5 HIV-1 strains and seems to interact with the tip and base of the gp120 V3 loop. Taken together, these findings support the interest in 33 (AL-518) as a useful new prototype for anti-HIV/EV71 drug development.

HIV in pregnancy: Mother-to-child transmission, pharmacotherapy, and toxicity

An estimated 1.3 million pregnant women were living with HIV in 2018. HIV infection is associated with adverse pregnancy outcomes and all HIV-positive pregnant women, regardless of their clinical stage, should receive a combination of antiretroviral drugs to suppress maternal viral load and prevent vertical fetal infection. Although antiretroviral treatment in pregnant women has undoubtedly minimized mother-to-child transmission of HIV, several uncertainties remain. For example, while pregnancy is accompanied by changes in pharmacokinetic parameters, relevant data from clinical studies are lacking. Similarly, long-term adverse effects of exposure to antiretrovirals on fetuses have not been studied in detail. Here, we review current knowledge on HIV effects on the placenta and developing fetus, recommended antiretroviral regimens, and pharmacokinetic considerations with particular focus on placental transport. We also discuss recent advances in antiretroviral research and potential effects of antiretroviral treatment on placental/fetal development and programming.

Generation of HIV-resistant cells with a single-domain antibody: implications for HIV-1 gene therapy

The cure or functional cure of the "Berlin patient" and "London patient" indicates that infusion of HIV-resistant cells could be a viable treatment strategy. Very recently, we genetically linked a short-peptide fusion inhibitor with a glycosylphosphatidylinositol (GPI) attachment signal, rendering modified cells fully resistant to HIV infection. In this study, GPI-anchored m36.4, a single-domain antibody (nanobody) targeting the coreceptor-binding site of gp120, was constructed with a lentiviral vector. We verified that m36.4 was efficiently expressed on the plasma membrane of transduced TZM-bl cells and targeted lipid raft sites without affecting the expression of HIV receptors (CD4, CCR5, and CXCR4). Significantly, TZM-bl cells expressing GPI-m36.4 were highly resistant to infection with divergent HIV-1 subtypes and potently blocked HIV-1 envelope-mediated cell-cell fusion and cell-cell viral transmission. Furthermore, we showed that GPI-m36.4-modified human CEMss-CCR5 cells were nonpermissive to both CCR5- and CXCR4-tropic HIV-1 isolates and displayed a strong survival advantage over unmodified cells. It was found that GPI-m36.4 could also impair HIV-1 Env processing and viral infectivity in transduced cells, underlying a multifaceted mechanism of antiviral action. In conclusion, our studies characterize m36.4 as a powerful nanobody that can generate HIV-resistant cells, offering a novel gene therapy approach that can be used alone or in combination.

Ibalizumab: A Review in Multidrug-Resistant HIV-1 Infection

Ibalizumab (Trogarzo^®; ibalizumab-uiyk) is the first monoclonal antibody to be approved for the treatment of HIV-1 infection. As a CD4-directed post-attachment inhibitor, ibalizumab blocks HIV-1 entry into CD4 cells while preserving normal immune function. Ibalizumab, in combination with other antiretroviral(s), is indicated in the USA for the treatment of heavily treatment-experienced adults with multidrug-resistant HIV-1 infection failing their current antiretroviral regimen, and in the EU for the treatment of adults infected with multidrug-resistant HIV-1 infection for whom it is otherwise not possible to construct a suppressive antiviral regimen. In the pivotal phase III TMB-301 trial, ibalizumab significantly reduced the viral load 7 days after being added to a failing antiretroviral regimen. Almost half of all patients achieved an undetectable viral load after 24 weeks of treatment with ibalizumab plus an optimized background regimen, with virological suppression maintained over the longer term (up to 96 weeks) in an expanded access protocol. The drug was generally well tolerated in clinical trials. Although additional studies and long-term post-marketing data are needed to fully determine its efficacy and safety, ibalizumab represents a valuable and much needed treatment option for patients with multidrug-resistant HIV-1 infection.

Ibalizumab: The First Monoclonal Antibody for the Treatment of HIV-1 Infection

OBJECTIVE

To review the efficacy and safety of ibalizumab (IBA) in the treatment of HIV-1 infection.

DATA SOURCES

A literature search was performed using PubMed and Google Scholar (2010 to mid-June 2020) with the search terms TMB-355, TNX-355, and ibalizumab. Other resources included abstracts presented at recent conferences and the manufacturer's website and prescribing information.

STUDY SELECTION AND DATA EXTRACTION

All relevant English-language articles of studies assessing the efficacy and safety of IBA were included.

DATA SYNTHESIS

IBA is a monoclonal antibody that blocks HIV-1 from infecting CD4+ T cells. IBA is approved by the Food and Drug Administration, in combination with other antiretrovirals (ARVs), for the treatment of HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant (MDR) HIV-1 infection failing their current ARVs. IBA demonstrated significant and sustained antiviral activity in patients with MDR HIV-1 infection who had advanced disease and limited treatment options. It carries a warning regarding the development of immune reconstitution inflammatory syndrome. Common adverse reactions include diarrhea, dizziness, nausea, and rash.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

IBA represents an attractive option for treatment-experienced adults with advanced HIV-1 infection who are no longer able to achieve viral suppression on oral ARV therapy alone and who are able to adhere to an infusion therapy every 2 weeks. As with other biologics, there is a potential for the development of antibodies to IBA that can compromise its efficacy and safety.

CONCLUSION

IBA provides a needed treatment option to achieve and maintain viral suppression in heavily treatment-experienced adults with MDR HIV-1 infection.

Characterization of a human monoclonal antibody generated from a B-cell specific for a prefusion-stabilized spike protein of Middle East respiratory syndrome coronavirus

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory infection and continues to infect humans, thereby contributing to a high mortality rate (34.3% in 2019). In the absence of an available licensed vaccine and antiviral agent, therapeutic human antibodies have been suggested as candidates for treatment. In this study, human monoclonal antibodies were isolated by sorting B cells from patient's PBMC cells with prefusion stabilized spike (S) probes and a direct immunoglobulin cloning strategy. We identified six receptor-binding domain (RBD)-specific and five S1 (non-RBD)-specific antibodies, among which, only the RBD-specific antibodies showed high neutralizing potency (IC50 0.006-1.787 μg/ml) as well as high affinity to RBD. Notably, passive immunization using a highly potent antibody (KNIH90-F1) at a relatively low dose (2 mg/kg) completely protected transgenic mice expressing human DPP4 against MERS-CoV lethal challenge. These results suggested that human monoclonal antibodies isolated by using the rationally designed prefusion MERS-CoV S probe could be considered potential candidates for the development of therapeutic and/or prophylactic antiviral agents for MERS-CoV human infection.

Advances in Long-Acting Agents for the Treatment of HIV Infection

Long-acting antiretroviral therapy holds the promise of new options for human immunodeficiency virus (HIV) treatment beyond the current paradigm of daily oral pills. Of particular interest is their potential role in addressing challenges with adherence to oral therapy and treatment fatigue. Similar to other conditions where long-acting formulations have proven effective such as contraception and mental health, long-acting antiretroviral therapy could provide additional treatment choices to people with HIV. This review provides an outline of the current landscape of long-acting antiretroviral therapy for HIV treatment, both approved and under development, including cabotegravir, rilpivirine, leronlimab, islatravir, albuvirtide, GS-6207, and broadly neutralizaing antibodies. However, there are a number of research gaps for long-acting antiretroviral therapy including issues regarding resistance and understudied populations, and this review highlights some of the challenges that will need to be addressed for clinical implementation of these novel treatment modalities.

Current and future priorities for the development of optimal HIV drugs

PURPOSE OF REVIEW

To summarize global efforts to accelerate access to simpler, safer and more affordable antiretroviral drugs and how this has shaped HIV treatment policy over the last decade, and outline future priorities. Several expert consultations aimed at aligning opportunities for optimization of antiretroviral drugs have been convened by WHO in partnership with academic institutions, international agencies, innovators and manufacturers. The increased access to lifelong treatment for people living with HIV also brings about new challenges in the long-term use of antiretrovirals (ARVs).

RECENT FINDINGS

The article describes the evolution of global research agenda on ARV optimization ascribing the characteristics of a target product profile, the importance of sequencing of first-line and second-line regimens, the role of programmatic data when looking at policy transition for new ARVs, inclusion of more subpopulations living with HIV, as well as the challenges in identifying what improvements can be made in an era where drugs are already safe, tolerable and efficacious.

SUMMARY

Within a framework of evolving treatment harmonization and simplification, future therapeutic options in development must take into consideration safety and efficacy across a range of patient populations as well the mode of administration in the context of lifelong therapy.

Bictegravir in a fixed-dose tablet with emtricitabine and tenofovir alafenamide for the treatment of HIV infection: pharmacology and clinical implications

INTRODUCTION

Current antiretroviral therapy is more effective and simpler than in previous times due to the development of new drugs with improved pharmacokinetic and pharmacodynamic profiles and the advent of single pill regimens with low toxicity that facilitate long-term adherence. The recent approval of the novel potent integrase strand-transfer inhibitor bictegravir (BIC) co-formulated with emtricitabine (FTC) and tenofovir alafenamide (TAF) in a fixed daily dose pill, B/F/TAF, adds to the list of single-tablet regimens available to treat HIV infection. Areas covered: This review provides an overview of the pharmacological and clinical information obtained from MEDLINE/PubMed publications and the latest international conferences. Expert opinion: BIC is a potent antiretroviral with an improved resistance profile over previous integrase inhibitors. Its combination with the new tenofovir prodrug TAF and FTC creates an effective regimen B/F/TAF for treatment-naïve patients and for those switching from another successful combination. B/F/TAF's favorable pharmacokinetic profile, simple dose, low pill burden, and few drug-drug interactions or treatment-related adverse events, will make it one of the preferred regimens in the future.