The Promise of Long-Acting Antiretroviral Therapies: From Need to Manufacture

Lipid-conjugated nucleoside monophosphate and monophosphonate prodrugs: A versatile drug delivery paradigm

Integrating lipid conjugation strategies into the design of nucleoside monophosphate and monophosphonate prodrugs is a well-established approach for discovering potential therapeutics. The unique prodrug design endows nucleoside analogues with strong lipophilicity and structures resembling lysoglycerophospholipids, which improve cellular uptake, oral bioavailability and pharmacological activity. In addition, the metabolic stability, pharmacological activity, pharmacokinetic profiles and biodistribution of lipid prodrugs can be finely optimized by adding biostable caps, incorporating transporter-targeted groups, inserting stimulus-responsive bonds, adjusting chain lengths, and applying proper isosteric replacements. This review summarizes recent advances in the structural features and application fields of lipid-conjugated nucleoside monophosphate and monophosphonate prodrugs. This collection provides deep insights into the increasing repertoire of lipid prodrug development strategies and offers design inspirations for medicinal chemists for the development of novel chemotherapeutic agents.

The Phenomenon of Antiretroviral Drug Resistance in the Context of Human Immunodeficiency Virus Treatment: Dynamic and Ever Evolving Subject Matter

Human immunodeficiency virus (HIV) is a significant global health issue that affects a substantial number of individuals across the globe, with a total of 39 million individuals living with HIV/AIDS. ART has resulted in a reduction in HIV-related mortality. Nevertheless, the issue of medication resistance is a significant obstacle in the management of HIV/AIDS. The unique genetic composition of HIV enables it to undergo rapid mutations and adapt, leading to the emergence of drug-resistant forms. The development of drug resistance can be attributed to various circumstances, including noncompliance with treatment regimens, insufficient dosage, interactions between drugs, viral mutations, preexposure prophylactics, and transmission from mother to child. It is therefore essential to comprehend the molecular components of HIV and the mechanisms of antiretroviral medications to devise efficacious treatment options for HIV/AIDS.

Long-acting microneedle formulations

The minimally-invasive and painless nature of microneedle (MN) application has enabled the technology to obviate many issues with injectable drug delivery. MNs not only administer therapeutics directly into the dermal and ocular space, but they can also control the release profile of the active compound over a desired period. To enable prolonged delivery of payloads, various MN types have been proposed and evaluated, including dissolving MNs, polymeric MNs loaded or coated with nanoparticles, fast-separable MNs hollow MNs, and hydrogel MNs. These intricate yet intelligent delivery platforms provide an attractive approach to decrease side effects and administration frequency, thus offer the potential to increase patient compliance. In this review, MN formulations that are loaded with various therapeutics for long-acting delivery to address the clinical needs of a myriad of diseases are discussed. We also highlight the design aspects, such as polymer selection and MN geometry, in addition to computational and mathematical modeling of MNs that are necessary to help streamline and develop MNs with high translational value and clinical impact. Finally, up-scale manufacturing and regulatory hurdles along with potential avenues that require further research to bring MN technology to the market are carefully considered. It is hoped that this review will provide insight to formulators and clinicians that the judicious selection of materials in tandem with refined design may offer an elegant approach to achieve sustained delivery of payloads through the simple and painless application of a MN patch.

Prodrug approaches for the development of a long-acting drug delivery systems

Long-acting formulations are designed to reduce dosing frequency and simplify dosing schedules by providing an extended duration of action. One approach to obtain long-acting formulations is to combine long-acting prodrugs (LA-prodrug) with existing or emerging drug delivery technologies (DDS). The design criteria for long-acting prodrugs are distinct from conventional prodrug strategies that alter absorption, distribution, metabolism, and excretion (ADME) parameters. Our review focuses on long-acting prodrug delivery systems (LA-prodrug DDS), which is a subcategory of long-acting formulations where prodrug design enables DDS formulation to achieve an extended duration of action that is greater than the parent drug. Here, we define LA-prodrugs as the conjugation of an active pharmaceutical ingredient (API) to a promoiety group via a cleavable covalent linker, where both the promoiety and linker are selected to enable formulation and administration from a drug delivery system (DDS) to achieve an extended duration of action. These LA-prodrug DDS results in an extended interval where the API is within a therapeutic range without necessarily altering ADME as is typical of conventional prodrugs. The conversion of the LA-prodrug to the API is dependent on linker cleavage, which can occur before or after release from the DDS. The requirement for linker cleavage provides an additional tool to prolong release from these LA-prodrug DDS. In addition, the physicochemical properties of drugs can be tuned by promoiety selection for a particular DDS. Conjugation with promoieties that are carriers or amenable to assembly into carriers can also provide access to formulations designed for extending duration of action. LA-prodrugs have been applied to a wide variety of drug delivery strategies and are categorized in this review by promoiety size and complexity. Small molecule promoieties (typically MW < 1000 Da) have been used to improve encapsulation or partitioning as well as broaden APIs for use with traditional long-acting formulations such as solid drug dispersions. Macromolecular promoieties (typically MW > 1000 Da) have been applied to hydrogels, nanoparticles, micelles, dendrimers, and polymerized prodrug monomers. The resulting LA-prodrug DDS enable extended duration of action for active pharmaceuticals across a wide range of applications, with target release timescales spanning days to years.

Factors Associated with Preferences for Long-Acting Injectable Antiretroviral Therapy Among Adolescents and Young People Living with HIV in South Africa

Long-acting injectable anti-retroviral therapy (LAART) may overcome barriers to long-term adherence and improve the survival of adolescents and young people living with HIV (AYLHIV). Research on the acceptability of LAART for this age-group is limited. We asked 953 AYLHIV about their preferred (theoretical) ART mode of delivery (pill, injectable, or other) in 2017-2018, before LAART was available or known to AYLHIV in South Africa. One in eight (12%) AYLHIV preferred LAART over single or multiple pill regimens. In multivariate analyses, six factors were associated with LAART preference: medication stock-outs (aOR = 2.56, 95% CI 1.40-4.68, p = 0.002), experiencing side-effects (aOR = 1.84, 95% CI 1.15-2.97, p = 0.012), pill-burden (aOR = 1.88, 95% CI 1.20-2.94, p = 0.006), past-year treatment changes (aOR = 1.63, 95% CI 1.06-2.51, p = 0.025), any HIV stigma (aOR = 2.22, 95% CI 1.39-3.53, p ≤ 0.001) and recent ART initiation (aOR = 2.02, 95% CI 1.09-3.74, p = 0.025). In marginal effects modelling, 66% of adolescents who experienced all factors were likely to prefer LAART, highlighting the potential high acceptability of LAART among adolescents and young people living with HIV struggling to adhere and have good HIV treatment outcomes. Adolescent boys who reported high ART pill burden were more likely to prefer LAART than their female peers in moderation analyses, suggesting that LAART may be particularly important to improve treatment outcomes among male AYLHIV as they become older. Adding LAART to existing treatment options for AYLHIV, particularly higher risk groups, would support AYLHIV to attain and sustain viral suppression-the third 95, and reduce their risk of AIDS-related mortality.

Engineering antiviral immune-like systems for autonomous virus detection and inhibition in mice

The ongoing COVID-19 pandemic has demonstrated that viral diseases represent an enormous public health and economic threat to mankind and that individuals with compromised immune systems are at greater risk of complications and death from viral diseases. The development of broad-spectrum antivirals is an important part of pandemic preparedness. Here, we have engineer a series of designer cells which we term autonomous, intelligent, virus-inducible immune-like (ALICE) cells as sense-and-destroy antiviral system. After developing a destabilized STING-based sensor to detect viruses from seven different genera, we have used a synthetic signal transduction system to link viral detection to the expression of multiple antiviral effector molecules, including antiviral cytokines, a CRISPR-Cas9 module for viral degradation and the secretion of a neutralizing antibody. We perform a proof-of-concept study using multiple iterations of our ALICE system in vitro, followed by in vivo functionality testing in mice. We show that dual output ALICE_SaCas9+Ab system delivered by an AAV-vector inhibited viral infection in herpetic simplex keratitis (HSK) mouse model. Our work demonstrates that viral detection and antiviral countermeasures can be paired for intelligent sense-and-destroy applications as a flexible and innovative method against virus infection.

3D-printed implantable devices with biodegradable rate-controlling membrane for sustained delivery of hydrophobic drugs

Implantable drug delivery systems offer an alternative for the treatments of long-term conditions (i.e. schizophrenia, HIV, or Parkinson’s disease among many others). The objective of the present work was to formulate implantable devices loaded with the model hydrophobic drug olanzapine (OLZ) using robocasting 3D-printing combined with a pre-formed rate controlling membrane. OLZ was selected as a model molecule due to its hydrophobic nature and because is a good example of a molecule used to treat a chronic condition schizophrenia. The resulting implants consisted of a poly(ethylene oxide) (PEO) implant coated with a poly(caprolactone) (PCL)-based membrane. The implants were loaded with 50 and 80% (w/w) of OLZ. They were prepared using an extrusion-based 3D-printer from aqueous pastes containing 36–38% (w/w) of water. The printing process was carried out at room temperature. The resulting implants were characterized by using infrared spectroscopy, scanning electron microscopy, thermal analysis, and X-ray diffraction. Crystals of OLZ were present in the implant after the printing process. In vitro release studies showed that implants containing 50% and 80% (w/w) of OLZ were capable of providing drug release for up to 190 days. On the other hand, implants containing 80% (w/w) of OLZ presented a slower release kinetics. After 190 days, total drug release was ca. 77% and ca. 64% for implants containing 50% and 80% (w/w) of OLZ, respectively. The higher PEO content within implants containing 50% (w/w) of OLZ allows a faster release as this polymer acts as a co-solvent of the drug.

Prodrug Therapies for Infectious and Neurodegenerative Diseases

Prodrugs are bioreversible drug derivatives which are metabolized into a pharmacologically active drug following chemical or enzymatic modification. This approach is designed to overcome several obstacles that are faced by the parent drug in physiological conditions that include rapid drug metabolism, poor solubility, permeability, and suboptimal pharmacokinetic and pharmacodynamic profiles. These suboptimal physicochemical features can lead to rapid drug elimination, systemic toxicities, and limited drug-targeting to disease-affected tissue. Improving upon these properties can be accomplished by a prodrug design that includes the careful choosing of the promoiety, the linker, the prodrug synthesis, and targeting decorations. We now provide an overview of recent developments and applications of prodrugs for treating neurodegenerative, inflammatory, and infectious diseases. Disease interplay reflects that microbial infections and consequent inflammation affects neurodegenerative diseases and vice versa, independent of aging. Given the high prevalence, personal, social, and economic burden of both infectious and neurodegenerative disorders, therapeutic improvements are immediately needed. Prodrugs are an important, and might be said a critical tool, in providing an avenue for effective drug therapy.

Building a Culture of Medicinal Chemistry Knowledge Sharing

Increasing the efficiency of the drug discovery process is a challenge faced by drug hunters everywhere. One strategy medicinal chemists employ to meet this challenge is learning from knowledge sources within and beyond their organization. In this Perspective, we discuss the evolution of mechanisms for medicinal chemistry knowledge capture and sharing at Merck & Co. over the past 15 years. We describe our approach to knowledge management and report on the multiple enduring and complementary teams and initiatives we have created to capture and share knowledge within a geographically diverse medicinal chemistry community. In addition, this Perspective will share the benefits we have observed and also reflect on what has allowed our efforts to be both successful and sustainable.

Designing a Predictive Model for Antiretroviral Regimen at the Antiretroviral Therapy Center in Chiro Hospital, Ethiopia

Nowadays, the huge amount of patient's data significantly increases with respect to the time in repositories and data mining is increasingly used as an emerging research area in medical fields for extracting useful and previously unknown insights/patterns from the repository data. These unknown patterns/hidden insights can help in discovering new knowledge hidden in these data repositories. From the observation, different ARV regimens were ordered for different patients. However, combination of these drugs causes different side effects on the patients. It has been observed that there was a lack of predictive studies and designed models available in hospitals specifically ART Centers that accurately determine or classify the patient's ARV regimen to TDF + 3TC + EFV, TDF + 3TC + NVP, AZT + 3TC + ATV/R, AZT + 3TC + LPV/R, TDF + 3TC + LVP/R, TDF + 3TC + ATV/R, 8888, and ABC + 3TC + LPV/R. In order to solve these kinds of problems, we built an accurate classifier system or model using parameters like Patient Age, Patient Encounter Day, Patient Encounter Month, Patient Encounter Year, Patient Weight, Patient CD4 Count Adult, Patient TB Screen, Patient Following WHO Stage, Patient CD4 Percent Child, Patient Regimen Specify, Patient Regimen, and so on. The general objective of this research was predictive modeling for the patient's ARV regimen class through data mining techniques so as to improve them. The study used the CRIPS-DM methodology to find and interpret patterns in repositories. A decision tree (J48 and Random Forest) algorithm was used for classification. Using all tested classifiers, the investigation of the study shows that the total accuracy was more than 60%. On the other hand, among different classifications, class H (ABC + 3TC + LPV/R) has shown the worst prediction. But it was revealed that the J48 classifier relatively produces higher classification accuracy for the D (AZT-3TC-NVP) regimen. Here, classification depended on the selected parameters, which revealed that prediction accuracy value differed among all classifiers and the selected attributes. Finally, the study concluded that data mining can be used as a significant technique to discover patient regimen based on salient affecting factors with 96.1% precision achieved. Ensemble learning resolves the categorizing models of greater anticipating performance with different learning algorithms. This model aligned with sentimental investigation to magnify the appearances of the dataset either from the social media or from primary data collection. The empirical investigation with different parameters shows the detailed improvement of their learning methods.

A patient-centred approach to deprescribing antiretroviral therapy in people living with HIV

Only a few studies have explored the benefit of deprescribing in people living with HIV (PLWH), focusing on the discontinuation of non-antiretrovirals (non-ARVs) used for HIV-associated comorbidities (co-medications), or the management of drug-drug interactions (DDIs) between ARVs or between ARVs and co-medications. The availability of modern single-tablet regimens, two-drug regimens and long-acting therapy opens a discussion regarding ARV deprescribing strategies. The objective of this article is to discuss ARV deprescribing strategies in the context of medication-related burden and patients' lived experience with medicine (PLEM) and to suggest indications for whom, when, how and why to consider these ARV options in PLWH. A PLEM construct helps to better interpret these strategies and provides a patient-centred precision-medicine approach. There are several safe and virologically effective ARV deprescribing strategies, but the ultimate benefits of these interventions still need to be further explored in terms of the overall health and quality of life of patients.

Long-acting cabotegravir plus rilpivirine for treatment in adults with HIV-1 infection: 96-week results of the randomised, open-label, phase 3 FLAIR study

BACKGROUND

There is a need for more convenient, less frequent treatment to help address challenges associated with daily oral HIV treatment in people living with HIV, including stigma, pill burden, drug-food interactions, and adherence. The phase 3 ATLAS and FLAIR studies showed non-inferiority of long-acting cabotegravir and rilpivirine dosed every 4 weeks compared with standard oral therapy for the maintenance of virological suppression in adults with HIV-1 over 48 weeks. We present the 96-week findings.

METHODS

FLAIR is a randomised, phase 3, open-label, multicentre study done in 11 countries investigating whether switching to long-acting cabotegravir and rilpivirine is non-inferior to daily dolutegravir, abacavir, and lamivudine in virologically suppressed adults living with HIV-1. Antiretroviral therapy (ART)-naive participants received induction therapy with daily oral dolutegravir (50 mg), abacavir (600 mg), and lamivudine (300 mg) for 20 weeks. After 16 weeks, participants with less than 50 HIV-1 RNA copies per mL were randomly assigned (1:1) to continue the standard of care regimen (standard care group) or switch to receive daily oral cabotegravir 30 mg and rilpivirine 25 mg for at least 4 weeks followed by long-acting cabotegravir 400 mg and rilpivirine 600 mg, administered as two 2 mL intramuscular injections, every 4 weeks for at least 96 weeks (long-acting group). Randomisation was stratified by baseline (preinduction) HIV-1 RNA (<100 000 or ≥100 000 copies per mL) and sex at birth and used GlaxoSmithKline-verified randomisation software (RandAll NG, version 1.3.3) for treatment assignment. The primary endpoint was the proportion of participants with plasma HIV-1 RNA of 50 copies per mL or more assessed as per the US Food and Drug Administration (FDA) Snapshot algorithm at week 48, which has been reported previously. Here, we report the proportion of participants with 50 or more HIV-1 RNA copies per mL using the FDA Snapshot algorithm at week 96 (intention-to-treat population; non-inferiority margin 6%). The trial is registered with ClinicalTrials.gov, NCT02938520.

FINDINGS

Between Oct 27, 2016, and March 24, 2017, 809 participants were screened. 631 (78%) participants entered the induction phase and 566 (70%) were randomly assigned to either the standard care group (283 [50%] participants) or the long-acting group (283 [50%]). Median age was 34 years (IQR 29 to 43), 62 (11%) were 50 years or older, 127 (22%) were women (sex at birth), and 419 (74%) were white. At week 96, nine (3%) participants in each arm had 50 or more HIV-1 RNA copies per mL, with an adjusted difference of 0·0 (95% CI -2·9 to 2·9), consistent with non-inferiority established at week 48. Across both treatment groups, adverse events leading to withdrawal were infrequent (14 [5%] participants in the long-acting group and four [1%] in the standard care group). Injection site reactions were the most common adverse event, reported by 245 (88%) participants in the long-acting group; their frequency decreased over time. Median injection site reaction duration was 3 days (IQR 2 to 4), and 3082 (99%) of 3100 reactions were grade 1 or 2. No deaths occurred during the maintenance phase.

INTERPRETATION

The 96-week results reaffirm the 48-week results, showing long-acting cabotegravir and rilpivirine continued to be non-inferior compared with continuing a standard care regimen in adults with HIV-1 for the maintenance of viral suppression. These results support the durability of long-acting cabotegravir and rilpivirine, over an almost 2-year-long period, as a therapeutic option for virally suppressed adults with HIV-1.

FUNDING

ViiV Healthcare and Janssen Research and Development.

Emerging Trends in the Long-Acting Antiretroviral Therapy: Current Status and Therapeutic Challenges

Antiretroviral drug therapy has significantly improved the prognosis and life expectancy of people living with HIV over the years. But this progress comes with an important caveat that antiretroviral regimens generally require adherence to life-long, daily dosing, to keep viral multiplication under check. Non-adherence to such dosing leads to decreased efficacy and increased drug resistance against antiretroviral drugs. Besides, poor drug penetration to certain tissues like CNS and lymph nodes leads to the build-up of viral reservoirs in these sites. To combat some of these challenges and improve patient compliance, long-acting antiretroviral drugs, are a new weapon in the arsenal, in the fight against HIV. Few long-acting preparations have been approved, and several others are in various clinical and preclinical stages of development. However, long-acting formulations also have their share of clinical issues like limited drug distribution, long term adverse drug reactions, drug-drug interactions, and gradual development of drug resistance. Modern technological premises are being tested to mitigate some of these problems. One such promising approach involves nanotechnological methods, which are being used to develop ultra-long acting formulations and drug delivery systems, targeting tissues with residual HIV concentration. Long-Acting Slow Effective Release Antiretroviral Therapy aka LASER ART, also builds on nanotechnology and prodrug modifications to design preparations with tailor-made favorable pharmacokinetics and wider drug distribution. These recent advances are fueling the progression of antiretroviral therapy towards eliminating the disease.

Long-acting approaches for delivery of antiretroviral drugs for prevention and treatment of HIV: a review of recent research

INTRODUCTION

Despite significant advances in treatment and prevention of HIV-1 infection, poor adherence to daily combination antiretroviral therapy (ART) regimens remains a major obstacle toward achieving sustained viral suppression and prevention. Adherence to ART could also be compromised by adverse drug reactions and societal factors that limit access to therapy. Therefore, medicines that aim to improve adherence by limiting ART side effects, frequency of dosing and socially acceptable regimens are becoming more attractive.

AREAS COVERED

This review highlights recent advances and challenges in the development of long-acting drug delivery strategies for HIV prevention and treatment. Approaches for extended oral and transdermal deliveries, microbicides, broadly neutralizing antibodies, and long-acting implantable and injectable deliveries are reviewed.

EXPERT OPINION

Emerging approaches on long-acting antiretroviral therapies and broadly neutralizing antibody technologies are currently at various stages of development. Such efforts, if successful and become broadly accepted by clinicians and users, will provide newer and simpler options for prevention and treatment of HIV infection.

A year-long extended release nanoformulated cabotegravir prodrug

Long-acting cabotegravir (CAB) extends antiretroviral drug administration from daily to monthly. However, dosing volumes, injection site reactions and health-care oversight are obstacles towards a broad usage. The creation of poloxamer-coated hydrophobic and lipophilic CAB prodrugs with controlled hydrolysis and tissue penetrance can overcome these obstacles. To such ends, fatty acid ester CAB nanocrystal prodrugs with 14, 18 and 22 added carbon chains were encased in biocompatible surfactants named NMCAB, NM2CAB and NM3CAB and tested for drug release, activation, cytotoxicity, antiretroviral activities, pharmacokinetics and biodistribution. Pharmacokinetics studies, performed in mice and rhesus macaques, with the lead 18-carbon ester chain NM2CAB, showed plasma CAB levels above the protein-adjusted 90% inhibitory concentration for up to a year. NM2CAB, compared with NMCAB and NM3CAB, demonstrated a prolonged drug release, plasma circulation time and tissue drug concentrations after a single 45 mg per kg body weight intramuscular injection. These prodrug modifications could substantially improve CAB's effectiveness.

Recent advances in long-acting nanoformulations for delivery of antiretroviral drugs

In spite of introduction of combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV) infection; inaccessibility and poor adherence to oral cART costs 10 in 100,000 death worldwide. Failure in adherence leads to viral rebound, emergence of drug resistance and anticipated HIV infection in high risk individuals. Various Long-acting antiretroviral (LA ARV) nanoformulations including nano-prodrug, solid drug nanoparticles (SDN), nanocrystals, aspherical nanoparticles, polymeric and lipidic nanoparticles have shown plasma/tissue drug concentration in the therapeutic range for several weeks during pre-clinical evaluation. LA ARV nanoformulations therefore have replaced cART as better alternative for the treatment of HIV infection. Cabenuva™ is recently approved by Health Canada containing LA cabotegravir+LA rilpivirine nanocrystals (ViiV healthcare) for once monthly administration by intramuscular route. The LA nanoformulation due to its nanosize insist on better stability, delivery to lymphatic, slow release into systemic circulation via lymphatic-circulatory system conjoint and secondary drug depot within infiltered immune cells at site of administration and systemic circulation in contrast to conventional drugs. However, the pharmacokinetic, biodistribution and efficacy of LA nanoformulations hinge onto physicochemical properties of the drugs and route of administration. Therefore, current review emphasizes on these contradistinctive factors that affects the reproducibility, safety, efficacy and toxicity of LA anti-HIV nanoformulations. Moreover, it expatiates on application of profuse nanoformulations for long-acting effect with promising preclinical discoveries and two clinical leads. To add on, utilization of physiology-based and mechanism-based pharmacokinetic modelling and in vivo animal models which could lead to enhanced safety and efficacy of LA ARV nanoformulations in humans have been included.

Integration of Computational and Experimental Approaches to Elucidate Mechanisms of First-Pass Lymphatic Drug Sequestration and Long-Acting Pharmacokinetics of the Injectable Triple-HIV Drug Combination TLC-ART 101

TLC-ART101 is a long-acting triple-HIV drug combination of lopinavir-ritonavir-tenofovir in one nanosuspension intended for subcutaneous injection. After a single TLC-ART 101 administration in nonhuman primates, drug concentrations in both plasma and HIV-target lymph node mononuclear cells were sustained for 2 weeks. Nevertheless, the mechanisms leading to the targeted long-acting pharmacokinetics remain elusive. Therefore, an intravenous study of TLC-ART 101 in nonhuman primates was conducted to elucidate the degree of association of drugs in vivo, estimate subcutaneous bioavailability, and refine a mechanism-based pharmacokinetic (MBPK2) model. The MBPK2 model considers TLC-ART 101 systemic drug clearances, nanoparticle-associated/dissociated species, more detailed mechanisms of lymphatic first-pass retention of associated-drugs after subcutaneous administrations, and the prediction of drug concentration time-courses in lymph node mononuclear cells. For all 3 drugs, we found a high association with the nanoparticles in plasma (>87% lopinavir-ritonavir, 97% tenofovir), and an incomplete subcutaneous bioavailability (<29% lopinavir-ritonavir, 85% tenofovir). As hypothesized by the MBPK2 model, the incomplete SC bioavailability observed is due to sequestration into a lymphatic node depot after subcutaneous absorption (unlike most intramuscular nanodrug products having near-to-injection depots), which contributes to long-acting profiles detected in plasma and target cells. This combined experimental and modeling approach may be applicable for the clinical development of other long-acting drug-combination injectables.

N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK) inhibits HIV-1 by suppressing the activity of viral protease

Human Immunodeficiency Virus (HIV), the etiological agent for Acquired Immunodeficiency Syndrome (AIDS), continues to kill humans despite stupendous advances in antiviral research. With the presently available combination antiretroviral therapeutic arsenal, AIDS is now a manageable disease but with no cure available till date. The development of novel antivirals consumes an extensive amount of time and resources. Hence, repurposing of the established gold standard molecules for their anti-HIV application is enormously advantageous. In this study, we report that N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK) inhibits HIV-1 replication in a highly-conserved manner. Further, TPCK inhibits HIV-1 replication at the late stages of its life cycle by impeding viral protease (PR) enzyme activity. Additionally, our results demonstrate that the combination of TPCK with established HIV-1 PR inhibitors shows significant synergistic inhibitory potential, suggesting the potential use of TPCK in cART regimen. Collectively, we report the anti-HIV activity of TPCK, which should be further characterized for its translational applications.

Pathways towards human immunodeficiency virus elimination

Antiretroviral therapy (ART) suppresses human immunodeficiency virus (HIV) infection. Research seeking to transform viral suppression into elimination has generated novel immune, chemical and molecular antiviral agents. However, none, to date, have excised latent integrated proviral DNA or removed infected cells from infected persons. These efforts included, but are not limited to, broadly neutralizing antibodies, "shock" and "kill" latency-reversing agents, innate immune regulators, and sequential long-acting antiretroviral nanoformulated prodrugs and CRISPR-Cas9 gene editing. While, the latter, enabled the complete excision of latent HIV-1 from the host genome success was so far limited. We contend that improvements in antiretroviral delivery, potency, agent specificity, or combinatorial therapies can provide a pathway towards complete HIV elimination.

Amplification of Replication Competent HIV-1 by Adoptive Transfer of Human Cells From Infected Humanized Mice

Detection of latent human immunodeficiency virus type 1 (HIV-1) in "putative" infectious reservoirs is required for determining treatment efficiency and for viral elimination strategies. Such tests require induction of replication competent provirus and quantitative testing of viral load for validation. Recently, humanized mice were employed in the development of such tests by employing a murine viral outgrowth assay (mVOA). Here blood cells were recovered from virus infected antiretroviral therapy suppressed patients. These cells were adoptively transferred to uninfected humanized mice where replication competent virus was recovered. Prior reports supported the notion that an mVOA assay provides greater sensitivity than cell culture-based quantitative VOA tests for detection of latent virus. In the current study, the mVOA assays was adapted using donor human hematopoietic stem cells-reconstituted mice to affirm research into HIV-1 elimination. We simulated an antiretroviral therapy (ART)-treated virus-infected human by maintaining the infected humanized mice under suppressive treatment. This was operative prior to human cell adoptive transfers. Replication-competent HIV-1 was easily detected in recipient animals from donors with undetectable virus in plasma. Moreover, when the assay was used to investigate viral presence in tissue reservoirs, quantitative endpoints were determined in "putative" viral reservoirs not possible in human sample analyses. We conclude that adoptive transfer of cells between humanized mice is a sensitive and specific assay system for detection of replication competent latent HIV-1.

Lessons Learned From Failures and Success Stories of HIV Breakthroughs: Are We Getting Closer to an HIV Cure?

There is a continuous search for an HIV cure as the success of ART in blocking HIV replication and the role of CD4+ T cells in HIV pathogenesis and immunity do not entirely eradicate HIV. The Berlin patient, who is virus-free, serves as the best model for a 'sterilizing cure' and many experts are trying to mimic this approach in other patients. Although failures were reported among Boston and Essen patients, the setbacks have provided valuable lessons to strengthen cure strategies. Following the Berlin patient, two more patients known as London and Düsseldorf patients might be the second and third person to be cured of HIV. In all the cases, the patients underwent chemotherapy regimen due to malignancy and hematopoietic stem cell transplantation (HSCT) which required matching donors for CCR5Δ32 mutation - an approach that may not always be feasible. The emergence of newer technologies, such as long-acting slow-effective release ART (LASER ART) and CRISPR/Cas9 could potentially overcome the barriers due to HIV latency and persistency and eliminate the need for CCR5Δ32 mutation donor. Appreciating the failure and success stories learned from these HIV breakthroughs would provide some insight for future HIV eradication and cure strategies.

A literature review of the patent application publications on cabotegravir - an HIV integrase strand transfer inhibitor

Introduction: Studies presented in the patent applications demonstrate that a new integrase strand transfer inhibitor cabotegravir might be used as long-acting antiretroviral formulation or delivery system that reduces dosing frequency and may therefore increase adherence and thus pre-exposure prophylaxis (PrEP) and treatment efficacy against HIV. As announced in 2019, the developer ViiV Healthcare seeks US and EU approval of long-acting, injectable HIV treatment.Area covered: This review covers all the patent applications published until October 2019 with cabotegravir in the examples or claim section of the patent application document. The patent applications cover drug substance synthesis, solid-state forms, therapeutic applications, in vitro and in vivo efficacy as well as the potential formulations of cabotegravir alone or in combination with other anti-HIV agents.Expert opinion: The results from multiple clinical studies suggest that cabotegravir can be used as PrEP agent and treatment agent against HIV. Multiple studies use cabotegravir in combination with other anti-HIV agents such as rilpivirine. Cabotegravir in combination with rilpivirine is an interesting therapeutic, due to the possibility of formulating long-acting formulation with dosing interval of every 4 weeks or less, thus reducing daily pill burden and improving patient's compliance.

Rod-shape theranostic nanoparticles facilitate antiretroviral drug biodistribution and activity in human immunodeficiency virus susceptible cells and tissues

Human immunodeficiency virus theranostics facilitates the development of long acting (LA) antiretroviral drugs (ARVs) by defining drug-particle cell depots. Optimal drug formulations are made possible based on precise particle composition, structure, shape and size. Through the creation of rod-shaped particles of defined sizes reflective of native LA drugs, theranostic probes can be deployed to measure particle-cell and tissue biodistribution, antiretroviral activities and drug retention.

Methods: Herein, we created multimodal rilpivirine (RPV) ¹⁷⁷lutetium labeled bismuth sulfide nanorods (¹⁷⁷LuBSNRs) then evaluated their structure, morphology, configuration, chemical composition, biological responses and adverse reactions. Particle biodistribution was analyzed by single photon emission computed tomography (SPECT/CT) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) imaging.

Results: Nanoformulated RPV and BSNRs-RPV particles showed comparable physicochemical and cell biological properties. Drug-particle pharmacokinetics (PK) and biodistribution in lymphoid tissue macrophages proved equivalent, one with the other. Rapid particle uptake and tissue distribution were observed, without adverse reactions, in primary blood-derived and tissue macrophages. The latter was seen within the marginal zones of spleen.

Conclusions: These data, taken together, support the use of ¹⁷⁷LuBSNRs as theranostic probes as a rapid assessment tool for PK LA ARV measurements.

Small Animal Models for Human Immunodeficiency Virus (HIV), Hepatitis B, and Tuberculosis: Proceedings of an NIAID Workshop

The main advantage of animal models of infectious diseases over in vitro studies is the gain in the understanding of the complex dynamics between the immune system and the pathogen. While small animal models have practical advantages over large animal models, it is crucial to be aware of their limitations. Although the small animal model at least needs to be susceptible to the pathogen under study to obtain meaningful data, key elements of pathogenesis should also be reflected when compared to humans. Well-designed small animal models for HIV, hepatitis viruses and tuberculosis require, additionally, a thorough understanding of the similarities and differences in the immune responses between humans and small animals and should incorporate that knowledge into the goals of the study. To discuss these considerations, the NIAID hosted a workshop on 'Small Animal Models for HIV, Hepatitis B, and Tuberculosis' on May 30, 2019. Highlights of the workshop are outlined below.

Creation of a long-acting rilpivirine prodrug nanoformulation

Antiretroviral therapy requires lifelong daily dosing to attain viral suppression, restore immune function, and improve quality of life. As a treatment alternative, long-acting (LA) antiretrovirals can sustain therapeutic drug concentrations in blood for prolonged time periods. The success of recent clinical trials for LA parenteral cabotegravir and rilpivirine highlight the emergence of these new therapeutic options. Further optimization can improve dosing frequency, lower injection volumes, and facilitate drug-tissue distributions. To this end, we report the synthesis of a library of RPV prodrugs designed to sustain drug plasma concentrations and improved tissue biodistribution. The lead prodrug M3RPV was nanoformulated into the stable LA injectable NM3RPV. NM3RPV treatment led to RPV plasma concentrations above the protein-adjusted 90% inhibitory concentration for 25 weeks with substantial tissue depots after a single intramuscular injection in BALB/cJ mice. NM3RPV elicited 13- and 26-fold increases in the RPV apparent half-life and mean residence time compared to native drug formulation. Taken together, proof-of-concept is provided that nanoformulated RPV prodrugs can extend the apparent drug half-life and improve tissue biodistribution. These results warrant further development for human use.