Pharmacokinetic Modeling to Guide Preclinical Development of an Islatravir-Eluting Reservoir-Style Biodegradable Implant for Long-Acting HIV PrEP.

Long-acting injectable cabotegravir is more effective than daily oral PrEP at preventing HIV transmission due to improved adherence, but requires bi-monthly large-volume intramuscular injections. Subcutaneous (SC) contraceptive implants can be formulated with antiretrovirals for extended-duration HIV PrEP. Islatravir (ISL) is a first-in-class, investigational antiretroviral with pharmacologic properties well-suited for implant delivery. We performed preclinical studies for the development of a reservoir-style, poly(ε-caprolactone) ISL-eluting implant by conducting a single-dose SC ISL dose-ranging pharmacokinetic (PK) study of 0.1, 0.3, and 1 mg/kg in adult Wistar rats. Non-compartmental analysis was conducted, and dose proportionality assessed for ISL plasma and intracellular islatravir-triphosphate (ISL-tp). Population PK models estimated ISL's unit impulse response to deconvolve ISL-implant in vivo absorption rate (mg/day) and cumulative mass (mg) from published rat plasma PK (n = 10). Drug release was interpreted using four kinetic models. Dose proportionality was affirmed for ISL and ISL-tp. A first-order, two-compartment model fitted the SC ISL bolus data. Mean (SD) absorption rate from 0 to 154 days was 0.072 ± 0.024 mg/day, and cumulative mass at 154 days was 8.67 ± 3.22 mg. ISL absorption was well-described by zero-order (r2 = 0.95) and Ritger-Peppas (r2 = 0.98). Our zero-order ISL-release poly(ε-caprolactone) implant is projected to achieve clinical PK above ISL-tp's PrEP efficacy threshold. Continued development for HIV PrEP applications is warranted.

HIV and urethritis: time required for antiretroviral therapy to suppress HIV in semen.

OBJECTIVES: To examine the time required to suppress HIV in the genital tract with antiretroviral therapy (ART) in men with urethritis. DESIGN: An observational cohort study. METHODS: Men with HIV and urethritis not on ART were enrolled at an STI clinic in Malawi and offered to initiate ART. Blood and semen samples were collected pretreatment and at 1, 2, 4, 8, 12 and 24 weeks posturethritis treatment. Median viral loads (VLs) were calculated by ART initiation groups: 'within 1 week', 'between 1 and 4 weeks' and 'no ART before 4 weeks', based on the men's choice about whether or not to initiate ART. The presence of ART at each visit was confirmed by bioanalytical methods. FINDINGS: Between January 2017 and November 2018, 74 men presented with urethritis and HIV and were confirmed ART naive. The median age was 32 years. Forty-one (55% of men) initiated ART within 1 week; 12 (16%) between 1 and 4 weeks; and 21 (28%) did not initiate ART by week 4. Within the 1 week group, median VL was suppressed within 4 weeks in both semen and blood. Among the 1-4 weeks group, VL was suppressed within 4 weeks in semen and 5 weeks in blood. Among the no ART before 4 weeks group, VL in semen declined within the first 4 weeks but remained unsuppressed through week 24, and there was no significant decline in blood HIV. CONCLUSION: Treatment of urethritis and prompt initiation of ART with counseling for safer sex for at least one month is a critical measure to reduce transmission of HIV.

Gradient-mixing LEGO robots for purifying DNA origami nanostructures of multiple components by rate-zonal centrifugation.

DNA origami purification is essential for many fields, including biophysics, molecular engineering, and therapeutics. The increasing interest in DNA origami has led to the development of rate-zonal centrifugation (RZC) as a scalable, high yield, and contamination-free method for purifying DNA origami nanostructures. RZC purification uses a linear density gradient of viscous media, such as glycerol or sucrose, to separate molecules according to their mass and shape. However, many methods for creating density gradients are time-consuming because they rely on slow passive diffusion. To expedite the preparation time, we used a LEGO gradient mixer to generate rotational motion and rapidly create a quasi-continuous density gradient with a minimal layering of the viscous media. Rotating two layers of differing concentrations at an angle decreases the time needed to form the density gradient from a few hours to minutes. In this study, the density gradients created by the LEGO gradient mixer were used to purify 3 DNA origami shapes that have different aspect ratios and numbers of components, with an aspect ratio ranging from 1:1 to 1:100 and the number of components up to 2. The gradient created by our LEGO gradient mixer is sufficient to purify folded DNA origami nanostructures from excess staple strands, regardless of their aspect ratios. Moreover, the gradient was able to separate DNA origami dimers from DNA origami monomers. In light of recent advances in large-scale DNA origami production, our method provides an alternative for purifying DNA origami nanostructures in large (gram) quantities in resource-limited settings.

Doravirine Concentrations and Human Immunodeficiency Virus Type 1 RNA in the Genital Fluids of Virologically Suppressed Adults Switching to Doravirine Plus Emtricitabine/Tenofovir Alafenamide.

Doravirine (DOR) concentrations and HIV-1 RNA were evaluated in genital fluids from adults with HIV on stable therapy who switched to DOR + FTC/TAF. High protein-unbound DOR concentrations were observed in both seminal plasma and cervicovaginal fluid. DOR + FTC/TAF maintained viral suppression in genital fluids in all but 1 participant.

Intracellular islatravir pharmacology differs between species in an in vitro model: implications for preclinical study design.

BACKGROUND: Islatravir (4'-ethynyl-2-fluoro-2'-deoxyadenosine; EFdA) is a first-in-class nucleoside reverse transcriptase translocation inhibitor (NRTTI) being investigated for HIV treatment and prevention. EFdA is intracellularly phosphorylated to EFdA-triphosphate (EFdA-tp), a competitive substrate of deoxyadenosine-triphosphate (dATP). Thus, translating safety and efficacy findings from preclinical studies relies on the assumption that EFdA's intracellular pharmacology can be extrapolated across species. OBJECTIVES: We investigated how EFdA is phosphorylated across animal species commonly used for preclinical models in drug development to identify those that most closely matched humans. METHODS: PBMCs were isolated from whole blood of six species (human, rhesus macaque non-human primate (rmNHP), rat, minipig, dog, and rabbit) using Ficoll separation and counted on a haemocytometer by Trypan blue staining. One million live cells were cultured in media supplemented with 10 U/mL human IL-2, 10% FBS and 1% antibiotics and treated with 0, 17, 170, and 1700 nM EFdA (n = 3 replicates per concentration). After 24 h, representative cell counts were derived from untreated control wells (as above), cells were washed in PBS, and lysed with 70:30 methanol:water. EFdA-tp and dATP concentrations were quantified by HPLC-MS/MS and normalized to the representative live cell counts for each species. RESULTS: When compared to human values, EFdA-tp concentrations for each EFdA treatment concentration were lower in all species (rmNHP 1.5-2.1-fold, rat 4.5-15-fold, minipig 37-71-fold, dog and rabbit >100-fold). Additionally, rmNHP and dog PBMCs exhibited significantly higher (7-10-fold; P < 0.001) dATP when compared with human PBMCs. CONCLUSIONS: Given intracellular pharmacology differences, these preclinical models may be a conservative estimate of EFdA's intracellular pharmacokinetics and efficacy in humans.

Dynamics of the Decay of Human Immunodeficiency Virus (HIV) RNA and Distribution of Bictegravir in the Genital Tract and Rectum in Antiretroviral-naive Adults Living With HIV-1 Treated With Bictegravir/Emtricitabine/Tenofovir Alafenamide (Spanish HIV/AIDS Research Network, PreEC/RIS 58).

BACKGROUND: The pharmacokinetics of bictegravir (BIC) and its association with the decay of human immunodeficiency virus (HIV)-1 RNA in genital fluids and the rectum have not yet been addressed. METHODS: We conducted a prospective, multicenter study of antiretroviral-naive people living with HIV-1 and initiating BIC/emtricitabine (FTC)/tenofovir alafenamide (TAF). HIV-1 RNA was measured (limit of quantification, 40 copies/mL) in blood plasma (BP), seminal plasma (SP), rectal fluid (RF), and cervicovaginal fluid (CVF) at baseline; Days 3, 7, 14, and 28; and Weeks 12 and 24. Total and protein-unbound BIC concentrations at 24 hours postdose (C24h) were quantified in BP, SP, CVF and rectal tissue (RT) on Day 28 and Week 12 using a validated liquid chromatography-tandem mass spectrometry assay. RESULTS: The study population comprised 15 males and 8 females. In SP, RF, and CVF, the baseline HIV-1 RNA was >40 copies/mL in 12/15, 13/15, and 4/8 individuals, respectively, with medians of 3.54 (2.41-3.79), 4.19 (2.98-4.70), and 2.56 (1.61-3.56) log10 copies/mL, respectively. The initial decay slope was significantly lower in SP than in RF and BP. The time to undetectable HIV-1 RNA was significantly shorter in SP and RF than in BP. All women achieved undetectable HIV-1 RNA in CVF at Day 14. The median total BIC concentrations in SP, RT, and CVF were 65.5 (20.1-923) ng/mL, 74.1 (6.0-478.5) ng/g, and 61.6 (14.4-1760.2) ng/mL, respectively, representing 2.7%, 2.6%, and 2.8% of the BP concentration, respectively, while the protein-unbound fractions were 51.1%, 44.6%, and 42.6%, respectively. CONCLUSIONS: BIC/FTC/TAF led to rapid decay of HIV-1 RNA in genital and rectal fluids. Protein-unbound BIC concentrations in SP, RT, and CVF highly exceeded the half-maximal effective concentration (EC50) value (1.1 ng/mL). CLINICAL TRIALS REGISTRATION: EudraCT 2018-002310-12.

BURMESE ROOFED TURTLE (BATAGUR TRIVITTATA) DISEASE SCREENING IN MYANMAR.

The Burmese roofed turtle (Batagur trivittata), a critically endangered freshwater turtle, is endemic to Myanmar. Once thought to be extinct, remnant wild populations were discovered in 2001 and limited captive individuals identified in pagoda ponds or confiscated from fishers in Myanmar. These and their offspring are maintained in five facilities in Myanmar and form the basis of a conservation program (habitat protection, captive breeding, nest protection, egg collection, head-starting, and release). Prerelease health screenings were performed in 2014 and 2018 at Yadanabon Zoological Gardens, a head-starting facility in Limpha Village, and Lawkanandar Wildlife Park. One hundred forty-three turtles were assessed (37 male, 50 female, 56 juveniles [too young to determine sex]; two females were assessed in both years), age range of 1 to 12 y (one unknown age adult founder), and body mass range of 0.111 to 32.72 kg. Health evaluations both years included physical examination and combined choanal/cloacal swab samples for polymerase chain reaction testing of the potential chelonian pathogens intranuclear coccidia, Mycoplasma, Herpesvirus, Ranavirus, and Adenovirus (not all tests performed each year). In 2018, cloacal swabs from 30 and 20 turtles at the Yadanabon Zoological Gardens and Lawkanandar Wildlife Park, respectively, were cultured for Salmonella. All turtles were assessed as healthy based on normal physical examination findings, and all had negative test results. Prerelease health screening, such as performed in this study, is an important component of release, reintroduction, and translocation projects to prevent introduction of novel pathogens into naïve wild populations.

Antiretroviral Penetration and Drug Transporter Concentrations in the Spleens of Three Preclinical Animal Models and Humans.

Adequate antiretroviral (ARV) concentrations in lymphoid tissues are critical for optimal antiretroviral therapy (ART). While the spleen contains 25% of the body's lymphocytes, there are minimal data on ARV penetration in this organ. This study quantified total and protein-unbound splenic ARV concentrations and determined whether drug transporters, sex, or infection status were modifiers of these concentrations in animal models and humans. Two humanized mice models (hu-HSC-Rag [n = 36; 18 HIV-positive (HIV+) and 18 HIV-negative (HIV-)] and bone marrow-liver-thymus [n = 13; 7 HIV+ and 6 HIV-]) and one nonhuman primate (NHP) model (rhesus macaque [n = 18; 10 SHIV+ and 8 SHIV-]) were dosed to steady state with ARV combinations. HIV+ human spleens (n = 14) from the National NeuroAIDS Tissue Consortium were analyzed postmortem (up to 24 h postdose). ARV concentrations were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), drug transporter concentrations were measured with LC-MS proteomics, and protein binding in NHP spleens was determined by rapid equilibrium dialysis. Mice generally had the lowest splenic concentrations of the three species. Protein binding in splenic tissue was 6 to 96%, compared to 76 to 99% in blood plasma. NHPs had quantifiable Mrp4, Bcrp, and Ent1 concentrations, and humans had quantifiable ENT1 concentrations. None significantly correlated with tissue ARV concentrations. There was also no observable influence of infection status or sex. With these dosing strategies, NHP splenic penetration most closely resembled that of humans. These data can inform tissue pharmacokinetic scaling to humans to target HIV reservoirs by identifying important species-related differences.

Turtles and Tortoises Are in Trouble.

Turtles and tortoises (chelonians) have been integral components of global ecosystems for about 220 million years and have played important roles in human culture for at least 400,000 years. The chelonian shell is a remarkable evolutionary adaptation, facilitating success in terrestrial, freshwater and marine ecosystems. Today, more than half of the 360 living species and 482 total taxa (species and subspecies combined) are threatened with extinction. This places chelonians among the groups with the highest extinction risk of any sizeable vertebrate group. Turtle populations are declining rapidly due to habitat loss, consumption by humans for food and traditional medicines and collection for the international pet trade. Many taxa could become extinct in this century. Here, we examine survival threats to turtles and tortoises and discuss the interventions that will be needed to prevent widespread extinction in this group in coming decades.

Last exit before the brink: Conservation genomics of the Cambodian population of the critically endangered southern river terrapin.

The southern river terrapin, Batagur affinis is one of the world's 25 most endangered freshwater turtle species. The major portion of the global population is currently found in peninsular Malaysia, with the only remnant Indochinese population in southern Cambodia. For more than a decade, wild nests in this remnant Cambodian population have been fenced and hatchlings reared in captivity. Here we amplified 10 microsatellite markers from all 136 captive individuals, obtained 2,658 presumably unlinked and neutral single nucleotide polymorphisms from 72 samples with ddRAD-seq, and amplified 784 bp of mtDNA from 50 samples. Our results reveal that the last Indochinese population comprised only four kinship groups as of 2012, with all offspring sired from <10 individuals in the wild. We demonstrate an obvious decrease in genetic contributions of breeders in the wild from 2006-2012 and identify high-value breeders instrumental for ex-situ management of the contemporary genetic stock of the species.

DISEASE SCREENING IN SOUTHERN RIVER TERRAPINS ( BATAGUR AFFINIS EDWARDMOLLI) IN CAMBODIA.

Southern River terrapins ( Batagur affinis) are among the most critically endangered turtles in the world. To augment the Cambodia population, a head-start program was established for the endemic subspecies Batagur affinis edwardmolli in 2006, and in 2015, prerelease health assessments were performed on 70 subadults (hatch years, 2006-2011). Combined choanal/cloacal swab samples ( n = 70) were collected and screened by polymerase chain reaction (PCR) for Mycoplasma, herpesvirus, and ranavirus. Cloacal samples ( n = 50) were also collected and cultured for Salmonella sp. Of 70 tested samples, six (8.6%) were positive for Mycoplasma, and all other PCR and culture test results were negative. Phylogenetic analysis of the 16S ribosomal RNA gene placed the Mycoplasma sp. from B. affinis edwardmolli in the chelonian Mycoplasma cluster that groups within the Mycoplasma pulmonis clade. This mollicute was not associated with clinical disease (defined as observable clinical abnormalities, such as depression, lethargy, respiratory signs, and anorexia) and is likely part of the endemic microbial flora of these terrapins.