Edmund V. Capparelli

Objectives: To develop a population pharmacokinetic (popPK) model to understand factors affecting the broadly neutralizing HIV antibody (bNAb) VR07-523LS disposition and infant predicted serum neutralization 80% inhibitory dilution titre ratio (PT80) and its potential relationship to antiviral effects. Methods: PK data from two studies were used: infants exposed to HIV initiating therapy ≤5 days of age (IMPAACT P1112, n = 21) and healthy adults (VRC605, n = 25). The infant study implemented fixed subcutaneous (s.c.) dosing whereas the adult study implemented weight-based dosing, via both intravenous (i.v.) and s.c. routes. Monte Carlo simulation assessed two doses (80 mg followed by 100 mg at 12 weeks) to determine the maintenance of levels >10 µg/mL in virtual infants. The broadly neutralizing antibodies (bNAbs) concentration/IC80 ratio (PT80) was calculated on the basis of simulated concentrations from the popPK model and VRC07-523LS HIV-1 sensitivity (IC80) distribution. Results: This model predicts typical infant CL/F and t1/2 of 159 mL/day/70 kg and 39 days. Comparatively, predicted adult typical CL/F and t1/2 were 269 mL/day/70 kg and 31 days. Concentrations were >10 µg/mL in >87% of virtual infants at 12 weeks following one dose and >98% at 24 weeks following two doses. Median (90% predictive interval) PT80 was 163 (71–383), 116 (51–274) and 61 (26–144) at 6, 8 and 12 weeks, respectively. Significant model covariates included age (infant versus adult) and multiple dosing. Conclusions: Age and repeat dosing influence VRC07-523LS PK. An 80-mg dose followed by 100 mg at 12 weeks rapidly achieves and maintains concentrations >10 µg/mL for >24 weeks. This dosing strategy is expected to result in antiviral effects in patients with sensitive viruses and supports further evaluation of VRC07-523LS.

BACKGROUND: HIV-1–specific broadly neutralizing monoclonal antibodies (bNAbs) have emerged as promising interventions with the potential to effectively treat and prevent HIV-1 infections. We conducted a phase I clinical trial evaluating the potent CD4-binding site–specific (CD4bs-specific) bNAbs VRC01LS and VRC07-523LS in people with HIV-1 (PWH) not receiving antiretroviral therapy (ART). METHODS: Participants received a single intravenous 40 mg/kg dose of either VRC01LS ( n = 7) or VRC07-523LS ( n = 9) and did not initiate ART for a minimum of 14 days. The primary study objective was to evaluate safety and tolerability; the secondary study objectives were to evaluate pharmacokinetics (PK) and the impact of administered bNAbs on viral loads (VL) and CD4 ⁺ T cell counts in the absence of ART. RESULTS: This trial enrolled 16 PWH aged 20 to 57 years. Both bNAbs were safe and well tolerated. Mild local reactogenicity was only reported in participants who received VRC07-523LS, while both bNAbs were associated with mild systemic symptoms. Maximum serum concentrations (C _max ) following VRC01LS or VRC07-523LS were 1,566 ± 316 and 1,295 ± 376 μg/mL, respectively. VRC07-523LS administration significantly decreased VL in 8 out of 9 participants, with an average decline of 1.7 ± 0.8 log ₁₀ copies/mL within 14 days after administration. In contrast, VRC01LS administration resulted in a smaller average decline (0.8 ± 0.8 log ₁₀ copies/mL), and 3 out of 7 participants showedno change in VL. Postinfusion maximum decline in VL correlated with post hoc baseline in vitro viral susceptibility results for both bNAbs. CONCLUSION: The results of this trial support inclusion of potent CD4bs-specific bNAbs, such as VRC07-523LS, into next-generation treatment regimens for HIV-1. TRIAL REGISTRATION: ClinicalTrials.gov NCT02840474. FUNDING: National Institute of Allergy and Infectious Diseases (NIAID)/NIH (grants UM1 AI068634, UM1 AI068636, UM1 AI106701, UM1AI069424, UM1AI069501, UM1AI69415, UM1AI069534, UM1AI69494); the Intramural Research Program of the NIAID/NIH; National Center for Advancing Translational Sciences/NIH (grants UM1TR004548, UL1TR001881, and UL1TR001878); and the National Cancer Institute/NIH (contract 75N91019D00024).

BACKGROUND: Broadly neutralizing monoclonal antibodies (bNAbs) represent a promising strategy for HIV-1 immunoprophylaxis and treatment. 10E8VLS and VRC07-523LS are bNAbs that target the highly conserved membrane-proximal external region (MPER) and the CD4-binding site of the HIV-1 viral envelope glycoprotein, respectively. METHODS: In this phase 1, open-label trial, we evaluated the safety and pharmacokinetics of 5 mg/kg 10E8VLS administered alone, or concurrently with 5 mg/kg VRC07-523LS, via s.c. injection to healthy non–HIV-infected individuals. RESULTS: Eight participants received either 10E8VLS alone ( n = 6) or 10E8VLS and VRC07-523LS in combination ( n = 2). Five ( n = 5 of 8, 62.5%) participants who received 10E8VLS experienced moderate local reactogenicity, and 1 participant ( n = 1/8, 12.5%) experienced severe local reactogenicity. Further trial enrollment was stopped, and no participant received repeat dosing. All local reactogenicity resolved without sequelae. 10E8VLS retained its neutralizing capacity, and no functional anti-drug antibodies were detected; however, a serum t _1/2 of 8.1 days was shorter than expected. Therefore, the trial was voluntarily stopped per sponsor decision (Vaccine Research Center, National Institute of Allergy and Infectious Diseases [NIAID], NIH). Mechanistic studies performed to investigate the underlying reason for the reactogenicity suggest that multiple mechanisms may have contributed, including antibody aggregation and upregulation of local inflammatory markers. CONCLUSION: 10E8VLS resulted in unexpected reactogenicity and a shorter t _1/2 in comparison with previously tested bNAbs. These studies may facilitate identification of nonreactogenic second-generation MPER-targeting bNAbs, which could be an effective strategy for HIV-1 immunoprophylaxis and treatment. TRIAL REGISTRATION: Clinicaltrials.gov, accession no. NCT03565315. FUNDING: Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH.

Clofazimine (CFZ) is a weakly basic, small-molecule antibiotic used for the treatment of mycobacterial infections including leprosy and multidrug-resistant tuberculosis. Upon prolonged oral administration, CFZ precipitates and accumulates within macrophages throughout the host. To model the pharmacokinetics of CFZ, the volume of distribution (Vd) was considered as a varying parameter that increases with continuous drug loading. Fitting the time-dependent change in drug mass and concentration data obtained from CFZ-treated mice, we performed a quantitative analysis of the systemic disposition of the drug over a 20-week treatment period. The pharmacokinetics data were fitted using various classical compartmental models sampling serum and spleen concentration data into separate matrices. The models were constructed in NONMEM together with linear and nonlinear sigmoidal expansion functions to the spleen compartment to capture the phase transition in Vd. The different modeling approaches were compared by Akaike information criteria, observed and predicted concentration correlations, and graphically. Using the composite analysis of the modeling predictions, adaptive fractional CFZ sequestration, Vd and half-life were evaluated. When compared to standard compartmental models, an adaptive Vd model yielded a more accurate data fit of the drug concentrations in both the serum and spleen. Including a nonlinear sigmoidal equation into compartmental models captures the phase transition of drugs such as CFZ, greatly improving the prediction of population pharmacokinetics and yielding further insight into the mechanisms of drug disposition.

Clofazimine (CFZ) is a poorly soluble, weakly basic, small molecule antibiotic clinically used to treat leprosy and is now in clinical trials as a treatment for multidrug resistant tuberculosis and COVID-19. CFZ exhibits complex, context-dependent pharmacokinetics that are characterized by an increasing half-life in long term treatment regimens. The systemic pharmacokinetics of CFZ have been previously represented by a nonlinear, 2-compartment model incorporating an expanding volume of distribution. This expansion reflects the soluble-to-insoluble phase transition that the drug undergoes as it precipitates out and accumulates within macrophages disseminated throughout the organism. Using mice as a model organism, we studied the mechanistic underpinnings of this increasing half-life and how the systemic pharmacokinetics of CFZ are altered with continued dosing. To this end, M. tuberculosis infection status and multiple dosing schemes were studied alongside a parameter sensitivity analysis (PSA) to further understanding of systemic drug distribution. Parameter values governing the sigmoidal expansion function that captures the phase transition were methodically varied, and in turn, the systemic concentrations of the drug were calculated and compared to the experimentally measured concentrations of drug in serum and spleen. The resulting amounts of drug sequestered were dependent on the total mass of CFZ administered and the duration of drug loading. This phenomenon can be captured by altering three different parameters of an expansion function corresponding to key biological determinants responsible for the precipitation and the accumulation of the insoluble drug mass in macrophages. Through this analysis of the context dependent pharmacokinetics of CFZ, a predictive framework for projecting the systemic distribution and self-assembly of precipitated drug complexes as intracellular mechanopharmaceutical devices of this and other drugs exhibiting similarly complex pharmacokinetics can be constructed.

Objective: Dosing efavirenz (EFV) in children less than 3 years of age is challenging due to large variability in drug levels. This study evaluated differences in pharmacokinetics with tuberculosis (TB) therapy, formulation, age, and CYP2B6 genotype. Design: Pharmacokinetic data from three IMPAACT/PACTG studies (P382, P1021, and P1070) for children initiating therapy less than 40 months of age were evaluated. Methods: Pharmacokinetic data were combined in a population pharmacokinetic model. Exposure from the 2-week pharmacokinetic visit was compared with changes in viral RNA between the Week 0 and Week 4 visits. Results: The model included 103 participants (19 on TB therapy). CYP2B6 516 genotype information was available for 82 participants (TT: 15, GT: 28, GG: 39). Median age at the first pharmacokinetic visit was 17.0 months (range: 2.0–39.0 months). Liquid formulation led to a 42% decrease in bioavailability compared with opened capsules. TB therapy (isoniazid and rifampin) led to a 29% decreased clearance, however Monte Carlo simulations demonstrated the majority of participants on TB therapy receiving standard EFV dosing to be in the target area under the curve range. Clearance was 5.3-fold higher for GG than TT genotype and 3.3-fold higher for GT than TT genotype. Age did not have a significant effect on clearance in the final model. Initial viral RNA decay was lower for patients in the lowest quartile of exposures (area under the curves) than for higher quartiles (P = 0.013). Conclusion: EFV dosing should account for CYP2B6 516 genotype and formulation, but does not require adjustment for concurrent TB therapy.

Background: Antiretroviral options for neonates (younger than 28 days) should be expanded. We evaluated the pharmacokinetics, safety, and acceptability of the "4-in-1" fixed-dose pediatric granule formulation of abacavir/lamivudine/lopinavir/ritonavir (30/15/40/10 mg) in neonates. Methods: The PETITE study is an ongoing phase I/II, open-label, single-arm, 2-stage trial conducted in South Africa. In stage 1, term neonates exposed to HIV on standard antiretroviral prophylaxis (nevirapine ± zidovudine) received single dose(s) of the 4-in-1 formulation, followed by intensive pharmacokinetic sampling and safety assessments. At each PK visit, blood was drawn after an observed dose at 1, 2, 4, 8, and 12 hours postdose. In this study, we have reported the planned interim pharmacokinetic and safety analysis after completion of the single-dose administration. Results: Sixteen neonates, with a median (range) birth weight of 3130 g (2790–3590 g), completed 24 pharmacokinetic visits. The 4-in-1 formulation imposed relatively high doses of abacavir [8.6 mg/kg (6.6–11.4)] and lamivudine [4.3 mg/kg (3.3–5.7)] but lower doses of lopinavir [11.5 mg/kg (8.8–15.2)]. The geometric means (GM, 90% CI) AUC_0–12 of abacavir, lamivudine, and lopinavir were 29.87 (26.29–33.93), 12.61 (10.72–14.83), and 3.49 (2.13–5.72) µg.h/mL, respectively. Lopinavir GM AUC_0–12 was below the predefined target (20–100 µg.h/mL), and ritonavir concentrations were only detectable in 4 of the 120 (3%) samples. No adverse events were related to study drugs. No neonate had difficulty swallowing the 4-in-1 formulation. Conclusions: The high doses of abacavir and lamivudine (in mg/kg) and AUCs were safe, and the formulation was well tolerated; however, lopinavir/ritonavir exposures were extremely low, preventing its use in neonates use in neonates. Alternative pediatric solid antiretroviral formulations must be studied in neonates.

VRC01 is a first‐in‐class, potent, broadly neutralizing antibody that targets the CD4 binding site of gp120 on HIV‐1 viruses, and is under development as a novel HIV therapeutic. This study utilized population pharmacokinetic (PK) modeling to characterize VRC01 PK to guide dosing selection for ongoing phase II clinical trials in pediatric patients. Combining VRC01 PK data from 3 adult and 1 infant clinical trials, a total of 1,475 VRC01 serum concentrations from 100 participants were used in the analysis (40 infants and 60 adults). VRC01 was administered either i.v. or s.c. (1–40 mg/kg). All infants received s.c. doses as compared with 13% s.c. and 87% i.v. in adults. The data were well‐described by a two‐compartment model. Clearance was 37% higher in adults with HIV infection and 83% lower in infants than adults. Subcutaneous bioavailability was 55% in adults. Rapid absorption was seen in infants indicating therapeutic levels could be achieved quickly. Monte Carlo simulations were used to determine optimal dosing and demonstrated 40 mg/kg s.c. at weeks 0, 2, 6, and 10 would maintain VRC01 levels at the suppressive target concentration of 50 μg/mL for the first 14 weeks of life in infants. The current analysis provides new insight into differences in monoclonal antibody PK between infants and adults and demonstrates the utility of a population PK approach in informing drug development for infant populations.

High-dose methotrexate (HD-MTX) is widely used in pediatric and adult oncology treatment regimens. This study aimed to develop a population pharmacokinetic model to characterize pediatric and adult MTX exposure across various disease types and dosing regimens, and to evaluate exposure–toxicity relationships.

Medication adherence is critical to the effectiveness of benznidazole (BZ) therapy for the treatment of Chagas disease. Assessing BZ adherence using traditional plasma sampling methods presents numerous challenges in resource-limited settings. Dried blood spot (DBS) sampling of BZ can be used to overcome logistical barriers and provides a less invasive method for assessing BZ levels. A BZ DBS assay using liquid chromatography-tandem mass spectrometry was developed and applied to a clinical study of infants and children being treated with BZ for Trypanosoma cruzi infection in Argentina. The assay was validated over a concentration range of 9.8–5,000 ng/mL. Inter-assay and intra-assay measures ranged from −2.9% to 2.7% and 0.5% to 8.3% for accuracy and from 3.5% to 12% and 1.6% to 13.6% for precision, respectively. The mean recovery of BZ was greater than 91%. Partitioning ratios for DBSs/plasma ranged from 0.95 to 1.02. A cohort of 10 infants and six children with T. cruzi infection being treated with BZ had median BZ concentrations of 1.2 (IQR 0.29, 2.14) µg/mL with seven of 65 (11%) samples above the BZ treatment goal of 3 μg/mL for adults. The reported DBS assay is a simple and accurate method for the quantitative measurement of BZ that can be applied to facilitate urgently needed clinical studies of BZ for the treatment of Chagas disease and assess BZ adherence in resource-limited settings.