Bridging dolutegravir clinical viral response across doses and formulations using model-based exposure-response analysis in pediatrics.

OBJECTIVE: Dolutegravir (DTG) is a once-daily HIV-1 integrase inhibitor approved for the treatment of HIV-1 infection in adults and children from 4 weeks of age. The posology of DTG in children has been driven by exposure-matching relative to the adult dose for efficacy and safety. However, higher variability in pediatric exposures raises concern that efficacy may not be reliably extrapolated from adult trials. Therefore, we evaluated the relationship between DTG exposure and virologic response in children. DESIGN/METHODS: A population exposure-response analysis using logistic regression for virologic response was undertaken based on DTG exposure and covariate data from 146 pediatric participants with HIV-1 from age at least 4 weeks to less than 18 years treated for up to 48 weeks with DTG in IMPAACT P1093 study. RESULTS: None of the DTG exposure metrics were predictive of virologic response over the range of exposures in this analysis. Of the covariates tested, viral load at least 100 000 copies/ml at enrolment was a significant predictor of virologic response showing a lower probability of achieving a virologic response of HIV-1 RNA less than 50 copies/ml compared with participants with viral load less than 100 000 copies/ml at enrolment. Baseline viral load was also a significant predictor at week 48 whereby the probability of achieving a virologic response at week 48 decreased with increasing baseline viral load. CONCLUSION: This exposure-response analysis suggests that DTG exposures in children are all above the plateau of the exposure-response relationship. These results suggest that matching pediatric pharmacokinetic exposure parameters to those in adults is a reasonable approach for dose determination of DTG-containing formulations in pediatrics.

Pharmacokinetics, safety, tolerability, and antiviral activity of dolutegravir dispersible tablets in infants and children with HIV-1 (IMPAACT P1093): results of an open-label, phase 1-2 trial.

BACKGROUND: Safe and potent antiretroviral medications in child-friendly formulations are needed to treat young children living with HIV-1. We aimed to select dosing for a dispersible tablet formulation of dolutegravir that achieved pharmacokinetic exposures similar to those in adults, and was safe and well tolerated in young children. METHODS: International Maternal Pediatric Adolescent AIDS Clinical Trial (IMPAACT) P1093 is a phase 1-2 ongoing multicentre, open-label, non-comparative study of dolutegravir. A 5 mg dispersible tablet formulation of dolutegravir was studied in children aged 4 weeks to less than 6 years old, weighing at least 3 kg, with HIV RNA of greater than 1000 copies per mL and no previous treatment with integrase strand transfer inhibitor recruited from IMPAACT clinical research sites in Africa, the Americas, and Asia. Doses were selected on the basis of intensive pharmacokinetic evaluation on days 5-10, with safety and tolerability assessed up to 48 weeks. The primary objectives of this study are to evaluate the pharmacokinetics of dolutegravir in combination with optimised background therapy and to establish the dose of dolutegravir that achieves the targeted 24-h trough concentration and 24-h area under the curve for infants, children, and adolescents with HIV-1, to establish the safety and tolerability of dolutegravir at 24 and 48 weeks, and to select a dose that achieves similar exposure to the dolutegravir 50 mg once daily dose in adults. This analysis included participants treated with the proposed dose of dolutegravir dispersible tablets in two stages for each of three age cohorts. This trial is registered at ClinicalTrials.gov (NCT01302847) and is ongoing. FINDINGS: We recruited 181 participants from April 20, 2011, to Feb 19, 2020; of these, 96 received dolutegravir dispersible tablets. This analysis included 73 (35, 48% female) participants who received the final proposed dose with median (range) age of 1 year (0·1 to 6·0), weight (minimum-maximum) of 8·5 kg (3·7 to 18·5), plasma HIV-1 RNA concentration of 4·2 log10 copies per mL (2·1 to 7·0), and CD4% of 24·0% (0·3 to 49·0); 64 (87·7%) were treatment-experienced. The selected dose within each age cohort (≥2 years to <6 years, ≥6 months to <2 years of age and ≥4 weeks to <6 months) achieved geometric mean trough (ng/mL) of 688, 1179, and 1446, and 24 h area-under-the-curve (h·mg/L) of 53, 74, and 65, respectively. No grade 3 or worse adverse events were attributed to dolutegravir. INTERPRETATION: In this study, the proposed once daily dosing of dolutegravir dispersible tablets provided drug exposures similar to those for adults, and was safe and well tolerated. These data support the use of dolutegravir dispersible tablets as first-line or second-line treatment for infants and children aged less than 6 years living with HIV-1. FUNDING: National Institute of Allergy and Infectious Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Mental Health, and ViiV Healthcare-GlaxoSmithKline.

Pharmacokinetics and Safety of 3 Months of Weekly Rifapentine and Isoniazid for Tuberculosis Prevention in Pregnant Women.

BACKGROUND: Pregnancy increases the risk of tuberculosis and its complications. A 3-month regimen of weekly isoniazid and rifapentine (3HP) is safe and effective for tuberculosis prevention in adults and children, including those with HIV, but 3HP has not been evaluated in pregnancy. METHODS: IMPAACT 2001 was a phase I/II trial evaluating the pharmacokinetics and safety of 3HP among pregnant women with indications for tuberculosis preventative therapy in Haiti, Kenya, Malawi, Thailand, and Zimbabwe (NCT02651259). Isoniazid and rifapentine were provided at standard doses (900 mg/week). Pharmacokinetic sampling was performed with the first (second/third trimester) and twelfth (third trimester/postpartum) doses. Nonlinear mixed-effects models were used to estimate drug population pharmacokinetics. RESULTS: Of 50 participants, 20 had HIV and were taking efavirenz-based antiretroviral therapy. Among women without HIV, clearance of rifapentine was 28% lower during pregnancy than postpartum (1.20 vs 1.53 L/hour, P < .001), with area under the concentration-time curve (AUCSS) of 786 and 673 mg × hour/L, respectively. In pregnant women with HIV, clearance was 30% higher than women without HIV (P < .001), resulting in lower AUCss (522 mg × hour/L); clearance did not change significantly between pregnancy and postpartum. Pregnancy did not impact isoniazid pharmacokinetics. There were no drug-related serious adverse events, treatment discontinuations, or tuberculosis cases in women or infants. CONCLUSIONS: 3HP does not require dose adjustment in pregnancy. Rifapentine clearance is higher among women with HIV, but all women achieved exposures of rifapentine and isoniazid associated with successful tuberculosis prevention. The data support proceeding with larger safety-focused studies of 3HP in pregnancy. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov, NCT02651259.

Impact of Low Birth Weight and Prematurity on Neonatal Raltegravir Pharmacokinetics: Impaact P1097.

BACKGROUND: HIV treatment of neonates requires identifying appropriate antiretroviral dosing regimens. Our aims were to characterize raltegravir elimination kinetics in low birth weight (LBW) neonates after maternal dosing and to develop a pharmacokinetic model to predict raltegravir plasma concentrations for term and preterm neonates. METHODS: Mothers living with HIV who received raltegravir during pregnancy and their LBW neonates participated in IMPAACT P1097 study. Up to 6 serial plasma samples were collected from each infant over the first 2 postnatal weeks to characterize raltegravir elimination. Safety laboratory evaluations were obtained, and infants were monitored for 6 weeks for signs of raltegravir toxicity. An integrated maternal-neonatal pharmacokinetic model was developed to predict neonatal raltegravir plasma concentrations. RESULTS: Sixteen mothers and their 18 LBW neonates were enrolled. The median (range) raltegravir elimination half-life was 24.4 (10.1-83) hours (N = 17 neonates). No adverse events related to raltegravir in utero exposure were observed. Pharmacokinetic modeling revealed that raltegravir clearance in full-term LBW neonates was well described by allometric scaling but clearance in preterm LBW neonates was better described using slower clearance maturation kinetics. Simulations suggest receipt of the current dosing recommendations in a 34-week gestation neonate would result in plasma concentrations up to 2.5-fold higher than those observed in full-term LBW infants. CONCLUSIONS: Modeling suggests that prematurity reduces raltegravir clearance and a modified raltegravir dosing regimen will be necessary to avoid elevated plasma raltegravir concentrations.

Raltegravir (RAL) in Neonates: Dosing, Pharmacokinetics (PK), and Safety in HIV-1-Exposed Neonates at Risk of Infection (IMPAACT P1110).

BACKGROUND: Adequate pharmacokinetic and safety data in neonates are lacking for most antiretroviral agents. Raltegravir is a selective HIV-1 integrase strand transfer inhibitor available in a granule formulation suitable for use in neonates and young infants as prophylaxis or treatment of HIV infection. METHODS: IMPAACT P1110 is a phase 1, multicenter, noncomparative dose-finding study of raltegravir in infants exposed to HIV-1 infection. A 2-cohort adaptive design was utilized where pharmacokinetic data from infants in cohort 1 who received 2 single doses of raltegravir 3 mg/kg were included in population modeling and simulations to guide selection of a daily dose for infants in cohort 2. RESULTS: A total of 52 infants enrolled in IMPAACT 1110: cohort 1 (N = 16) and cohort 2 (N = 36). Using simulations based on population PK modeling incorporating cohort 1 data, the following daily dosing regimen was selected for study: 1.5 mg/kg daily from birth through day 7; 3 mg/kg twice daily from days 8-28 of life; and 6 mg/kg twice daily after 4 weeks of age through 6 weeks of age. The geometric mean protocol exposure targets for AUC, Ctrough, and Cmax were met or slightly exceeded in all infants. The chosen neonatal raltegravir dosing regimen was safe and well tolerated in full-term neonates during treatment over the first 6 weeks of life and follow-up to age 24 weeks. CONCLUSIONS: Raltegravir can be safely administered to full-term infants using the daily dosing regimen studied. This regimen is not recommended for use in premature infants in a new version of P1110.

Interferon-induced transmembrane protein 1 regulates endothelial lumen formation during angiogenesis.

OBJECTIVE: It is well established that angiogenesis is a complex and coordinated multistep process. However, there remains a lack of information about the genes that regulate individual stages of vessel formation. Here, we aimed to define the role of human interferon-induced transmembrane protein 1 (IFITM1) during blood vessel formation. APPROACH AND RESULTS: We identified IFITM1 in a microarray screen for genes differentially regulated by endothelial cells (ECs) during an in vitro angiogenesis assay and found that IFITM1 expression was strongly induced as ECs sprouted and formed lumens. We showed by immunohistochemistry that human IFITM1 was expressed by stable blood vessels in multiple organs. siRNA-mediated knockdown of IFITM1 expression spared EC sprouting but completely disrupted lumen formation, in both in vitro and in an in vivo xeno-transplant model. ECs lacking IFITM1 underwent early stages of lumenogenesis (ie, intracellular vacuole formation) but failed to mature or expand lumens. Coimmunoprecipitation studies confirmed occludin as an IFITM1 binding partner in ECs, and immunocytochemistry showed a lack of occludin at endothelial tight junctions in the absence of IFITM1. Finally, time-lapse video microscopy revealed that IFITM1 is required for the formation of stable cell-cell contacts during endothelial lumen formation. CONCLUSIONS: IFITM1 is essential for the formation of functional blood vessels and stabilizes EC-EC interactions during endothelial lumen formation by regulating tight junction assembly.

Analysis of stromal cell secretomes reveals a critical role for stromal cell-derived hepatocyte growth factor and fibronectin in angiogenesis.

OBJECTIVE: Angiogenesis requires tightly coordinated crosstalk between endothelial cells (ECs) and stromal cells, such as fibroblasts and smooth muscle cells. The specific molecular mechanisms moderating this process are still poorly understood. METHODS AND RESULTS: Stromal cell-derived factors are essential for EC sprouting and lumen formation. We therefore compared the abilities of 2 primary fibroblast isolates and a primary smooth muscle cell isolate to promote in vitro angiogenesis, and analyzed their secretomes using a combination of nano liquid chromatography-mass spectrometry/mass spectrometry, quantitative PCR, and ELISA. Each isolate exhibited a different level of angiogenic ability. Using quantitative MS, we then compared the secretomes of a fibroblast isolate exhibiting low angiogenic activity, a fibroblast isolate exhibiting high angiogenic activity, and human umbilical vein ECs. High angiogenic fibroblast supernatants exhibited an overabundance of proteins associated with extracellular matrix constituents compared with low angiogenic fibroblasts or ECs. Finally, small interfering RNA technology and purified protein were used to confirm a role for stromal cell-derived hepatocyte growth factor and fibronectin in inducing EC sprouting. CONCLUSIONS: Differences in stromal cell ability to induce angiogenesis are a result of differences in the secreted proteomes of both extracellular matrix proteins and proangiogenic growth factors.

Rapid anastomosis of endothelial progenitor cell-derived vessels with host vasculature is promoted by a high density of cotransplanted fibroblasts.

To ensure survival of engineered implantable tissues thicker than approximately 2-3 mm, convection of nutrients and waste products to enhance the rate of transport will be required. Creating a network of vessels in vitro, before implantation (prevascularization), is one potential strategy to achieve this aim. In this study, we developed three-dimensional engineered vessel networks in vitro by coculture of endothelial cells (ECs) and fibroblasts in a fibrin gel for 7 days. Vessels formed by cord blood endothelial progenitor cell-derived ECs (EPC-ECs) in the presence of a high density of fibroblasts created an interconnected tubular network within 4 days, compared with 5-7 days in the presence of a low density of fibroblasts. Vessels derived from human umbilical vein ECs (HUVECs) in vitro showed similar kinetics. Implantation of the prevascularized tissues into immune-compromised mice, however, revealed a dramatic difference in the ability of EPC-ECs and HUVECs to form anastomoses with the host vasculature. Vascular beds derived from EPC-ECs were perfused within 1 day of implantation, whereas no HUVEC vessels were perfused at day 1. Further, while almost 90% of EPC-EC-derived vascular beds were perfused at day 3, only one-third of HUVEC-derived vascular beds were perfused. In both cases, a high density of fibroblasts accelerated anastomosis by 2-3 days. We conclude that both EPC-ECs and a high density of fibroblasts significantly accelerate the rate of functional anastomosis, and that prevascularizing an engineered tissue may be an effective strategy to enhance convective transport of nutrients in vivo.