Population pharmacokinetics of the rilpivirine long-acting formulation after intramuscular dosing in healthy subjects and people living with HIV.

OBJECTIVES: To characterize the population pharmacokinetics of the rilpivirine long-acting (LA) formulation after intramuscular administration. METHODS: Rich and sparse rilpivirine plasma concentration data were obtained from seven clinical studies. In total, 18 261 rilpivirine samples were collected from 986 subjects (131 healthy subjects from Phase I studies and 855 people living with HIV from Phase IIb/III studies). Doses ranged from 300 to 1200 mg, as single-dose or multiple-dose regimens (every 4 or 8 weeks). In Phase III studies, an initiation injection of 900 mg followed by continuation injections of 600 mg every 4 weeks was used. Non-linear mixed-effects modelling was performed using NONMEM® software. RESULTS: A one-compartment model with linear elimination and two parallel absorption pathways (fast and slow) with sequential zero-first-order processes adequately captured rilpivirine flip-flop pharmacokinetics after intramuscular administration of the LA formulation. The estimated apparent elimination half-life of rilpivirine LA was 200 days. None of the evaluated covariates (age, body weight, BMI, sex, race, health status and needle length) had a clinically relevant impact on rilpivirine pharmacokinetics. CONCLUSIONS: The population pharmacokinetic model suitably describes the time course and associated variability of rilpivirine plasma concentrations after rilpivirine LA intramuscular administration. The monthly regimen consists of an oral lead-in period (rilpivirine 25 mg tablets once daily for 4 weeks), followed by an initiation injection of 900 mg rilpivirine LA, then 600 mg rilpivirine LA continuation injections monthly. The absence of a clinically relevant effect of covariates on rilpivirine pharmacokinetics suggests that rilpivirine LA dose adjustments for specific subgroups are not warranted.

Reduced exposure to darunavir and cobicistat in HIV-1-infected pregnant women receiving a darunavir/cobicistat-based regimen.

OBJECTIVES: The aim of the study was to evaluate darunavir and cobicistat pharmacokinetics in pregnant women with HIV-1 infection. METHODS: This phase 3b, open-label study enrolled HIV-1-infected pregnant women (18-26 weeks of gestation) receiving combination antiretroviral therapy with once-daily darunavir/cobicistat 800/150 mg. The plasma pharmacokinetics of darunavir (total and unbound) and cobicistat were assessed over 24 h during the second and third trimesters (24-28 and 34-38 weeks of gestation, respectively) and 6-12 weeks postpartum. Pharmacokinetic parameters [area under the plasma concentration-time curve over 24 h (AUC24 h ), maximum plasma concentration (Cmax ) and minimum plasma concentration (Cmin )] were derived using noncompartmental analysis and compared using linear mixed effects modelling (pregnancy versus postpartum). Antiviral activity and safety were evaluated. RESULTS: Seven women were enrolled in the study; six completed it. Total darunavir exposure was lower during pregnancy than postpartum (AUC24 h , 50-56% lower; Cmax , 37-49% lower; Cmin , 89-92% lower); unbound darunavir exposure was also reduced (AUC24 h , 40-45% lower; Cmax , 32-41% lower; Cmin , 88-92% lower). Cobicistat exposure was also lower during pregnancy than postpartum (AUC24 h , 49-63% lower; Cmax , 27-50% lower; Cmin , 83% lower). At study completion, five of six (83%) women were virologically suppressed (HIV-1 RNA < 50 copies/mL). There was one virological failure (the patient was nonadherent; no emerging genotypic resistance was observed and susceptibility to antiretrovirals was maintained). No mother-to-child transmission was detected among six infants born to the six women who completed the study. Overall, darunavir/cobicistat was well tolerated in women and infants. CONCLUSIONS: In view of markedly reduced darunavir and cobicistat exposures during pregnancy, this combination is not recommended in HIV-1-infected pregnant women.

Pharmacokinetics of once-daily darunavir/ritonavir in HIV-1-infected pregnant women.

OBJECTIVES: HIV antiretroviral therapy during pregnancy is recommended to reduce the risk of mother-to-child transmission and for maternal care. Physiological changes during pregnancy can affect pharmacokinetics. The impact of pregnancy was evaluated for once-daily (qd) darunavir/ritonavir. METHODS: HIV-1-infected pregnant women on an antiretroviral regimen that includes darunavir were enrolled in the study and further treated with darunavir/ritonavir 800/100 mg qd. Plasma concentrations were assessed over 24 h during the second and third trimesters and postpartum using a validated high-performance liquid chromatography tandem mass spectrometry assay for total darunavir and ritonavir, and using (14) C-darunavir-fortified plasma for unbound darunavir. Pharmacokinetic parameters were derived using noncompartmental analysis. Safety and antiviral response were assessed at all visits. RESULTS: Data were available for 16 women. The area under the plasma concentration-time curve from 0 to 24 h (AUC24h ) for total darunavir was 34-35% lower during pregnancy vs. postpartum. Unbound darunavir AUC24h was 20-24% lower during pregnancy vs. postpartum. The minimum plasma concentration of total and unbound darunavir was 32-50% and 13-38% lower, respectively, during pregnancy vs. postpartum. The antiviral response (< 50 HIV-1 RNA copies/mL) was 59% at baseline and increased to 87-100% during the trial; the CD4 count increased over time. One serious adverse event (gestational diabetes) was judged as possibly related to study medication. All 16 infants born to women remaining in the study at delivery were HIV-1 negative (two were premature). CONCLUSIONS: Total darunavir exposure decreased during pregnancy, but the decrease was less for unbound (active) darunavir. These changes are not considered clinically relevant. Darunavir/ritonavir 800/100 mg qd may therefore be a treatment option for HIV-1-infected pregnant women.

Safety, tolerability and pharmacokinetics of rilpivirine following administration of a long-acting formulation in healthy volunteers.

OBJECTIVES: This phase I healthy volunteer study (NCT01031589) was carried out to investigate the safety/tolerability and pharmacokinetics of a rilpivirine (RPV; TMC278) long-acting (LA) formulation after single and multiple intramuscular (i.m.) injections. METHODS: In the first part of the study, which had an open-label design, a single RPV LA i.m. injection (300 mg/mL) of 300 (n = 6) or 600 (n = 5) mg was given to the volunteers. In the second part of the study, which had a double-blind, randomized, placebo-controlled design, three RPV LA i.m. injections (one every 4 weeks) at 1200/600/600 mg (n = 6) or placebo (n = 2) were given. Safety and local tolerability were monitored. RPV plasma concentrations were analysed up to 28 days after injection or until they were < 20 ng/mL. RESULTS: Grade 1/2 RPV-related adverse events in the 300, 600 and 1200/600/600 mg groups were: rash (zero, one and one subject, respectively, the last of whom discontinued participation in the study); musculoskeletal stiffness (three, zero and zero subjects, respectively); injection site reactions (one, two and two subjects, respectively). After one injection of 300, 600 or 1200 mg RPV LA, the mean (standard deviation) maximum plasma concentration was 39 (25), 48 (13) and 140 (16) ng/mL, and the mean (standard deviation) area under the concentration-time curve (28 days) was 17,090 (8907), 25,240 (8184) and 55,350 (13,550) ng h/mL, respectively. RPV pharmacokinetics were largely comparable after the 1200 mg loading dose and both 600 mg injections of RPV LA. The mean (standard deviation) RPV plasma concentration across the 28-day dosing interval after the last injection in the 1200/600/600 mg group was 79 (19) ng/mL. CONCLUSIONS: Single and multiple i.m. injections of RPV LA demonstrated favourable local/systemic tolerability in healthy volunteers. RPV pharmacokinetics suggested that clinically relevant plasma concentrations can be achieved with this LA formulation.

Effect of gender and race on the week 48 findings in treatment-naïve, HIV-1-infected patients enrolled in the randomized, phase III trials ECHO and THRIVE.

OBJECTIVES: A week 48 efficacy and safety analysis with respect to gender and race was conducted using pooled data from the phase III, double-blind, double-dummy efficacy comparison in treatment-naïve, HIV-infected subjects of TMC278 and efavirenz (ECHO) and TMC278 against HIV, in a once-daily regimen versus efavirenz (THRIVE) trials. METHODS: Treatment-naïve, HIV-1-infected adults were randomized to receive rilpivirine (RPV; TMC278) 25 mg once a day (qd), or efavirenz (EFV) 600 mg qd, plus tenofovir/emtricitabine (ECHO) or tenofovir/emtricitabine, zidovudine/lamivudine or abacavir/lamivudine (THRIVE). RESULTS: A total of 1368 participants (76% male and 61% White, of those with available race data) were randomized and treated. No gender-related differences in response rate (percentage of patients with HIV-1 viral load < 50 HIV-1 RNA copies/mL, using an intent-to-treat, time-to-loss-of-virological-response algorithm) were observed (RPV: men, 85%; women, 83%; EFV: men, 82%; women, 83%). Response rates were lower in Black compared with Asian and White participants (RPV: 75% vs. 95% and 85%, respectively; EFV: 74% vs. 93% and 83%, respectively); this finding was mostly a result of higher discontinuation and virological failure rates in Black patients. Safety findings were generally similar across race and gender subgroups. However, nausea occurred more commonly in women than in men in both treatment groups. In men, diarrhoea was more frequent in the EFV group, and abnormal dreams/nightmares were more frequent in men in both the EFV and RPV groups. CONCLUSIONS: Overall response rates were high for both RPV and EFV. No gender differences were observed. However, response rates were lower among Black patients, regardless of treatment group. Gender appeared to influence the incidence of gastrointestinal adverse events and abnormal dreams/nightmares for both treatments.

The influence of hepatic impairment on the pharmacokinetics of paliperidone.

OBJECTIVES: This study assessed the impact of hepatic impairment on the pharmacokinetics (PK) of paliperidone and its enantiomers. METHODS: A single 1 mg dose of paliperidone immediate-release (IR) was administered to subjects with moderate hepatic impairment (n = 10) and demographically matched individuals with normal hepatic function (n = 10). RESULTS: Plasma protein binding was lower in hepatically impaired subjects resulting in a 27% higher unbound fraction of paliperidone compared with healthy individuals. After correcting for the difference in plasma protein binding, unbound exposures were comparable between groups. All other PK parameters were similar between the two groups. Paliperidone IR was equally well tolerated in both groups. CONCLUSIONS: The impact of moderate hepatic impairment on paliperidone PK is not considered clinically relevant as the PK profile of unbound paliperidone is similar for subjects with moderate hepatic impairment and those with normal hepatic function. Dosage adjustments of paliperidone are not required in subjects with mild or moderate hepatic impairment.

Heterogeneity in relaxation mechanisms in the carotid and the femoral artery of the mouse.

The participation of prostanoids, nitric oxide and non-prostanoid non-nitric oxide factors in endothelium-dependent relaxations was investigated in phenylephrine (PE)-constricted carotid and femoral arteries of C57BL6 mice. The carotid artery was more sensitive to acetylcholine as compared to the femoral artery, and cyclooxygenase inhibition did not influence the relaxation in either vessel. In the carotid artery, high doses of acetylcholine caused transient constrictions, which were abolished by indomethacin or piroxicam. In the carotid but not the femoral artery, N(omega)-nitro-L-arginine or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) enhanced PE-induced contractions enormously, suggesting that endogenous nitric oxide production is much higher in the carotid artery. While in the carotid artery all relaxation was abolished by N(omega)-nitro-L-arginine or ODQ, a residual response (34+/-5% and 74+/-4%, respectively) but with a different shape, was maintained in the femoral artery. This N(omega)-nitro-L-arginine-resistant relaxation was abolished by the combination of apamin and charybdotoxin. In both arteries, ODQ abolished relaxation to S-nitroso-N-acetyl-D-penicillamine, while N(omega)-nitro-L-arginine enhanced the sensitivity to this donor of exogenous nitric oxide. In 30 mM KCl, the relaxation to acetylcholine was abolished by N(omega)-nitro-L-arginine or ODQ in either artery. In conclusion, in the carotid artery endothelium-dependent relaxation is mediated predominantly by nitric oxide acting via cyclic GMP-dependent pathways, while in the femoral artery part of the relaxation can be attributed to a non-prostanoid non-nitric oxide factor operating via apamin/charybdotoxin-sensitive potassium channels.

Local application of advanced glycation end products and intimal hyperplasia in the rabbit collared carotid artery.

OBJECTIVE: Accumulation of advanced glycation end products (AGEs) in the vessel wall has been implicated in atherogenesis. The aim of our study was to examine the effects of local application of glycated bovine serum albumin (AGE-BSA) on collar-induced intimal hyperplasia in a diabetes-free setting. METHODS: Intimal thickening was induced by placing a collar around the carotid artery of rabbits. Via a catheter attached to an osmotic minipump, control BSA or AGE-BSA was administered locally to the vessel wall in a dose of 1.5 or 15 microg h(-1) during 14 days. Vessels receiving phosphate buffered saline (PBS, 5 microl h(-1)) were used as controls. RESULTS: Infusion of AGE-BSA 15 microg h(-1) significantly enhanced intimal thickening as compared to control BSA or PBS. Positive remodelling, measured as an increase in the area comprised by the external elastic lamina and preservation of lumen size, was only significant after treatment with the higher dose of AGE-BSA. In all other groups, intimal thickening was accompanied by a decrease of the lumen without outward displacement. Infusion of control BSA or AGE-BSA changed the cell composition of the neointima, with a significant enhancement in the number of T-lymphocytes and macrophages and a reduction in the percentage of intimal area occupied by smooth muscle cells. These effects were however similar for control BSA as well as AGE-BSA. CONCLUSIONS: It is concluded that infusion of control BSA or AGE-BSA may aggravate collar-induced intimal thickening by evoking an inflammatory response. This supports the concept that inflammation contributes to atherogenesis. Further, the significant enhancement in intimal hyperplasia by AGE-BSA suggests that glycated proteins provide an additional stimulus for the development of atherosclerotic lesions.