Lipophilic nalmefene prodrugs to achieve a one-month sustained release

Nalmefene is an opioid antagonist which as a once-a-day tablet formulation has recently been approved for reducing ethanol intake in alcoholic subjects. In order to address the compliance issue in this patient population, a number of potential nalmefene prodrugs were synthesized with the aim of providing a formulation that could provide plasma drug concentrations in the region of 0.5–1.0 ng/mL for a one-month period when dosed intramuscular to dogs or minipigs. In an initial series of studies, three different lipophilic nalmefene derivatives were evaluated: the palmitate (C16), the octadecyl glutarate diester (C18-C5) and the decyl carbamate (CB10). They were administered intramuscularly to dogs in a sesame oil solution at a dose of 1 mg-eq. nalmefene/kg. The decyl carbamate was released relatively quickly from the oil depot and its carbamate bond was too stable to be used as a prodrug. The other two derivatives delivered a fairly constant level of 0.2–0.3 ng nalmefene/mL plasma for one month and since there was no significant difference between these two, the less complex palmitate monoester was chosen to demonstrate that dog plasma nalmefene concentrations were dose-dependent at 1, 5 and 20 mg-eq. nalmefene/kg. In a second set of experiments, the effect of the chain length of the fatty acid monoester promoieties was examined. The increasingly lipophilic octanoate (C8), decanoate (C10) and dodecanoate (C12) derivatives were evaluated in dogs and in minipigs, at a dose of 5 mg-eq. nalmefene/kg and plasma nalmefene concentrations were measured over a four-week period. The pharmacokinetic profiles were very similar in both species with Cmax decreasing and Tmax increasing with increasing fatty acid chain length and the target plasma concentrations (0.5–1.0 ng/mL over a month-long period) were achieved with the dodecanoate (C12) prodrug. These data therefore demonstrate that sustained plasma nalmefene concentrations can be achieved in both dog and minipig using nalmefene prodrugs and that the pharmacokinetic profile of nalmefene can be tuned by varying the length of the alkyl group

Direct nose to brain delivery of small molecules: critical analysis of data from a standardized in vivo screening model in rats

The blood–brain barrier (BBB) is often a limiting factor for getting drugs in the brain. Bypassing the BBB by intranasal (IN), or also called nose to brain (NTB), route is an interesting and frequently investigated concept for brain drug delivery. However, despite the body of evidence for IN drug delivery in literature over the last decades, reproducibility and interpretation of animal data remain challenging. The objective of this project was to assess the feasibility and value of a standardized IN screening model in rats for the evaluation of direct brain delivery. A chemically diverse set of commercial and internal small molecules were tested in the in vivo model with different doses and/or formulations. Data were analyzed using different ways of ratio calculations: blood concentration at time of sacrifice, total exposure in blood (area under the curve, AUC) and the brain or olfactory bulb concentrations. The IN route was compared to another parenteral route to decide if there is potential direct brain transport. The results show that blood and tissue concentrations and ratios are highly variable and not always reproducible. Potential direct brain delivery was concluded for some compounds, however, sometimes depending on the analysis: using blood levels at sacrifice or AUC could lead to different conclusions. We conclude that a screening model for the evaluation of direct brain transport of small molecules is very difficult to achieve and a conclusion based on a limited number of animals with this variability is questionable

Pharmacokinetics and Disposition of Rilpivirine (TMC278) Nanosuspension as a Long-Acting Injectable Antiretroviral Formulation▿

The next-generation human immunodeficiency virus type 1 (HIV-1) nonnucleoside reverse transcriptase inhibitor rilpivirine (TMC278) was administered in rats and dogs as single intramuscular (IM) or subcutaneous (SC) injections, formulated as a 200-nm nanosuspension. The plasma pharmacokinetics, injection site concentrations, disposition to lymphoid tissues, and tolerability were evaluated in support of its potential use as a once-monthly antiretroviral agent in humans. Rilpivirine plasma concentration-time profiles showed sustained and dose-proportional release over 2 months in rats and over 6 months in dogs. The absolute bioavailability approached 100%, indicating a complete release from the depot, in spite of rilpivirine concentrations still being high at the injection site(s) 3 months after administration in dogs. For both species, IM administration was associated with higher initial peak plasma concentrations and a more rapid washout than SC administration, which resulted in a stable plasma-concentration profile over at least 6 weeks in dogs. The rilpivirine concentrations in the lymph nodes draining the IM injection site exceeded the plasma concentrations by over 100-fold 1 month after administration, while the concentrations in the lymphoid tissues decreased to 3- to 6-fold the plasma concentrations beyond 3 months. These observations suggest uptake of nanoparticles by macrophages, which generates secondary depots in these lymph nodes. Both SC and IM injections were generally well tolerated and safe, with observations of a transient inflammatory response at the injection site. The findings support clinical investigations of rilpivirine nanosuspension as a long-acting formulation to improve adherence during antiretroviral therapy and for preexposure prophylaxis

Dog model with implanted pump to test boosters for antiretroviral medication

A dog model was developed to test the capacity of boosters for antiretroviral medication. Two dogs were implanted with a modified constant-flow Codman 3000 infusion pump, adapted to release viscous solutions of darunavir (TMC114) at a constant rate of 25mg/dog/day in the venous blood stream. Booster candidates were given by oral gavage for at least 4 days up to maximum 7 days in cross-over fashion, separated by a wash-out period of minimum 1 week. The booster candidates were tested at doses of 20 and/or 40mg/kg/day: blood sampling for determination of the boosting effect was performed on the last day of booster administration. The model allowed to (1) compare the boosting ratio of these booster candidates based on the exposure (determination of the area under the curve (AUC) of darunavir in presence versus absence of the booster candidate), (2) detect delay in boosting activity by evaluation of the shift of Cmax of darunavir following booster administration versus the Cmax of the booster candidate) and (3) calculate the intrinsic booster capacity, by correcting for the systemic exposure of booster candidate by normalizing the booster ratio for the booster's AUC. The latter parameter (intrinsic booster capacity) allows to determine the booster's metabolic contribution in inhibiting the metabolism of antiretroviral medication (most likely via inhibition of CYP3A4), minimizing the impact of potential effects of the booster at the level of the gastro-intestinal tract.status: publishe

Development of an implantable infusion pump for sustained anti-HIV drug administration

Factors such as insufficient drug potency, non-compliance and restricted tissue penetration contribute to incomplete suppression of Human Immunodeficiency Virus (HIV) and the difficulty to control this infection. Infusion via standard catheters can be a source of infection, which is potentially life threatening in these patients. We developed an implantable infusion pump, allowing to accommodate large volumes (16-50mL) of high viscous solutions (up to 23.96mPas at 39 degrees C) of anti-HIV agents and providing sustained release of medication: a standard Codman 3000 pump, which was initially developed to release aqueous solutions ( approximately 0.7mPas) into the spinal cord such as for pain medication, was transformed for release of viscous solutions up to 40mPas by adapting the diameter of the capillary flow restrictor, the capillary length and way of catheterisation--by placing the indwelling catheter in the vena cava. A pilot study of the pump implanted in 2 dogs showed continuous steady-state release of the protease inhibitor darunavir (25mg/dog/day administered for 25 days), thereby achieving plasma concentration levels of approximately 40ng/mL. Steady-state plasma levels were reproducible after monthly refill of the pumps. In conclusion, the implantable adapted Codman 3000 constant-flow infusion pump customized to anti-HIV therapy allows sustained release of anti-HIV medication and may represent an opportunity to reduce the pill burden and complexity of dosing schemes associated with common anti-HIV therapy.status: publishe

CSF Aβ isoform patterns.

<p>Dogs treated with vehicle (N = 15), NB-C8 (N = 3 at 3 hours, N = 3 at 16 hours) and NB-B4 (N = 5 at 6 hours). Mass spectra of the Aβ isoform pattern from dogs treated with placebo (Panel a, upper panel) or NB-C8 16 hours post treatment (Panel a, lower panel). The expanded sections show Aβ1-33, Aβ1-34, Aβ5-38 and Aβ5-40. Aβ1-33 and Aβ5-38 were excluded from quantitative analysis since their peaks partially overlap, making quantification difficult. Absolute (Panels b–c) and normalized (Panels d–e) mass spectral peak intensities of all detected Aβ isoforms. Statistical significances were tested for normalized peak intensities comparing different treatments. For NB-B4, significant differences were seen for Aβ5-40 (P = 0.001), Aβ1-34 (P = 0.001) and Aβ11-40 (P = 0.002). For NB-C8, significant differences were seen between vehicle and treatment at 16 h for Aβ5-40 (P = 0.01) and Aβ1-34 (P = 0.05). Data are means; error bars are SD.</p

Summary of processing pathways.

<p>The main pathways of Aβ peptide release and how these are affected by BACE1 inhibition (arrows indicate absolute and/or relative changes). The APP box shows major APP cleaving secretases with selected cleavage sites that depend on them.</p

Cell medium Aβ isoform patterns.

<p>SH-SY5Y APP695wt cells treated with AZ-20 (Panel a). SHSY-5Y APP695swe cells treated with AZ-20 (Panel b). 7PA2 APP751 V717F cells treated with AZ-20 (Panel c). HeLa-APPswe cells treated with β-secretase inhibitor IV (Panel d). HeLa-APPswe mock and scrambled siRNA-transfected control cells, and cells transfected with single oligo siRNA or pooled siRNA against BACE1 (Panels e). N = 1 for each concentration and treatment.</p