A pharmacokinetic study of extended-release buprenorphine in cynomolgus monkeys (Macaca fasicularis)

BACKGROUND

A novel buprenorphine (BUP) extended-release formulation (BUP-XR) produced as a lipid-encapsulated, low viscosity BUP suspension for subcutaneous (SC) injection to control pain was evaluated for pharmacokinetics and safety in four adult male cynomolgus monkeys.

METHODS

Each animal was given 0.2 mg/kg reformulated BUP-XR SC. Clinical observations were made during the course of the study. Blood samples were obtained from each animal before BUP-XR administration, 6, 24, 48, 72, and 96 h post-BUP-XR injection. Plasma levels of buprenorphine were analyzed using HPLC-MS/MS. The PK values calculated included peak plasma concentration of the BUP analyte, time to peak plasma concentration, plasma half-life, area under the plasma concentration-time curve, clearance, apparent volume of distribution, and elimination rate constant (Cmax , Tmax , T½ , AUC0-t , CL, Vd, and Ke, respectively).

RESULTS

Observable adverse clinical signs were not detected. BUP concentration peaked from 6 to 48 h, then declined in a linear fashion. Quantifiable plasma BUP was measured in all monkeys at all time points. Results indicate that a single BUP-XR dose at 0.2 mg/kg can reliably provide plasma levels of BUP reported in the literature to be therapeutically relevant for up to 96 h.

CONCLUSIONS

Because of the lack of any clinical observations or adverse effects at the injection site or absence of observable abnormal behaviors, it may be concluded that the use of BUP-XR is safe and efficacious in this species of non-human primate at the dose regimen described in this study for up to 96 h post-administration.

Pharmacokinetic and Histopathologic Study of an Extended-Release, Injectable Formulation of Buprenorphine in Sprague-Dawley Rats

A novel buprenorphine (BUP) extended-release formulation (BUP-XR) produced as a lipid-encapsulated, low viscosity BUP suspension for SC injection to control pain was evaluated for pharmacokinetics and safety in Sprague-Dawley rats given either 0.65 mg/kg (low dose) or 1.30 mg/kg (high dose). The 2 dosage groups each contained 6 male and 6 female rats to determine whether BUP-XR behaved differently in male or female animals. Blood samples were obtained from each animal before BUP-XR administration and at 6, 24, 48, 72, 96, and 168 h after administration. For necropsy and injection-site histopathology evaluation, 3 animals of each sex from each test group were euthanized on day 8, with the remaining animals euthanized on day 15. Mean plasma BUP concentration peaked from 6 to 24 h in all test groups, then declined in a linear fashion. Quantifiable plasma BUP was measured in all male rats at all time points except for one low dose group sample taken at 168 h. Female rats had quantifiable plasma BUP at all time points except for 1 low dose group sample at 72 and 96 h, and 2 low dose group samples at 168 h. The low dose groups, whether male or female, had lower mean plasma BUP levels at all time points as compared with their high dose counterparts, and female rats had lower mean plasma BUP levels than male rats at all time points. Results indicate that a single BUP-XR dose at either dose concentration can reliably provide plasma levels of BUP reported in the literature to be therapeutically relevant for up to 72 h, although lower plasma BUP levels can be anticipated in female rats compared with male counterparts. Mild to moderate injection-site granulomatous inflammation was observed in 6 of 12 rats in the low dose group and 7 of 12 in the high dose group. This reaction is characteristic of lipid material designed to persist in situ.

Hydroxamic acids as potent inhibitors of endothelin-converting enzyme from human bronchiolar smooth muscle

Hydroxamic acids 6a-h, derived from malonyl amino acids, and 25a-d, derived from succinyl amino acids, were synthesized as inhibitors of human bronchiolar smooth muscle endothelin-converting enzyme (HBSM ECE). Several unexpected side reactions were discovered, particularly in the synthesis of hydroxamates derived from succinates. In vitro evaluation against human bronchiolar ECE revealed that in all cases hydroxamates derived from malonate were more potent than hydroxamates derived from succinate. Isopropyl and isobutyl P1' side chains were suitable; omission of the P1' side chain seriously diminished potency. In the P2' position, several amino acids gave potent malonate-derived hydroxamate inhibitors (6b, d-h, IC50 = 0.2-6.8 nM), and beta-Ala provided an extremely potent inhibitor (6c, IC50 = 0.01 nM). C-terminus carboxylates are much more potent ECE inhibitors than the corresponding amides. Most of the hydroxamates were also potent inhibitors of thermolysin and neutral endopeptidase (NEP); however, the P2' beta-Ala derivative 6c uniquely inhibited HBSM ECE much more potently than NEP.

Identification of beta-exotoxin production, plasmids encoding beta-exotoxin, and a new exotoxin in Bacillus thuringiensis by using high-performance liquid chromatography

An improved high-performance liquid chromatography separation was developed to detect and quantify beta-exotoxin production in Bacillus thuringiensis culture supernatants. Exotoxin production was assigned to a plasmid in five strains, from three subspecies (B. thuringiensis subsp. thuringiensis serotype 1, B. thuringiensis subsp. tolworthi serotype 9, and B. thuringiensis subsp. darmstadiensis serotype 10). A new exotoxin, called type II beta-exotoxin in this report, was discovered in B. thuringiensis subsp. morrisoni serotype 8ab, purified, and partially characterized. This material is more specific than type I beta-exotoxin and is very active against the Colorado potato beetle, Leptinotarsa decemlineata.

The position of the ATP binding site on the (Ca2+ + Mg2+)-ATPase

We present a convenient method to calculate the efficiency of fluorescence energy transfer in two-dimensional membrane systems. We apply it to the analysis of energy transfer between phospholipid molecules labelled with fluorescein and rhodamine groups, and of energy transfer in reconstituted membranes containing (Ca2+ + Mg2+)-ATPase purified from sarcoplasmic reticulum, with the ATPase labelled at the ATP binding site with fluorescein as donor, and rhodamine-labelled lipid as acceptor. The ATP binding site is found to be distant from the plane of the lipid/water interface of the membrane. It is suggested that the ATPase is present in the membrane as a dimer, with the two ATP binding sites in the dimer being close to the protein/protein interface. Addition of vanadate causes no change in quenching, suggesting that the ATP binding site does not move significantly with respect to the lipid/water interface in the E1-E2 conformational transition of the ATPase.

Crystallization and preliminary X-ray diffraction studies of colicin E3 immunity protein

Immunity protein, an inhibitor of the ribonuclease activity of the protein antibiotic colicin E3, crystallizes in the orthorhombic space group C222 with cell dimensions a = 78.7 A, b = 54.1 A, c = 36.1 A and one molecule of Mr 9800 per asymmetric unit. The crystals are suitable for high resolution X-ray analysis.

Dimerization by colicin E3 in the absence of immunity protein

Using small angle x-ray scattering from solutions of colicin E3-immunity protein complex and the separated proteins, we have measured the radii of gyration of each species. We find that the complex is an elongated molecule with a radius of gyration of 35.5 +/- 0.7 A. Immunity protein is more compact with a radius of gyration of 13.4 +/- 0.1 A. Upon removal of immunity protein from the complex, colicin E3 (form minus immunity protein) undergoes further elongation and dimerizes, such that its radius of gyration increases to 75.6 +/- 3.1 A. Dimerization is not reversed by simple addition of a stoichiometric amount of immunity protein to the E3 solution, even though this is sufficient to block in vitro activity. We suggest that the elongation, and perhaps dimer formation, occurs in vivo, concomitant with membrane translocation.