Bone turnover markers and pharmacokinetics of a new sustained-release formulation of the cathepsin K inhibitor, ONO-5334, in healthy post-menopausal women.

A sustained-release tablet (SRT) of ONO-5334 was compared to the immediate-release tablet (IRT) dose, which demonstrated effects on bone mineral density (BMD) comparable to those of therapy with alendronate. The single-dose phase was a randomized, partial single-blind, crossover study where 50-, 100-, and 300-mg SRTs and 300-mg IRTs were administered to nine post-menopausal women. The multiple-dose phase was a randomized, double-blind, placebo-controlled, parallel-group study where 100- and 300-mg SRTs, or placebo were administered to 24 women. After a single administration of a 300-mg SRT, mean C max was 3.3-fold lower, mean AUCinf was 0.83-fold lower and mean C 24h was 5.4-fold higher compared to the 300-mg IRT. Repeated SRT dosing did not significantly affect PK, although C 24h increased slightly. After a single ONO-5334 dose, serum CTX-I was suppressed by ~50 % within 1 h, reaching maximum suppression 6 h post-dose. Greater suppression was maintained longer by the 300-mg SRT vs. the 300-mg IRT. Second morning void and cumulative urine CTX-I showed clear dose-response effects at/over 24 h for SRT, with maximum suppression occurring at/over 24 h (except 50- and 300-mg cumulative urine). Repeated dosing suggested greater suppression of urine CTX-I. Compared with the IRT, the SRT showed reduced C max, greater C 24h, and slightly reduced AUCinf dose for dose. The SRT showed clear dose-response suppression on bone resorption and greater efficacy dose for dose vs. the IRT.

[New approach for osteoporosis treatment: cathepsin K inhibitor, ONO-5334].

ONO-5334, an orally-administered low-molecular compound, is a selective synthetic inhibitor of cathepsin K which is specifically expressed in osteoclasts and has a critical role in bone-collagen degradation. ONO-5334 is being developed by Ono Pharmaceutical Co., Ltd. as a possible therapeutic agent for osteoporosis. ONO-5334 has been shown to prevent the decrease in bone mineral density (BMD) in the ovariectomized cynomolgus monkey osteoporosis model. In a 12-month clinical study with postmenopausal osteopenia or osteoporosis, ONO-5334 showed a significant increase in BMD compared with placebo and a similar magnitude of suppression on bone resorption compared with the current well known anti-resorptive agents, bisphosphonates, but with little or no suppression on bone formation. There were no clinically relevant safety concerns identified in this study. Whether this mechanism of action may result in more potent anti-fracture efficacy accompanied by better bone quality in long term use of ONO-5334 is of significant interest.

Relevance of astrocytic activation to reductions of astrocytic GABAA receptors.

Although astrocytes express gamma-aminobutyric acid subtype-A (GABAA) receptors in the mature brain, GABAA receptor expression in a cultivation state remains controversial. In this study, we investigated the alteration of astrocytic GABAA receptor expression in in vitro and in vivo studies to elucidate the relevance of astrocytic activation to reductions of astrocytic GABAA receptors. The GABA-evoked Cl- current (GABAA response) in cultured astrocytes was determined by recording in the whole-cell mode using a conventional patch-clamp technique under voltage-clamp conditions. The respective amplitudes of GABAA responses on days in vitro 1, 3-5, 7-10, and 12-15 were 1019+/-97, 512+/-76, 84+/-21, and 22+/-9 pA, respectively, suggesting that the GABAA response subsequently diminished with in vitro aging. In immunohistochemical and biochemical analyses, the expression of GABAA receptor beta-subunit decreased, whereas expressions of glial fibrillary acidic protein (GFAP) and S100B, hallmarks of astrocytic activation, increased dramatically in the cultured astrocytes with in vitro aging. With the use of [3H]SR95531, a GABAA-specific ligand, at 24 h after transient focal ischemia, binding was significantly reduced in the astrocytic fractions without affecting the synaptosomal fractions, and decreases in the mRNA expression level of GABAA receptor beta-subunits were concurrently observed. Interestingly, the loss of GABAA response in cultured astrocytes was mitigated by co-culturing with neurons or treatments with monoclonal S100B antibodies. These results indicate that astrocytic GABAA receptors are reduced with in vitro aging and cerebral ischemia, presumably through the overproduction of S100B in activated astrocytes.