Clinical Pharmacology of Potent New Bisphosphonates for Postmenopausal Osteoporosis

Long-Term Oral Toxicity and Anti-osteoporotic Effect of Sintered Dicalcium Pyrophosphate in Rat Model of Postmenopausal Osteoporosis

Sintered dicalcium pyrophosphate (SDCP), a synthetic pyrophosphate analog, has shown potential for the management of osteoporosis. The long-term oral toxicity and anti-osteoporotic effect of SDCP in a postmenopausal osteoporosis rat model were evaluated in this study. SDCP was orally administered to bilateral ovariectomized (OVX) Wistar rats at a dose of 0.75 mg/kg daily for 24 weeks following by 2 weeks of observation. There were no abnormal findings in clinical signs of toxicity, food consumption, body weight, blood examination, necropsy, and histological inspection attributable to the ingestion of SDCP. The serum level of type I collagen fragments, a bone resorption marker, decreased in SDCP-treated rats, and the bone formation markers alkaline phosphatase, osteocalcin, and osteopontin significantly decreased. These findings indicate that the bone turnover rate decreased in SDCP-treated animals. Relative to OVX rats, the increase in serum tartrate-resistant acid phosphatase 5b level represents an increase in bony tissues in the SDCP-treated rats. Histological examinations of distal femoral metaphyses further revealed that the ingestion of SDCP improved the trabecular bone architecture and decreased bone porosity. Analysis of limb bone ashes showed a significant increase in bone mineral content. Our results show that SDCP inhibits bone resorption to restore bone mass in OVX rats without deleterious effects, and therefore that SDCP has potential in the management of osteoporosis.

Postmenopausal osteoporosis treatment with antiresorptives: effects of discontinuation or long-term continuation on bone turnover and fracture risk--a perspective

Osteoporosis may be a lifelong condition. Robust data regarding the efficacy and safety of both long-term osteoporosis therapy and therapy discontinuation are therefore important. A paucity of clinical trial data regarding the long-term antifracture efficacy of osteoporosis therapies necessitates the use of surrogate endpoints in discussions surrounding long-term use and/or discontinuation. Long-term treatment (beyond 3-4 years) may produce further increases in bone mineral density (BMD) or BMD stability, depending on the specific treatment and the skeletal site. Bisphosphonates, when discontinued, are associated with a prolonged reduction in bone turnover markers (BTMs), with a very gradual increase to pretreatment levels within 3 to 60 months of treatment cessation, depending on the bisphosphonate used and the prior duration of therapy. In contrast, with nonbisphosphonate antiresorptive agents, such as estrogen and denosumab, BTMs rebound to above pretreatment values within months of discontinuation. The pattern of BTM change is generally mirrored by a more or less rapid decrease in BMD. Although the prolonged effect of some bisphosphonates on BTMs and BMD may contribute to residual benefit on bone strength, it may also raise safety concerns. Adequately powered postdiscontinuation fracture studies and conclusive evidence on maintenance or loss of fracture benefit is lacking for bisphosphonates. Similarly, the effects of rapid reversal of bone turnover upon discontinuation of denosumab on fracture risk remain unknown. Ideally, studies evaluating the effects of long-term treatment and treatment discontinuation should be designed to provide head-to-head "offset" data between bisphosphonates and nonbisphosphonate antiresorptive agents. In the absence of this, a clinical recommendation for physicians may be to periodically assess the benefits/risks of continuation versus discontinuation versus alternative management strategies.

ACUTE AND SUBACUTE ORAL TOXICITY TESTS OF SINTERED DICALCIUM PYROPHOSPHATE ON OVARIECTOMIZED RATS FOR OSTEOPOROSIS TREATMENT

Sintered dicalcium pyrophosphate (SDCP) is a synthetic pyrophosphate analog that could be utilized in the treatment for osteoporosis. In this study, an ovariectomized rat model is used to evaluate the systematic toxicity of orally administered SDCP relative to its effects on bone mass. Ovariectomized Wistar rats were treated with experimental medication with different dosing strategies (0.5 mg/kg five days weekly, and 2.5 mg/kg once weekly) for once (acute oral toxicity test) and four weeks (subacute oral toxicity test) followed by recovery period. Clinical signs of toxicity, body weight, and food consumption of rats were recorded. Blood samples were collected for hematological and blood biochemical analyses. Rats were sacrificed for necropsy and major visceral organs were harvested for histological examination after the recovery period. Long bones of four limbs were harvested to evaluate the effects of SDCP on bone mass. Results showed that there was no change in clinical signs, body weight, food consumption, hematology, blood biochemistry, necropsy, and histological examination attributable to the oral administration with SDCP to rats during the dosing period and the recovery period. Analysis of bone ashes revealed that the ovariectomized rats ingested with 0.5 mg/kg SDCP five days weekly continually for four weeks increased bone mineral contents significantly. In the ovariectomized rats ingested with 2.5 mg/kg SDCP once weekly continually for four weeks, the bone mineral contents were increased to normal bone quality. This study indicates that the SDCP can increase bone mass in the ovariectomized rat with no deleterious effects.

New generation pharmacotherapy in elderly multiple myeloma patients

BACKGROUND

Observational databases have demonstrated that the overall prognosis of multiple myeloma patients has markedly improved over the past decade, yet the greatest strides have been attained in younger rather than older patients.

OBJECTIVE

To review recent clinical trials that include new generation agents (thalidomide, lenalidomide and bortezomib) and autologous stem cell transplantation in older multiple myeloma patients.

RESULTS

Conventional regimens such as melphalan plus prednisone can be improved with the addition of thalidomide or bortezomib: more patients attain complete and near-complete remission, and progression-free survival rates are nearly doubled. In addition, autologous hematopoietic stem cell transplantation studies show that this treatment approach can be used successfully in selected older myeloma patients in whom the toxicity profile of autotransplant and resulting overall survival may be similar to that obtained in the younger patient group.

CONCLUSIONS

In the advanced-age population, implementation of new therapies results in significant benefits in older as well as younger patients.