Regulatory aspects of the development of drugs for metabolic bone diseases - FDA and EMA perspective.

Regulation of medicines involves complex scientific and public health policies which are reflected in the regulatory approaches used by the European Medicines Agency and the United States Food and Drug Administration for the approval of products developed for metabolic bone diseases. For osteoporosis therapies, utilized by many patients, the approaches and existing guidance for product development of both agencies are similar; confirmatory studies for the approval of osteoporosis products can rely on well-defined efficacy outcome parameters. Therapeutics for rare bone diseases, a rapidly expanding area, often require an individualized regulatory approach. This review outlines key aspects of these regulatory approaches applied by the two agencies for products for metabolic bone diseases.

The European Medicines Agency's approval of new medicines for type 2 diabetes.

Since 2005, more than 40 new medicines for the treatment of type 2 diabetes have been introduced on the market. These consist of 15 new active substances establishing three new classes of non-insulin products, and several new or modified insulin products and combinations. The approval of these products in Europe is regulated via the centralized procedure at the European Medicines Agency. Demonstration of benefit with regard to improved glucose control remains the principal outcome required from confirmatory studies to demonstrate efficacy. For the majority of these new medicines approved since 2005, cardiovascular outcome trials have now been completed, and have invariably supported the cardiovascular safety of these products. In some of these trials additional important benefits have been observed, for instance, a reduction in major adverse cardiovascular events and improvement of renal outcome. The existing regulatory framework and the continuous adaption of regulatory requirements to emerging developments will continue to guide the approval of new products in the future.

Preoperative evaluation of microencapsulated human parathyroid tissue aids selection of the optimal bioartificial graft for human parathyroid allotransplantation.

Allotransplantation of microencapsulated parathyroid tissue is a promising approach to the treatment of permanent hypoparathyroidism. Preoperative assessment of the quality of microencapsulated parathyroid tissue could facilitate selection of the optimal bioartifical graft for human parathyroid allotransplantation. Parathyroid tissue from patients with secondary hyperparathyroidism (n = 15) was processed mechanically or enzymatically (collagenase type II). Tissue particles and single cells/cell clusters were routinely microencapsulated with amitogenic Ba(2+) alginate. Parathyroid secretion dynamics in response to stimulation of nonencapsulated and microencapsulated parathyroid tissue with Ca(2+) were evaluated in a perifusion system. The stability of the different types of microcapsule was assessed using an osmotic pressure test. Mechanical cutting of parathyroid tissue led to peripheral necrosis of tissue particles and impaired their vitality. Collagenase digestion, in contrast, resulted in single cells and cell clusters without peripheral necrosis. The quality of microencapsulation of single cells/cell clusters was significantly better than that of tissue particles (deformed and imperfect capsules). Microencapsulation itself did not decrease cell vitality. Nonencapsulated and microencapsulated tissue particles and single cells/cell clusters from different donors maintained their own levels of response to stimulation with low Ca(2+). Microcapsules containing tissue particles showed poor stability compared with those containing single cells/cell clusters. Preoperative evaluation of microencapsulated parathyroid tissue can disclose differences in vitality and function and thus facilitate selection of the optimal bioartifical graft for human parathyroid allotransplantation.

Functional characterization of GATA3 mutations causing the hypoparathyroidism-deafness-renal (HDR) dysplasia syndrome: insight into mechanisms of DNA binding by the GATA3 transcription factor.

The hypoparathyroidism-deafness-renal (HDR) dysplasia syndrome is an autosomal dominant disorder caused by mutations of the dual zinc finger transcription factor, GATA3. We investigated 21 HDR probands and 14 patients with isolated hypoparathyroidism for GATA3 abnormalities. Thirteen different heterozygous germline mutations were identified in patients with HDR. These consisted of three nonsense mutations, six frameshifting deletions, two frameshifting insertions, one missense (Leu348Arg) mutation and one acceptor splice site mutation. The splice site mutation was demonstrated to cause a pre-mRNA processing abnormality leading to the use of an alternative acceptor site 8 bp downstream of the normal site, resulting in a frameshift and prematurely terminated protein. Electrophoretic mobility shift assays (EMSAs) revealed three classes of GATA3 mutations: those that lead to a loss of DNA binding which represent over 90% of all mutations, and involved a loss of the carboxy-terminal zinc finger; those that resulted in a reduced DNA-binding affinity; and those (e.g. Leu348Arg) that did not alter DNA binding or the affinity but likely altered the conformational change that occurs during binding in the DNA major groove as predicted by a three-dimensional modeling. These results elucidate further the molecular mechanisms underlying the altered functions of mutants of this zinc finger transcription factor and their role in causing this developmental anomaly. No mutations were identified in patients with isolated hypoparathyroidism, thereby indicating that GATA3 abnormalities are more likely to result in two or more of the phenotypic features of the HDR syndrome and not in one, such as isolated hypoparathyroidism.