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.

Regulatory Perspectives in Pharmacometric Models of Osteoporosis.

Osteoporosis is a disorder of the bones in which they are weakened to the extent that they become more prone to fracture. There are various forms of osteoporosis: some of them are induced by drugs, and others occur as a chronic progressive disorder as an individual gets older. As the median age of the population rises across the world, the chronic form of the bone disease is drawing attention as an important worldwide health issue. Developing new treatments for osteoporosis and comparing them with existing treatments are complicated processes due to current acceptance by regulatory authorities of bone mineral density (BMD) and fracture risk as clinical end points, which require clinical trials to be large, prolonged, and expensive to determine clinically significant impacts in BMD and fracture risk. Moreover, changes in BMD and fracture risk are not always correlated, with some clinical trials showing BMD improvement without a reduction in fractures. More recently, bone turnover markers specific to bone formation and resorption have been recognized that reflect bone physiology at a cellular level. These bone turnover markers change faster than BMD and fracture risk, and mathematically linking the biomarkers via a computational model to BMD and/or fracture risk may help in predicting BMD and fracture risk changes over time during the progression of a disease or when under treatment. Here, we discuss important concepts of bone physiology, osteoporosis, treatment options, mathematical modeling of osteoporosis, and the use of these models by the pharmaceutical industry and the Food and Drug Administration.

Reduced bone mineral density in human immunodeficiency virus-infected patients and its association with increased central adiposity and postload hyperglycemia.

Reduced bone mineral density (BMD) and abnormalities in fat redistribution, glucose homeostasis, and lipid metabolism are prevalent among HIV-infected patients on highly active antiretroviral therapy (HAART). The relationship between the metabolic and skeletal complications of HIV is unclear. Fifty-one HIV patients on HAART (aged 30-54 yr, 86% male) and 21 HIV-negative control subjects (aged 31-51 yr, 82% male) were examined with oral glucose tolerance testing, a fasting lipid profile, and dual x-ray absorptiometry, and markers of bone formation (serum osteocalcin) and resorption (urinary deoxypyridinoline). HIV-infected subjects had a higher prevalence of either osteopenia or osteoporosis (World Health Organization criteria) at the spine, hip, or forearm, compared with HIV-negative controls (63% vs. 32%, P = 0.02) and evidence of increased bone resorption (urine deoxypyridinoline, 14.7 +/- 6.5 vs. 10.9 +/- 2.5 nmol/mmol creatinine, P = 0.012). Among the HIV-infected patients, those with reduced bone mineral density (n = 32) were similar to the group with normal BMD (n = 19) in the use of protease inhibitors, duration of HAART therapy, or other demographic variables. Plasma glucose 2 h after a glucose load (odds ratio 1.02 per 1 mg/dl increase, 95% confidence interval 1.01-1.05, P = 0.009) and central adiposity (trunk fat/total fat) (odds ratio 1.09 per 1% ratio increase, 95% confidence interval 1.00-1.18, P = 0.012) were associated with reduced BMD. These associations remained significant in a multivariate model including age and body mass index. Bone resorption was associated with female gender (P < 0.001) and non-high-density lipoprotein cholesterol (P = 0.034) in a multivariate linear regression model controlling for age, body mass index, protease inhibitor use, duration of HAART, and extremity fat. Reduced BMD is prevalent in HIV-infected patients on HAART and is related to central adiposity and postload hyperglycemia. Bone resorption is independently associated with female gender and dyslipidemia. HIV-infected patients with metabolic abnormalities may represent a population that would benefit from bone density screening.

Bone quality: a perspective from the Food and Drug Administration.

Osteoporosis, a disease of compromised bone strength, is a leading cause of fracture, morbidity, and mortality. The past 10 years have resulted in the development of new pharmacologic therapies for the treatment of this disease. Most of these agents have been approved for the treatment of osteoporosis based on placebo-controlled fracture trials. However, recent ethical concerns regarding placebo-controlled trials threaten to derail the development of new, possibly better, treatment options. Novel noninvasive imaging technologies may offer greater insight into the pathophysiology and biomechanics of osteoporosis and fracture. Because of these advances, many hope to find a new biomarker that will predict fracture risk better than the current bone density measurements and that ultimately will replace fracture as the primary endpoint for osteoporosis drug registration trials. This paper discusses the perspective of a Food and Drug Administration reviewer regarding the role of surrogate markers as they relate to the quest for new, safe and efficacious treatments for osteoporosis.