Ethical issues in the design of osteoporosis clinical trials: the state of the question

Soy components vs. whole soy: are we betting our bones on a long shot?

Soybeans are a good source of bone-healthy nutrients. Epidemiological studies in Asia evaluating diets containing traditional whole soy foods show a positive association with bone mineral density and fracture protection. Smaller scale intervention studies in Western nations mainly feature isolated soy protein (SP) and purified or concentrated soy isoflavones (SI) rather than whole soy foods and they have produced inconsistent results. Consumption of SP does not alter calcium (Ca) retention even though urinary Ca excretion is less in diets with SP compared with proteins higher in sulfur-containing amino acids. SI, often consumed at higher concentrations than would be available in traditional Asian diets, are not yielding the type of incontrovertible evidence that might be expected in support of their benefit to bone health. This forces one to ask whether whole soy might provide a superior effect on bone.

Clinical evaluation of novel bisphosphonate dosing regimens in osteoporosis: The role of comparative studies and implications for future studies

BACKGROUND

Daily nitrogen-containing bisphosphonates have shown antifracture efficacy in many studies of postmenopausal osteoporosis. However, current dosing schedules are often inconvenient or impractical for patients. Efforts to reduce dosing frequency to improve adherence (ie, compliance and persistence), and therefore treatment outcomes, are ongoing. Although a number of trial designs can be used to consider the efficacy of therapy, comparing the efficacy of different regimens should only be undertaken in purposefully designed head-to-head studies.

OBJECTIVE

This article summarizes the design and conduct of clinical studies that have investigated alternative bisphosphonate regimens and those that have directly compared different approved bisphosphonates. It also explores the implications for future studies of postmenopausal osteoporosis treatment.

METHODS

Using the terms bisphosphonate, daily, weekly, and monthly, a search (completed in 2006) of the PubMed database was conducted to identify primary English-language publications of pertinent studies comparing either novel with established regimens of the same bisphosphonates or different established bisphosphonates.

RESULTS

The first option is the equivalence or noninferiority bridging study for comparison of new treatment regimens versus the established regimen of the same bisphosphonate, known as the active comparator. Four such studies have led to the registration of novel bisphosphonate dosing regimens designed to provide easier dosing alternatives for patients. The second option is the active comparator study, which compares one bisphosphonate with the most prescribed weekly bisphosphonate. Weekly dosed oral alendronate has previously been shown to be superior (for bone mineral density gains) to daily and weekly dosed oral risedronate. An ongoing noninferiority study, Monthly Oral Therapy with Ibandronate for Osteoporosis Intervention, is comparing weekly alendronate with ibandronate, a monthly oral bisphosphonate.

CONCLUSIONS

The exploration of new dosing schedules and formulations aims to identify the optimal bisphosphonate regimen for postmenopausal osteoporosis. To achieve this, careful consideration must be given to the choice of a scientifically valid study design that effectively, and ethically, meets the study objectives. Given the concerns regarding placebo-controlled antifracture studies, 2 alternative study designs should be considered, both using validated surrogate end points (bone mineral density and biochemical markers of bone turnover) as the principal mode of assessment.

Is it ethical to use placebos in osteoporosis trials?

The use of placebo control groups (e.g., subjects using calcium and vitamin D) in osteoporosis trials with subjects at high risk for fracture has been systematically questioned by institutional review boards (IRBs). Regulatory agencies, on the other hand, continue to not only recommend but also require that placebo-controlled trials be presented for the registration of new drugs for osteoporosis treatment. The Declaration of Helsinki and its updates have upheld the principle that protection of research subjects' rights is of primary concern. Nevertheless, even the Declaration keeps clearly opening the possibility of using placebo-control designs if it is justified for "compelling and scientifically sound methodological reasons." The use of intermediary endpoints or surrogates to establish the efficacy or safety of new medications in the management of osteoporosis is currently considered scientifically insufficient. This concept has led regulatory agencies, such as the Food and Drug Administration in the United States and the European Medicines Agency in the European Union, to require "fragility fracture reduction" as the primary endpoint in clinical trials for the registration of new drugs. Superiority or noninferiority trials are alternatives to placebo-controlled designs. However, factors such as sample size, cost, and statistical limitations render these models impractical for the registration of new medications for osteoporosis. We recommend collaboration among regulatory agencies, IRBs, scientists, and ethicists on the design of clinical trials for the registration of new medications for reduction of fracture risk. Delay in developing mutually acceptable models may impair scientific development in the field and possibly deprive patients of potentially beneficial treatments.

Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients

Background

For adults, vitamin D intake of 100 mcg (4000 IU)/day is physiologic and safe. The adequate intake (AI) for older adults is 15 mcg (600 IU)/day, but there has been no report focusing on use of this dose.

Methods

We compared effects of these doses on biochemical responses and sense of wellbeing in a blinded, randomized trial. In Study 1, 64 outpatients (recruited if summer 2001 25(OH)D <61 nmol/L) were given 15 or 100 mcg/day vitamin D in December 2001. Biochemical responses were followed at subsequent visits that were part of clinical care; 37 patients completed a wellbeing questionnaire in December 2001 and February 2002. Subjects for Study 2 were recruited if their 25(OH)D was <51 nmol/L in summer 2001. 66 outpatients were given vitamin D; 51 completed a wellbeing questionnaire in both December 2002 and February 2003.

Results

In Study 1, basal summer 25-hydroxyvitamin D [25(OH)D] averaged 48 ± 9 (SD) nmol/L. Supplementation for more than 6 months produced mean 25(OH)D levels of 79 ± 30 nmol/L for the 15 mcg/day group, and 112 ± 41 nmol/L for the 100 mcg/day group. Both doses lowered plasma parathyroid hormone with no effect on plasma calcium. Between December and February, wellbeing score improved more for the 100-mcg/day group than for the lower-dosed group (1-tail Mann-Whitney p = 0.036). In Study 2, 25(OH)D averaged 39 ± 9 nmol/L, and winter wellbeing scores improved with both doses of vitamin D (two-tail p < 0.001).

Conclusion

The highest AI for vitamin D brought summertime 25(OH)D to >40 nmol/L, lowered PTH, and its use was associated with improved wellbeing. The 100 mcg/day dose produced greater responses. Since it was ethically necessary to provide a meaningful dose of vitamin D to these insufficient patients, we cannot rule out a placebo wellbeing response, particularly for those on the lower dose. This work confirms the safety and efficacy of both 15 and 100 mcg/day vitamin D₃ in patients who needed additional vitamin D.