The objective of this multicentre, parallel, blinded, randomized controlled study was to evaluate the efficacy and the safety of cyclosporine (CsA group, 117 dogs) in comparison with methylprednisolone (MP group, 59 dogs) in the treatment of atopic dermatitis for 4 months. Mean induction dose of both drugs (5 mg/kg CsA, 0.75 mg/kg MP) was tapered over time according to the clinical response. At the end of the study, the mean estimated percentage reduction from baseline (confidence interval) of lesion scores was 52% (44-59) and 45% (35-56), and the reduction in pruritus score was 36% (27-43) and 33% (23-43) in dogs in the CsA and MP groups, respectively. These percentages were not significantly different between groups. A significantly better overall assessment of efficacy was obtained in the CsA-treated dogs (76 vs. 63% responses excellent or good in the CsA compared with MP group). CsA-treated dogs presented a higher frequency of gastrointestinal disorders, mainly vomiting, but MP dogs tended to be more susceptible to infections. There was no remarkable change over baseline of the haematological and biochemical parameters in the two groups.

Results suggest that oral administration of cyclosporine at a dosage of 5.0 mg/kg once daily is effective in reducing severity of pruritus and skin lesions in dogs with AD, especially those with nonseasonal disease.

BackgroundSmall clinical trials are necessary when there are difficulties in recruiting enough patients for conventional frequentist statistical analyses to provide an appropriate answer. These trials are often necessary for the study of rare diseases as well as specific study populations e.g. children. It has been estimated that there are between 6,000 and 8,000 rare diseases that cover a broad range of diseases and patients. In the European Union these diseases affect up to 30 million people, with about 50% of those affected being children. Therapies for treating these rare diseases need their efficacy and safety evaluated but due to the small number of potential trial participants, a standard randomised controlled trial is often not feasible. There are a number of alternative trial designs to the usual parallel group design, each of which offers specific advantages, but they also have specific limitations. Thus the choice of the most appropriate design is not simple.MethodsPubMed was searched to identify publications about the characteristics of different trial designs that can be used in randomised, comparative small clinical trials. In addition, the contents tables from 11 journals were hand-searched. An algorithm was developed using decision nodes based on the characteristics of the identified trial designs.ResultsWe identified 75 publications that reported the characteristics of 12 randomised, comparative trial designs that can be used in for the evaluation of therapies in orphan diseases. The main characteristics and the advantages and limitations of these designs were summarised and used to develop an algorithm that may be used to help select an appropriate design for a given clinical situation. We used examples from publications of given disease-treatment-outcome situations, in which the investigators had used a particular trial design, to illustrate the use of the algorithm for the identification of possible alternative designs.ConclusionsThe algorithm that we propose could be a useful tool for the choice of an appropriate trial design in the development of orphan drugs for a given disease-treatment-outcome situation.

The proof-of-concept (PoC) decision is a key milestone in the clinical development of an experimental treatment. A decision is taken on whether the experimental treatment is further developed (GO), whether its development is stopped (NO-GO), or whether further information is needed to make a decision. The PoC decision is typically based on a PoC clinical trial in patients comparing the experimental treatment with a control treatment. It is important that the PoC trial be designed such that a GO/NO-GO decision can be made. The present work develops a generic, Bayesian framework for defining quantitative PoC criteria, against which the PoC trial results can be assessed. It is argued that PoC criteria based solely on significance testing versus the control are not appropriate in this decision context. A dual PoC criterion is proposed that includes assessment of superiority over the control and relevance of the effect size and hence better matches clinical decision making. The approach is illustrated for 2 PoC trials in cystic fibrosis and psoriasis.

The advent of molecular markers has created a great potential for the understanding of quantitative inheritance, in plants as well as in animals. Taking the newly available data into account, biometrical models have been constructed for the mapping of quantitative trait loci (QTLs). In current approaches, the lack of knowledge on the number and location of most important QTLs contributing to a trait is a major problem. In this paper, we utilize reversible jump Markov chain Monte Carlo (MCMC) methodology (Green 1995) in order to compute the posterior quantities required for fully Bayesian inference. It yields posterior densities not only for the parameters, given the number of QTL, but also for the number of QTL itself. As an example, the algorithm is applied to simulated data, according to a standard design in plant breeding. KEYWORDS: Quantitative trait locus; breeding scheme; Bayesian inference; reversible jump Markov chain Monte Carlo.