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Comparative Effectiveness Clinical Trials in Psychiatry: Superiority, Non-inferiority and the Role of Active Comparators

AC Leon
Journal of Clinical Psychiatry 2011;72(10):1344–1349 10.4088/JCP.10m06089whi
The Agency for Healthcare Research and Quality, part of the US Department of Health and Human Services, has issued several Requests for Applications to conduct comparative effectiveness research (CER). Many of the applications will involve randomized controlled clinical trials that include an active comparator. The inclusion of an active comparator has implications for clinical trial design.

Despite a common misperception, a clinical trial result of no significant difference between active treatment groups does not imply equivalence or noninferiority. A noninferiority trial, on the other hand, can directly test whether one active treatment group is noninferior to the other. For example, noninferiority of an inexpensive generic could be tested in comparison with a novel, more costly intervention. Although seldom used in psychiatry, noninferiority clinical trials could play a fundamental role in CER. Features of noninferiority and the nearly ubiquitous superiority designs are contrasted. The noninferiority margin is defined and its application and interpretation are discussed.

Evidence of noninferiority can only come from well-designed and conducted noninferiority CER. Sample sizes needed in noninferiority trials and in superiority trials that include an active comparator are substantially larger than those needed in trials that can utilize a placebo control in their scientific design. As a result, trials with active comparators are more costly, require longer recruitment duration, and expose more participants to the risks of an experiment than do trials in which the only comparator is placebo.

Two Clinical Trial Designs to Examine Personalized Treatments for Psychiatric Disorders (2009 Scientific Meeting, Arlington)

AC Leon
Journal of Clinical Psychiatry. 2011 May;72(5):593-7. Epub 2010 Jul 13
The National Institute of Mental Health Strategic Plan calls for the development of personalized treatment strategies for mental disorders. In an effort to achieve that goal, several investigators have conducted exploratory analyses of randomized controlled clinical trial (RCT) data to examine the association between baseline subject characteristics, the putative moderators, and the magnitude of treatment effect sizes. Exploratory analyses are used to generate hypotheses, not to confirm them. For that reason, independent replication is needed. Here, 2 general approaches to designing confirmatory RCTs are described that build on the results of exploratory analyses. These approaches address distinct questions. For example, a 2 × 2 factorial design provides an empirical test of the question, “Is there a greater treatment effect for those with the single-nucleotide polymorphism than for those without that polymorphism?” and the hypothesis test involves a moderator-by-treatment interaction. In contrast, a main effects strategy evaluates the intervention in subgroups and involves separate hypothesis-testing studies of treatment for subjects with the genotypes hypothesized to have enhanced and adverse response. These designs require widely disparate sample sizes to detect a given effect size. The former could need as many as 4-fold the number of subjects. As such, the choice of design impacts the research costs, clinical trial duration, and number of subjects exposed to risk of an experiment, as well as the generalizability of results. When resources are abundant, the 2 × 2 design is the preferable approach for identifying personalized interventions because it directly tests the differential treatment effect, but its demand on research funds is extraordinary.

What is Causing the Reduced Drug-Placebo Difference in Recent Schizophrenia Clinical Trials and What Can be Done About It? (2007 Mid-Year Conference, Brussels)

A Kemp , NR Schooler, AH Kalali, L Alphs, R Anand, G Awad, M Davidson, S Dubé, L Ereshefsky, G Gharabawi, AC Leon, JP Lepine, SG Potkin, A Vermeulen
Schizophrenia Bulletin 2008, Vol. 36, No. 3
On September 18, 2007, a collaborative session between the International Society for CNS Clinical Trials and Methodology and the International Society for CNS Drug Development was held in Brussels, Belgium. Both groups, with membership from industry, academia, and governmental and nongovernmental agencies, have been formed to address scientific, clinical, regulatory, and methodological challenges in the development of central nervous system therapeutic agents. The focus of this joint session was the apparent diminution of drug-placebo differences in recent multicenter trials of antipsychotic medications for schizophrenia. To characterize the nature of the problem, some presenters reported data from several recent trials that indicated higher rates of placebo response and lower rates of drug response (even to previously established, comparator drugs), when compared with earlier trials. As a means to identify the possible causes of the problem, discussions covered a range of methodological factors such as participant characteristics, trial designs, site characteristics, clinical setting (inpatient vs outpatient), inclusion/exclusion criteria, and diagnostic specificity. Finally, possible solutions were discussed, such as improving precision of participant selection criteria, improving assessment instruments and/or assessment methodology to increase reliability of outcome measures, innovative methods to encourage greater subject adherence and investigator involvement, improved rater training and accountability metrics at clinical sites to increase quality assurance, and advanced methods of pharmacokinetic/pharmacodynamic modeling to optimize dosing prior to initiating large phase 3 trials. The session closed with a roundtable discussion and recommendations for data sharing to further explore potential causes and viable solutions to be applied in future trials.

Trial designs likely to meet valid long-term Alzheimer’s disease progression effects: learning from the past, preparing for the future

A Kemp , G Grossberg. S Romano, D Arnold, J Ryan, R Bullock, D Streiner
International Journal of Alzheimer's Disease, 2009 Dec 22;2009
The International Society for CNS Clinical Trials and Methodology (ISCTM) held its 4th Annual Autumn Conference in Toronto, Ontario, October 6-7, 2008. The purpose of the present report is to provide an overview of one of the sessions at the conference which focused on the designs and methodologies to be applied in clinical trials of new treatments for Alzheimer's disease (AD) with purported "disease-modifying" effects. The session began with a discussion of how neuroimaging has been applied in multiple sclerosis clinical trials (another condition for which disease modification claims have been achieved). The next two lectures provided a pharmaceutical industry perspective on some of the specific challenges and possible solutions for designing trials to measure disease progression and/or modification. The final lecture provided an academic viewpoint and the closing discussion included additional academic and regulatory perspectives on trial designs, methodologies, and statistical issues relevant to the disease modification concept.

Defining a Clinically Meaningful Effect for the Design and Interpretation of Randomized Controlled Trials

R Keefe , H Kraemer. R Epstein, E Frank, G Haynes, T Laughren, J McNulty, S Reed, J Sanchez, AC Leon
Innovations in Clinical Neuroscience: May-June 2013 (ISCTM Supplement #1)

Sample sizes required to detect two-way and three-way interactions involving slope differences in mixed-effects linear models

M Heo , AC Leon
Journal of Biopharmaceutical Statistics. 2010 July;20
Based on maximum likelihood estimates obtained from mixed-effects linear models, closed-form power functions are derived to detect two-way and three-way interactions that involve longitudinal course of outcome over time in clinical trials. Sample size estimates are shown to decrease with increasing within-subject correlations. It is further shown that when clinical trial designs are balanced in group sizes, the sample size required to detect an effect size for a three-way interaction is exactly fourfold that required to detect the same effect size of a two-way interaction. Furthermore, this fourfold relationship virtually holds for unbalanced allocations of subjects if one factor is balanced in the three-way interaction model. Simulations are presented that verify the sample size estimates for two-way and three-way interactions.

An Introduction to Adaptive Designs and Adaptation in CNS Trials

V Dragalin
European Neuropsychopharmacology: February 2011 (Volume 21, Issue 2)
Adaptive designs learn from accumulating trial data in real time and apply this knowledge to optimize subsequent study execution. A set of design rules define a priori which modifications may be incorporated into the trial design. Judicious use of adaptive designs may increase the information value per resource unit invested by avoiding allocation of patients to non-efficacious/unsafe therapies and allowing stopping decisions to be made at the earliest possible time point. Ultimately this may accelerate the development of promising therapies.

Adaptive Clinical Trials for New Drug Applications in Japan

Y Ando , A Hirakawa, Y Uyama
European Neuropsychopharmacology Volume 21, Issue 2, February 2011
Adaptive design is regarded as an efficient method for clinical trials in order to increase the success rate of a new drug in development, and recently has been actively discussed among regulatory agencies, industry and academia. Since adaptive design involves interim analyses and is more complex than traditional fixed design, some points such as possibility of introducing statistical and operational bias should be considered when planning and implementing such trials. In this article, we share our perspectives in the consideration of adaptive design clinical trials based on our experiences discussing adaptive design in clinical trial consultation meetings in Japan.

Methodological Issues in Negative Symptom Trials

SR Marder , DG Daniel, L Alphs, AG Awad, RS Keefe
Schizophrenia Bulletin, 2011 Mar;37(2):250-4. Epub 2011 Jan 26
Individuals from academia, the pharmaceutical industry, and the US Food and Drug Administration used a workshop format to discuss important methodological issues in the design of trials of pharmacological agents for improving negative symptoms in schizophrenia. The issues addressed included the need for a coprimary functional measure for registration trials; the characteristics of individuals who should enter negative symptom trials; the optimal duration for a proof-of-concept or registration trial; the optimal design of a study of a broad-spectrum agent that treats both positive and negative symptoms or a co-medication that is added to an antipsychotic; the relative strengths and weaknesses of available instruments for measuring negative symptoms; the definition of clinically meaningful improvement for these trials; and whether drugs can be approved for a subdomain of negative symptoms.