If treatments for cognitive impairment are to be utilized successfully, clinicians must be able to determine whether they are effective and which patients should receive them. In order to develop consensus on these issues, the International Society for CNS Clinical Trials and Methodology (ISCTM) held a meeting of experts on March 20, 2014, in Washington, DC. Consensus was reached on several important issues. Cognitive impairment and functional disability were viewed as equally important treatment targets. The group supported the notion that sufficient data are not available to exclude patients from available treatments on the basis of age, severity of cognitive impairment, severity of positive symptoms, or the potential to benefit functionally from treatment. The group reached consensus that cognitive remediation is likely to provide substantial benefits in combination with procognitive medications, although a substantial minority believed that medications can be administered without nonpharmacological therapy. There was little consensus on the best methods for assessing cognitive change in clinical practice. Some participants supported the view that performance-based measures are essential for measurement of cognitive change; others pointed to their cost and time requirements as evidence of impracticality. Interview-based measures of cognitive and functional change were viewed as more practical, but lacking validity without informant involvement or frequent contact from clinicians. The lack of consensus on assessment methods was viewed as attributable to differences in experience and education among key stakeholders and significant gaps in available empirical data. Research on the reliability, validity, sensitivity, and practicality of competing methods will facilitate consensus.

Abstract
Objective: To survey the current approaches of clinical trial sponsors in prospective suicidal ideation and behavior assessments and challenges encountered. Design: An internet-based survey. Setting: Inclusion of prospective assessments of suicidal ideation and behavior in industry-sponsored clinical studies were required following the release of the September 2010 United States Federal Drug Administration draft guidance. The International Society for CNS Clinical Trials and Methodology Suicidal Ideation and Behavior Assessment Workgroup conducted an online survey to understand industry practices and experiences in implementing suicidal ideation and behavior assessments in clinical trials. Participants: The survey was sent to 1,447 industry employees at 178 pharmaceutical companies. A total of 89 evaluable responses, representing 39 companies, were obtained. Measurements: A 30-item internet survey was developed asking about potential challenges and issues in implementing prospective suicidal ideation and behavior assessments. Results: Common factors in deciding whether to include suicidal ideation and behavior assessments in a clinical trial were psychiatric or neurologic drug product (95%); central nervous system activity (78%); disease (74%) and patient population (71%); and regulatory announcements and policies (74%). The most common challenges in implementing suicidal ideation and behavior assessments included cross-cultural differences in acceptance of SIB assessments (40%); obtaining adequate baseline history (36.8%); obtaining translations (35%); investigator/rater discomfort with asking about suicidal ideation and behavior (32%); and inadequate training of raters to administer suicidal ideation and behavior ratings (30%). Conclusion: Among sponsors surveyed, the implementation rate of suicidal ideation and behavior assessment in central nervous systems studies is very high. Most have used the Columbia-Suicide Severity Rating Scale. Challenges regarding standardization of retrospective assessment timeframes and differing approaches to summarizing and analyzing suicidal ideation and behavior-related study data were frequently reported. These results suggest that inconsistent reports of suicidal ideation and behavior within study datasets may occur and that integration of data across studies remains a concern.

Last week at a meeting on clinical trials for central nervous system treatments, researchers convened to grapple with what they see as a serious and underrecognized problem in drug development: the fact that many people in clinical trials stop taking their experimental medications or don't take them as prescribed. These nonadherent participants can diminish the apparent effects of a drug compared with placebo and can potentially mask a drug's side effects or safety risks. As researchers recognize the effect of the problem on their trial data, some are taking greater pains to measure adherence through blood tests or electronic monitoring, and some are considering ways to design more adherence-friendly trials.
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BACKGROUND: The increasing prevalence of Alzheimer disease (AD) and lack of effective agents to attenuate progression have accelerated research and development of disease modifying (DM) therapies. The traditional parallel group design and single time point analysis used in the support of past AD drug approvals address symptomatic benefit over relatively short treatment durations. More recent trials investigating disease modification are by necessity longer in duration and require larger sample sizes. Nevertheless, trial design and analysis remain mostly unchanged and may not be adequate to meet the objective of demonstrating disease modification. Randomized start design (RSD) has been proposed as an option to study DM effects, but its application in AD trials may have been hampered by certain methodological challenges.
PURPOSE: To address the methodological issues that have impeded more extensive use of RSD in AD trial and to encourage other researchers to develop novel design and analysis methodologies to better ascertain DM effects for the next generation of AD therapies, we propose a stepwise testing procedure to evaluate potential DM effects of novel AD therapies.
METHODS: Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-cog) is used for illustration. We propose to test three hypotheses in a stepwise sequence. The three tests pertain to treatment difference at two separate time points and a difference in the rate of change. Estimation is facilitated by the Mixed-effects Model for Repeated Measures approach. The required sample size is estimated using Monte Carlo simulations and by modeling ADAS-cog data from prior longitudinal AD studies.
RESULTS: The greatest advantage of the RSD proposed in this article is its ability to critically address the question on a DM effect. The AD trial using the new approach would be longer (12-month placebo period plus 12-month delay-start period; total 24-month duration) and require more subjects (about 1000 subjects per arm for the non-inferiority margin chosen in the illustration). It would also require additional evaluations to estimate the rate of ADAS-cog change toward the end of the trial.
LIMITATIONS: A regulatory claim of disease modification for any compound will likely require additional verification of a drug's effect on a validated biomarker of Alzheimer's pathology.
CONCLUSIONS: Incorporation of the RSD in AD trials is feasible. With proper trial setup and statistical procedures, this design could support the detection of a disease-modifying effect. In our opinion, a two-phase RSD with a stepwise hypothesis testing procedure could be a reasonable option for future studies.

In central nervous system therapeutic areas, there are general concerns with establishing efficacy thought to be sources of high attrition rate in drug development. For instance, efficacy endpoints are often subjective and highly variable. There is a lack of robust or operational biomarkers to substitute for soft endpoints. In addition, animal models are generally poor, unreliable or unpredictive. To increase the probability of success in central nervous system drug development program, adaptive design has been considered as an alternative designs that provides flexibility to the conventional fixed designs and has been viewed to have the potential to improve the efficiency in drug development processes. In addition, successful implementation of an adaptive design trial relies on establishment of a trustworthy logistics model that ensures integrity of the trial conduct.

In accordance with the spirit of the U.S. Food and Drug Administration adaptive design draft guidance document recently released, this paper enlists the critical considerations from both methodological aspects and regulatory aspects in reviewing an adaptive design proposal and discusses two general types of adaptations, sample size planning and re-estimation, and two-stage adaptive design. Literature examples of adaptive designs in central nervous system are used to highlight the principles laid out in the U.S. FDA draft guidance. Four logistics models seen in regulatory adaptive design applications are introduced. In general, complex adaptive designs require simulation studies to access the design performance. For an adequate and well-controlled clinical trial, if a Learn-and-Confirm adaptive selection approach is considered, the study-wise type I error rate should be adhered to. However, it is controversial to use the simulated type I error rate to address a strong control of the study-wise type I error rate.

Adaptive clinical trial designs offer significant opportunities to optimize the conduct of clinical trials for the benefit of the subjects in the trial, the subjects that may be treated after the trial and the trial sponsor. However currently, the use of adaptive designs is limited, due to statistical, regulatory and logistical concerns. In this article we share our experience of overcoming the last of these over a range of phase 2, response adaptive, dose finding studies. Based on our experience we feel quite strongly that the logistics of executing adaptive trials should not be a barrier to their use.