Power behind the throne: A clinical trial simulation study evaluating the impact of controllable design factors on the power of antidepressant trials

Are large prospective trials on antidepressants in mental disorders seeding trials? A descriptive study of trials registered on ClinicalTrials.gov

OBJECTIVES

This descriptive study of registered trials aimed to identify large clinical trials on antidepressants for mental disorders: (1) to assess what proportion could be labelled as 'seeding trials' (trials for marketing purposes) and (2) to describe their methodological characteristics and outcomes.

DESIGN

A search was conducted across all trials registered on ClinicalTrials.gov by drug name in March 2017.

SETTING

All trials registered in the database of ClinicalTrials.gov were screened. Large registered studies were received and studies focusing prospectively on the effects of antidepressants in mental health disorders. Specific data items were extracted automatically, and subsequently inspected, corrected and completed by hand.

PARTICIPANTS

Prospective studies were selected focusing on the effects of antidepressants in any mental health disorder with 800 participants or more planned for inclusion.

MAIN OUTCOME MEASURES

Three members from the study team independently assessed the following 'seeding trial' characteristics in each registered study: a high level of involvement of the product manufacturer in the study design, in the data analysis and reporting of the study, an abnormally low ratio of patient numbers to study site, spin and/or omissions of clinically relevant findings in the abstracts, and conclusions that focused on secondary endpoints and surrogate markers. Secondary outcomes were the exploration of a functional outcome and suicidality.

RESULTS

31 trials were identified from clinical trials database. 18/31 were published (58%). 8 of these 18 (44%) studies were identified as possible seeding trials. 13/31 (42%) large trials planned to explore functioning and 5/31 (16%) suicidality.

CONCLUSIONS

Large trials are rare in the field of antidepressant research. Some could be 'seeding trials'. Few explored suicidality. Identifying seeding trials from incomplete data entries in registries, especially when almost half of the studies were still unpublished, posed considerable challenges. The delay between our research and publication limits the strength of our conclusions.

PROSPERO REGISTRATION NUMBER

CRD42017065591.

Consistently Modest Antidepressant Effects in Clinical Trials: the Role of Regulatory Requirements

Despite being widely heralded following their discovery, the effectiveness and clinical utility of antidepressants has been questioned, in part due to the release of several decades of regulatory trial data. Upon investigation, contemporary regulatory trials of antidepressants have demonstrated a nearly identical effect size (0.3) for the past 40 years, regardless of placebo response or attempts to improve trial design. In this review, we examine the historical methods of antidepressant trials and re-evaluate regulatory trial data over time and according to drug class (SSRIs, SNRIs, and atypicals) with the addition of two classes of antidepressants not previously analyzed: tricyclics used as active comparators and the recently-approved NMDA receptor antagonist, esketamine. We show that among these five classes of antidepressants there were no significant differences between effect sizes or percent symptom reduction. We suggest that within the context of a regulatory trial of antidepressants, effect sizes will remain modest (~0.3) regardless of class or novel drug mechanism, possibly due to regulatory changes to trial design and conduct following the Kefauver-Harris Act of 1962. We comment that the regulatory double-blind, parallel, placebo-controlled trial model is an artificial creation for a narrow purpose-designed to demonstrate simple superiority over placebo and to determine basic safety. We should be cautious of stretching trial results beyond their limited capacity to inform clinical practice as trials are not representative of real-world patients or medication management practices. There is a substantial need to develop more realistic models to evaluate the clinical utility of antidepressants.

Identifying outcomes for depression that matter to patients, informal caregivers, and health-care professionals: qualitative content analysis of a large international online survey

BACKGROUND

Many clinical trials have assessed treatments for depressive disorders and bipolar depression. However, whether, and which, assessed outcome domains really matter to patients, informal caregivers, and health-care professionals remains unclear.

METHODS

We did an international online survey in French, German, and English. Participants were adult patients with a history of depression, informal caregivers, and health-care professionals, recruited by purposeful sampling. To identify outcome domains, participants answered four open-ended questions about their expectations for depression treatment. We disseminated the survey without restriction via social media, patient and professional associations, and a media campaign. Four researchers independently did qualitative content analyses. We assessed data saturation using mathematical models to ensure the comprehensive identification of outcome domains.

FINDINGS

Between April 5, 2018, and Dec 10, 2018, 1912 patients, 464 informal caregivers, and 627 health-care professionals from 52 countries provided 8183 open-ended answers. We identified 80 outcome domains related to symptoms (64 domains), such as mental pain (or psychological or psychic pain, 523 [17%] of 3003 participants) and motivation (384 [13%]), and functioning (16 domains), such as social isolation (541 [18%]). We identified 57 other outcome domains regarding safety of treatment, health care organisation, and social representation, such as stigmatisation (408 [14%]).

INTERPRETATION

This study provides a list of outcome domains important to patients, informal caregivers, and health-care professionals. Unfortunately, many of these domains are rarely measured in clinical trials. Results from this study should set the foundation for a core outcome set for depression.

FUNDING

Fondation pour la Recherche Medicale and NIHR Oxford Health Biomedical Research Centre.

Power behind the throne: A clinical trial simulation study evaluating the impact of controllable design factors on the power of antidepressant trials

OBJECTIVE

To evaluate the impact of controllable design factors on the power of antidepressants trials.

METHODS

Using clinical trial simulation (CTS), we analyzed the combined impact on the power of trials of controllable design factors (sample size, outcome metrics, and disease severity at inclusion) and uncontrollable parameters (heterogeneity of diseases labeled "depression" in the source population and selective effects of drugs on items of the Hamilton Depression Rating Scale [HDRS], the most used outcome measurement tool). We elaborated 3,840 scenarios calibrated with real data, particularly the publication bias-corrected effect size.

RESULTS

For an effect size of 0.26, simulations revealed that in trials with ≤650 participants, power was less than 80%. Among the tested outcome metrics, the "remission" outcome provided more robustness for sample heterogeneity, whereas the continuous outcome "HDRS changes" provided more robustness when investigating drugs with a selective effect on the HDRS items. For the "remission" outcome, the power of trials increased with increasing HDRS threshold at inclusion but decreased with the outcomes "response" and "HDRS changes. Drugs with a selective effect on the HDRS items could not reach the same power as for the reference drug.

CONCLUSION

Our study allows for drawing recommendations to avoid underpowered trials of antidepressants.