The Impact of Placebo Response Rates on Clinical Trial Outcome: A Systematic Review and Meta-Analysis of Antidepressants in Children and Adolescents with Major Depressive Disorder

Interpreting clinical trial outcomes complicated by placebo response with an assessment of false-negative and true-negative clinical trials in depression using propensity-weighting

The objective of this study was to evaluate the performances of the propensity score weighted (PSW) methodology in a post-hoc re-analysis of a failed and a negative RCTs in depressive disorders. The conventional study designs, randomizations, and statistical approaches do not account for the baseline distribution of major non-specific prognostic and confounding factors such as the individual propensity to show a placebo effect (PE). Therefore, the conventional analysis approaches implicitly assume that the baseline PE is the same for all subjects in the trial even if this assumption is not supported by our knowledge on the impact of PE on the estimated treatment effect (TE). The consequence of this assumption is an inflation of false negative results (type II error) in presence of a high proportion of subjects with high PE and an inflation of false positive (type I error) in presence of a high proportion of subjects with low PE value. Differently from conventional approaches, the inverse of the PE probability was used as weight in the mixed-effects analysis to assess TE in the PSW analysis. The results of this analysis indicated an enhanced signal of drug response in a failed trial and confirmed the absence of drug effect in a negative trial. This approach can be considered as a reference prospective or post-hoc analysis approach that minimize the risk of inflating either type I or type II error in contrast to what happens in the analyses of RCT studies conducted with the conventional statistical methodology.

A new method for analyzing clinical trials in depression based on individual propensity to respond to placebo estimated using artificial intelligence

One of the major reasons for trial failures in major depressive disorders (MDD) is the presence of unpredictable levels of placebo response as the individual baseline propensity to respond to placebo is not adequately controlled by the current randomization and statistical methodologies. The individual propensity to respond to any treatment or intervention assessed at baseline was considered as a major non-specific prognostic and confounding effect. The objective of this paper was to apply the propensity score methodology to control for potential imbalance at baseline in the propensity to respond to placebo in clinical trials in MDD. Individual propensity was estimated using artificial intelligence (AI) applied to observations collected in two pre-randomization occasions. Cases study are presented using data from two randomized, placebo-controlled trials to evaluate the efficacy of paroxetine in MDD. AI models were used to estimate the individual propensity probability to show a treatment non-specific placebo effect. The inverse of the estimated probability was used as weight in the mixed-effects analysis to assess treatment effect. The comparison of the results obtained with and without propensity weight indicated that the weighted analysis provided an estimate of treatment effect and effect size significantly larger than the conventional analysis.

Factors Related to Placebo Response in Randomized, Double-Blind Clinical Trials of Antidepressants in Children and Adolescents: A Meta-regression Analysis

BACKGROUND AND OBJECTIVE

Many randomized clinical trials (RCTs) for antidepressants in children and adolescents have failed to demonstrate efficacy due to a high placebo response. The aim of this study was to identify the potential factors affecting placebo response using meta-regression analysis of RCTs for antidepressants in children and adolescents using the Children's Depressive Rating Scale-Revised (CDRS-R) as the outcome.

METHODS

PubMed and ClinicalTrials.gov were searched for randomized, double-blind, placebo-controlled trials of antidepressants for the acute treatment of major depressive disorder in children and adolescents. The outcome used in the present study was the mean change of the CDRS-R total score from baseline to the last assessment for the primary efficacy in the placebo arm. Potential factors related to the placebo response, such as study design, operational, and patient factors, were explored using meta-regression.

RESULTS

The analyses included 23 trials. On multivariable meta-regression, setting up a placebo lead-in period was significantly associated with a smaller placebo response in the CDRS-R.

CONCLUSION

Setting up a placebo lead-in period should be considered in future clinical trials of antidepressants in adolescents and children.

The temporal trend of placebo response in migraine prevention from 1990 to 2021: a systematic literature review and meta-analysis with regression

BACKGROUND

Migraine affects 1.1 billion people globally and is the second leading cause of disability worldwide. In clinical trials, treatment efficacy is evaluated by comparing the differential responses in the treatment and placebo arms. Although placebo response in preventive migraine trials has been studied, there is limited research examining temporal trends. This study evaluates the trend of placebo response over thirty years in migraine prevention trials and investigates the association of potential confounders, such as patient, treatment, and study characteristics on placebo response using meta-analysis with regression.

METHODS

We conducted literature searches from January 1990 to August 2021 in bibliographical databases (PubMed, Cochrane Library, and EMBASE). Studies were selected according to PICOS criteria and included randomized, double-blind, placebo-controlled trials evaluating preventive migraine treatments in adult patients diagnosed with episodic or chronic migraine, with or without aura. The protocol was registered with PROSPERO (CRD42021271732). Migraine efficacy outcomes included were either continuous (e.g., monthly migraine days) or dichotomous (e.g., ≥ 50% responder rate (yes/no)). We assessed the correlation of the change in outcome from baseline in the placebo arm, with the year of publication. The relationship between placebo response and year of publication was also assessed after accounting to confounders.

RESULTS

A total of 907 studies were identified, and 83 were found eligible. For the continuous outcomes, the change from baseline in mean placebo response showed an increase over the years (rho = 0.32, p = 0.006). The multivariable regression analysis also showed an overall increase in placebo response over the years. The correlation analysis of dichotomous responses showed no significant linear trend between publication year and mean placebo response (rho = 0.08, p = 0.596). Placebo response also varied by route of administration.

CONCLUSION

Placebo response increased over the past 30 years in migraine preventive trials. This phenomenon should be considered when designing clinical trials and conducting meta-analyses.

Placebo response in trials with patients with anxiety, obsessive-compulsive and stress disorders across the lifespan: a three-level meta-analysis

QUESTION

Randomised controlled trials assessing treatments for anxiety, obsessive-compulsive and stress-related disorders often present high placebo response rates in placebo groups. Understanding the placebo response is essential in accurately estimating the benefits of pharmacological agents; nevertheless, no studies have evaluated the placebo response across these disorders using a lifespan approach.

STUDY SELECTION AND ANALYSIS

We searched MEDLINE, PsycINFO, Embase, Cochrane, websites of regulatory agencies and international registers from inception to 9 September 2022. The primary outcome was the aggregate measure of internalising symptoms of participants in the placebo arms of randomised controlled trials designed to assess the efficacy of selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) in individuals diagnosed with anxiety, obsessive-compulsive or stress-related disorders. The secondary outcomes were placebo response and remission rates. Data were analysed through a three-level meta-analysis.

FINDINGS

We analysed 366 outcome measures from 135 studies (n=12 583). We found a large overall placebo response (standardised mean difference (SMD)=-1.11, 95% CI -1.22 to -1.00). The average response and remission rates in placebo groups were 37% and 24%, respectively. Larger placebo response was associated with a diagnosis of generalised anxiety disorder and post-traumatic stress disorder, when compared with panic, social anxiety and obsessive-compulsive disorder (SMD range, 0.40-0.49), and with absence of a placebo lead-in period (SMD=0.44, 95% CI 0.10 to 0.78). No significant differences were found in placebo response across age groups. We found substantial heterogeneity and moderate risk of bias.

CONCLUSIONS

Placebo response is substantial in SSRI and SNRI trials for anxiety, obsessive-compulsive and stress-related disorders. Clinicians and researchers should accurately interpret the benefits of pharmacological agents in contrast to placebo response.

PROSPERO REGISTRATION NUMBER

CRD42017069090.

Placebo Response to Oral Administration in Osteoarthritis Clinical Trials and Its Associated Factors: A Model-Based Meta-analysis

IMPORTANCE

In osteoarthritis (OA) clinical trials, a placebo is often used as control. Therefore, a thorough understanding of the placebo response is important for guiding drug development in OA.

OBJECTIVE

To develop an oral placebo response model for OA.

DATA SOURCES

PubMed, EMBASE, and Cochrane Library databases were searched systematically from January 1, 1991, to July 2, 2022.

STUDY SELECTION

Randomized double-blind placebo-controlled trials of patients with primary OA were included. The interventions and placebo were administered orally. A total of 3032 trials were identified; of these, 130 (4.3%) met the inclusion criteria.

DATA EXTRACTION AND SYNTHESIS

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, dosage form of the placebo, sample size, proportion of patients who previously used nonsteroidal anti-inflammatory drugs, publication year, intervention categories, Kellgren-Lawrence grades, proportion of White patients, duration of pain, funding source, and risk of bias were extracted. A model-based meta-analysis was used to evaluate the time course of the placebo response in OA treatment and estimate the influencing factors. For subgroup analyses, a meta-analysis with a random-effects model was used to summarize the typical values of the model parameters and their SEs.

MAIN OUTCOMES AND MEASURES

The primary end point was the time course of the oral placebo response on the WOMAC pain, stiffness, and function subscale scores.

RESULTS

The 130 trials selected for analysis included 12 673 participants (mean age, 59.9 years; 68.9% women). The baseline scores of WOMAC pain, stiffness, and function subscales were found to be significantly associated with the placebo response. The placebo response reached 90% of its maximum response between 5 and 7 weeks. The placebo responses on the WOMAC subscales were also associated with the sample size, proportion of patients who had previously used nonsteroidal anti-inflammatory drugs, intervention drugs, and publication year.

CONCLUSIONS AND RELEVANCE

In this study, an oral placebo response model of OA was developed that may quantitatively describe the placebo response at different baseline levels of symptoms. The findings may provide valuable references for future clinical trial design and decision-making.

Controversies In The Pharmacotherapy Of Adolescent Depression

BACKGROUND

Although fluoxetine and, in the USA, escitalopram are approved for depression in adolescence, substantial concern surrounds antidepressant use in youth. Major controversies regarding efficacy and safety (increased suicidality).

INTRODUCTION

The cathegory of depression is very broad and overinclusive, in terms of etiology, role of psychosocial adversities severity, episodicity, presentation, relationship with bipolarity. This heterogeneity, not fully controlled considered in Randomized Controlled Trials (RCTs), may account for the disappointing results on both efficacy and safety.

METHOD

Based on the available literature, we will address the following topics: a) controversies regarding the definition of depression as a unique homogeneous condition with a unique type of pharmacological treatment; b) controversies about the interpretation of data from Randomized Controlled Trials (RCTs) on the efficacy of pharmacological treatments in adolescent depression; c) the interpretation of data regarding the safety of antidepressant treatment in adolescent depression, particularly in terms of increased suicidal risk.

RESULTS

According to RCTs, antidepressants are minimally to moderately more effective than placebo, principally based on very high placebo responses, and only fluoxetine showed more evidence of efficacy. These differences in meta-analyses are sometimes statistically, but not clinically significant. Depression is a heterogeneous condition in terms of etiology, role of psychosocial adversities severity, episodicity, presentation, relationship with bipolarity. This heterogeneity may partly explain the low drug-placebo difference and the high placebo response (possibly related to a high level of natural recovery of the adolescent depression). In the National Institute of Mental Health (NIMH)-funded studies, including a lower number of study sites and more reliable enrollment procedures, lower placebo response rates and greater group differences between medication and placebo were found. Robust evidence supports an increased risk of emergent suicidality after starting antidepressants. A clear age effect on suicidal risk after antidepressants is supported by a comprehensive meta-analysis, showing that suicidal risk increased with decreasing age, being markedly greater in subjects aged between 18 and 25 years. However, the term suicidality is too broad, as it includes suicidal ideation, suicidal attempts, and completed suicide, with a hugely wide range of severity and pervasiveness. If emergent suicidality should be actively and carefully explored, empirical evidence, albeit weak, suggests that combined pharmacotherapy (antidepressant and/or lithium) associated with psychotherapy may be helpful in reducing pretreatment suicidal ideation and suicidal risk.

DISCUSSION

Moderate to severe depression should be treated with psychotherapy and/or fluoxetine, the best-supported medication, and treatment-resistant adolescents should always receive combined treatment with psychotherapy. Suicidal ideation, particularly with a plan, should be actively explored before starting an antidepressant, as a reason for the closest monitoring. Emergent suicidality after starting antidepressants, as well as antidepressant-related activation, should also be closely monitored and may lead to antidepressant discontinuation. Although no response to pharmacotherapy and psychotherapy may occur in up to 40% of depressed adolescents, possible predictors or mediators of poorer response in adolescents are uncertain, and only a few studies support possible treatment strategies. Finally, studies exploring the efficacy of antidepressants in specific depression subtypes, i.e., based on prevalent psychopathological dimensions (apathy, withdrawal, impulsivity), are warranted.

Antidepressants in children and adolescents with major depressive disorder and the influence of placebo response: A meta-analysis

BACKGROUND

There are few available antidepressants for pediatric Major Depressive Disorder (MDD). The objective of this systematic review and meta-analysis was to review industry-funded studies of antidepressants in children and adolescents with MDD, and to better understand the contribution of study design and placebo response to the findings of these studies.

METHODS

Randomized, double-blind, placebo-controlled clinical trials that compared antidepressant with placebo for the acute treatment of MDD in children and/or adolescents were selected. Estimates of the standardized mean difference (SMD) in change in Children's Depression Rating Scale-Revised scores were pooled, after examining for heterogeneity. A random-effects meta-analysis was completed.

RESULTS

Thirty-four antidepressant-placebo comparisons, involving 6161 subjects, were included. The SMD among all studies was 0.12 (CI 0.08, 0.17; p < 0.001), a very small effect size, lower than that seen in studies of adults with MDD. When the meta-analysis was limited to studies with a low mean placebo response, the SMD increased to 0.19 and further increased to 0.22 when studies with at least a 50% chance of receiving placebo were included.

LIMITATIONS

Many studies focused on older children and younger adolescents. Our findings may not reflect antidepressant efficacy in older adolescents.

CONCLUSIONS

The modest SMD identified in this analysis may reflect study design factors and the application of antidepressants developed for adults to pediatric patients. Given the urgent clinical need for more pediatric MDD treatments, the influence of placebo response and the need for drug development tailored to this population should be considered in pediatric MDD trial design.

PATENCY-2 trial of vonapanitase to promote radiocephalic fistula use for hemodialysis and secondary patency

OBJECTIVE

Arteriovenous fistulas created for hemodialysis often fail to become usable and are frequently abandoned. This prospective trial evaluated the efficacy of vonapanitase, a recombinant human elastase, in increasing radiocephalic fistula use for hemodialysis and secondary patency.

METHODS

PATENCY-2 was a randomized, double-blind, placebo-controlled trial in patients on or approaching the need for hemodialysis undergoing radiocephalic arteriovenous fistula creation. Of 696 screened, 613 were randomized, and 603 were treated (vonapanitase n = 405, placebo n = 208). The study drug solution was applied topically to the artery and vein for 10 min immediately after fistula creation. The primary endpoints were fistula use for hemodialysis and secondary patency (fistula survival without abandonment). Other efficacy endpoints included unassisted fistula use for hemodialysis, primary unassisted patency, fistula maturation and unassisted maturation by ultrasound criteria, and fistula procedure rates.

RESULTS

The proportions of patients with fistula use for hemodialysis was similar between groups, 70% vonapanitase and 65% placebo, (p = 0.33). The Kaplan-Meier estimates of 12-month secondary patency were 78% (95% confidence interval [CI], 73-82) for vonapanitase and 76% (95% CI, 70-82) for placebo (p = 0.93). The proportions with unassisted fistula use for hemodialysis were 46% vonapanitase and 37% placebo (p = 0.054). The Kaplan-Meier estimates of 12-month primary unassisted patency were 50% (95% CI, 44-55) for vonapanitase and 43% (95% CI, 35-50) for placebo (p = 0.18). There were no differences in the proportion of patients with fistula maturation or in fistula procedure rates. Adverse events were similar between groups. Vonapanitase was not immunogenic.

CONCLUSIONS

Vonapanitase treatment did not achieve clinical or statistical significance to meaningfully improve radiocephalic fistula surgical outcomes. Outcome in the placebo group were better than in historical controls. Vonapanitase was well-tolerated and safe.

TRIAL REGISTRATION

clinicaltrials.gov: NCT02414841 (https://clinicaltrials.gov/ct2/show/NCT02414841).

Beyond Amitriptyline: A Pediatric and Adolescent Oriented Narrative Review of the Analgesic Properties of Psychotropic Medications for the Treatment of Complex Pain and Headache Disorders

Children and adolescents with recurrent or chronic pain and headache are a complex and heterogenous population. Patients are best served by multi-specialty, multidisciplinary teams to assess and create tailored, individualized pain treatment and rehabilitation plans. Due to the complex nature of pain, generalizing pharmacologic treatment recommendations in children with recurrent or chronic pains is challenging. This is particularly true of complicated patients with co-existing painful and psychiatric conditions. There is an unfortunate dearth of evidence to support many pharmacologic therapies to treat children with chronic pain and headache. This narrative review hopes to supplement the available treatment options for this complex population by reviewing the pediatric and adult literature for analgesic properties of medications that also have psychiatric indication. The medications reviewed belong to medication classes typically described as antidepressants, alpha 2 delta ligands, mood stabilizers, anti-psychotics, anti-sympathetic agents, and stimulants.