Factors Influencing Placebo Responses in Rheumatoid Arthritis Clinical Trials: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Studies

The lessebo effect in randomized controlled trials of rituximab in patients with rheumatoid arthritis: a meta-analysis

OBJECTIVE

The goal of this study was to assess the impact of negative expectations associated with receiving a placebo (the lessebo effect) on efficacy outcomes in randomized clinical trials (RCTs) of rituximab in patients with rheumatoid arthritis (RA).

METHODS

We performed a meta-analysis on the American College of Rheumatology 20%, 50%, and 70% (ACR20, 50, 70) response rates in the placebo and active (biosimilar)-controlled groups (reference-pbo and reference-bs) of rituximab showing an insufficient response to methotrexate or tumor necrosis factor. We evaluated the difference in ACR20, 50, 70 response rates between the two groups (reference-bs vs. reference-pbo).

RESULTS

Nine RCTs included a total of 2734 patients with RA. The pooled incidence of ACR20 response rate in the placebo- and active-controlled groups of the rituximab RCTs for RA was 53.1% (95% confidence interval [CI] 49.9-56.3%) and 75.0% (95% CI 71.2-78.4%), respectively. The difference in the ACR20 response rate between the placebo- and active-controlled groups was -20.9% (95% CI -26.9 to 61.9%, p < 0.001). The pooled incidence of ACR50 response rate in the placebo- and active-controlled groups of the rituximab RCTs for RA was 29.0% (95% CI 26.2-32.0%) and 47.4% (95% CI 43.2-51.6%), respectively. The ACR50 response rates were significantly higher in the active-controlled groups than in the placebo-controlled groups (-18.4%; 95% CI -18.4 to -13.4%, p < 0.001). The difference in the ACR70 response rate between the placebo- and active-controlled groups was -14.9% (95% CI -22.2 to -7.6%, p < 0.001). The ACR20, 50, 70 response rates were significantly higher in the active-controlled groups than in the placebo-controlled group.

CONCLUSION

This study shows that the use of a placebo can be associated with a clinically significant reduction in the magnitude of change of the ACR20, 50, 70 response rates in rituximab RCTs for RA. The lessebo effect has potential implications for the development of new treatments and appraisal of current treatment options for RA.

Identifying Factors Associated With Treatment Response in Rheumatoid Arthritis Clinical Trials

Objective

Despite a wealth of studies evaluating rheumatoid arthritis (RA) therapies, it remains difficult to compare efficacies across trials due to heterogeneous study populations. We sought to identify patient/trial characteristics associated with clinical response to enable fairer comparisons.

Methods

We reviewed 565 disease‐modifying antirheumatic drug studies compiled for American College of Rheumatology (ACR) management guidelines. Seventy‐two articles on randomized controlled phase II/III trials from 1995 to 2018 reporting the proportion of patients achieving 20%, 50% or 70% improvement in the ACR's RA disease score (ACR20/50/70) or Disease Activity Score‐28 with erythrocyte sedimentation rate or C‐reactive protein (DAS28‐ESR or DAS28‐CRP) with follow‐up more than 3 months were included. We explored associations between 34 patient/trial characteristics and ACR responses. We constructed multivariable models using these factors to compute expected response rates and to compare observed with expected response rates across therapies.

Results

Among eligible clinical trials, later publication year, baseline DAS28‐CRP score, methotrexate/biologic naivety, baseline ESR, follow‐up of 52 weeks or more, number of subjects enrolled, and anticitrullinated peptide antibody seropositivity were associated with greater ACR response. Greater age, longer disease duration, higher baseline Sharp score, and steroid use were associated with lower response rates. Predictive models incorporating these factors explained 29%, 37%, and 53% of variance in ACR20, ACR50, and ACR70, respectively. Overall, comparing observed versus expected rates of response across trials more closely approximated results of head‐to‐head trials. For example, although observed responses numerically favored adalimumab to tofacitinib, comparison of observed versus expected results across trials more closely approximated the results from a head‐to‐head trial (“Oral Rheumatoid Arthritis triaL [ORAL] Strategy”).

Conclusion

We identified factors associated with ACR response in RA trials. Adjusting for expected outcomes yielded therapy comparisons somewhat more similar to head‐to‐head trials. These findings could inform other across‐trial comparisons, particularly when head‐to‐head trials are lacking.

Impact of pre-existing background therapy on placebo responses in randomised controlled clinical trials of rheumatoid arthritis

OBJECTIVES

Various hypotheses exist for the explanation of placebo response rates in randomised controlled trials (RCTs) of patients with rheumatoid arthritis with IR to methotrexate (MTX). We hypothesised that placebo responses may be related to more consequent intake of MTX during the tightly monitored trial period.

METHODS

We conducted a post hoc analysis of placebo-treated patients included in two RCTs that had allowed inclusion of patients with and without ongoing MTX: the GO-AFTER and the SIRROUND-T trials. We pooled placebo patients of both trials and compared American College of Rheumatology (ACR) 20%/50%/70% response rates and Clinical Disease Activity Index (CDAI) low disease activity (LDA; ie, CDAI ≤10) responses between those receiving placebo on top of continued MTX and those receiving placebo without any background disease modifying antirheumatic drugs (DMARDs).

RESULTS

Of 398 placebo patients, 285 continued MTX and 113 had no background DMARDs. Baseline characteristics were similar. At week 16, ACR20 response was achieved by 72/285 (25.3%) of placebo+continued MTX and 14/113 (12.4%) of placebo only patients (nominal p=0.005); for ACR50 these numbers were 25/285 (8.4%) versus 1/113 (0.9%; nominal p=0.003) and for ACR70 they were 8/285 (2.8%) versus 0/113 (0%; nominal p=0.112). Also, more patients with placebo+continued MTX achieved CDAI-LDA at week 16 (25/285; 8.8%) compared with placebo only (2/113; 1.8%; nominal p=0.013).

CONCLUSION

Clinical responses to placebo are higher in patients who continue an insufficient MTX background therapy. This suggests an inadvertently more consequent intake of background therapy during the trial. Background therapy should therefore be effectively aligned before enrollment into a clinical trial.

Safety and efficacy of elsubrutinib or upadacitinib alone or in combination (ABBV-599) in patients with rheumatoid arthritis and inadequate response or intolerance to biological therapies: a multicentre, double-blind, randomised, controlled, phase 2 trial

BACKGROUND

ABBV-599 is a novel fixed-dose combination of the Bruton's tyrosine kinase (BTK) inhibitor elsubrutinib and the Janus kinase (JAK) inhibitor upadacitinib under investigation for the treatment of autoimmune diseases. We aimed to determine whether ABBV-599 could increase the treatment response for patients with active rheumatoid arthritis compared with inhibiting either pathway alone, while maintaining an acceptable safety profile.

METHODS

We conducted a multicentre, double-blind, parallel-group, dose-exploratory, randomised, controlled, phase 2 trial at 75 community sites in eight countries in Europe and North America. We enrolled patients who were 18 years or older with rheumatoid arthritis and inadequate response or intolerance to biological disease-modifying antirheumatic drugs. Eligible patients were randomly assigned (3:2:2:2:2:1) via interactive response technology to receive daily, orally administered ABBV-599 (ie, upadacitinib 15 mg plus elsubrutinib 60 mg), elsubrutinib 60 mg, elsubrutinib 20 mg, elsubrutinib 5 mg, upadacitinib 15 mg, or placebo. Randomisation was stratified by the number of previous biological disease-modifying antirheumatic drugs. The investigator, study site personnel, and patients were masked throughout the study. The primary endpoint was change from baseline in disease activity score of 28 joints with C-reactive protein (DAS28-CRP) at week 12 for all patients who received a study drug. Pharmacokinetics and safety were also assessed. This study is registered with ClinicalTrials.gov, number NCT03682705.

FINDINGS

Between Oct 8, 2018, and March 26, 2020, 242 patients were randomly assigned to receive ABBV-599 (n=62), elsubrutinib 60 mg (n=41), elsubrutinib 20 mg (n=39), elsubrutinib 5 mg (n=41), upadacitinib 15 mg (n=40), or placebo (n=19). Of the 242 patients, 204 (84%) were female, 38 (16%) were male, and 220 (91%) were White; the mean age at baseline was 58·0 years (SD 11·3). Compared with placebo, the least squares mean changes from baseline in DAS28-CRP were -1·44 (90% CI -2·03 to -0·85; p<0·0001) for ABBV-599, -0·40 (-1·03 to 0·23; p=0·29) for elsubrutinib 60 mg, -0·20 (-0·85 to 0·44; p=0·61) for elsubrutinib 20 mg, -0·21 (-0·84 to 0·41; p=0·57) for elsubrutinib 5 mg, and -1·75 (-2·38 to -1·13; p<0·0001) for upadacitinib. No significant improvements in efficacy measures for elsubrutinib alone (any dose) versus placebo were detected, despite adequate plasma exposure and target engagement. Treatment-emergent adverse events were observed in 113 (47%) of 242 patients, with similar proportions for all groups.

INTERPRETATION

Significant improvements in disease activity metrics of rheumatoid arthritis with ABBV-599 were driven by the JAK inhibitor upadacitinib with no discernible effect by the BTK inhibitor elsubrutinib.

FUNDING

AbbVie.

Placebo response in psoriatic arthritis clinical trials: a systematic review and meta-analysis

OBJECTIVE

To determine the placebo response rate in psoriatic arthritis (PsA) randomised clinical trials (RCTs), its contributing factors, and impact on the effect size of active treatments.

METHODS

We searched multiple databases, from inception to December 20, 2020, for placebo-controlled RCTs in PsA. We used a random-effects meta-analysis to pool the response rates for the American College of Rheumatology 20 (ACR20) criteria in the placebo arm, determined the risk difference for treatment vs placebo, and used meta-regression to determine the factors associated with placebo response rates. The risk of bias was assessed in duplicate. PROSPERO: CRD42021226000.

RESULTS

We included 42 RCTs (5,050 patients receiving placebo) published between 2000 and 2020; The risk of bias was low in 28 trials, high in four, and with some concerns in ten. The pooled placebo response rate was 20.3% (95% CI, 18.6% to 22.1%; predicted intervals, 11.7%-29.0%), with significant between-trial heterogeneity (I2=56.8%, p< 0.005). The pooled risk difference for treatment vs placebo was 27% (95%CI, 24% to 31%). In the multivariable meta-regression, there was a 15% (95% CI, 2.9% to 29.8%) increase in the odds of achieving the placebo response for each five-year increment in publication year (p= 0.016). In addition, the active treatment risk difference decreased for every five-year increment in publication year (β = -0.053; 95% CI -0.099 to -0.007; p= 0.024) but was not associated with the placebo response.

CONCLUSION

Despite increasing over time, the placebo response for ACR20 in PsA RCTs was not associated with the active treatment effect size.

The response to TNF blockers depending on their comparator in rheumatoid arthritis clinical trials: the lessebo effect, a meta-analysis

OBJECTIVE

To compare the effect of the biological reference agents (infliximab, etanercept, adalimumab) in rheumatoid arthritis (RA) in pivotal superiority placebo-controlled trials (reference agent vs placebo) vs their effect in equivalence active comparator-controlled trials (reference agent vs biosimilar).

METHODS

The PubMed, EMBASE, Cochrane, databases were searched for randomized, double-blind, controlled trials up to March 2020 comparing a biological reference agent vs placebo or biosimilar. The study assessed the American College of Rheumatology (ACR) 20/50/70 responses of the reference agent in these groups (Reference-pbo and Reference-bs, respectively). The effect of the reference agent in both groups was estimated with 95% confidence intervals (95%CI), pooled using random-effects models and then compared using a meta-regression model.

RESULTS

We included 31 trials. The main characteristics of the population (disease duration and activity, % seropositivity and methotrexate dose) of the population in both groups were similar. The meta-analysis found a better ACR20 response to the biological originator in the Reference-bs group with a global rate of 70% (95%CI, 66-74) compared with 59% (95%CI, 55-62) in the reference-pbo group (p= 0.001). A significant difference was also found for ACR 50 [44% (95%CI, 39-50) vs 35% (95%CI, 31-39) respectively, p< 0.01].

CONCLUSION

Effect of the reference biologic agent was better when compared with an active drug to a placebo. This could be linked to an increased placebo effect in active comparator-controlled studies or a nocebo effect in placebo-controlled studies. This effect can be called the Lessebo effect.