Meta-regression to explain the placebo effects in clinical trials of anti-CGRP monoclonal antibodies for migraine prevention

• Published in: Journal of medical economics 2023-12, Vol.26 (1), p.1072-1080
• Main Authors: Regnier, Stephane Alexandre, Lee, Xin Ying
• Format: Article
• Language: English
• ISSN: 1369-6998; 1941-837X
• DOI: 10.1080/13696998.2023.2248842

Background: Commonly used methods of comparison (e.g. network meta-analyses) require common comparator(s) across trials, such as placebo in placebo-controlled trials. Recent literature indicates that route of administration differences across placebo arms of clinical trials in pain disorders may contribute to differences in placebo effect.Methods: We conducted a meta-regression on placebo data from pivotal clinical trials of anti-calcitonin gene-related peptide (anti-CGRP) monoclonal antibodies for migraine prevention to quantify the impact of route of administration, migraine type (episodic/chronic), and number of prior treatment failures on placebo reduction in monthly migraine days (MMDs) across weeks 1-12 of treatment. A systematic literature review of Embase, MEDLINE, the Cochrane Library, and grey literature conducted in June 2021 identified 14 relevant, randomized placebo-controlled trials for analysis.Results: After testing models with different covariates, a meta-regression was fitted to the extracted placebo data with the covariates of route of administration, migraine type, and proportion of patients with ≥2 prior preventive treatment failures. An intravenous route of administration for the placebo arm was a predictor for higher MMD reduction. Predictors of lower MMD reduction were migraine type (episodic migraine) and a higher proportion of patients having ≥2 failed preventive treatments.Conclusions: The efficacy of intravenous anti-CGRP monoclonal antibodies are likely underestimated, and differences in the route of administration of placebo may necessitate use of alternative methods that do not assume the presence of a common comparator when comparing anti-CGRP monoclonal antibodies in migraine prevention. Further research into the contextual effects of the placebo effect is warranted.