All four anti-CGRP monoclonal antibodies showed consistently high efficacy for chronic migraine prevention (NNT 5-8), while Botox showed no significant benefit (NNT 56) in this indirect comparison meta-analysis.
NNT 5-8 vs. NNT 56Anti-CGRP antibodies need only 5-8 patients treated for one to achieve 50% migraine reduction, while Botox requires treating 56 patients — a dramatic difference that challenges current step-therapy requirements.
What the researchers found
All four anti-CGRP monoclonal antibodies demonstrated invariably high and consistent efficacy, with NNTs (number needed to treat) ranging from 5 to 8 for achieving a 50% reduction in monthly migraine days. This means that for every 5-8 patients treated, one additional patient achieves meaningful improvement compared to placebo.
In contrast, onabotulinumtoxin A (Botox) showed a non-significant absolute risk difference with an NNT of 56 — meaning far more patients need treatment to achieve the same benefit. Topiramate results were contradictory between its two included studies (NNTs of 2 and 22). Safety profiles were similar across all treatments, with no significant differences in serious adverse events or study dropout rates among anti-CGRP mAbs.
Why it matters
Chronic migraine affects about 2% of the global population and is among the most disabling conditions worldwide. Until anti-CGRP antibodies arrived, treatment options were limited to repurposed drugs (topiramate, an epilepsy drug) and Botox injections. This analysis provides the first systematic indirect comparison showing that anti-CGRP antibodies are more consistently effective than these established treatments. The NNT metric is particularly useful for clinicians and patients making real-world treatment decisions.
How the study worked
Researchers searched MEDLINE and CENTRAL databases for phase 2b and phase 3 randomized controlled trials evaluating chronic migraine prophylaxis. Eight RCTs met inclusion criteria. Rather than pooling different drugs together, the authors used absolute risk difference (ARD) as the primary metric — a measure that directly translates into NNT and NNH (number needed to harm). This cross-trial indirect comparison approach was used because no head-to-head trials exist between anti-CGRP antibodies and standard treatments.
What this study cannot tell us
This is an indirect comparison rather than a direct head-to-head trial, which introduces the possibility that differences between study populations, designs, and endpoints could confound the results. Only eight RCTs were included, and the small number of topiramate trials (2) produced contradictory results, limiting conclusions about that drug. The Botox studies used different trial designs than the CGRP antibody studies. The analysis does not account for long-term efficacy, cost-effectiveness, or patient preference factors.
How to read the evidence
This is a meta-analysis of phase 2b and 3 RCTs using rigorous statistical methods (absolute risk difference). However, the indirect comparison design (no head-to-head trials available) introduces cross-trial confounding. The consistency of anti-CGRP results across multiple studies strengthens confidence in those findings, while the contradictory topiramate results and singular Botox trial comparison weaken conclusions for those drugs.
When this study was published
Published in 2024, this analysis captures the current evidence base for chronic migraine prophylaxis. Head-to-head trials between anti-CGRP antibodies and established treatments may emerge in coming years to provide more definitive comparisons.
The bigger picture
This meta-analysis arrives as anti-CGRP antibodies are reshaping chronic migraine management but face barriers of high cost and insurance prior authorization requirements (often requiring patients to fail other treatments first). The finding that Botox — a widely used and insurance-required step therapy — showed an NNT of 56 compared to 5-8 for anti-CGRP antibodies challenges the step-therapy model and could influence guidelines and reimbursement policies. The consistency of results across all four anti-CGRP antibodies also suggests the class effect is robust.
Questions still open
- Should anti-CGRP antibodies become first-line preventive therapy for chronic migraine rather than requiring failure of older treatments first?
- Why did Botox show such poor efficacy in this indirect comparison when it remains widely used clinically — is the trial design or patient population different?
- Are there chronic migraine subgroups who respond better to Botox or topiramate than to anti-CGRP antibodies?
Common questions
What does 'NNT 5-8' mean for chronic migraine treatment?
Should I switch from Botox to an anti-CGRP antibody for my chronic migraines?
Read the original research
A Risk-Difference Meta-Analysis for the Prophylactic Treatments of Chronic Migraine.
Cureus, 16(6), e62458
Citation
Kodounis, Michalis; Constantinidis, Theodoros S; Rizonaki, Konstantina; Drakou, Eleni; Zintzaras, Elias; Stefanidis, Ioannis; Mitsikostas, Dimos-Dimitrios; Dardiotis, Efthimios. (2024). A Risk-Difference Meta-Analysis for the Prophylactic Treatments of Chronic Migraine.. Cureus, 16(6), e62458. https://doi.org/10.7759/cureus.62458