Reviews/Anti CGRP Antibodies/Erenumab tolerability versus topiramate
Comparative Efficacy · CGRP-CE-01 · v2
Borderline: within 4 points of the Established/Likely boundary, so a re-grade could land either side.
One large, carefully designed head-to-head trial directly compared erenumab against topiramate for preventing migraine, and it was built specifically to measure how well patients tolerate each drug [1]. Far fewer people stopped erenumab because of side effects than stopped topiramate, which was the main outcome the trial set out to measure. A follow-up look at the same trial found that more erenumab patients stayed on their treatment [20], and a separate trial comparing erenumab against a mix of older oral drugs pointed the same way [18]. Because the direct topiramate comparison comes from a single trial run entirely in Germany, the panel judged the claim well supported but held it short of the strongest tier. No second independent trial comparing these two drugs head-to-head exists in this evidence set.
A dedicated head-to-head phase 4 randomised trial [1] with tolerability as its pre-specified primary endpoint found 10.6% of erenumab patients discontinued medication due to an adverse event versus 38.9% on topiramate (odds ratio 0.19, p < 0.001). A post-hoc analysis of the same trial [20] reported that more erenumab patients completed on study medication (85.9% vs 59.5%), reflecting the same tolerability gap. An independent active-controlled trial [18] comparing erenumab against nonspecific oral preventives found fewer erenumab patients discontinued for adverse events (2.9% vs 23.3%), corroborating the direction though not isolating topiramate. All corroboration is either within the same trial family [20], [21] or against a mixed comparator [18]. The contested point: The direct erenumab-versus-topiramate finding rests on a single trial family: [20] and [21] are post-hoc analyses of HER-MES [1] rather than independent replications. The only other comparative randomised trials either use a mixed oral-preventive comparator [18] or test a different molecule, atogepant [24], rather than erenumab.
All 36 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The topiramate-specific verdict rests on a single trial: HER-MES [1], with [20] and [21] being post-hoc analyses of the same study rather than independent replications.
No independent erenumab-vs-topiramate replication exists in the corpus: [18] (APPRAISE) uses a mixed oral-preventive comparator rather than topiramate alone, and [24] (TEMPLE) tests atogepant, a different molecule.
Where it remains uncertain. The topiramate-specific result comes from one German trial family [1], [20], [21]; no independent erenumab-versus-topiramate replication exists, and the nearest comparative trials use a mixed comparator [18] or a different drug [24].
Aleatory
Whether any given patient tolerates either drug varies person to person; the trial reports group discontinuation rates [1], not individual-level outcomes.
Epistemic
Only one trial family [1], [20], [21] directly compares the two drugs; a second independent head-to-head trial would reduce this gap.
Inferential
Tolerability is inferred from discontinuation due to adverse event alone [1]; no alternative tolerability measure triangulates the direct comparison.
The load-bearing papers from a corpus of 36, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Primary-endpoint direct evidence of superior erenumab tolerability versus topiramate.
“The primary endpoint was medication discontinuation due to an adverse event during the double-blind phase.”
Panel auditInternal validity: high · scope of inference: Adults with ≥4 migraine days/month naïve to both study drugs, over 24 weeks, in Germany.Key limitations: single-country (Germany) · treatment-naïve population only · 24-week horizon
Independent active-controlled RCT showing the same tolerability advantage of erenumab over oral preventives (topiramate included in the comparator basket).
“discontinued treatment due to adverse events (12 of 408 [2.9%] vs 48 of 206 [23.3%])”
Panel auditInternal validity: high · scope of inference: Erenumab versus oral preventives as a class in episodic migraine after 1-2 prior failures.Key limitations: topiramate not isolated · open-label · class-level comparator
Within-trial corroboration: higher on-treatment completion for erenumab reflects the tolerability gap.
“Of these, 334 patients (85.9%) receiving erenumab, and 231 patients (59.5%) receiving topiramate completed the DBTP on study medication.”
Panel auditInternal validity: high · scope of inference: Comparative efficacy of erenumab versus topiramate in HER-MES completers.Key limitations: efficacy endpoint not tolerability · post hoc · completion gap not attributed
Outcomes are HIT-6 and SF-36v2, not adverse-event or discontinuation tolerability measures.
Panel auditInternal validity: high · scope of inference: Comparative headache impact and quality of life for erenumab versus topiramate.Key limitations: QoL endpoint not tolerability · post hoc · no adverse-event data
4 of 36 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
A large head-to-head RCT with tolerability as the primary endpoint carries the claim directly, but the absence of independent erenumab-vs-topiramate replication caps confidence at Likely.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Independent head-to-head replication. The direct comparison rests on a single trial family [1], [20], [21], all from Germany, with no independent erenumab-versus-topiramate replication in the corpus. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: An independent, multi-country, double-blind erenumab-versus-topiramate trial with adverse-event discontinuation as the primary endpoint.
Open question: Does the erenumab-over-topiramate tolerability advantage replicate in an independent trial outside Germany? Why it is still open: The direct comparison exists only in the single German HER-MES trial family [1], [20], [21].
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19