Xeomin Migraine Phase III: Enrollment Milestone Masks Unresolved Efficacy and Episodic Precedent Risk

Merz Completes Phase III Enrolment for Xeomin in Migraine Prevention

Merz Therapeutics has successfully completed patient enrolment for its MINT-C and MINT-E global Phase III clinical trials, evaluating Xeomin (incobotulinumtoxinA) for the prevention of chronic and episodic migraine in adults. The studies enrolled approximately 1800 participants across 109 investigation sites in Europe and North America, achieving this milestone six months ahead of schedule. The primary outcome measures the change in monthly migraine days from baseline to month six, with secondary endpoints assessing monthly headache days, acute medication days, and migraine frequency. The main study period is expected to conclude during the coming year, with results guiding future clinical and regulatory decisions.

• Merz Therapeutics has completed patient enrolment for its MINT-C and MINT-E Phase III trials, involving approximately 1800 participants across 109 sites in Europe and North America. This significant milestone was achieved six months ahead of the initial schedule, underscoring the efficient execution of the global clinical program for Xeomin in migraine prevention.
• The trials are designed to assess the safety and efficacy of Xeomin, with the primary outcome focusing on the change in monthly migraine days from baseline to month six. Key secondary endpoints include evaluating differences in monthly headache days, acute medication days, and migraine frequency across two-week periods at the conclusion of each injection cycle, providing a comprehensive view of the drug's potential benefits.
• The completion of enrolment is a critical step, with the main study period anticipated to finish next year, followed by data analysis to inform future clinical and regulatory strategies for Xeomin in migraine prevention. Currently, Xeomin holds regulatory approvals in over 80 countries for various aesthetic and neurological indications, such as cervical dystonia, spasticity, and blepharospasm, but is not yet approved for migraine prevention.

MINT-C and MINT-E: Designing Xeomin's Path in Migraine Prevention

Several randomized, controlled trials have evaluated preventive and acute migraine therapies across chronic and episodic migraine populations, employing diverse designs, dosing regimens, and endpoint frameworks. The studies below span pharmacological classes including CGRP-pathway agents, anticonvulsants, and gepants, providing a cross-sectional view of trial methodology in this therapeutic area.

Addressing the Unmet Needs in Chronic and Episodic Migraine

Migraine management remains constrained by significant gaps in both acute and preventive treatment paradigms, affecting patients across the episodic and chronic spectrum. Despite therapeutic advances, poor adherence, tolerability issues, and incomplete efficacy continue to limit outcomes, while access barriers and underdiagnosis compound the clinical burden.

• Adherence and tolerability of preventive therapies: Conventional oral preventives — including beta-blockers, tricyclics, antiepileptics, and botulinum toxin — are associated with poor tolerability and low adherence. Pooled 12-month adherence for anti-CGRP monoclonal antibodies (mAbs) is approximately 55%, compared with approximately 35% for oral preventives, yet discontinuation due to adverse events with anti-CGRP mAbs still ranges from 5.9%–20%, most commonly constipation and injection-site reactions.

• Incomplete efficacy across patient subgroups: Responder rates (≥50% reduction in monthly migraine days) for anti-CGRP mAbs improve from 44% at three months to 64% at 12 months, but a substantial proportion of patients do not respond. In patients with chronic migraine and medication overuse headache, chronic migraine status and multiple failures from prior preventive medication classes are independently associated with poor galcanezumab response. Patients with new daily persistent headache achieve a ≥30% improvement in monthly moderate-to-severe headache days in only 23% of cases with CGRP mAbs, compared with 46% in daily chronic migraine and 84% in non-daily chronic migraine.

• Medication overuse headache (MOH) as a compounding barrier: Medication overuse has a prevalence of 0.5–2.0% and contributes directly to migraine chronification. Frequent use of symptomatic headache medication drives the transition from episodic to chronic migraine, and a high relapse rate is observed particularly in patients with opioid overuse. Monthly consumption of pain medication has been identified as the only baseline prognostic factor in multivariate analysis for MOH outcomes.

• Cardiovascular and safety constraints limiting prescribing: Triptans carry cardiovascular risks and vasoconstrictive properties that restrict their use in broader patient populations. While gepants lack vasoconstrictive properties, first-generation CGRP receptor antagonists were not fully developed due to hepatotoxicity. Erenumab has been associated with hypertension, and CGRP antagonists should be used with caution in patients with small vessel disease, given that vasodilation may be an important CGRP-mediated mechanism mid-ischemia. Long-term cardiovascular safety data remain insufficient.

• Limited long-term safety and evidence beyond 12 months: Further research is needed to assess long-term safety of anti-CGRP mAbs beyond 12 months, cost-effectiveness, and use in special populations such as pregnancy. Current guidelines recommend discontinuation after 12–18 months due to limited long-term data, despite real-world evidence suggesting sustained reductions in monthly headache days and medication overuse at 2, 3, and 4 years.

• Access, underdiagnosis, and prescriber knowledge gaps: General practitioners are not always educated about migraine, and specialists are few and often difficult to reach. Polytherapy is strongly not recommended but remains common practice because treatment is not optimized. Prophylactic therapy is recommended in cases of four or more headaches per month, eight or more headache days per month, debilitating headaches, and medication-overuse headaches, yet preventive treatment is often not chosen appropriately.

• Evidence gaps in specific populations and headache subtypes: Evidence for topiramate, valproate, and propranolol in chronic migraine mostly carries high risk of bias. In pediatric episodic migraine, topiramate, divalproex, and clonidine were no more effective than placebo in preventing migraines, and long-term preventive benefits and improvement in disability and quality of life remain unknown. Predictive models for identifying patients at risk of medication overuse or MOH remain limited, with all available studies demonstrating a high risk of bias in model construction.

Xeomin's Established Safety Profile and Future in Migraine

A pooled analysis of Merz-sponsored, placebo-controlled, and repeat-dose studies examined the incidence of treatment-emergent adverse events (TEAEs) across adult neurological indications — cervical dystonia, blepharospasm, limb spasticity, sialorrhea, and essential tremor of the upper limb. After a single injection cycle, overall TEAE incidences were similar between incobotulinumtoxinA and placebo in most indications, though between-indication differences were observed. Few TEAEs led to discontinuation, and no fatal TEAEs were recorded with incobotulinumtoxinA. Critically, repeated treatment cycles did not increase the incidence of any event, supporting a stable long-term tolerability profile. The most frequent treatment-related TEAEs were indication-dependent; dysphagia was predominant for indications affecting the head or neck, while the treatment-related TEAEs of special interest across all indications were most commonly muscular weakness, dysphagia, and dry mouth.

In upper- and lower-limb post-stroke spasticity, a small cohort of Japanese patients receiving incobotulinumtoxinA 400 U during the open-label lead-in tolerability periods of two Phase 3 studies (J-PURE and J-PLUS) reported only mild or moderate AEs — 5 of 11 patients (45.5%) in J-PURE and 8 of 11 (72.7%) in J-PLUS. No serious AEs were reported, and no patient discontinued due to an AE. Non-serious, transient AEs of special interest in J-PURE comprised muscular weakness and eyelid ptosis in two patients. In essential tremor, a randomized, double-blind, placebo-controlled exploratory trial of customized incobotulinumtoxinA injections (total dose ≤200 U) demonstrated a favorable tolerability profile; the principal finding was a slight and transient reduction of maximal grip strength versus placebo, with two patients reporting localized finger muscle weakness.

Across indications, the collective evidence from the pooled neurological safety analysis and individual indication studies supports and extends the favorable safety and tolerability profile of incobotulinumtoxinA established by individual clinical studies. The absence of fatal TEAEs, the low rate of discontinuations attributable to adverse events, and the lack of cumulative toxicity with repeated dosing are consistent findings across the studied populations.

Xeomin's Ambitious Bid to Redefine Migraine Prophylaxis

Merz Therapeutics' announcement of completing Phase III enrollment for Xeomin (incobotulinumtoxinA) in chronic and episodic migraine prevention trials marks a significant moment for the company and the broader migraine treatment landscape. This move represents an ambitious effort to expand Xeomin's utility beyond its established neurological indications, such as cervical dystonia and blepharospasm, into a highly competitive and rapidly evolving therapeutic area.

If successful, these trials could position Xeomin as a formidable contender in migraine prophylaxis. A key strategic advantage for incobotulinumtoxinA is its complexing protein-free formulation. Research suggests this characteristic may reduce the risk of neutralizing antibody formation, which can lead to secondary treatment failure over time. For patients requiring long-term, repeated injections for chronic migraine, this potential for sustained efficacy without immunoresistance could be a crucial differentiator. Furthermore, evidence points to incobotulinumtoxinA offering cost savings compared to other botulinum toxin type A products, partly due to reduced wastage, which could appeal to healthcare systems and payers.

However, the path forward is not without its challenges. The migraine prevention market has seen the rise of highly effective CGRP monoclonal antibodies, which some real-world studies indicate may offer superior efficacy and lower adverse event rates compared to onabotulinumtoxinA, particularly in difficult-to-treat chronic migraine patients. Xeomin will need to demonstrate compelling efficacy and a distinct value proposition to compete effectively against these newer agents. Moreover, previous exploratory studies with botulinum toxin type A in episodic migraine have yielded mixed results, suggesting that demonstrating clear superiority over placebo in this population could be challenging. The known 'wear-off' phenomenon of botulinum toxin type A, where efficacy may wane by the third month post-injection, also presents a consideration for long-term patient management and satisfaction. The upcoming trial results will therefore be critical in determining Xeomin's future role and Merz's strategic positioning in this dynamic market.