In 2021, the Italian Medicines Agency approved reimbursement of monoclonal antibodies targeting the CGRP pathway (CGRP-mAbs) as preventive therapies for patients with high frequency and chronic migraine (CM). A moderate to severe disability, quantified as a MIgraine Disability ASsessment (MIDAS) score > or equal to 11, is required for prescription. Score reduction of at least 50% after the first three months (T3) is mandatory to continue treatment.

This is a prospective real-life, open-label study. CM patients will be treated with erenumab 70-140 mg subcutaneous injections every 28 days for one year (T13). We will record the following parameters: demographic and headache features, monthly migraine and headache days (MMDs and MHDs respectively), days and doses of symptomatic intake. Patients also completed questionnaires evaluating migraine related disability (MIDAS and HIT-6), psychological comorbidities (HADS-A and HADS-D), quality of life (MSQ and 0 to 100 visual analogue scale) and allodynia (ASC-12).

At least a 50% reduction in MIDAS score or MMDs after 3 months of treatment will be testedas predictors of long-term clinical outcome.

Monoclonal antibodies directed against the Calcitonin Gene Related Peptide (CGRP-mAbs) pathway are a silver lining in the setting of migraine therapies, partly overcoming the issues related to poor effectiveness and tolerability of previous preventive treatments.

These drugs act on the CGRP pathway, a key vasoactive neuropeptide in migraine pathophysiology involved in activation and sensitization of afferent trigeminal nociceptors of the trigeminovascular system. Galcanezumab, fremanezumab and eptinezumab target the CGRP ligand, while erenumab, a fully human IgG2, targets its receptor. mAbs efficacy and safety have been largely documented in multiple randomized clinical trials, open-label studies as well as in the real-world setting.

The Italian Medicines Agency (AIFA) approved a 12-month period of mAbs treatment reimbursement through the National Health Service for migraine patients with the following features: i) at least 8 migraine days per month in the last three months, ii) a MIgraine Disability ASsessment (MIDAS) score ≥ 11, and iii) previous failure for inefficacy or no tolerability of at least three preventive drugs, among β-blockers, tricyclic antidepressants, antiepileptics, and onabotulinumtoxin-A for chronic migraine (CM).

In addition, a reduction of at least 50% of MIDAS score after 3 and 6 months of treatment is the only mandatory step to continue beyond these check-points. Thus, MIDAS score is pivotal for mAbs treatment initiation and continuation. MIDAS is a self-administered five-item questionnaire focusing on reduction in home and workplace productivity, and a score > 11 identify a set of patients with a moderate to severe disability. A MIDAS score reduction during mAbs treatment was demonstrated in the short and long term period, but its role as predictor of mAbs clinical outcome has never been consistently studied. A major concern for using a single parameter as a mandatory criterion for prescription and continuation of a preventive treatment is the limited ability to capture the multifaced disability that characterize the migraine spectrum. On the other side, reduction in monthly migraine days (MMDs) represents a pivotal outcome for clinical trials and physicians, but this may not completely highlight the patients' perspective.

The investigators consecutively screened migraine patients attending the outpatient clinic of the Headache Science & Neurorehabilitation Center of the IRCCS Mondino Foundation (Pavia, Italy).

The patients underwent a 1-year treatment with erenumab subcutaneous administration every 28 days (13 administrations) outside of the AIFA reimbursement program within a compassionate program.

During a baseline visit (T0), a neurologist with expertise in the headache field provided clinical indication to erenumab. At T0, the investigators checked the inclusion/exclusion criteria and the headache diaries of the three preceding months, and performed a full neurologic and general examination and a thorough anamnestic evaluation.

Patients who agreed to participate in the study signed a written informed consent and completed the baseline procedures, including clinical and demographic data recording and completion of a set of questionnaires to assess migraine related disability (MIDAS and HIT-6), psychological comorbidities (HADS-A and HADS-D), quality of life (MSQ), a self-perception of general health (0 to 100 visual analogue scale), and allodynia (ASC-12).

The first erenumab administration (70 mg) was delivered in the hospital setting at T0. After the first administration the patients were observed for 2 hours to monitor possible acute adverse events. The patients were then instructed to perform the following self-administrations of erenumab at home every 28 days (T1 to T12).

The patients returned to the Center every 12 weeks for the follow-up visits (T3 - T6 - T9 - T12), and at T13 for the last visit of the protocol. Monthly headache days (MHDs), monthly migraine days (MMDs), and days of acute drug intake were prospectively recorded in a paper headache diary. At each follow-up visit, the patients completed the same study procedures and clinical scales previously defined. At T3, erenumab dosage was increased in 72 patients up to 140 mg, according to the physician's judgment. All patients were allowed to keep their oral preventive medication with a stable dose across all study period.

The primary outcome was to evaluate the role of MIDAS reduction of at least 50% at T3 (MIDASRes) as a predictor of the long-term clinical outcome. As co-primary outcome, the investigators explored the role of early (T3) 50% MMDs reduction (MMDRes) as predictor of long-term efficacy.

In addition, the investigators evaluated the association between MIDASRes as well as MMDRes and the percentage of patients with a reduction in MMDs of at least 50% in the last 4 weeks of observation period (T13) when compared to baseline (RespondersT13). ResponderT13 were defined according to the IHS Guidelines for clinical trials involving CM patients.

As secondary outcomes, the investigators searched for possible associations between baseline clinical/demographic features and long-term efficacy of erenumab treatment, while, as exploratory outcomes, we described 1-year change in migraine-related disability, anxiety and depression severity, allodynia, and quality of life. The study was approved by the local Ethics Committee (P-20190105434).

Inclusion Criteria:

• diagnosis of CM according to ICHD-3 criteria for at least 12 months prior to enrollment;
• completion of a full headache diary in the 3 months preceding the enrollment; compliance to complete a daily headache diary for 1 year;
• previous failure of at least 3 classes of preventive treatments among beta-blockers, antiepileptic drugs, antidepressants, or onabotulinumtoxin-A;
• MIDAS score > 11.

Exclusion Criteria:

• severe cardiologic comorbidities;
• pregnancy and breastfeeding;
• previous adverse reaction to latex

Patients with chronic migraine with clinical features in agreement with AIFA regulations for CGRP-mAbs prescription.