Background: Calcitonin gene-related peptide has shown to play a central role in cluster headache (CH) pathophysiology. A clinical trial with galcanezumab was carried out in chronic cluster headache (CCH) but did not meet its primay endpoint. However, its off-label use in patients with CCH refractory to other therapies could be considered. We aimed to asses the efficacy and safety of galcanezumab as CCH preventive treatment in a real-life setting.

Methods: An observational study was conducted. Patients with CCH who received at least one dose of 240 mg of galcanezumab.

Results: Twenty-one patients who tried a mean of 6.3 ± 1.9 preventive therapies, including onabotulinumtoxinA in 90.5%. At baseline, the median of frequency was 60 (37.5-105) monthly attacks with 10 (8.3-10) points in pain intensity (Numerical Rating Scale). After one month, the frequency decreased to 31 (10.5-45) (p = 0.003) with 8.5 (8-9.5) intensity (p = 0.007); 10 (47.6%) patients were 50% responders of whom four (19%) were 75% responders. Of the 15 patients with 3 months of follow-up, seven (46.6%) reduced their frequency by 50% and four (26.6%) by 75%, with 40 (10-60) monthly attacks (p = 0.07) and pain intensity of 8 (5-10) (p = 0.026). Some 52% patients experienced adverse events, mostly mild.

Conclusions: In our cohort of refractory CCH, galcanezumab was effective in almost 50% of patients. This finding supports individual off-label treatment attempts.

Keywords: CGRP; chronic cluster headache; galcanezumab; monoclonal antibodies; preventive treatment.