We aimed to conduct a Systematic Review and Single-Arm Meta-Analysis exploring the effectiveness of Galcanezumab in cluster headache, incorporating the majority of available studies.

We conducted a systematic search in PubMed, Scopus, and Cochrane for studies using Galcanezumab (240–300 mg) in patients with chronic or episodic cluster headache. The primary outcome was the weekly reduction in headache attacks. Secondary outcomes included the percentage of patients with more than 50% response and patient global perception of improvement (PGI-I). Statistical analysis was performed using Review Manager Web 8.0.0 (RevMan Web) and Open Meta.

258 patients were included from six studies, three of which were RCTs. The main difference was calculated from baseline attacks versus bouts after receiving treatment. The weekly reduction in headache episodes was significantly lower (MD -6.3; 95% CI -7.35, -5.24). The percentage of patients achieving a >50% response during this timeframe was 66.6% (95% CI 45.8, 87.4), and the proportion of patients reporting a PGI-I score of 'much better' or 'better' was 65.7% (95% CI 42.4, 89.1). In a sub-group analysis of the three randomized controlled trials comparing Galcanezumab to placebo, which included 358 patients, the weekly reduction in headache attacks was not significant (MD -2.45; 95% CI -4.98, 0.08).

The use of Galcanezumab for cluster headache can effectively reduce the frequency of attacks after treatment compared to baseline especially during the first weeks. However, the analysis of placebo-controlled studies showed no significant reduction. Further investigations are needed in subgroups of patients who are refractory to other treatments and with a larger sample size.