Efficacy and safety of galcanezumab as a treatment of refractory episodic and chronic cluster headache: Case series and narrative review

Background Galcanezumab, a monoclonal antibody targeting calcitonin gene-related peptide (CGRP), has demonstrated clinical benefit as a preventive treatment of episodic cluster headache (ECH) but not in chronic cluster headache (CCH) to this date. Our objective was to analyze our clinical experience of the compassionate use of galcanezumab in cluster headache and to conduct a narrative review of the published literature. Methods We present a case series of patients with refractory ECH and CCH treated with 240 mg galcanezumab monthly in an outpatient headache clinic. We recorded epidemiologic and clinical data and analyzed the disease evolution after 3 and 6 months. The review was performed following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results We included three patients with ECH who were treated during a refractory cluster bout (mean duration of 83.7 days since the first attack, range 46.0-105.0 days) and six patients with CCH who had a high frequency of attacks (mean 35.8 attacks/week, range 7-56) and refractory to a mean of 5.2 preventive treatments (range, 3-9). In the CCH group, >50% frequency reduction was seen in 83% (5/6 patients) and the number of attacks per week showed a mean reduction of -24.2 at month 3 (range, -6 to -49) and -27.6 at month 6 (range, -7 to -49). In the ECH group, the bout ended a mean 17.3 days (range, 10-28) after galcanezumab administration. One third of patients reported mild adverse events, none of them leading to discontinuation. Conclusion In conclusion, our clinical experience supports the use of galcanezumab in patients with refractory cluster headache. These results might encourage the possibility of continuing clinical development with randomized controlled trials of anti-CGRP treatments in patients with cluster headache.