A phase 3b study reported that Galcanezumab was well-tolerated and improved the condition of people with cluster headaches. Robert Riesenberg et al. aimed to assess long-term safety of Galcanezumab in cluster headache people who had finished one out of two Phase III double-blind studies in cluster headache. In this open-label study, 164 subjects with a mean age of 48.3 years were administered 300 mg Galcanezumab subcutaneously up to once per month.

Safety was the major outcome ascertained, as evaluated by suicidality, serious side effects, and treatment-emergent side effects. Other outcomes incorporated health values, effectiveness as evaluated by the Patient Global Impression of Improvement, immunogenicity, and discontinuation rates. The majority of treatment-related adverse events (n = 119; 72.6%) were mild to moderate, with nasopharyngitis being the most usually reported  adverse effect (22.0% ). Out of 18 serious side effects, constipation was found to be associated with the therapy.

Suicidal thoughts were observed in 2 subjects (1.2%). Because of an adverse event, 5 subjects (3.1%) discontinued. Among the 8 subjects who were therapy-emergent anti-drug antibody positive, 2 subjects were not therapy-associated anti-drug antibody-positive in parent trials. At months one, six, and twelve, 81% of subjects assessed their status of cluster headache as little, much, or very much better on Patient Global Impression of Improvement.

From baseline, improvement in health value scores was witnessed. Hence, Galcanezumab use was associated with improved patient-reported cluster headache status.