Side Effects of Galcanezumab in Order of Occurrence
Injection-site pain is the most common side effect of galcanezumab, occurring in approximately 11-14% of patients, followed by nasopharyngitis (7%), upper respiratory tract infection (10%), and injection-site reactions (13.9%). 1, 2, 3
Most Common Side Effects (≥5% of Patients)
Based on the FDA label and clinical trial data, the side effects in descending order of frequency are:
Primary Injection-Related Effects
- Injection-site pain: 11.4% of patients (compared to 2.9% with placebo) 2
- Injection-site reactions (general): 13.9% of patients (compared to 5.8% with placebo) 2
- Injection-site pruritus: Significantly more common than placebo 4
- Injection-site erythema: Significantly more common with 240 mg dose 4
Respiratory Infections
- Upper respiratory tract infection: 10.0% of patients (compared to 8.8% with placebo) 2, 3
- Nasopharyngitis: 7.0% of patients (compared to 2.2% with placebo) 2, 3
- Sinusitis: ≥10% of patients in long-term studies 3
Musculoskeletal Effects
- Back pain: ≥10% of patients in long-term studies 3
Less Common but Clinically Important Side Effects
Hypersensitivity Reactions
- Potential hypersensitivity events: 3.3% with galcanezumab (compared to 5.1% with placebo) 2
- Anaphylaxis and angioedema: Reported in post-marketing surveillance 1
- Rash: Reported in post-marketing experience 1
Immunogenicity
- Anti-drug antibody development: 4.6% of patients during treatment, with 5% (16/128) developing anti-galcanezumab antibodies in some studies 1, 2
- Most patients who developed antibodies tested positive for neutralizing antibodies, though this did not appear to affect pharmacokinetics, safety, or efficacy 1
Serious Adverse Events (Rare, <1%)
The following serious adverse events were each reported by single patients in clinical trials 2:
- Appendicitis
- Crohn's disease
- Suicidal ideation
- Congenital ankyloglossia (in infant of paternal pregnancy)
Adverse Events Leading to Discontinuation
Overall discontinuation rate due to adverse events was low at 4.8% in long-term studies, with the following specific events leading to discontinuation 2, 3:
- Abdominal pain (one patient)
- Visual impairment (one patient)
- Upper limb fracture (one patient)
Important Clinical Context
The majority of treatment-emergent adverse events were rated as mild to moderate in severity, and the completion rate during treatment was high at 81.9% 2, 5. The 120 mg and 240 mg doses showed comparable safety profiles, with no clinically meaningful differences in adverse event rates between the two doses 3, 4.
Laboratory values, vital signs, and electrocardiograms did not show any clinically meaningful changes with galcanezumab treatment 3. The incidence of serious adverse events was only 3.7% across all dose groups in long-term studies 3.