Prophylactic use of subcutaneous CSL830, a C1 inhibitor, twice weekly led to a significant reduction in acute attacks in patients with hereditary angioedema, a disabling and potentially fatal condition caused by a deficiency or dysfunction of the C1 inhibitor protein.

• Randomized, double-blind, placebo-controlled Phase 3 trial
• Safety and efficacy of self-administered SC CSL830 evaluated in patients with type I or type II hereditary angioedema
• Patients had 4 or more attacks in a consecutive 2-month period within 3 months before screening
• Crossover design; patients assigned to 1 of 4 treatment sequences, two 16-week treatment periods
• 40 IU or 60 IU CSL830/kg twice weekly then placebo or vice versa
• Primary endpoint: number of attacks of angioedema
• Secondary endpoint: proportion of patients who had ≥50% reduction in number of attacks with CSL830; number of times rescue meds used

• 90 patients underwent randomization; 79 completed trial
• Both CSL830 doses reduced rate of attacks compared to placebo (mean difference with 40 IU dose: –2.42 attacks/month; 95% CI, –3.38 to –1.46; mean difference with 60 IU dose: –3.51 attacks/month; 95% CI, –4.21 to –2.81; P<0.001 for both)
• Response rates: 40 IU group: 76%; 60 IU group: 90%
• Rescue medication use per month: 40 IU group: 1.13 uses vs 5.55 uses for placebo group, 60 IU group: 0.32 uses vs 3.89 uses for placebo group
• Adverse events: similar proportion between CSL830 and placebo; most common was mild and transient local site reactions