Population pharmacokinetic simulation of varied Immune Globulin Subcutaneous (Human), 20% solution (Ig20Gly) loading and maintenance dosing regimens in immunoglobulin-naïve patients with primary immunodeficiency diseases

•A PK model simulated Ig20Gly dose regimen scenarios in IG-naïve patients with PID.•Steady-state IgG achieved by around Week 12 for all baseline endogenous IgG levels.•Time to target trough IgG level depended on baseline IgG and Ig20Gly loading scheme.•Simulations indicated that protective IgG levels may be attained within 1–3 weeks.•A 400- or 800-mg/kg/mo maintenance regimen appeared adequate for stable IgG levels. The pharmacokinetics of Ig20Gly, a 20% subcutaneous immunoglobulin (IG) therapy, is well characterized in IG-experienced patients with primary immunodeficiency diseases (PID). Data from IG-naïve patients are limited. Simulate serum total immunoglobulin G (IgG) pharmacokinetic profiles in IG-naïve patients with PID for different Ig20Gly initiation and maintenance dosing regimens. A population pharmacokinetic model developed with data from pivotal phase 2/3 trials of weekly Ig20Gly in PID (NCT01412385, NCT01218438) was used to simulate pharmacokinetic profiles of IgG in various scenarios with 400- or 800-mg/kg total loading doses (administered as split doses over 1–2 weeks) and corresponding 100- or 200-mg/kg weekly maintenance doses, respectively. Endogenous baseline IgG levels (1.5, 2.0, 4.0, 6.0 g/L) were evaluated for each scenario; time to putative therapeutic target IgG trough level (7 g/L) was determined. Serum IgG levels reached steady-state by approximately Week 12 for all scenarios and baseline endogenous IgG levels. Time to target trough level generally occurred sooner with 1-week versus 2-week loading schemes. Endogenous baseline IgG levels