Protective antibody concentrations in primary immunodeficiency following infusion with 5% or 10% intravenous immunoglobulin

<b>Background:</b> Inadequate production of immunoglobulin G (IgG) antibodies renders patients with primary immunodeficiency susceptible to infection by numerous pathogens, some of which can lead to severe asthma exacerbation and possible death. These patients who are immunocompromised are often reliant on intravenous immunoglobulin (IVIG) therapies, which provide passive antibodies against various respiratory pathogens, including measles virus and encapsulated bacteria. <b>Objective:</b> We conducted a subanalysis of data from a multicenter, multinational, phase III, open-label bioequivalence study to compare protective concentrations of IgG antibodies provided by a 5% and a 10% IVIG product in patients with primary immunodeficiency. <b>Methods:</b> Patients on stable 21- or 28-day regimens of previous IVIG products were assigned to receive study treatment (adults: 5% IVIG and 10% IVIG; children: 10% IVIG) at doses of 300-800 mg/kg per infusion. Trough concentrations of total IgG, IgG subclasses, measles-neutralizing antibodies, and IgG against Haemophilus influenzae type b and Streptococcus pneumoniae serotypes were evaluated. <b>Results:</b> A total of 48 patients (33 adults ages 16-55 years; 15 children ages 2-15 years) were enrolled and received treatment. No statistically significant differences in trough concentrations of total IgG, IgG subclasses, measles-neutralizing antibodies, or IgG directed at encapsulated bacteria were observed between the 5% and 10% formulations in analyses by age (adult or pediatric) or infusion schedule (every 21 or 28 days). All evaluated patients had trough IgG concentrations above accepted thresholds for protection against disease. <b>Conclusion:</b> These findings support the conclusion that, at dose levels and infusion schedules prescribed in clinical practice, this 5% and 10% IVIG product provided consistent, predictable, and bioequivalent IgG concentrations for adult and pediatric patients with primary immunodeficiency disease. Both formulations delivered trough antibody concentrations of total IgG, measles-neutralizing antibodies, and antibodies against encapsulated bacteria that are above thresholds accepted as protective.Clinical trial NCT01963143, <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.clinicaltrials.gov">www.clinicaltrials.gov</ext-link>.