This is a prospective, multi-center, randomized, open-label, 2-period cross-over study (16 weeks per treatment period) to evaluate flexible dosing and daily push dosing of IGSC 20% in treatment-experienced subjects with PI. There is an additional, separate cohort of treatment-naïve, non-randomized subjects with PI who will not be part of the crossover.~Treatment-experienced subjects entering the study will maintain the same IgG dose (mg/kg) received prestudy that will be normalized to the study-assigned dose-time interval (ie, there will be 1:1 correspondence regardless of prestudy route of administration [intravenous [IV] or SC]). Treatment-experienced subjects will be randomized in a 1:1:1 ratio into 1 of 3 parallel cohorts consisting of 18 subjects each as follows:~Cohort 1 (daily push compared with every 2 weeks [biweekly] pump) will evaluate syringe daily push dosing versus every 2 weeks [biweekly] ambulatory pump administration. Subjects will be randomized in a 1:1 ratio to 1 of 2 sequences, either beginning with syringe daily push dosing for 16 weeks and then crossing over to ambulatory pump administration every 2 weeks for 16 weeks or the reverse sequence.~Cohort 2 (daily push compared with once weekly pump) will evaluate syringe daily push dosing versus once weekly ambulatory pump administration. Subjects will be randomized in a 1:1 ratio to 1 of 2 sequences, either beginning with syringe daily push dosing for 16 weeks and then crossing over to ambulatory pump administration once every week for 16 weeks or the reverse sequence.~Cohort 3 (daily push compared with 2 times/week pump) will evaluate syringe daily push dosing versus 2 times/week ambulatory pump administration. Ambulatory pump dosing will take place on preselected days (eg, Monday and Thursday) not less than 3 days apart. The dosing days should remain constant for the duration of the study. Subjects will be randomized in a 1:1 ratio to 1 of 2 sequences, either beginning with syringe daily push dosing for 16 weeks and then crossing over to ambulatory pump administration 2 times/week for 16 weeks or the reverse sequence.~The treatment-naïve cohort will receive a loading dose of 5 consecutive daily doses of IGSC 20% 150 mg/kg/day (Week 0, Days 1-5) followed by weekly infusions of 150 mg/kg starting Week 1 (Day 8) through Week 32 (end of Treatment Phase).
This is a prospective, multi-center, randomized, open-label, 2-period cross-over study (16 weeks per treatment period) to evaluate flexible dosing and daily push dosing of IGSC 20% in treatment-experienced subjects with PI. An additional, separate cohort of treatment-naïve, non-randomized subjects who will not be part of the crossover are included and will receive a loading dose of 5 consecutive daily doses of IGSC 20% followed by weekly infusions of IGSC 20% starting Week 1 (Day 8) through Week 32 (end of Treatment Phase).~For treatment-experienced subjects, the study consists of a Screening Visit, Baseline Visit, 16-week Treatment Period 1, 16-week Treatment Period 2, and Final Visit/Early Termination Visit. For treatment-naïve subjects, the study consists of a Screening Visit, a Baseline Visit, a 32-week Treatment Phase, and Final Visit/Early Termination Visit.~Approximately 54 treatment-experienced subjects and approximately 6 treatment-naïve subjects will be enrolled at study centers in the United States (US) and European Union (EU).