Study Evaluating IGSC 20% Flexible Dosing in Treatment-Experienced and Treatment-Naive Subjects With Primary Immunodeficiency

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).