This study aims to assess the safety, tolerability and pharmacokinetics of Ig NextGen 10% in patients with primary immune deficiency currently being treated with Intragam P. Eligible patients will switch from 3 to 4 weekly intravenous Intragam P therapy to receive seven cycles of Ig NextGen 10% treatment administered intravenously at three- to four-weekly intervals. Patients will be monitored on the study for up to 36 weeks.

Inclusion Criteria:

• Clinical diagnosis of PID
• = or >6 month use of Intragam P at three- or four-weekly intervals
• = or >6 month history of IgG trough levels of ≥ 5 g/L

Exclusion Criteria:

• Newly diagnosed PID within six months prior to Screening
• Known selective IgA deficiency or antibodies to IgA
• Immunosuppressive treatment other than topical and/ or inhaled steroids and/ or low dose oral steroids
• Protein-losing enteropathies, or kidney diseases
• History of malignancies of lymphoid cells
• Any of the following laboratory results at Screening:
• Serum Creatinine > 1.5 times the upper normal limit (UNL)
• AST or ALT concentration > 2.5 times the UNL
• Albumin < 25 g/L