The purpose of the study is to assess the impact of immunoglobulin treatment by subcutaneous injections every 2 weeks (biweekly) on a cohort of patients with primary and secondary immune deficiencies. The full study will consist of safety, efficacy and Quality of Life (QoL) evaluations and a pharmacokinetic (PK) sub-study. The primary objectives of the study are to determine tolerability and safety of biweekly IgPro20 injection regimen and to compare PK outcomes on weekly and biweekly IgPro20 therapy.

Patients who have received and/or are currently receiving immunoglobulin G (IgG) in intravenous (IVIg), or subcutaneous (SCIg) infusions are eligible for inclusion if they meet inclusion/exclusion criteria.

The study consists of two parts. In Part 1 of the study enrolled subjects will receive IgPro20 weekly for either 12 weeks (for patients on SCIg infusion prior to the study) or 24 weeks (for patients on IVIg infusion prior to the study). Part 2 will consist of a biweekly treatment with IgPro20 for 52 weeks, for both groups.

Additionally, study subjects meeting inclusion criteria for the PK sub-study will undergo a PK sample collection for 1 week and 2 weeks in study Parts 1 and 2, respectively.

Inclusion Criteria:

Full study:

• Female or male patients with primary or secondary immunodeficiency, aged from 5 to 64 years, receiving steady state immunoglobulin G replacement therapy.

Pharmacokinetic sub-study:

• Female or male patients with primary immunodeficiency, aged between 12 and 64 years of age, on steady-state IgPro20 replacement therapy and willing to undergo pharmacokinetic sample collection on weekly and biweekly IgPro20 dosing regimens.

Exclusion Criteria:

• Patients with protein losing conditions such as: lymphangiectasis, nephrosis, status post cardio-thoracic surgery requiring drainage tubes for more than 48 hours, protein-losing enteropathy.
• Concomitant treatment with plasma or other blood products (including any IgGs other than IgPro20 [Hizentra]) within 21 days before study entry and/or during the study.
• Any other condition or treatment that, in the opinion of the investigator, would interfere with obtaining valid results for that subject.
• Women of childbearing potential with a positive pregnancy test.
• Active infection at the time of screening.