The primary objective is to determine if BPL's GAMMAPLEX raises the platelet count of subjects with chronic ITP to a threshold of 50 x 109/L, similar to that of a historical control. The secondary objectives are: 1) to determine the safety of GAMMAPLEX at the dosage used in this study. 2) to determine if GAMMAPLEX maintains platelet counts of ³ 50 x 109/L in subjects with chronic ITP for a period of time similar to that of a historical control.

• Biological: Gammaplex, intravenous immunoglobulin
• Biological: Gammaplex

Inclusion Criteria:

1. Males and females aged between 6 and 70 years.
2. Confirmed diagnosis of chronic ITP of at least 6 months duration.
3. Platelet count of less than or equal to 20 x 10 9/L at enrollment.
4. Absence of other conditions that, in the opinion of the investigator, could cause thrombocytopenia.
5. If subjects are currently being treated with corticosteroids the treatment regimen/dose must have been stable (for a minimum of 2 weeks before screening). However, subjects must remain on a stable treatment regimen. If there is any intent to alter the corticosteroid treatment regimen (e.g., tapering of corticosteroids) before Day 10, subjects may not be included in the study.
6. If subjects are currently being treated with cyclophosphamide, azathioprine or attenuated androgens, the treatment regimen and dose must have been stable for a minimum of 2 months before screening. However, if there is any intent to alter the treatment regimen before Day 10, subjects may not be included in the study.
7. Splenectomized subjects and both Rh(D)+ and Rh(D)- subjects may be included.
8. The subject has signed an informed consent form (if at least 18 years old) or the subject's parent or legal guardian has signed the informed consent form. If appropriate, the subject has signed a child assent form.
9. If a subject is a female of child-bearing potential, she must have a negative result on a urine-based HCG pregnancy test.
10. If a subject is a female who is or becomes sexually active, she must practice contraception by using a method of proven reliability for the duration of the study.

Exclusion Criteria:

1. The subject has a history of any severe or anaphylactic reaction to blood or any blood-derived product, or any severe reaction to IGIV or any other IgG preparation.
2. The subject is known to be intolerant to any component of the investigational product.
3. The subject has received any live virus vaccine within the last 3 months.
4. The subject has received an IGIV preparation within 1 month prior to screening.
5. The subject is currently receiving, or has received, any investigational agent within the 1 month prior to screening.
6. The subject has received any blood, blood product, or blood derivative within the 1 month prior to screening.
7. The subject has received Rituximab within the 3 months before screening
8. The subject is pregnant or is nursing.
9. The subject is positive for any of the following at screening: HBsAg, NAT for HCV, NAT for HIV, Antibodies to HCV or HIV 1 or 2.
10. The subject, at screening, has levels greater than 2.5 times the upper limit of normal, as defined by the central laboratory, of alanine aminotransferase or aspartate aminotransferase.
11. The subject has a severe renal impairment (defined as serum creatinine greater than 2 times the upper limit of normal or BUN greater than 2.5 times the upper limit of normal for the range of the laboratory doing the analysis); the subject is on dialysis; the subject has a history of acute renal failure.
12. The subject is known to have abused alcohol, opiates, psychotropic agents, or other chemicals or drugs within the past 12 months.
13. The subject has a history of deep vein thrombosis (DVT) or thrombotic complications of IGIV therapy.
14. The subject has any history or sign of hyperviscosity, transient ischemic attack (TIA), stroke, other thromboembolic event, or unstable angina.
15. The subject suffers from any acute or chronic medical conditions (e.g., renal disease or predisposing conditions for renal disease, coronary artery disease, or protein losing enteropathy) that, in the opinion of the investigator, may interfere with the conduct of the study.
16. The subject has an acquired medical condition, such as chronic lymphocytic leukemia, lymphoma, multiple myeloma, chronic or recurrent neutropenia (defined as an absolute neutrophil count (ANC) < 1 x 109/L).
17. The subject has non-controlled arterial hypertension (systolic blood pressure >160 mmHg and/or diastolic blood pressure >90 mmHg).
18. The subject is anemic (hemoglobin <10 g/dL) at screening.
19. The subject is unlikely to adhere to the protocol requirements of the study or is likely to be uncooperative..