Assessment of Safety and Efficacy of a New Intravenous Immunoglobulin (IGIV3I 10% Grifols) In Subjects with Chronic Immune Thrombocytopenia

Abstract 4669

Two similarly designed prospective, uncontrolled, open-label clinical trials were planned to assess the safety and efficacy of a new intravenous immunoglobulin (IVIG), IGIV3I 10% Grifols, in subjects with chronic immune thrombocytopenia (ITP) in the USA, Canada and Europe (Spain, Russia and the United Kingdom). Subjects were candidates to be enrolled if they had a diagnosis of chronic ITP and a baseline platelet count ≤ 20 × 10⁹/l. Eligible subjects received treatment with IGIV3I 10% Grifols 1g/kg for 2 consecutive days or 0.4 g/kg for 5 consecutive days. The primary efficacy endpoint was the response rate, defined as the proportion of subjects reaching or exceeding the threshold value of 50 × 10⁹/l on or before day 8 (American study) or on day 30 (European study) where day 1 is the day of the first infusion. Secondary efficacy endpoints were the time to response, defined as the number of days elapsed from day 1 to achievement of the threshold value; duration of response, defined as the number of consecutive days with a platelet count known to be ≥50 × 10⁹/l; the maximum (peak) platelet count and regression of haemorrhagic diathesis for those subjects presenting with bleeding signs at baseline. Safety endpoints included adverse events (AEs), physical examinations, vital signs and clinical laboratory parameters monitoring. A total of 27 subjects (18 adults and 9 pediatrics) have been enrolled, i.e. administered with at least one infusion of the product at any dose, in the study. Twenty-four (24) subjects (89%) were considered responders. This proportion was higher in pediatric subjects (9/9, 100%) than in adult subjects (15/18, 83%). The mean time to response was 1.6 days (Standard Deviation (SD) 0.9); the mean duration of response was 14.0 days (SD 12.1) and the mean maximum platelet count was 263 × 10⁹/l (SD 195.6). Twenty-three (23) subjects (all the pediatric subjects 9/9 and 14/18 adults) presented with some sign of bleeding at baseline. All subjects (23/23, 100%) experienced an improvement in the haemorrhagic diathesis, regardless of some of them being considered non-responders according to the platelet count criterion. A total of 92 AEs potentially related to study drug were reported. The most common of these were headache (25 events), nausea (8 events), pyrexia (7 events) and chills (6 events). Only 1 AE was reported as definitely related to study drug, an event of palmar erythema. Two serious AEs (SAE) potentially related to the study drug were reported in 2 subjects. One of them was an unexpected laboratory alteration which consisted in leukopenia and decreased hemoglobin and advised to maintain the subject hospitalized for further observation during the weekend. The reaction was transient, without complications or other clinical symptoms and total recovery of the normal laboratory values. The second SAE was an event of thrombosis in the right humeral vein, in a patient with a number of predisposing medical conditions. At the time of discharge the patient's overall condition was satisfactory. Analysis of AEs, clinical laboratory values, physical assessments and vital signs did not indicate any safety concerns for subjects receiving the study drug and are in line with those expected for the ITP population treated with IVIG. Both primary and secondary efficacy endpoints show a good response to the product in terms of rapid elevation of platelet counts to an hemostatic level in line with what is expected for an IVIG product. Moreover, the improvement of the baseline bleeding diathesis even in patients considered as non-responders according to the platelet count criterion is highly suggestive of the clinical efficacy of the product. Overall, these results indicate that treatment with the new IGIV3I 10% Grifols is safe and efficacious for rapidly increasing platelet counts in chronic ITP subjects and improving their bleeding diathesis.