Study of Veltuzumab (hA20) at Different Doses in Patients With ITP

The goal of current treatment guidelines for most patients with chronic adult ITP is to
maintain platelet levels above 30 x 109/L. The conventional first-line therapy is
corticosteroids with or without intravenous immunoglobulins, but many patients relapse when
steroids are tapered. Standard therapy then is splenectomy, but patients with refractory ITP
who do not respond require further therapy. Unfortunately, immunosuppressive agents or other
available treatments typically produce only short-term responses. Because of the lack of
medical options after first-line therapy, the target population for this first study of
anti-CD20 immunotherapy with hA20 are adult patients with chronic ITP who failed at least
one standard ITP therapy (i.e., received at least one standard ITP therapy and now present
with platelet levels below 30 x 109/L).

In autoimmune disease, rituximab as well as other anti-CD20 antibodies currently being
considered for commercialization have focused on a different dosing schedule in rheumatoid
arthritis, and use fixed dosages rather than variable doses based on body surface area. In
addition, recent studies of these newer anti-CD20 antibodies in rheumatoid arthritis have
reported that lower doses indeed appear effective when administered twice, 2 weeks apart.
Based upon these considerations, patients in this study will receive hA20 twice, 2 weeks
apart, and administered at one of 3 dose levels.

Inclusion Criteria:

- Male or female, >18 years old, with or without prior splenectomy

- Signed written informed consent obtained prior to study entry

- ITP according to ASH guidelines, with other potential causes of thrombocytopenia
excluded

- Platelet levels < 150 x 109/L for more than 6 months

- Received an adequate course of at least one standard ITP treatment (an inadequate
course of standard ITP therapy does not qualify as meeting this requirement)

- Platelet count < 30 x 109/L at study entry and on at least one other occasion at
least 1 week apart within the past month. (Phase I only: platelet count also > 10 x
109/L at study entry).

- Bleeding assessment score of Grade 0 or 1. See full protocol for all inclusion
criteria

Exclusion Criteria:

See full protocol for exclusion criteria or contact study staff for details