The US Food and Drug Administration (FDA) today expanded the approved use of Imbruvica® (ibrutinib) for patients with Waldenström’s macroglobulinemia, a rare type of B-cell lymphoma. Imbruvica® is the first therapy indicated specifically for Waldenström’s macroglobulinemia and previously received Breakthrough Therapy designation for this use.
A type of non-Hodgkin lymphoma, Waldenström’s macroglobulinemia usually gets worse slowly over time and causes B lymphocytes to grow within the bone marrow, lymph nodes, liver, and spleen. The abnormal B cells also overproduce a protein known as immunoglobulin M or IgM (macroglobulin) that may lead to excess bleeding and problems with vision and the nervous system.
According to the National Cancer Institute, approximately 70,800 Americans were diagnosed and 18,990 died from non-Hodgkin lymphomas in 2014. Imbruvica® is a selective inhibitor of Bruton’s tyrosine kinase, a component of the B-cell receptor signaling pathway that plays a key role in the development and progression of Waldenström’s macroglobulinemia. In other words, the targeted therapy attacks the pathway that mediates disease progression.
The new approval was based on data from a phase II multicenter study of 63 previously treated patients with Waldenström’s macroglobulinemia. All study participants received a daily 420-mg dose of Imbruvica® until disease progression or side effects became intolerable. Results showed 62% of participants had their cancer shrink after treatment (overall response rate). Nearly 51% of patients achieved a partial response, and 11% achieved a very good partial response. No complete responses were reported. At the time of the study, the duration of response ranged from 2.8 months to approximately 18.8 months.
Reference: Treon SP, Tripsas CK, Yang G, et al: A prospective multicenter study of the Bruton’s tyrosine kinase inhibitor ibrutinib in patients with relapsed or refractory Waldenstrom’s macroglobulinemia. 2013 ASH Annual Meeting. Abstract 251. Presented December 9, 2013.
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