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FDA Expands Labeling for Imbruvica (Ibrutinib) to Include Treatment of Waldenström’s Macroglobulinemia

Approval is drug’s fourth indication in U.S.

The FDA has approved Imbruvica (ibrutinib, Janssen Biotech/Pharmacyclics, Inc.) capsules as the first therapy indicated specifically for patients with Waldenström’s macroglobulinemia (WM), a rare, indolent type of B-cell lymphoma. This represents the fourth indication for Imbruvica since its initial approval in November 2013.

The update to the Imbruvica label is based on data from a Dana-Farber Cancer Institute phase II study. The data were presented at the 2013 annual meetings of the American Society of Hematology (ASH) and the International Congress of Malignant Lymphoma (ICML).

The phase II multicenter study on which the approval was based evaluated the efficacy and tolerability of ibrutinib 420 mg once daily in 63 patients with previously treated WM (median age, 63 years). The response rate was 62%. Nearly 51% of the patients achieved a partial response (PR), and 11% achieved a very good PR. No complete responses were reported. The median time to response was 1.2 months. The median duration of response has not been reached (range, 2.8+ to 18.8+ months).

The most common adverse events (AEs) included neutropenia, thrombocytopenia, diarrhea, rash, nausea, muscle spasms, and fatigue. Six percent of the patients discontinued treatment because of AEs. AEs leading to dose reduction occurred in 11% of the patients.

Approximately 1,000 to 1,500 new cases of WM occur in the U.S. each year, and the median age at diagnosis is 60 to 70 years.

WM –– a clinically recognized subset of lymphoplasmacytic lymphoma –– begins with a malignant change to the B cell, a type of lymphocyte, during its maturation so that it continues to reproduce more malignant B cells. WM cells make large amounts of the antibody immunoglobulin M (IgM), mostly in the bone marrow. Antibodies such as IgM normally help the body to fight infection. However, the overproduction of IgM, a hallmark of WM, often leads to the bone marrow becoming dysfunctional. Typically, patients with WM are diagnosed after developing symptoms associated with the disease, such as anemia, fatigue, and night sweats.

Ibrutinib works by blocking a specific protein, Bruton’s tyrosine kinase (BTK). The BTK protein transmits important signals that tell B cells to mature and to produce antibodies and is needed by specific cancer cells to multiply and metastasis. Ibrutinib targets and blocks BTK, thereby inhibiting cancer cell survival and metastases.

In addition to WM, Imbruvica is indicated to treat patients with mantle cell lymphoma who have received at least one prior therapy; chronic lymphocytic leukemia (CLL) who have received at least one prior therapy; and CLL with the 17p deletion.

Source: PR Newswire; January 29, 2015.

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