The Food and Drug Administration has approved ibrutinib for the treatment of Waldenstrom’s macroglobulinemia, the first treatment approved for this rare cancer, and the fourth indication approved for this targeted therapy.

Ibrutinib, marketed as Imbruvica by Pharmacyclics and Janssen Biotech, is an oral kinase inhibitor and was approved in 2013 for treating patients with mantle cell lymphoma who have received one previous therapy.

In 2014, the drug was approved for patients with previously treated chronic lymphocytic leukemia (CLL) who have received at least one previous therapy, followed by approval for patients with CLL who carry a deletion in chromosome 17.

The latest approval “highlights the importance of development of drugs for supplemental indications,” Dr. Richard Pazdur, director of the office of hematology and oncology products in the FDA’s Center for Drug Evaluation and Research, said in the FDA statement announcing the approval.

This is the first approved treatment for Waldenstrom’s macroglobulinemia (WM), a rare, indolent type of non-Hodgkin’s lymphoma, according to the statement issued by Pharmacyclics. “Because there has never been an FDA-approved treatment for Waldenstrom’s macroglobulinemia since it was first identified over 70 years ago, doctors had to rely on therapies borrowed from similar cancers to treat these patients,” Dr. Steven Treon, director of the Bing Center for Waldenstrom’s Macroglobulinemia at the Dana-Farber Cancer Institute, Boston, said in the statement.

Dr. Treon was the lead investigator of the phase II study that was the basis of the approval. In the study of 63 previously treated patients with WM, patients received 420 mg of ibrutinib per day, until disease progressed or they could no longer tolerate adverse effects of the drug. The overall response rate was 62%, and the duration of response ranged from 2.8 months to almost 19 months, according to the FDA. Thrombocytopenia, neutropenia, diarrhea, anemia, fatigue, musculoskeletal pain, bruising, nausea, upper respiratory tract infection, and rash were among the most common adverse events associated with treatment. The warnings and precautions section of the prescribing information includes recommendations to monitor patients for hemorrhage, infections, and atrial fibrillation, and states that other malignancies have occurred in patients during treatment and that it can cause fetal harm.

Ibrutinib inhibits Bruton’s tyrosine kinase, “a signaling molecule of the B-cell antigen receptor (BCR) and cytokine receptor pathways,” according to the most recent version of the prescribing information. “BTK’s role in signaling through the B-cell surface receptors results in activation of pathways necessary for B-cell trafficking, chemotaxis, and adhesion. Nonclinical studies show that ibrutinib inhibits malignant B-cell proliferation.”

About 1,000 to 1,500 people are diagnosed every year with WM in the United States, at a median age of 60-70 years, according to Pharmacyclics.


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