First Drug Approved Specifically for Waldenstrom's Macroglobulinemia

The first drug specifically for Waldenström’s macroglobulinemia (WM) was approved by the Food and Drug Administration today. The FDA has expanded the approval of Imbruvica (ibrutinib) for the treatment of patients with WM. This approval comes more than two months ahead of its expected review deadline of April 17.

WM is a rare form of non-Hodgkin lymphoma, with approximately 1,000 to 1,500 patients in the US diagnosed with WM each year.

The FDA approval was based on a phase 2 study of 63 patients who received 420 mg Imbruvica once daily. The overall response rate on the trial was 62 percent, according to an independent review committee. Responses ranged from 2.8 to 18.8 months, though a median has not yet been reached.

“Today’s approval highlights the importance of development of drugs for supplemental indications,” Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, said in a statement. “Continued research has discovered new uses of Imbruvica.”

Patients on the trial received Imbruvica alone and were treated until disease progression or unacceptable toxicity. In total, 11 percent of patients had very good partial responses and 51 percent had partial responses. According to data presented at the 2013 annual meeting of the American Society of Clinical Oncology, the best overall response rate (minor response or better using consensus criteria adapted from the 3rd International Workshop on WM) was 83 percent following a median of nine cycles.

The most common adverse events observed on the trial were neutropenia, thrombocytopenia, diarrhea, rash, nausea, muscle spasms and fatigue. Adverse events led to dose reduction in 11 percent of patients and discontinuation in 6 percent.

"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," Steven P. Treon, lead investigator of the trial and director of the Bing Center for WM at the Dana-Farber Cancer Institute, said in a statement.

This is the fourth indication for the agent. Ibrutinib is also approved for patients with chronic lymphocytic leukemia (CLL) with a 17p deletion, patients with CLL who had received at least one prior treatment, and patients with mantle cell lymphoma who have received at least one prior treatment. The agent received a breakthrough therapy designation for WM in February 2013.