FDA Approval of Ibrutinib for Waldenström's Macroglobulinemia a First for These Patients

Carl Harrington

The recent extended approval of ibrutinib for the treatment of Waldenström’s macroglobulinemia (WM), the disease’s first FDA-approved therapy, has provided new hope for patients with the orphan disease.

Carl Harrington, President of the International Waldenström’s Macroglobulinemia Foundation (IWMF), said he and the rest of the WM community are thrilled with the FDA’s decision on the approval.

“It’s the very first time that WM patients have a treatment that’s been specifically studied to treat the disease,” he said in a phone interview with Oncology Nursing News. “It’s also not just for relapsed or refractory patients, it’s for everyone.”

The decision was based on a phase II study of 63 patients with relapsed/refractory WM who received 420 mg ibrutinib once daily for up to 2 years until disease progression or unacceptable toxicity. The overall response rate (ORR) on the trial was 62%, according to an independent review committee. Responses ranged from 2.8 to 18.8 months, though a median has not yet been reached. At baseline, patients’ mean hemoglobin level was 10.5mg/dL, and mean serum IgM level was 3610. Anemia was the most common reason for treatment initiation (87.3% of patients).

In total, 11% of patients had very good partial responses, and 51% had partial responses. According to data presented at the 2013 ASCO Annual Meeting, the best ORR (minor response or better using consensus criteria adapted from the 3rd International Workshop on WM) was 83% following a median of 9 cycles.

Approximately 1000-1500 patients in the United States are diagnosed with WM, a rare form of non-Hodgkin lymphoma, each year, according to the FDA.

Before the approval, physicians relied on borrowed treatments from similar diseases, Harrington said.

“Of course they worked pretty well, but sometimes the reactions of WM patients were different,” he said. “This is the first treatment that’s studied and approved for us, and we’re just thrilled with that.”

Ibrutinib seems to work well against WM patients who have the MYD8 mutation, which 90% of all WM patients have, but not as well in WM patients who have the CXCR4 mutation, which about 28% of patients have, Harrington said.

“Most cancers have many mutations, we seem to have a smaller number, and with 90% of patients having the same mutation, it really helps researchers hone in on potential treatments,” he said.

Harrington said the approval is setting the groundwork for more developments in WM treatment.

“Ibrutinib is being tested right now in combination with other drugs, and there are other drugs in development, including one from Idera, IMO-8400, which recently received orphan drug designation from the FDA.”

Harrington said ibrutinib is well tolerated. Results from the study show the most common adverse events to be neutropenia, thrombocytopenia, diarrhea, rash, nausea, muscle spasms, and fatigue. These events led to dose reduction in 11% of patients and discontinuation in 6% of patients.

While the newly approved agent is welcome in the community, there will be some new challenges for physicians and patients.

“This is the first time a broad spectrum of WM patients will be able to take a daily oral therapy specific to our disease instead of going in for an infusion, which raises compliance issues which have never been an issue for us,” Harrington said.

But Harrington said the IWMF will be working with pharmaceutical companies, other advocacy groups, and the medical community to make sure that patients understand the importance of continuing to take their medication.