Ibrutinib in previously treated Waldenström's macroglobulinemia

Area of Science:

• Hematology
• Oncology
• Pharmacology

Background:

• Waldenström's macroglobulinemia (WM) is characterized by prevalent MYD88(L265P) and CXCR4(WHIM) mutations.
• MYD88(L265P) drives tumor growth via Bruton's tyrosine kinase, a target of ibrutinib.
• CXCR4(WHIM) mutations are associated with in vitro resistance to ibrutinib.

Purpose of the Study:

• To evaluate the efficacy and safety of ibrutinib in pretreated symptomatic patients with Waldenström's macroglobulinemia.
• To investigate the influence of MYD88 and CXCR4 mutation status on patient outcomes with ibrutinib treatment.

Main Methods:

• A prospective study involving 63 patients with WM who had received prior treatment.
• Oral administration of ibrutinib at 420 mg daily until disease progression or unacceptable toxicity.
• Analysis of MYD88 and CXCR4 mutation status to correlate with treatment response and survival.

Main Results:

• Ibrutinib treatment led to significant reductions in serum IgM and bone marrow involvement, and increased hemoglobin levels (P<0.01).
• The overall response rate was 90.5%, with a major response rate of 73.0%.
• Patients with MYD88(L265P)CXCR4(WT) exhibited the highest response rates (100% overall, 91.2% major).
• Estimated 2-year progression-free survival was 69.1% and overall survival was 95.2%.
• Common grade 2+ toxicities included neutropenia (22%) and thrombocytopenia (14%), more frequent in heavily pretreated patients.

Conclusions:

• Ibrutinib is an effective and safe treatment for pretreated Waldenström's macroglobulinemia patients, yielding durable responses.
• MYD88 and CXCR4 mutation status significantly influence patient response to ibrutinib.
• The findings support ibrutinib as a valuable therapeutic option in WM, with mutation status guiding treatment considerations.