Single-Agent Ibrutinib for Rituximab-Refractory Waldenström Macroglobulinemia: Final Analysis of the Substudy of the Phase III Innovate TM Trial

Clin Cancer Res. 2021 Nov 1;27(21):5793-5800. doi: 10.1158/1078-0432.CCR-21-1497. Epub 2021 Aug 11.

Abstract

Purpose: The first report from the open-label substudy of the phase III iNNOVATE study (PCYC-1127; NCT02165397) demonstrated that single-agent ibrutinib was efficacious and well tolerated in patients with heavily pretreated, rituximab-refractory Waldenström macroglobulinemia. Results from the final analysis are now reported.

Patients and methods: Ibrutinib 420 mg was administered once daily to patients (N = 31) who failed to achieve at least a minor response (MR) or who relapsed <12 months after their last rituximab-containing therapy. Endpoints included progression-free survival (PFS) and overall response rate (ORR; MR or better) per independent review committee, hemoglobin improvement, overall survival (OS), and safety; serum IgM was also assessed.

Results: After a median follow-up of 58 months (range: 9-61), median PFS was 39 months [95% confidence interval (CI): 25-not evaluable]; 60-month PFS rate was 40%. In MYD88L265P/CXCR4WHIM and MYD88L265P/CXCR4WT subtypes, median PFS was 18 months and not reached, respectively. In all patients, ORR was 87%; responses deepened over time with major response (≥ partial response) rates increasing from 61% at 6 months to 77% at 60 months. Median OS was not reached. Seventeen of 21 patients (81%) with baseline hemoglobin ≤11.0 g/dL had sustained hemoglobin improvement. Improvements in serum IgM levels were sustained, reaching a maximum median change of -37 g/L at 54 months. Ibrutinib maintained a manageable safety profile, with no new safety signals identified. There were no events of major hemorrhage or atrial fibrillation.

Conclusions: In the final analysis from iNNOVATE, single-agent ibrutinib continued to show sustained efficacy in patients with heavily pretreated, rituximab-refractory Waldenström macroglobulinemia.

Publication types

  • Clinical Trial, Phase III
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives*
  • Adenine / therapeutic use
  • Aged
  • Aged, 80 and over
  • Antineoplastic Agents, Immunological / therapeutic use*
  • Humans
  • Middle Aged
  • Piperidines / therapeutic use*
  • Rituximab / therapeutic use
  • Treatment Failure
  • Waldenstrom Macroglobulinemia / drug therapy*

Substances

  • Antineoplastic Agents, Immunological
  • Piperidines
  • ibrutinib
  • Rituximab
  • Adenine

Associated data

  • ClinicalTrials.gov/NCT02165397