Abstract CT550: Phase II study of acalabrutinib and an anti-CD20 monoclonal antibody in patients with anti-MAG mediated neuropathy

Background: Peripheral neuropathy occurs in 20-25% of patients with an IgM paraprotein and 40-50% of patients with an IgM monoclonal gammopathy have a detectable anti-myelin associated glycoprotein (MAG) antibody. The presence of an anti-MAG antibody is often associated with a chronic, progressive symmetric demyelinating polyneuropathy that can lead to sensory deficits and gait dysfunction, significantly altering a patient’s quality of life. Prior clinical trials have failed to demonstrate an effective long-term therapy for anti-MAG neuropathy. Additionally, the best manner to assess the evolution of this type of neuropathy has not been elucidated. We designed this clinical trial to evaluate a potential therapy for anti-MAG related neuropathy based on previous reports of subjective improvement in patients with anti-MAG neuropathy treated with rituximab or Bruton’s tyrosine kinase inhibitors. We included multiple neurologic outcome measures so their responsiveness and performance could be assessed in a clinical trial setting. Methods: This is a single-arm open-label phase II trial investigating the use of acalabrutinib and an anti-CD20 monoclonal antibody for the treatment of an IgM-associated anti-MAG mediated neuropathy. Eligible patients must have positive anti-MAG antibody titers with an IgM monoclonal gammopathy of undetermined significance (MGUS) or Waldenström macroglobulinemia (WM). Patients must have a predominantly sensory neuropathy characterized by demyelinating features in nerve conduction studies with a modified Rankin score of ≥1 with progressive symptoms or a modified Rankin score of ≥2. The ECOG performance status must be ≤2. Acceptable organ and marrow function are required. Prior exposure to chemotherapy, Bruton Tyrosine Kinase inhibitors, or other therapies for WM are not permitted except for steroids, IVIg, or an anti-CD20 monoclonal antibody given at least 90 days before study drug initiation. Approximately 33 patients will be enrolled in this study. Patients will be treated with acalabrutinib 100 mg orally twice daily on days 1-28 of each cycle and treatment will be administered until disease progression or unacceptable toxicity. Rituximab (or a biosimilar) will be administered on days 1, 8, 15, and 22 of cycles 1 and 4. The primary endpoint of this trial is to evaluate the overall hematologic response rate (defined as ≥25% reduction in serum IgM) associated with the treatment. The key secondary endpoint is to evaluate the proportion of patients that achieve improvement or stability in neuropathic symptoms based on the Inflammatory Rasch-built Overall Disability Scale (I-RODS) patient-reported disability scale. Additional secondary neurologic endpoints include the INCAT disability score, exam-based outcomes (the MRC distal sum score and INCAT-ISS), measures of function (10-meter walk test, 9-hole peg test), a pain scale, a fatigue scale (FSS), and a neuropathy-specific quality of life scale (IN-QOL). Additional secondary endpoints include time to next treatment, overall survival, hematologic response based on MYD88 and CXCR4 mutational status, change in bone marrow disease burden, and proportion of adverse events associated with treatment. This study is currently open and accruing patients. Clinical trial information: NCT05065554 Sponsor: AstraZeneca Citation Format: Shayna Sarosiek, Christopher T. Doughty, Andrew Branagan, Catherine A. Flynn, Kirsten Meid, Timothy P. White, Megan Little, Carly Leventoff, Steven P. Treon, Jorge J. Castillo. Phase II study of acalabrutinib and an anti-CD20 monoclonal antibody in patients with anti-MAG mediated neuropathy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT550.