Zanubrutinib Treatment in Patients With IgM Monoclonal Gammopathy and Antri-MAG Related Polyneuropathy

The objective of this investigator-initiated phase II single-arm open-label clinical trial is to investigate neurological response rate, safety and tolerability of Zanubrutinib 320 mg daily in combination with Rituximab 375 mg/m2 (standard therapy) for the treatment of immunoglobulin M monoclonal gammopathy of unknown significance (IgM MGUS) related polyneuropathy with Myelin Associated Glycoprotein antibodies (anti-MAG). 42 adult patients will be included in two Dutch hospitals (University Medical Center Utrecht and Amsterdam University Medical Center). This trial consists of a 6-month treatment period, after which the hematological response will be evaluated. Adequately responding participants (at least partial response) will be treated for an additional 6 months, after which hematological response will be re-evaluated. Participants with at least a very good partial response will remain on treatment. Non-responding participants will be followed for clinical outcomes only. The total study period per participant will be 36 months.