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

Treatment will consist of Rituximab administered at 375 mg/m2 intravenously on Cycle 1 Days 1, 8, 15, 22 only (4 total infusions). The experimental part of the treatment will consist of Zanubrutinib, given once daily 320 mg (4 x 80 mg capsules). Although Zanubrutinib is taken continuously, therapy cycles are calculated per 28 days. Participants will be treated for a minimum of 6 cycles per protocol. Participants who still use Zanubrutinib at the end of study can continue indefinitely until registration and reimbursement in the Netherlands.