Rituximab is a type of protein called an antibody that attacks the cluster of differentiation 20 (CD20), a protein found on B-cells like WM. Rituximab is approved by the FDA for treating non-Hodgkin lymphoma (NHL). Dexamethasone is a steroid and is similar to the hormones naturally produced by the adrenal glands; it prevents the release of substances that cause inflammation. Rituximab and dexamethasone are often used to treat WM, alone or in combination with other drugs. Combinations with rituximab, dexamethasone and other proteasome inhibitors have shown good response rates in WM participants. Ixazomib is a proteasome inhibitor; thus the investigator swill investigate if the combination of Ixazomib, Rituximab, and Dexamethasone is also active in WM.