RecruitingPhase 2Drug trialThe Effect of Daratumumab in Patients with Monoclonal Gammopathy of Renal Significance (MGRS) in FinlandThe goal of this clinical trial is to learn if drug daratumumab works to treat kidney diseases other than AL-amyloidosis that fall under the category of monoclonal gammopathy of renal significance (MGRS). The main questions it aims to answer are: Does daratumumab have an effect on the patients' renal function or the amount of proteinuria? Does daratumumab have an effect on the hematological endpoints evaluated by minimal residual disease (MRD) and the difference between involved and uninvolved free light chain (dFLC)? Also changes in quality of life (according to EORTC QLQ-C30) and mechanism of complement system activation are evaluated. The number of patiets with partial or very good partial hematological remission and the number of patients with adverse events related to daratumumab are also recorded.