P0244OVERTURNING THE CONVENTIONAL PYRAMID OF AL AMYLOIDOSIS MANAGEMENT: DARATUMUMAB ADMINISTERED AS MONOTHERAPY IN SEVERE PATIENTS WITH BIOPSY PROVEN RENAL INVOLVEMENT

Abstract

Abstract Background and Aims Immunoglobulin light chain amyloidosis (AL) with multi-organ involvement is characterized by poor outcome. Current treatment of AL targeting the underlying plasma cell clone has been adapted from the multiple myeloma (MM). Novel powerful drugs are expanding the therapeutic options. Daratumumab is a first-in-class anti-CD38 human antibody (IgG1κ) which proved to be effective in combination with bortezomib in MM refractory to conventional bortezomib-based regimens. Its effectiveness as a single agent and its safety in the treatment of AL amyloidosis is under study. Aim of the study: This study reports the experience with Daratumumab monotherapy in a series of severe patients with AL amyloidosis and multiorgan and biopsy-proven renal involvement. Method Five patients (2 males and 3 females), mean age 64 years (range 52-69) were treated with Daratumumab following antibody testing and extended RBC antigen phenotyping. Treatment protocol was as follows: 16 mg/kg Daratumumab i.v. administered weekly for 8 weeks, then 8 times every two weeks, and then monthly for 1 year. Premedication included oral paracetamol, and i.v. chlorphenamine and methylprednisolone. Results In patient #1, in dialysis, who was refractory to conventional therapies Daratumumab administration resulted in normalization of the FLC ratio with disappearance of serum M-component and Bence-Jones (BJ) proteinuria. In patient #2 who had a relapsing disease, Daratumumab treatment resulted in a rapid decrease of proteinuria (from 6.8 to 2.7gr/24 hours at the 16th dose) and N-terminal propeptide (NT-pro-BNP) levels (from 1844 pg/ml to 330 pg/ml) with disappearance of serum M-component and BJ proteinuria and normalization of the FLC ratio. Patient #3 was treated front-line. He had an impressive decrease of proteinuria from 9.3 to 2.2 gr/24 hrs and NT-proBNP levels (from 850 pg/ml to 225 pg/ml) with normalization of FLC ratio and disappearance of serum M-component. In patient #4, who was intolerant to conventional regimens, Daratumumab therapy resulted in decrease in proteinuria, disappearance of serum M-component and improvement in the FLC ratio, which were paralleled by a reduction of NT-proBNP levels. Patient #5 had a relapsing disease. Daratumumab achieved a decrease of proteinuria (from 2.5 to 1 gr/24 hrs9, a decrease of serum M-component with increase of FLC ratio (0.29, nv: 0.31 – 1.56). This was the only patient who experienced an infusion reaction during the first dose (grade 1). The 4 patients with still preserved renal function also showed renal response with sCr improvement or stabilization and a decrease in proteinuria levels These data were paralleled by the reduction of NT-proBNP values in the 3 patients with cardiac involvement. Conclusion Daratumumab monotherapy resulted in the disappearance of M-proteins in every patient with FLC ratio normalization in 4 out of 5 subjects and impressive decrease of proteinuria and pro-BNP values proving to be an effective therapeutic option for pretreated/naïve patients with severe AL with renal involvement.