Consolidation with a short course of daratumumab in patients with AL amyloidosis or light chain deposition disease.

Daratumumab has major and rapid activity in AL amyloidosis with favourable toxicity. We used as a consolidation a short course of daratumumab in 25 patients with AL amyloidosis or light chain deposition disease (LCDD), who had not achieved a haematologic complete response (hemCR) after standard therapy with bortezomib, cyclophosphamide and dexamethasone (VCD). We evaluated minimal residual disease (MRD) and changes in the bone marrow (BM) microenvironment before and after consolidation using next generation flow cytometry (NGF). At the time of consolidation, 21 patients were in very good partial response (VGPR) and four in partial response (PR); all had detectable MRD. One month after consolidation completion, 8 patients (32%) achieved a hemCR, of whom 5 (20%) became also MRD negative. In the BM, we observed significant changes in B-cell precursors, naïve B-cells, T-cells, CD27+ NK & NKT cells, mast cells and erythroblasts. After a median follow-up of 25 months, none of the patients in hemCR has relapsed and all have achieved an organ response; a haematologic relapse occurred in 6/17 patients that did not achieve hemCR. In conclusion, consolidation with a short course of daratumumab can improve depth of response in patients with AL amyloidosis or LCDD and significantly affects BM environment.

Timing and impact of a deep response in the outcome of patients with systemic light chain (AL) amyloidosis.

A rapid and deep haematologic response is fundamental in order to improve outcomes of patients with AL amyloidosis. We evaluated the impact of timing and depth of haematologic response at early time points (at 1 and 3 months from the start of therapy) in 227 consecutive previously untreated AL patients, who received bortezomib-based primary therapy. After 1 month of therapy, 30.5% had ≥VGPR, 28% PR and 36% no response (NR), with 11% having iFLC <20 mg/L and 15% dFLC <10 mg/L. Deep haematologic response at 1 month (either ≥VGPR or iFLC <20 mg/L or dFLC <10 mg/L), was associated with a high organ response rate. The survival of patients with ≥VGPR was significantly better than those with PR and NR at 1-month landmark (p < .001) but this benefit was mainly driven by those with iFLC <20 mg/L. The depth of haematologic response at 1 month was significant across all Mayo stages. At 3 months, 46% of the patients had not significantly improved the depth of their response but even patients that improved their response from an iFLC ≥20 mg/L at 1 month to iFLC <20 mg/L at 3 months still had inferior outcome to those with an early deep response. Thus, in patients with AL amyloidosis, a very rapid and deep response is crucial, especially for those at high risk, targeting very low FLC levels within the first month of therapy.