P1443: AUTOLOGOUS NK CELLS AS CONSOLIDATION AFTER FRONT-LINE STEM CELL TRANSPLANTATION IN MULTIPLE MYELOMA: A LONG-TERM FOLLOW-UP

Abstract

Background: Immunotherapies have shown great anti-tumour effect in a variety of malignancies. In multiple myeloma (MM) antibodies, including bispecific T cell engagers, antibody-drug conjugates, and more recently, CAR T cells have reported exciting clinical results and many of them have been incorporated in the treatment armamentarium. Less is reported for NK cells, in particular autologous NK cells. Initial results from our first-in-human trial ACP-001 with autologous NK cells given as consolidation after front-line autologous stem cell transplantation (ASCT) were recently reported (Nahi et al., 2022, Cell Reports Medicine 3, 100508 February 15, 2022). It showed that the concept was feasible with good safety, including no SAEs, and promising efficacy. We here report the long-term clinical follow-up. Aims: The aim of this report was to investigate long-term safety, disease progression, second-line therapy and survival after autologous NK cell treatment. Methods: This first-in-human trial included six patients with newly diagnosed MM eligible for ASCT at the Karolinska University Hospital Huddinge in Sweden. After standard induction treatment (bortezomib, cyclophosphamide and dexamethasone (VCD) at the time) and ASCT with melphalan 200 mg/m2 (MEL200) the patients received three escalating doses of autologous activated and expanded NK cells. Clinical data on long-term safety, disease progression, second-line therapy and survival were captured from the patients’ electronical charts. Results: No subject were lost to follow-up or had withdrawn from the study. With a median follow-up from study inclusion of 6.9 (6.1-7.2) yrs, and 6.2 (5.4-6.7) yrs from the first NK cell infusion, there are no new reported AE related to the NK cell infusions. All six patients are alive with one subject still in first remission 6.8 yrs after inclusion. Five patients had disease progression 13-51 months after study inclusion and four of them underwent reinduction (VRD (n=2), KRD (n=1), KRD+dara (n=1)) followed by a second ASCT with MEL200. The fifth patient progressed within the first yr after ASCT and received VRD+dara. All five patients responded to second line treatment with PR (n=2), VGPR (n=2) and MRD negative (n=1) but subsequently progressed with a PFS2 ranging from 11.5 to 26.3 months. Summary/Conclusion: This long-term follow-up confirms the safety and feasibility of autologous NK cell therapy as consolidation after front line ASCT in MM. Autologous NK cell treatment in first line did not negatively impact the possibility to administer, or the outcome, of later treatments which is important with all new treatment options for patients with advanced MM.