Abstract LB-070: Immune monitoring of PNK-007, an allogeneic, off the shelf NK cell in a Phase I study of acute myeloid leukemia

Celularity has developed a GMP platform for generating Placenta-derived intermediate Natural Killer cells (PNK-007): an allogeneic cytotoxic NK cell product culture-expanded and differentiated from placental CD34+ progenitor cells. In a 10 patient relapsed/refractory AML phase I study, PNK-007 infusion was evaluated following Cyclophosphamide-Fludarabine (Cy-Flu) conditioning treatment. Patients received a single PNK-007 infusion of 1 million (M) cells/kg, 3M cells/kg, or 10M cells/kg followed by rhIL-2 administered subcutaneously at 6M units every other day for up to 6 doses to facilitate PNK-007 persistence and expansion. Here, we report PNK-007 cell persistence, AML monitoring, and broader immune profiling from Phase I translational studies. PNK-007 persistence in the blood was observed between 7 and 28 days post infusion in patients dosed ≥ 3M cells/kg. Functional analysis of PNK-007 isolated from the blood of one patient indicated post-infusion NK cell effector activity. This included sustained expression of NKp30, NKp46, and DNAM-1 NK cell activating receptors. CD94, CD11a, and CD16 expression were increased relative to the pre-infusion cell product. CD57 and KIRs were absent at infusion, but were found on a subset of PNK-007 post-infusion indicating further NK maturation in vivo. Negligible expression of immunoinhibitory checkpoint receptors was observed on PNK-007 14 days post-infusion including PD-1, TIM3, and LAG3. Post-infusion PNK-007 cells stained positive for granzyme B, perforin, and secreted IFNγ, but not TNFα in response to acute activation. In the month following Cy-Flu conditioning, we observed limited reconstitution of myeloid and lymphoid cells, consistent with other reports investigating this patient population. T cells at day 7 were 35-65% CD4+Foxp3+ and sustained T cell expansion in two patients beyond day 14 was associated with elevated PD-1 expression. Patients were B and NK cell deficient and showed negligible monocyte reconstitution alongside neutropenia. Elevated monocyte and neutrophil counts in two patients occurred in the context of significantly increased AML burden in the blood. In those patients, between 25-50% of monocytes did not express MHC-II consistent with myeloid-derived suppressor cells. Our translational studies allow us to monitor PNK-007 cell persistence and maturation in addition to characterizing broader immune reconstitution from clinical samples. PNK-007 maturation data from this study are consistent with our preclinical models. We further show in this patient population that immune reconstitution appears compromised following Cy-Flu conditioning. Our data identify kinetics of PNK-007 persistence alongside hematopoietic recovery and AML disease. Citation Format: William van der Touw, Lin Kang, Julie M. Curtsinger, Vanessa Voskinarian-Berse, Bhavani Stout, Mohamad Hussein, Sarah A. Cooley, Jeffrey S. Miller, Robert Hariri, Xiaokui Zhang. Immune monitoring of PNK-007, an allogeneic, off the shelf NK cell in a Phase I study of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-070.