Allogenic donor-derived cytokine-induced killer (CIK) cells as a safe post-transplant treatment for disease recurrence in the setting of HLA-mismatched donors Free

Background Cytokine-induced killer (CIK) cells are in vitro expanded CD3+, CD8+ and CD56+ T cells, sharing both T and NK cell features. CIK cells have the unique ability to recognize and kill malignant cells both through TCR-mediated cytotoxicity and non-MHC restricted recognition, the so‐called “dual‐functional capability”. CIK cells can mediate a potent graft versus leukemia (GvL) effect with a low risk of inducing graft versus host disease (GvHD). Our group published results from phase I/II studies demonstrating the feasibility and safety of clinical-grade allogeneic CIK cell production, associated with a low incidence of GvHD and adequate disease control (Introna M. et al. BBMT, 2017).

Objectives We have conducted a phase I/II trial using haploidentical or HLA-mismatched donor-derived CIK cells for post-hematopoietic cell transplantation (HCT) relapse (NCT03821519). The primary endpoint of the study was the incidence of acute grade II-IV GvHD at day +100 after the last infusion of CIK cells.

Methods CIK cells were obtained starting from 50 ml of peripheral blood or lymphocyte apheresis by the original haploidentical (67.9%) or mismatched unrelated (36.1%) donor. Cells were activated in culture in the presence of monoclonal antibodies against CD3 (OKT3), interferon-gamma (IFN-g), and interleukin-2 (IL-2) for 18-25 days of culture. From December 2018 to January 2025, 47 patients were enrolled. CIK cell production was successful in 44 patients (93,6%). For each patient three CIK infusions were scheduled (5x10⁶, 5x10⁶ and 10x10⁶ cells/kg) every 21 days and the cell target dose of 20x10⁶/Kg was reached in 36 patients (81,8%). Fourteen patients were not infused: 7 due to uncontrolled disease progression, 4 due to development of GvHD, 2 for infectious complications, and one patient withdrew from the study.

Results The primary endpoint of the phase I/II study was fully met in the 13 initial patients, since only one patient developed grade 1 skin 1 acute GvHD. This prompted us to launch a subsequent expanded, compassionate use program. Here we present the results from 28 patients who received at least 1 CIK cell infusion and had a follow up of at least 21 days after the last CIK cell infusion.

The median age was 61.9 years (range 54.1-65.3), with 57.1% of male patients. Underlying diseases included acute myeloid leukemia (AML, 75%), myelofibrosis (MF, 17.8%), acute lymphoblastic leukemia (ALL, 3.6%) and myelodysplastic syndrome (MDS, 3.6%). Median time to relapse from HCT was 5.3 months (range, 2.8-19.4). Disease status at enrollment was active disease (AD) in 8 patients (28.6%) and complete hematologic remission (CR) with detectable minimal residual disease (MRD) or mixed chimerism (MC) in 16 (57.1%). Four patients (14.3%) were enrolled in CR with negative MRD and full donor chimerism (FC) due to a high risk of relapse (prophylactic indication): 1 relapsed after the first HCT and achieved a second remission after intensive chemotherapy, 1 was in CR after a second HCT and 2 patients had a high-risk AML. Bridging therapy was used in 9 patients (34.6%) with an overall response rate of 44%. Disease status at the time of CIK cell infusion was AD in 5 patients (17.9%), CR with MRD/MC in 17 (60.7%) and CR with negative MRD/FC in 6 (21.4%). At day +21 after CIK cell infusion CR with negative MRD/FC was documented in 12 patients (42.9%), CR with positive MRD/MC in 7 (25%) and AD in 8 (28.6%). No additional acute GvHD was reported. One patient developed mild chronic GvHD. Starting from the first CIK infusion, the median follow-up is 9.6 months (IQR 4.6-20.1), with a median overall survival (OS) and progression-free survival (PFS) of 31.2 months (IQR 14.6-not reached) and 10.1 months (IQR 3.2-not reached), respectively. Patients in CR with positive MRD/MC at the time of CIK cell infusion, showed a numerically better OS and PFS compared to AD: median OS not reached vs 9.8 months (p=0.251) and median PFS 13.6 months vs 4.7 months (p=0.204) for CR with positive MRD/MC and AD respectively.

Conclusions In conclusion, allogeneic CIK cell infusion for post-HCT relapse confirms a safe profile also in the mismatched donor setting, with a promising anti-leukemia activity, particularly in MRD relapses or MC. Our results pave the way to plan an early prophylactic use of CIK cells in all patients at higher risk of relapse after HCT.