Can we make a better match or mismatch with KIR genotyping?

Killer instincts: natural killer cells as multifactorial cancer immunotherapy

Natural killer (NK) cells integrate heterogeneous signals for activation and inhibition using germline-encoded receptors. These receptors are stochastically co-expressed, and their concurrent engagement and signaling can adjust the sensitivity of individual cells to putative targets. Against cancers, which mutate and evolve under therapeutic and immunologic pressure, the diversity for recognition provided by NK cells may be key to comprehensive cancer control. NK cells are already being trialled as adoptive cell therapy and targets for immunotherapeutic agents. However, strategies to leverage their naturally occurring diversity and agility have not yet been developed. In this review, we discuss the receptors and signaling pathways through which signals for activation or inhibition are generated in NK cells, focusing on their roles in cancer and potential as targets for immunotherapies. Finally, we consider the impacts of receptor co-expression and the potential to engage multiple pathways of NK cell reactivity to maximize the scope and strength of antitumor activities.

Phase I non-randomized clinical trial of allogeneic natural killer cells infusion in acute myeloid leukemia patients

INTRODUCTION

A new type of immune cell transplantation called allogeneic NK cell infusion is proposed as a potential universal off-the-shelf cell product for adoptive immune cell therapy in hematologic malignancies.

DESIGN

A multicentral phase I non-randomized clinical trial was conducted to assess the safety, feasibility, and potential efficacy of adoptively infused NK cells in patients with refractory/relapsed AML. We evaluated the feasibility of the trial by considering cell production, patient selection, and treatment protocol.

METHOD

Allogeneic NK cells were produced from random healthy unrelated donors; 10 patients were selected according to the inclusion criteria and were included in two groups in case of NK cell dose escalation. Two cell infusions were given, spaced 7 days apart, following a lymphodepletion conditioning regimen of fludarabin-endoxan administered 7 days before the first infusion. The intervention safety was scored using Common Terminology Criteria for Adverse Events (CTCAE) based on variations in vital signs due to cell infusion. NK cell chimerism, tumor burden, and duration of relapse were considered to be components of efficacy. The pilot feasibility evaluation was checked using the CONSORT platform.

RESULTS

The NK cell infusion procedure was well tolerated, and no grade 2-5 toxicities related (possible or probable) to PB-NK cell infusion were observed. Four patients developed grade 1 transient chills, headaches, vomiting, and bone pain following each PB-NK cell infusion that were not required hospitalization. One of these patients (p01) died because of severe acute respiratory syndrome. Of 9 evaluable patients, 6 (66.6%) showed stable disease (SD) and 3 (33.3%) presented progressive disease (PD). Of 6 SD patients, 2 (p08 and p09) remained alive in SD and 3 patients (p04, p05 and p07) converted to PD at 9 months after infusion of NK cells, and 1 (p03) was not evaluable due to follow-up loss. No patient achieved complete remission.

CONCLUSION

The study demonstrated the feasibility and safety of adoptive transfer of random healthy unrelated donor PB-NK cells in refractory/relapsed AML patients and supports continued study in phase II clinical trials in relapsed/refractory AML patients.

Treatment of recurrent pediatric myelodysplastic syndrome post hematopoietic stem cell transplantation

Treatment of recurrent myelodysplastic syndrome (MDS) after hematopoietic cell transplantation (HCT) remains challenging. We present a 4-year-old girl experiencing early MDS relapse post-HCT treated with a multimodal strategy encompassing a second HCT and innovative targeted therapies. We underscore the potential of a comprehensive treatment approach in managing recurrent pediatric MDS.

Natural Killer Cell Engagers (NKCEs): a new frontier in cancer immunotherapy

Natural Killer (NK) cells are a type of innate lymphoid cells that play a crucial role in immunity by killing virally infected or tumor cells and secreting cytokines and chemokines. NK cell-mediated immunotherapy has emerged as a promising approach for cancer treatment due to its safety and effectiveness. NK cell engagers (NKCEs), such as BiKE (bispecific killer cell engager) or TriKE (trispecific killer cell engager), are a novel class of antibody-based therapeutics that exhibit several advantages over other cancer immunotherapies harnessing NK cells. By bridging NK and tumor cells, NKCEs activate NK cells and lead to tumor cell lysis. A growing number of NKCEs are currently undergoing development, with some already in clinical trials. However, there is a need for more comprehensive studies to determine how the molecular design of NKCEs affects their functionality and manufacturability, which are crucial for their development as off-the-shelf drugs for cancer treatment. In this review, we summarize current knowledge on NKCE development and discuss critical factors required for the production of effective NKCEs.

KIR2DS4 and its variant KIR1D in KIR-AA genotype donors showed differential survival impact in patients with lymphoid disease after HLA-matched unrelated hematopoietic stem cell transplantation

Previous studies illustrated associations between presence of activating killer cell immunoglobulin-like receptor (KIR) genes and lower susceptibility to hematologic malignancies in humans. In addition, favorable hematopoietic stem cell transplantation (HSCT) outcomes were reported in patients, who received transplants from donors with KIR genotypes dominant for activating KIR receptors. However, the association of activating KIR genes on an allelic level with disease and their impact on HSCT outcome has been only scarcely investigated. To this end, we genotyped a large transplantation cohort for KIR two Ig domains and short cytoplasmic tail 4 (KIR2DS4) polymorphisms and investigated their association with disease. We next investigated the impact of KIR-AA genotype donor KIR2DS4 polymorphisms (AA/KIR2DS4 versus (vs.) AA/KIR1D), on clinical outcome of HSCT in patient subgroups (myeloid vs. lymphoid). Among 2810 transplant pairs, 68.8% (n=1934) were 10/10 human leukocyte antigen (HLA) matched and 31.2% (n=876) were 9/10 HLA-matched. The distribution of KIR one Ig domain (KIR1D) in patients vs. donors was equal (P value = 0.205). Multivariate analysis in 10/10 HLA-matched patients with lymphoid disease showed improved HSCT outcome (overall survival (OS): hazard ratio (HR) 0.62, P=0.002; disease free survival (DFS): HR 0.70, P=0.011; graft-versus-host disease free and relapse-free survival (GRFS): HR 0.67, P=0.002; non-relapse mortality (NRM): HR 0.55, P<0.001) when they received grafts from AA/KIR1D donors. This effect was not seen in either 9/10 HLA-matched patients with lymphoid disease or patients with myeloid disease. Our study indicates that the presence of KIR1D alleles is not associated with disease in patients and interestingly, using grafts from AA/KIR1D donors translated into a beneficial survival outcome in 10/10 HLA-matched patients with lymphoid disease.

KIR genotype and haplotype frequencies in the multi-ethnic population of Malaysia

Killer cell immunoglobulin-like receptors (KIR) genotype and haplotype frequencies have been reported to vary distinctly between populations, which in turn contributes to variation in the alloreactivity of natural killer (NK) cells. Utilizing the diverse KIR genes to identify suitable transplant donors would prove challenging in multi-ethnic countries, even more in resource-limited countries where KIR genotyping has not been established. In this study, we determined the KIR genotypes from 124 unrelated Malaysians consisting of the Malays, Chinese, Indians, and aboriginal people through polymerase chain reaction sequence-specific primer (PCR-SSP) genotyping and employing an expectation-maximization (EM) algorithm to assign haplotypes based on pre-established reference haplotypes. A total of 27 distinct KIR haplotypes were discerned with higher frequencies of haplotype A (55.2%) than haplotype B (44.8%). The most frequent haplotypes were cA01:tA01 (55.2%), cB01:tB01 (18.1%), and cB02:tA01 (13.3%), while the least frequent haplotypes were cB03:tB01 (1.2%), cB04:tB03 (0.4%), and cB03:tA01 (0.4%). Several haplotypes were identified to be unique to a specific ethnic group. The genotype with the highest frequency was genotype AB (71.8%), followed by AA (19.4%), and BB (8.9%). The Indians exhibited the lowest genotype AA but the highest genotype BB, whereas genotype BB was absent in the aboriginal people. Despite the limitations, the genotype and haplotypes in the Malaysian population were successfully highlighted. The identification of ethnic-specific KIR genotypes and haplotypes provides the first step to utilizing KIR in identifying suitable transplant donors to further improve the transplant outcome in the Malaysian population.

Natural killer cells in antitumour adoptive cell immunotherapy

Natural killer (NK) cells comprise a unique population of innate lymphoid cells endowed with intrinsic abilities to identify and eliminate virally infected cells and tumour cells. Possessing multiple cytotoxicity mechanisms and the ability to modulate the immune response through cytokine production, NK cells play a pivotal role in anticancer immunity. This role was elucidated nearly two decades ago, when NK cells, used as immunotherapeutic agents, showed safety and efficacy in the treatment of patients with advanced-stage leukaemia. In recent years, following the paradigm-shifting successes of chimeric antigen receptor (CAR)-engineered adoptive T cell therapy and the advancement in technologies that can turn cells into powerful antitumour weapons, the interest in NK cells as a candidate for immunotherapy has grown exponentially. Strategies for the development of NK cell-based therapies focus on enhancing NK cell potency and persistence through co-stimulatory signalling, checkpoint inhibition and cytokine armouring, and aim to redirect NK cell specificity to the tumour through expression of CAR or the use of engager molecules. In the clinic, the first generation of NK cell therapies have delivered promising results, showing encouraging efficacy and remarkable safety, thus driving great enthusiasm for continued innovation. In this Review, we describe the various approaches to augment NK cell cytotoxicity and longevity, evaluate challenges and opportunities, and reflect on how lessons learned from the clinic will guide the design of next-generation NK cell products that will address the unique complexities of each cancer.

Decoding the multidimensional signatures of resident and expanded natural killer cells generated from perinatal blood

Natural killer (NK) cells are lymphocytes and play a pivotal role in innate and adaptive immune responses against infections and malignancies. Longitudinal studies have indicated the feasibility of perinatal blood for large-scale NK cell generation, yet the systematic and detailed comparations of the signatures of resident and expanded NK cells (rNKs, eNKs) are largely obscure. Herein, we harvested rNKs from umbilical cord blood (rUC-NKs) and placental blood (rP-NKs) as well as the corresponding eNKs (eUC-NKs, eP-NKs). Furthermore, the biological properties and transcriptomic signatures including cellular subpopulations, cytotoxicity, gene expression profiling, genetic characteristics, signaling pathways and gene set-related biological process were investigated. The enriched rNKs and eNKs exhibited diversity in biomarker expression pattern, and eNKs with higher percentages of NKG2D⁺, NKG2A⁺, NKp44⁺ and NKp46⁺ subsets. rNKs or eNKs with different origins showed more similarities in transcriptomic signatures than those with the same origin. Our data revealed multifaceted similarities and differences of the indicated rNKs and pNKs both at the cellular and molecular levels. Our findings provide new references for further dissecting the efficacy and molecular mechanisms of rNKs and eNKs, which will collectively benefit the fundamental and translational studies of NK cell-based immunotherapy.

Haploidentical vs Matched Unrelated vs Matched Sibling Donor HCT with Post-Transplantation Cyclophosphamide

With the use of post-transplantation cyclophosphamide (PTCy), the outcomes of mismatched related donor hematopoietic cell transplantation (HCT) are now approaching those of matched donor HCT. Here we compared haploidentical donor HCT versus HLA-matched unrelated donor (MUD) HCT and HLA-identical sibling donor (MSD) HCT in a cohort in which all patients received PTCy for graft-versus-host disease (GVHD) prophylaxis. We included 661 patients (275 haploidentical, 246 MUD, and 140 MSD HCT). The most common diagnoses were acute myelogenous leukemia and myelodysplastic syndrome. In multivariate analysis, the haploidentical group was found to have significantly higher nonrelapse mortality (NRM) (hazard ratio [HR], 3.2; 95% confidence interval [CI], 2 to 4.9; P < .001) and inferior progression-free survival (HR, 1.8; 95% CI, 1.4 to 2.4; P < .001) and overall survival (OS; HR, 2.2; 95% CI, 1.6 to 3; P < .001) compared with the MUD group. Relapse was the most common cause of death in all groups. Among causes of NRM, the haploidentical group had more infection-related deaths and fewer GVHD-related deaths than the other groups. The haploidentical group also had a higher risk of viral and fungal infections, grade ≥3 hemorrhagic cystitis, and cardiovascular toxicities and slower reconstitution of CD4, CD8, and regulatory T cells but faster reconstitution of natural killer cells. In an exploratory analysis, older patients with older donors (>50 years for both) appeared to have particularly high NRM and lower OS in the haploidentical group compared with the other groups. Our data suggest that even with the use of PTCy, the outcomes of haploidentical HCT are inferior to those of HLA-matched donor HCT.

Enhancing Natural Killer Cell Targeting of Pediatric Sarcoma

Osteosarcoma, Ewing sarcoma (EWS), and rhabdomyosarcoma (RMS) are the most common pediatric sarcomas. Conventional therapy for these sarcomas comprises neoadjuvant and adjuvant chemotherapy, surgical resection of the primary tumor and/or radiation therapy. Patients with metastatic, relapsed, or refractory tumors have a dismal prognosis due to resistance to these conventional therapies. Therefore, innovative therapeutic interventions, such as immunotherapy, are urgently needed. Recently, cancer research has focused attention on natural killer (NK) cells due their innate ability to recognize and kill tumor cells. Osteosarcoma, EWS and RMS, are known to be sensitive to NK cell cytotoxicity in vitro. In the clinical setting however, NK cell cytotoxicity against sarcoma cells has been mainly studied in the context of allogeneic stem cell transplantation, where a rapid immune reconstitution of NK cells plays a key role in the control of the disease, known as graft-versus-tumor effect. In this review, we discuss the evidence for the current and future strategies to enhance the NK cell-versus-pediatric sarcoma effect, with a clinical focus. The different approaches encompass enhancing antibody-dependent NK cell cytotoxicity, counteracting the NK cell mechanisms of self-tolerance, and developing adoptive NK cell therapy including chimeric antigen receptor-expressing NK cells.

Differential Effect of Graft-versus-Host Disease on Survival in Acute Leukemia according to Donor Type

PURPOSE

The anti-leukemic activity of allogeneic hematopoietic cell transplantation (HCT) depends on both the intensity of conditioning regimen and the strength of the graft-versus-leukemia (GVL) effect. However, it is unclear whether the sensitivity of the GVL effects differs between donor type and graft source.

EXPERIMENTAL DESIGN

We retrospectively evaluated the effect of acute and chronic graft-versus-host disease (GVHD) on transplant outcomes for adults with acute leukemia (n = 6,548) between 2007 and 2017 using a Japanese database. In all analyses, we separately evaluated three distinct cohorts based on donor type [(8/8 allele-matched sibling donor, 8/8 allele-matched unrelated donor, and unrelated single-cord blood (UCB)].

RESULTS

The multivariate analysis, in which the development of GVHD was treated as a time-dependent covariate, showed a reductive effect of grade I-II acute GVHD on treatment failure (defined as 1-leukemia-free survival; P < 0.001), overall mortality (OM; P < 0.001), relapse (P < 0.001), and non-relapse mortality (NRM; P < 0.001) in patients receiving from UCB. A reductive effect of limited chronic GVHD on treatment failure (P < 0.001), OM (P < 0.001), and NRM (P < 0.001) was also shown in patients receiving from UCB. However, these effects were not always shown in patients receiving from other donors. The beneficial effects of mild acute and chronic GVHD after UCB transplantation on treatment failure were noted relatively in subgroups of patients with acute myelogenous leukemia and a non-remission status.

CONCLUSIONS

These data suggested that the development of mild GVHD could improve survival after UCB transplantation for acute leukemia.

Reduced leukemia relapse through cytomegalovirus reactivation in killer cell immunoglobulin-like receptor-ligand-mismatched cord blood transplantation

Cytomegalovirus (CMV) reactivation in cord blood transplantation (CBT) may result in the proliferation and maturation of natural killer (NK) cells. Similarly, a mismatch of the killer cell immunoglobulin-like receptor (KIR)-ligand induces NK cell activation. Therefore, if CMV reactivation occurs in the presence of KIR-ligand mismatch, it might improve CBT outcomes. We assessed the difference in the effect of CMV reactivation in the presence of KIR-ligand mismatch on disease relapse in the graft-versus-host direction. A total of 2840 patients with acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, and chronic myeloid leukemia were analyzed. Among those with a HLA-Bw4/A3/A11 (KIR3DL-ligand) mismatch, CMV reactivation up to 100 days following CBT had a favorable impact on relapse (18.9% vs. 32.9%, P = 0.0149). However, this effect was not observed in cases without the KIR3DL-ligand mismatch or in those with or without a HLA-C1/C2 (KIR2DL-ligand) mismatch. The multivariate analysis suggested that CMV reactivation had a favorable effect on relapse only in cases with a KIR3DL-ligand mismatch (hazard ratio 0.54, P = 0.032). Moreover, the interaction effect between CMV reactivation and KIR3DL-ligand mismatch on relapse was significant (P = 0.039). Thus, our study reveals the association between KIR-ligand mismatches and CMV reactivation, which will enhance CBT outcomes.

Clinical development of natural killer cells expressing chimeric antigen receptors

Both natural killer (NK) cells and T cells demonstrate potent antitumor responses in many settings. NK cells, unlike T cells, are not the primary mediators of graft-versus-host disease (GVHD). Redirection of T cells with chimeric antigen receptors (CAR) has helped to overcome tumor escape from endogenous T cells. NK cells expressing CARs are a promising new therapy to treat malignancy. Clinical biomanufacturing of CAR NK cells can begin with NK cells derived from many different sources including adult peripheral blood-derived NK cells, cord blood-derived NK cells, cell line-derived NK cells, or stem cell-derived NK cells. Manufacturing protocols may include isolation of NK cells, activation, expansion, and genetic modification to express the chimeric antigen receptors. Clinical trials have tested both unmodified and CAR NK cells with encouraging results. The next stage in clinical development of CAR NK cells represents a highly exciting new frontier in clinical cell therapy as well as understanding basic NK cell biology. The purpose of this review is to provide the reader with a fundamental understanding of the core concepts in CAR NK cell manufacturing, specifically highlighting differences between CAR T cell manufacturing and focusing on future directions in the field.

Use of CAR-Transduced Natural Killer Cells in CD19-Positive Lymphoid Tumors

BACKGROUND

Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy has shown remarkable clinical efficacy in B-cell cancers. However, CAR T cells can induce substantial toxic effects, and the manufacture of the cells is complex. Natural killer (NK) cells that have been modified to express an anti-CD19 CAR have the potential to overcome these limitations.

METHODS

In this phase 1 and 2 trial, we administered HLA-mismatched anti-CD19 CAR-NK cells derived from cord blood to 11 patients with relapsed or refractory CD19-positive cancers (non-Hodgkin's lymphoma or chronic lymphocytic leukemia [CLL]). NK cells were transduced with a retroviral vector expressing genes that encode anti-CD19 CAR, interleukin-15, and inducible caspase 9 as a safety switch. The cells were expanded ex vivo and administered in a single infusion at one of three doses (1×10⁵, 1×10⁶, or 1×10⁷ CAR-NK cells per kilogram of body weight) after lymphodepleting chemotherapy.

RESULTS

The administration of CAR-NK cells was not associated with the development of cytokine release syndrome, neurotoxicity, or graft-versus-host disease, and there was no increase in the levels of inflammatory cytokines, including interleukin-6, over baseline. The maximum tolerated dose was not reached. Of the 11 patients who were treated, 8 (73%) had a response; of these patients, 7 (4 with lymphoma and 3 with CLL) had a complete remission, and 1 had remission of the Richter's transformation component but had persistent CLL. Responses were rapid and seen within 30 days after infusion at all dose levels. The infused CAR-NK cells expanded and persisted at low levels for at least 12 months.

CONCLUSIONS

Among 11 patients with relapsed or refractory CD19-positive cancers, a majority had a response to treatment with CAR-NK cells without the development of major toxic effects. (Funded by the M.D. Anderson Cancer Center CLL and Lymphoma Moonshot and the National Institutes of Health; ClinicalTrials.gov number, NCT03056339.).

Presence of centromeric but absence of telomeric group B KIR haplotypes in stem cell donors improve leukaemia control after HSCT for childhood ALL

Although allogeneic hematopoietic stem-cell transplantation (HSCT) provides high cure rates for children with high-risk acute lymphoblastic leukaemia (ALL), relapses remain the main cause of treatment failure. Whereas donor killer cell immunoglobulin-like receptor (KIR) genotype was shown to impact on relapse incidence in adult myeloid leukaemia similar studies in paediatric ALL are largely missing. Effect of donor KIR genotype on transplant outcome was evaluated in 317 children receiving a first myeloablative HSCT from an HLA-matched unrelated donor or sibling within the prospective ALL-SCT-BFM-2003 trial. Analysis of donor KIR gene polymorphism revealed that centromeric presence and telomeric absence of KIR B haplotypes was associated with reduced relapse risk. A centromeric/telomeric KIR score (ct-KIR score) integrating these observations correlated with relapse risk (hazard ratio (HR) 0.58; P = 0.002) while it had no impact on graft-versus-host disease or non-relapse mortality. In multivariable analyses ct-KIR score was associated with reduced relapse risk (HR 0.58; P = 0.003) and a trend towards improved event-free survival (HR 0.76; P = 0.059). This effect proved independent of MRD level prior to HSCT. Our data suggest that in children with ALL undergoing HSCT after myeloablative conditioning, donor selection based on KIR genotyping holds promise to improve clinical outcome by decreasing relapse risk and prolonged event-free survival.

Optimal Donor Selection During Verification Process: Which Factors Are Worth Knowing?

BACKGROUND

The selection of optimal donor is crucial for successful hematopoietic stem cell transplantation (HSCT). Thereby, it is appropriate to know, in addition to basic human leukocyte antigen (HLA) gene matches, other immunogenic or nonimmunogenic parameters predicting the outcome of transplant.

OBJECTIVE

A unified approach is necessary to provide a comprehensive view of the patient-donor compatibility characterization outside of standard HLA genes. The approach should be applicable as a tool for optimizing procedures for extended donor typing and/or verification typing of a donor.

METHODS

The study used the summary, unification, and innovation of existing practical knowledge and experience of the Czech National Marrow Donor Registry of various factors beyond HLA matching with impact on transplant outcome.

RESULTS

An information technology system-implemented procedure (a verification algorithm) is presented as the decision support approach for prematurely discarding less suitable donors from the transplantation process. It is intended primarily for the transplant specialist to help establish optimal procedures for verifying and determining donor critical factors.

CONCLUSIONS

A process defining HLAs, killer cell immunoglobulin-like receptors, and cytokine typing strategies was proposed to provide support to a transplant specialist in refining the choice of a suitable donor.