High-affinity Natural Killer Research Articles

Case report: PD-L1-targeted high-affinity natural killer cells and IL-15 superagonist N-803-based therapy extend overall survival of advanced metastatic pancreatic cancer patients

BackgroundMetastatic pancreatic cancer (mPC) is an aggressive form of cancer with a poor prognosis and few therapeutic options after failure of the second-line treatment. Induction of immunogenic cell death (ICD) by use of relatively low-dose chemo- or radiation therapy, enhancement of immune responses by the IL-15 superagonist N-803 (Anktiva®), and targeting of programmed death receptor ligand 1 (PD-L1)-expressing cells may offer a therapeutic approach to refractory mPC with the potential to increase overall survival (OS).MethodsFrom late 2019 to 2021, single-patient Investigational New Drug (spIND) protocols for five mPC patients were designed and approved that generally comprised combined Abraxane (nab-paclitaxel) and gemcitabine therapy with experimental therapeutics N-803, PD-L1-targeted high-affinity natural killer (PD-L1 t-haNK) cells, and aldoxorubicin, a serum albumin-binding doxorubicin prodrug. Some patients also received stereotactic body radiation therapy (SBRT), cyclophosphamide, pembrolizumab, nivolumab, and/or experimental ETBX-051 (brachyury) and/or ETBX-061 (MUC1) vaccines. Duration of spIND treatment and responses, for some patients including imaging and carbohydrate antigen 19-9 (CA19-9) levels, and OS from initial diagnosis and the start of spIND therapy were assessed.FindingsThe line/duration of spIND therapy was, for patients 1 through 5, respectively, second line/6.4 months, sixth line/3.5 months, third line/25.4 months, third line/7.4 months, and fourth line/23.2 months. OS from the commencement of spIND therapy was 13, 4.8, 26.9, 9, and 23.2 months, and OS from diagnosis was 22, 21, 42, 13, and 33 months for patients 1 through 5, respectively.ConclusionsThe OS from the initiation of spIND for all patients exceeded the reported OS for the greater-than-second-line mPC patients and, for four of five patients, second-line therapy. The OS of 13, 26.9, and 23.2 months for three patients is particularly notable. The findings here support the ongoing clinical investigations of N-803 and PD-L1 t-haNK cells in combination therapy.

Recurrent pancreatic cancer treated with N-803 and PD-L1 t-haNK followed by an EGFR-targeted nanocell drug conjugate.

Multimodal temporal therapy orchestrated to leverage immunotherapy, tumor-targeted chemotherapy, and natural killer (NK) cell therapy may provide an opportunity to induce immunogenic cell death for tumor response and increased survival in patients with recurrent cancer. The interleukin-15 (IL-15) superagonist N-803, an enhancer of NK cells, CD4 + T cells, cytotoxic CD8 + T cells, and memory T-cell activity, combined with off-the-shelf PD-L1-targeted high-affinity NK (PD-L1 t-haNK) cells represent novel immunotherapies designed to overcome an immunosuppressive tumor microenvironment (TME). The epidermal growth factor receptor-targeted antibody-nanocell conjugate E-EDV-D682 provides tumor-targeted chemotherapy in the form of its anthracycline metabolite PNU159682 (nemorubicin) cargo and is currently being studied in combination with immunomodulatory EDVs delivering the adjuvant α-galactosyl ceramide (GC). Here, we report the compassionate use treatment of this combination in a patient with recurrent, metastatic pancreatic cancer (mPC) after 3 lines of therapy. Under the initial single-patient Investigational New Drug (spIND) protocol, the patient received N-803, PD-L1 t-haNK cells, and the albumin doxorubicin conjugate aldoxorubicin for ~27 months. The patient's disease became stable on this regimen, and a transient complete response was observed by ~14 months of therapy. Due to progression, a second spIND protocol was designed whereby the patient received E-EDV-D682 plus EDV-GC for more than 24 months, which resulted in stable disease and the patient's continued survival at the time this report was written. The patient's extended survival despite the dire prognosis associated with recurrent mPC points to the merits of this temporal combination regimen in overcoming immuno-chemo resistance with enhanced immune activity required for tumor response and extended survival.

Cryopreservation of Natural Killer Cells Pre-Complexed with Innate Cell Engagers.

Innate cell engager (ICE®) constructs are bispecific tetravalent antibodies targeting specific tumor antigens and simultaneously engaging natural killer (NK) cell and macrophage receptors for the destruction of tumor cells. Pre-complexing of ICE® constructs with adoptive NK cells is a novel approach to enhance NK cell activity. The suitability of such complexes for cryopreservation, whilst retaining the biological activity and specificity, may enable the development of off-the-shelf NK cell products. This study investigates the binding affinity of ICE® constructs targeting EpCAM and NK cell receptors CD16A, NKG2D, or NKp46 to the corresponding antigens, the ICE® antitumor activity, and feasibility of cryopreservation. Cell surface retention assays using primary NK cells confirmed a substantially slower ICE® construct dissociation kinetics compared with control molecules, suggesting the formation of durable complexes independently of the CD16A polymorphism. The high-affinity NK cell and EpCAM/CD16A ICE® complexes were superior to those engaging NKG2D or NKp46 receptors when tested for the NK-cell-mediated elimination of EpCAM-expressing tumor cells. Moreover, the potency and efficacy of these complexes were unaffected after a single freeze–thaw cycle. CD16A-selective ICE® drug candidates complexed with NK cells hold promise as novel cryopreserved off-the-shelf NK cell products with chimeric antigen receptor-like NK cell properties, capable of effective depletion of tumor cells.

Exploiting off-target effects of estrogen deprivation to sensitize estrogen receptor negative breast cancer to immune killing

BackgroundThere are highly effective treatment strategies for estrogen receptor (ER)+, progesterone receptor (PR)+, and HER2+ breast cancers; however, there are limited targeted therapeutic strategies for the 10%–15% of women who...

PD-L1 targeting high-affinity NK (t-haNK) cells induce direct antitumor effects and target suppressive MDSC populations

BackgroundAlthough immune checkpoint inhibitors have revolutionized cancer treatment, clinical benefit with this class of agents has been limited to a subset of patients. Hence, more effective means to target tumor...

Efficient ADCC killing of meningioma by avelumab and a high-affinity natural killer cell line, haNK.

Meningiomas are the most common adult primary tumor of the central nervous system, but there are no known effective medical therapies for recurrent meningioma, particularly for World Health Organization grade II and III tumors. Meningiomas arise from the meninges, located outside the blood-brain barrier, and therefore may be directly targeted by antibody-mediated immunotherapy. We found that programmed cell death ligand 1 (PD-L1) was highly expressed in multiple human malignant meningioma cell lines and patient tumor samples. PD-L1 was targeted with the anti-PD-L1 antibody avelumab and directed natural killer cells to mediate antibody-dependent cellular cytotoxicity (ADCC) of PD-L1-expressing meningioma tumors both in vitro and in vivo. ADCC of meningioma cells was significantly increased in target cells that upregulated PD-L1 expression and, conversely, abrogated in tumor cells that were depleted of PD-L1. Additionally, the high-affinity natural killer cell line, haNK, outperformed healthy donor NK cells in meningioma ADCC. Together, these data support a clinical trial designed to target PD-L1 with avelumab and haNK cells, potentially offering a novel immunotherapeutic approach for patients with malignant meningioma.

Correlation between circulating cell-free RNA biomarkers and response during combination immunotherapy in previously refractory metastatic TNBC patients.

e14027 Background: A commercial liquid biopsy test was included as an exploratory component of an integrated immunotherapy clinical trial in previously refractory metastatic TNBC patients, combining innate, high-affinity natural killer cell (haNK) therapy with adenoviral and yeast-based vaccines and an IL-15 superagonist (NCT 03387085). The purpose of the study was to assess the utility of cell-free circulating RNA (cfRNA) as a predictor of treatment response. Methods: Blood was drawn from trial participants at baseline and at 2-6 week intervals throughout the treatment protocol. cfRNA and cfDNA were extracted from plasma and tested for analytes by quantitative PCR (qPCR) in a CLIA and CAP certified laboratory. This study is based on the analysis of 18 the cfRNA analytes (AR, PD-L1, CTLA-4, LAG-3, EGFR, HER2, ERCC1, TIM-3, MGMT, RRM1, SLC29A1, TOP1, TOP2A, TOP2B, TUBB3, TYMP, TYMS, XRCC1) in six patients that had at least three testing time points; new patient recruitment and serial testing are ongoing. The relative expression of each RNA analyte was normalized by beta-actin. Tumor size was evaluated by imaging using the RECIST criteria. Results: The amount and variability of cfRNA was positively correlated with the tumor size. As cfRNA quantity and variability increased or decreased, a corresponding increase or decrease in tumor size was observed, respectively. Not all 18 genes showed consistent patterns of change across the six patients, however the average expression and variability of the 18 genes showed evidence of a correlation with tumor size change from baseline (p-values = 0.08 and 0.03, respectively). Only trace levels of PD-L1 expression were observed in all 6 patients at baseline, prior to the initiation of the combination immunotherapy. Among the 5 patients that showed a reduction in tumor size of at least 10%, 4 also showed an associated increase in cfRNA PD-L1 expression from nearly 0 to normalized values between 2.1 and 6.8. Conclusions: Exploratory analysis in an ongoing combination immunotherapy clinical trial for TNBC showed that increasing and decreasing cfRNA levels are correlated with increasing and decreasing tumor size, respectively. Increased PD-L1 cfRNA levels are correlated with beneficial treatment response. Liquid biopsy of cfRNA could provide an effective biomarker of treatment response. Clinical trial information: NCT03387085.

Direct and antibody-dependent cell-mediated cytotoxicity of head and neck squamous cell carcinoma cells by high-affinity natural killer cells

High affinity natural killer cells (haNKs) are a cell therapy product capable of mediating both direct and antibody-dependent cell-mediated cytotoxicity (ADCC). These cells may be particularly useful in tumors that escape T-cell anti-tumor immunity by harboring antigen processing and presentation defects. Here, we demonstrated that haNKs directly kill both HPV-positive and negative head and neck squamous cell carcinoma cells. Variable tumor cell sensitivity to haNK direct cytotoxicity did not correlated with MHC class I chain-related protein A or B (MICA or MICB) expression. Importantly, haNK killing was significantly enhanced via ADCC mediated by cetuximab or avelumab in cells with higher baseline EGFR or PD-L1 expression, respectively. The ability of IFNγ to induce tumor cell PD-L1 expression correlated with enhanced PD-L1-specific ADCC. IFNγ induced neither tumor cell EGFR expression nor EGFR-specific ADCC. Although a single dose of 8 Gy IR did not appear to directly enhance susceptibility to haNK killing alone, enhanced PD-L1- and EGFR-mediated ADCC after IR correlated with increased PD-L1 and EGFR expression in one of four models. This pre-clinical evidence supports the investigation of haNK cellular therapy in combination with ADCC-mediating mAbs, with or without IR, in the clinical trial setting for patients with advanced HNSCCs. Given the MHC-unrestricted nature of this treatment, it may represent an opportunity to treat patients with non-T-cell inflamed tumors.

Immunotherapy utilizing the combination of natural killer\u2013 and antibody dependent cellular cytotoxicity (ADCC)\u2013mediating agents with poly (ADP-ribose) polymerase (PARP) inhibition

BackgroundPoly (ADP-ribose) polymerase inhibitors (PARPi) prevent single-stranded DNA repair. Olaparib is a PARPi approved for the treatment of BRCA mutant ovarian and breast carcinoma. Emerging clinical data suggest a benefit of combining olaparib with immunotherapy in prostate cancer patients both with and without somatic BRCA mutations.MethodsWe examined if olaparib, when combined with IgG1 antibody-dependent cellular cytotoxicity (ADCC)-mediating monoclonal antibodies (mAbs) cetuximab (anti-EGFR), or avelumab (anti-PD-L1), would increase tumor cell sensitivity to killing by natural killer (NK) cells independently of BRCA status or mAb target upregulation. BRCA mutant and BRCA wildtype (WT) prostate carcinoma cell lines were pretreated with olaparib and then exposed to NK cells in the presence or absence of cetuximab or avelumab.ResultsNK-mediated killing was significantly increased in both cell lines and was further increased using the ADCC-mediating mAbs. Pre-exposure of NK cells to recombinant IL-15/IL-15Rα further increased the lysis of olaparib treated tumor cells. In addition, olaparib treated tumor cells were killed to a significantly greater degree by engineered high-affinity NK cells (haNK). We show here for the first time that (a) olaparib significantly increased tumor cell sensitivity to NK killing and ADCC in both BRCA WT and BRCA mutant prostate carcinoma cells, independent of PD-L1 or EGFR modulation; (b) mechanistically, treatment with olaparib upregulated death receptor TRAIL-R2; and (c) olaparib significantly enhanced NK killing of additional tumor types, including breast, non-small cell lung carcinoma, and chordoma.ConclusionsThese studies support the combined use of NK- and ADCC-mediating agents with correctly timed PARP inhibition.

Glypican-1 as a novel immunotherapeutic target in prostate cancer.

174 Background: New effective therapies for men with prostate cancer are desperately needed. Recently, cancer immunotherapy has emerged as an important new treatment strategy for prostate cancer and for castrate resistant prostate cancer (CRPC). Multiple studies have identified the heparan sulfate proteoglycan-1 Glypican 1 (GPC-1) as being overexpressed in different cancers, and also as being a possible marker of poor prognosis in several solid tumor cancers. GPC-1 has been recently identified as a potential marker for prostate cancer. The MIL-38 monoclonal antibody detects GPC-1 and an IgG1 chimeric version of this antibody has been developed for preclinical studies. Here we sought to examine MIL-38 binding to a panel of prostate cancer cell lines and examine its feasibility as a novel immunotherapeutic agent targeting GPC-1 in prostate cancer Methods: Expression of GPC-1 in CRPC cell lines was examined by Flow cytometry and Western Blotting using MIL-38 as the detector antibody. The competency of GPC-1 as an immunotherapeutic target was assessed via chimeric MIL-38 induced Antibody Dependent Cell Cytotoxicity (ADCC) using high affinity Natural Killer cells (haNKs) in vitro . Results: Flow cytometry and Western blot assessments of normal prostatic epithelial cells (i.e. RWPE-1) and cells from prostate cancer cell lines (i.e. PC-3, 22RV1, DU-145, VCaP, LNCaP, CWR-R1, and LAPC-4) revealed that only cancer cells expressed GPC-1. Enzalutamide resistant cell lines demonstrated higher expression of GPC-1 than their respective parental line. ADCC assays demonstrated enhanced haNK – prostate cancer cell cytotoxicity in the presence of chimeric MIL-38 anti-GPC-1 antibody, while the IgG1 isotype control had no effect. Conclusions: GPC-1 protein was expressed by most prostate cancer cell lines, including enhanced expression by enzalutamide resistant cells. Preliminary in vitro ADCC assay results revealed the potential utility of GPC-1 as an immunotherapeutic target in prostate cancer.

A potential therapy for chordoma via antibody-dependent cell-mediated cytotoxicity employing NK or high-affinity NK cells in combination with cetuximab

OBJECTIVE Chordoma is a rare bone tumor derived from the notochord and is resistant to conventional therapies such as chemotherapy, radiotherapy, and targeting therapeutics. Expression of epidermal growth factor receptor (EGFR) in a large proportion of chordoma specimens indicates a potential target for therapeutic intervention. In this study the authors investigated the potential role of the anti-EGFR antibody cetuximab in immunotherapy for chordoma. METHODS Since cetuximab is a monoclonal antibody of the IgG1 isotype, it has the potential to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) employing natural killer (NK) cells as effectors. Polymorphisms in the CD16 allele expressed on NK cells have been shown to influence the degree of ADCC of tumor cells, with the high-affinity valine (V)/V allele being responsible for more lysis than the V/phenylalanine (F) or FF allele. Unfortunately, however, only approximately 10% of the population expresses the VV allele on NK cells. An NK cell line, NK-92, has now been engineered to endogenously express IL-2 and the high-affinity CD16 allele. These irradiated high-affinity (ha)NK cells were analyzed for lysis of chordoma cells with and without cetuximab, and the levels of lysis observed in ADCC were compared with those of NK cells from donors expressing the VV, VF, and FF alleles. RESULTS Here the authors demonstrate for the first time 1) that cetuximab in combination with NK cells can mediate ADCC of chordoma cells; 2) the influence of the NK CD16 polymorphism in cetuximab-mediated ADCC for chordoma cell lysis; 3) that engineered haNK cells-that is, cells transduced to express the CD16 V158 FcγRIIIa receptor-bind cetuximab with similar affinity to normal NK cells expressing the high-affinity VV allele; and 4) that irradiated haNK cells induce ADCC with cetuximab in chordoma cells. CONCLUSIONS These studies provide rationale for the use of cetuximab in combination with irradiated haNK cells for therapy for chordoma.

Combination Therapy with Daratumumab and CAR-NK Targeting CS1 for Multiple Myeloma

Daratumumab (Dara), a targeted therapy utilizing a monoclonal antibody against CD38, and its combination with other are becoming a new standard of care treatment in multiple myeloma (MM). Recently, chimeric antigen receptor (CAR) T cell immunotherapy has been successful in the clinic for the treatment of leukemia and lymphoma. Our preliminary data suggest that both CS1-CAR T cells and CS1-CAR NK cells are effective in eradicating MM cells in vitro and in vivo (Chu et al., 2014, Leukemia and Chu et al., 2014, Clinical Cancer Research). In this study, we investigated the combination therapy with Dara and CS1-CAR NK cells for the treatment of relapsed MM.We first showed that that in MM patients, CD38brightCD138─CD34─CD20+CD27+ MM cancer stem-like cells (CSCs) express CS1 at levels much higher than any other cells, and are susceptible to being eradicated by CS1-CAR NK cells. However, CD34+hematopoietic stem cells from bone marrow of healthy donors do not express CS1. These data suggest that CS1-CAR NK cells can target MM CSCs, and thus may prevent relapse of MM, as ample evidence shows that relapsed or recurrent tumor cells are derived from CSCs.We also demonstrated that CD38 is highly expressed on NK and MM cells. Dara triggered IFN-γ and GZMB expression (p< 0.01) in primary human NK cells, even in the absence of crosslinking with tumor cells. Interestingly, the increase IFN-γ expression can be validated in the CD16 (+) haNK-92 (high-affinity natural killer cells), but not in the parental NK-92 cell line. Blocking the recognition between CD16 and Dara (an IgG1 mAb) with an Fc blocking Ab completely impaired Dara-induced IFN-γ and GZMB expression, indicating that Dara-induced NK cell activation is CD16-dependent. Mechanistically, Dara significantly induced phosphorylation of NFkB and STAT1, indicating that Dara induces IFN-γ and GZMB in NK cells, which may occur through CD16 and be mediated downstream by STAT1 and NFkB. We also found that Dara failed to stimulate GZMB and IFN-γ expression in CD38(-) CD16(+) NK cells, while successful in stimulating CD38(+) CD16(+) NK cells, indicating that Dara induces NK cell activation, which requires not only the binding between CD16 and Fc fragment of Dara, but also the CD38 signaling pathway. Furthermore, we found that Dara mediated cytotoxicity of NK cells against MM cells through antibody-dependent cell-mediated cytotoxicity (ADCC) against CD38-positive (e.g., MM1.S), but not CD38-negative (e.g., U266), which can be blocked by CD16 blocking Ab. Moreover, Dara displays ADCC effects in CD16(+) NK cells but not CD16(-) NK cells. When CD16(+) NK cells were armed with the CS1-CAR, ADCC is still observed against CD38(+) MM cells at low effector to target ratios, i.e., Dara still enhances cytotoxicity of CS1-CAR NK cells, which already have enhanced cytotoxicity.We observed that Dara-induced NK cell ADCC against CD38(+) MM MM1.S cells led to increased T cell proliferation and activation in a co-culture system including dendritic cells. This effect was not observed when MM U266 cells were included as the NK cell target. Out data are consistent with that recent discovery by DiLillo and Ravetch showing that engagement of monoclonal antibody can induce an antitumor vaccine effects (David J et al., Cell, 2015).To tested Dara affects NK cell survival, immunoblotting was performed with anti-cleaved Caspase-3 and anti-cleaved PARP-1 antibodies. We demonstrated that apoptotic activity was increased in both CD16(+)NK cells (primary NK and haNK-92) and parental CD16(-)NK-92 cells treated with Dara for 24 h in a dose-dependent manner. Unlike Dara’s positive effects on CD16(+) NK cells (i.e. stimulating IFN-γ production and ADCC), induction of apoptosis seems to be CD16-independent, as parental NK-92 cells, which are CD16(-), also showed an increased levels of apoptosis induced by Dara. We are testing whether the apoptosis induction is dependent on the antigen for Dara, because as mentioned above, both primary NK cells, and modified as well as unmodified NK-92 cells, that were CD38 (+).In conclusion, our study demonstrates that the combination of Dara and CS1-CAR NK cells, which target two different tumor-associated antigens, both of which have potent anti-MM efficacy, may show additive or synergistic effects; however due to the positive and negative effects of Dara on NK cells, sequential treatment rather than a concomitant treatment modality should be considered. DisclosuresNo relevant conflicts of interest to declare.

Abstract 2302: An ‘off the shelf,’ GMP-grade, IL-2-independent NK cell line expressing the high-affinity Fc-receptor to augment antibody therapeutics

Abstract A number of approved IgG1 monoclonal antibodies (mAb) used in cancer therapy, including trastuzumab, cetuximab, and rituximab, depend on natural killer (NK) cell-mediated antibody dependent cell-mediated cytotoxicity (ADCC) to induce cancer cell death, mediated through the Fcγ receptor (FcγR). Multiple studies report that survival benefit is significantly improved in cancer patients receiving IgG1 antibody therapy who have NK cells that express the high-affinity FcγRIIIa receptor (CD16-158V). Only 12% of the normal human population, however, is homozygous for expression of this high-affinity variant CD16. We hypothesized that infusion of an NK-92 cell line modified to express CD16-158V (high-affinity NK cells [haNK]) in combination with an IgG1 mAb may result in superior antitumor effects compared with IgG1 mAb alone. A GMP-grade plasmid-transfected variant of NK-92 expressing the high-affinity CD16 receptor was developed utilizing a novel transfection vector containing the erIL-2 gene, enabling the resulting haNK cells to grow independently of IL-2. Using limiting dilution, clones having identical surface molecule expression to the parent cell line were generated and shown to have long-term expression of CD16. The haNK cells displayed high ADCC in combination with rituximab, trastuzumab, and daratumumab against target cell lines that were not killed by the parental NK-92 cells. Of note, despite non-viral transfection, the plasmid is fully integrated into chromosome 5. The haNK cell line secretes about 200 pg/106 cells of IL-2, and like the parental NK-92 cell line, produces enough IFNγ to potentially stimulate an adaptive immune response. A GMP-grade master cell bank of haNK cells has been established; haNK cells can be cryopreserved with retention of ADCC activity. In vivo studies demonstrated the efficacy of haNK cells. In a multiple myeloma model of CD38+ NCI-H929 cells xenografted into NOD/SCID gamma null (NSG) mice, treatment with haNK cells plus the anti-CD38 mAb daratumumab led to prolonged survival versus mice treated with haNK cells plus an isotype control (log rank p = 0.0169), demonstrating therapeutically relevant in vivo ADCC. haNK cells have also been transfected with various CARs using mRNA, thereby enabling this platform to make a bispecific effector cell product. In summary, haNK cells are a potent and versatile platform for cellular immunotherapy, and clinical trials of these novel “off the shelf” high-affinity NK cells are scheduled for 2016. Citation Format: Laurent Boissel, Hans Klingemann, Kerry Campbell, Karen Nichols, Frances Toneguzzo, Paula Marcus, Brent Williams, Armand Keating, Patrick Soon-Shiong. An ‘off the shelf,’ GMP-grade, IL-2-independent NK cell line expressing the high-affinity Fc-receptor to augment antibody therapeutics. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2302.

KIR and HLA Genotypes Influence Clinical Outcome in Multiple Myeloma Patients Treated with SAR650984 (Anti-CD38) in Combination with Lenalidomide and Dexamethasone

SAR650984 (SAR) is a humanized IgG1 monoclonal antibody that binds selectively to the human CD38 receptor. TCD11863 (TCD) is a phase Ib trial evaluating the combination of SAR with lenalidomide (LEN) and dexamethasone (Dex) in relapsed/refractory multiple myeloma (RRMM) [NCT01749969]. Because natural killer (NK) cells contribute to antibody-dependent cellular cytotoxicity, we hypothesized that immunogenetic factors contributing to NK cell function would influence clinical activity among RRMM patients treated with SAR/LEN/Dex. We therefore prospectively performed KIR and HLA class I genotyping on 31 RRMM patients enrolled in TCD. We used the typing data to stratify patients based on predicted differences in KIR3DL1, HLA-Bw4 receptor-ligand binding affinities. We used the Kaplan-Meier method to estimate probabilities of progression-free survival (PFS) and time to progression (TTP) among all 31 treated patients, with the log-rank test to evaluate differences in survival distributions based on patient KIR and HLA genotype status, the cox proportional hazard model to examine the association of the hazard of failure with genotype status, and the Fischer’s exact test to compare overall response rates (ORR) among 28 evaluable patients. P-values are provided for exploratory purpose, since the study was not powered for formal comparison of efficacy variables by genotype subgroup. Of the 31 patients, 12 had a high-affinity KIR3DL1,HLA-B Bw4-80Ile compound genotype (including 3 with both HLA-A and HLA-BBw4-80Ile), and 19 lacked the KIR3DL1,HLA-B Bw4-80Ile genotype, with 7 of these 19 patients possessing a low-affinity KIR3DL1, HLA-Bw4-80Thr genotype (including 1 with HLA-ABw4-80Ile), 7 with a missing ligand or receptor genotype, and 5 with a KIR3DL1, HLA-ABw4-80Ile genotype not containing other HLA-B Bw4 alleles. Presence of a high-affinity KIR3DL1,HLA-B Bw4-80Ile genotype (n=12, 10 evaluable for ORR) was associated with high ORR and prolonged TTP and PFS relative to patients lacking KIR3DL1,HLA-B Bw4-80Ile (n=19, 18 evaluable for ORR; 90% ORR vs. 56%, P=0.10; TTP HR 0.11, [95% CI] 0.08-0.68, P<0.01; PFS HR 0.22, [95% CI] 0.05-0.98, P=0.03). The benefit of KIR3DL1,HLA-B Bw4-80Ile varied with gene dose, such that the proportion of patients remaining on treatment increased with increasing copy number of HLA-B Bw4-80Ile from 0 (n=19) to 1 (n=8) to 2 (n=4) copies, with 21% remaining on treatment at 6 months vs. 50% vs. 100% (TTP P=0.02). Because HLA-A Bw4-80Ile ligands bind KIR3DL1 with different strength and specificity than HLA-B Bw4-80Ile ligands, we separated patients with KIR3DL1, HLA-ABw4-80Ile from patients with KIR3DL1, HLA-BBw4-80Ile and found a specific association of prolonged PFS among patients with a pure high-affinity KIR3DL1,HLA-B Bw4-80Ile genotype (n=9; 7 patients remain on treatment at 6 months, 2 AEs), compared with patients with a pure KIR3DL1, HLA-A Bw4-80Ile genotype (n=5; 2 on treatment at 6 months, 3 PDs), a KIR3DL1, HLA-ABw4-80Ile genotype containing other HLA-B Bw4 alleles (n=4), a pure low-affinity KIR3DL1, HLA-Bw4-80Thr genotype (n=6; 2 on treatment at 6 months, 3 PDs, and 1 AE), and a missing KIR3DL1 ligand or receptor genotype (n=7; 3 on treatment at 6 months, 3 PDs, and 1 AE) [PFS P=0.02]. While the number of prior therapies (2-4 vs. 5-7 vs. 8-12, P=0.02) and ISS stage at the start of treatment (stage I to III, P<0.01) also influenced PFS, possession of KIR3DL1,HLA-B Bw4-80Ile was associated with prolonged PFS within each of these subgroups. In summary, a KIR3DL1, HLA-B Bw4-80Ile genotype predictive of high-affinity NK cell receptor-ligand interactions and potent NK cell licensing correlated with increased ORR and PFS among patients treated with SAR/LEN/Dex, although the small sample size requires validation in future studies. DisclosuresMartin:Sanofi: Research Funding. Venstrom:Sanofi Oncology: Research Funding.