Placental circulating T cells: a novel, allogeneic CAR-T cell platform with preserved T-cell stemness, more favorable cytokine profile, and durable efficacy compared to adult PBMC-derived CAR-T

BACKGROUND

Chimeric antigen receptor (CAR)-T cell quality and stemness are associated with responsiveness, durability, and memory formation, which benefit clinical responses. Autologous T cell starting material across patients with cancer is variable and CAR-T expansion or potency can fail during manufacture. Thus, strategies to develop allogeneic CAR-T platforms including the identification and expansion of T cell subpopulations that correspond with CAR-T potency are an active area of investigation. Here, we compared CAR-T cells generated from healthy adult peripheral blood T cells versus placental circulating T (P-T) cells.

METHODS

CAR-T cells from healthy adult peripheral blood mononuclear cells (PBMCs) and P-T cells were generated using the same protocol. CAR-T cells were characterized in detail by a combination of multiparameter flow cytometry, functional assays, and RNA sequencing. In vivo antitumor efficacy and persistence of CAR-T cells were evaluated in a Daudi lymphoma xenograft model.

RESULTS

P-T cells possess stemness advantages compared with T cells from adult PBMCs. P-T cells are uniformly naïve prior to culture initiation, maintain longer telomeres, resist immune checkpoint upregulation, and resist further differentiation compared with PBMC T cells during CD19 CAR-T manufacture. P-T CD19 CAR-T cells are equally cytotoxic as PBMC-CD19 CAR-T cells but produce less interferon gamma in response to lymphoma. Transcriptome analysis shows P-T CD19 CAR-T cells retain a stem-like gene signature, strongly associate with naïve T cells, an early memory phenotype, and a unique CD4 T cell signature compared with PBMC-CD19 CAR-T cells, which enrich for exhaustion and stimulated memory T cell signatures. Consistent with functional data, P-T CD19 CAR-T cells exhibit attenuated inflammatory cytokine and chemokine gene signatures. In a murine in vivo model, P-T CD19 CAR-T cells eliminate lymphoma beyond 90 days. PBMC-CD19 CAR-T cells provide a non-durable benefit, which only delays disease onset.

CONCLUSION

We identified characteristics of T cell stemness enriched in P-T CD19 CAR-T which are deficient in PBMC-derived products and translate into response durability in vivo. Our findings demonstrate that placental circulating T cells are a valuable cell source for allogeneic CAR-T products. Stemness advantages inherent to P-T cells translate to in vivo persistence advantages and long-term durable activity.

A phase I/IIa open label, nonrandomized, multicenter study of CYNK-101 in combination with trastuzumab and pembrolizumab in patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction (G/GEJ) adenocarcinoma

TPS478

Background: CYNK-101 is a human placental hematopoietic stem/progenitor cell derived NK cell product, that is genetically modified to express a variant of CD16, FcγRIII, via lentiviral vector transduction. The CD16 variant has amino acid modifications to enable high affinity and proteolytic cleavage-resistance for ADCC enhancement. Results from preclinical studies demonstrated enhanced ADCC activity of CYNK-101 in combination with trastuzumab against HER2+ gastric cancer cell lines in vitro, ex vivo and in vivo. Methods: A Phase I/IIa study is a first-line treatment of patients with locally advanced unresectable or metastatic HER2 positive gastric or gastroesophageal junction (G/GEJ) adenocarcinoma. Patients are required to have confirmation of HER2 positivity defined as either IHC 3+ or IHC 2+ with a positive FISH or FISH + alone. Following the completion of screening assessments, patients are enrolled to the initial induction period of the trial and receive pembrolizumab, trastuzumab and a fluoropyrimidine/platinum based-chemotherapy for up to six 21-day cycles. In Phase I, patients may skip the initial induction period if they had previously been treated with pembrolizumab or, trastuzumab and a fluoropyrimidine/platinum based-chemotherapy and have not achieved an adequate response. Patients complete a disease assessment and then proceed to a lymphodepletion regimen of cyclophosphamide 900 mg/m2 and fludarabine 30 mg/m2 with MESNA for 3 days. Following 2 days of rest, the NK-cell re-induction period of the study begins with pembrolizumab 200 mg and trastuzumab 6 mg/kg on Day 1 of that cycle and 6M IU of rhIL-2 with CYNK-101 on days 1, 8, 15. CYNK-101 will be administered based on the calculated number of transduced cells per body weight as measured in kilograms (kg). Two dose levels of CYNK-101 (36 x 106 transduced cells/kg, and 72 x 106 transduced cells/kg) will be evaluated for the NK-Cell reinduction period during the Phase 1 portion of the study in a standard “3+3” dose escalation fashion. Once the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) is determined in Phase I, the designated dosing Cohort level of the NK-Cell re-induction period will be used for the Phase IIa Expansion portion of the study. Both study periods will contain maintenance dosing of pembrolizumab 200 mg, trastuzumab 6 mg/kg and 6M IU rhIL-2 with 3.6 x 106 transduced cells/kg of CYNK-101 on Day 1 of a 21-day cycle. Endpoints: Primary endpoints for Phase I, include the incidence of adverse events defined as dose-limiting toxicities (DLTs). Phase IIa will evaluate efficacy as measured by overall response rate and a complete response rate as determined by RECIST 1.1. Approximately 52 patients are planned for this Phase I/IIa study. Clinical trial information: NCT05207722 .

Human placental hematopoietic stem cell-derived natural killer cells (CYNK) recognize and eliminate influenza A virus-infected cells

Influenza A virus (IAV) infections are a significant recurrent threat to public health and a significant burden on global economy, highlighting the need for developing more effective therapies. Natural killer (NK) cells play a pivotal role in the control of pulmonary IAV infection, however, little is known about the therapeutic potential of adoptively transferred NK cells for viral infections. Here, we investigated the antiviral activity of CYNK, human placental hematopoietic stem cell-derived NK cells, against IAV infection in vitro. Virus infection induced the expression of NK cell activating ligands on respiratory epithelial cells, resulting in enhanced recognition by CYNK cells. Upon co-culture with IAV-infected epithelial cells, CYNK exhibited elevated degranulation and increased production of IFN-γ, TNF-α and GM-CSF in a virus dose-dependent manner. Furthermore, CYNK showed virus dose-dependent cytotoxicity against IAV-infected cells. The antiviral activity of CYNK was mediated by NKp46 and NKG2D. Together, these data demonstrate that CYNK possesses potent antiviral function against IAV and warrant clinical investigations for adoptive NK cell therapies against viral infections.

A phase I/IIa, open-label, multicenter, non-randomized clinical trial to assess the safety and efficacy of CYNK-001 in combination with recombinant human interleukin 2 in adults with recurrent resection eligible IDH1 wild-type glioblastoma (GBM)

TPS2080

Background: CYNK-001 is a CD56+CD3- enriched, off-the-shelf, allogeneic natural killer (NK) cell product expanded from placental CD34 cells. CYNK-001 exhibits in vitro cytotoxicity against patient-derived GBM cell lines and secretes cytolytic cytokines during co-culture with cancer cells. CYNK-001 administered via the intracranial (IC) route exhibited in vivo antitumor activity in a U-87MG orthotopic mouse model. Methods: A Phase I/IIa clinical trial is enrolling IDH1 wild-type GBM patients at first or second recurrence with contrast-enhancing measurable disease (per RANO criteria) who are candidate for surgical resection. Screening MRI scans for inclusion are performed within 14 days prior to Day -5 lymphodepletion with Cyclophosphamide 900mg/m2 and fludarabine 30mg/m2 plus mesna. Using a standard 3+3 dose escalation schema, patients will receive the first cycle of CYNK-001 intravenously (IV) at an initial dose of 2.4 x109 cells on Days 1, 8 and 15 after lymphodepletion. Cell supportive IL-2 at 6M IU administered SQ on Days 1, 3, 5, 8, 10, 12, and 15 within 3 hours prior to CYNK-001 IV infusion where applicable. Cycle 2 begins with surgical resection on Day 22 in which CYNK-001 is administered directly into the tumor cavity wall at an initial dose of 100 x106 NK cells and an Ommaya catheter placement. Subsequent CYNK-001 IC administrations via the Ommaya are on days 29 and 36 with 6M IU IL-2 SQ. DLT is evaluated for all dosing cohorts from day 1 to 7 days post last dose of cycle 2. Once a maximum tolerated dose is identified, a safety lead-in cohort with an additional 3 cycles of CYNK-001 IC will be administered prior to initiating the Phase IIa portion of the study. Endpoints: The primary endpoint is dose-limiting toxicity for the Phase I analysis and 6-month progression free survival post tumor resection for the Phase IIa component. Post-resected tumor tissue will be characterized for effector immune cell function and immune suppression with assessments directed at CYNK-001 tumor distribution using methodology developed at Celularity Inc. Approximately 66 patients are planned for this Phase I/IIa study. Approximately 66 patients are planned for this Phase I/IIa study. Clinical trial information: NCT05218408.

Abstract CT201: Early report of a phase I/II study of human placental hematopoietic stem cell derived natural killer cells (CYNK-001) for the treatment of adults with COVID-19 (NCT04365101)

Background CYNK-001 is a cryopreserved, allogeneic, off-the-shelf natural killer (NK) cell investigational product derived from placental CD34+ cells. CYNK-001 exhibits cytotoxicity against various cancer cell types as well as virally infected cells and secretes immunomodulatory cytokines upon target activation. This is the first study to evaluate the safety and potential efficacy of CYNK-001 to treat patients (pts) with SARS-CoV-2, previously investigated in only solid tumor and hematologic malignancies. Methods Placental CD34+ cells were cultured in the presence of cytokines for 35 days to generate CYNK-001 under the cGMP conditions. Pts with a positive RT-PCR test for SARS-CoV-2 from the nasopharynx and having moderate to severe illness, not requiring intensive care support or mechanical ventilation, were eligible. All enrolled pts received best supportive care. In the Phase 1 trial focused on safety of administration, a total of 14 pts will receive up to 3 CYNK-001 infusions on Days 1 (1.5e8 cells), 4 (6e8 cells), 7 (6e8 cells). Efficacy was measured by SARS-CoV-2 clearance as measured by RT-PCR testing and clinical measures of improvement, including pulmonary status, and inflammatory marker changes. Results Four of 6 pts treated to date were evaluable at the time of submission. All had multiple medical co-morbidities. Peripheral oxygen saturation (Sp02) ranged between 88-92% on up to 8L of supplemental oxygen and all had evidence of multilobar pneumonia on chest radiography. Two pts had received no prior therapy for COVID-19. The other 2 pts received remdesivir and dexamethasone, with the 4th pt also receiving convalescent plasma. In all 4 pts, all infusions were well tolerated. In 3 of 4 pts, oxygenation improved after the first infusion of CYNK-001 and radiographic improvement was noted. The 4th pt developed progressive hypoxemia prior to the administration of the first dose of CYNK-001, requiring more than 30L of supplemental oxygen delivered by facemask to support a Sp02>90%. All 3 doses of CYNK-001 were administered, but oxygen requirements increased. Twelve days after first CYNK-001 dose, the pt declined mechanical ventilation and died of respiratory failure. Attribution to CYNK-001 could not be ruled out. The remaining 3 pts were discharged with an average follow-up of 16 (9-32) days after first infusion. Conclusion In the first study to measure the safety and potential efficacy of CYNK-001 infusions to treat pts with COVID-19 disease, infusions were generally well tolerated with one Grade 5 event of hypoxic respiratory failure. Early efficacy has been seen in 3 of 4 pts with improvement of oxygenation, inflammatory markers, and radiographic findings. Once Phase 1 is completed, the Phase 2 portion of the study will test this approach in a randomized fashion compared to best available therapy to confirm efficacy of this approach.

Citation Format: Corey Casper, Leonid Groysman, Vinay Malhotra, Eric Whitman, Stacy Herb, Erica Rave, Alan Lew, Cristina Goman, Zachary Sagawa, Monica Thakar, Victoria Lacasse, Cherie Daly, Shuyang He, Lin Kang, Sharmila Koppisetti, Tanel Mahlakõiv, Sunday Osokoya, William van der Touw, Junhong Zhu, Greg Berk, Xiaokui Zhang, Andrew Pecora, Robert Hariri. Early report of a phase I/II study of human placental hematopoietic stem cell derived natural killer cells (CYNK-001) for the treatment of adults with COVID-19 (NCT04365101) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT201.

Abstract 513: Simultaneous monitoring of immune cell subsets and minimal residual disease in bone marrow aspirate using full-spectrum flow cytometry

Background: Treatment options for multiple myeloma (MM) patients have expanded and improved outcomes. Autologous stem cell transplantation, immunomodulatory drugs (IMiDs), monoclonal antibodies, and CAR-T cell therapy have direct and indirect immune modulating effects that favor patient responses. However, the majority of patients still relapse due to minimal residual disease (MRD). Current flow cytometry methods that monitor MRD and bone marrow immune cell populations require large cell numbers to achieve assay sensitivity. New approaches are needed to better capture high-resolution data given the limited recovery of bone marrow specimens. Here, we describe the simultaneous monitoring of immune cell subsets in the bone marrow and MRD using a single antibody panel and the Cytek Aurora full-spectrum flow cytometry platform. In a Phase 1/2 study to evaluate an off-the-shelf, allogeneic human placental-derived NK cell product in newly diagnosed MM, this method enables correlative analysis of MRD state with immune profiling.

Methods: Bone marrow aspirate (BMA) from 5 patients with newly diagnosed MM following induction therapy were collected for MRD assessment in parallel using next-generation sequencing (NGS) and MRD evaluation by flow cytometry. BMA was lysed of red blood cells and 2x107 cells were stained using TCRγδ, CD16, CD8, CD33, CD117, CD11c, CD3, CD19, CD1c, CD45, CD38, CD14, HLA-DR, CD138, CD141, CD34, CD25, CRTH2, CD56, CD303, CD4, and CD127. Cells were acquired on a Cytek Aurora 4 laser system followed by data analysis using FlowJo software. MRD threshold of 10-5 was used for positivity for both modalities of testing.

Results: The 22-parameter panel resolved the majority of immune cell subpopulations present in the bone marrow and peripheral blood including granulocytes, B cells, plasma cells, monocytes, MDSCs, plasmacytoid and classical dendritic cells, NK cells, and T cells (CD4, CD8, NKT, γδT, Treg). Total plasma cells were identified based upon CD38+CD138+ co-staining. Myeloma cells could be identified based on aberrant expression of CD45, CD19, CD56, and CD117. Of the five patients evaluated, one patient was MRD negative by NGS and flow cytometry with no detectable cells. One patient was MRD negative by NGS (0.7x10-5) but positive by flow cytometry (1.53x10-5). The three remaining patients were positive by NGS (6.32x10-4, 7.51x10-4, and 4.78x10-4) and flow cytometry (2.46x10-4, 5.37x10-4, and 9.74x10-4).

Conclusion: Utilizing full-spectrum flow cytometry provides streamlined monitoring of MRD while capturing BMA-associated immune cell populations. Compared to validated measures of MRD testing by NGS, our flow cytometry approach provides comparable results while profiling myeloid and lymphoid cell subpopulations, which enables correlative analyses of underlying pathophysiological activities.

Citation Format: William van der Touw, Bhavani Stout, James McCauley, Tanel Mahlakõiv, Robert Hariri, Xiaokui Zhang. Simultaneous monitoring of immune cell subsets and minimal residual disease in bone marrow aspirate using full-spectrum flow cytometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 513.

CBLB ablation with CRISPR/Cas9 enhances cytotoxicity of human placental stem cell-derived NK cells for cancer immunotherapy

BACKGROUND

Tumors often develop resistance to surveillance by endogenous immune cells, which include natural killer (NK) cells. Ex vivo activated and/or expanded NK cells demonstrate cytotoxicity against various tumor cells and are promising therapeutics for adoptive cancer immunotherapy. Genetic modification can further enhance NK effector cell activity or activation sensitization. Here, we evaluated the effect of the genetic deletion of ubiquitin ligase Casitas B-lineage lymphoma pro-oncogene-b (CBLB), a negative regulator of lymphocyte activity, on placental CD34+ cell-derived NK (PNK) cell cytotoxicity against tumor cells.

METHODS

Using CRISPR/Cas9 technology, CBLB was knocked out in placenta-derived CD34+ hematopoietic stem cells, followed by differentiation into PNK cells. Cell expansion, phenotype and cytotoxicity against tumor cells were characterized in vitro. The antitumor efficacy of CBLB knockout (KO) PNK cells was tested in an acute myeloid leukemia (HL-60) tumor model in NOD-scid IL2R gammanull (NSG) mice. PNK cell persistence, biodistribution, proliferation, phenotype and antitumor activity were evaluated.

RESULTS

94% of CBLB KO efficacy was achieved using CRISPR/Cas9 gene editing technology. CBLB KO placental CD34+ cells differentiated into PNK cells with high cell yield and >90% purity determined by CD56+ CD3- cell identity. Ablation of CBLB did not impact cell proliferation, NK cell differentiation or phenotypical characteristics of PNK cells. When compared with the unmodified PNK control, CBLB KO PNK cells exhibited higher cytotoxicity against a range of liquid and solid tumor cell lines in vitro. On infusion into busulfan-conditioned NSG mice, CBLB KO PNK cells showed in vivo proliferation and maturation as evidenced by increased expression of CD16, killer Ig-like receptors and NKG2A over 3 weeks. Additionally, CBLB KO PNK cells showed greater antitumor activity in a disseminated HL60-luciferase mouse model compared with unmodified PNK cells.

CONCLUSION

CBLB ablation increased PNK cell effector function and proliferative capacity compared with non-modified PNK cells. These data suggest that targeting CBLB may offer therapeutic advantages via enhancing antitumor activities of NK cell therapies.

Abstract 2218: High affinity and cleavage resistant CD16 enhances Trastuzumab mediated killing of gastric cancer targets by human placental CD34+-derived natural killer cells

Introduction: When targeting tumors with monoclonal antibodies, natural killer (NK) cells are key effectors of antibody dependent cellular cytotoxicity (ADCC) following recognition of antibody Fc by CD16. Celularity has developed a novel proprietary technology platform that enables production of an allogeneic, off-the-shelf, placental CD34+-derived NK cell therapy for the treatment of hematologic and solid tumor malignancies. Here we report the genetic modification of CD16 in NK cells for high binding affinity to IgG and resistance to protease cleavage, together with functional evaluation of anti-tumor ADCC activity against epidermal growth factor receptor 2 (HER2) positive gastric cancer cells in combination with Trastuzumab (anti-Her2).

Methods: Human placental CD34+ cells were transduced with lentivirus expressing a high binding affinity (158Val) and protease resistant (197Pro) CD16 variant (CD16VP) and cultured for 35 days in the presence of cytokines, including thrombopoietin, SCF, Flt3 ligand, IL-7, IL-15 and IL-2, to generate CD16VP cells. The tumorigenic activity of CD16VP cells against HER2-positive gastric cancer cell lines NCI-N87 and OE19 was assessed in combination with Trastuzumab. ADCC activity was measured by real-time xCELLigence, and cytokine secretion by Luminex. The kinase inhibitors PD98059 (MEK/ERK), SB203580 (p38 MAPK), SP600125 (JNK), and Wortmannin (PI3K) were used to study the molecular mechanisms underlying cytotoxicity of CD16VP cells against gastric cancer.

Results and conclusion: High transduction efficiency was achieved in multiple placental CD34+ donors with an average of 64.6 ± 10.3% (n=8) CD16 expression on NK cells compared to 12.1 ± 3.3% (n=8) on non-transduced cells. These cells expanded [7095 ± 2998-fold (n=8)] and differentiated into NK cells with >90% purity (CD56+CD3-). While treatment of PMA/ionomycin for 4 hours resulted in >89% CD16 cleavage on non-transduced cells, <11% cleavage was observed on CD16VP cells, demonstrating shedding resistance. CD16VP cells in the presence of Trastuzumab compared to IgG control, showed enhanced lysis of NCI-N87 and OE19 targets (97 ± 7% and 95 ± 2% vs. 55 ± 19% and 42 ± 14% respectively, p<0.01), secreted higher levels of GM-CSF, IFN-γ, and TNF-α, and demonstrated increased degranulation against OE19. The ADCC mediated cytotoxicity and degranulation were PI3K and JNK pathway-dependent as Wortmannin decreased ADCC by 82.2 ± 17.7% and degranulation by 43.9 ± 1.9%, and SP600125 decreased degranulation by 72.3 ± 1.2%. Our results demonstrate that CD16VP cells have enhanced Trastuzumab-mediated ADCC activity against gastric cancer tumor cell lines with resistance to CD16 cleavage. Development of CD16VP cells provides a combination therapeutic option by harnessing the anti-tumor activities of both targeted biologics and innate cytotoxicity of NK cells.

Citation Format: Irene Raitman, Salvatore Rotondo, Tanel Mahlakõiv, Xuan Guo, Andrea DiFiglia, Hemlata Rana, Qian Ye, Srinivas Somanchi, William van der Touw, Lin Kang, Robert Hariri, Xiaokui Zhang. High affinity and cleavage resistant CD16 enhances Trastuzumab mediated killing of gastric cancer targets by human placental CD34+-derived natural killer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2218.

Abstract 4482: Monitoring T cell reactivity to allogeneic placental cell products using multiple lymphocyte reaction and TCR sequencing approaches

Introduction: Allogeneic stem cell-derived therapies offer patients a readily accessible source of off-the-shelf product. However, allogeneic cells may be recognized by the recipient's immune system thus negatively affecting persistence and efficacy. Among people, allelic differences in human leukocyte antigen (HLA) complex genes are the major source of alloantigen which can elicit immunity. While there are established assays for measuring alloantibodies, monitoring T cell alloreactivity is more challenging. Unique clonal populations vary between individuals and functional assays are difficult to scale and standardize if alloreactive populations are rare/infrequent. Here, we evaluate how alloreactive T cells from patients may be identified using multiple lymphocyte reaction (MLR). Next generation sequencing of the TCR locus permits the subsequent identification and monitoring of allogeneic T cell clones in a patient over time.

Methods: Placental leukocytes depleted of CD34 cells or peripheral blood mononuclear cells (PBMC) were enriched for monocytes using magnetic-bead isolation followed by dendritic cell (DC) maturation in the presence of GM-CSF and IL-4 for 5 days. DC were activated with lipopolysaccharide for 16 hours then cultured in the presence of CD3+ T cells isolated from healthy 3rd party PBMC for 5 days in the presence of IL-2. Proliferating alloantigen-specific T cells were observed by flow cytometry. TCR locus sequencing was performed on DNA libraries generated from unstimulated and post-MLR cultures using the Illumina platform.

Results: In contrast to monocyte derived DCs from PBMC, monocyte derived DCs from placenta required higher levels of cytokine and lipopolysaccharide stimulation to achieve similar level of maturation. Co-culture of placental-derived DCs with unrelated T cells over 5 days resulted in the outgrowth of T cell colonies visible by brightfield microscopy. Flow cytometry confirmed clonal expansion of CD4 and CD8 T cell populations based upon the expression of Ki-67, CD25, and CD69 on cells with a higher forward scatter. To assess feasibility of performing TCR sequencing in unstimulated and post-MLR T cells, one T cell responder was evaluated in response to 3 different DC donors. For each DC donor, a single T cell clone representing 0.35% of the starting repertoire expanded to become the dominant clone at 44%, 61%, and 66% following MLR with the next most frequent clones represented 4%, 3%, and 2% among total T cells, respectively. Our data demonstrate the feasibility of identifying alloreactive T cell clones for translational research monitoring in patients. This approach could inform correlations with cell persistence and help optimize allogeneic cell delivery and dosage strategies in the context of disease state and lymphodepletion.

Citation Format: Bhavani Stout, Tanel Mahlakoiv, Robert Hariri, Xiaokui Zhang, William van der Touw. Monitoring T cell reactivity to allogeneic placental cell products using multiple lymphocyte reaction and TCR sequencing approaches [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4482.

Abstract CT108: A Phase I study of PNK-007, allogeneic, off the shelf NK cell, post autologous transplant in multiple myeloma (NCT02955550)

Background: PNK-007 is an allogeneic, off the shelf cell therapy enriched for CD56+/CD3- NK cells expanded from placental CD34+ cells. PNK-007 exhibit cytotoxicity against various cancer cell types, including multiple myeloma (MM), and secrete cytokines during co-culture with cancer cells. This is a Phase I study of single infusion PNK-007 after autologous stem cell transplant (ASCT) in MM.

Methods: Placental CD34+ cells were cultivated in the presence of cytokines for 35 days to generate PNK-007 under cGMP standards followed by release testing. HLA matching and KIR mismatching were not used. Four treatment arms were evaluated on eligible patients (pts) following ASCT: 10 million (M) cells/kg Day (D) 14 with or without rhIL-2, 30M cells/kg D14 with rhIL-2 or 30M cells/kg D7 with rhIL-2. rhIL-2 was administered subcutaneously at 6M units every other day for up to 6 doses to facilitate PNK-007 expansion. Pts received variable pre-ASCT induction therapy. Maintenance therapy was permitted after the Day 90-100 visit (D90). Enrollment is complete, and all pts have completed the D90 visit as of the cutoff date Oct 26, 2018.

Results: 15 pts who received PNK-007 (12 of whom received rhIL-2) were evaluated for clinical response at D90. Pts aged 44-69 yrs included 12 newly diagnosed (ND)MM and 3 relapsed/refractory (RR)MM. The 3 RRMM received 1, 2 or 5 prior lines of therapy, with 2 pts having previous ASCT. All pts had been exposed to IMiDs and PIs. No dose-limiting toxicity, GvHD, graft failure or graft rejection were observed. No serious adverse events (AEs) were attributable to PNK-007 and the reported AEs were consistent with AEs related to ASCT. Based on physician assessed responses by International Myeloma Working Group pre-ASCT, 10/15 pts achieved VGPR or better (1 CR and 9 VGPR), and by D90, 12/15 pts achieved VGPR or better (5 CR or sCR and 7 VGPR). Using a validated Euro-flow minimal residual disease (MRD) assay by bone marrow aspirate (BMA), pre-ASCT, 4/15 pts were MRD negative (MRD-), and by D90, 10/15 pts were MRD-. At one-year post-ASCT, 4/6 pts were MRD-, with 1 converting to MRD-, 1 inadequate sample, and 1 remaining MRD+. PNK-007 did not interfere with immune reconstitution kinetics. Administration of rhIL-2 coincided with a transient increase in circulating regulatory T cell levels. Host NK cells reached a maximum level between 21-28 days post-ASCT followed by contraction independent of rhIL-2 administration.

Conclusion: PNK-007 is the first fully allogeneic, off the shelf CD34+ derived NK cell product in MM clinical trials. A single infusion of PNK-007 up to 30M cells/kg with and without rhIL-2 was well tolerated in the post-ASCT setting. We established the feasibility of infusing PNK-007 as early as 7 days post-ASCT without negative impact on blood count recovery. Attainment of BMA MRD- status was observed in 10/15 pts at D90. These clinical data are encouraging and warrant further evaluation.

Citation Format: Sarah A. Holstein, Sarah A. Cooley, Parameswaran Hari, Sundar Jagannath, Catherine R. Balint, William van der Touw, Michele L. Donato, Philip L. McCarthy, Paul K. Wallace, Xiaokui Zhang, Robert J. Hariri, Mohamad A. Hussein, Ravi Vij. A Phase I study of PNK-007, allogeneic, off the shelf NK cell, post autologous transplant in multiple myeloma (NCT02955550) [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 CT108.

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.

Blocking immunoinhibitory receptor LILRB2 reprograms tumor-associated myeloid cells and promotes antitumor immunity

Tumor-associated myeloid cells maintain immunosuppressive microenvironments within tumors. Identification of myeloid-specific receptors to modulate tumor-associated macrophage and myeloid-derived suppressor cell (MDSC) functions remains challenging. The leukocyte immunoglobulin-like receptor B (LILRB) family members are negative regulators of myeloid cell activation. We investigated how LILRB targeting could modulate tumor-associated myeloid cell function. LILRB2 antagonism inhibited receptor-mediated activation of SHP1/2 and enhanced proinflammatory responses. LILRB2 antagonism also inhibited AKT and STAT6 activation in the presence of M-CSF and IL-4. Transcriptome analysis revealed that LILRB2 antagonism altered genes involved in cell cytoskeleton remodeling, lipid/cholesterol metabolism, and endosomal sorting pathways, as well as changed differentiation gene networks associated with inflammatory myeloid cells as opposed to their alternatively activated phenotype. LILRB2 blockade effectively suppressed granulocytic MDSC and Treg infiltration and significantly promoted in vivo antitumor effects of T cell immune checkpoint inhibitors. Furthermore, LILRB2 blockade polarized tumor-infiltrating myeloid cells from non-small cell lung carcinoma tumor tissues toward an inflammatory phenotype. Our studies suggest that LILRB2 can potentially act as a myeloid immune checkpoint by reprogramming tumor-associated myeloid cells and provoking antitumor immunity.

Glatiramer Acetate Enhances Myeloid-Derived Suppressor Cell Function via Recognition of Paired Ig-like Receptor B

Glatiramer acetate (GA; Copaxone) is a copolymer therapeutic that is approved by the Food and Drug Administration for the relapsing-remitting form of multiple sclerosis. Despite an unclear mechanism of action, studies have shown that GA promotes protective Th2 immunity and stimulates release of cytokines that suppress autoimmunity. In this study, we demonstrate that GA interacts with murine paired Ig-like receptor B (PIR-B) on myeloid-derived suppressor cells and suppresses the STAT1/NF-κB pathways while promoting IL-10/TGF-β cytokine release. In inflammatory bowel disease models, GA enhanced myeloid-derived suppressor cell-dependent CD4⁺ regulatory T cell generation while reducing proinflammatory cytokine secretion. Human monocyte-derived macrophages responded to GA by reducing TNF-α production and promoting CD163 expression typical of alternative maturation despite the presence of GM-CSF. Furthermore, GA competitively interacts with leukocyte Ig-like receptors B (LILRBs), the human orthologs of PIR-B. Because GA limited proinflammatory activation of myeloid cells, therapeutics that target LILRBs represent novel treatment modalities for autoimmune indications.

LILRB receptor-mediated regulation of myeloid cell maturation and function

The leukocyte immunoglobulin-like receptor (LILR) family comprises a set of paired immunomodulatory receptors expressed among human myeloid and lymphocyte cell populations. While six members of LILR subfamily A (LILRA) associate with membrane adaptors to signal via immunoreceptor tyrosine-based activating motifs (ITAM), LILR subfamily B (LILRB) members signal via multiple cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIM). Ligand specificity of some LILR family members has been studied in detail, but new perspective into the immunoregulatory aspects of this receptor family in human myeloid cells has been limited. LILRB receptors and the murine ortholog, paired immunoglobulin-like receptor B (PIRB), have been shown to negatively regulate maturation pathways in myeloid cells including mast cells, neutrophils, dendritic cells, as well as B cells. Our laboratory further demonstrated in mouse models that PIRB regulated functional development of myeloid-derived suppressor cell and the formation of a tumor-permissive microenvironment. Based on observations from the literature and our own studies, our laboratory is focusing on how LILRs modulate immune homeostasis of human myeloid cells and how these pathways may be targeted in disease states. Integrity of this pathway in tumor microenvironments, for example, permits a myeloid phenotype that suppresses antitumor adaptive immunity. This review presents the evidence supporting a role of LILRs as myeloid cell regulators and ongoing efforts to understand the functional immunology surrounding this family.

Complement regulation of T-cell alloimmunity

Complement proteins are generated both by the liver (systemic compartment) and by peripheral tissue-resident cells and migratory immune cells (local compartment). The immune cell-derived, alternative pathway complement components activate spontaneously, yielding local, but not systemic, production of C3a and C5a. These anaphylatoxins bind to their respective G-protein-coupled receptors, the C3a receptor and the C5a receptor, expressed on T cells and antigen-presenting cells, leading to their reciprocal activation and driving T-cell differentiation, expansion, and survival. Complement deficiency or blockade attenuates T-cell-mediated autoimmunity and delays allograft rejection in mice. Increasing complement activation, achieved by genetic removal of the complement regulatory protein decay accelerating factor, enhances murine T-cell immunity and accelerates allograft rejection. Signaling through the C3a receptor and the C5a receptor reduces suppressive activity of natural regulatory T cells and the generation and stability of induced regulatory T cells. The concepts, initially generated in mice, recently were confirmed in human immune cells, supporting the need for testing of complement targeting therapies in organ transplants patients.

Cutting edge: Receptors for C3a and C5a modulate stability of alloantigen-reactive induced regulatory T cells

CD4(+)Foxp3(+) regulatory T cells (Treg) are critical regulators of immune homeostasis and self-tolerance. Whereas thymic-derived or natural Treg stably express Foxp3, adaptive or induced Treg (iTreg) generated from peripheral CD4 T cells are susceptible to inflammation-induced reversion to pathogenic effector T cells. Building upon our previous observations that T cell-expressed receptors for C3a (C3aR) and C5a (C5aR) drive Th1 maturation, we tested the impact of C3aR/C5aR signaling on induction and stability of alloreactive iTreg. We observed that genetic deficiency or pharmacological blockade of C3aR/C5aR signaling augments murine and human iTreg generation, stabilizes Foxp3 expression, resists iTreg conversion to IFN-γ/TNF-α-producing efffector T cells, and, as a consequence, limits the clinical expression of graft-versus-host disease. Taken together, the findings highlight the expansive role of complement as a crucial modulator of T cell alloimmunity and demonstrate proof-of-concept that targeting C3a/C3aR and C5a/C5aR interactions could facilitate iTreg-mediated tolerance to alloantigens in humans.

Signaling through C5a receptor and C3a receptor diminishes function of murine natural regulatory T cells

Blockade of C3aR/C5aR signaling in nT reg cells augments in vitro and in vivo suppression, abrogates autoimmune colitis, and prolongs allogeneic skin graft survival.

Thymus-derived (natural) CD4⁺ FoxP3⁺ regulatory T cells (nT reg cells) are required for immune homeostasis and self-tolerance, but must be stringently controlled to permit expansion of protective immunity. Previous findings linking signals transmitted through T cell–expressed C5a receptor (C5aR) and C3a receptor (C3aR) to activation, differentiation, and expansion of conventional CD4⁺CD25⁻ T cells (T conv cells), raised the possibility that C3aR/C5aR signaling on nT reg cells could physiologically modulate nT reg cell function and thereby further impact the induced strength of T cell immune responses. In this study, we demonstrate that nT reg cells express C3aR and C5aR, and that signaling through these receptors inhibits nT reg cell function. Genetic and pharmacological blockade of C3aR/C5aR signal transduction in nT reg cells augments in vitro and in vivo suppression, abrogates autoimmune colitis, and prolongs allogeneic skin graft survival. Mechanisms involve C3a/C5a-induced phosphorylation of AKT and, as a consequence, phosphorylation of the transcription factor Foxo1, which results in lowered nT reg cell Foxp3 expression. The documentation that C3a/C3aR and C5a/C5aR modulate nT reg cell function via controlling Foxp3 expression suggests targeting this pathway could be exploited to manipulate pathogenic or protective T cell responses.

Complement regulation of T cell immunity

Results of studies published since 2002 reveal that T cells and antigen-presenting cells (APCs) produce complement proteins. The immune cell-derived, alternative pathway complement components activate spontaneously, yielding local, but not systemic, production of C3a and C5a. These anaphylatoxins bind to their respective G-protein-coupled receptors, C3aR and C5aR, expressed on both partners. The resultant complement-induced T cell activation and APC activation drive T cell differentiation, expansion and survival. Complement deficiency or blockade attenuates T cell-mediated autoimmunity and delays allograft rejection in mice. Increasing complement activation, achieved by genetic removal of the complement regulatory protein decay-accelerating factor, enhances murine T cell immunity and accelerates allograft rejection. The findings support the need for design and testing of complement inhibitors in humans.

Epigenetic regulation of Foxp3 expression in regulatory T cells by DNA methylation

Foxp3, a winged-helix family transcription factor, serves as the master switch for CD4(+) regulatory T cells (Treg). We identified a unique and evolutionarily conserved CpG-rich island of the Foxp3 nonintronic upstream enhancer and discovered that a specific site within it was unmethylated in natural Treg (nTreg) but heavily methylated in naive CD4(+) T cells, activated CD4(+) T cells, and peripheral TGFbeta-induced Treg in which it was bound by DNMT1, DNMT3b, MeCP2, and MBD2. Demethylation of this CpG site using the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (Aza) induced acetylation of histone 3, interaction with TIEG1 and Sp1, and resulted in strong and stable induction of Foxp3. Conversely, IL-6 resulted in methylation of this site and repression of Foxp3 expression. Aza plus TGFbeta-induced Treg resembled nTreg, expressing similar receptors, cytokines, and stable suppressive activity. Strong Foxp3 expression and suppressor activity could be induced in a variety of T cells, including human CD4(+)CD25(-) T cells. Epigenetic regulation of Foxp3 can be predictably controlled with DNMT inhibitors to generate functional, stable, and specific Treg.