Enhancement Of Antibody-dependent Cellular Cytotoxicity Research Articles

Safety and activity of lenalidomide in combination with obinutuzumab in patients with relapsed indolent non-Hodgkin lymphoma: a single group, open-label, phase 1/2 trial

Rituximab and lenalidomide is a preferred option for relapsed indolent B cell non-Hodgkin lymphoma. Obinutuzumab may be a superior combination partner with lenalidomide given enhanced antibody dependent cellular cytotoxicity and phagocytosis compared to rituximab. Our aim was to determine the recommended phase 2 dose, safety, and activity of lenalidomide in combination with fixed dose of obinutuzumab in relapsed and refractory indolent B cell non-Hodgkin lymphoma. In this single-arm, open-label, phase 1/2 trial, we enrolled patients with relapsed or refractory WHO Grade 1-3A follicular lymphoma, marginal zone lymphoma and small lymphocytic lymphoma and adequate performance status (ECOG 0-2) at the MD Anderson Cancer Center. We excluded patients with evidence of ongoing transformation to aggressive lymphoma. During phase 1, 1000mg intravenous obinutuzumab was administered with three predefined levels of oral lenalidomide in a 3+3 dose escalation design to establish lenalidomide 20mg as the recommended phase 2 dose. During phase 2, patients received induction therapy with six 28-day cycles of lenalidomide 20mg with intravenous obinutuzumab 1000mg. In accordance with our prior experience with lenalidomide plus rituximab, patients who were responding to the combination could receive up to 6 additional cycles (up to 12 cycles in total) of combination therapy. Dosing of obinutuzumab was continued in all responding patients after cycle 6 every 2 months for a total of 30 months from the start of therapy. The decision of number of cycles of combination therapy beyond 6 was at discretion of the investigator and was included to allow individualisation of therapy to maximise response while minimising exposure. The co-primary objectives were to evaluate the safety and overall response, defined as the proportion of patients who achieved a complete or partial response in relapsed and refractory indolent non-Hodgkin lymphoma at the end of induction therapy, according to Cheson and colleagues (2007 criteria). The secondary endpoints were complete response after induction therapy and time to event endpoints including time to progression, progression free survival, and overall survival. Analyses were intent to treat in the efficacy cohort and per-treated in the safety population in all patients who received at least one dose of either investigational agent. This trial is registered with ClinicalTrials.gov, NCT01995669. Between June 03, 2014, and 07 March 2019, we completed planned enrolment, and 66 patients started therapy including 9 patients in phase 1 and 57 patients in phase 2. All patients were evaluated for safety and the 60 patients treated at the recommended phase 2 dose of lenalidomide 20mg were evaluable for activity. Grade 3-4 haematological toxicities included neutropenia 21% (14/66) and thrombocytopenia 11% (7/66) with no cases of febrile neutropenia. Grade 3-4 non-haematological toxicities included lung infection 8% (5/66), fatigue 8% (5/66) and rash 6% (4/66). By Cheson 2007 criteria, 90% (54/60, 95% CI: 79-96) achieved an overall response at the end of induction meeting the prespecified activity endpoint. Complete responses were seen in 33% (20/60, 95% CI: 22-47) at the end of induction. Median progression free survival, time to progression and overall survival have not been reached after median follow-up of 41.7 months. Estimated 4-year progression free survival rates were 55% (95% CI: 42-73), time to progression of 56% (95% CI: 43-74) and overall survival of 84% (95% CI: 74-95). Our findings suggest that oral lenalidomide with obinutuzumab is safe and highly active in patients with relapsed and refractory indolent B cell non-Hodgkin lymphoma and is associated with prolonged remission duration. The study is limited by the lack of a control arm leading to cross-trial comparisons to evaluate activity. Future randomised trials comparing this regime to rituximab and lenalidomide are warranted. Genentech and an MD Anderson Core grant.

CD19 expression in diffuse large B-cell lymphoma (DLBCL) patient biopsies after treatment with tafasitamab.

e19050 Background: Tafasitamab (tafa) is a CD19-targeting immunotherapy that induces enhanced antibody dependent cellular cytotoxicity and phagocytosis. Tafa received accelerated FDA approval in 2020 for treating relapsed or refractory DLBCL in combination with lenalidomide in patients ineligible for autologous stem cell transplant, based on results from L-MIND, a multicenter, open-label, single-arm, phase 2 trial. FirmMIND (NCT05429268) is an ongoing identical study, further evaluating efficacy and safety of tafa in this setting. Several other CD19 targeting agents are available; however, CD19 antigen loss following treatment with chimeric antigen receptor T-cell therapy targeting CD19 (CART19) has raised concerns over CD19-targeted therapy sequencing. Loss of CD19 has not been observed to date in tafa clinical trials or practice. Methods: To evaluate CD19 expression at screening and after disease progression in firmMIND, we developed an immunohistochemistry (IHC) assay using a mAb that binds to an intracellular epitope of CD19 clone LE-CD19. To validate that CD19 expression is detectable after tafa treatment, we treated cultured SU-DHL-4 or Jurkat cells with tafa at a saturating concentration for 24 hours. After washing out unbound tafa, cells were harvested at specific timepoints. Resulting cell line blocks were assessed for CD19 expression by IHC. We also monitored CD19 trafficking in response to fluorescently labeled tafa by confocal microscopy. Results: By IHC, CD19 expression was comparable between treatment conditions, suggesting the assay can effectively measure CD19 expression in lymphoma biopsy samples post-tafa. Confocal microscopy showed a fraction of tafa-bound CD19 internalized and colocalized with a CD19 intracellular pool labeled with anti-CD19 mAb clone EPR5906; this mAb also detected CD19 that remained localized on the cell surface. The data demonstrated that CD19 persists on tumor cells after tafa treatment at levels that could be bound by other CD19-targeting therapies. As of the January 25, 2024 data cutoff, we received 6 end-of-treatment (EOT) samples from patients in firmMIND. Biopsies were collected 14-26 days after the last tafa dose; 5 of 6 samples were biopsies from lymph nodes or liver and showed ≥80% of tumor cells staining CD19+ on membranes with 3+ intensity by IHC, except 1 that was collected only 6 days after last dose and showed 50% positivity. The sixth biopsy (extranodal subcutaneous lesion) showed no CD19 expression at baseline or EOT. Conclusions: Patient biopsy analysis and preclinical data suggest that following tafa treatment, CD19 antigen is preserved on the surface of tumor cells after short and transient internalization and could be targeted by other CD19 agents, such as CART therapy. This conclusion is supported by sequential treatment with tafa followed by CART in vivo (Sakemura, 2024). Analyses are ongoing to confirm these findings.

Engineering Superaffinity Antibody Dependent Cellular Cytotoxcity Receptors into iPSC-Derived NK Cells As Next-Generation Immunotherapies for Cancer

Engineered immune cells have provided an important new approach to treating cancer. Most of the progress so far has focused on autologous CAR-T cell therapy, although this approach has been met with several limitations including high-cost and complexity of manufacturing, donor-to-donor variability, and severe toxicities in some patients. Allogenic natural killer (NK) cell therapies have also been shown to mount potent responses against hematologic malignancies but are less likely to cause high-grade toxicities and can be mass produced for off-the-shelf usage. We have developed an induced pluripotent stem cell (iPSC) derived NK (iNK) platform amenable to engineering multiple features in immune cells to improve efficacy against both solid and liquid tumors. Our previous studies showed that knocking out the CISH gene, which encodes a key regulator of activation, in iNK cells significantly improves their anti-cancer activity, in vivo persistence, metabolic fitness, polyfunctional cytokine production, and resistance to cell exhaustion. In these CISH Knockout (KO) iNK cells, we have screened a library of CAR constructs containing domains from diverse immune cell signaling receptors including NK cell activating receptors, cytokine receptors, and integrins. Our screen identified SLNK12, a CAR signaling domains that performed better than both T cell CARs and previously reported NK cell CARs in the context of CISH KO iNK cells. In this study, we describe the development of iNK cells with enhanced antibody dependent cellular cytotoxicity (ADCC) activity. NK cells normally bind antibodies via their CD16A receptor, which has medium-to-low affinity for the antibody Fc domain and is also typically expressed at a low level in unmodified iNKs. We have constructed a recombinant Fc-receptor that combines a high-affinity Fc-binding domain (to improve antibody binding) with our NK cell optimized SLNK12 CAR signaling domain to enhance ADCC-mediated killing. When co-cultured with multiple NC cell resistant tumor lines such as BT-474 (breast cancer) or FaDu (squamous cell carcinoma), these SuperAffinity ADCC receptor CISH KO iNK cells possess potent anti-cancer activity in combination with several different therapeutic monoclonal antibodies, including anti-EGFR (Cetuximab) and anti-HER2 (Trastuzumab) amongst others (Figure 1). We have assessed efficacy in a variety of different 2D and 3D spheroid cytotoxicity assays, as well as cytokine release and CAR activation assays. In addition, we demonstrate that our SuperAffinity receptor mediates tumor cell killing at lower antibody concentrations than do CD16A variants. Furthermore, introduction of serum IgG inhibits, but does not stop ADCC killing for both our SuperAffinity ADCC receptor and the CD16A receptor. Taken together, our results show that engineering CISH KO iNK cells with NK-optimized CARs for enhanced ADCC improves anti-tumor activity against a variety of solid tumor target lines. Future work will focus on advancing the new cellular therapies into clinical development.

BAT6026, a novel anti-OX40 antibody with enhanced antibody dependent cellular cytotoxicity effect for cancer immunotherapy.

OX40 (CD134), a member of the TNF receptor superfamily, is a widely studied costimulatory immune checkpoint. Several OX40 agonistic antibodies are in the clinical stage for cancer treatment, among which PF-04518600 is the leader and currently in phase II trial. It has been recognized that one potential mode of action for anti-OX40 antibodies is the deletion of intratumoral Tregs. Thus, a novel human anti-OX40 antibody, BAT6026, was generated with enhanced antibody dependent cellular cytotoxicity (ADCC) via fucose deletion to strengthen its Treg depletion activity. This characteristic of BAT6026 differentiates it from other previously reported anti-OX40 antibodies in the field of tumor therapy. The affinity of BT6026 to OX40 was 0.28nM, approximately 8 times stronger than that of PF-04518600. BAT6026 effectively competed for the binding of ligand OX40L to OX40, whereas PF-04518600 only partially competed. Moreover, compared to PF-04518600, BAT6026 activated T cells more effectively when clustered by FcγRs engagement and stimulated SEB-pretreated PBMCs to secrete IL-2 cytokines in vitro. In addition, BAT6026 demonstrated stronger anti-tumor activity than PF-04518600 in an OX40-humanized mouse MC38 tumor model. BAT6026 also showed a significantly synergistic effect on tumor inhibition when combined treatment with PD-1 antibody. Analysis of tumor-infiltrating T cells revealed that BAT6026 treatment significantly reduced Treg cells and increased CD8+ T cells in tumor. Preclinical safety assessment in non-human primates demonstrated a good safety profile for BAT6026. Together these data warrant further development of BAT6026 into clinical trials for patients with cancer.

Preliminary results of a phase 1/2, first-in-human, open-label, dose escalation study of ZL-1211 (anti-Claudin 18.2 mAb) in patients with unresectable or metastatic solid tumors.

2537 Background: ZL-1121 is a humanized immunoglobulin G1 monoclonal antibody targeting Claudin18.2. Site mutations (S239D and I332E) were introduced in the Fc portion of ZL-1211 to enhance antibody dependent cellular cytotoxicity. Herein, we present the preliminary results from the ongoing dose escalation part of the study. Methods: This is a first-in-human, phase 1/2, multicenter, dose escalation/cohort expansion study of ZL-1211 administered intravenously to adult patients with Claudin 18.2-positive advanced solid tumors. A Bayesian optimal interval design with 3+3 run-in was adopted to assess 5 dose levels of ZL-1211 monotherapy (1 to 40 mg/kg biweekly) for phase 1 dose escalation, followed by phase 2 cohort expansion. The primary objectives were to determine the maximum tolerated dose and/or the recommended phase 2 dose, assess the safety/tolerability, and evaluate the preliminary antitumor activities of ZL-1211. Tumor assessments were performed every 8 weeks per RECIST v1.1. Blood samples were collected for pharmacokinetic (PK) analyses. Results: As of Dec 12, 2022, 19 patients (11 pancreatic cancer, 6 gastric cancer, 1 esophageal cancer, and 1 bile duct cancer) had been enrolled in the dose escalation phase to receive ZL-1211 at 1 mg/kg (n = 3), 5 mg/kg (n = 7), 10 mg/kg (n = 4), and 20 mg/kg (n = 5). The median age was 60 years and the majority of the patients (78.9%) received ≥2 lines of prior systemic therapy. No dose limiting toxicities (DLT) had been observed as of the cut-off date. The most common treatment-related adverse events (TRAEs) were gastrointestinal disorders, including nausea (11/19, 57.9%), vomiting (6/19, 31.6%), and abdominal pain (3/19, 15.8%). Other common TRAEs (≥15%) were hypoalbuminaemia (3/19, 15.8%) and infusion-related reactions (3/19, 15.8%). Grade 3 TRAEs occurred in 3 patients, 1 with nausea and vomiting, 1 with platelet count decreased, and 1 with anaemia, leukopenia, platelet count decreased, and weight decreased. No Grade ≥ 4 TRAEs were reported. Two patients experienced serious TRAEs: 1 reporting 2 cases each of grade 3 vomiting and nausea and 1 reporting a grade 3 platelet count decreased and a grade 2 abdominal pain, all of which had recovered. TRAEs led to treatment interruption in 5 patients (26.3%) and treatment withdrawal in 1 patient (5.3%). No TRAEs leading to death were reported. Six of 9 tumor-evaluable patients achieved stable disease as the best overall response. Three patients had tumor regression: 17.1% in a pancreatic cancer patient of the 5 mg/kg cohort; 14.5% in a pancreatic cancer patient and 24.9% in a gastric cancer patient in the 10 mg/kg cohort. Preliminary PK analyses revealed linear PK of ZL-1211 over the dose range tested. Conclusions: ZL-1211 displayed an acceptable safety/tolerability profile to date and demonstrated preliminary antitumor effects. Clinical trial information: NCT05065710 .

Abstract 1528: 6B5, an anti-human B7-H3 therapeutic antibody that enhances antibody-dependent cellular cytotoxicity and inhibits tumor growth in B7-H3-humanized mice

Abstract B7-H3 (CD276) is a type I transmembrane protein belonging to the B7 family of immune-regulatory ligands. Initially reported as a costimulatory signal of human T cells, increasing evidence suggests that it may also have coinhibitory function. TLT-2 has been identified as a potential cognate receptor for B7-H3, but others may exist. Overexpression of B7-H3 protein is found in a variety of human cancers, including lung adenocarcinomas, neuroblastomas, gliomas, and pancreatic tumors—and is associated with poor prognosis and survival. While B7-H3 can promote T cell activation and anti-tumor responses in the context of CD3 stimulation, its coinhibitory function inhibits T and NK cell activity in the tumor microenvironment. We generated 6B5, a fully human B7-H3 monoclonal antibody, from murine B7-H3 knock-out RenMab™ mice, which contain the full human immunoglobulin variable domain. 6B5 is cross-reactive with rodent and cynomolgus monkey B7-H3. It displays higher affinity for tumor cell lines than Enoblituzumab. 6B5 has no staining on normal human tissues. In vitro antibody-dependent cellular cytotoxicity (ADCC) against H520 squamous cell carcinoma cells was potentiated by 6B5 relative to Enoblituzumab and, critically, did not exhibit the hook effect at high dosage. In vivo efficacy of 6B5 in humanized B7-H3 mice bearing murine EL4 lymphomas was comparable to Enoblituzumab. ADCC enhancement in vivo was comparable to afucosylation or five-point mutations. Epitope mapping revealed non-overlapping B7-H3 binding epitopes of 6B5 and Enoblituzumab. Taken together, these data suggest that 6B5 is a promising therapeutic anti-human B7-H3 IgG monoclonal antibody that may find clinical application in a range of cancers, including current refractory types. Citation Format: Yunyun Chen, Jiangmei Li, Yanan Guo, Wenqi Hu, Ting Mao, Li Hui, W. Frank An, Yi Yang, Feng Li. 6B5, an anti-human B7-H3 therapeutic antibody that enhances antibody-dependent cellular cytotoxicity and inhibits tumor growth in B7-H3-humanized mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1528.

Leveraging Natural Killer Cell Innate Immunity against Hematologic Malignancies: From Stem Cell Transplant to Adoptive Transfer and Beyond

Numerous recent advancements in T-cell based immunotherapies have revolutionized the treatment of hematologic malignancies. In the race towards the first approved allogeneic cellular therapy product, there is growing interest in utilizing natural killer (NK) cells as a platform for off-the-shelf cellular therapies due to their scalable manufacturing potential, potent anti-tumor efficacy, and superior safety profile. Allogeneic NK cell therapies are now being actively explored in the setting of hematopoietic stem cell transplantation and adoptive transfer. Increasingly sophisticated gene editing techniques have permitted the engineering of chimeric antigen receptors, ectopic cytokine expression, and tumor recognition signals to improve the overall cytotoxicity of NK cell therapies. Furthermore, the enhancement of antibody-dependent cellular cytotoxicity has been achieved through the use of NK cell engagers and combination regimens with monoclonal antibodies that act synergistically with CD16-expressing NK cells. Finally, a greater understanding of NK cell biology and the mechanisms of resistance have allowed the preclinical development of NK checkpoint blockade and methods to modulate the tumor microenvironment, which have been evaluated in early phase trials. This review will discuss the recent clinical advancements in NK cell therapies in hematologic malignancies as well as promising avenues of future research.

Characterization of a Novel CD4 Mimetic Compound YIR-821 against HIV-1 Clinical Isolates.

Small CD4-mimetic compound (CD4mc), which inhibits the interaction between gp120 with CD4, acts as an entry inhibitor and induces structural changes in the HIV-1 envelope glycoprotein trimer (Env) through its insertion within the Phe43 cavity of gp120. We recently developed YIR-821, a novel CD4mc, that has potent antiviral activity and lower toxicity than the prototype NBD-556. To assess the possibility of clinical application of YIR-821, we tested its antiviral activity using a panel of HIV-1 pseudoviruses from different subtypes. YIR-821 displayed entry inhibitor activity against 53.5% (21/40) of the pseudoviruses tested and enhanced neutralization mediated by coreceptor binding site (CoRBS) antibodies in 50% (16/32) of these. Furthermore, when we assessed the antiviral effects using a panel of pseudoviruses and autologous plasma IgG, enhancement of antibody-mediated neutralization activity was observed for 48% (15/31) of subtype B strains and 51% (28/55) of non-B strains. The direct antiviral activity of YIR-821 as an entry inhibitor was observed in 53% of both subtype B (27/51) and non-B subtype (40/75) pseudoviruses. Enhancement of antibody-dependent cellular cytotoxicity was also observed with YIR-821 for all six selected clinical isolates, as well as for the transmitted/founder (T/F) CH58 virus-infected cells. The sequence diversity in the CD4 binding site as well as other regions, such as the gp120 inner domain layers or gp41, may be involved in the multiple mechanisms related to the sensitive/resistant phenotype of the virus to YIR-821. Our findings may facilitate the clinical application of YIR-821. IMPORTANCE Small CD4-mimetic compound (CD4mc) interacts with the Phe43 cavity and triggers conformational changes, enhancing antibody-mediated neutralization and antibody-dependent cellular cytotoxicity (ADCC). Here, we evaluated the effect of YIR-821, a novel CD4mc, against clinical isolates, including both subtype B and non-B subtype viruses. Our results confirm the desirable properties of YIR-821, which include entry inhibition, enhancement of IgG-neutralization, binding, and ADCC, in addition to low toxicity and long half-life in a rhesus macaque model, that might facilitate the clinical application of this novel CD4mc. Our observation of primary viruses that are resistant to YIR-821 suggests that further development of CD4mcs with different structural properties is required.

460 Enhancement of antibody-dependent cellular cytotoxicity is associated with treatment response to extracorporeal photopheresis in Sézary syndrome

Sézary syndrome (SS) is a rare, leukemic type of cutaneous T-cell lymphoma (CTCL), for which extracorporeal photopheresis (ECP) is a first-line therapy. Reliable biomarkers to objectively monitor the response to ECP in patients with SS are missing. We examined the quantitative and qualitative impact of ECP on natural killer (NK) cell activity in SS patients, and especially their functional ability for antibody-dependent cell-mediated cytotoxicity (ADCC). Further, we addressed the question whether the magnitude of the effect on ADCC can be associated with the anti-cancer efficacy of ECP in SS patients.

Pre-Clinical Efficacy of AB-101, an Allogeneic Cord-Blood Derived Natural Killer (NK) Cell Therapeutic Candidate, in Combination with Anti-CD38 Antibodies in Models of Multiple Myeloma

Introduction: AB-101 is a non-engineered, allogeneic, off-the-shelf, cryopreserved cord blood-derived natural killer (NK)-cell therapy in development as a cancer therapeutic. A highly scaled manufacturing process enables production of 1000s of doses of AB-101 from a single donor cord blood unit (CBU). AB-101 is derived from CBUs selected for KIR-B haplotype and natural high-affinity variant of CD16 (158V/V), which are associated with improved anti-tumor activity and ADCC enhancement, resulting in a highly active NK cell product without the requirement for additional engineering. We are developing AB-101 for combination with monoclonal antibodies (mAbs) to enhance antibody dependent cellular cytotoxicity (ADCC) in patients, initially in an ongoing Phase I clinical trial for NHL. To further develop AB-101 as an ADCC enhancer, we assessed anti-tumor activity in combination with CD38 mAb, against multiple myeloma (MM) cell lines. CD38 is a transmembrane glycoprotein that is uniformly and highly upregulated on MM cells. Anti-CD38 mAbs exert anti-tumor activity against MM through ADCC and other mechanisms. NK cells play a key role in ADCC responses through CD16 receptor signaling. However, the majority of NK cells express CD38 and are depleted by therapeutic CD38 mAbs which could limit their therapeutic efficacy. Combining NK cell therapies with anti-CD38 mAbs, thus necessitates CD38 knockout to prevent fratricide. AB-101 has a naturally low percent and intensity of CD38 expression. Here we present data demonstrating that AB-101 are resistant to anti-CD38 mAb-induced fratricide and can elicit significant ADCC against MM cell lines both in vitro and in vivo. Since anti-CD38 mAbs are combined with glucocorticoids in the clinic, we assessed the impact of dexamethasone and methylprednisolone on ADCC by AB-101. Here we report robust ADCC following treatment of AB-101 with glucocorticoids. Methods: AB-101 was screened for CD38 expression and incubated with anti-CD38 mAb - daratumumab or hIgG1 control (300 - 0.41 µg/ml) for 4 hours to assess fratricide. In vitro ADCC assays were performed at various effector to target ratios against control (Daudi and K562) and MM cell lines (NCI-H929, RPMI 8226, MM.1S and MM.1R) using 2 µg/ml of daratumumab or hIgG1. To study the effect of glucocorticoids, AB-101 was cultured in various concentrations of dexamethasone and methylprednisolone for 48 hours in the presence of 50 or 500 IU/ml of IL-2, prior to ADCC assay. In vivo efficacy of AB-101 in combination with daratumumab was assessed in the intraperitoneal (IP) MM.1S-Luc xenograft model in NSG mice (Figure 1A). Daratumumab and AB-101 were administered by IP injection. Tumor burden was assessed by bioluminescent imaging (BLI). Results: AB-101 was over 98% CD56+/CD3- with 87% CD56+/CD16+ population. Only 22% of GMP drug product were CD38+ with low intensity of expression compared to peripheral blood NK cells (~88%). In the presence of daratumumab AB-101 viability was unaltered compared to hIgG1 control demonstrating resistance to fratricide. Daratumumab enhanced ADCC potential of AB-101 against MM cell lines and Daudi in in vitro. ADCC against MM lines and Daudi did not decrease on exposure to glucocorticoids compared to no treatment group. In vivo anti-tumor efficacy, as evidenced by reduction in BLI signal, was observed in the MM.1S model in AB-101 + daratumumab groups compared to daratumumab and AB-101 alone (Figure 1B). AB-101 + daratumumab (1 and 3mpk) led to 98 and 99% tumor growth inhibition (TGI), respectively, relative to no treatment. Daratumumab monotherapy at 1 and 3mpk showed 21% and 87% TGI respectively, and AB-101 showed 16% TGI relative to no treatment. Conclusions: AB-101 has high and consistent expression of CD16 and low CD38 expression and is resistant to daratumumab induced fratricide and hence can be combined with daratumumab without additional engineering such as CD38 knockout. Daratumumab is combined in the clinic with glucocorticoids, immunomodulatory drugs (IMiDs) and proteosome inhibitors (PI). While IMiDs and PIs are reported to enhance NK cell function, glucocorticoids have been shown to diminish NK cell cytotoxicity. Data presented here suggests that ADCC potential of AB-101 is not negatively impacted by glucocorticoids. Taken together, the in vitro and in vivo data supports further clinical development of AB-101 in combination with daratumumab to treat MM patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Epigallocatechin-3-Gallate as a Novel Vaccine Adjuvant.

Vaccine adjuvants from natural resources have been utilized for enhancing vaccine efficacy against infectious diseases. This study examined the potential use of catechins, polyphenolic materials derived from green tea, as adjuvants for subunit and inactivated vaccines. Previously, catechins have been documented to have irreversible virucidal function, with the possible applicability in the inactivated viral vaccine platform. In a mouse model, the coadministration of epigallocatechin-3-gallate (EGCG) with influenza hemagglutinin (HA) antigens induced high levels of neutralizing antibodies, comparable to that induced by alum, providing complete protection against the lethal challenge. Adjuvant effects were observed for all types of HA antigens, including recombinant full-length HA and HA1 globular domain, and egg-derived inactivated split influenza vaccines. The combination of alum and EGCG further increased neutralizing (NT) antibody titers with the corresponding hemagglutination inhibition (HI) titers, demonstrating a dose-sparing effect. Remarkably, EGCG induced immunoglobulin isotype switching from IgG1 to IgG2a (approximately >64–700 fold increase), exerting a more balanced TH1/TH2 response compared to alum. The upregulation of IgG2a correlated with significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) function (approximately 14 fold increase), providing a potent effector-mediated protection in addition to NT and HI. As the first report on a novel class of vaccine adjuvants with built-in virucidal activities, the results of this study will help improve the efficacy and safety of vaccines for pandemic preparedness.

The Combination of Umbralisib Plus Ublituximab Is Active in Patients with Relapsed or Refractory Marginal Zone Lymphoma (MZL): Results from the Phase 2 Global Unity-NHL Trial

The Combination of Umbralisib Plus Ublituximab Is Active in Patients with Relapsed or Refractory Marginal Zone Lymphoma (MZL): Results from the Phase 2 Global Unity-NHL Trial

268 Enhancement of antibody-dependent cellular cytotoxicity is associated with treatment response to extracorporeal photopheresis in Sézary syndrome

Importance: Sézary syndrome (SS) is a rare, leukemic type of cutaneous T-cell lymphoma (CTCL), which can be successfully controlled with extracorporeal photopheresis (ECP). Reliable biomarkers to objectively monitor the response to ECP in patients with SS are missing. Objective: We examined the quantitative and qualitative impact of ECP on natural killer (NK) cell activity in SS patients, and especially their functional ability for antibody-dependent cell-mediated cytotoxicity (ADCC). Further, we address the question if the magnitude of the effect can be associated with the treatment response to ECP in SS patients. Materials and Methods: We collected blood samples before starting therapy and after an average of 9 months of uninterrupted ECP treatment from a case-series of 13 SS patients (8 women, 5 men). This is a single-centre study. All patients were diagnosed according to EORTC-WHO criteria and gave written informed consent to the use of their material and data for research purposes. Blood from healthy volunteers was obtained anonymously from a blood bank. Number of NK cells by flow cytometry, ADCC activity by LDH release assay and flow cytometry, treatment response based on blood tumour staging. Results: NK cell numbers were reduced in SS patients compared to healthy individuals and showed a tendency of recovery after long-term ECP treatment, independent of the response to treatment. Patients with marginal increase (≤1.5 AU-fold) or lack of increase in ADCC activity failed to respond to treatment, while an increase in ADCC efficacy paralleled a positive response to ECP. Conclusions and Relevance: NK-mediated ADCC is selectively enhanced and can serve as a reliable biomarker to objectively monitor response to ECP in patients with SS.

Bio-O2-04 - Enhancement of antibody-dependent cellular cytotoxicity is associated with treatment response to extracorporeal photopheresis in Sézary syndrome

Sézary syndrome (SS) is a rare, leukemic type of cutaneous T-cell lymphoma (CTCL), for which extracorporeal photopheresis (ECP) is a first-line therapy. Reliable biomarkers to objectively monitor the response to ECP in patients with SS are missing. We examined the quantitative and qualitative impact of ECP on natural killer (NK) cell activity in SS patients, and especially their functional ability for antibody-dependent cell-mediated cytotoxicity (ADCC). Further, we addressed the question whether the magnitude of the effect on ADCC can be associated with the anti-cancer efficacy of ECP in SS patients. We assessed numbers of NK cells, ADCC activity, and treatment response based on blood tumor staging in a cohort of 13 SS patients (8 women, 5 men) treated with ECP as a first-line therapy. Blood samples were collected before treatment start and after an average of 9 months of uninterrupted ECP treatment. NK cell numbers were reduced in SS patients compared to healthy individuals and showed a tendency of recovery after long-term ECP treatment, independent of the clinical response to treatment. Patients with marginal increase (≤1.5 AU-fold) or lack of increase in ADCC activity failed to respond clinically to treatment, while patients with an increased ADCC activity showed a reduction in blood tumor burden. NK-mediated ADCC is selectively enhanced and might be a mechanism underlying the effect of ECP while in addition it can possibly serve as a reliable biomarker to objectively monitor response to ECP in patients with SS.

Genetically Engineered Pluripotent Cell-Derived Natural Killer Cell Therapy Provides Enhanced Antibody Dependent Cellular Cytotoxicity Against Hematologic Malignancies and Solid Tumors in Combination with Monoclonal Antibody Therapy

Antibody-dependent cellular cytotoxicity (ADCC) is a key effector mechanism mediated by natural killer (NK) cells that has been shown to significantly contribute to the anti-tumor effect of therapeutic monoclonal antibodies (mAbs) including rituximab (anti-CD20), cetuximab (anti-EGFR) and trastuzumab (anti-ErbB2). ADCC is induced by the crosslinking of the FcγRIIIA (CD16a) receptor expressed on NK cells with cell surface-bound IgG antibodies. Upon NK cell activation, CD16a is proteolytically cleaved from the surface of NK cells, a process that decreases ADCC. There exist two allelic variants of CD16a, with the high-affinity CD16a 158V allele found in about 10% of the population. Additionally, we previously identified a single substitution mutation that renders CD16a resistant to activation-induced cleavage. Engineering of human induced pluripotent stem cells (hiPSCs) with a non-cleavable version of the high-affinity CD16a 158V variant, followed by differentiation of hiPSCs to NK cells, enables us to develop an off-the-shelf NK cell therapy with improved ADCC properties when combined with monoclonal antibody therapy for treatment of both hematologic malignancies and solid tumors. We evaluated cell surface phenotype, as well as the in vitro and in vivo tumor-killing function, of these high affinity, non-cleavable CD16a iNK (hnCD16-iNK) cells alone and in combination with anti-CD20 mAb against multiple B-cell leukemia and lymphoma targets. In contrast to the endogenous expression of CD16a on peripheral blood NK (PB-NK) cells, which is variable depending on the donor, the derivation of NK cells from a clonal hiPSC line engineered to express hnCD16a produced a uniform population of CD16+ NK cells (>95% CD16+ for hnCD16-iNK vs. 40-60% CD16+ PB-NK cells). These hnCD16-iNK cells are phenotypically mature, highly functional in vitro, and exhibit enhanced ADCC when combined with anti-CD20 mAb against multiple lymphoma targets, including Raji, Nalm6 and Jeko-1. Both direct and CD16-mediated activation of hnCD16-iNK cells result in production of the inflammatory cytokines tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). Furthermore, in contrast to PB-NK cells, hnCD16-iNK cells proved to be highly resistant to activation-induced cleavage of CD16 in response to Raji cells coated with anti-CD20 (68±26% cleavage for PB-NK vs. 8.0±4.2% cleavage for hnCD16-iNK cells). To extend these findings to an in vivo model, we treated Raji-lymphoma bearing mice with either anti-CD20 mAb (rituximab) alone or in combination with either PB-NK cells or hnCD16-iNK cells. Combination treatment with hnCD16-iNK cells enhanced the efficacy of anti-CD20 compared to mAb treatment only, and provided improved tumor regression compared to mAb plus PB-NK (p<0.001; tumor burden measured six days after NK cell injection). Additionally, mice that received combination treatment with hnCD16-iNK cells had significantly better survival than mice treated with mAb alone (median survival rate of 39 days for rituximab treatment only group vs. >50 days for combination treatment with hnCD16-iNK). Similar results were seen with the combination of anti-HER2 antibody and hnCD16-iNK cells in an SKOV3 ovarian cancer mouse model. In summary, these data demonstrate that combination therapy hnCD16-iNK cells with monoclonal antibody therapy is highly functional against various tumor cell lines in vitro and in vivo, and justify further investigation into their clinical application to enhance ADCC and the anti-tumor effects of therapeutic mAbs. DisclosuresBjordahl:Fate Therapeutics: Employment, Equity Ownership. Gaidarova:Fate Therapeutics Inc.: Employment, Equity Ownership. Rogers:Fate Therapeutics Inc.: Employment, Equity Ownership. Kaufman:Fate Therapeutics: Consultancy, Research Funding. Valamehr:Fate Therapeutics: Employment, Equity Ownership.

Enhancement of Antibody-Dependent Cellular Cytotoxicity and Phagocytosis in Anti-HIV-1 Human-Bovine Chimeric Broadly Neutralizing Antibodies.

No prophylactic vaccine has provided robust protection against human immunodeficiency virus type 1 (HIV-1). Vaccine-induced broadly neutralizing antibodies (bNAbs) have not been achieved in humans and most animals; however, cows vaccinated with HIV-1 envelope trimers produce bNAbs with unusually long third heavy complementarity-determining regions (CDRH3s). Alongside neutralization, Fc-mediated effector functions, including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADP), may be critical for in vivo bNAb antiviral activity. Here, we aimed to augment the Fc-dependent effector functions of a chimeric human-bovine bNAb, NC-Cow1, which binds the CD4 binding site (CD4bs) and exhibits broader and more potent neutralization than most human CD4bs bNAbs by using an exceptionally long 60-amino acid (aa) CDRH3. The bovine variable region of NC-Cow1 was paired with a human IgG1 Fc region mutated to create the following three variants: G236R/L328R (GRLR) that abrogates Fc-gamma receptor (FcγR) binding, and two variants that enhance binding, namely, G236A/S239D/I332E (GASDIE) and G236A/S239D/A330L/I332E (GASDALIE). Both GASDIE and GASDALIE improved binding to human FcγRIIA and FcγRIIIA, enhanced human natural killer (NK) cell activation, and mediated higher levels of ADCC and ADP activity than the wild-type human IgG1 Fc. GASDALIE mediated higher phagocytic activity than GASDIE. As expected, GRLR eliminated binding to FcγRs and did not mediate ADCC or ADP. We demonstrated that mutations in the human Fc region of bovine chimeric antibodies with ultralong CDRH3s could enhance antibody effector functions while maintaining envelope binding and neutralization. This study will have significant implications in the development of multifunctional anti-HIV antibodies, which may be important to prevent HIV-1 transmission in an antibody-based topical microbicide. IMPORTANCE Despite successful antiviral chemotherapy, human immunodeficiency virus (HIV) is still a lifelong persistent virus, and no vaccine yet prevents HIV transmission. Topical microbicides offer an important alternative method to prevent sexual transmission of HIV-1. With the production of highly potent anti-HIV-1 broadly neutralizing antibodies (bNAbs) and multifunctional antibodies, monoclonal antibodies are now important prophylactic agents. Recently discovered anti-HIV-1 bovine bNAbs (with higher potency and breadth than most human bNAbs) could be novel candidates as potent topical microbicides. Our study is significant as it demonstrates the compatibility of combining bovine-derived neutralization with human-derived antibody-effector functions. This study is a new approach to antibody engineering that strengthens the feasibility of using high-potency bovine variable region bNAbs with augmented Fc function and promotes them as a strong candidate for antibody-mediated therapies.

Enhancement of antibody-dependent cellular cytotoxicity is associated with treatment response to extracorporeal photopheresis in Sézary syndrome

Summary Sézary syndrome (SS) is a rare, leukemic type of cutaneous T-cell lymphoma (CTCL), for which extracorporeal photopheresis (ECP) is a first-line therapy. Reliable biomarkers to objectively monitor the response to ECP in patients with SS are missing. We examined the quantitative and qualitative impact of ECP on natural killer (NK) cell activity in SS patients, and especially their functional ability for antibody-dependent cell-mediated cytotoxicity (ADCC). Further, we addressed the question whether the magnitude of the effect on ADCC can be associated with the anti-cancer efficacy of ECP in SS patients. We assessed numbers of NK cells, ADCC activity, and treatment response based on blood tumor staging in a cohort of 13 SS patients (8 women, 5 men) treated with ECP as a first-line therapy. Blood samples were collected before treatment start and after an average of 9 months of uninterrupted ECP treatment. NK cell numbers were reduced in SS patients compared to healthy individuals and showed a tendency of recovery after long-term ECP treatment, independent of the clinical response to treatment. Patients with marginal increase (≤1.5 AU-fold) or lack of increase in ADCC activity failed to respond clinically to treatment, while patients with an increased ADCC activity showed a reduction in blood tumor burden. NK-mediated ADCC is selectively enhanced and might be a mechanism underlying the effect of ECP while in addition it can possibly serve as a reliable biomarker to objectively monitor response to ECP in patients with SS.

Glycoengineering of AAV-delivered monoclonal antibodies yields increased ADCC activity

The absence of fucose on asparagine-297 of the human immunoglobulin G (IgG) heavy chain has been shown to enhance antibody-dependent cellular cytotoxicity (ADCC) activity by 10- to 100-fold compared to fucosylated antibody. Our lab is studying the use of adeno-associated virus (AAV) as a vector for the delivery of HIV-specific antibodies for therapeutic purposes. Since the antibody is produced by vector-transduced cells in vivo, current techniques of glycoengineering cannot be utilized. In order to achieve similar enhancement of ADCC with AAV-delivered antibodies, short hairpin RNAs (shRNAs) that target fucosyltransferase-8 (FUT8), were designed, tested, and cloned into AAV vectors used to deliver HIV-specific broadly neutralizing antibodies (bNAbs). Antibodies produced by our glycoengineered-AAV (GE-AAV) vectors were analyzed for fucose content and ADCC. GE-AAV constructs were able to achieve over 80% knockdown of FUT8. Results were confirmed by lectin western blot for α1-6 fucose, which revealed almost a complete absence of fucose on GE-AAV-produced antibodies. GE-AAV-produced antibodies revealed >10-fold enhancement of ADCC, while showing identical neutralization and gp140 trimer binding compared to their fucosylated counterparts. ADCC was enhanced 40- to 60-fold when combined with key Fc mutations known to enhance binding to FcγRIIIA. Our findings define a powerful approach for supercharging AAV-delivered anti-HIV antibodies.

Obinutuzumab (GA101) vs. rituximab significantly enhances cell death, antibody-dependent cytotoxicity and improves overall survival against CD20+ primary mediastinal B-cell lymphoma (PMBL) in a xenograft NOD-scid IL2Rgnull (NSG) mouse model: a potential targeted agent in the treatment of PMBL.

Primary mediastinal large B-cell lymphoma (PMBL), a distinct mature B-cell lymphoma, expresses CD20 and has recently been successfully treated with the combination of a type I anti-CD20 monoclonal antibody, rituximab, with multiple combination chemotherapy regimens. Obinutuzumab is a glycoengineered type II anti-CD20 monoclonal antibody (mAb), recognizing a unique CD20 extracellular membrane epitope with enhanced antibody dependent cellular cytotoxicity (ADCC) vs rituximab. We hypothesize that obinutuzumab vs rituximab will significantly enhance in-vitro and in-vivo cytotoxicity against PMBL. PMBL cells were treated with equal dose of obinutuzumab and rituximab for 24 hours (1–100 μg/ml). ADCC were performed with ex-vivo expanded natural killer cells at 10:1 E: T ratio. Mice were xenografted with intravenous injections of luciferase expressing Karpas1106P cells and treated every 7 days for 8 weeks. Tumor burden was monitored by IVIS spectrum system. Compared with rituximab, obinutuzumab significantly inhibited PMBL cell proliferation (p = 0.01), promoted apoptosis (p = 0.05) and enhanced ADCC (p = 0.0002) against PMBL. Similarly, in PMBL xenografted NOD scid gamma mice, obinutuzumab significantly enhanced survival than rituximab when treated with equal doses (p = 0.05). Taken together our results suggest that obinutuzumab significantly enhanced natural killer cytotoxicity, reduced PMBL proliferation and prolonged the overall survival in humanized PMBL xenografted NOD scid gamma mice.

Abstract 2370: Synergistic effect of carboplatin on farletuzumab (FAR) tumor cell killing via downregulation of the humoral immunosuppressive CA125 protein and enhanced antibody dependent cellular cytotoxicity (ADCC)

Abstract Farletuzumab (FAR) is a humanized monoclonal antibody (mAb) that targets folate receptor alpha (FRA), a cell surface protein highly overexpressed on a large number of cancers. Clinical evidence suggests that FAR enhances the anti-tumor effects of carboplatin and taxane in ovarian cancer patients whose tumors express low CA125 levels. In light of the recent evidence that CA125 has a direct effect on suppressing the humoral immune mechanisms [antibody dependent cellular cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC)] of FAR (1, 2) and the findings that chemotherapeutic agents can enhance the ADCC activity of certain mAbs, we tested the potential synergistic effects that carboplatin may have on FAR immune effector function. Here we show the immunosuppressive effects that CA125 has on FAR-mediated tumor cell killing in vivo and demonstrate that carboplatin is able to suppress cell surface CA125 expression leading to enhanced FAR ADCC on FRA-expressing ovarian tumor cells. CA125 has been previously found to suppress FAR-mediated tumor cell killing in vitro. To determine its effect in vivo, we tested single agent FAR against isogenic tumor cells in mouse xenografts. OVCAR-3 is a FRA positive ovarian tumor cell line that expresses high levels of CA125 on its cell surface. A CA125 shRNA knockdown line (OV-KD) has been previously generated and shown to be more susceptible to FAR ADCC than its parental counterpart. Xenograft studies using these lines found that FAR had significant single agent tumor killing in the OV-KD xenografts in contrast to OVCAR-3 xenografts. We next tested FAR in vivo killing when used in combination with carboplatin. These data showed that carboplatin had a synergistic effect when combined with FAR treatment as compared to single agent treatment alone. To determine if this mechanism involved enhanced ADCC, we conducted similar studies in vitro whereby OVCAR-3 cells were treated with a sublethal concentration of carboplatin for 72 hrs, washed and then tested for FAR ADCC killing. These data found that FAR had enhanced ADCC activity on carboplatin treated cells as compared to untreated cells. Finally, to explore the potential mechanism by which this effect may occur, we examined the steady-state levels of both the mannose-6-phosphate receptor (M6PR), reported to be upregulated by chemotherapeutic drugs leading to enhanced ADCC via higher granzyme B uptake and the CA125 immunosuppressive factor. Our data found that both M6PR and CA125 expression were significantly suppressed following carboplatin exposure. These data support a mechanism by which carboplatin may enhance the humoral immune response for FAR and potentially other anti-tumor mAbs via downregulation of the immunosuppressive CA125 protein. 1. OncoTarget 8:66747-57, 20172. 2. EJI 201847707, 2018 Citation Format: J. Bradford Kline, Keiji Furuuchi, James Fulmer, Jennifer McDonough, Luigi Grasso, Nicholas C. Nicolaides. Synergistic effect of carboplatin on farletuzumab (FAR) tumor cell killing via downregulation of the humoral immunosuppressive CA125 protein and enhanced antibody dependent cellular cytotoxicity (ADCC) [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 2370.