anti-CD3 Bispecific Antibody Research Articles

19 Phase II Trial of Ubamatamab in MUC16-Expressing SMARCB1-Deficient Renal Medullary Carcinoma and Epithelioid Sarcoma

Abstract Background Mucin 16 (MUC16) is a large integral membrane glycoprotein that is highly expressed in malignancies such as ovarian cancer but only at low abundance in epithelial cells of normal tissues. Proteolytic cleavage of cell surface MUC16 results in the shedding of its extracellular portion, known as cancer antigen 125 (CA-125), into the bloodstream and a short, membrane-associated C-terminal MUC16 domain that remains on the cell surface. Renal medullary carcinoma (RMC) and epithelioid sarcoma (ES) are aggressive SMARCB1-deficient malignancies found to have elevated serum CA-125 levels in 70-80% of cases. Our preclinical studies suggest that upregulation of MUC16 upon SMARCB1 loss is a viable and attractive tumor target for SMARCB1-deficient malignancies such as ES and RMC. Ubamatamab is a human IgG4-based anti-MUC16 x anti-CD3 bispecific antibody that specifically targets the cell surface bound C-terminal MUC16 domain and can thus induce T cell–redirected killing of tumor cells even in the presence of high concentrations of CA-125. It would thus be a rationale therapy to use in SMARCB1-deficient malignancies expressing MUC16, including those such as RMC known to downregulate MHC Class I as a resistance mechanism to conventional immunotherapy. This is because CD3-targeting bispecific antibodies such as ubamatamab replace conventional signal 1 by engaging T cells regardless of MHC class I expression. As proof of concept, a 20-year-old patient with metastatic SMARCB1-negative ES expressing high levels of serum CA-125 achieved a durable (12+ months) partial response to ubamatamab after progressing on multiple prior therapies, including EZH2 inhibition with tazemetostat as well as anti-PD1/CTLA4 immune checkpoint inhibition with nivolumab plus ipilimumab. The patient reported Grade 2 CRS, pleural effusion, and pericardial effusion, all of which resolved without intervention1. This serves as proof-of-concept for the ability of CD3-targeted bispecifics to overcome resistance to immune checkpoint inhibition. Given this strong preclinical and clinical evidence, we have developed a phase II clinical trial of ubamatamab alone or in combination with the anti-PD1 immune-checkpoint inhibitor cemiplimab in patients with MUC16-expressing RMC and ES who have progressed on at least one line of prior therapy. Up to 20 patients will be enrolled from each disease cohort (ES and RMC) for a total of up to 40 patients. Patients enrolled in Stage I of the trial will receive ubamatamab monotherapy. Patients with disease progression on ubamatamab monotherapy during Stage I can proceed to stage II, which will evaluate the combination of ubamatamab with cemiplimab combination. The co-primary endpoints will be objective response rate (ORR) at any time during the trial and disease control rate (DCR) through 18 weeks. Secondary endpoints will include overall survival, progression-free survival, duration of response, and safety. All endpoints will be analyzed and reported separately for each disease cohort (RMC and ES), and for each Stage (ubamatamab monotherapy and combination ubamatamab with cemiplimab). The trial will utilize the time-to-event Bayesian Optimal Phase II (TOP) design, which maximizes statistical power with well-controlled type I errors. For patients with ES, the joint null hypotheses are that the objective response rate (ORR) is 15% and the disease control rate (DCR) is 26%. The regimen will be promising if either ORR is greater than 15% or DCR is greater than 26% with 69.6% power to declare this an interesting regimen if ORR is 30% and the DCR is 43%. For patients with RMC, the joint null hypotheses are that the objective response rate (ORR) is 15% and the disease control rate (DCR) is 15%. The regimen will be promising if either ORR is greater than 15% or DCR is greater than 15% with 71.4% power to declare this an interesting regimen if ORR is 30% and the DCR is 30%. Pre- and post-treatment correlative analyses will be performed in blood and tumor biopsy tissues to identify changes in specific immune cell subsets and elucidate the dynamic evolution of tumor and immune cell compartments as well as their spatial relationships following ubamatamab alone or in combination with cemiplimab. References 1 Revon-Riviere G, Chami R, Mills D, et al. Mucin 16 (cancer antigen 125) Expression in Epithelioid Sarcoma leads to Single-Patient Study with Bispecific T-Cell Engager Ubamatamab (Mucin16xCD3): A Bench-To-Bedside Experience. Connective Tissue Oncology Society, Nov 16–19, 2022, Vancouver, Canada.

Human plasma cells engineered to secrete bispecifics drive effective in vivo leukemia killing

Bispecific antibodies are an important tool for the management and treatment of acute leukemias. As a next step toward clinical translation of engineered plasma cells, we describe approaches for secretion of bispecific antibodies by human plasma cells. We show that human plasma cells expressing either fragment crystallizable domain-deficient anti-CD19×anti-CD3 (blinatumomab) or anti-CD33×anti-CD3 bispecific antibodies mediate Tcell activation and direct Tcell killing of B acute lymphoblastic leukemia or acute myeloid leukemia cell lines invitro. We demonstrate that knockout of the self-expressed antigen, CD19, boosts anti-CD19-bispecific secretion by plasma cells and prevents self-targeting. Plasma cells secreting anti-CD19-bispecific antibodies elicited invivo control of acute lymphoblastic leukemia patient-derived xenografts in immunodeficient mice co-engrafted with autologous Tcells. In these studies, we found that leukemic control elicited by engineered plasma cells was similar to CD19-targeted chimeric antigen receptor-expressing Tcells. Finally, the steady-state concentration of anti-CD19 bispecifics in serum 1month after cell delivery and tumor eradication was comparable with that observed in patients treated with a steady-state infusion of blinatumomab. These findings support further development of ePCs for use as a durable delivery system for the treatment of acute leukemias, and potentially other cancers.

An anti-EpCAM x anti-CD3 bispecific antibody, M701, for the treatment of malignant ascites due to epithelial cancer: Interim results of a prospective randomized controlled phase II trial.

An anti-EpCAM x anti-CD3 bispecific antibody, M701, for the treatment of malignant ascites due to epithelial cancer: Interim results of a prospective randomized controlled phase II trial.

Abstract 6706: An anti-claudin 18.2/CD3 bispecific antibody for the treatment of claudin 18.2 positive gastric cancer

Abstract The claudin18.2 (CLDN18.2) protein shows four transmembrane domains (TMDs) with two extracellular loops (ECL), ECL-1 and ECL-2. It is a highly selective biomarker with limited expression in normal tissues and often exhibits abnormal expression during the occurrence and development of various primary malignant tumors. The specific expression pattern supports the notion that CLDN18.2 is a distinctive molecule for targeted therapy in various cancers, particularly gastric and pancreatic cancers. Various drugs targeting CLDN18.2, including monoclonal antibodies, ADCs, CAR-T, and bispecific antibodies, have also entered clinical trials. As of this writing, there are currently no commercially available products worldwide that specifically target CLDN18.2. However, Zolbetuximab (IMAB362) has successfully reached the Phase III end point, indicating positive clinical outcomes and establishing CLDN18.2 as a promising cellular and antibody therapeutic option. Here, we describe LNF2007, an anti-CLDN 18.2/CD3 bispecific antibody that can redirect CD3+ effector T cells to CLDN18.2+ tumor sites, resulting in the activation of T cells and subsequent killing of target cells. The design of LNF2007 focuses on selecting a relatively weak and reasonable affinity to CD3, accompanied by the suppression of Fc-mediated effector functions. This aim is to minimize off-target toxicity and maximize therapeutic efficacy. In vitro data demonstrate that LNF2007 binds more strongly to CLDN18.2+cells than to CD3+ cells. LNF2007 exhibited good dose-dependent activation and cytotoxicity against engineered cell lines BXPC3-hCLDN18.2-Luc and CHOK1-hCLDN18.2-Luc, which are positive for CLDN18.2 expression .In the in vivo pharmacodynamics assay, LNF2007 also demonstrated superior efficacy in the humanized NUGC4-CLDN18.2 model and BxPC3-CLDN18.2 model. Furthermore, a 4-week repeated dose (up to 1 mg/kg) toxicity study in cynomolgus monkeys showed that LNF2007 was safe and well tolerated. In vitro cytokine release was lower in the LNF2007 group than that in the AMG 910 and AZD5863 (two another anti-claudin18.2/CD3 bispecific antibody) groups. In conclusion, the novel anti-CLDN18.2 × anti-CD3 bispecific antibody LNF2007 demonstrates similar efficacy to AMG 910 and AZD5863 and is safer. LNF2007 provides a promising therapy for claudin 18.2-positive cancer patients.Taishan Industry Leading Talents Project of Shandong Province was a sponsor of this research. Citation Format: Lili Zhao, Guimin Zhang, Zhong Liu, Jinhua Xu, Lizhi Zhao, Guangyan Li, Bin Li, Zhongsong Zhu, Wei Peng, Yuqiang Zhu, Zhaowei Chen, Zhenyu Li. An anti-claudin 18.2/CD3 bispecific antibody for the treatment of claudin 18.2 positive gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6706.

Initial Results from a Phase 1 Dose-Escalation Study of WVT078, a BCMA×CD3 Bispecific Antibody, in Combination with WHG626, a Gamma-Secretase (GS) Inhibitor, in Patients with Relapsed and/or Refractory Multiple Myeloma

Introduction: WVT078, a potent anti-B-cell maturation antigen (BCMA)×anti-CD3 bispecific antibody (BsAb), is being investigated as a single-agent and in combination with a GS inhibitor (GSI), WHG626 (AL102), in patients (pts) with relapsed and/or refractory (r/r) multiple myeloma (MM). Single-agent WVT078 showed an acceptable safety profile in the ongoing first-in-human study with active dose range of 48-250 µg/kg (Raab, Leukemia 2023). Membrane BCMA expressed on surface of MM cells is cleaved by GS. This results in shedding of its extracellular domain (ECD) as soluble BCMA (sBCMA), which may bind to and interfere with activity of BCMA-targeting agents such as WVT078. By preventing this shedding, GSIs are postulated to increase clinical benefit of BCMA-targeting agents. WVT078 combined with WHG626 was shown to enhance anti-myeloma activity of WVT078 in vitro preclinically (Raab, Leukemia 2023), supporting rationale for this combination in r/r MM. Methods: The combination of WVT078 and WHG626 is being investigated as part of above-mentioned phase 1 study (NCT04123418) in pts with MM who are r/r to ≥2 standard-of-care regimens, including an immunomodulatory drug, proteasome inhibitor, and anti-CD38 agent (if available). Pts who received prior BCMA chimeric antigen receptor T-cell therapy or BCMA antibody-drug conjugates therapy are included; pts with prior BCMA×CD3 BsAb treatment are excluded. Primary objectives were to evaluate safety and tolerability and to determine recommended dose for expansion of WVT078 in combination with WHG626. Secondary objectives were to assess preliminary anti-tumor activity and characterize pharmacokinetics (PK) and immunogenicity. Key exploratory objectives included evaluation of sBCMA and characterization of immune-cell activation phenotypes. Dose escalation was guided by Bayesian Logistic Regression Model, and International Myeloma Working Group criteria were used to assess disease response. Flow cytometry was used to study pharmacodynamic (PD) effects on immunophenotype of immune cells. Immunoassay-based platform (Meso Scale Discovery) was used for assessing cytokine production and enzyme-linked immunosorbent assay for quantifying serum sBCMA levels. Results: As of April 29, 2023, a total of 23 pts (median age, 64 years) with r/r MM were treated in dose escalation with intravenous WVT078 at 12-48 µg/kg once weekly, combined with oral WHG626 at 2-4 mg once daily, given 2 days on and 5 days off. Eighteen pts (78.3%) discontinued treatment due to progressive disease (n=15), adverse event (AE), guardian decision and physician decision (n=1 each). Most frequent (≥20%) treatment-related AEs across all doses in the combination were cytokine release syndrome (65.2%; Grade ≥3, n=1), pyrexia (39.1%), diarrhea (34.8%), decreased appetite (26.1%), hypophosphatemia, nausea and neutropenia (21.7% each); 5 pts experienced dose-limiting toxicities (pneumonia, neutropenia, ALT/AST/lipase increase, platelet count decrease, sepsis and shoulder pain). The safety profile is consistent with WVT078 and WHG626 as single agents. A maximum tolerated dose was not reached. The overall response rate (partial response or better; ORR) and overall complete response (CR) rate (stringent CR+CR) across all dose levels tested were 39.1% (n=9; 90% CI, 22.2, 58.3) and 13.0% (n=3; 90% CI, 3.7, 30.4), respectively; ORR at two highest dose levels combined was 57.1% (n=8/14; 90% CI, 32.5, 79.4). PK total (AUC) and maximal (Cmax) exposure to WVT078 in serum increased approximately proportionally to dose in Cycle 1. Evidence of T-cell engagement with WVT078 was demonstrated by upregulated peripheral T-cell proliferation and activation markers. WHG626 decreased serum sBCMA levels by 10% within first 24 hours of treatment prior to WVT078 dosing. WHG626 enhanced WVT078-mediated increases in serum inflammatory cytokine levels, and upregulated T-cell activation phenotype in bone marrow in a dose-dependent manner.Based on preliminary data, cytokine and clinical effects were observed at lower WVT078 doses with WVT078+WHG626 than with WVT078 alone. Conclusions: WVT078 combined with WHG626 has an acceptable safety profile and shows preliminary evidence of clinical activity at highest doses tested. PD biomarker analysis supports postulated mechanism of action of WHG626 combined with WVT078. This is the first clinical report on combination of BCMAxCD3 BsAb and GSI in r/r MM.

Clinical Characteristics, Treatment Patterns, and Outcomes of Patients with Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL) Refractory to Covalent Bruton's Tyrosine Kinase Inhibitor (BTKi) and Exposed to B-Cell Lymphoma 2 Inhibitor (BCL2i)

Introduction: CLL/SLL patients who failed BTKi and are treated with BCL2i represent a growing population with few standard-of-care treatment options after discontinuing both therapies. Patients who fail both BTKi and BCL2i have poor prognosis, with a median overall survival (OS) of 3.6 months (Lew et al., Blood Advances, 2021). However, real-world evidence for these patients is limited. This study described the characteristics, treatment patterns, and outcomes of CLL/SLL patients who were relapsed or were resistant/refractory/intolerant (R/R/R/I) to BTKi and who were exposed to BCL2i. Among patients who discontinued BCL2i, responses to the treatment immediately after BCL2i were reported. Methods: This retrospective chart review study evaluated Dana-Farber Cancer Institute patients with CLL/SLL (≥18 years old) who were R/R/R/I to BTKi and received BCL2i (in any order). Abstraction took place from 12/2021 to 07/2023. Patients were required to have records available from 6 months before to 12 months after first BTKi initiation. Patients who received non-hormonal antineoplastic therapy for other primary malignancies in the period between CLL/SLL diagnosis and receipt of their first BTKi treatment were excluded. Demographic and clinical characteristics at or before BCL2i initiation were described. Lines of treatment (LOTs) and responses to BCL2i were summarized. Time to treatment discontinuation, real-world PFS (rwPFS) and OS were estimated by Kaplan-Meier analysis. Patients were considered doubly refractory if they were R/R/R/I to BTKi and BCL2i. Overall response rate to first treatment after BTKi and BCL2i was summarized among doubly refractory patients. Results: Among 104 patients who were R/R/R/I to BTKi, 61 (58.7%) received a BCL2i. The patients exposed to both BTKi and BCL2i were observed for a median (interquartile range [IQR]) time of 2.6 (1.1,4.4) years after BCL2i initiation. 57 (93.4%) patients received BCL2i after BTKi and 4 (6.6%) received BCL2i before BTKi. BCL2i was most commonly (23 [37.7%] patients exposed to BCL2i) received in the fourth LOT and all patients received their first BCL2i after their first LOT. Median (IQR) age at BCL2i initiation was 68.4 (63.3-74.4) years. Among patients who were assessed for cytogenetic abnormalities (n=58), the most common abnormalities were del(13q) (55.2%) and del(17p) (36.2%). 36 (61.0%) patients had TP53 mutation. 45 (73.8%) patients discontinued their first BCL2i treatment. IGHV mutation was assessed for 49 patients and 8 (16.3%) had mutation rates ≥ 2%. Median (IQR) time to BCL2i discontinuation for patients receiving BCL2i was 1.5 (0.4, 3.1) years. 40 (76.9%) of the 52 patients with a known first response to BCL2i achieved clinician-assessed complete (CR) or partial response (PR) at first assessment. 25 (41.0%) patients were R/R/R/I to BCL2i at the time of abstraction. Of them, 21 (84.0%) progressed, 7 (28.0%) developed Richter transformation (RT) and 11 (44.0%) died. Primary cause of death was available for 8 (72.7%) patients and, of these, 5 (62.5%) died due to disease progression, 2 (25.0%) died due to a secondary malignancy, and 1 (12.5%) died from unspecified causes. Among doubly refractory patients, median (95% CI) rwPFS was 1.6 (0.7, 2.4) years and median OS was 3.8 (2.3, not reached) years from the initiation of the latter of BTKi and BCL2i treatment. Among doubly refractory patients, 18 (72.0%) received an additional LOT after the latter of BTKi and BCL2i. The therapies received in the first line after BTKi and BCL2i were allogeneic HSCT (4 patients), duvelisib (3 patients), oral CDK9i (2 patients), and 1 patient each with CAR-T, anti-CD20 bispecific antibody, alemtuzumab, vecabrutinib, zanubrutinib; and for patients with RT: venetoclax plus rituximab with anthracycline chemotherapy (2 patients), PI3Ki/PD-1 (1 patient), duvelisib (1 patient) ( Figure 1). Response to the additional LOT was known for 17 patients and unknown for 1 patient. Clinician-assessed CR or PR to treatment immediately after BCL2i and BTKi was achieved for 4 (23.5%) of these patients at first assessment. Conclusions: Patients with CLL/SLL who were failed by BTKi and BCL2i treatment have poor prognosis. Overall response rates to treatment immediately after BTKi and BCL2i treatment are low among doubly refractory patients. More effective treatments are needed to address the unmet therapeutic needs of CLL/SLL patients who are refractory to both BTKi and BCL2i.

Novel anti-CD30/CD3 bispecific antibodies activate human T cells and mediate potent anti-tumor activity.

CD30 is expressed on Hodgkin lymphomas (HL), many non-Hodgkin lymphomas (NHLs), and non-lymphoid malignancies in children and adults. Tumor expression, combined with restricted expression in healthy tissues, identifies CD30 as a promising immunotherapy target. An anti-CD30 antibody-drug conjugate (ADC) has been approved by the FDA for HL. While anti-CD30 ADCs and chimeric antigen receptors (CARs) have shown promise, their shortcomings and toxicities suggest that alternative treatments are needed. We developed novel anti-CD30 x anti-CD3 bispecific antibodies (biAbs) to coat activated patient T cells (ATCs) ex vivo prior to autologous re-infusions. Our goal is to harness the dual specificity of the biAb, the power of cellular therapy, and the safety of non-genetically modified autologous T cell infusions. We present a comprehensive characterization of the CD30 binding and tumor cell killing properties of these biAbs. Five unique murine monoclonal antibodies (mAbs) were generated against the extracellular domain of human CD30. Resultant anti-CD30 mAbs were purified and screened for binding specificity, affinity, and epitope recognition. Two lead mAb candidates with unique sequences and CD30 binding clusters that differ from the ADC in clinical use were identified. These mAbs were chemically conjugated with OKT3 (an anti-CD3 mAb). ATCs were armed and evaluated in vitro for binding, cytokine production, and cytotoxicity against tumor lines and then in vivo for tumor cell killing. Our lead mAb was subcloned to make a Master Cell Bank (MCB) and screened for binding against a library of human cell surface proteins. Only huCD30 was bound. These studies support a clinical trial in development employing ex vivo-loading of autologous T cells with this novel biAb.

DISCOVERY OF A CYNOMOLGUS MONKEY-CROSS-REACTIVE ANTI-HUMAN CD3 MAB FOR T CELL ENGAGERS

Abstract Background Anti-CD3 based T cell engager antibodies can redirect cytotoxic activity of T cells in a non-MHC restricted fashion to kill tumor cells effectively. Therefore, the discovery of an anti-CD3 antibody capable of activating T cells in the presence of tumor cells is highly desirable. Recently, many anti-CD3 bispecific antibodies (bsAbs) entered clinical trials. Despite the promising efficacy of anti-CD3 bsAbs, safety issues arose and establishing a proper therapeutic window between efficacy and safety became a challenge. One of the safety concerns for anti-CD3 bsAbs is the cytokine release syndrome due to T-cell activation. Recent studies have shown that this safety challenge can be mitigated by selecting an anti-CD3 antibody with the appropriate binding epitope, CD3 affinity and binding kinetics (on and off rate). Methods by using WuXi Biologics’ state-of-the-art hybridoma platform, an anti-CD3 Ab was discovered through a combination of immunization and screening strategies. Results the selected anti-CD3 Ab demonstrates moderate affinity and fast-on fast-off binding kinetics against both human and cynomolgus CD3 molecules. Once constructed into T cell engagers (TCEs) using this anti-CD3 Ab with TAA binding arms in WuXiBody® format, the obtained TCEs mediated efficient anti-tumor activity, but induced low levels of cytokine production by T cells. Conclusions WuXi Biologics has discovered an anti-CD3 Ab with desired binding properties to human CD3. As shown in two showcases, the TCEs constructed using this anti-CD3 Ab can elicit efficient T cell cytotoxicity against tumor cells but low levels of cytokine release. The cross-reactivity of the anti-CD3 Ab enables preclinical assessments of toxicity in NHP.

A Phase 1 Study of Plamotamab, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with Relapsed/Refractory Non-Hodgkin's Lymphoma: Recommended Dose Safety/Efficacy Update and Escalation Exposure-Response Analysis

Introduction: Plamotamab is a humanized bispecific antibody that binds both CD20 and CD3 and recruits cytotoxic T cells to kill CD20-expressing malignant cells. In the dose-escalation phase of an ongoing first-in-human (FIH) Ph 1 study (XmAb13676-01; NCT02924402), plamotamab was well tolerated with manageable cytokine release syndrome (CRS) and demonstrated evidence of clinical activity in heavily pretreated patients (pts) with relapsed/refractory (R/R) non-Hodgkin's lymphoma (NHL) (Patel; ASH 2021). Here, exposure-response (ER) analyses of the dose-escalation cohorts from the same study are reported. Safety and efficacy results from the follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) escalation (Part C) and expansion cohorts at the proposed recommended dosing regimen (RD) are also reported. Methods: The study is an FIH, multi-center, open-label Ph 1 dose-escalation study in R/R NHL pts. The dose-escalation phase has 3 Parts: Parts A and B using weight-based dosing; Part C using flat step-up doses (SUD). An IV RD was identified from Part C, which was used to expand into FL and DLBCL. Treatment was continued for ≥2 cycles if therapeutic benefit was evident. ER analysis was conducted based on exposure metrics calculated using population pharmacokinetic (popPK) model for plamotamab vs. observed responses related to efficacy/safety from Parts A, B, and C. Results: At data cut-off for RD safety/efficacy evaluation (25July2022), 36 pts were enrolled on or before 01April2022 (median age: 67 years, range: 36-86; 61% male). At baseline, 11.1% had stage III disease and 69.4% had stage IV disease. Median number of prior lines of therapy was 4 (range: 2-10), with 50% pts receiving CAR-T as a prior therapy (16 pts with DLBCL, 2 pts from other NHL subtypes, and no pts with FL). After last therapy, 91.7% of all pts had relapsed/progressed. In the RD safety population (n=36), CRS was the most common adverse event (AE; 72.2%). CRS was mostly confined to Cycle 1 and no Grade (Gr)≥3 CRS was reported. Treatment-emergent AEs (≥25%) included anemia (44.4%), pyrexia and nausea (38.9% each), asthenia (27.8%), and aspartate aminotransferase increase, diarrhea, and hypophosphatemia (25.0% each). Gr≥3 AEs (≥10%; 77.8% overall) were anemia (19.4%), neutropenia and neutrophil count decreased (16.7% each) and thrombocytopenia (11.1%). SAEs (≥5%; 55.6% overall) were CRS (25.0%), COVID-19 (8.3%), pneumonia and sepsis (5.6% each). AEs leading to plamotamab discontinuation occurred in 5 pts (13.9%). Overall, 25 pts were evaluable for efficacy at the RD. DLBCL pts at the RD (n=19) had an objective response (OR) rate of 47.4% (9/19 pts) and CMR/CR rate of 26.3% (5/19 pts); DLBCL pts with prior CAR-T had an OR rate of 46.2% (6/13 pts) and CMR/CR rate of 30.8% (4/13 pts). In FL pts at the RD (n=6), OR rate was 100% (6/6 pts) and CMR/CR rate was 50% (3/6 pts). The median time to initial response was 54 days for DLBCL and 56.5 days for FL. At data cut-off for ER analysis (10Nov2021) of Parts A, B and C only, exposure data were available from 55 pts who received at least 1 dose of plamotamab in the second cycle, were evaluable for CRS and for efficacy and safety at the target dose. For the first "priming” dose, plamotamab exposure correlated significantly with peak IL6 levels as well as incidence of Gr≥2 CRS events. At subsequent SUD, Postdose-Cmax / Predose-Ctrough ratio, indicative of the fold-change with each SUD, was the best predictor of any grade CRS events. At the target dose, no significant relationship exists between plamotamab exposure vs. all Gr≥3 AEs. A positive relationship exists for best OR, which is further improved by accounting for the impact of residual rituximab on plamotamab binding to CD20 using a competitive binding model. Conclusion: Plamotamab demonstrated evidence of clinical activity in heavily pretreated pts with DLBCL and FL with promising responses in pts with prior CAR-T therapy. CRS was generally manageable with premedication. Safety and efficacy evaluation of pts at the RD is currently ongoing, and updated results will be provided. Taken together, popPK/PD analysis of plamotamab exposure with IL6 levels, CRS incidence, high-grade AEs and OR rate provide guidance for RDs to be studied in future trials. A novel exposure metric was proposed to inform step-up dose increases that minimize the risk of CRS, while impact of rituximab on drug efficacy was captured as has been described in the literature. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Preclinical characterization of a Fab-like CD3/CLDN18.2 XFab® bispecific antibody against solid tumors

The claudin 18.2(CLDN18.2) antigen is highly expressed in gastric mucosa epithelial cells and frequently expressed in malignant tumors. Positive clinical outcomes have popularized claudin 18.2 as a novel cellular and antibody therapeutic. Here, we designed a bispecific antibody-ZWB67 using the XFab® platform, aimed at redirecting CD3+ effector T cells to CLDN18.2+ target cells or tissues. Physicochemical characterization, binding properties, T cell stimulatory activity, and T cell-dependent cellular cytotoxicity of ZWB67 were evaluated in dosage intervals using antigens of CD3 and target cells expressing CLDN18.2 or CD3. Then, the anti-tumor activity was assessed in humanized CD3EDG mice bearing MC-38-hCLDN18.2 tumors. Our data demonstrate that ZWB67 specifically binds to the human CD3e antigen (KD = 1.04E−08 M) and binds more strongly to CLDN18.2+ cells than to CD3+ cells (4.3- to 9.2-fold difference). ZWB67 showed good activity in the luciferase reporter system and exhibited dose-dependent activation, cytotoxicity of T cells, and cytokine release when co-cultured with CLDN18.2+ cells and CD3+ T cells. ZWB67 also exhibited high in vivo efficacy in the MC-38-hCLDN18.2 xenograft mouse model. In conclusion, the novel anti-CLDN18.2 × anti-CD3 bispecific antibody exhibited low affinity for anti-CD3, highly specific binding, potent cytotoxicity, and anti-tumor activity. These data provide a basis for future preclinical and clinical development of this therapeutic strategy.

Global multi-center phase I trial of the intraperitoneal infusion of anti-EpCAM x anti-CD3 bispecific antibody catumaxomab for advanced gastric carcinoma with peritoneal metastasis.

e16102 Background: Advanced gastric cancer (GC) patients (pts) have high incidence of peritoneal metastasis (PM), resulting in ascites, cachexia and poor life quality. EpCAM is highly expressed on GC but no on peritoneum. Catumaxomab intraperitoneal infusion (i.p.) was previously demonstrated to eradicate EpCAM+ cancers and control the malignant ascites in Europe (Heiss. Int. J. Cancer.2010). We present initial safety, pharmacokinetics (PK), and efficacy from the multi-center phase I trial of Catumaxomab on GC pts with PM in Asian population (NCT04222114). Methods: GC pts who had progressed on at least two prior standard systemic therapies with peritoneal metastasis were enrolled. Pts received Catumaxomab i.p. of 10 μg, 20 μg, 50 μg and 150 μg on days 1, 4, 8 and 11, respectively in the 1st cycle. From the 2nd cycle, Pts received Catumaxomab i.p. of 20 μg, 50 μg, 150 μg on days 1, 4 and 8, respectively. The cycle was 42 days in Cohort A, and 28 days in Cohort B. Catumaxomab PK were evaluated, tumor measurements and quantification of ascites by five-point method (Oriuchi, JJCO,2005) were performed Q6W. The primary endpoint was overall survival (OS); secondary endpoints were response rate of ascites, progression-free interval of peritoneal metastatic lesions and puncture-free survival (PuFS); Data cut-off date was Jan 29,2022. Results: 17 pts from 14 sites (median age: 52.5 yr, ECOG PS: 0 [n=2], 1 [n=14], 2[n=1], Cohort A:9, Cohort B:8) were treated. There were no dose-limiting toxicities (DLTs). The most common treatment-emergent adverse event (TEAE) was pyrexia (76.5%) and abdominal pain (58.8%). Grade ≥3 treatment related adverse events (TRAE) of abdominal pain (23.5%), bilirubin conjugated increased (23.5%), lymphocyte count decreased (17.6%), ALT increased (11.8%), and AST increased (11.8%) were reported. No treatment related death or neurotoxicity occurred in the study. Median overall survival was 102 days (95%CI: 38-166), with 10 (58.8%) deaths observed. For ascites, CR+PR was observed in 4 cases (33%), no PD case was reported. No therapeutic ascites drainage was recorded after cycle 1. Median PuFS was 116 days (95%CI: 28-157). Median progression-free interval of peritoneal metastatic lesions was 102 days (95%CI: 38-166). PK: Catumaxomab concentrations in plasma increased in a dose-dependent manner and were similar to Caucasian population in Europe. Conclusions: This clinical study indicated that multiple cycles of Catumaxomab i.p. were safe and well tolerated in Asian population. PK profile was similar. Early efficacy signals were promising, especially in pts with ascites, which will be further investigated in phase 3 study. Clinical trial information: NCT04222114.

HIV envelope antibodies and TLR7 agonist partially prevent viral rebound in chronically SHIV-infected monkeys.

A key challenge for the development of a cure to HIV-1 infection is the persistent viral reservoir established during early infection. Previous studies using Toll-like receptor 7 (TLR7) agonists and broadly neutralizing antibodies (bNAbs) have shown delay or prevention of viral rebound following antiretroviral therapy (ART) discontinuation in simian-human immunodeficiency virus (SHIV)-infected rhesus macaques. In these prior studies, ART was initiated early during acute infection, which limited the size and diversity of the viral reservoir. Here we evaluated in SHIV-infected rhesus macaques that did not initiate ART until 1 year into chronic infection whether the TLR7 agonist vesatolimod in combination with the bNAb PGT121, formatted either as a human IgG1, an effector enhanced IgG1, or an anti-CD3 bispecific antibody, would delay or prevent viral rebound following ART discontinuation. We found that all 3 antibody formats in combination with vesatolimod were able to prevent viral rebound following ART discontinuation in a subset of animals. These data indicate that a TLR7 agonist combined with antibodies may be a promising strategy to achieve long-term ART-free HIV remission in humans.

A Novel Anti-B7-H3 × Anti-CD3 Bispecific Antibody with Potent Antitumor Activity.

B7-H3 plays an important role in tumor apoptosis, proliferation, adhesion, angiogenesis, invasion, migration, and evasion of immune surveillance. It is overexpressed in various human solid tumor tissues. In patients, B7-H3 overexpression correlates with advanced stages, poor clinical outcomes, and resistance to therapy. The roles of B7-H3 in tumor progression make it a potential candidate for targeted therapy. Here, we generated a mouse anti-human B7-H3 antibody and demonstrated its binding activity via Tongji University Suzhou Instituteprotein-based and cell-based assays. We then developed a novel format anti-B7-H3 × anti-CD3 bispecific antibody based on the antibody-binding fragment of the anti-B7-H3 antibody and single-chain variable fragment structure of anti-CD3 antibody (OKT3) and demonstrated that this bispecific antibody mediated potent cytotoxic activities against various B7-H3-positive tumor cell lines in vitro by improving T cell activation and proliferation. This bispecific antibody also demonstrated potent antitumor activity in humanized mice xenograft models. These results revealed that the novel anti-B7-H3 × anti-CD3 bispecific antibody has the potential to be employed in treatment of B7-H3-positive solid tumors.

Safety and Anti-Tumor Activity of Plamotamab (XmAb13676), an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Subjects with Relapsed/Refractory Non-Hodgkin's Lymphoma

Safety and Anti-Tumor Activity of Plamotamab (XmAb13676), an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Subjects with Relapsed/Refractory Non-Hodgkin's Lymphoma

539P Interim results of a phase I study of M701, a recombinant anti-EpCAM and anti-CD3 bispecific antibody in EpCAM-positive cancer patients with malignant ascites

Malignant ascites in patients (pts) who had failed standard therapy have no effective and durable treatment. M701 is an anti-EpCAM/CD3 bispecific antibody which can engage the T cells and eliminate the EpCAM positive tumor cells. Here we report the interim results of a phase I trial of M701 in pts with malignant ascites who had failed standard therapies.

Abstract 1833: Development of anti-CLDN18.2-anti-CD3 bispecific antibody as cancer therapeutics

Abstract Claudin-18 (CLDN18) is a member of the large Claudin family of four-span transmembrane proteins, which are essential components of the mammalian tight junctions (TJs) in the epithelial cells. Claudin-18 has two splice variants, CLDN18.1 and CLDN18.2. While CLDN18.1 is specifically expressed in the lung tissue, CLDN18.2 expression in normal tissue is more restricted and is only detected in small patches of stomach mucosal. CLDN18.2 expression is elevated in many types of epithelial cancers including stomach, esophagus, pancreatic and ovarian cancers. Anti-CLDN18.2 monoclonal antibody Claudiximab (IMAB362) demonstrated promising results in clinical trials for gastric cancers. Using a combination of DNA, protein, and transfected cells as immunogens, we have generated a panel of mouse monoclonal antibodies which are highly specific for CLDN18.2 but do not cross-react to CLDN18.1. The lead antibody E9 had higher binding affinity for CLDN18.2, compared to the IMAB362. The humanized anti-CLDN18.2 antibody showed a strong antibody dependent cytotoxicity (ADCC) activity against Mia PaCa-2 cells overexpressing CLDN18.2. To redirect T-cell-mediated lysis toward CLDN18.2-overexpressed tumor cells, we generated an anti-CLDN18.2/anti-CD3 bispecific antibody. We demonstrated that the bispecific antibody binds to both human T cells and CLDN18.2-expressing tumor cells. Furthermore, the anti-CLDN18.2/anti-CD3 bispecific antibody had robust activity in killing Mia PaCa-2 cells overexpressing CLDN18.2 in the in vitro T cell-dependent cellular cytotoxicity (TDCC) assay. In addition, the bispecific antibody retained the in vitro ADCC activity against Mia PaCa-2 cells overexpressing CLDN18.2. Taken together, our data suggest that the anti-CLDN18.2/anti-CD3 bispecific antibody is a promising cancer therapeutic candidate utilizing multiple anti-tumor mechanisms of action, including ADCC and TDCC. Citation Format: Haishan Lin, Huey Li, Hunter Drobenaire, Veronica Pizzarella, Richard Zhang. Development of anti-CLDN18.2-anti-CD3 bispecific antibody as cancer therapeutics [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 1833.

Safety and Preliminary Antitumor Activity of the Anti-PD-1 Monoclonal Antibody REGN2810 Alone or in Combination with REGN1979, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with B-Lymphoid Malignancies

Safety and Preliminary Antitumor Activity of the Anti-PD-1 Monoclonal Antibody REGN2810 Alone or in Combination with REGN1979, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with B-Lymphoid Malignancies

Safety and Preliminary Clinical Activity of REGN1979, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with B-NHL Previously Treated with CD20-Directed Antibody Therapy

Safety and Preliminary Clinical Activity of REGN1979, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with B-NHL Previously Treated with CD20-Directed Antibody Therapy

Improving first-line treatment in diffuse large B-cell lymphoma

R-CHOP remains the standard of care in first-line treatment of diffuse large B-cell lymphoma (DLBCL), the most common lymphoma subtype. Patients who fail this therapy have a poor outcome, with relapse or refractory disease resulting in fatality in the majority. In this short paper, we summarize recent clinical studies exploring alternative regimens and efficacy of autologous stem cell transplantation (ASCT) consolidations. In ABC DLBCL, adequately identifying patients with poor prognosis but failed to recognize the patient for molecular target of therapy. Immunotherapy, which may potentially be used in less well genetically characterized patients, is most potent if used relative to chemotherapy protocols, therefore its optional combination remains to be determined. The hope is ultimately to move away from a universal chemotherapeutic mentality towards an individualized approach, be it through the use of a targeted small molecule or a biological drug. We discuss the role of new monoclonal antibodies such as obinutuzumab, brentuximab vedotin, polatuzumab vedotin and bispecific antibodies (BIABs) in first-line treatment regimens. BIABs which can bind to two different antigens at the same time are under investigation. After neurotoxic blinatumomab, anti-CD20/anti-CD3 BIABs take the lead, and due to their favorable toxicity profile they can be used in elderly patients with comorbidities, causing durable responses in patients with B-cell non-Hodgkin lymphoma who otherwise have limited options, even in those relapsing or refractory to chimeric antigen receptor (CAR) T-cell therapy.

Abstract 5654: Affinity tuned Xmab®2+1 anti-mesothelin x anti-CD3 bispecific antibody induces selective T cell-dependent cellular cytotoxicity of human ovarian cancer cells

Abstract Mesothelin (MSLN) is a tumor-associated antigen highly expressed in ovarian tumors. Current treatment options for ovarian cancer have only modest efficacy and there remains a large unmet need for new targeted therapies. We generated targeted T cell engager bispecific antibodies that bind MSLN on tumor cells and CD3 on T cells. The humanized and affinity-optimized MSLN x CD3 bispecific antibodies are in an XmAb® 2+1 Fab2-scFv-Fc format that bind bivalently to MSLN and monovalently to CD3. The affinity of the MSLN-targeting arms was reduced to promote avid binding to MSLN expressing cancer cell lines and to minimize reactivity on normal surrogate cell lines. We correlated the expression of MSLN on cancer cell lines to 191 biopsy cores of serous and mucinous ovarian cancer tissues by IHC to identify surrogate cell lines to test for T cell-dependent cellular cytotoxicity (TDCC) activity. MSLN-transfected A549 cells were found to stain as intensely as ovarian cancer tumors expressing high amounts of MSLN. OVCAR-8 cancer cells were found to correlate with a medium MSLN level density on ovarian cancer tumors while ASPC-1 cells represented low MSLN-expressing tumors. Finally, we correlated expression of MSLN to non-cancer adjacent tissues and identified SKOV3, HT29, MCF7, and A549 (parental) cancer cells as appropriate surrogates of normal tissues. Reduction of MSLN affinity of MSLN x CD3 XmAb® 2+1 bispecific antibodies led to preferential killing of MSLN-high target cells, with up to 45-fold more potent TDCC activity on OVCAR8 and ASPC-1 cancer cells compared to the selected normal surrogate cell lines. Engineering of selective MSLN x CD3 bispecific antibodies allows for preferential killing of cancer cells, potentially minimizing on-target/off-tumor effects that may contribute to dose-limiting toxicities. Citation Format: Veronica G. Zeng, Matthew S. Faber, Matthew J. Bernett, Kendra N. Avery, John L. Zeytounian, Rumana Rashid, Umesh S. Muchhal, Gregory L. Moore, John R. Desjarlais, Michael Hedvat. Affinity tuned Xmab®2+1 anti-mesothelin x anti-CD3 bispecific antibody induces selective T cell-dependent cellular cytotoxicity of human ovarian cancer 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 5654.