Complement-dependent Cytotoxicity Activity Research Articles

Positive associations of active immune therapy OBI-833/OBI-821 induced immune responses with clinical outcomes in patients with non-small cell lung cancer.

e14671 Background: OBI-833/OBI-821 (OBI-833) is a novel active immune therapy (cancer vaccine) targeting a tumor-associated carbohydrate antigen, Globo H. Previous reports have shown that OBI-833 can elicit a beneficial immune response in Non-Small Cell Lung Cancer (NSCLC) patients and rendered durable stable disease with some TKI-treated patients. In this study, we further evaluated the effect of OBI-833-induced immune responses on the in-study progression-free survivals (isPFS) during the treatment. Methods: Sera were collected for the evaluations of maximum concentration (Cmax) and exposure (area under the curve: AUC) of anti-Globo H IgM (GH IgM) and IgG (GH IgG), complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and ex-vivo GH IgM induction with PBMC from each subject at baseline. The correlations of OBI-833-induced immune responses with isPFS and best overall response (BOR) were also evaluated. Pearson correlation coefficient analysis was used for all correlation evaluations. Results: Among the 14 OBI-833-treated subjects, 93% and 64% of subjects had significant increase in GH IgM and GH IgG, respectively. Median Cmax GH IgM and Cmax GH IgG were 13.8 µg/mL and 12.4 µg/mL, respectively. While the increase in CDC activities was not significantly correlated with the increase of GH IgM, a weak association between GH IgG and ADCC was observed (r=0.3380, p<0.0001). In addition, a strong association (r=0.84) was observed between Ex-vivo IFN-γ secreting and their Cmax IgM concentration in the OBI-833 Ex-vivo stimulation study. In contrast, weak association (r=0.26) was observed between Ex-vivo GH IgM induction and their Cmax of IgM. Correlations of the immune responses on isPFS were further analyzed. Significant positive correlations were observed for the Cmax and AUC of GH IgM with isPFS (Cmax: r=0.6345, p=0.0148; AUC: r=0.8212, p=0.0003) and the Cmax and AUC of GH IgG with isPFS (Cmax: r=0.7192, p=0.0037; AUC: r=0.6306, p=0.0062). Furthermore, distinct features of GH IgG responses from 2 subjects were identified based on the ADCC-GH IgG scatter plot. Samples from subject 034-006 showed high ADCC activity with relatively low GH IgG concentration, whereas the BOR was at -27%, which has significant negative correlation of tumor response (TR) with GH IgG (r=-0.7381, p=0.0148) and ADCC (r=-0.8565, p=0.0016). In contrast, samples from subject 034-004 showed average ADCC activity and relatively high GH IgG concentration with BOR at -12%, showing a negative correlation of TR with GH IgG (r=-0.8352, p=0.0001) and ADCC (r=-0.5690, p=0.0269). Conclusions: OBI-833 can elicit beneficial immune responses in NSCLC patients. Both GH IgM and GH IgG may contribute to the isPFS and TR of the subjects. Further development of OBI-833 in EGFR-mutated NSCLC patients phase II trial is ongoing.

The Papain-like Protease Domain of Severe Acute Respiratory Syndrome Coronavirus 2 Conjugated with Human Beta-Defensin 2 and Co1 Induces Mucosal and Systemic Immune Responses against the Virus.

Most of the licensed vaccines against SARS-CoV-2 target spike proteins to induce viral neutralizing antibodies. However, currently prevalent SARS-CoV-2 variants contain many mutations, especially in their spike proteins. The development of vaccine antigens with conserved sequences that cross-react with variants of SARS-CoV-2 is needed to effectively defend against SARS-CoV-2 infection. Given that viral infection is initiated in the respiratory mucosa, strengthening the mucosal immune response would provide effective protection. We constructed a mucosal vaccine antigen using the papain-like protease (PLpro) domain of non-structural protein 3 of SARS-CoV-2. To potentiate the mucosal immune response, PLpro was combined with human beta-defensin 2, an antimicrobial peptide with mucosal immune adjuvant activity, and Co1, an M-cell-targeting ligand. Intranasal administration of the recombinant PLpro antigen conjugate into C57BL/6 and hACE2 knock-in (KI) mice induced antigen-specific T-cell and antibody responses with complement-dependent cytotoxic activity. Viral challenge experiments using the Wuhan and Delta strains of SARS-CoV-2 provided further evidence that immunized hACE2 KI mice were protected against viral challenge infections. Our study shows that PLpro is a useful candidate vaccine antigen against SARS-CoV-2 infection and that the inclusion of human beta-defensin 2 and Co1 in the recombinant construct may enhance the efficacy of the vaccine.

Abstract LB129: Preclinical development of a bispecific antibody-trap selectively targeting CD38 and CD47 for treating hematologic malignancies

Abstract CD38 and CD47 are co-expressed in various hematologic malignancies including multiple myeloma (MM), B-cell non-Hodgkin lymphoma (NHL), B-cell acute lymphoblastic leukemia (ALL), T-cell ALL and B-cell chronic lymphocytic leukemia (CLL). We present, herein, several CD38 antibody - CD47 ligand trap bispecific antibodies (BsAbs) in an ADCC-enhanced IgG1 form that harbor high CD38 binding affinity, low CD47 binding affinity, along with negligible affinity to red blood cells (RBCs) and no induction of RBCs agglutination. Using flow cytometry and Biolayer interferometry (BLI), we confirmed that our BsAbs can simultaneously bind to both CD38 and CD47, and that binding to either antigen first does not prevent binding to the other antigen subsequently. On CD47+/CD38low Jurkat (T leukemic) cells, our BsAbs reveal less blocking effect on the CD47/SIRPα interaction than a monospecific CD47 ligand trap molecule based on which our BsAbs were designed; conversely, on CD38/CD47 double-positive Reh (pro-B ALL) cells, our BsAbs reveal 200-500-fold greater blocking effect on the CD47/SIRPα interaction than the same monospecific CD47 ligand trap molecule, indicating that the inhibition of CD47/SIRPα by our BsAbs is depended on the engagement of CD38 on tumor cells. On CD47+/CD38+ Daudi (B NHL) lymphoma cells and L-1236 (B Hodgkin) lymphoma cells, four of our BsAbs inhibited CD38 enzymatic activity, which is responsible for immune-suppressive adenosine production in tumor microenvironment. Our BsAbs presented potent dose-dependent antibody-dependent cellular cytotoxicity (ADCC) against CD47+/CD38+ Raji (B NHL) and NCI-H929 (B plasmacytoma myeloma) cells, while revealing negligible ADCC activity against CD47+/CD38− cells, indicating low off-tumor toxicity. Likewise, our BsAbs also harbor potent antibody-dependent cellular phagocytosis (ADCP) activity against Raji NHL cells, varied degree of complement-dependent cytotoxicity (CDC) activity and direct apoptosis induction against Daudi NHL cells. In a mouse xenograft model harboring NCI-H929 multiple myeloma, our BsAbs produced more potent tumor growth inhibition, than monospecific anti-CD47 ligand trap, anti-CD38 (isatuximab) or combination of isatuximab and anti-CD47 ligand trap, at the same molecular dose per body weight. Notably, clone IMM5605-12C10 eradicated all tumors and achieved 100% complete response rate in a group of six mice. In summary, simultaneous targeting CD38 and CD47 using our CD38 antibody - CD47 ligand trap bispecific design in an ADCC-enhanced IgG1 form presents a novel multimodal approach for treating hematologic malignancies that are resistant to anti-CD38 antibodies. Citation Format: Wenzhi Tian, Song Li, Dianze Chen, Yanan Yang, Huiqin Guo, Dandan Liu, Ruliang Zhang, Fan Zhang. Preclinical development of a bispecific antibody-trap selectively targeting CD38 and CD47 for treating hematologic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB129.

A phase I study of EO-3021 in adult patients with solid tumors likely to express CLDN18.2.

TPS429 Background: Claudin 18 isoform 2 (CLDN18.2) belongs to a family of tight junction proteins with broad expression in gastric and gastroesophageal junction (GEJ), pancreatic, esophageal, and other solid tumors. Expression of CLDN18.2 in normal tissue is limited to the gastric mucosa, making it a promising antibody-drug conjugate (ADC) therapeutic target. Currently, there are no approved therapies targeting CLDN18.2. EO-3021 (also known as SYSA1801) is an ADC comprised of a fully human CLDN18.2 monoclonal antibody (mAb) specifically conjugated at glutamine 295 with a cleavable linker and MMAE with a homogenous drug-to-antibody ratio (DAR) of 2. In preclinical models, EO-3021 selectively delivers a potent cytotoxic MMAE payload directly to cancer cells expressing CLDN18.2, retains antibody-dependent cellular toxicity (ADCC) and complement-dependent cytotoxicity (CDC) activity, and exhibits a bystander effect.1 In an ongoing Phase 1 study in China (NCT05009966), EO-3021 exhibited signs of anti-tumor activity in patients with gastric cancer and had an acceptable safety profile.2 Outside of Greater China, EO-3021 is being evaluated by Elevation Oncology for the treatment of patients with advanced or metastatic solid tumors likely to express CLDN18.2, particularly gastric and GEJ adenocarcinomas. Methods: This is a Phase I, open-label, multi-center, dose escalation and expansion study to investigate the safety, tolerability, pharmacokinetics (PK) and preliminary anti-tumor activity of EO-3021 in patients with solid tumors likely to express CLDN18.2 (NCT05980416). Patients whose tumors have progressed on or after standard therapy, or who are intolerable for available standard therapy are eligible for participation. Approximately 120 patients will be enrolled in this study. There are 4 planned dose levels in the dose finding portion of the study. Patients will receive EO-3021 intravenously (IV) once every three weeks until disease progression or unacceptable toxicity. The expansion cohort will evaluate EO-3021 in patients with gastric/GEJ adenocarcinoma. Provision of tumor samples (archived and fresh biopsy) is required for study enrollment. CLDN18.2 expression in tumor tissue via will be assessed by retrospective evaluation via central immunohistochemistry assay; results will be explored for possible correlation with tumor response. Enrollment in the dose escalation portion of the study began in August 2023. 1. Dan M, et al. Cancer Res. 83, 2023. 2. Wang Y, et al. J Clin Oncol. 41, 2023. Clinical trial information: NCT05980416 .

Development of therapeutic monoclonal antibodies against DKK1 peptide-HLA-A2 complex to treat human cancers

BackgroundTargeted immunotherapy with monoclonal antibodies (mAbs) is an effective and safe method for the treatment of malignancies. Development of mAbs with improved cytotoxicity, targeting new and known tumor-associated antigens, therefore...

New Frontiers in Monoclonal Antibodies for Relapsed/Refractory Diffuse Large B-Cell Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive lymphoma. Approximately 60% of patients are cured with R-CHOP as a frontline treatment, while the remaining patients experience primary refractory or relapsed disease (R/R). The prognosis for R/R DLBCL patients who are neither eligible for autologous stem-cell transplantations nor CAR-T-cell treatment is poor, representing an important unmet need. Monoclonal antibodies (mAbs) have dramatically improved therapeutic options in anti-cancer strategies, offering new opportunities to overcome chemo-refractoriness in this challenging disease, even in cases of primary non-responder DLBCL. Several novel mAbs, characterized by different mechanisms of action and targets, are now available for R/R DLBCL. Unbound mAbs induce an immune response against cancer cells, triggering different mechanisms, including antibody-dependent cellular cytotoxicity (ADCC), activation of antibody-dependent cell-mediated phagocytosis (ADCP) and complement-dependent cytotoxicity (CDC). Antibody-drug conjugates (ADCs) and radioimmunotherapy (RIT), respectively, deliver a cytotoxic payload or a beta-emitter radionuclide to the targeted cells and nearby bystanders. Bispecific T-cell engagers (BiTes) and immune checkpoint inhibitors (ICIs) redirect and enhance the immune response against tumor cells. Here, we review therapeutic strategies based on monoclonal antibodies for R/R DLBCL.

Antipodoplanin antibody enhances the antitumor effects of CTLA-4 blockade against malignant mesothelioma by natural killer cells.

Combination immunotherapy with multiple immune checkpoint inhibitors (ICIs) has been approved for various types of malignancies, including malignant pleural mesothelioma (MPM). Podoplanin (PDPN), a transmembrane sialomucin-like glycoprotein, has been investigated as a diagnostic marker and therapeutic target for MPM. We previously generated and developed a PDPN-targeting Ab reagent with high Ab-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). However, the effects of anti-PDPN Abs on various tumor-infiltrating immune cells and their synergistic effects with ICIs have remained unclear. In the present study, we established a novel rat-mouse chimeric anti-mouse PDPN IgG2a mAb (PMab-1-mG2a ) and its core-fucose-deficient Ab (PMab-1-mG2a -f) to address these limitations. We identified the ADCC and CDC activity of PMab-1-mG2a -f against the PDPN-expressing mesothelioma cell line AB1-HA. The antitumor effect of monotherapy with PMab-1-mG2a -f was not sufficient to overcome tumor progression in AB1-HA-bearing immunocompetent mice. However, PMab-1-mG2a -f enhanced the antitumor effects of CTLA-4 blockade. Combination therapy with anti-PDPN Ab and anti-CTLA-4 Ab increased tumor-infiltrating natural killer (NK) cells. The depletion of NK cells inhibited the synergistic effects of PMab-1-mG2a -f and CTLA-4 blockade invivo. These findings indicated the essential role of NK cells in novel combination immunotherapy targeting PDPN and shed light on the therapeutic strategy in advanced MPM.

Abstract C121: Development of CRB-701 (SYS6002): A novel site-specific, Nectin-4 targeting ADC

Abstract CRB-701 (SYS6002) is a clinical stage, next generation ADC targeting Nectin-4 wherein two monomethyl auristatin E (MMAE) moieties are site-specifically conjugated to a novel Nectin-4 targeting IgG1 antibody via a cleavable linker. Nectin proteins are cell adhesion molecules belonging to the immunoglobulin (Ig) superfamily that participate in cell-to-cell interactions and form adhesion junctions between cells. Nectin-4 is widely expressed in epithelial cancers including bladder, breast, lung, colorectal, pancreatic, and ovarian. By contrast the expression level of Nectin-4 is very low in healthy adult human tissues. Due to this differential expression, Nectin-4 has emerged as a robust tumor associated antigen (TAA) that has been clinically validated in urothelial carcinoma by Enfortumab Vedotin (EV). While approved, EV carries associated toxicity concerns including skin rash, peripheral neuropathy and ocular toxicities that can lead to EV discontinuations and lasting adverse effects. CRB-701 (SYS6002) has demonstrated high affinity Nectin-4 binding (~2ng/ml) across species and has selectivity for Nectin-4 among the Nectin family of proteins (>5000 ng/ml). The antibody retains potent in vitro activity against FcgRI and C1q (<10nM) conferring antibody dependent cellular cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC) activity in vitro. Compared to EV, CRB-701 (SYS6002) reduces free MMAE exposure by 4.8-9.7-fold when adjusted to ADC exposure (AUC) and there is a 2.2-7.4-fold reduction in MMAE in circulation based on Cmax in rats and non-human primates. Collectively these data reflect lower free MMAE in plasma, reducing the risk of MMAE-induced toxicities observed with EV in the clinic. This improved PK and safety profile coincides with a longer half-life of the ADC in plasma potentially reducing the frequency of administration to achieve efficacy. The internalization rate of CRB-701 (SYS6002) was 2-fold faster than EV when assessed in nectin-4 expressing cells. These data may explain the statistically significant reduction in tumor growth observed in a BL0597 patient derived xenograft model (PDX) of bladder cancer with low Nectin-4 protein expression by IHC (H score =50) when compared to EV at the same dose and frequency. Collectively these data suggest that CRB-701 (SYS6002) could demonstrate an improved therapeutic index and PK profile relative to EV and as such could achieve higher tolerated concentrations at lower dose frequency. The stability of the site-specific linker and the reduction in the drug-antibody ratio (DAR) could lead to a differentiated profile clinically that enables higher doses, longer treatment duration and a greater potential in drug combinations in nectin-4 positive tumors. CRB-701 (SYS6002) is currently being explored clinically in a phase 1 dose escalation with an anticipated completion date mid-2024. Citation Format: Rachael Brake, Zhaopeng Sun, Mo Dan, Lu Lv, Congcong Niu, Yang Zhang, Mingyue Shen, XiXin Hu, Xiwu Hui, Andrew Kolodziej. Development of CRB-701 (SYS6002): A novel site-specific, Nectin-4 targeting ADC [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C121.

ZGGS15, a Novel IgG4 Bispecific Monoclonal Antibody Targeting Both LAG-3 and Tigit, Demonstrates Outstanding Anti-Tumor Activity and Can be Used As Monotherapy or in Combination with Anti-PD-1 Antibodies for Cancer Immunotherapy

Background This study aims to evaluate the anti-tumor efficacy of ZGGS15, a novel IgG4 bispecific monoclonal antibody (BsAb) targeting TIGIT and LAG-3, for cancer immunotherapy. Methods: ZGGS15 was generated in-house with the standard recombinant BsAb technology. ZGGS15 proteins were purified with protein A affinity column chromatography and evaluated for purity by size-exclusion high-performance liquid chromatography. The ZGGS15 affinity was assessed using a biolayer interferometry (BLI) assay. The EC50s of ZGGS15 binding to TIGIT and LAG-3 were determined using the ELISA technique. The EC50s of ZGGS15 binding to REH, Hela, MCF-7, and HCC1954 cells were measured by flow cytometry. Antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activities were also evaluated by flow cytometry. BALB/c-hPD-1/hLAG-3 and BALB/c-hPD-1/hTIGIT subcutaneously transplanted with CT26.WT tumor mouse models, and peripheral blood mononuclear cells (PBMC) -humanized NOG bearing A375 tumor mouse model were used for in vivo anti-tumor efficacy evaluation. Results ZGGS15 binds specifically to activated CD4 + and CD8 + T cells and human LAG-3 and TIGIT proteins expressed by CHO-K1 cells identically with a dose-dependent nanomolar affinity of 0.69 nM and 1.87 nM for human LAG-3 and TIGIT, respectively. In vitro kinetic analysis BLI results revealed ZGGS15 has high affinity for human LAG-3 and human TIGIT proteins, with KDs of 3.05 nM and 2.65 nM, respectively. ZGGS15 binds to human LAG-3 and human TIGIT simultaneously with similar affinity. Furthermore, ZGGS15 competitively inhibited the binding of LAG-3 to MHC-II (IC50 = 0.77 nM) and the binding of TIGIT to CD155 (IC50=0.24 nM). ZGGS15 induced better T cell activation than single anti-LAG3 or anti-TIGIT mAb agent or combined with different stimuli with or without cancer cells. When combined with nivolumab, ZGGS15 can further enhance the T cell activation in a dose-dependent manner. ADCC/CDC assay results showed that ZGGS15 binding to target cells does not induce ADCC or CDC. ZGGS15 interacts with the human neonatal Fc receptor in a pH-dependent manner, which can promote recirculation of ZGGS15 with a prolonged half-life in plasma. Besides, ZGGS15 interacts with human Fc-γ receptors and the human complement component, C1q, with low binding affinities. However, ZGGS15 does not induce obvious cytokine production from PBMCs, including IFN-γ, IL-2, IL-6, IL-10, and TNF-α. In vivo anti-tumor efficacy for ZGG15 in PBMC humanized NOG mice bearing A375 tumors showed that ZGGS15 had significant anti-tumor effects in the subcutaneous A375 xenograft model. ZGGS15 showed a better anti-tumor inhibition than single anti-LAG-3 or anti-TIGIT agent and a synergetic effect when combined with nivolumab. On day 18 post-treatment, the ZSAB015 plus nivolumab treatment demonstrated a significantly tumor growth inhibition (TGI) of 95.80% ( p =0.001), compared with the vehicle group. In vivo efficacy tests in BALB/c-hPD-1/hLAG-3 mice subcutaneously transplanted with CT26.WT tumor model showed that both high and low doses of ZGGS15 could inhibit the growth of CT26.WT colon cancer. The combination of high-dose ZGGS15 plus nivolumab has better efficacy than high-dose ZGGS15 and is slightly better than nivolumab alone. The tumor volume inhibition rate (TGITV) for ZGGS15 at 2 mg/kg was 69.70%, and for ZGGS15 at 5 mg/kg plus nivolumab at 1 mg/kg, it was 94.03% ( p < 0.001). During the experiment, the tumor-bearing mice tolerated it well, and no adverse reactions were observed. In vivo efficacy tests of ZGG15 in BALB/c-hPD-1/hTIGIT mice subcutaneously transplanted with CT26.WT tumor model showed that ZGGS15 at a low dose (1.5 mg/kg) demonstrated a significant tumor inhibitory effect, with the TGITV of 51.42% ( p < 0.01). The combination of ZGGS15 high-dose with nivolumab (5 mg/kg + 1 mg/kg) showed a better tumor inhibitory effect compared with ZGGS15 high-dose (5 mg/kg), with the TGITV of 81.15% and 41.54%, respectively ( p < 0.05). Conclusions ZGGS15 has excellent anti-tumor activity by inhibiting LAG-3 and TIGIT as a new IgG4 BsAb. ZGGS15 also exhibits potent anti-tumor efficacy in transgenic mouse models combined with nivolumab. Additionally, ZGGS15 does not elicit ADCC or CDC, therefore avoiding the cross-reaction of non-target binding. Finally, ZGGS15 does not induce cytokine production, mitigating any potential adverse effects of CRS.

GEN3014 (HexaBody ®-CD38) in Anti-CD38 Mab-Naive Patients with Relapsed/Refractory Multiple Myeloma: Preliminary Results from a Dose-Expansion Cohort of a Phase 1/2 Trial

Background: The treatment landscape for relapsed/refractory multiple myeloma (RRMM) has changed dramatically with the approval of CD38-targeted antibodies such as daratumumab. Despite this advancement in therapy, some patients still experience progression following daratumumab regimens. Clinical outcomes may be improved by more potent CD38-targeted treatment options. GEN3014 (HexaBody ®-CD38) is a next-generation human IgG1 anti-CD38 monoclonal antibody (mAb) that contains a hexamerization-enhancing mutation, E430G, that facilitates highly efficient complement-dependent cytotoxicity (CDC). In preclinical studies, GEN3014 showed robust tumor-cell killing through highly potent CDC, with increased efficiency compared with daratumumab, as well as potent antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis (Hiemstra et al, eBioMedicine 2023). Preliminary dose-escalation data from the first-in-human phase 1/2 trial of GEN3014 in RRMM patients showed clinical activity and a tolerable safety profile, and the recommended phase 2 dose was 16 mg/kg (NCT04824794). Based on these findings, expansion was initiated. Herein we describe the preliminary results of an expansion cohort in anti-CD38 mAb-naive RRMM patients. Methods: Adult RRMM patients were eligible if they had ≥3 prior lines of therapy including a proteasome inhibitor (PI) and an immunomodulatory imide drug (IMiD), were double refractory to a PI and an IMiD, or had ≥2 prior lines of therapy with 1 combining a PI and an IMiD. Patients received GEN3014 16 mg/kg intravenously in 28-day cycles (QW, cycles 1-2; Q2W, cycles 3-6; Q4W, cycles ≥7). The primary objective was to assess the preliminary antitumor activity of GEN3014. Secondary objectives included assessment of safety, tolerability, and pharmacokinetics/pharmacodynamics. Results: As of May 5, 2023, 11 anti-CD38 mAb-naive RRMM patients were treated in this expansion cohort (median age, 66 years; range, 56-75). With a median duration of exposure of 2.4 months (range, 0.2-8.3), 4 patients (36.4%) remained on treatment. Primary reasons for discontinuation included disease progression (n=3), AEs (n=3), and death (n=1). The most common treatment-emergent AEs (TEAEs) were neutropenia (36.4%), headache (27.3%), infusion-related reactions (IRRs; 27.3%), and thrombocytopenia (27.3%). IRRs were all grade 2 and did not lead to treatment discontinuation. There were 2 grade 5 TEAEs (respiratory tract infection, n=1; cardiac arrest, n=1). Of the 11 patients treated, 7 received ≥1 cycle of GEN3014, and among them, the best overall responses were 1 complete response, 2 very good partial responses, 2 partial responses, 1 minimal response, and 1 stable disease. GEN3014 treatment was associated with a transient reduction in either complement component C2 or total complement lytic activity in all patients, suggesting CDC activity. T cells transiently decreased after administration of the first dose in all patients, and T-cell expansion (≥50% increase from baseline for ≥2 visits) was observed in 2 of 4 evaluable patients who reached cycle 3 day 1 at the time of analysis. Updated data will be presented. Conclusions: GEN3014 showed a manageable safety profile and clinical activity in anti-CD38 mAb-naive RRMM patients in this expansion cohort. The preliminary pharmacodynamic observations were in line with observations from the dose-escalation part of the study. The study is ongoing and open for enrollment.

Iberdomide Enhances Dara Mediated Cytotoxicity through Upregulation of CDC Activity and Elevated NK Cell Mediated ADCC

Background: Multiple Myeloma (MM) is an incurable hematological malignancy with current treatments comprising combination regimens, typically featuring immunomodulatory agents (IMiDs) due to their potent anti-tumor activity and immunomodulatory effects. Clinical studies utilizing the combination of IMiD agents and daratumumab (DARA), an anti-CD38 monoclonal antibody, have shown improved patient outcomes for MM. However, patients ultimately relapse demonstrating the need for novel therapies. Iberdomide (IBER) is a novel cereblon E3 ligase modulator. It promotes faster and deeper degradation of the substrate targets compared to IMiDs, resulting in enhanced anti-proliferative, pro-apoptotic and immune stimulatory activity. In early clinical studies, IBER has been shown to overcome resistance to IMiDs and in the ongoing Phase 3 EXCALIBER study (NCT04975997) is being explored for treatment of newly diagnosed (ND) and relapsed/refractory (RR) MM in combination with DARA and dexamethasone. Here, we investigate the potential mechanisms of synergy between IBER and DARA in preclinical models. Methods: Complement dependent cytotoxicity (CDC) of DARA was assessed with 15% human serum for human complement components and assays were performed by titrating either single agent or combinations in a tritiated thymidine assay. Antibody dependent cellular cytotoxicity (ADCC) was performed by co-culturing MM cells with varying expression levels of CD38 and effector cells and assessing target cell viability with annexin-v/topro-3 flow. A humanized PBMC adoptive transfer mouse model, utilizing human PBMC engraftment 14 days prior to implantation, was used to assess in vivo activity of IBER, DARA and IBER + DARA. Results: In CDC assays, we observed variable sensitivity of MM cells to complement-specific CDC in the presence of DARA (0.1-1 µg/ml), regardless of cell surface CD38 expression. Notably, IBER treatment resulted in upregulation of CD38 surface expression in 60% of MM cell lines tested. LP1 and MOLP8 displayed susceptibility to DARA-mediated CDC. DARA showed a dose-dependent increase in CDC activity in both cell lines. Notably, IBER+DARA also showed ~35% more synergistic CDC activity in both cell lines, than the single agents. In ADCC assays, we observed pretreatment of PBMC with IBER (vs. DMSO) significantly increased DARA mediated ADCC in H929 and LP-1 cells. To confirm that this effect was directed by NK cells, we cultured NK cells for 24 hr in supernatants from stimulated PBMC in presence of IBER prior to co-culture with MM cells. We noted that IBER-treated PBMC supernatant significantly enhanced the NK ADCC activity of DARA suggesting that IBER enhancement of cytokine secretion from PBMC increases NK cell mediated ADCC. Orthogonally, we pre-treated MM cells with IBER or DMSO prior to co-culture in ADCC assay. Notably, IBER treatment of MM cells, without treating immune cells, also increased DARA-mediated ADCC, indicating that IBER directly increases sensitivity to DARA-directed ADCC. To investigate the MOA of IBER-DARA synergy in ADCC, we analyzed gene expression and cell surface changes of a panel of NK-specific receptor ligands on MM cells following treatment with IBER. We observed IBER-induced upregulation of MICA mRNA levels (~2x) and surface expression (~40%) in MM target cells. We used RNAi to knock down Ikaros, an IBER substrate, which resulted in increased MICA expression (~3x) in MM cells. Furthermore, we observed that RNAi knock down of MICA in MM cells resulted in a significant decrease (60%, p<0.0001) in MM cell killing by NK cells, suggesting IBER-enhanced sensitivity of MM cells to NK-cell killing was in part, due to the upregulation of MICA through degradation of Ikaros. Lastly, we examined the anti-MM effects of IBER in a humanized xenograft model with a lenalidomide resistant cell line. Longitudinal analysis identified persistence of human PBMC engraftment and activation of immune subsets (NK cells and T-cells) that were increased upon IBER treatments, consistent with clinical observations. The combination of IBER/DARA resulted in ~22% tumor growth inhibition (TGI) in comparison to single agents, DARA and IBER and ~37% TGI in comparison to vehicle. Conclusion: Taken together, these data demonstrate that IBER and DARA work synergistically in preclinical models primarily through enhancement of both ADCC and CDC. This combination has the potential to improve outcomes in MM.

Effective clearance of rituximab-resistant tumor cells by breaking the mirror-symmetry of immunoglobulin G and simultaneous binding to CD55 and CD20

Complement-dependent cytotoxicity (CDC), which eliminates aberrant target cells through the assembly and complex formation of serum complement molecules, is one of the major effector functions of anticancer therapeutic antibodies. In this study, we discovered that breaking the symmetry of natural immunoglobulin G (IgG) antibodies significantly increased the CDC activity of anti-CD20 antibodies. In addition, the expression of CD55 (a checkpoint inhibitor in the CDC cascade) was significantly increased in a rituximab-resistant cell line generated in-house, suggesting that CD55 overexpression might be a mechanism by which cancer cells acquire rituximab resistance. Based on these findings, we developed an asymmetric bispecific antibody (SBU-CD55 × CD20) that simultaneously targets both CD55 and CD20 to effectively eliminate rituximab-resistant cancer cells. In various cancer cell lines, including rituximab-resistant lymphoma cells, the SBU-CD55 × CD20 antibody showed significantly higher CDC activity than either anti-CD20 IgG antibody alone or a combination of anti-CD20 IgG antibody and anti-CD55 IgG antibody. Furthermore, the asymmetric bispecific antibody (SBU-CD55 × CD20) exhibited significantly higher CDC activity against rituximab-resistant cancer cells compared to other bispecific antibodies with symmetric features. These results demonstrate that enhancing CDC with an asymmetric CD55-binding bispecific antibody could be a new strategy for developing therapeutics to treat patients with relapsed or refractory cancers.

The Influence of Human IgG Subclass and Allotype on Complement Activation.

Complement activation via the classical pathway is initiated when oligomeric Igs on target surfaces are recognized by C1 of the complement cascade. The strength of this interaction and activation of the complement system are influenced by structural variation of the Ab, including Ab isotype, subclass, and glycosylation profile. Polymorphic variants of IgG have also been described to influence Fc-dependent effector functions. Therefore, we assessed complement binding, deposition, and complement-dependent cytotoxicity (CDC) of 27 known IgG allotypes with anti-trinitrophenyl specificity. Differences between allotypes within subclasses were minor for IgG1, IgG3, and IgG4 allotypes, and more substantial for IgG2. Allelic variant IGHG2*06, containing a unique serine at position 378 in the CH3 domain, showed less efficient complement activation and CDC compared with other IgG2 polymorphisms. We also observed variable cell lysis between IgG1 and IgG3, with IgG3 being superior in lysis of human RBCs and Ramos cells, and IgG1 being superior in lysis of Raji and Wien133 cells, demonstrating that a long-standing conundrum in the literature depends on cellular context. Furthermore, we compared IgG1 and IgG3 under different circumstances, showing that Ag density and Ab hinge length, but not complement regulators, define the context dependency of Ab-mediated CDC activity. Our results point toward a variation in the capacity of IgG subclasses to activate complement due to single amino acid changes and hinge length differences of allotypes to activate complement, which might give new insights on susceptibility to infectious, alloimmune, or autoimmune diseases and aid the design of Ab-based therapeutics.

Tumor cell-expressed lipolysis-stimulated lipoprotein receptor negatively regulates T-cell function.

Lipolysis-stimulated lipoprotein receptor (LSR) is known as a lipoprotein receptor. LSR is expressed in various solid tumors, including epithelial ovarian, gastric, and colon cancers. High LSR expression is significantly associated with poor prognosis, but its role in cancer has not been fully elucidated. LSR belongs to the Ig protein superfamily, which is conserved in B7 family. Here, we assessed LSR as a novel immune checkpoint molecule. We developed a novel anti-LSR antibody (#27-6 mF-18) that defects antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity activity. The #27-6 mF-18 cross-reacts with both human and mouse LSR. We found that LSR was expressed on 4T1 murine breast cancer cell line. The #27-6 mF-18 exhibited antitumor effects against the 4T1 syngeneic tumor model, a poor immunogenic model refractory to treatment with anti-PD-1 or anti-CTLA-4 antibodies. Compared with control antibody-treated mice, mice treated with #27-6 mF-18 showed significantly increased numbers of CD8+ T cells and a ratio of activated CD8+ T cells infiltrated in the tumor tissue. This antitumor effect was abrogated by CD8+ T-cell depletion through anti-CD8 antibody treatment, indicating that LSR negatively regulates tumor immunity by repressing CD8+ T cells. These findings show that LSR negatively regulates T-cell immune activity. LSR targeting could provide immune checkpoint inhibitors for cancer immunotherapy.

Levels and in vitro functional effects of circulating anti-hinge antibodies in melanoma patients receiving the immune checkpoint inhibitor pembrolizumab.

The efficacy of PD-1 monoclonals such as pembrolizumab can be modulated by the signals delivered via their Fc region. Tumour/inflammation associated proteases can generate F(ab')2 fragments of therapeutic monoclonals, and subsequent recognition of F(ab')2 epitopes by circulating anti-hinge antibodies (AHA) can then, potentially, link F(ab')2 binding to the target antigen with novel Fc signalling. Although elevated in inflammatory diseases, AHA levels in cancer patients have not been investigated and functional studies utilising the full repertoire of AHA present in sera have been limited. AHA levels in pembrolizumab treated melanoma patients (n = 23) were therefore compared to those of normal donors and adalimumab treated patients. A subset of melanoma patients and the majority of adalimumab patients had elevated levels of AHA reactive with F(ab')2 fragments of IgG4 anti-PD-1 monoclonals (nivolumab, pembrolizumab) and IgG1 therapeutic monoclonals (rituximab, adalimumab). Survival analysis was restricted by the small patient numbers but those melanoma patients with the highest levels (>75% percentile, n = 5) of pembrolizumab-F(ab')2 reactive AHA had significantly better overall survival post pembrolizumab treatment (p = 0.039). In vitro functional studies demonstrated that the presence of AHA+ sera restored the neutrophil activating capacity of pembrolizumab to its F(ab')2 fragment. Neither pembrolizumab nor its F(ab')2 fragments can induce NK cell or complement dependent cytotoxicity (CDC). However, AHA+ sera in combination with pembrolizumab-F(ab')2 provided Fc regions that could activate NK cells. The ability of AHA+ sera to restore CDC activity was more restricted and observed using only one pembrolizumab and one adalimumab patient serum in combination with rituximab- F(ab')2. This study reports the presence of elevated AHA levels in pembrolizumab treated melanoma patients and highlight the potential for AHA to provide additional Fc signaling. The issue of whether tumour associated proteolysis of PD-1 mAbs and subsequent AHA recognition impacts on treatment efficacy requires further study.

Preclinical anti-tumour activity of HexaBody-CD38, anext-generation CD38 antibody with superior complement-dependent cytotoxic activity.

HexaBody®-CD38 (GEN3014) is a hexamerization-enhanced human IgG1 that binds CD38 with high affinity. The E430G mutation in its Fc domain facilitates the natural process of antibody hexamer formation upon binding to the cell surface, resulting in increased binding of C1q and potentiated complement-dependent cytotoxicity (CDC). Co-crystallization studies were performed to identify the binding interface of HexaBody-CD38 and CD38. HexaBody-CD38-induced CDC, antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), trogocytosis, and apoptosis were assessed using flow cytometry assays using tumour cell lines, and MM patient samples (CDC). CD38 enzymatic activity was measured using fluorescence spectroscopy. Anti-tumour activity of HexaBody-CD38 was assessed in patient-derived xenograft mouse models invivo. HexaBody-CD38 binds a unique epitope on CD38 and induced potent CDC in multiple myeloma (MM), acute myeloid leukaemia (AML), and B-cell non-Hodgkin lymphoma (B-NHL) cells. Anti-tumour activity was confirmed in patient-derived xenograft models invivo. Sensitivity to HexaBody-CD38 correlated with CD38 expression level and was inversely correlated with expression of complement regulatory proteins. Compared to daratumumab, HexaBody-CD38 showed enhanced CDC in cell lines with lower levels of CD38 expression, without increasing lysis of healthy leukocytes. More effective CDC was also confirmed in primary MM cells. Furthermore, HexaBody-CD38 efficiently induced ADCC, ADCP, trogocytosis, and apoptosis after Fc-crosslinking. Moreover, HexaBody-CD38 strongly inhibited CD38 cyclase activity, which is hypothesized to relieve immune suppression in the tumour microenvironment. Based on these preclinical studies, a clinical trial was initiated to assess the clinical safety of HexaBody-CD38 in patients with MM. Genmab.

An armed anti-immunoglobulin light chain nanobody protects mice against influenza A and B infections.

The immune system eliminates pathogen intruders such as viruses and bacteria. To recruit immune effectors to virus-infected cells, we conjugated a small molecule, the influenza neuraminidase inhibitor zanamivir, to a nanobody that recognizes the kappa light chains of mouse immunoglobulins. This adduct was designed to achieve half-life extension of zanamivir through complex formation with the much-larger immunoglobulins in the circulation. The zanamivir moiety targets the adduct to virus-infected cells, whereas the anti-kappa component simultaneously delivers polyclonal immunoglobulins of indeterminate specificity and all isotypes. Activation of antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity promoted elimination of influenza neuraminidase-positive cells. A single dose of the conjugate protected mice against influenza A or B viruses and was effective even when given several days after infection with a lethal dose of virus. In the absence of circulating immunoglobulins, we observed no in vivo protection from the adduct. The type of conjugates described here may thus find application for both anti-influenza prophylaxis and therapy.

A phase 1, first-in-human, open-label, dose escalation and dose expansion study of TST005 in patients with locally advanced or metastatic solid tumors.

2531 Background: TST005 is a novel bi-functional fusion protein combining a high affinity PD-L1 mAb and a differentiated TGF-β trap with improved stability. In pre-clinical study, TST005 showed no antibody-dependent dependent cytotoxicity (ADCC) or complement dependent cytotoxicity (CDC) activity. Methods: This is a Phase 1, dose escalation study with classic 3+3 design to evaluate the safety, tolerability, PK and pharmacodynamic and preliminary anti-tumor activity of TST005 and determine the maximum tolerated dose and/or the Recommended Phase 2 Dose (RP2D). Eligible solid tumor patients who have failed prior standard therapy(ies) and have received no more than one prior immune checkpoint inhibitor (ICI) treatment will be enrolled to receive TST005 intravenous (IV) infusion every 3 weeks until disease progression assessed by the Investigator per RECIST v1.1 and/or immune RECIST, or unacceptable toxicity. Results: The study is ongoing at 4 clinical centers in US and China. As of 31 Jan 2023, 18 eligible subjects have been enrolled into different TST005 dose levels: 2 at dose of 1mg/kg, 4 at 3 mg/kg, 4 at 10 mg/kg, 3 at 20 mg/kg, and 5 at the last dose level of 30 mg/kg. The enrollment is still ongoing. No DLT was observed so far. The most common treatment-emergent adverse events (TEAEs) ( > 10%) included: fatigue (38.9%), rash (22.2%), anemia (16.7%), myalgia (16.7%), and arthralgia, dehydration diarrhea, dry skin, hematuria, hypokalemia, pruritus, lymphocyte count decreased were 11.1%. 7 patients (38.9%) experienced ≥Grade 3 (G3) TEAEs according to CTCAE V5.0, 1 of whom were considered as related to TST005: it was an infusion related reaction (G3), and caused discontinuation of treatment. Two subjects experienced IRRs (G2 and G3 respectively), both at the dose of 3mg/kg cohort. One subject of 30mg/kg dose cohort presented a squamous cell carcinoma of skin, which is known as a classic side effect of TGF-β directed therapies. The subject was discontinued from study and to receive resection. No treatment-related deaths occurred. TST005 demonstrated a nonlinear PK profile between 1 to 20 mg/kg with calculated t1/2 of 4-9 days. ADA was observed in most ADA evaluable subjects, PK at doses ≥ 10mg/kg were not impacted by ADA. At 20mg/kg, the receptor occupancy increased to > 90% immediately after infusion and remain at this level up to C2D1. Start from 1mg/kg, serum TGF-β1 was depleted immediately after dosing, sustained to next dose of TST005. 11 subjects had at least one post treatment tumor assessment per RECIST 1.1. 7 subjects (63.6%) had best overall response of SD. No PR or CR had been observed. Conclusions: TST005 monotherapy demonstrated a good safety and tolerability, nonlinear PK characteristics and significant target engagement in patients with advanced solid tumors. Continue investigation of TST005 as monotherapy or in combination with other therapies are warranted. Clinical trial information: NCT04958434 .

Innenrücktitelbild: Improvement of Antibody Activity by Controlling Its Dynamics Using the Glycan–Lectin Interaction (Angew. Chem. 30/2023)

Antibody dynamics on membranes, such as endocytosis and clustering, are vital in determining antibody functions. Yoshiyuki Manabe, Kazuya Kabayama, Koichi Fukase et al. proposed a new approach to modulate antibody dynamics and its function. In their Communication (e202304779), the antibody was conjugated with galactose-containing N-glycan, and its internalization was suppressed by the interaction with galectin-3, leading to the enhancement of complement-dependent cytotoxic (CDC) activity. The glycan–antibody conjugate might provide an alternative strategy for enhancing antibody activity.

Inside Back Cover: Improvement of Antibody Activity by Controlling Its Dynamics Using the Glycan–Lectin Interaction (Angew. Chem. Int. Ed. 30/2023)

Antibody dynamics on membranes, such as endocytosis and clustering, are vital in determining antibody functions. Yoshiyuki Manabe, Kazuya Kabayama, Koichi Fukase et al. proposed a new approach to modulate antibody dynamics and its function. In their Communication (e202304779), the antibody was conjugated with galactose-containing N-glycan, and its internalization was suppressed by the interaction with galectin-3, leading to the enhancement of complement-dependent cytotoxic (CDC) activity. The glycan–antibody conjugate might provide an alternative strategy for enhancing antibody activity.