Human CD38 Research Articles

Abstract 5316: SM2256: A bispecific conditional CD40 and 4-1BB dual agonist for enhanced solid tumor immune response

Abstract Background: Monoclonal antibodies targeting the co-stimulatory receptors CD137 (4-1BB) and CD40 have displayed encouraging activity against a wide range of solid tumors in preclinical animal models. However, their clinical development as monotherapy has been hindered by dose-related liver toxicity, leading to limited efficacy at safe doses. To address this challenge and bolster tumor-specific immunity by orchestrating the interaction between dendritic cells (DCs) and cytotoxic T cells, we introduce SM2256 - a bispecific conditional CD40 and 4-1BB dual agonist. SM2256 physically bridges DCs and T cells, enhancing T cell priming and reactivation. In preclinical animal studies, SM2256 exhibited both excellent tolerability and potent anti-tumor activity. Methods: SM2256 was engineered by fusing high-affinity, non-ligand-blocking VHH domains targeting 4-1BB and CD40 to a silenced IgG1 Fc backbone. This fusion resulted in a tetravalent bispecific antibody capable of conditionally activating CD40 and 4-1BB upon mutual receptor binding. We assessed the binding specificity and affinity of SM2256 to human CD40 and 4-1BB using ELISA and flow cytometry. The target-dependent activation of CD40 and 4-1BB was confirmed via reporter assays and co-culture systems using primary DCs and T cells. In vivo safety and anti-tumor efficacy were evaluated in a syngeneic transplantation model using the MC38 cancer cell line in B-h41BB/B-hCD40 double humanized mice. Results: SM2256 exhibited sub-nanomolar binding affinity to recombinant human and cynomolgus monkey CD40 and 4-1BB, activating 4-1BB-NFκB-luc and CD40-NFκB-luc reporter cell lines at picomolar concentrations in a strictly target-dependent manner. Furthermore, SM2256 physically facilitated the interaction between DCs and T cells, leading to increased expression of DC co-stimulatory ligands and elevated secretion of cytokines by T cells in mixed lymphocyte cultures. In a syngeneic tumor transplantation model, SM2256 significantly restrained the growth of MC38 tumors in B-h41BB/B-hCD40 double humanized mice. Conclusions: SM2256 is a novel conditional CD40 and 4-1BB dual agonist that demonstrates promising preclinical efficacy against solid tumors while boasting an improved safety profile when compared to existing monoclonal antibodies. Citation Format: Wenjing Song, Simin Yang, Yi Wei, Shihao Lu, Huiqin Geng, Xiaodan Liu, Hong Zhou, Siyao Xie, Xing Zhang, Sheila Zhou, Yanbin Liang. SM2256: A bispecific conditional CD40 and 4-1BB dual agonist for enhanced solid tumor immune response [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 5316.

Abstract 4019: Development of mRNA chimeric antigen receptor T cells targeting MET in aggressive B-cell lymphomas

Abstract Multiple versions of CAR T cells targeting the cell surface protein CD19 are approved by the FDA to treat refractory B-cell malignancies. However, durable remissions range from 60% in B-cell leukemias to 40% in B-cell lymphomas. Major reasons for resistance to CD19-CAR treatment relate to heterogeneous or loss of CD19 expression. In addition, CD19-CAR leads to B-cell depletion which increases the risk for infection. These limiting factors necessitate research into alternative targets for CAR therapy against B-cell lymphomas.Using a large data set from clinical trials, we found that approximately 30-70% of diffuse large B-cell lymphomas (DLBCL) express MET. We hypothesize that these MET-positive B-cell lymphomas can potentially be targeted with chimeric antigen receptor (CAR) T-cells against MET receptor. We constructed a second-generation anti-MET-CAR by fusing the scFv fragment of an anti-MET monoclonal antibody with the human CD28 hinge/transmembrane/cytoplasmic domain and CD3ζ cytoplasmic domain. Stable MET-CAR Jurkat cells showed increased CD69 expression upon stimulation by MET-positive lymphoma cell lines such as Karpas-422 and OCI-LY3. Using primary human T cells, we further demonstrated that the mRNA MET-CAR T-cells mediated cytotoxicity against DLBCL cell lines. Of note, while CD19-CAR T-cells showed only low level of cytotoxicity against the CD19-/MET+ OCI-LY3 cell line, MET-CAR T cell was able to mediate substantial tumor cell lysis.In summary, the preliminary data demonstrate that MET-CAR is capable of mediating cytotoxicity against MET-positive DLBCL. Some cell lines such as OCI-LY3 are negative for CD19 but positive for MET expression, and MET-CAR is capable of mediating cell lysis while CD19-CAR is ineffective. These results suggest that some large B-cell lymphomas negative for CD19, either intrinsic or secondary to loss of CD19 as a result of resistance mechanism, may show MET expression and will likely benefit from MET-targeted immunotherapy. Citation Format: Po-Han Chen, Rianna Raghunandan, Markus Muschen, Samuel G. Katz. Development of mRNA chimeric antigen receptor T cells targeting MET in aggressive B-cell lymphomas [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 4019.

Abstract 2479: Discovery of agonist CD28-specific single domain antibodies from alpaca

Abstract Upon immune activation, in addition to the first signal driven by the TCR-peptide/MHC interactions, the costimulatory signals are indispensable to optimal T-cell activation, the absence of which will trigger naive T cells to an anergic state. The CD28-CD80/CD86 pathway is widely known as the most classical and critical costimulatory signal for the initial activation of T cells. Bispecific T-cell engagers targeting CD3e can activate cytotoxic T-cells and have shown remarkable tumor regressions in clinical trials. However, the absence of a costimulatory signal through CD28 results in insufficient T-cell activation and early exhaustion. Combination of both CD3e and CD28 targeting antibodies offers attractive approach to optimally boost T-cell activity. Development of superagonistic CD28-targeting antibody has been paused after TeGenero‘s TGN1412 Phase 1 trial in 2006 due to life-threatening cytokine release syndrome. Unlike superagonist TGN1412, which activates T cells and induce cytokine storm, tumor targeting antigen and cross-linking dependent CD28 bispecific antibody is supposed to display little or no toxicity. In the present study, we explored Alpaca immunized phage library approach to generate cross-linking dependent agonist CD28 single domain antibody for bispecific antibody development. Alpacas were immunized subsequently with recombinant human CD28 extracellular domain and 293F cells stably expressing human CD28. Serum samples after immunizations showed decent immune response against CD28. At the end of Boost 2 and 3, peripheral blood was collected and phage display libraries were constructed using VHH specific primers. Phage display libraries were panned against recombinant CD28 ECD protein and CHOK1 cells overexpressing CD28. After one round of panning, both protein and cell panning tracks showed robust enrichment in output titer and repeating sequences. Next, 600 clones were randomly picked for screening by the binding to U266B1 cells endogenously expressing CD28. Of the 326 clones showed positive binding to U266B1, 79 unique sequences were identified. Secondary screening by ELISA and FACS using periplasmic extract confirmed 69 unique sequences that bound to both CD28 protein and cells expressing CD28. Seventeen unique sequences were selected for VHH-Fc production. All purified VHH-Fc showed sub-nanomolar affinity by ELISA and bind to primary T cells by flow cytometry. Three VHH-Fc induced IL-2 production in a primary T cells activation assay only when cross-linked and in the presence of CD3 co-stimulation and are suitable for further bispecific T cell engager development. Citation Format: Yunyun Chen, Yannan Ding, Xiaoyan Liu, Qianqian Zhu, Wenfang Xin, Hu Liu, Teddy Yang, Yikai Qiu. Discovery of agonist CD28-specific single domain antibodies from alpaca [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 2479.

Abstract 2381: The bispecific antibody KA-3001, targeting PSMA and CD28, specifically enhances T cell activation within prostate tumors

Abstract Immunotherapy, which involves blocking PD-1 signaling, has revolutionized the treatment paradigm for advanced solid tumors. However, prostate cancer exhibits a low response ratio to anti-PD-1 therapy. In this study, we have developed a bispecific antibody (BsAb), KA-3001, targeting PSMA and human CD28, aiming to enhance T cell activation in the tumor microenvironment. KA-3001, in a regular IgG1 format, features an identical light chain and was designed using our common light chain bispecific antibody discovery platform with knob-into-hole technology. Mutations in the Fc domain were introduced to eliminate ADCC, ADCP, and CDC activity. KA-3001's two Fabs demonstrate high affinity for PSMA and relatively low affinity for CD28. In comparison to REGN5678, KA-3001 exhibits significantly stronger binding to PSMA-expressing prostate tumor cells, along with relatively lower CD28 activation, minimizing toxicity while maintaining anti-tumor efficacy. In PBMC humanized immunodeficient mouse tumor models, KA-3001 effectively suppresses the growth of 22Rv1 tumors with or without PD-1 antagonist antibody. Furthermore, KA-3001 has a half-life of more than five days in the blood of Balb/c mice. Finally, we assessed the developability of this antibody through various treatments such as high concentration, low pH, repeated freezing and thawing, and high temperature. The BsAb demonstrates neither aggregation nor degradation. In conclusion, the BsAb KA-3001, developed using our common light chain antibody discovery platform, stands out as a promising pre-clinical candidate drug for the treatment of prostate cancer. Citation Format: Jiabei Liang, Chen Su, Hao Peng, Feng Hao, Tongtong Liu, Jinying Ning, Guojin Wu. The bispecific antibody KA-3001, targeting PSMA and CD28, specifically enhances T cell activation within prostate tumors [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 2381.

Abstract 2715: Preclinical characterization of SM2248: A dual-action bispecific antibody enhancing immunotherapy for solid tumors

Abstract Background: Innate immune cells, such as macrophages and myeloid-derived suppressor cells (MDSCs), dominate the immune landscape within "cold" solid tumors, which typically exhibit poor responses to immune checkpoint inhibitors (ICIs). The dearth of tumor-infiltrating T cells and the prevailing immunosuppressive microenvironment contribute to this ineffectiveness. To bolster immunotherapy against such tumors, we developed SM2248, a bispecific VHH antibody. SM2248 simultaneously obstructs the CD47-SIRPα phagocytosis checkpoint pathway and conditionally activates CD40 on tumor-infiltrating innate immune cells. CD47/SIRPa blockade enhances macrophage and dendritic cell (DC) phagocytosis and cross-presentation of antigens to cytotoxic T cells. CD40 activation fosters DC licensing, reprograms macrophages, and guides MDSC differentiation towards DCs and macrophages. The combined action of CD47 blockade and CD40 stimulation remodels the tumor microenvironment, fostering T cells infiltration and activation. Methods: SM2248 was developed by fusing a highly selective CD47-blocking VHH module - minimizing binding to human erythrocytes and platelets, with a conditional CD40 agonistic VHH module - selectively activating immune cells upon CD47 engagement, incorporated into an inactivated IgG1 Fc backbone. The specificity and affinity of SM2248 binding to human CD47 and CD40 were assessed via ELISA and flow cytometry assays. CD47 and SIRPα interaction blockade was confirmed through a competitive ligand binding assay. Target-dependent CD40 activation was evaluated via a CD40-NFκB-Luc reporter assay. In vivo anti-tumor efficacy was determined using a syngeneic transplantation model of MC38-hCD47 cancer cells in B-hCD40 humanized mice. Binding to erythrocytes and platelets, compared with magrolimab, was assessed using flow cytometry. Hemolysis toxicity was evaluated through an in vitro erythrocyte lysis assay. Results: SM2248 effectively inhibits cell surface CD47-SIRPα interaction at nanomolar concentrations and activates CD40-NF-κB-luciferase reporters at picomolar concentrations in a target-dependent manner. In contrast to the CD47 monoclonal antibody magrolimab, SM2248 does not bind to human erythrocytes or platelets and does not induce hemolysis. In murine syngeneic tumor models, SM2248 completely halts the growth of MC38-hCD47 tumors in humanized B-hCD40 mice and does not induce dose-dependent hepatotoxicity at doses up to 10 mg/kg. Conclusions: SM2248, a humanized bispecific tetravalent VHH antibody targeting CD47 and CD40, exhibits promising in vivo efficacy and a favorable safety profile in preclinical studies, offering the potential for enhancing immunotherapy in solid tumors. Citation Format: Xiaodan Liu, Hong Zhou, Shihao Lu, Huiqin Geng, Wenjing Song, Siyao Xie, Yi Wei, Xing Zhang, Simin Yang, Sheila Zhou, Yanbin Liang. Preclinical characterization of SM2248: A dual-action bispecific antibody enhancing immunotherapy for solid tumors [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 2715.

Abstract 1859: Diverse CD28-binding IgG and heavy chain-only antibodies for T-cell engager development

Abstract Engagement of the CD28 co-receptor by T-cell engager (TCE) molecules can enhance activation, proliferation, and anti-tumor activities, particularly in immunosuppressive tumor microenvironments. In this study, we present data on a diverse panel of CD28-binding IgG and heavy chain-only (HCAb) antibodies for T-cell co-stimulation. Our diverse panel of CD28-binding antibodies add co-stimulatory building blocks to our TCE repertoire. Using single B cell-screening, we identified fully human IgG and HCAb binders to human and non-human primate CD28 with a high degree of sequence diversity. We selected a subset of antibodies for expression and assessed binding to both human and cynomolgus CD28-expressing cells. These antibodies displayed a wide range of binding avidities in the sub-nanomolar to micromolar range, and epitope binning analysis identified seven epitope communities. Co-stimulatory activity for a subset of molecules was assessed in vitro. Antibodies displayed a wide range of crosslinked T-cell activation with the majority showing no activation independent of crosslinking. Data presented here describe a diverse set of CD28-binding antibodies ready for engineering into co-stimulatory TCEs. Combining these molecules with our TCE platform or other T-cell activating strategies will enable development of novel TCE modalities with co-stimulatory function for diverse tumor targets. Citation Format: Katherine Lam, Shirley Zhi, Lucas Kraft, Elena Vigano, Wei, Cristina Faralla, Esther Odekunle, Kelly Bullock, Erin Marshall, Melissa Cid, Grace Leung, Lindsay DeVorkin, Sherie Duncan. Diverse CD28-binding IgG and heavy chain-only antibodies for T-cell engager development [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 1859.

Abstract 4180: Evaluation of CD38 pharmacodynamics in multiple myeloma using PET with a Ga-68 labelled peptide

Abstract Introduction: Multiple myeloma (MM) is a disease of plasma cells that primarily arises in the bone marrow. CD38 is a receptor expressed uniformly and with high density in MM. Several CD38 targeted therapeutics are in clinic for MM. However, how those therapeutics engage or modulate CD38 is poorly understood particularly in lesions that cannot be assessed with routine blood testing. CD38 specific radiotracers for positron emission tomography (PET) could be helpful for detection of MM and for assessing therapy response early by measuring CD38 pharmacodynamics non-invasively. Here, we report the development of a first-in-class peptide-based PET radiotracer, [68Ga]AJ206, evaluation of its pharmacokinetics (PK), specificity for non-invasive CD38 detection, and its potential to evaluate therapy induced CD38 pharmacodynamics in mouse models of MM. Methods: A bicyclic peptide, AJ206, was synthesized and its binding affinity for CD38 was determined by surface plasmon resonance. AJ206 was labelled with Gallium-68 in high radiochemical yields and purity. In vitro uptake of [68Ga]AJ206 was carried out in four MM cell lines with variable CD38 expression (MOLP8, MM1S, RPMI8226, and U266). PK and biodistribution of [68Ga]AJ206 were evaluated by PET in cell line derived xenografts, in patient derived xenografts (PDXs) and in a disseminated disease model. PET data was corroborated by ex vivo biodistribution studies. [68Ga]AJ206 in vivo specificity for CD38 was confirmed by co-injection of non-radioactive AJ206 (1 mg/kg) and cross-correlative immunohistochemistry (IHC) of matched xenografts. Furthermore, ability of [68Ga]AJ206 to quantify CD38 pharmacodynamics was established by treating PDX models with all-trans retinoic acid (ATRA) and cross validating PET imaging observations with IHC. Results: AJ206 exhibits high affinity (KD,19 nM) for human CD38. In vitro binding assays showed variable [68Ga]AJ206 uptake in MM cells that correlated with receptor density measured by flow cytometry. Dynamic PET-MR imaging revealed high and specific uptake of [68Ga]AJ206 in MOLP8 tumor within 5 min that retained for at least 90 min. In contrast, [68Ga]AJ206 exhibited rapid clearance from normal tissues providing high contrast images at 60 minutes and a high tumor-to-muscle ratio of 27.1±2.7. Tumor uptake was reduced by > 80 % in mice receiving blocking dose, confirming the specificity of the radiotracer. Also, [68Ga]AJ206 could detect CD38 expression in different MM xenografts, PDXs and disseminated disease models which was corroborated by flow cytometry and IHC findings. Moreover, [68Ga]AJ206 successfully quantified the increased CD38 expression in PDXs following ATRA treatment. Conclusion: [68Ga]AJ206 is a CD38 specific high affinity peptide-based PET imaging agent that can be used to non-invasively quantify CD38 pharmacodynamics in MM, with potential applications in other diseases with CD38 involvement. Citation Format: Ajay Kumar Sharma, Kuldeep Gupta, Akhilesh Mishra, Gabriela Lofland, Ian Marsh, Dhiraj Kumar, Gabriel Ghiaur, Philip Imus, Steven P. Rowe, Robert Hobbs, Christian B. Gocke, Sridhar Nimmagadda. Evaluation of CD38 pharmacodynamics in multiple myeloma using PET with a Ga-68 labelled peptide [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 4180.

Abstract 5309: ATOR-4066, a Neo-X-Prime™ bispecific antibody targeting CD40 and CEACAM5, induces tumor localized immune cell activation in preclinical in vivo tumor model

Abstract ATOR-4066 is a preclinical stage bispecific antibody targeting CD40 and CEACAM5, based on Alligator’s novel Neo-X-Prime™ antibody technology platform. ATOR-4066 induces a neoantigen specific T-cell response by simultaneous binding to CD40 on myeloid cells such as antigen presenting cells (APCs) and to CEACAM5 on tumor cells. CEACAM5 is a tumor-associated antigen highly expressed on several cancer indications such as colorectal and gastric cancer, as well as on tumor-derived material. ATOR-4066 treatment results in (1) CEACAM5-conditional CD40-mediated activation of APCs and (2) enhanced uptake of tumor-derived material, leading to cross-presentation of neoantigen and priming of neoantigen-specific T cells, resulting in enhanced tumor cell killing. We have previously shown evidence of a potent anti-tumor effect of ATOR-4066 in vivo, superior to the effects observed with the corresponding CD40 mAb. Moreover, we have demonstrated CEACAM5-dependent activation of CD40-expressing cells in vitro, and an ability to mediate co-localization of CEACAM5-expressing tumor debris and CD40 expressing APCs. In addition, ATOR-4066 was shown to induce CEACAM5-conditional activation of tumor-infiltrating CD40-expressing immune cells in dissociated primary human tumor material from colorectal and gastric cancer patients. Here we present data further elucidating the mode of action of ATOR-4066 in vivo. Following ATOR-4066 treatment, tumors and lymph nodes were isolated from human CD40 transgenic mice bearing MC38 tumors expressing human CEACAM5. Flow cytometry analysis shows an increased number of tumor-infiltrating immune cells in mice treated with ATOR-4066 compared to treatments with CD40 mAb or vehicle. The study also reveals upregulation of co-stimulatory molecules such as CD86 on DCs and macrophages after treatment with ATOR-4066 compared to groups treated with CD40 mAb or vehicle. The effect was localized to the tumor microenvironment and not observed in tumor draining lymph nodes, confirming previous in vitro results demonstrating CEACAM5-conditional immune activation. Moreover, RNA-sequencing of tumor samples displayed distinct transcriptomic alterations following ATOR-4066 treatment vs. CD40 mAb or vehicle treatment in vivo. In contrast, RNA-sequencing of peripheral blood in ATOR-4066 treated mice showed only small transcriptomic differences compared to the vehicle treated group, but distinct from mice treated with a CD40 mAb, further demonstrating the CEACAM5 dependent response of ATOR-4066. In summary, these preclinical data demonstrate that ATOR-4066 activates infiltrating myeloid cells resulting in increases in activated tumor infiltrating T cells, thus creating a pro-inflammatory tumor microenvironment, which strongly supports further development and clinical testing of ATOR-4066. Citation Format: Hampus Andersson, Ida Uddbäck, Mona Celander, Maria Johansson, Lill Ljung, Anneli Nilsson, Amulya Krishna Shetty, David Gomez Jimenez, Mattias Levin, Sara Fritzell, Laura von Schantz, Malin Lindstedt, Karin Hägerbrand, Anette Sundstedt, Peter Ellmark. ATOR-4066, a Neo-X-Prime™ bispecific antibody targeting CD40 and CEACAM5, induces tumor localized immune cell activation in preclinical in vivo tumor model [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 5309.

Abstract 2366: Balancing efficacy and toxicity of a fibroblast activation protein dependent tetravalent CD40 agonist antibody for cancer therapy

Abstract Background: CD40 agonist antibodies have been found to augment tumor antigen presentation and have shown potential as anti-tumor treatments in human clinical trials. The clinical success of CD40 agonist antibodies has been restricted due to their limited efficacy and on-target, off-tumor toxicity. We hypothesized that toxicity associated with CD40 agonist antibodies could be overcome by activating CD40 specifically through tumor-specific antigens. Additionally, limited efficacy can be improved by rational design of CD40 bispecific antibodies (BsAbs). Herein, we present FAPxCD40, a trivalent CD40 agonist BsAb targeting fibroblast activation protein (FAP) possessing an optimized therapeutic window. Method: We generated a series of FAPxCD40 bispecific antibodies with 2, 4, and 6 CD40 valences by using a high-affinity anti-FAP antibody and a crosslink-dependent CD40 agonist VHH antibody. These BsAbs were evaluated using multiple immune cell functional assays, including assays for dendritic cell (DC) maturation, B cell maturation, and CMV-reactive T cell recall. The in vivo therapeutic window of the FAPxCD40 bispecifics was compared in CD40 humanized mice with subcutaneously transplanted FAP-positive MC38 tumor xenografts. Results: We developed FAPxCD40 BsAbs with varying valences, including bivalent FAPxCD40-2, tetravalent FAPxCD40-4, and hexavalent FAPxCD40-6. FAPxCD40-2 showed strict FAP-dependent CD40 agonist activity in both DC and B cell maturation assays, while its CD40 agonist activity upon FAP-crosslinking was modest. FAPxCD40-4 exhibited efficient CD40 agonist activity upon FAP-crosslinking, but however, it also exhibited some undesired FAP-independent CD40 agonist activity. FAPxCD40-6 efficiently clustered CD40 but marginally benefited from FAP binding, making it unsuitable as a choice. In the humanized CD40 mice model, FAPxCD40-2 effectively eliminated systemic toxicity at all tested doses. Its antitumor activity, however, is modest with TGI (tumor growth inhibition) rate of 32.8 % at a dose of 6.96 mpk. Further escalation of the FAPxCD40-2 dosage to 13.92 mpk did not result in enhanced antitumor activity with TGI rate of 46.9 %, indicating that its CD40 agonist activity may have reached a plateau. In contrast, FAPxCD40-4 broke this plateau and induce a promising antitumor response at a dose of 1.3 mpk, resulting in a 92% TGI rate. Furthermore, no liver enzyme upregulation or platelet count decrease was observed under these conditions, indicating an ideal therapeutic window. In addition, during nonclinical toxicology studies conducted on cynomolgus monkeys, it was found that doses of FAPxCD40-4 up to 99 mg/kg administered weekly for a total of four doses were well-tolerated. Conclusion: Our study demonstrates that FAPxCD40-4, a tetravalent FAPxCD40 BsAb, exhibits efficient CD40 agonist activity with an optimized therapeutic window. Citation Format: Simeng Chen, Yuan Lin, Xiaoru Zhou, Xing Sun, Changyong Yang, Cheng Liao. Balancing efficacy and toxicity of a fibroblast activation protein dependent tetravalent CD40 agonist antibody for cancer therapy [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 2366.

Abstract 5310: KK2269, an epithelial cell adhesion molecule-targeted CD40 agonist, demonstrates antitumor effects in combination with standard therapies for NSCLC

Abstract CD40 is a key molecule expressed on antigen presenting cells (APCs), whose signaling activates APCs and generates antitumor immune responses. Although CD40 agonists have been investigated in clinical trials, systemic toxicities have limited their full potential in providing adequate antitumor effects. To overcome this limitation, we developed KK2269, a bispecific antibody, using REGULGENT™ technology. KK2269 binds to CD40 and tumor-expressed epithelial cell adhesion molecule (EpCAM) to allow activation of CD40+ APCs only at EpCAM+ tumor sites, thus avoiding systemic toxicity. EpCAM is overexpressed in many types of epithelial cancers, including non-small cell lung cancer (NSCLC). KK2269 exerts synergistic antitumor activity and tumor-specific immune responses in combination with docetaxel, a common chemotherapy for NSCLC, in an EpCAM-expressing tumor mouse model. Hence, we aimed to evaluate KK2269 for the treatment of NSCLC. Docetaxel is used as a combination therapy with ramucirumab, an anti-VEGF receptor 2 (VEGFR2) antibody, for previously treated advanced NSCLC. In addition, many clinical studies are evaluating the add-on effects of PD-1/PD-L1 blockade combined with standard chemotherapies (including docetaxel) in NSCLC, which may become the standard of care for advanced NSCLC in the future. Therefore, we investigated the antitumor effect of KK2269 in combination with docetaxel + anti-mouse VEGFR2 (study 1) and with docetaxel + anti-mouse PD-1 (study 2) using a mouse EpCAM-expressing B16F10 tumor-bearing human CD40 transgenic mouse model. The prolongation of TTP5X (the day on which the tumor volume is observed to be ≥5-fold of that observed on day 0) was evaluated. In study 1, the median TTP5X (95% confidence interval [CI]) with the control, docetaxel + anti-VEGFR2, and triple combination (KK2269, docetaxel, anti-VEGFR2) was 10.0 days (7.0, 10.0), 26.0 days (17.0, 28.0), and 52.0 days (42.0, not calculable), respectively. The TTP5X was significantly prolonged with the triple combination compared with the control (p=0.000007, log-rank test) and docetaxel + anti-VEGFR2 (p=0.000004, log-rank test). In study 2, the median TTP5X (95% CI) was 7.0 days (not calculable), 9.0 days (6.0, 11.0), 16.0 days (7.0, 18.0), and 26.5 days (7.0, 32.0) with the control, KK2269, docetaxel + anti-PD-1, and triple combination (KK2269, docetaxel, anti-PD-1), respectively. TTP5X was significantly prolonged with the triple combination compared with the control, KK2269, and docetaxel + anti-PD-1 (p<0.0001, p=0.0003, and p=0.0023, respectively, log-rank test). Thus, a significant antitumor effect was demonstrated when KK2269 was added to the standard treatment of NSCLC (docetaxel + anti-VEGFR2 antibody) and to docetaxel + anti-PD-1 antibody. Our findings strongly suggest that KK2269 provides improved treatment options for patients with NSCLC. Citation Format: Yuta Tezuka, Kyoko Kawasaki, Yoshiki Sumitomo, Masato Saito, Akari Yao, Munetoshi Ando. KK2269, an epithelial cell adhesion molecule-targeted CD40 agonist, demonstrates antitumor effects in combination with standard therapies for NSCLC [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 5310.

Abstract 5296: Enhancing the strength and durability of vaccine-induced anti-tumor immunity with CD27 agonism of CD4+ T cells

Abstract Despite encouraging early phase clinical trials, decades of research have yet to yield effective cancer vaccine immunotherapies. To determine potential markers for success, we performed a follow-up study of a HER2-pulsed dendritic cell cancer vaccine Phase I trial performed in advanced HER2+ cancer patients. Surprisingly, we found that all treated patients were alive at over 18 years post-treatment. These patients still possessed significant HER2-specific memory T cell responses, typified by CD27 expression. The expansion of HER2-specific CD27+ memory T cells was also observed in patients from a separate clinical trial, who received a HER2-expressing viral vaccine. To validate these clinical responses, we vaccinated human CD27 transgenic mice with a HER2 viral vector again observing HER2-specific CD27+ memory T cells, suggesting the significance of this axis in eliciting and maintaining effective vaccine-specific memory T cell responses. We hypothesized that CD27 expression was not just a marker of memory T cells, but represented a critical activation pathway during memory formation. To determine the potential impact of CD27 agonism in vaccination, we combined HER2 vaccination with an anti-CD27 agonist antibody (Varlilumab). The combination treatment elicited a robust increase in HER2-specific CD4+ memory T cell responses that was maintained for at least 300 days post-vaccination. Using therapeutic HER2 vaccination in combination with anti-CD27 of HER2+ tumor bearing mice, we show significantly increased anti-tumor efficacy and further enhancement in combination with PD1 inhibition. The anti-tumor response was triggered by anti-CD27 antibody during the vaccine priming phase, which enhanced HER2-specific CD4+ T cells. Critically, we found that HER2 specific CD4+ T cell responses allowed for anti-tumor responses that persisted after CD8+ T cell depletion, indicating a direct role for antigen-specific CD4+ T cells independent of CD8+ T cells. Collectively, our results support a central role for antigen-specific CD27+ CD4+ T cells in cancer vaccination. These data support the addition of CD27 agonism to improve the therapeutic index of cancer vaccines and potentially enhance responses to immune checkpoint blockade in refractory cancers. Citation Format: Bin-Jin Hwang, Erika Crosby, Timothy Trotter, Li-Chung Tsao, Tao Wang, Congxiao Liu, Xiao Yang, Gangjun Lei, Junping Wei, Xingru Ma, Bushanqing Liu, Amy Hobeika, Michael Morse, Tibor Keler, Li-Zhen He, Herbert Kim Lyerly, Zachary Hartman. Enhancing the strength and durability of vaccine-induced anti-tumor immunity with CD27 agonism of CD4+ T cells [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 5296.

Abstract 2379: The bispecific antibody KA-3007 against B7H3 and CD28 enhances T cell activation in solid tumors

Abstract Immunotherapy, revolutionizing the treatment of advanced solid tumors by blocking PD1 signaling, faces challenges as most cancers remain unresponsive to anti-PD-1 therapy. CD28, a key immune co-stimulatory receptor on T cells, often lacks ligands expressed on tumor cells. B7H3 is highly expressed in various solid tumors. In this study, we developed a bispecific antibody (BsAb) named KA-3007, targeting B7H3 and human CD28 to activate T cells in the tumor microenvironment. KA-3007, featuring an identical light chain, was developed using our common light chain bispecific antibody discovery platform with knob-into-hole technology. This BsAb is in regular IgG1 format with mutations in the Fc domain to eliminate ADCC, ADCP, and CDC activity. Its two Fabs bind to B7H3 with high affinity and CD28 with relatively low affinity. Co-culturing T cells with tumor cells expressing B7H3 enhances T cell activation. In PBMC humanized immunodeficient mouse tumor models, KA-3007 effectively suppresses the growth of NCI-H292 tumors, with or without a PD1 antagonist antibody. Furthermore, this antibody exhibits a half-life of more than five days in the blood of Balb/c mice. Finally, we assessed the developability of KA-3007 with different treatments such as high concentration, low pH, repeated freezing and thawing, and high temperature, and it shows neither aggregation nor degradation. In conclusion, the BsAb KA-3007, developed with our common light chain antibody discovery platform, emerges as a promising pre-clinical candidate drug for the treatment of solid cancers. Citation Format: Guojin Wu, Zhengcheng Guo, Hao Peng, Feng Hao, Feng He, Jinying Ning. The bispecific antibody KA-3007 against B7H3 and CD28 enhances T cell activation in solid tumors [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 2379.

ImmunoPET/CT imaging of clear cell renal cell carcinoma with [18F]RCCB6: a first-in-human study.

The cluster of differentiation (CD70) is a potential biomarker of clear cell renal cell carcinoma (ccRCC). This study aims to develop CD70-targeted immuno-positron emission tomography/computed tomography (immunoPET/CT) imaging tracers and explore the diagnostic value in preclinical studies and the potential value in detecting metastases in ccRCC patients. Four novel CD70-specific single-domain antibodies (sdAbs) were produced and labelled with 18F by the aluminium fluoride restrained complexing agent (AlF-RESCA) method to develop radiotracers. The visualisation properties of the tracers were evaluated in a subcutaneous ccRCC patient-derived xenograft (PDX) model. In a registered prospective clinical trial (NCT06148220), six patients with pathologically confirmed RCC were included and underwent immunoPET/CT examination exploiting one of the developed tracers (i.e., [18F]RCCB6). We engineered four sdAbs (His-tagged RCCB3 and RCCB6, His-tag-free RB3 and RB6) specifically targeting recombinant human CD70 without cross-reactivity to murine CD70. ImmunoPET/CT imaging with [18F]RCCB3 and [18F]RCCB6 demonstrated a high tumour-to-background ratio in a subcutaneous ccRCC PDX model, with the latter showing better diagnostic potential supported by higher tumour uptake and lower bone accumulation. In comparison, [18F]RB6, developed by sequence optimisation, has significantly lower kidney accumulation than that of [18F]RCCB6. In a pilot translational study, [18F]RCCB6 immunoPET/CT displayed ccRCC metastases in multiple patients and demonstrated improved imaging contrast and diagnostic value than 18F-FDG PET/CT in a patient with ccRCC. The work successfully developed a series of CD70-targeted immunoPET/CT imaging tracers. Of them, [18F]RCCB6 clearly and specifically identified inoculated ccRCCs in preclinical studies. Clinical translation of [18F]RCCB6 suggests potential for identifying recurrence and/or metastasis in ccRCC patients.

Discovery and preclinical development of a therapeutically active nanobody-based chimeric antigen receptor targeting human CD22

Chimeric antigen receptor (CAR-) T cell therapies targeting B-cell restricted antigens CD19, CD20, or CD22 can produce potent clinical responses for some B-cell malignancies, but relapse remains common. Camelid single domain antibodies (sdAbs or nanobodies) are smaller, simpler, and easier to recombine than single-chain variable fragments (scFvs) used in most CARs, but fewer sdAb-CARs have been reported. Thus, we sought to identify a therapeutically active sdAb-CAR targeting human CD22. Immunization of an adult Llama glama with CD22 protein, sdAb-cDNA library construction, and phage panning yielded >20 sdAbs with diverse epitope and binding properties. Expressing CD22-sdAb-CAR in Jurkat cells drove varying CD22-specific reactivity not correlated with antibody affinity. Changing CD28 to CD8-transmembrane design increased CAR persistence and expression in vitro. CD22-sdAb-CAR candidates showed similar CD22-dependent CAR-T expansion in vitro, though only membrane-proximal epitope targeting CD22-sdAb-CARs activated direct cytolytic killing and extended survival in a lymphoma xenograft model. Based on enhanced survival in blinded xenograft studies a lead CD22sdCAR-T was selected; achieving comparable complete responses to a benchmark short-linker m971-scFv CAR-T in high-dose experiments. Finally, immunohistochemistry and flow cytometry confirm tissue and cellular level specificity of the lead CD22-sdAb. This presents a complete report on pre-clinical development of a novel CD22sdCAR therapeutic.

Immune profiling of patients with extranodal natural killer/T cell lymphoma treated with daratumumab

Natural killer/T cell lymphoma (NKTCL) is a highly aggressive, heterogeneous non-Hodgkin lymphoma resulting from malignant proliferation of cytotoxic natural killer (NK) or T cells. Previous studies demonstrated variable expression of CD38 on NKTCL tumors. Daratumumab, a human IgGκ monoclonal antibody targeting CD38 with a direct on-tumor and immunomodulatory mechanism of action, was hypothesized to be a novel therapeutic option for patients with relapsed or refractory (R/R) NKTCL. In the phase 2 NKT2001 study (ClinicalTrials.gov Identifier: NCT02927925) assessing the safety and efficacy of daratumumab, a suboptimal overall response rate was seen in R/R NKTCL patients. One patient, whose tumors did not express CD38, responded to treatment, suggesting that the immunomodulatory activities of daratumumab may be sufficient to confer clinical benefit. To understand the suboptimal response rate and short duration of response, we investigated the immune profile of NKTCL patients from NKT2001 in the context of daratumumab anti-tumor activity. Tumor tissue and whole blood were, respectively, analyzed for CD38 expression and patient immune landscapes, which were assessed via cytometry by time-of-flight (CyTOF), multiparameter flow cytometry (MPFC), clonal sequencing, and plasma Epstein-Barr virus (EBV)-DNA level measurements. Changes observed in the immune profiles of NKTCL patients from NKT2001, including differences in B and T cell populations between responders and nonresponders, suggest that modulation of the immune environment is crucial for daratumumab anti-tumor activities in NKTCL. In conclusion, these findings highlight that the clinical benefit of daratumumab in NKTCL may be enriched by B/T cell–related biomarkers.

Abstract PR06: CD40 agonist mitazalimab in combination with mFOLFIRINOX in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC): Interim efficacy results of the OPTIMIZE-1 phase 1b/2 study

Abstract Mitazalimab is a human CD40 agonistic IgG1antibody. Targeting CD40 kickstarts the cancer immunity cycle by licensing dendritic cells leading to tumor specific T cell priming and activation. Furthermore, in PDAC CD40 agonists on myeloid cells promote degradation of the desmoplastic tumor stroma, improving influx of T cells and sensitizing the tumor to chemotherapeutic agents. OPTIMIZE-1 (NCT04888312) is a Phase 1b/2, open label, multicenter study designed to evaluate safety, tolerability, and efficacy of mitazalimab in combination with mFOLFIRINOX (Oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, irinotecan 150 mg/m2, 5-FU 2.4 g/m2) in patients with previously untreated mPDAC. In the first part of the study (phase 1b), 900 µg/kg mitazalimab was selected as the recommended phase 2 dose (RP2D). In the first 21-day treatment cycle, mitazalimab is administered IV at RP2D on day 1 and 10 and mFOLFIRINOX infusion started on day 8. In subsequent cycles, treatment follows a 14-day cycle where mitazalimab is administered 2 days after mFOLFIRINOX. The primary endpoint of this ongoing study is overall response rate (ORR) per RECIST v1.1. Secondary and exploratory endpoints include duration of response, progression free and overall survival, safety, PK and PD biomarker assessments. As of May 24, 2023, study enrolment was complete, 65 patients were treated with mFOLFIRINOX and mitazalimab 900 µg/kg (RP2D). Interim efficacy analysis comprised of 57 evaluable patients. Median follow up was 6.5 months and median exposure to treatment was 5 months. 28 patients (49%) remain on treatment, 18 (32%) continued treatment beyond 6 months, the longest being 17 months (ongoing). ORR was 43.9% (25 patients with partial response), an additional 19 patients achieved stable disease, resulting in a 77.2% disease control rate. Median time to response was 2.2 months and median duration of response was 8.7 months. The most common grade (Gr) ≥3 TEAEs were neutropenia (21.5%), anemia (12.3%), thrombocytopenia (12.3%) and hypokalemia (12.3%). Mitazalimab related Gr >3 AEs occurring in more than one patient were fatigue in 3 (4.6%) patients, increased ALT in 3 (4.6%) patients, diarrhea in 2 (3.1%) patients, asthenia in 2 (3.1%) patients, increased AST in 2 (3.1%) patients, and hypokalemia in 2 (3.1%) patients. 25 patients (38.5%) experienced infusion reactions (all Gr 1-2, managed with symptomatic treatment, none amounting to cytokine release syndrome) and 7 (10.8%) patients discontinued treatment due to TEAEs (pneumonia, gastric obstruction, neuropathy, bacteremia, ileal obstruction, stroke, skin reaction). In this ongoing phase 1b/2 trial, 900 µg/kg mitazalimab has shown no evidence of additive toxicity when administered in combination with mFOLFIRINOX, allowing extended treatment until progression. Interim efficacy results demonstrate encouraging antitumor activity in mPDAC with good durability of responses, meriting continued development. Citation Format: Jean-Luc Van Laethem, Karen P. Geboes, Philippe A. Cassier, Ivan Borbath, Aurélien Lambert, Emmanuel Mitry, Hans Prenen, Jean-Frédéric Blanc, Lorenzo Pilla, Mercedes Rodriguez Garrote, Roberto A. Pazo Cid, Inmaculada Gallego, Jaime Feliú, Karin Nordbladh, Peter Ellmark, Malin Carlsson, Yago Pico de Coaña, Sumeet V. Ambarkhane, Teresa Macarulla. CD40 agonist mitazalimab in combination with mFOLFIRINOX in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC): Interim efficacy results of the OPTIMIZE-1 phase 1b/2 study [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR06.

Impaired intratumoral dendritic cell function and potential predictive value of dendritic cell markers for metastasis in malignant salivary gland tumors.

The differentiation between primary and metastatic salivary gland neoplasms (SGNs) helps in determining appropriate management strategies, including the need for additional diagnostic tests, surveillance, or aggressive treatment. The purpose of this study was to identify and quantify the immature and mature dendritic cells (DCs) in metastatic and no metastatic SGNs and determine its association with clinicopathological findings. Cross-sectional, observational, and descriptive study that includes 33 malignant salivary gland neoplasms [MSGN (6, 18.1% metastatic)], and 22 pleomorphic adenomas (PA), as a control group. Clinical and histopathological characteristics were obtained. Immunohistochemistry for human leukocyte antigen D-related (HLA-DR), CD1a, CD83, and Ki-67 proteins was done. Positive intra- and peritumoral DCs were counted. Individuals with MSGN had a lower density of intratumoral HLA-DR+ cells than those with PA (p=0.001), Ki-67 immunostaining was significantly higher in MSGN than in PA (6% vs. 1.4%, p<0.001). Metastatic MSGN showed less intratumoral CD1a+ than non-metastatic (3.2 vs. 165.1, p=0.001). No differences in intra- and peritumoral CD83+ cells were found between benign and malignant SGN. These results suggest that the immune-protective function of intratumoral DCs is compromised in MSGNs. DCs markers may represent useful prediction tools for metastases in salivary gland malignancies, with crucial implications in the implementation of appropriate disease management strategies.

M9657 Is a Bispecific Tumor-Targeted Anti-CD137 Agonist That Induces MSLN-Dependent Antitumor Immunity without Liver Inflammation.

The costimulatory receptor CD137 (also known as TNFRSF9 or 4-1BB) sustains effective cytotoxic T-cell responses. Agonistic anti-CD137 cancer immunotherapies are being investigated in clinical trials. Development of the first-generation CD137-agonist monotherapies utomilumab and urelumab was unsuccessful due to low antitumor efficacy mediated by the epitope recognized on CD137 or hepatotoxicity mediated by Fcγ receptors (FcγR) ligand-dependent CD137 activation, respectively. M9657 was engineered as a tetravalent bispecific antibody (mAb2) in a human IgG1 backbone with LALA mutations to reduce binding to FCγRs. Here, we report that M9657 selectively binds to mesothelin (MSLN) and CD137 with similar affinity in humans and cynomolgus monkeys. In a cellular functional assay, M9657 enhanced CD8+ T cell-mediated cytotoxicity and cytokine release in the presence of tumor cells, which was dependent on both MSLN expression and T-cell receptor/CD3 activation. Both FS122m, a murine surrogate with the same protein structure as M9657, and chimeric M9657, a modified M9657 antibody with the Fab portion replaced with an anti-murine MSLN motif, demonstrated in vivo antitumor efficacy against various tumors in wild-type and human CD137 knock-in mice, and this was accompanied by activated CD8+ T-cell infiltration in the tumor microenvironment. The antitumor immunity of M9657 and FS122m depended on MSLN expression density and the mAb2 structure. Compared with 3H3, a murine surrogate of urelumab, FS122m and chimeric M9657 displayed significantly lower on-target/off-tumor toxicity. Taken together, M9657 exhibits a promising profile for development as a tumor-targeting immune agonist with potent anticancer activity without systemic immune activation and associated hepatotoxicity.

Abstract B034: CD27 is a new promising T cell co-stimulatory target for cancer immunotherapy

Abstract Members of the tumor necrosis factor receptor superfamily (TNFRSF) are key co-stimulators of T cells. CD27, a member of the TNFRSF, is expressed only on the surface of lymphocytes, including naive and activated CD4+ and CD8+ T cells as well as NK cells. It enhances T cell activation, proliferation, and differentiation of effector and memory T cells after stimulation with its ligand, CD70. The costimulatory signal of CD27 is mediated via the NFkB pathway but also via the phosphatidylinositol 3 kinase and the protein kinase B pathways. CD27 signaling also influences the innate immune response via direct activation of NK cells and subsequent secretion of interferon-gamma (IFNg). Several published preclinical studies demonstrated that anti-CD27 agonistic monoclonal antibodies can promote T-cell activation and antitumor immunity making CD27 an attractive cancer immunotherapy target. Here we describe the characterization, preclinical development, and selection of our anti-CD27 fully human monoclonal antibody (mAb) lead candidate. We selected this candidate from a library of 147 anti-CD27 mAbs generated after immunization of humanized Trianni® mice with soluble human CD27 extracellular domain (hCD27-ECD). Anti-CD27 mAbs were tested in an accelerated stability study and showed excellent stability parameters for up to 7 days at 4 and 37°C in commonly used formulation buffers. The selected agonist anti-CD27 mAb demonstrated high affinity binding to both human and cynomolgus monkey CD27 and not to mouse CD27. It also demonstrated high specificity against CD27 with no cross-reactivity detected against other members of the TNFRSF. This lead candidate did not block the binding of CD27 natural ligand, CD70 and induced strong NFkB-mediated CD27 signaling in the absence or presence of cross-linking by Fc gamma receptors or secondary cross-linking antibodies. Moreover, this anti-CD27 mAb mediated NFkB activation is significantly potentiated by the addition of a sub-optimal amount of soluble CD70. The anti-CD27 lead mAb induced T cell proliferation and secretion of pro-inflammatory cytokines only in the presence of sub-optimal TCR stimulation in vitro using primary human T cells. It also activated NK cells demonstrated by CD69 expression induction. The anti-CD27 mAb lead candidate showed extended serum half-life in hCD27-KI mice. It also demonstrated a significant antitumor effect as a single agent in human CD27-Knockin mice (hCD27-KI) subcutaneously implanted with MC38 or in NOD-SCID mice subcutaneously implanted with Raji. These preclinical results establish that the selected anti-CD27 mAb is a promising drug candidate and we are actively pursuing its development. Citation Format: Thierry Guillaudeux, Yulia Ovechkina, Kurt Lustig, Shawn Iadonato. CD27 is a new promising T cell co-stimulatory target for cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr B034.

Subgroup Analyses of Progression-Free Survival from the Phase 3 Octans and Alcyone Studies in Transplant-Ineligible Patients with Newly Diagnosed Multiple Myeloma Treated with Bortezomib, Melphalan, and Prednisone with or without Daratumumab

Introduction:Daratumumab, a human IgGκ monoclonal antibody targeting CD38, has shown clinical efficacy in combination with standard-of-care regimens in patients with newly diagnosed multiple myeloma (NDMM). The addition of daratumumab to bortezomib, melphalan, and prednisone (D-VMP) significantly improved clinical outcomes vs bortezomib, melphalan, and prednisone (VMP) in phase 3 studies in Asian patients (OCTANS) and a global population (ALCYONE) with transplant-ineligible (TIE) NDMM. Here, we present subgroup analyses of progression-free survival (PFS) by measurable residual disease (MRD) and cytogenetic risk status from OCTANS and ALCYONE. Methods: Eligible patients from OCTANS (NCT03217812) and ALCYONE (NCT02195479) had a diagnosis of NDMM and were TIE due to age or comorbidities. Patients were randomized to receive up to nine 42-day cycles of VMP (bortezomib 1.3 mg/m 2 SC twice weekly in Cycle 1 and weekly in Cycles 2-9, and melphalan 9 mg/m 2 and prednisone 60 mg/m 2 orally on Days 1-4 of each cycle) or D-VMP (VMP + daratumumab 16 mg/kg IV weekly in Cycle 1, every 3 wk in Cycles 2-9, and every 4 wk thereafter until disease progression or unacceptable toxicity). MRD negativity (10 -5) was assessed by multi-parameter flow cytometry in OCTANS and next-generation sequencing in ALCYONE. Cytogenetic risk was assessed by FISH or karyotype testing. Results:A total of 220 Asian patients were randomized (D-VMP, n = 146; VMP, n = 74) in OCTANS, and 706 global patients were randomized (D-VMP, n = 350; VMP, n = 356) in ALCYONE. With a median follow-up of 41.2 mo (range, 0.0-59.9) in OCTANS, the median PFS was 38.7 mo with D-VMP and 19.2 mo with VMP (HR, 0.35; 95% CI, 0.23-0.52; P &amp;lt;0.0001). With a median follow-up of 40.1 mo (range, 0.0-52.1) in ALCYONE, the median PFS was 36.4 mo with D-VMP and 19.3 mo with VMP (HR, 0.42; 95% CI, 0.34-0.51; P &amp;lt;0.0001). The rates of overall and sustained MRD negativity were higher with D-VMP vs VMP. In OCTANS, the MRD-negativity rate was 40.4% with D-VMP vs 10.8% with VMP ( P &amp;lt;0.0001), and more patients in the D-VMP group had sustained MRD negativity lasting ≥12 mo (24.7% vs 1.4%; P &amp;lt;0.0001) and ≥18 mo (15.1% vs 1.4%; P = 0.0008). Similarly, in ALCYONE, the MRD-negativity rate was 28.3% with D-VMP vs 7.0% with VMP ( P &amp;lt;0.0001), with more patients in the D-VMP group having sustained MRD negativity lasting ≥12 mo (14.0% vs 2.8%; P &amp;lt;0.0001) and ≥18 mo (8.9% vs 1.7%: P &amp;lt;0.0001). In both studies, longer PFS was observed for patients who achieved MRD negativity vs those who did not within each treatment group; however, the PFS benefit observed for D-VMP vs VMP was maintained irrespective of MRD status ( Figure). In multivariate analyses, achievement of sustained MRD negativity lasting ≥12 mo was associated with longer PFS vs MRD negativity &amp;lt;12 mo in both OCTANS (HR, 0.23; 95% CI, 0.09-0.62; P = 0.004) and ALCYONE (HR, 0.13; 95% CI, 0.06-0.32; P &amp;lt;0.0001). No other factors showed a significant association with PFS in the multivariate analysis for OCTANS; other factors associated with longer PFS in ALCYONE included age &amp;lt;75 vs ≥75 y (HR, 0.38; 95% CI, 0.20-0.75; P = 0.005) and ISS disease stage I vs II (HR, 0.20; 95% CI, 0.05-0.86; P = 0.03). Data from OCTANS and ALCYONE were pooled for an analysis of PFS by cytogenetic risk subgroup (D-VMP, n = 496; VMP, n = 430). D-VMP prolonged median PFS vs VMP in patients with standard cytogenetic risk (not estimable vs 18.9 mo; HR, 0.33; 95% CI, 0.26-0.42) and high cytogenetic risk (25.6 vs 18.9 mo; HR, 0.54; 95% CI, 0.41-0.71), defined by the presence of t(4;14), t(14;16), del(17p), t(14;20), gain(1q21), and/or amp(1q21). Median PFS was also longer with D-VMP vs VMP for patients with gain and/or amp(1q21) (31.9 vs 18.9 mo; HR, 0.45; 95% CI, 0.32-0.63), 1 high-risk cytogenetic abnormality (HRCA; 24.4 vs 19.3 mo; HR, 0.62; 95% CI, 0.44-0.86), and ≥2 HRCA (28.2 vs 17.5 mo; HR, 0.36; 95% CI, 0.20-0.63). Conclusions:In this subgroup analysis of OCTANS and ALCYONE, the prolonged PFS observed with D-VMP vs VMP in the overall study populations was maintained irrespective of the achievement of MRD negativity or the presence of high cytogenetic risk. In addition, the rates of MRD negativity and sustained MRD negativity were higher with D-VMP vs VMP, and achievement of these deep responses translated into longer PFS, consistent with a prior pooled analysis of the MAIA and ALCYONE studies. These results further support the use of daratumumab in combination with VMP in both Asian and global patients with TIE NDMM.