Bispecific antibodies targeting CD40 and tumor-associated antigens promote cross-priming of T cells resulting in an antitumor response superior to monospecific antibodies

BACKGROUND

Indications with poor T-cell infiltration or deficiencies in T-cell priming and associated unresponsiveness to established immunotherapies represent an unmet medical need in oncology. CD40-targeting therapies designed to enhance antigen presentation, generate new tumor-specific T cells, and activate tumor-infiltrating myeloid cells to remodel the tumor microenvironment, represent a promising opportunity to meet this need. In this study, we present the first in vivo data supporting a role for tumor-associated antigen (TAA)-mediated uptake and cross-presentation of tumor antigens to enhance tumor-specific T-cell priming using CD40×TAA bispecific antibodies, a concept we named Neo-X-Prime.

METHODS

Bispecific antibodies targeting CD40 and either of two cell-surface expressed TAA, carcinoembryonic antigen-related cell adhesion molecule 5 (CEA) or epithelial cell adhesion molecule (EpCAM), were developed in a tetravalent format. TAA-conditional CD40 agonism, activation of tumor-infiltrating immune cells, antitumor efficacy and the role of delivery of tumor-derived material such as extracellular vesicles, tumor debris and exosomes by the CD40×TAA bispecific antibodies were demonstrated in vitro using primary human and murine cells and in vivo using human CD40 transgenic mice with different tumor models.

RESULTS

The results showed that the CD40×TAA bispecific antibodies induced TAA-conditional CD40 activation both in vitro and in vivo. Further, it was demonstrated in vitro that they induced clustering of tumor debris and CD40-expressing cells in a dose-dependent manner and superior T-cell priming when added to dendritic cells (DC), ovalbumin (OVA)-specific T cells and OVA-containing tumor debris or exosomes. The antitumor activity of the Neo-X-Prime bispecific antibodies was demonstrated to be significantly superior to the monospecific CD40 antibody, and the resulting T-cell dependent antitumor immunity was directed to tumor antigens other than the TAA used for targeting (EpCAM).

CONCLUSIONS

The data presented herein support the hypothesis that CD40×TAA bispecific antibodies can engage tumor-derived vesicles containing tumor neoantigens to myeloid cells such as DCs resulting in an improved DC-mediated cross-priming of tumor-specific CD8⁺ T cells. Thus, this principle may offer therapeutics strategies to enhance tumor-specific T-cell immunity and associated clinical benefit in indications characterized by poor T-cell infiltration or deficiencies in T-cell priming.

Abstract 4155: Mitazalimab, a potent CD40 agonist in combination with chemotherapy redirects and activates tumor infiltrating myeloid cells

Mitazalimab is a human CD40 agonistic antibody developed for immunotherapy of cancer. Activation of CD40, expressed on myeloid cells, such as dendritic cells and tumor infiltrating macrophages, leads to improved T cell priming and initiation of T cell-dependent anti-tumor responses. Mitazalimab is a FcγR crosslinking-dependent IgG1 antibody, with potential for high efficacy and manageable safety profile.

Immunologically cold and immune-excluded tumors, such as pancreatic cancer, are defined by low infiltration of immune cells as well as low expression and release of neoantigens. In pancreatic cancer, effector CD8+ T cells are excluded from the tumor by the desmoplastic tumor stroma, which surrounds the tumor and hosts immunosuppressive macrophages that dampen the immune response in the tumor microenvironment. By activating and re-directing tumor infiltrating myeloid cells, CD40 agonists such as mitazalimab, have the potential to augment the response to chemotherapy and spark an effective anti-tumor response by i) priming T cells reactive to the tumor neoantigens released by the chemotherapy, and ii) inducing degradation of the stroma surrounding the tumor thereby enhancing the efficacy of chemotherapy.

The ability of mitazalimab to augment the response to chemotherapy was demonstrated in mice, transgenic for human CD40 (hCD40tg), inoculated with the syngeneic tumor cell line MB49. Mitazalimab, administered repeatedly together with FOLFIRINOX (oxaliplatin, irinotecan, 5-fluorouracil and folinic acid), synergized effectively with chemotherapy, inducing long-term survival. The combined treatment improved activation of antigen presenting cells in the circulation, intratumoral T cell responses as well as reduced the amount of intratumoral immunosuppressive M2 macrophages. By converting the MB49 tumor cell line resistant to FOLFIRINOX treatment, we could further demonstrate that the combination of mitazalimab and FOLFIRINOX induced a strong anti-tumor activity also in a chemoresistant variant of the MB49 cell line.

In conclusion, mitazalimab synergizes effectively with chemotherapy, leading to induction of long-term survival in a preclinical tumor model by reducing immunosuppressive M2 macrophages and improving T cell responses intratumorally. These preclinical data, together with the clinical data of mitazalimab from the phase 1 study (NCT02829099), where mitazalimab was well tolerated up to 1200 μg/kg with a manageable safety profile, support the ongoing clinical phase 2 study OPTIMIZE-1 (NCT04888312) of mitazalimab in combination with chemotherapy in pancreatic cancer.

Citation Format: Karin Enell Smith, Mia Thagesson, Anneli Nilsson, Doreen Werchau, Peter Ellmark. Mitazalimab, a potent CD40 agonist in combination with chemotherapy redirects and activates tumor infiltrating myeloid cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4155.

751 Neo-X-Prime bispecific antibodies targeting CD40 and tumor antigens promote cross-presentation of tumor exosome-derived neoantigen and induce superior anti-tumor responses compared to CD40 mAb

Background

Alligator's Neo-X-Prime platform aims to enable antigen presenting cells to efficiently enhance priming of tumor neoantigen-specific T cells with the goal of overcoming PD-1 resistance in certain tumor types. We hypothesize that binding of a CD40 x TAA bispecific antibody (bsAb) to CD40 on dendritic cells (DCs) and a tumor-associated antigen (TAA) on tumor exosomes or tumor debris leads to (i) activation of the DC, (ii) uptake of the tumor material, (iii) cross-presentation of tumor-derived neoantigen (present in exosomes or debris) and, iv) priming of tumor neoantigen-specific T cells, resulting in an increased quantity and/or quality of the tumor-targeting T cell pool.

Methods

Functionality was evaluated in vitro using CD40 reporter cells and monocyte-derived DCs, co-cultured with cells expressing TAA. Further, co-localization of TAA-expressing cellular debris with a CD40-expressing human B cell line in the presence of bsAbs was assessed using live cell imaging. In vivo, anti-tumor efficacy and immunological memory were assessed in human CD40 transgenic (hCD40tg) mice bearing MB49 bladder carcinoma tumors transfected with human TAA or controls. T cells isolated from OVA-specific TCR-transgenic mice were used to evaluate the effect of Neo-X-Prime bsAbs on antigen-specific T cell expansion in the presence of hCD40tg DCs and exosomes from MB49 tumors transfected with both human TAA and OVA using flow cytometry.

Results

Using CEA as a highly expressed TAA, we have developed lead Neo-X-Prime CD40-CEA bsAbs engineered to achieve an optimal profile. Further, using Neo-X-Prime concept molecules targeting EpCAM, we have demonstrated the ability to mediate co-localization of tumor debris and CD40 expressing antigen presenting cells that is dependent on the receptor density of the TAA. We have further shown that addition of Neo-X-Prime bsAbs to a co-culture of murine DCs, T cells and tumor-derived exosomes induces increased expansion of model neoantigen-specific T cells. In vivo, Neo-X-Prime bsAbs display a potent, TAA-dependent anti-tumor effect that is superior to CD40 mAbs. Cured mice develop a broad immunological memory that is not dependent on expression of the TAA. The tumor-localizing property of Neo-X-Prime bsAbs also shows potential for improved safety compared to CD40 monospecific antibodies.

Conclusions

Neo-X-Prime bsAbs have the potential to tumor-selectively target CD40-expressing antigen-presenting cells to mediate an expansion of the tumor-specific T cell repertoire, resulting in increased T cell infiltration and potent anti-tumor effects.

Ethics Approval

All experiments were performed after approval from the Malmö/Lund Animal Ethics Committee.

Abstract 1593: Mitazalimab, a potent CD40 agonist with potential for combination with chemotherapy

Mitazalimab (ADC-1013, JNJ-64457107) is a human CD40 agonistic antibody developed for immunotherapy of cancer. Activation of CD40, expressed on antigen-presenting cells (APC), leads to improved T cell priming and initiation of T cell-dependent anti-tumor responses. There are several CD40 agonists in clinical development with different characteristics, affecting both efficacy and tolerability. Mitazalimab is an FcγR crosslinking-dependent IgG1 antibody, with potential for high efficacy and safety. Immunologically “cold” tumors, such as pancreatic cancer, are defined by low infiltration of immune cells as well as low expression and release of neoantigens. In pancreatic cancer, infiltration of effector CD8+ T cells is blocked by the desmoplastic tumor stroma, which surrounds the tumor and hosts immune-suppressive macrophages that dampen the immune response in the tumor microenvironment (TME). By activating and re-directing the immunosuppressive M2 macrophages into tumoricidal M1 macrophages in the TME, CD40 agonists such as mitazalimab, have the potential to augment the response to chemotherapy and spark an effective immune reaction by i) priming T cells reactive to the tumor neoantigens released by the chemotherapy, and ii) inducing degradation of the stroma surrounding the tumor enhancing the efficacy of chemotherapy. The ability of mitazalimab to augment the response to chemotherapy was demonstrated in mice, transgenic for human CD40 (hCD40tg), inoculated with the syngeneic tumor cell line MB49. Mitazalimab, administered repeatedly together with FOLFIRINOX (oxaliplatin, irinotecan, 5-fluorouracil and folinic acid), synergized effectively with chemotherapy and induced a long-term survival. Further, it was also demonstrated that mitazalimab induced a concentration-dependent activation of tumor-associated macrophages (TAMs), purified from human tumor samples, into a more tumoricidal M1 like phenotype, by upregulation of cell surface markers such as CD83.In conclusion, mitazalimab re-directs human macrophages into a M1 like tumoricidal, less immunosuppressive phenotype, and synergizes effectively with chemotherapy, leading to induction of a long-term survival in a preclinical tumor mouse model. These preclinical data, together with the clinical data of mitazalimab from the phase 1 study (NCT02829099) where mitazalimab was well tolerated up to 1200 μg/kg with manageable side effects, support further clinical development of mitazalimab in combination with chemotherapy in pancreatic cancer.

Citation Format: Adnan Deronic, Mia Thagesson, Anneli Nilsson, Peter Ellmark, Anette Fält, Charlotte Fält, Karin Enell Smith. Mitazalimab, a potent CD40 agonist with potential for combination with chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1593.

The CTLA-4 x OX40 bispecific antibody ATOR-1015 induces anti-tumor effects through tumor-directed immune activation

BACKGROUND

The CTLA-4 blocking antibody ipilimumab has demonstrated substantial and durable effects in patients with melanoma. While CTLA-4 therapy, both as monotherapy and in combination with PD-1 targeting therapies, has great potential in many indications, the toxicities of the current treatment regimens may limit their use. Thus, there is a medical need for new CTLA-4 targeting therapies with improved benefit-risk profile.

METHODS

ATOR-1015 is a human CTLA-4 x OX40 targeting IgG1 bispecific antibody generated by linking an optimized version of the Ig-like V-type domain of human CD86, a natural CTLA-4 ligand, to an agonistic OX40 antibody. In vitro evaluation of T-cell activation and T regulatory cell (Treg) depletion was performed using purified cells from healthy human donors or cell lines. In vivo anti-tumor responses were studied using human OX40 transgenic (knock-in) mice with established syngeneic tumors. Tumors and spleens from treated mice were analyzed for CD8+ T cell and Treg frequencies, T-cell activation markers and tumor localization using flow cytometry.

RESULTS

ATOR-1015 induces T-cell activation and Treg depletion in vitro. Treatment with ATOR-1015 reduces tumor growth and improves survival in several syngeneic tumor models, including bladder, colon and pancreas cancer models. It is further demonstrated that ATOR-1015 induces tumor-specific and long-term immunological memory and enhances the response to PD-1 inhibition. Moreover, ATOR-1015 localizes to the tumor area where it reduces the frequency of Tregs and increases the number and activation of CD8+ T cells.

CONCLUSIONS

By targeting CTLA-4 and OX40 simultaneously, ATOR-1015 is directed to the tumor area where it induces enhanced immune activation, and thus has the potential to be a next generation CTLA-4 targeting therapy with improved clinical efficacy and reduced toxicity. ATOR-1015 is also expected to act synergistically with anti-PD-1/PD-L1 therapy. The pre-clinical data support clinical development of ATOR-1015, and a first-in-human trial has started (NCT03782467).

Abstract 3623: The CTLA-4 x OX40 bispecific antibody ATOR-1015 induces anti-tumor effects through tumor-directed immune activation

ATOR-1015 is a CTLA-4 x OX40 bispecific immune activating antibody developed for tumor-directed immunotherapy. ATOR-1015 binds both targets simultaneously, promoting cell-cell interactions expected to enhance the immuno-stimulating effect of the compound. The mode of action of ATOR-1015 is thought to be a combination of regulatory T cell (Treg) depletion and effector T cell activation. It can be seen as a next generation CTLA-4 antibody with tumor-directed activity and augmented Treg depletion. The ability to induce ADCC of human Treg was investigated using an FcγR expressing reporter assay demonstrating superior effect of ATOR-1015 compared to the monospecific antibody counterparts. Further, ATOR-1015 has been shown to induce activation of T cells in the presence of CTLA-4 expressing cells, ability that is not observed when combining the monoclonal counterparts. Syngeneic tumor models in vivo using human transgenic mice cross-reacting with both targets demonstrate that ATOR-1015 reduces tumor growth and prolongs survival. Further, ATOR-1015 treatment demonstrates superior increase in the intratumoral CD8+ T cell/Treg ratio compared to the monospecific counterparts, without affecting systemic T cells. This tumor directed immune activation is demonstrated to be due to the tumor localization abilities of ATOR-1015. In conclusion, ATOR-1015 is a next generation CTLA-4 antibody with tumor directed activity with augmented T-reg depletion. It is currently in GLP manufacturing of clinical material and will start clinical trials in the second half of 2018.

Citation Format: Niina Veitonmäki, Mia Thagesson, Doreen Werchau, Karin Hägerbrand, Kristine Smedenfors, Anne Månsson-Kvarnhammar, Anna Rosén, Maria Johansson, Christina Furebring, Per Norlén, Peter Ellmark. The CTLA-4 x OX40 bispecific antibody ATOR-1015 induces anti-tumor effects through tumor-directed immune activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3623.