Alexander Wiedenmann

Costimulatory T cell engagement via a novel bispecific anti-CD137 /anti-HER2 protein

Meeting abstracts CD137 is a potent costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily. The receptor, also known as 4-1BB, is mainly expressed on activated CD4+ and CD8+ T cells, activated B cells, and natural killer (NK) cells. While multiple lines of evidence show

Abstract B023: Costimulatory T-cell engagement via a novel bispecific anti-CD137 /anti-HER2 protein based on Anticalin® technology

Background: CD137 is a potent costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily. The receptor, also known as 4-1BB, is mainly expressed on activated CD4+ and CD8+ T cells, activated B cells, and natural killer (NK) cells. While multiple lines of evidence show that CD137 is a highly promising therapeutic target, current approaches are not designed to achieve a tumor-target driven activation, which may reduce the available therapeutic window via peripheral T cell activation and toxicity. To overcome this limitation, we applied Anticalin® technology to generate a bispecific protein therapeutic binding to CD137 and a differentially expressed tumor target, HER2. Methods: Anticalin® proteins are 18 kD protein therapeutics derived from human lipocalins which enable straight-forward multimeric drug targeting across several formats. We utilized phage display to generate an Anticalin protein binding to CD137 with high affinity and specificity. The CD137-specific Anticalin protein was genetically fused to a Trastuzumab variant, yielding four different constructs covering a range of distances between the binding sites of the T cell-target and the tumor cell target. To minimize Fc-receptor interaction of the resulting bispecific and concomitant potential toxicity towards CD137-positive cells, the backbone of Trastuzumab was switched from IgG1 to an engineered IgG4 isotype. Results: All four bispecific constructs bound the targets CD137 and HER2 with a nearly identical affinity compared to the parental building blocks, and both targets could be simultaneously bound. Compared to non-engineered Trastuzumab, binding to human receptors FcγRI and FcγRIII was significantly reduced, while binding to the neonatal Fc receptor (FcRn) was retained. Functional activity was demonstrated in human T cell activation assays, and shown to be tumor target (HER2) dependent. Conclusion: We report the first bispecific therapeutic protein that targets the potent costimulatory immunoreceptor CD137 in a tumor-target dependent manner, utilizing HER2 as the tumor target. Compared to currently existing CD137-targeting antibodies, this approach has the potential to provide a more localized activation of the immune system with reduced peripheral toxicity. Bispecific T cell engagers based on CD137 and HER2 may have utility in HER2-positive cancers where there is a significant unmet medical need, such as bladder, ovarian and gastric cancer. Citation Format: Marlon J. Hinner, Rachida-Siham Bel Aiba, Alexander Wiedenmann, Corinna Schlosser, Andrea Allersdorfer, Gabriele Matschiner, Christine Rothe, Ulrich Moebius, Shane A. Olwill. Costimulatory T-cell engagement via a novel bispecific anti-CD137 /anti-HER2 protein based on Anticalin® technology. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B023.

Abstract B016: Costimulatory T-cell engagement by PRS-343, a CD137 (4-1BB)/HER2 bispecific, leads to tumor growth inhibition and TIL expansion in humanized mouse model

Background: CD137 (4-1BB) is a key costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily. While multiple lines of evidence show that CD137 is a highly promising therapeutic target in cancer, current mAb-based approaches are not designed to achieve a tumor-target driven activation and may display toxicity and a limited therapeutic window due to peripheral T cell and NK cell activation. To overcome this limitation, we generated PRS-343, a CD137/HER2 bispecific that is designed to promote CD137 clustering by bridging CD137-positive T cells with HER2-positive tumor cells, thereby providing a potent costimulatory signal to tumor antigen-specific T cells. Methods: Anticalin® proteins are 18 kD protein therapeutics derived from human lipocalins. We utilized phage display to generate an Anticalin protein binding to CD137 with high affinity and specificity. PRS-343 was obtained by genetic fusion of the CD137-specific Anticalin protein to a variant of the HER2-targeting monoclonal antibody trastuzumab with an engineered IgG4 backbone. We have shown previously that the bispecific fusion PRS-343 targets CD137 and HER2 in a bispecific manner and efficiently activates T cells ex vivo in the presence of HER2-positive cells. Here, in vivo proof of concept data is presented utilizing a humanized mouse model in immunocompromised mice and the SK-OV-3 cell line as a HER2-positive xenograft. When tumors had reached a predefined size, mice received human PBMC via an intravenous route and weekly intraperitoneal injections of PRS-343 for three weeks. An IgG4 isotype antibody served as the negative control, while a CD137-targeting benchmark antibody and trastuzumab with an engineered IgG4 backbone (“tras-IgG4”) served as controls for monospecific targeting of CD137 and HER2, respectively. Results: PRS-343 activity was investigated at four different weekly doses of PRS-343 (4μg, 20μg, 100μg and 200μg). We found that PRS-343 dose-dependently led to strong tumor growth inhibition compared to treatment with the isotype control, and that the tumor response was accompanied by a significantly higher tumor infiltration with human lymphocytes (hCD45+). Interestingly, the anti-CD137 benchmark neither displayed tumor growth inhibition nor enhanced lymphocyte infiltration into tumors compared to isotype. The tras-IgG4 control was also devoid of lymphocyte infiltration into the tumor, but displayed a tumor growth inhibition comparable to PRS-343. Taken together, these data show that PRS-343 provided dual activity by both increasing the frequency of tumor-infiltrating lymphocytes by bispecific targeting of CD137 and HER2 as well as mediating direct tumor growth inhibition by the direct, monospecific targeting of HER2. Notably, the tumor growth inhibition provided by targeting HER2 did not require any antibody directed cellular cytotoxicity (ADCC) as both PRS-343 and the tras-IgG4 control lack the ability to interact with Fc-gamma receptors on NK cells that ADCC would require. The animal model also allowed investigating the potential safety of PRS-343: While the anti-CD137 benchmark accelerated the onset of graft-versus-host-disease and led to stronger expansion of CD8+ T cells in the peripheral blood compared to the isotype control group, both of these effects were absent for PRS-343. The data therefore support the envisaged mode of action of selective, tumor-localized costimulatory T cell activation, as well as the concept that such an approach may lead to higher efficacy and reduced systemic toxicity compared to conventional anti-CD137 mAbs. Conclusion: We report potent costimulatory T-cell engagement of the immunoreceptor CD137 in a HER2-dependent manner, utilizing the CD137/HER2 bispecific PRS-343. In a humanized mouse model, PRS-343 displays dual activity based on monospecific HER2-targeting and bispecific, tumor-localized costimulation of CD137. Compared to known CD137-targeting antibodies in clinical development, this approach has the potential to provide a more localized activation of the immune system with higher efficacy and reduced peripheral toxicity. The direct, monospecific HER2-targeting activity may provide an additional therapeutic benefit and work in synergy with local CD137 costimulation. The positive functional ex vivo and in vivo data of PRS-343 as well as the excellent developability profile support investigation of its anti-cancer activity in clinical trials. Citation Format: Marlon J. Hinner, Rachida-Siham Bel Aiba, Corinna Schlosser, Thomas Jaquin, Andrea Allersdorfer, Sven Berger, Alexander Wiedenmann, Gabriele Matschiner, Julia Schuler, Ulrich Moebius, Christine Rothe, Shane A. Olwill. Costimulatory T-cell engagement by PRS-343, a CD137 (4-1BB)/HER2 bispecific, leads to tumor growth inhibition and TIL expansion in humanized mouse model [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B016.

Abstract 556: Costimulatory T-cell engagement by the HER2/CD137 bispecific PRS-343 leads to strong antitumor effect in humanized mouse model

Background. CD137 (4-1BB) is a key costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily. While multiple lines of evidence show that CD137 is a highly promising therapeutic target in cancer, current mAb-based approaches are not designed to achieve a tumor-target driven activation and may display toxicity and a limited therapeutic window due to peripheral T cell and NK cell activation. To overcome this limitation, we generated PRS-343, a HER2/CD137 bispecific that is designed to promote CD137 clustering by bridging CD137-positive T cells with HER2-positive tumor cells, thereby providing a potent costimulatory signal to tumor antigen-specific T cells. Methods. Anticalin® proteins are 18 kD protein therapeutics derived from human lipocalins. We utilized phage display to generate an Anticalin protein binding to CD137 with high affinity and specificity. PRS-343 was obtained by genetic fusion of the CD137-specific Anticalin protein to a variant of the HER2-targeting monoclonal antibody trastuzumab with an engineered IgG4 backbone. Results. The bispecific fusion PRS-343 targets CD137 and HER2 with nearly identical affinities compared to the parental building blocks, and is capable of binding both targets simultaneously. We show ex vivo that T cells are efficiently activated when incubated with PRS-343 and HER2-positive cells, and that the activation is HER2-dependent. The in vivo activity of PRS-343 was investigated utilizing a humanized mouse model with a tumor cell-line-derived, HER2-positive xenograft. When tumors had reached a predefined size, mice received human PBMC via an intravenous route and weekly intraperitoneal injections of PRS-343 or controls for three weeks. We found that PRS-343 led to strong tumor growth inhibition and a significantly better response compared to either isotype control or anti-CD137 benchmark mAbs. The data, which include phenotyping of peripheral and intra-tumoral lymphocytes, support the envisaged mode of action of tumor-localized costimulatory T cell activation. Conclusion. We report potent costimulatory T-cell engagement of the immunoreceptor CD137 in a HER2-dependent manner, utilizing the HER2/CD137 bispecific PRS-343. Compared to known CD137-targeting antibodies in clinical development, this approach has the potential to provide a more localized activation of the immune system with higher efficacy and reduced peripheral toxicity. The positive functional ex vivo and in vivo data of PRS-343 as well as the excellent developability profile support investigation of its anti-cancer activity in clinical trials. Citation Format: Marlon J. Hinner, Rachida-Siham Bel Aiba, Corinna Schlosser, Alexander Wiedenmann, Andrea Allersdorfer, Gabriele Matschiner, Sven Berger, Ulrich Moebius, Christine Rothe, Shane A. Olwill. Costimulatory T-cell engagement by the HER2/CD137 bispecific PRS-343 leads to strong antitumor effect in humanized mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 556.

Abstract C205: Costimulatory T-cell engagement via a novel bispecific anti-CD137 /anti-HER2 protein

CD137 is a potent costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily. The receptor, also known as 4-1BB, is mainly expressed on activated CD4+ and CD8+ T cells, activated B cells, and natural killer (NK) cells. While multiple lines of evidence show that CD137 is a highly promising therapeutic target, current approaches using monospecific antibodies may display a limited therapeutic window due to peripheral T cell and NK cell activation, leading to unwanted toxicity. To overcome this limitation, we have generated a bispecific protein therapeutic designed to achieve a tumor-target driven activation of immune cells via binding to CD137 and to a differentially expressed tumor target, HER2. Anticalin® proteins are 18 kD protein therapeutics derived from human lipocalins. Using phage display technology a CD137-specific Anticalin was identified. The Anticalin was recombinantly fused to a trastuzumab variant at either the C or N terminus of the antibody´s heavy or light chain, yielding four different constructs covering a range of distances between the binding sites of the T cell-target and the tumor cell target. To minimize Fcγ-receptor interaction of the resulting bispecific and concomitant potential toxicity towards CD137-positive cells, the backbone of trastuzumab was switched from IgG1 to an engineered IgG4 isotype. Using ELISA or cell-based assays it was shown that all bispecific constructs bound their targets CD137 and HER2 with similar affinity compared to the parental building blocks, and both targets could be simultaneously bound. Binding to human receptors FcγRI and FcγRIII was significantly reduced in the bispecific constructs compared to non-engineered trastuzumab, while binding to the neonatal Fc receptor (FcRn) was retained. All constructs were shown to have excellent drug-like properties including thermal stability and plasma stability. HER2-dependent agonistic engagement of CD137 was demonstrated in ex-vivo T-cell activation assays utilizing HER2-positive human cell lines. The functional activity of the bispecific constructs was found to be dependent on their geometry. In conclusion, we report the first bispecific therapeutic protein that targets the potent costimulatory immunoreceptor CD137 in a tumor-target dependent manner, utilizing HER2 as the tumor target. Compared to currently existing CD137-targeting antibodies, this approach has the potential to provide a more controlled activation of the immune system in the tumor microenvironment with reduced peripheral toxicity. Bispecific T-cell engagers based on CD137 and HER2 have potential utility in HER2-positive cancers where there is a significant unmet medical need. Citation Format: Marlon J. Hinner, Rachida-Siham Bel Aiba, Alexander Wiedenmann, Corinna Schlosser, Andrea Allersdorfer, Gabriele Matschiner, Christine Rothe, Ulrich Moebius, Holbrook E. Kohrt, Shane A. Olwill. Costimulatory T-cell engagement via a novel bispecific anti-CD137 /anti-HER2 protein. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C205.