Julian Bertschinger

Discovery and characterization of COVA322, a clinical-stage bispecific TNF/IL-17A inhibitor for the treatment of inflammatory diseases.

Biologic treatment options such as tumor necrosis factor (TNF) inhibitors have revolutionized the treatment of inflammatory diseases, including rheumatoid arthritis. Recent data suggest, however, that full and long-lasting responses to TNF inhibitors are limited because of the activation of the pro-inflammatory TH17/interleukin (IL)-17 pathway in patients. Therefore, dual TNF/IL-17A inhibition is an attractive avenue to achieve superior efficacy levels in such diseases. Based on the marketed anti-TNF antibody adalimumab, we generated the bispecific TNF/IL-17A-binding FynomAb COVA322. FynomAbs are fusion proteins of an antibody and a Fyn SH3-derived binding protein. COVA322 was characterized in detail and showed a remarkable ability to inhibit TNF and IL-17A in vitro and in vivo. Through its unique mode-of-action of inhibiting simultaneously TNF and the IL-17A homodimer, COVA322 represents a promising drug candidate for the treatment of inflammatory diseases. COVA322 is currently being tested in a Phase 1b/2a study in psoriasis (ClinicalTrials.gov Identifier: NCT02243787).

A Bispecific HER2-Targeting FynomAb with Superior Antitumor Activity and Novel Mode of Action

Upregulation of HER2 is a hallmark of 20% to 30% of invasive breast cancers, rendering this receptor an attractive target for cancer therapy. Although HER2-targeting agents have provided substantial clinical benefit as cancer therapeutics, there is a need for the development of new agents aiming at circumventing anti-HER2 resistance. On the basis of the approved antibody pertuzumab, we have created a panel of bispecific FynomAbs, which target two epitopes on HER2. FynomAbs are fusion proteins of an antibody and a Fyn SH3–derived binding protein. One bispecific FynomAb, COVA208, was characterized in detail and showed a remarkable ability to induce rapid HER2 internalization and apoptosis in vitro. Moreover, it elicited a strong inhibition of downstream HER2 signaling by reducing HER2, HER3, and EGFR levels in vitro and in vivo. Importantly, COVA208 demonstrated superior activity in four different xenograft models as compared with the approved antibodies trastuzumab and pertuzumab. The bispecific FynomAb COVA208 has the potential to enhance the clinical efficacy and expand the scope of HER2-directed therapies, and delineates a paradigm for designing a new class of antibody-based therapeutics for other receptor targets. Mol Cancer Ther; 13(8); 2030–9. ©2014 AACR.

Generation, characterization and structural data of chymase binding proteins based on the human Fyn kinase SH3 domain

The serine protease chymase (EC = 3.4.21.39) is expressed in the secretory granules of mast cells, which are important in allergic reactions. Fynomers, which are binding proteins derived from the Fyn SH3 domain, were generated against human chymase to produce binding partners to facilitate crystallization, structure determination and structure-based drug discovery, and to provide inhibitors of chymase for therapeutic applications. The best Fynomer was found to bind chymase with a KD of 0.9 nM and koff of 6.6x10−4 s−1, and to selectively inhibit chymase activity with an IC50 value of 2 nM. Three different Fynomers were co-crystallized with chymase in 6 different crystal forms overall, with diffraction quality in the range of 2.25 to 1.4 Å resolution, which is suitable for drug design efforts. The X-ray structures show that all Fynomers bind to the active site of chymase. The conserved residues Arg15-Trp16-Thr17 in the RT-loop of the chymase binding Fynomers provide a tight interaction, with Trp16 pointing deep into the S1 pocket of chymase. These results confirm the suitability of Fynomers as research tools to facilitate protein crystallization, as well as for the development of assays to investigate the biological mechanism of targets. Finally, their highly specific inhibitory activity and favorable molecular properties support the use of Fynomers as potential therapeutic agents.

Linker Length Matters, Fynomer-Fc Fusion with an Optimized Linker Displaying Picomolar IL-17A Inhibition Potency

Background: IL-17A is a proinflammatory cytokine involved in various inflammatory diseases. Results: Potent IL-17A inhibitors were generated by fusing human Fyn SH3 domain derivatives (Fynomers) to the Fc part of an antibody. Conclusion: The linker length between the Fc part and the binding domain influences significantly the potency of Fc fusion proteins. Significance: Fynomers represent a promising class of therapeutic proteins. Fynomers are small binding proteins derived from the human Fyn SH3 domain. Using phage display technology, Fynomers were generated inhibiting the activity of the proinflammatory cytokine interleukin-17A (IL-17A). One specific Fynomer called 2C1 inhibited human IL-17A in vitro with an IC50 value of 2.2 nm. Interestingly, when 2C1 was genetically fused to the Fc part of a human antibody via four different amino acid linkers to yield bivalent IL-17A binding proteins (each linker differed in length), the 2C1-Fc fusion protein with the longest linker displayed the most potent inhibitory activity. It blocked homodimeric IL-17A with an IC50 value of 21 pm, which corresponds to a hundredfold improved IC50 value as compared to the value obtained with monovalent Fynomer 2C1. In contrast, the 2C1-Fc fusion with the shortest linker showed only an ∼8-fold improved IC50 value of 260 pm. Furthermore, in a mouse model of acute inflammation, we have shown that the most potent 2C1-Fc fusion protein is able to efficiently inhibit IL-17A in vivo. With their suitable biophysical properties, Fynomer-Fc fusion proteins represent new drug candidates for the treatment of IL-17A mediated inflammatory conditions such as psoriasis, psoriatic arthritis, or rheumatoid arthritis.

Mapping the conformational space accessible to BACE2 using surface mutants and cocrystals with Fab fragments, Fynomers and Xaperones

The aspartic protease BACE2 is responsible for the shedding of the transmembrane protein Tmem27 from the surface of pancreatic β-cells, which leads to inactivation of the β-cell proliferating activity of Tmem27. This role of BACE2 in the control of β-cell maintenance suggests BACE2 as a drug target for diabetes. Inhibition of BACE2 has recently been shown to lead to improved control of glucose homeostasis and to increased insulin levels in insulin-resistant mice. BACE2 has 52% sequence identity to the well studied Alzheimers disease target enzyme β-secretase (BACE1). High-resolution BACE2 structures would contribute significantly to the investigation of this enzyme as either a drug target or anti-target. Surface mutagenesis, BACE2-binding antibody Fab fragments, single-domain camelid antibody VHH fragments (Xaperones) and Fyn-kinase-derived SH3 domains (Fynomers) were used as crystallization helpers to obtain the first high-resolution structures of BACE2. Eight crystal structures in six different packing environments define an ensemble of low-energy conformations available to the enzyme. Here, the different strategies used for raising and selecting BACE2 binders for cocrystallization are described and the crystallization success, crystal quality and the time and resources needed to obtain suitable crystals are compared.

Abstract 658: A bispecific HER2 targeting FynomAb with superior anti-tumor activity and novel mode of action

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Upregulation of HER2 is a hallmark of 20% to 30% of invasive breast cancers, rendering this receptor an attractive target for cancer therapy. Although HER2 targeting agents have provided substantial clinical benefit as cancer therapeutics, there is a need for the development of new agents aiming at circumventing anti-HER2 resistance. Fynomers are small 7 kDa globular proteins derived from the SH3 domain of the human Fyn kinase (Fyn SH3) that can be engineered to bind with antibody-like affinity and specificity to virtually any target of choice. Fynomers can be fused to N-terminal and/or C-terminal ends of antibodies to generate multispecific therapeutics (FynomAbs) with tailored architectures. FynomAbs can be produced using standard antibody technology (GMP production yield of 3.3 g/L at 1000 L scale achieved), and show IgG-like biophysical properties and pharmacokinetic profiles. Based on the approved antibody pertuzumab we have created a panel of bispecific FynomAbs which target two epitopes on HER2. The activity of the HER2 targeting FynomAbs was found to depend on the FynomAb architecture, i.e. the spatial arrangement of the binding sites of antibody and the Fynomer. The most potent of these FynomAbs, termed COVA208, demonstrated superior tumor cell growth inhibition in vitro compared to pertuzumab and trastuzumab. COVA208 was characterized in detail and showed an increased ability to induce rapid HER2-internalization and apoptosis in vitro. Moreover, it elicited a stronger inhibition of downstream HER2 signaling which was accompanied by a reduction of HER2, HER3 and EGFR levels in vitro and in vivo. The therapeutic potential of COVA208 has been demonstrated in vivo in four different HER2 mouse models, where COVA208 exhibited excellent anti-tumor activity. Importantly, COVA208 demonstrated superior activity in vivo compared to trastuzumab and pertuzumab. The bispecific FynomAb COVA208 has the potential to enhance the clinical efficacy and expand the scope of HER2-directed therapies, and delineates a paradigm for designing a new class of antibody-based therapeutics for other receptor targets. Citation Format: Babette Schade, Simon Brack, Isabella Attinger-Toller, Kristina Klupsch, Richard Woods, Helen Hachemi, Ulrike von der Bey, Susann Koonig-Friedrich, Julian Bertschinger, Dragan Grabulovski. A bispecific HER2 targeting FynomAb with superior anti-tumor activity and novel mode of action. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 658. doi:10.1158/1538-7445.AM2014-658

Abstract 656: A bispecific HER2/CD3 targeting FynomAb with excellent tumor killing and favorable pharmacokinetic properties

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA There is increasing evidence that T cells are able to control tumor growth and increase survival of cancer patients. However, tumor-specific T cell responses are difficult to mount and sustain in cancer patients, and are limited by numerous immune escape mechanisms of tumor cells. A promising approach in the immunotherapy of cancer is to engage T cells to target tumor cells using bispecific therapeutics targeting a tumor-associated surface antigen and CD3e on T cells. Such therapeutics elicit T cell mediated lysis of tumor cells independent of T cell specificity. Fynomers are small 7 kDa globular proteins derived from the SH3 domain of the human Fyn kinase (Fyn SH3) that can be engineered to bind with antibody-like affinity and specificity to virtually any target of choice. Fynomers can be fused to N-terminal and/or C-terminal ends of antibodies to generate multispecific therapeutics (FynomAbs) with tailored architectures. FynomAbs can be produced using standard antibody technology (GMP production yield of 3.3 g/L at 1000 L scale achieved), and show IgG-like biophysical properties and pharmacokinetic profiles. We have generated a novel bispecific FynomAb which can simultaneously bind HER2 on tumor cells and CD3 on T cells. The bispecific HER2/CD3 targeting FynomAb COVA420 potently redirected T cells to HER2 expressing tumor cells showing picomolar tumor cell lysis activity. We present for the first time that a tailored architecture of the FynomAb leads to optimal tumor cell killing properties. The activity of COVA420 was found to be highly specific, as no lysis of cells was observed in the absence of HER2 expression. In addition, COVA420 demonstrated an antibody-like pharmacokinetic profile in mice. We anticipate that the increased half-life of T cell recruiting FynomAbs compared to other bispecific formats translates into a significant benefit for patients, since it circumvents the need for continuous infusion and prolongs the intervals between successive treatments. In summary, bispecific T cell recruiting FynomAbs represent a novel platform technology to redirect T cells to tumor cells with optimal biophysical properties, long-half lives and tailored architectures. Citation Format: Ulrich Wuellner, Fabian Buller, Kristina Klupsch, Simon Brack, Irene Zbinden, Roger Santimaria, Isabella Attinger-Toller, Susann Konig-Friedrich, Julian Bertschinger, Dragan Grabulovski. A bispecific HER2/CD3 targeting FynomAb with excellent tumor killing and favorable pharmacokinetic properties. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 656. doi:10.1158/1538-7445.AM2014-656