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We introduce a novel and versatile ADC-linker technology that is based on site-specific enzymatic payload conjugation to ‘off-the-shelf’ antibodies, i.e., without the need to reduce or engineer the antibody. The functionalization takes place site-specifically and stoichiometrically (drug-to-antibody ratio, DAR = 2.0) at the Fc-part of antibodies. The resulting ADCs show favorable biophysical properties such as high solubility and stability using different payloads. Additionally, initial ELISA findings show that our modification does not interfere with Fc-gamma receptor and FcRn binding. Importantly, our ADCs showed superior efficacy in different tumor animal models as compared to control Thiomab™ ADCs. Using native trastuzumab (non-engineered) as the targeting antibody and amanitin as payload, we generated within 36 hours highly homogeneous and pure ADCs with a well-defined DAR of 2.0 as confirmed by LC-MS. In in-vitro assays our ADCs demonstrated potent cytotoxicity in all tested cell-lines (SKBR-3, BT-474, JIMT-1, and NCI-N87) as compared to the control Thiomab™ ADCs, most strikingly for the JIMT-1 cell-line: EC50 of 0.15nM vs 2.5nM. In the mouse JIMT-1 tumor model, our anti-HER2 ADC was highly potent and resulted in complete tumor remission in all mice (10/10 mice) at a single dose of 2mg/kg. In contrast, the control Thiomab™-functionalized ADC showed tumor regrowth in 4 out of 10 animals, starting on day 50. The same high potency was observed for the NCI-N87 xenograft model at a dose of 3mg/kg in which tumor growth inhibition was significantly delayed versus the reference ADC (8/10 vs 4/10 animals alive on day 110). These encouraging results obtained so far indicate that our linker technology a) allows for fast (< 36 hours) and straightforward manufacturing of ADCs using different payloads without protein engineering efforts, b) results in ADCs with favorable biophysical properties and a clear defined drug-to-antibody ratio, and c) enables the generation of highly potent and stable, thus safer, next-generation ADCs. Citation Format: Philipp Rene Spycher, Julia Carina Frei, Jöri Elias Wehrmüller, Isabella Attinger-toller, Dragan Grabulovski, Torsten Hechler, Michael Kulke, Andreas Pahl, Martin Behe, Roger Schibli. Overcoming limitations of current Antibody-Drug Conjugates (ADCs) by a novel linker technology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-106.

CD3 bispecific therapies retargeting T cells to tumors have recently demonstrated striking activity in patients. Several CD3 bispecific antibodies directed against various tumor targets are currently being investigated in the clinic across different tumors. One limitation of these therapies is the risk of target-related toxicity due to low-level expression of tumor antigen in normal tissue. In this study we have engineered a bispecific CD3/HER2 FynomAb, COVA420, which redirects T cells with high potency and selectivity to tumor cells with high HER2 expression in vitro and in vivo. COVA420 activity depends on high HER2 density as no activity was observed on cells with lower HER2 levels as found in human normal tissue. These results suggest that COVA420 may spare normal tissue expressing low levels of HER2 while still having uncompromised efficacy on tumor cells with high HER2 expression. This concept may be applied to other cancer antigens that otherwise cannot be targeted by T cell redirecting approaches, and may therefore expand the applicability of CD3 bispecific FynomAbs to a larger number of solid tumors.

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 König-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

3066 Background: A promising approach in the immunotherapy of cancer is to recruit T cells to attack tumor cells using bispecific therapeutics targeting a tumor-associated surface antigen and CD3 o...