SUMOylation is a reversible post-translational modification that has been implicated in the regulation of various cellular processes including inflammatory responses and expression of Type I interferons (IFN1). In this report, we have explored the activity of the selective small molecule SUMOylation inhibitor subasumstat (TAK-981) in promoting antitumor innate immune responses. We demonstrate that treatment with TAK-981 results in IFN1-dependent macrophage and NK cell activation, promoting macrophage phagocytosis and NK cell cytotoxicity in ex vivo assays. Furthermore, pre-treatment with TAK-981 enhanced macrophage phagocytosis or NK cell cytotoxicity against CD20-positive target cells in combination with the anti-CD20 antibody rituximab. In vivo studies demonstrated enhanced antitumor activity of TAK-981 and rituximab in CD20-positive lymphoma xenograft models. Combination of TAK-981 with anti-CD38 antibody daratumumab also resulted in enhanced antitumor activity. TAK-981 is currently being studied in phase 1 clinical trials (NCT03648372, NCT04074330, NCT04776018, and NCT04381650) for the treatment of patients with lymphomas and solid tumors.

Guanylyl cyclase C (GCC) is a cell-surface protein that is expressed by normal intestinal epithelial cells, more than 95% of metastatic colorectal cancers (mCRC), and the majority of gastric and pancreatic cancers. Due to strict apical localization, systemically delivered GCC-targeting agents should not reach GCC in normal intestinal tissue, while accessing antigen in tumor. We generated an investigational antibody-drug conjugate (TAK-264, formerly MLN0264) comprising a fully human anti-GCC monoclonal antibody conjugated to monomethyl auristatin E via a protease-cleavable peptide linker. TAK-264 specifically bound, was internalized by, and killed GCC-expressing cells in vitro in an antigen-density-dependent manner. In GCC-expressing xenograft models with similar GCC expression levels/patterns observed in human mCRC samples, TAK-264 induced cell death, leading to tumor regressions and long-term tumor growth inhibition. TAK-264 antitumor activity was generally antigen-density-dependent, although some GCC-expressing tumors were refractory to TAK-264-targeted high local concentrations of payload. These data support further evaluation of TAK-264 in the treatment of GCC-expressing tumors.

In vitro properties of antibody-drug conjugates (ADCs) such as binding, internalization, and cytotoxicity are often well characterized before in vivo studies. Interpretation of in vivo studies might be significantly enhanced by molecular imaging tools. We present here a dual-isotope cryoimaging quantitative autoradiography (CIQA) methodology combined with advanced 3-dimensional imaging and analysis allowing for the simultaneous study of both antibody and payload distribution in tissues of interest in a preclinical setting. TAK-264, an investigational ADC targeting anti-guanylyl cyclase C (GCC), was synthesized using tritiated monomethyl auristatin E. The tritiated ADC was then conjugated to diethylenetriaminepentaacetic acid, labeled withIn, and evaluated in vivo in animals bearing GCC-positive and GCC-negative tumors. CIQA revealed the time course of drug release from ADC and its distribution into various tumor regions that are less accessible to the antibody. For GCC-positive tumors, a representative section obtained 96 h after tracer injection showed only 0.8% of the voxels to have colocalized signal, versus over 15% of the voxels for a GCC-negative tumor section, suggesting successful and specific cleaving of the toxin in the GCC-positive lesions. The combination of a veteran established autoradiography technology with advanced image analysis methodologies affords an experimental tool that can support detailed characterization of ADC tumor penetration and pharmacokinetics.

TAK-164 is an antibody-drug conjugate comprising a full-length, fully human IgG1 monoclonal antibody (mAb) directed towards the extracellular domain of guanylyl cyclase C (GCC). The mAb is conjugated using the peptide-linked indolino-benzodiazepine DNA alkylator DGN549 (also known as IGN-P1). TAK-164 demonstrates efficient binding to antigen-expressing cells in vitro, and GCC-dependent uptake that results in cytotoxicity. Following a single administration of TAK-164 in female SCID mice bearing GCC-positive xenografts, the pharmacokinetics of the conjugated antibody component of TAK-164 displayed low plasma clearance. Exposure to the ADC resulted in a dose- and time-dependent increase in DNA damage as measured by the pharmacodynamic marker pH2A.X in GCC-positive tumor-bearing xenografts. To further these observations, antitumor activity of TAK-164 was evaluated in multiple GCC-positive patient-derived xenografts. In these studies, a single intravenous administration of TAK-164 resulted in durable antitumor activity. Furthermore, the use of preclinical imaging demonstrated that TAK-164 preferentially accumulates in GCC-positive tumors, and that treatment response can be monitored using FDG-PET. These promising preclinical data warrant advancement of this ADC to clinical evaluation. Citation Format: Adnan O. Abu-Yousif, Bret M. Bannerman, Donna Cvet, Melissa Gallery, Michelle L. Ganno, Michael D. Smith, Katharine C. Lai, Thomas A. Keating, Jayaprakasam Bolleddula, Bradley Stringer, Mark G. Qian, Afrand Kamali, Kurt Eng, Secil Koseoglu, Cindy Q. Xia, O. Petter Veiby. TAK-164, a GCC-targeted antibody-drug conjugate (ADC) for the treatment of colorectal cancers and other GI malignancies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B120.