Arwed Cleve

Abstract 287: BAY 1816032, a novel BUB1 kinase inhibitor with potent antitumor activity

The spindle assembly checkpoint represents a highly conserved surveillance mechanism which safeguards correct chromosome segregation by delaying anaphase onset until all chromosomes are properly bi-oriented on the spindle apparatus. Non-catalytic functions of the mitotic kinase BUB1 (budding uninhibited by benzimidazoles 1) were reported to be essential for spindle assembly checkpoint activation. In contrast, the catalytic function of BUB1 plays a minor role in spindle assembly checkpoint activation but is required for chromosome arm resolution and positioning of the chromosomal passenger complex for resolution of spindle attachment errors. Here, we disclose for the first time the structure and functional characterization of a novel, first-in-class Bub1 kinase inhibitor. Medicinal chemistry efforts resulted in BAY 1816032 featuring high potency, long target residence time and good oral bioavailablity. It inhibits BUB1 enzymatic activity with an IC50 of 7 nanomol/L, shows slow dissociation kinetics resulting in a long target residence time of 87 min, and an excellent selectivity on a panel of 395 kinases. Mechanistically BAY 1816032 abrogated nocodazole-induced Thr-120 phosphorylation of the major BUB1 target protein histone H2A in HeLa cells with an IC50 of 29 nanomol/L, induced lagging chromosomes and mitotic delay. Persistent lagging chromosomes and missegregation were observed upon combination with low concentrations of paclitaxel. Single agent BAY 1816032 inhibited proliferation of various tumor cell lines with a median IC50 of 1.4 micromol/L and demonstrated synergy or additivity with paclitaxel or docetaxel in almost all cell lines evaluated (minimal combination index 0.3). In tumor xenograft studies BAY 1816032 only marginally inhibited tumor growth as single agent upon oral administration, however, upon combination with paclitaxel or docetaxel a strong and statistically significant reduction of tumor size as compared to the respective monotherapy was observed. Intratumoral levels of phospho-Thr120 H2A were found to be strongly reduced, and no hints on drug-drug interactions were found. In line with the good tolerability in xenograft studies, no relevant findings from non-GLP 2 weeks toxicological studies in rat and dog were reported. Our findings validate the innovative concept of interference with mitotic checkpoints and justify clinical proof of concept studies evaluating BUB1 inhibitor BAY 1816032 in combination with taxanes in order to enhance their efficacy and potentially overcome resistance. Citation Format: Gerhard Siemeister, Anne Mengel, Wilhelm Bone, Jens Schroder, Sabine Zitzmann-Kolbe, Hans Briem, Amaury E. Fernandez-Montalvan, Simon Holton, Ursula Monning, Oliver von Ahsen, Sandra Johanssen, Arwed Cleve, Marion Hitchcock, Kirstin Meyer, Franz von Nussbaum, Michael Brands, Dominik Mumberg, Karl Ziegelbauer. BAY 1816032, a novel BUB1 kinase inhibitor with potent antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 287. doi:10.1158/1538-7445.AM2017-287

Abstract 1321: Castration-resistant prostate cancer: BAY 1024767 blocks function of mutated androgen receptor.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Analysis of biopsies from prostate cancer metastases and of circulating tumor cells shows that androgen receptor (AR) mutations are often found in patients developing resistance to antiandrogen therapy, i.e. at the castration-resistant prostate cancer (CRPC) stage. Here we report on preclinical studies with a novel androgen receptor suppressor compound BAY 1024767 that exhibits strong antagonism for wild-type and mutated AR, both in vitro and in vivo. Mutations located in the AR ligand-binding domain (LBD) and potentially involved in the resistance to the standard of care bicalutamide were generated and tested in cell-based transactivation assays, using 0.1 nM R1881 for stimulation. Bicalutamide showed reduced antagonistic activity for AR E709Y and no antagonism up to 10 μM for AR W741C. In comparison, BAY 1024767 exhibited strong antagonism for these mutants. Another mechanism leading to CRPC is the elevation of intratumoral androgen levels. To mimick this situation, the transactivation assays were performed at a higher (1 and 10 nM R1881) androgen concentration. Bicalutamide, and also the novel antiandrogen MDV3100, showed much reduced antagonism for wild-type and W741C or E709Y mutant AR. Conversely, antagonism was still observed for BAY 1024767, especially at 1 nM R1881. The KuCaP-1 model, which is derived from a CRPC patient and harbors the W741C mutation, was obtained from the group of O. Ogawa (Kyoto University). Mice bearing the KuCaP-1 xenograft subcutaneously were treated with bicalutamide (60 mg/kg, PO, qdx20) or BAY 1024767 (50 mg/kg, PO, q2dx10). No effect on tumor growth was observed with bicalutamide (T/C=103%) whereas BAY 1024767 was able to inhibit tumor growth with a T/C of 36% on day 54 post-implantation. In another study we found that MDV 3100 (100 mg/kg, PO) and abiraterone acetate (200 mg/kg, PO) were inactive in the KuCaP-1 model (100% and 73% T/C, respectively). Citation Format: Bernard Haendler, Tatsuo Sugawara, Pascale Lejeune, Silke Koehr, Hortensia Faus, Matthias Busemann, Arwed Cleve, Ulrich Luecking, Franz von Nussbaum, Michael Brands, Dominik Mumberg. Castration-resistant prostate cancer: BAY 1024767 blocks function of mutated androgen receptor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1321. doi:10.1158/1538-7445.AM2013-1321