Abstract A030: Discovery and preclinical characterization of novel macrocyclic KIF18A Inhibitors for treatment of chromosomally instable tumors

Abstract Chromosome instability (CIN) and Genetic instability are hallmark features of malignant tumor cells, contributing to tumour progression, drug resistance and metastasis. KIF18A, a member of the kinesin superfamily of motor proteins, is essential for preserving the structural integrity of the bipolar spindle apparatus during cell division. Recent studies have demonstrated that genetic depletion of KIF18A impacts the chromosome alignment, elongation of mitotic spindles, and activates spindle assembly checkpoint in chromosomal instable tumour cells ultimately leading to cell death, while having negligible impact towards the survival of normal cells. These findings suggest that targeting KIF18A represents a promising therapeutic approach for selectively inhibiting the growth of chromosomally instable tumours, while sparing the normal division of euploid cells. We have designed novel macrocyclic KIF18A inhibitors based on our structural understanding from Cryo-EM structures of initial acyclic binders. Structure guided SAR led to the identification of highly potent and selective compounds with optimized properties. Lead compounds exhibited significant inhibition of KIF18A ATPase activity and demonstrated robust cellular anti-proliferative potency in chromosomally instable (CIN-high) high-grade serous ovarian carcinoma cells (HGSOC, OVCAR-3) while retaining a good selectivity over the CIN-low MCF7 cells. This in vitro potency was supported by a significant and dose-dependent upregulation of phospho-Histone H3 and gamma-H2AX, consistent with the induction of mitotic arrest and DNA damage. Further, the lead compounds exhibited encouraging drug-like properties, including acceptable in vitro ADMET profile and excellent in vivo exposure with low clearance resulting in good oral bioavailability in rodents. Additionally, these compounds showed significant anti-tumor efficacy that was associated with robust induction of phospho-histone H3 in the OVCAR3 CDX model. The macrocyclic lead compound is being extensively evaluated in advanced in vitro and in vivo assays to support further development. Citation Format: Kiran Aithal B, Sandip Sengupta, Raghavendra N R, Shailesh Vishwanath. Jadhav, Aditya Kiran. Gatta, Balasubramanyam D, Suresh D. Babu, Gokulakrishnan R, Srinivasu P, Samiulla D S, Amith A, Aravind A B, Girish C. Daginakatte, Kavitha Nellore, Kishore Narayanan, Chandrasekhar Abbineni, Murali Ramachandra, Susanta Samajdar. Discovery and preclinical characterization of novel macrocyclic KIF18A Inhibitors for treatment of chromosomally instable tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A030.