Abstract: Provided herein are methods of treating a subject having a neoplastic disease, comprising administering to the subject a KIF18A inhibitor in an amount effective to treat the neoplastic disease a neoplastic disease in a subject. Also provided are methods of inducing or increasing tumor regression in a subject with a tumor and methods of reducing tumor or cancer growth in a subject. In exemplary aspects, the method comprises administering to the subject a KIF18A inhibitor. Methods of inducing or increasing death of tumor or cancer cells in a subject comprising administering to the subject a KIF18A inhibitor are also provided herein. Advantageously, the KIF18A inhibitors selectively treat the neoplastic disease, induce or increase tumor regression, and/or induce or increase death of tumor or cancer cells without overt toxicity to normal somatic cells.