This phase I trial tests the safety, side effects, and best dose of abemaciclib in combination with 5-fluorouracil and how well it works in treating patients with colorectal cancer that has spread from where it first started (primary site) to other places in the body (metastatic) and that has not responded to treatment (refractory). Abemaciclib, a type of cyclin-dependent kinase inhibitor, blocks certain proteins, which may help keep tumor cells from growing. 5-fluorouracil, a type of antimetabolite, stops cells from making deoxyribonucleic acid (DNA) and may kill tumor cells. Giving abemaciclib in combination with 5-fluorouracil may be safe, tolerable, and/or effective in treating patients with metastatic and refractory colorectal cancer.
Patients must have histologically or cytologically confirmed microsatellite stability (MSS) metastatic colorectal cancer where patients have progressed on standard therapies which would have included 5-FU or capecitabine, oxaliplatin, and irinotecan. Patients must have had progression of disease (PD) or intolerance to bevacizumab and anti-EGFR antibodies (cetuximab or panitumumab) in patients who have left-sided and RAS-wildtype CRC
Patients must have measurable disease
Age ≥ 18 years. Because no dosing or adverse event data are currently available on the use of abemaciclib in combination with 5-FU in patients < 18 years of age, children are excluded from this study
Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Karnofsky ≥ 60%)
Patients who have not recovered from adverse events due to prior anti-cancer therapy (i.e., have residual toxicities > grade 1) with the exception of alopecia or grade 2 peripheral neuropathy. Patients who are experiencing immune related adverse events (AEs) which are adequately treated with hormone replacement therapy, including diabetes on insulin regimen, hypothyroidism on levothyroxine, and adrenal insufficiency on steroid replacement will also be eligible
Patients who are receiving any other investigational agents. There is to be a washout period of two weeks or five half-lives, whichever is shorter, for all investigational agents prior to treatment initiation on this study. Individual cases can be discussed with the national PI
History of allergic reactions attributed to compounds of similar chemical or biologic composition to abemaciclib or other agents (5-FU) used in study such as a previous intolerance to 5-FU or capecitabine, including patients with known or suspected dihydropyrimidine dehydrogenase deficiency
Patients who have received previous treatment with a CDK4/6 inhibitor