A Study of REC-4881 in Participants With Cancers Which Have an AXIN1 or APC Mutation

Inclusion Criteria: 1. 55 years of age or older with histologically-confirmed unresectable, locally advanced, or metastatic solid tumor with AXIN1 or APC mutation. If a participant has colorectal cancer, then they must be RAS / RAF wild type to enroll into the APC mutant cohort 2. Have experienced progressive disease, relapsed disease, or be intolerant to at least one established standard systemic anti-cancer treatment, or in the opinion of the Investigator have been considered ineligible for standard therapy 3. Measurable disease at baseline per RECIST 1.1 criteria 4. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1 Exclusion Criteria: 1. Received treatment with another mitogen-activated protein kinase (MEK) inhibitor within two months of first dose of REC-4881 2. Left ventricular ejection fraction (LVEF) \<50% as measured by echocardiogram (ECHO) or multigated acquisition (MUGA) scan