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, locallyadvanced, or metastatic solid tumor with AXIN1 or APC mutation. If a participant hascolorectal cancer, then they must be RAS / RAF wild type to enroll into the APCmutant cohort

2. Have experienced progressive disease, relapsed disease, or be intolerant to at leastone established standard systemic anti-cancer treatment, or in the opinion of theInvestigator 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) inhibitorwithin 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