Excessively restrictive eligibility criteria hinder the enrollment of cancer patients to clinical trials. Those patients are supposed to represent the range of characteristics of the overall population with particular cancer. This, in turn, affects the generalizability of results and efficiency of the drug development process in oncology. Recent guidelines from the American Society of Clinical Oncology recommend broadening the eligibility criteria for early and late phase trials. A clearly defined rationale is essential for excluding patients. They selected specific items that commonly lead to the exclusion of patients from clinical trials, namely brain metastases, the minimum age for enrollment, human immunodeficiency virus infection, prior and concurrent malignancies, and organ dysfunction. We reviewed the clinical trials of abemaciclib and tucatinib, two novel anticancer agents, to investigate the eligibility criteria used in their ongoing trials and how the cut-offs for adequate kidney functions were defined. We provided recommendations to allow for enrollment of otherwise eligible patients.