TAS-116 Plus Palbociclib in Breast and Rb-null Cancer

Inclusion Criteria: * Histologically or cytologically confirmed solid tumors such as ER/PR(+), HER2(-) breast cancer, SCLC, soft tissue sarcoma, endometrial cancer, bladder cancer that has progressed on at least one standard therapy or for which there is no standard therapy. (Metastases or recurrences do not need to be histologically confirmed.) * Patients with breast cancer whose tumors progressed after prior palbociclib. * Patients with any treatment-refractory solid tumor that is RB-deficient (9 patient cohort expansion after phase Ib dose de-escalation phase). Examples include SCLC, soft tissue sarcoma, endometrial cancer, bladder cancer. Patients should have no available standard therapy. * Patients must have at least one area of measurable disease per RECIST Version 1.1 for solid tumors. * Recovered (\< grade 1) from clinically significant effects of any prior surgery, radiotherapy or other anti-neoplastic therapy, except alopecia * Males or females age \>18 years * Life expectancy \> 60 days as documented by treating investigator * Eastern Cooperative Oncology Group (ECOG) performance status score 0 or 1 * Patients must have normal organ and marrow function as defined in detail in the study protocol * Women must not pregnant and not nursing. * Women of childbearing potential must have a negative pregnancy test (urine or serum) within 7 days prior to starting the study drug (prior to Day 1 of treatment). Both males and females must agree to use effective birth control …