A Phase I, Open-Label, International, Multicenter, Non-Randomized, Dose-Escalating Safety, Tolerance and Pharmacokinetic Study of Oral Administration of TAS-114 in Combination with S-1 in a Twice Daily Schedule for 14 Days in Patients with Advanced Solid Tumors.

This is an open-label, non-randomized, dose-escalation Phase I study of TAS-114 administered in combination with S-1, evaluating the safety, tolerability, pharmacokinetics and preliminary antitumor activity of the TAS-114/S-1 regimen in patients with advanced solid tumors.

The study will be conducted in two parts: a Dose-Escalation Phase (Part 1) to determine the MTD; and an Expansion Phase (Part 2) to further evaluate the safety and preliminary efficacy with the MTD. Patients will receive the study medication according to the proposed treatment schedule until disease progression (PD), occurrence of intolerable side effects, removal by the Investigator or withdrawal of consent. A patient is considered discontinued from study treatment when TAS-114 is discontinued.

Male or female patients age 18 years or older with confirmed advanced solid tumor(s) for which no standard therapy exists.

TAS-114/S-1 will be administered BID for 14 days followed by a 7-day recovery period, every 21 days (1 cycle) in patients with advanced solid tumors.

Inclusion Criteria:

1. Has provided written informed consent.
2. Is ≥18 years of age
3. Has histologically or cytologically confirmed advanced or metastatic solid tumor(s) for which no standard therapy exists.
4. Expansion Phase only: Has at least one measurable lesion
5. Is able to take medications orally (e.g., no feeding tube).
6. Has adequate organ function
7. Women of child-bearing potential must have a negative pregnancy test (urine or serum) within 7 days prior to starting the study drug.
8. Is willing and able to comply with scheduled visits and study procedures.

Exclusion Criteria:

1. Has received treatment with any proscribed treatments within specified time frames prior to study drug administration.
2. Has a serious illness or medical condition(s)
3. Is receiving concomitant treatment with drugs that may interact with S-1