A Study of TAS-120 in Patients With Metastatic Breast Cancer

Inclusion Criteria:

Provide written informed consent
Age ≥ 18 years of age

Histologically or cytologically confirmed recurrent locally advanced or metastatic breast cancer not amenable to treatment with curative intent, and the following cohort specific criteria:

A. Cohort 1

HR+ HER2- breast cancer harboring an FGFR2 gene amplification.
Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1
Has received 1-3 prior endocrine-containing therapies and up to 2 prior chemotherapy regimens for advanced/metastatic disease
Has received prior treatment with a CDK4/6 inhibitor or is ineligible for such treatment

B. Cohort 2

TNBC harboring an FGFR2 gene amplification
Measurable disease per RECIST 1.1
Has received at least 1 prior chemotherapy or chemotherapy/immunotherapy (PD-L1/PD-1 inhibitors) regimen for advanced/metastatic disease C. Cohort 3
TNBC or HR+ HER2- breast cancer harboring an FGFR2 gene amplification
Non measurable, evaluable disease per RECIST 1.1. Patients with bone-only disease must have lytic or mixed lytic-blastic lesions
Other criteria for either HR+ HER2- breast cancer or TNBC should be met as described for Cohort 1 and 2, respectively

D. Cohort 4

HR+ HER2- breast cancer harboring an FGFR1 high-level gene amplification
Measurable disease per RECIST 1.1
Has received 1-2 prior endocrine-containing therapies and no more than 1 prior chemotherapy regimen for advanced/metastatic disease. Prior treatment with fulvestrant is not permitted.
Has received prior treatment with a CDK4/6 inhibitor or is ineligible for such treatment
Pre/peri-menopausal patients must be on goserelin
Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
Archival or (preferably) fresh tumor tissue must be available
Adequate organ function

Exclusion Criteria:

History and/or current evidence of any of the following disorders:

Non-tumor related alteration of the calcium-phosphorus homeostasis that is considered clinically significant
Ectopic mineralization/calcification, including but not limited to soft tissue, kidneys, intestine, or myocardia and lung, considered clinically significant
Retinal or corneal disorder confirmed by retinal/corneal examination and considered clinically significant
Prior treatment with an FGFR inhibitor
A serious illness or medical condition(s)
Brain metastases that are untreated or clinically or radiologically unstable
Pregnant or lactating female