Fulvestrant Plus Enzalutamide in ER+/Her2- Advanced Breast Cancer

This is a single arm, non-randomized, open-label phase 2 study designed to evaluate the
tolerability and clinical activity of adding enzalutamide to fulvestrant treatment in women
with advanced breast cancer that are ER and/or PR-positive and Her2 normal. In this study 500
mg of Fulvestrant will be given IM on days 1, 15, 28, then every 4 weeks as per standard of
care (SOC) and 160mg of Enzalutamide will be, in conjunction with Fulvestrant, PO daily.

Inclusion Criteria:

1. ER+ Her2- breast cancer

2. Metastatic

3. Female, at least 18 years of age

4. Candidate for fulvestrant therapy - patients who have started fulvestrant may enter
this trial if within 3 months of starting fulvestrant

5. Measurable or evaluable by RECIST 1.1

6. ECOG PS 0-2

7. Able to swallow study drug and comply with study requirements

8. Tumor available for fresh biopsy (two biopsies - pretreatment as regards enzalutamide,
and during treatment at 4 weeks). The patient will be also be asked if they would be
willing to provide a third biopsy at time of progression.

9. If patient is pre- or peri- menopausal, then will need to have concurrent ovarian
suppression. Patients may have already gotten the loading dose of ovarian suppression.
Pre- or peri- menopausal subjects must have a negative urine pregnancy test confirmed
at screening.

10. ANC >1000/uL and platelets >75,000/uL at screening visit

11. Total bilirubin < 1.5 times upper limit of normal (ULN) at the screening visit unless
an alternate nonmalignant etiology exists (eg, Gilbert's disease)

12. Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) < 3 times ULN or <
5 times ULN if patient has documented liver metastases

13. Creatinine < 1.5 times ULN

14. INR < 1.5 times ULN, or if on warfarin, can safely transition off for biopsy

15. Willing to donate blood for research at 4 time points

16. Written informed consent obtained prior to biopsies and blood samples

17. Agreement to exercise appropriate use of contraception. Subjects should use 2
acceptable methods of birth control (one of which must include a condom as a barrier
method of contraception) starting at the time of screening for an enzalutamide study
and continuing throughout the course of treatment and for at least three months after
enzalutamide is discontinued.

Exclusion Criteria:

1. Current or previously treated brain or leptomeningeal metastases

2. History of seizures

3. Prior treatment with an anti-androgen (abiraterone, ARN-509, bicalutamide,
enzalutamide, ODM-201, TAK-448, TAK-683, TAK-700, VT-464)

4. Systemic estrogens or androgens within 14 days before initiating therapy. Vaginal
estrogens are allowed if necessary for patient comfort.