The trial is a phase 2, parallel group design in patients with ER positive metastatic breast cancer.~This study will be a multicentre study conducted over an 18 month period. Patients who are taking either a third generation AI, tamoxifen or fulvestrant and have a documented evidence of progressive disease after achieving a best response of stable disease (for at least 6 months) or an objective response of CR or PR on the current treatment indicating the development of secondary resistance to current therapy will be entered into the study having undergone a screening period to continue receiving the same treatment with the addition of SFX-01.~At least 60 patients will be enrolled into one of three arms in a 1:1:1 ratio, i.e. 20 patients per arm. Enrolment will be based on current treatment.~Treatment Arm A: All patients will continue to receive their AI and, at the start of the study (D1), patients will additionally take SFX-01.~Treatment Arm B: All patients will continue to receive tamoxifen and, at the start of the study (D1), patients will additionally take SFX-01~Treatment Arm C: All patients will continue to receive fulvestrant 500 mg IM in 28 day Cycles and, at the start of the study (D1), patients will additionally take SFX-01.~Patient participation will include a Screening Phase, a Treatment Phase, and a Follow-up Phase of up to 28 weeks post D1 of dosing. The Screening Phase will be up to 28 days prior to enrolment. The Treatment Phase will extend from enrolment until the patient is discontinued from study treatment. The Follow-up Phase will be a maximum of 28 weeks and extend from the time of study entry until 30 days after the patient discontinues trial therapy.
This is a Phase 2 study to demonstrate the safety and efficacy of SFX-01 when used in combination with aromatase inhibitors (AIs), tamoxifen and fulvestrant.~Patients will be enrolled into one of three study arms (SFX-01 in combination with AI, tamoxifen or fulvestrant) based on their current therapy.