Efficacy and Safety Study of REM-001 Photodynamic Therapy for Treatment of Cutaneous Metastatic Breast Cancer (CMBC)

All participants must have stable or responding systemic disease for at least 3 months at screening. REM-001 Therapy: Day 1: REM-001 = 0.8 mg/kg (IV) at 2 mL/Kg/hr (over approximately 24 minutes) Day 2: Light treatment per treatment area= 100 J/cm2 (10 min per treatment field) - 24 hrs (± 2 hrs) after infusion of REM-001. Total area of target lesions treated will be \< 200 cm2. Participants will be assessed at week 1, 4, 8, 12, 16, 20 and 24 weeks. An additional 4 weeks follow up will be undertaken if confirmatory assessment is required after week 24. Assessments will include: * cutaneous lesion response using photographic imaging * area of ulceration using photographic imaging * presence or absence of ulceration, bleeding, discharge and eschar * patient-reported assessments for pain and itch, using numeric rating scales * quality of life assessments * safety On Day 1 of treatment, the participant will undergo an ECG assessment post-infusion and a blood sample for determination of concentration of REM-001 in plasma will be collected post-infusion.