New targeted therapy duo enters human trials for advanced breast cancer

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Part A * Pathologically confirmed estrogen and/or progesterone receptor (ER/PR) positive and HER2 negative locoregionally recurrent or metastatic breast cancer * At least one target or non-target lesion per RECIST v1.1 criteria. * Male or non-pregnant, non-lactating female subjects age ≥18 years. Part B * Pathologically confirmed estrogen and/or progesterone receptor (ER/PR) positive and HER2 negative locoregionally recurrent or metastatic breast cancer * Refractory to endocrine therapy. Note: there is no limit on prior number of lines of endocrine therapy or prior treatments with CDK4/6, AKT, PI3K and/or mTOR inhibitors. * Received or declined at least one line of chemotherapy or antibody drug conjugate in the locoregionally recurrent or metastatic setting * Progressive disease or intolerance to last treatment. * At least one target lesion per RECIST v1.1 criteria. * Male or non-pregnant, non-lactating female subjects age ≥18 years. * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1. * Life expectancy of at least six months. * Adequate bone marrow reserve, hepatic function and renal function. Exclusion Criteria: Part A * Study participant has not recovered from clinically significant adverse event(s) resulting from most recent anticancer therapy/intervention. * Known central nervous system (CNS) disease, except for those subjects with treated brain metastasis who are stable for at least 1 month, having no evidence of progression or hemorrhage after treatment and no ongoing requirement for corticosteroids, as ascertained by clinical examination and brain imaging (magnetic resonance imaging \[MRI\] or computed tomography \[CT\]) during the screening period. * Radiotherapy for breast cancer ≤ 28 days prior * Received a radionuclide within a period of less than 10 physical half-lives of the administered radionuclide prior to dosing with 68Ga-R11228. * Any condition that precludes the proper performance of imaging procedures required in this study. Part B * Study participant has not recovered from clinically significant adverse event(s) resulting from most recent anticancer therapy/intervention * Treatment with anticancer therapy or with an investigational drug or device within 21 days or 5 half-lives of the agent (whichever is shorter) * Known central nervous system (CNS) disease, except for those subjects with treated brain metastasis who are stable for at least 1 month, having no evidence of progression or hemorrhage after treatment and no ongoing requirement for corticosteroids, as ascertained by clinical examination and brain imaging (magnetic resonance imaging \[MRI\] or computed tomography \[CT\]) during the screening period. * Radiotherapy for breast cancer ≤ 28 days * Prior systemic radionuclide therapeutic treatment. * Received a radionuclide within a period of less than 10 physical half-lives of the administered radionuclide prior to dosing with 68Ga-R11228. * Any unresolved NCI-CTCAE Version 5.0 Grade 2 or higher toxicity (except alopecia and Grade 2 platinum-therapy related neuropathy) from previous breast cancer treatment and/or from medical/surgical procedures or interventions. * Any condition that precludes the proper performance of imaging procedures required in this study.