A Phase 1, open-label, dose-escalation clinical trial of MBQ-167 in participants with advanced Breast Cancer for whom Standard of Care (SOC) has failed or has proven intolerable.

The main questions this clinical trial aims to answer are:

• What, if any, are the side effects of different dose levels in humans?
• What is the maximum tolerated dose?
• How does the human body process the drug?
• Does the drug slow, stop or eliminate cancer in human participants?

Participants will be asked to:

• provide informed consent
• be evaluated by physicians and provide laboratory specimens to determine if eligible
• take MBQ-167 orally twice a day for at least 21 days
• may continue dosing, if safe to do so, until not effective or other decision to stop is made
• participate in multiple visits that include additional evaluations, laboratory tests and diary review until after stopping the investigational drug

Key Inclusion Criteria:

• The investigator will evaluate these and other criteria to determine whether a participant can be included in this study.
• Histologically and/or cytologically confirmed advanced breast cancer which has progressed after treatment with approved therapies or for which there are no standard therapies available.
• Participants with known brain metastases may be eligible if specific conditions are met.
• Life expectancy ≥6 months, in the opinion of the investigator, after starting MBQ-167.
• Are able to swallow capsules twice daily with a meal.

Key Exclusion Criteria:

• The investigator will evaluate these and other criteria to determine whether a participant should be excluded from this study.
• Inability to take oral medication, or malabsorption syndrome or any other uncontrolled gastrointestinal condition (e.g., nausea, diarrhea, or vomiting) that might impair the bioavailability of MBQ-167.
• Females who are pregnant or breastfeeding.
• Participants who have received any anticancer treatment within 4 weeks or any investigational agent within 28 days prior to the first dose of trial drug or who have not recovered from any acute toxicity greater than Grade 0 or 1 related to previous anticancer treatment.
• Participants who have received any anticancer treatment within 4 weeks or any investigational agent within 28 days prior to the first dose of trial drug or who have not recovered from any acute toxicity greater than Grade 0 or 1 related to previous anticancer treatment.
• Active malignancies other than advanced breast cancer will be excluded from the study.