Study of ISB 1302 (CD3 Bispecific Ab) in HER2-positive Metastatic Breast Cancer

Inclusion Criteria

• Females with HER2-positive [IHC 2 +, with FISH confirmation] or 3+ [IHC or FISH] metastatic breast cancer that has progressed on last therapy. No more than 4 lines of therapy in metastatic setting (of which no more than 2 lines should be anti-HER2 antibody-based therapy).
• Measurable disease, defined as per RECIST v1.1.
• Eastern Cooperative Oncology Group (ECOG ) performance-status score of 2 or less
• Adequate bone marrow, renal, and liver function.
• Recovered from any previous surgery and no history of major surgery within the last 28 days prior to start of study drug
• Must be willing to undergo pre-treatment and on-treatment biopsies in Part 1 and Part 2.

Exclusion Criteria

• Any suspected or proven immunocompromised state, or infections, such as history of positive human immunodeficiency virus (HIV), known active or chronic hepatitis B virus (HBV) or hepatitis C virus (HCV).
• Any history or evidence of clinically significant cardiovascular disease.
• Evidence of clinically significant cardiovascular and respiratory conditions
• Previous antineoplastic treatment with immune checkpoint regulator or comparable immunotherapy within 8 weeks of starting study drug.
• Chemotherapy, radiotherapy, molecular-targeted therapy, or biological therapies (including HER2-directed therapies) within 4 weeks of starting study drug
• Hormone therapy within 2 weeks of starting study medications.
• Diagnosed with another malignancy that requires active therapy
• Brain metastases that require directed therapy.
• Has not recovered from any therapy related toxicities from previous treatments.
• Use of any investigational drug within 4 weeks from the start of study drug.
• Any condition that, in the opinion of the Investigator, would interfere with evaluation of the study drug or interpretation of subject safety or study results.