A Safety Study of SGN-LIV1A in Breast Cancer Patients

Inclusion Criteria:

- Pathologically confirmed diagnosis of breast cancer with radiographic evidence of
incurable, unresectable, locally advanced or metastatic disease (LA/MBC)

- One of the following:

- Part A) Triple-negative disease (ER/PR/HER2-negative) and received at least 2
prior cytotoxic regimens in the incurable, unresectable, LA/MBC setting; or
ER-positive and/or PR-positive/HER2-negative disease and received at least 2
prior cytotoxic regimens in the incurable, unresectable, LA/MBC setting and are
no longer a candidate for hormonal therapy (not enrolling new patients);

- Part B) Combination Arm: HER2-positive disease and received at least 2 prior
cytotoxic regimens in the incurable, unresectable, LA/MBC setting (not enrolling
new patients);

- Part C) Triple-negative disease and received 2-4 prior non-hormonally-directed
therapies in the MBC setting (not enrolling new patients);

- Part D) Triple-negative disease and received 1 prior non-hormonally-directed or
cytotoxic therapy in the MBC setting; or

- Part E) ER-positive and/or PR-positive/HER2- disease and received no more than 1
prior non-hormonally-directed or cytotoxic therapy in the MBC setting.

- Newly obtained tumor tissue biopsy and archived tumor tissue, if available, must be
collected for central pathology determination of LIV-1 expression

- Measurable disease

- Eastern Cooperative Oncology Group performance status 0 or 1

- Combination Arm: adequate heart function

Exclusion Criteria:

- Pre-existing neuropathy Grade 2 or higher

- Malignant CNS disease that has not been definitively treated

- Prior treatment with SGN-LIV1A or prior treatment with an MMAE-containing therapy

- Combination Arm: hypersensitivity to trastuzumab