Inclusion Criteria:

- Cytological or histological confirmation of locally advanced/metastatic or recurrent
epithelial ovarian cancer, fallopian tube cancer, primary peritoneal cancer or
endometrial cancer; OR, cytological or histological confirmation of locally advanced
/metastatic Her2 non-overexpressing breast cancer

- Eighteen years of age or above

- Candidates for chemotherapy

- Able to understand and sign an informed consent (or have a legal representative who
is able to do so)

- Measurable disease according to RECIST v1.1

- ECOG Performance Score (PS) of ≤ 2

- Willing to abstain from sexual intercourse or to use an effective form of
contraception during the study and for 90 days following the last dose of MM-121

Exclusion Criteria:

- Prior radiation therapy to >25% of bone marrow-bearing areas

- Evidence of any other active malignancy

- Active infection or fever> 38.5°C during screening visits or on the first scheduled
day of dosing

- Symptomatic CNS disease

- Known hypersensitivity to any of the components of MM-121 or who have had
hypersensitivity reactions to fully human monoclonal antibodies

- Received treatment, within 30 days prior to the first scheduled day of dosing, with
any investigational agents that have not received regulatory approval for any
indication or disease state

- Pregnant or breast feeding