Inclusion Criteria:

- Subjects who have received first-line chemotherapy, which must have been a
platinum-containing regimen.

- Subjects who received maintenance paclitaxel or bevacizumab are eligible for
enrollment provided they have discontinued therapy at least (4 weeks for prior taxane
and at least 8 weeks for bevacizumab) prior to randomization and recovered from
toxicities to less than Grade 2.

- Subject must be currently in remission by clinical and radiological criteria
(Response Evaluation Criteria for Solid Tumors [RECIST 1.1]).

- Clinical remission is defined as: asymptomatic and a negative physical examination.

- Scans are required post completion of platinum-containing therapy to document disease
remission.

- Prior to the first-line regimen, CA 125 must have been elevated at first diagnosis,
must have normalized with the first-line therapy/regimen, and is currently elevated:

- CA 125 elevation is defined as 2 consecutive measurements that are both above the ULN
at least 4 weeks apart, with the second measure showing further increases from the
first measurement.

- CA 125 elevation must be at least 6 months from completion of first-line
platinum-containing regimen and have not occurred while receiving maintenance
therapy.

- Documentation of at least 1 normal CA 125 level at approximately 6 months (± 4 weeks)
or greater after completion of first line therapy is required.

- Subjects must have available archived tumor tissue.

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

- Adequate renal, hepatic, and bone marrow function based on screening laboratory
assessments.

Exclusion Criteria:

- Subjects with any evidence of disease including new ascites as confirmed by imaging.

- Any other prior antitumor systemic therapy except for first-line chemotherapy
associated with previous CA 125 normalization.

- Subjects with prior radiotherapy within 3 months of randomization and have not
recovered from all radiotherapy-related toxicities, who have received radiation
therapy to the chest within 3 months of randomization, or who have a history or
radiation pneumonitis.

- Subjects with protocol-specified active autoimmune processes except vitiligo or
thyroiditis.

- Subjects receiving investigational study drug for any indication, immunological-based
treatment for any reason, or potent CYP3A4 inducers or inhibitors.

- Subjects receiving monoamine oxidase inhibitors (MAOIs) within the 21 days prior to
screening; subjects who have ever had Serotonin Syndrome (SS) after receiving 1 or
more serotonergic drugs.

- Subjects for whom tamoxifen therapy is contraindicated.