Phase 1b/2 Study of Avelumab With or Without Entinostat in Patients With Advanced Epithelial Ovarian Cancer

The study is comprised of 2 phases: an open-label Safety Lead-in (Phase 1b) followed by an
Expansion Phase (Phase 2). The Expansion Phase will evaluate the efficacy and safety of
entinostat with avelumab when administered at the Recommended Phase 2 Dose (RP2D) versus
avelumab alone in patients with advanced epithelial ovarian cancer in a randomized,
double-blind, placebo-controlled setting. In Phase 2, patients will be randomized in a 2:1
ratio to receive avelumab plus entinostat or avelumab plus placebo, respectively.

All patients will be assessed at Screening and at specified times during the conduct of the
study using standard clinical and laboratory assessments. Patients will be assessed for
response through radiological assessments. Patients will continue receiving their appropriate
cycles of study treatment until tumor progression or adverse events (AEs) occur which
necessitate discontinuing therapy as determined by the Investigator.

Inclusion Criteria:

- Histologically or cytologically confirmed epithelial ovarian, fallopian tube, or
peritoneal cancer

- Recurrent or progressive disease on or after initial platinum-based chemotherapy

- Evidence of measurable disease based on imaging studies within 28 days before the
first dose of study drug

- Previously received at least 3, but no more than 6, lines of therapy including at
least 1 course of platinum-based therapy

- Patient must have acceptable, applicable laboratory requirements

- Patients may have a history of brain metastasis provided certain protocol criteria are
met

- Experienced resolution of toxic effect(s) of the most recent prior anti-cancer therapy
to Grade ≤1 (except alopecia or neuropathy)

- Able to understand and give written informed consent and comply with study procedures.

Exclusion Criteria:

- Non-epithelial ovarian carcinomas or ovarian tumors with low malignant potential
(i.e., borderline tumors)

- Another known malignancy that is progressing or requires active treatment (excluding
adequately treated basal cell carcinoma or cervical intraepithelial neoplasia/cervical
carcinoma in situ or melanoma in situ). Prior history of other cancer is allowed, as
long as there is no active disease within the prior 5 years.

- Diagnosis of immunodeficiency or receiving systemic steroid therapy or any other form
of immunosuppressive therapy within 7 days prior to enrollment.

- Active autoimmune disease that might deteriorate when receiving an immunostimulatory
agent

- Previously treated with a histone deacetylase inhibitor (i.e., vorinostat, belinostat,
romidepsin, panobinostat), PD-1/PD-L1-blocking antibody (i.e., atezolizumab,
nivolumab, pembrolizumab), or a cytotoxic T-lymphocyte associated protein-4 (CTLA-4)
agent

- Currently enrolled in (or completed) another investigational drug study within 30 days
prior to study drug administration

- A medical condition that precludes adequate study treatment or increases patient risk