Inclusion Criteria: - Participants must sign an approved informed consent form (ICF). - Participants must be ≥ 18 years of age. - Participants must have pathology-confirmed epithelial ovarian, fallopian tube, or primary peritoneal carcinoma. - Participants must have primary or secondary platinum-resistant ovarian cancer. - Participants must have at least a single (RECIST v1.1-defined) measurable lesion. - For the purpose of obtaining a RECIST v1.1 baseline scan, participants must have a radiological evaluation conducted no more than 28 days prior to beginning study therapy (PLD). NOTE: For participants with a history of CNS metastasis, baseline radiological imaging must include an evaluation of the head. - Participants must have had prior debulking surgery. - Participants must have received prior platinum-based chemotherapy for management of primary disease but must not have received more than 2 prior systemic cytotoxic regimens. - Participants are allowed to have received, but are not required to have received, one additional non-cytotoxic antitumor agent (eg, biologic or cytostatic) for the management of ovarian cancer. - Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1. - Participants must have recovered (to baseline/stabilization) from prior cytotoxic therapy-associated acute toxicities. - Participants must have adequate organ function including: 1. Bone Marrow Reserve: 1. Absolute neutrophil count (ANC) ≥ 1.5x10^9/L prior to treatment. Participants on maintenance doses of granulocyte colony stimulating factor (G-CSF) are eligible. 2. Platelets ≥ 100x10^9/L 3. Hemoglobin ≥ 9 g/dL 4. Use of supportive care measures (eg, use of white blood cell [WBC] growth factors, antiemetics, epoetin) should follow the ASCO guidelines as listed at www.asco.org. Participants should receive full supportive care, including transfusion of blood as mandated by clinical need; however, transfusions administered for the sole purpose of meeting the study inclusion criteria between the time informed consent is signed and first dose of EC145/placebo/PLD is administered are not allowed. 2. Hepatic: Total bilirubin level < 1.5 x ULN and ALT, AST, GGT, and alkaline phosphatase levels < 2.5 x ULN. 3. Renal: Serum creatinine level ≤ 1.5 x ULN or for participants with serum creatinine levels above 1.5 x ULN, creatinine clearance ≥ 50 mL/min/1.73m^2 4. Cardiac: Left ventricular ejection fraction (LVEF) equal to or greater than the institutional lower limit of normal. Exclusion Criteria: - Patients refractory to primary platinum therapy where "refactory" is defined as disease progression within 6 months of first dose of initial platinum-based therapy. - Diagnosis of "tumor of low-malignant potential". - Prior exposure to PLD or anthracycline therapy. - Prior exposure to FR-targeted therapy (eg, EC145, EC0225, EC0489, farletuzumab). - Prior therapy with vinorelbine (Navelbine®) or vinca-containing compounds. - Prior abdominal or pelvic radiation therapy or radiation therapy to > 10% of the bone marrow at any time in the past or prior radiation therapy within the past 3 years to the breast/sternum, dermal lesions, head or neck. - Recent (i.e., ≤ 6 weeks) history of abdominal surgery or peritonitis - Serious comorbidities (as determined by the investigator) such as, but not limited to, active congestive heart failure or recent myocardial infarction. Patients who require antifolate therapy for the management of comorbid conditions (e.g., rheumatoid arthritis) will be excluded from the trial. - Pregnant or nursing. - Concurrent malignancy requiring therapy (excluding non-invasive carcinoma or carcinoma in situ). - Symptomatic central nervous system (CNS) metastasis. - Other concurrent chemotherapy, immunotherapy, radiotherapy, or any ancillary therapy that is considered to be investigational (i.e., used for non-approved indications(s) and in the context of a research investigation). Use of low dose corticosteroid therapy (e.g., for nausea prophylaxis) is acceptable; however, concomitant tamoxifen therapy is not. Supportive care measures are allowed.