A Study of MORAb-202 Versus Investigator's Choice Chemotherapy in Female Participants With Platinum-resistant High-grade Serous (HGS) Ovarian, Primary Peritoneal, or Fallopian Tube Cancer

Inclusion Criteria:

* Female participants with histologically-confirmed diagnosis of HGS ovarian, primary peritoneal, or fallopian tube cancer.
* Platinum-resistant disease, defined as:
* For participants who had only 1 line of platinum-based therapy: progression between \> 1 month and ≤ 6 months after the last dose of platinum-based therapy of at least 4 cycles.
* For participants who had 2 or 3 lines of platinum-based therapy: progression ≤ 6 months after the last dose of platinum-based therapy.
* Participants have received at least 1 but no more than 3 prior lines of systemic therapy and for whom single-agent therapy is appropriate as the next line of therapy. Participants may have been treated with up to 1 line of therapy subsequent to determination of platinum-resistance.
* Disease progression per RECIST v1.1 (by investigator assessment) of at least 1 measurable lesion on or after the most recent therapy.
* Either formalin-fixed, paraffin-embedded (FFPE) tissue (up to 5 years old) or newly-obtained biopsies must be available for FRα assessment prior to randomization.
* Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 or 1.

Exclusion Criteria:

Medical Conditions

* Clear cell, mucinous, endometrioid or sarcomatous histology, or mixed tumors containing components of any of these histologies, or low grade or borderline ovarian cancer.
* Primary platinum-refractory ovarian cancer defined as disease progression within 1 month of the last dose of the first line platinum-containing regimen.
* Pulmonary function test (PFT) abnormalities: FEV1 \< 70% or FVC \< 60%, and DLCO \< 80%.
* Investigator-assessed current ILD/pneumonitis, or ILD/pneumonitis suspected at screening or history of ILD/pneumonitis of any severity including ILD/pneumonitis from prior anti-cancer therapy.
* Significant third-space fluid retention (eg, ascites or pleural effusion) that requires repeated drainage.

Physical and Laboratory Test Findings

* Evidence of organ dysfunction or any clinically-significant deviation from normal in physical examination, vital signs, ECG, or clinical laboratory determinations beyond what is consistent with the target population.

Allergies and Adverse Drug Reactions

* Has any prior severe hypersensitivity (≥ Grade 3) to monoclonal antibodies or eribulin or contraindication to the receipt of corticosteroids or any of the excipients (investigators should refer to the prescribing information for the selected corticosteroid).
* History of allergy or contraindication to IC chemotherapy agent selected if randomized to Arm C.

Other protocol-defined inclusion/exclusion criteria apply.