A Study of E7389 Liposomal Formulation (E7389-LF) Plus Nivolumab in Participants With Solid Tumor

Inclusion Criteria:

1. Phase 1b part only: Participants with advanced, nonresectable, or recurrent solid tumor for which no alternative standard therapy or no effective therapy exists (participants who will be the candidate of treatment by nivolumab monotherapy as standard therapy is acceptable)
2. Phase 2 part only: Participants with a confirmed diagnosis of nonresectable gastric cancer (GC), esophageal cancer (EGC) or small cell lung cancer (SCLC) who showed disease progression based on investigator's assessment during or after first line chemotherapy (second-line chemotherapy for GC) and did not receive any other systemic chemotherapy to advanced/recurrent disease
3. Participants who meet the following criteria for biopsy; Phase 1b part: Participants who have accessible tumors for biopsy and agree to tumor biopsy for pre- and post-treatment of study drug (If a pre-treatment biopsy cannot be obtained due to safety issue, then an archival tumor tissue sample may be submitted.) Phase 2 part: Participants who have accessible tumors for biopsy and agree with tumor biopsy for pre and post treatment of study drug (As an alternative to pre-treatment biopsy, tumor tissue sample taken from recurrent or advanced disease may be submitted). However, if the sponsor and the investigator discuss and agree in advance, and the participants agree to submission of archival tumor tissue, then these participants are eligible regardless of accessible tumors, and consent to biopsy is not necessary
4. Life expectancy of greater than or equal to (\>=) 12 weeks
5. Eastern Cooperative Oncology Group-Performance Status (ECOG-PS) 0-1
6. Phase 2 part only: At least one measurable lesion based on RECIST 1.1 (Lesions that have had radiotherapy or loco-regional therapies must show evidence of progressive disease to be deemed a measurable lesion)

Exclusion Criteria:

1. Diagnosed with meningeal carcinomatosis
2. Participants with brain or subdural metastases or invasion are not eligible
3. Active, known, or suspected autoimmune disease