A Study of KK2269 in Adult Participants With Solid Tumors

• Key Common Inclusion Criteria for Parts 1 and 2:

• Patients who are ≥ 18 years old at the time of informed consent
• Patients who have disease measurable by RECIST v1.1
• Patients with an ECOG PS of 0 or 1
• Patients with a life expectancy of at least 3 months in the judgement of the investigator or subinvestigator
• The specified periods have passed respectively after the completion of previous cancer treatments as of the date of enrollment at the time of the first dose of KK2269
• Patients who agree to use a medically effective method of contraception
• Key Additional Inclusion Criterion for Part 1:

•Patients with histological or cytological evidence of at least one locally advanced or metastatic non-CNS solid tumor

• Key Additional Inclusion Criteria for Part 2:

•Patients with histological or cytological evidence of any of the following disease: Gastric adenocarcinoma, GEJ adenocarcinoma, or esophageal adenocarcinoma, NSCLC (Only patients with NSCLC will be enrolled in the expansion part)

•Patients who are suitable for docetaxel treatment

• Key Common Exclusion Criteria for Parts 1 and 2:

• Patients with an uncontrolled or serious intercurrent illness
• Patients with known active central nervous system metastasis
• Patients with a history of ≥ Grade 3 allergic reaction to any antibody drug
• Patients with a history of autoimmune disease
• Patients with a history of HIV, HBV, or HCV at screening
• Patients who have a history of primary immunodeficiency
• Key Additional Exclusion Criterion For Part 2:

• Patients with a history of treatment with docetaxel