A Study of KK2269 in Adult Participants With Solid Tumors

* Key Common Inclusion Criteria for Parts 1 and 2:

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

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:

1. Patients with histological or cytological evidence of any of the following disease:
2. Gastric adenocarcinoma, GEJ adenocarcinoma, or esophageal adenocarcinoma
3. NSCLC
4. Patients who are suitable for docetaxel treatment

* Key Common Exclusion Criteria for Parts 1 and 2:

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

* Patients with a history of treatment with docetaxel