A Clinical Study of KK2260 in Patients With Advanced or Metastatic Solid Tumors

Inclusion Criteria:

<Common Inclusion Criteria for Part 1a, Part 1b, and Part 2

1. Patients who have given informed written consent.

2. Male or female subjects ≥18 years of age, at time of signing informed consent.

3. Subjects who are refractory to standard treatment, intolerant of standard treatment,for whom standard treatment does not exist, or who have refused standard treatment.

4. Patients with measurable disease according to RECIST version 1.1

5. Patients who have had the certaion periods between the date of completion of priortherapy and the date of enrollment

6. Subjects who agree to have a tumor biopsy as part of the baseline examination.Patients who have difficulty in performing a tumour biopsy and have agreed to submita previously collected stored specimen.

7. Patients with an ECOG PS of 0 or 1 at baseline.

8. Patients with haematopoietic, hepatic, renal, cardiac and respiratory functions thatmeet certain criteria in a baseline test.

<Additional Inclusion Criteria for Part 1a

1. Patients with pathologically diagnosed advanced or metastatic solid tumors.

<Additional Inclusion Criteria for Part 1b

1. Patients with pathologically diagnosed with advanced or metastatic esophagealcancer, or advanced or metastatic head and neck cancer whose primary site of originis the oral cavity, oropharynx, hypopharynx, larynx, nasal cavity, or paranasalsinuses.

2. Patients with pathologically diagnosed squamous cell carcinoma.

3. Patients who agree to undergo tumor biopsy after administration.

<Additional Inclusion Criteria for Part 2a

1. Patients with pathologically diagnosed with advanced or metastatic esophagealcancer.

2. Patients with pathologically diagnosed squamous cell carcinoma.

3. Patients who agree to undergo tumor biopsy after administration.

<Additional Inclusion Criteria for Part 2b

1. Patients with advanced or metastatic head and neck cancer whose primary site oforigin is the oral cavity, oropharynx, hypopharynx, larynx, nasal cavity, orparanasal sinuses.

2. Patients with pathologically diagnosed squamous cell carcinoma.

3. Patients who agree to undergo tumor biopsy after administration.

Exclusion Criteria:

<Common Exclusion Criteria to Part 1 and Part 2>

1. Patients with central or brain pia mater metastases that are untreated andsymptomatic or that require treatment.

2. Patients with concurrent multiple or synchronous cancers, or with iatrogenicmultiple or synchronous cancers with a disease-free interval of 5 years or less.

3. Patients receiving continuous systemic administration of steroids or otherimmunosuppressive drugs.

4. Patients who have had a Grade 3 or higher allergic reaction to an antibody agent oran additive of the study drug.

5. Patients who have not recovered to Grade 1 or below from adverse events caused bypreviously administered anticancer therapy.

6. Patients with active interstitial lung disease or a history of active interstitiallung disease.

7. Patients with infectious diseases requiring systemic treatment.

8. Patients with a fever of 38.0°C or higher at the time of registration.

9. Patients who test positive for Hepatitis B virus antigen or antibody, Hepatitis Cvirus antibody, or HIV antibody in a baseline test.