Safety, Tolerability, PK, PD and Preliminary Efficacy of ONO-4685

Inclusion Criteria

1. Subjects must be willing and able to participate in the study
2. A diagnosis of plaque-type psoriasis for ≥6 months.
3. Plaque-type psoriasis involving ≥3% of body surface area (BSA) (Parts B and C).
4. Willing to provide skin biopsies (Parts B and C).
5. Subjects in good health, as judged by medical history, medical examination, vital signs, ECG and clinical laboratory tests.
6. Subjects willing to comply with the contraception and sperm and ova donation requirements of the protocol.

Exclusion Criteria

1. Subjects with any clinically significant abnormality in screening tests.
2. Guttate, erythrodermic or pustular psoriasis as sole or predominant form of the psoriasis, or other skin condition (eg eczema).
3. Presence or history of alcohol or drugs abuse.
4. Heavy smokers (more than 20 cigarettes or use more than ½ ounce (12.5 grams) of tobacco each day).
5. Subjects have had any 'live' vaccines (excluding COVID-19 vaccine) during the 3 months before the first dose of study medicine.
6. Subjects have had a first COVID-19 vaccine within 6 weeks or second and booster COVID-19 vaccinations within 2 weeks before the first dose of study medicine.
7. Subjects have had any clinically significant disease or infection, including tuberculosis.
8. Presence or history of malignancy (cancer) including lymphoproliferative disorders.
9. Subject is pregnant, lactating, or breastfeeding.
10. Subjects have received treatment with biologics in the last 3 months, immunosuppressant medicine or prescription medicine for psoriasis within 4 weeks before admission to the ward; have used phototherapy from 2 weeks before admission to the ward; have used highly potent or potent topical steroids within 2 weeks before admission to the ward.
11. Subjects have used topical corticosteroids or Vitamin D analogues within 7 days before admission to the ward (Parts B and C).