Table 1 Inclusion and exclusion criteria

1. Patients who have a diagnosis of generalised chronic plaque and/or guttate psoriasis

1. Patients with photosensitive disorders

2. Male and female patients aged between 18 and 75 years inclusive

2. Patients with diabetes mellitus

3. Patients with a PASI of 7 or greater at screening or baseline despite use of topical therapies

3. Patients who are receiving medications that can cause photosensitivity

4. Patients who are due to undergo NB-UVB light therapy

4. Patient who are receiving GLP-1 analogue therapy

5. Patients who have not required systemic psoriasis therapy during the past 8 weeks

5. Patients who have conditions that could be made worse by phototherapy (cataracts, epilepsy, etc.)

6. Patients who are unlikely to require systemic therapy for the duration of clinical trial involvement

6. Patients with allergy or hypersensitivity to Januvia^®

7. Patients who have a negative pregnancy test at screening (women of child-bearing potential only)

7. Patients with any of the following conditions:

severe kidney disease (estimated glomerular filtration rate of less than 30 ml/min/1.73 m²)

severe heart disease (left ventricular ejection fraction less than 35 %)

severe liver disease (alanine aminotransferase greater than 150 IU/L)

severe lung disease (forced expiratory volume in 1 second or a forced vital capacity that is known to be less than 50 % of that estimated for a person of that age and gender)

8. Patients who are willing to sign voluntarily a statement of informed consent to participate in the study

8. Patients who have received NB-UVB light recently (within 8 weeks)

9. Patients who are receiving currently or have received systemic therapy for psoriasis recently (within 8 weeks)

10. Patients who have any other contraindications to Januvia^® as stated in its Summary of Product Characteristics

11. Female patients of child-bearing potential who are pregnant, breastfeeding, or unwilling to practice an acceptable barrier and/or hormonal method of contraception during participation in the study – abstinence will be permitted only if it is in keeping with a person’s lifestyle

12. Patients with any clinically significant chronic disease that might, in the opinion of the investigator, interfere with the evaluations or preclude completion of the trial

13. Patients with a current or recent (within the past 4 weeks) acute serious illness, acute psychiatric illness or severe uncontrolled/unstable illness

14. Patients who have been randomised into this study previously

15. Patients who are participating in another clinical trial concurrently

16. Patients who are participating in another clinical trial during the 12 weeks prior to study entry (i.e. screening visit)