• Relapse rate, as assessed by PASI (Psoriasis Area and Severity Index )score
  

• Time to relapse
  
• Change from baseline in PASI score at every visit and on relapse
  
• Change from baseline in BSA (Body Surface Area) score at every visit and on relapse
  
• Change from baseline in VAS (Visual Analogue Scale) for Patient Self assessment of pruritus at every visit and on relapse
  
• Safety / Tolerability assessed by adverse events
  

Inclusion criteria:

• Outpatients 18 years of age and older (max 65 years)
• Patients with chronic plaque psoriasis on disease remission (i.e. PASI ≤75% of PASI before cyclosporine continuous treatment course) entering a maintenance period
• Disease remission obtained with only cyclosporine as systemic therapy (maximum dose 5 mg/kg/day) for >8 weeks and <16 weeks
• PASI still <75% of PASI before cyclosporine continuous treatment course, at randomization to study treatment (8±2 days after disease remission)

Exclusion criteria:

• Abnormal renal function (creatinine ≥ 10% the upper limit of the reference range)
• Severe chronic degenerative diseases
• Severe uncontrolled hypertension
• Body weigh >110 kg
• Abnormal liver function
• Hyperkalemia or hyperuricemia
• Clinically significant impairment of hematopoietic and cardiovascular function
• Concomitant therapy with nephrotoxic medications
• Patients with malignancy or a history of malignancy
• Females of childbearing potential who are planning to become pregnant, who are pregnant and/or lactating, who are unwilling to use effective means of contraception
• Clinically significant uncontrolled bacterial, viral or fungal infection
• Evidence of drug and/or alcohol abuse