Efficacy and Safety of a Botanical Total Coumarin (TC) Cream in Treating Patients With Psoriasis Vulgaris (PLANTCOAT-IIb Trial)

Inclusion Criteria: * Age of 18-70 years old. Both men and women and members of all races and ethnic groups * Consistent with diagnostic criteria of stable phase psoriasis vulgaris and have at least two target lesions suitable for evaluation * Women of childbearing age must be using birth control strategies defined by one of the following: 1) a barrier method (condom) and/or 2) oral contraceptives, during the 8-week study period. * ISGA score ≥ 2 (at least mild severity) * BSA (stable stage group): 1%≤ to ≤20% * Signed a written informed consent document * No additional exposure to the sun Exclusion Criteria: * Subjects in pregnancy, preparing for pregnancy or breast feeding * History of hyperergic or photosensitivity * History of complicated cardiovascular diseases, cerebrovascular diseases, severe primary diseases of hepatic, kidney and hematopoietic system, or patients with psychiatric disorders * History of photosensitive diseases such as porphyria, chronic actinic dermatitis, Xeroderma pigmentosa * Within 4 weeks prior to randomizations, patients have taken treatment with following approved or investigational psoriasis therapies on the target lesions: * Topical treatments * PUVA, UVB or Grenz ray therapy. * Any systemic treatments other than biologicals with a possible effect on psoriasis (e.g., corticosteroids, vitamin D analogues, hydroxycarbamide, azathioprine, methotrexate, cyclosporine, other immunosuppressant). * Any types of other investigational therapies for psoriasis * Within 3 months prior to randomizations, patients have taken systemic treatments with retinoids or biological therapies (marketed or otherwise) with a possible effect on psoriasis (e.g., alefacept, efalizumab, etanercept, infliximab). * Planned initiation of, or changes to, concomitant medications that could affect psoriasis (e.g., beta blockers, anti-malaria drugs, lithium) during the double-blind phase of the study. * History of allergic reactions attributed to compounds of similar chemical or biologic compositions to Coumarins.