Cheng HM, et al. – This paper aspired to assess the pharmacological effect of Indigo naturalis as a single topical agent (topical ointment) in Chinese patients with moderate plaque–type psoriasis. The clinical efficacy of Indigo naturalis in moderate psoriasis was illustrated here. This study also exemplified a novel experimental medicine approach in order to comprehend the Traditional Chinese Medicine (TCM) targeting mechanisms.

Methods

• The design of this research was a randomized, double-blind, placebo-controlled clinical study.
• It inspected the Indigo naturalis as a topical monotherapy to treat moderate plaque psoriasis in a Chinese cohort (n = 24).
• Patients were treated with Indigo naturalis ointment (n = 16) or matched placebo (n = 8) twice daily for 8 weeks, with 1 week of follow-up.

Results

• At week 8, marked improvements were noted in Psoriasis Area and Severity Index (PASI) scores from baseline, in Indigo naturalis-treated patients (56.3% had 75% improvement [PASI 75] response) compared with placebo (0.0%).
• A gene expression signature of moderate psoriasis was established from baseline skin biopsies.
• This, in turn, incorporated the up-regulation of the interleukin (IL)-17 pathway as a viatl aspect.
• The Indigo naturalis therapy caused maximum of these signature genes returning toward normal, including down-regulation of the IL-17 pathway.
• With the aid of an in vitro keratinocyte assay, an IL-17-inhibitory effect was brought to light for tryptanthrin, a component of Indigo naturalis.