Psoriasis is an inflammatory skin disease with huge negative impact on the quality of life of
the patients, and has an overall prevalence of 2% to 3% in the general population. Plaques
psoriasis is the most common type of the disease and presents red, well demarcated, and
silvery plaques mainly localized in the umbilical and lumbosacral area as well as in the
elbows, knees, and scalp. The major histological features of psoriasis include epidermal
hyperplasia with aberrant keratinocyte differentiation, pronounced inflammatory cell
infiltration and increased vascularization. Currently, pharmacological treatments such as
retinoids, corticosteroids, and vitamin D analogs remain the main options for most psoriasis
patients. However, the efficacy of conventional drugs is limited because of adverse side
effects and the development of pharmacoresistance. Recently, biologics have become available
for the treatment of acute and subacute plaque psoriasis with excellent response rate.
However, the high costs involved with the biologics have barred many ordinary psoriasis
patients from benefiting from this new class of anti-psoriatic medication. Natural products
are valuable sources in novel drug development. Inflammatory skin disease formula (ISDF) is
an empirical formula of the Principal Investigator (Prof. Zhi-Xiu Lin), a highly experienced
Registered Chinese Medicine Practitioner and Chinese medicine dermatologist working at the
School of Chinese Medicine, The Chinese University of Hong Kong. ISDF has been prescribed in
clinic in Hong Kong for many years and observed to be effective in relieving atopic
dermatitis and psoriasis patients' clinical manifestations. ISDF contains nine Chinese herbal
medicines, including Rehmanniae Radix (Dihuang) 20.0 g, Paeoniae Radix Rubra (Chiyao) 10.0 g,
Scutellariae Radix (Huangqin) 10.0 g, Phellodendri Cortex (Huangbai) 10.0 g, Forsythiae
Fructus (Lianqiao) 12.0 g, Plantaginis Semen (Cheqianzi) 10.0 g, Vignae Semen (Chixiaodou)
10.0 g, Dictamni Cortex (Baixianpi) 10.0 g and Kochiae Fructus (Difuzi) 10.0 g. Among them,
Rehmanniae Radix is frequently used for the treatment of psoriasis in Chinese medicine.
Paeoniflorin, the major active ingredients of Paeoniae Radix Rubra, has been reported to
inhibit imiquimod (IMQ)-induced psoriasis in mice by regulating Th17 cell response and
cytokine secretion. Baicalin, the active components of Scutellariae Radix, was able to
improve the psoriasis-like skin lesions induced by IMQ or 2,4-dinitrofluorobenzene (DNCB) in
mice. Berberine, the main alkaloid of Phellodendri Cortex, could inhibit IMQ-induced
psoriasis-like skin lesions and upregulation of CDC6 and p-STAT3 in mice.
Recent study demonstrated that ISDF (named SZF in the study) markedly decreased the epidermal
thickening and infiltration of mast cells in the ears and dorsal skin of the DNCB-treated
mice via inhibition of inflammation through inactivation of NF-κB p65 pathway. The ISDF was
found to contain baicalin (4.92%, w/w), berberine (2.90%, w/w), paeoniflorin (0.26%, w/w) and
phillyrin (0.10%, w/w). Recent preliminary data revealed that ISDF significantly improved the
psoriatic-like symptoms and reduced the epidermal thickening in the dorsal skin of
IMQ-stimulated mice via inhibition of the inflammation response. The results on its acute
toxicity demonstrated that ISDF at up to the dose of 37.8 g/kg, which was the maximum
tolerable dose of ISDF in mice, did not exert any overt toxicity. Based on these positive
findings of pilot study, the investigators therefore hypothesize that ISDF is an effective
herbal formula with anti-psoriatic effects. In Chinese medicine (CM) theory, psoriasis may be
classified into different subtypes or "syndromes", including syndrome of wind-heat and blood
heat, which is also known as blood heat syndrome or syndrome of wind-heat and blood dryness;
syndrome of blood deficiency and wind-dryness; syndrome of blood stasis in the skin; and
dampness-heat syndrome. Each of these syndromes represents a different pathogenesis in CM and
corresponds to a different stage or manifestation of psoriasis. ISDF is composed of herbal
medicines that can clear heat to cool the blood, clear heat and dry dampness, clear heat and
drain dampness, disperse wind-heat, and is suitable for treating psoriasis with wind-heat,
blood heat or dampness-heat. A randomized, double-blinded, placebo-controlled trial will be
conducted to evaluate the efficacy of ISDF on psoriasis patients. Clinical evidence for the
anti-psoriatic effects of ISDF, and is a necessary step towards developing this Chinese
medicine formula into an anti-psoriatic pharmaceutical agent.