Clinuvel Pharmaceuticals (ASX:CUV) said patient case studies from its ongoing CUV105 study in vitiligo showed repigmentation after 20 weeks of therapy with its drug candidate afamelanotide and adjunct narrowband ultraviolet B phototherapy, according to a Thursday filing with the Australian bourse.

Vitiligo is a skin disorder that causes the skin to lose pigment.

Data also showed the maintenance of pigmentation in patients with darker skin types after the withdrawal of therapy for up to six months, the company said.

A longer-term follow up study with topical ruxolitinib showed that patients who respond to therapy but withdraw from treatment after 52 weeks see high rates of relapse.

In the same filing, the company said analyses of five years of treatment with afamelanotide for epidermal pigmentation in erythropoietic protoporphyria patients in 104 patients confirmed that afamelanotide had no reported effect on malignant transformation or naevi. No drug-related malignancies have been reported after more than 21,000 doses administered.

Clinuvel Pharmaceuticals' shares fell almost 6% in recent trading on Thursday and earlier reached an eight-year low.