Background:

PPA-904 is a specific phenothiazine photosensitizer used in photodynamic therapy.

Topical PPA904 photodynamic therapy is a promising treatment for cutaneous leishmaniasis. The best curative PPA904-photodynamic therapy regimen is achieved under the conditions of a longer duration of topical application time (90 minutes) and several (three) consecutive treatments with 4-day intervals between treatments[1]. PPA904-PDT can provide an immunomodulating, dose-dependent efflux on IL-12p70 production. This mechanism could be responsible for promoting a more rapid healing in PPA904-PDT treated mice[2]. Treatment of PPA904 is well tolerated with no reports of pain or other safety issues. PPA904 treated subjects show a reduction in bacterial load immediately post-treatment. After 3 months, 50% (four of eight) of subjects with actively treated chronic leg ulcer show complete healing, compared with 12% (one of eight) of subjects on placebo[3].

[1]. Akilov OE,et al. Optimization of topical photodynamic therapy with 3,7-bis(di-n-butylamino)phenothiazin-5-ium bromide for cutaneous leishmaniasis. Lasers Surg Med. 2009 Jul;41(5):358-65. [2]. Akilov OE, et al. Photodynamic therapy for cutaneous leishmaniasis: the effectiveness of topical phenothiaziniums in parasite eradication and Th1 immune response stimulation. Photochem Photobiol Sci. 2007 Oct;6(10):1067-75. [3]. Morley S, et al. Phase IIa randomized, placebo-controlled study of antimicrobial photodynamic therapy in bacterially colonized, chronic leg ulcers and diabetic foot ulcers: a new approach to antimicrobial therapy. Br J Dermatol. 2013 Mar;168(3):617-24.