Tolerance of Cyto-selective Difluoroethane-based Cryotherapy in the Treatment of Post-inflamamatory Hyperpigmentation (PIH).

CS5\_2 study aims to evaluate the tolerance of 4 different conditions of cryotherapy treatments applied on dorsal post-inflammatory hyperpigmentation (PIH) spots. This study is a proof of concept, designed to be interventional, monocentric, randomized and double blind. The study will evaluate 4 prototypes : (814A-v1), (814B-v1), (814C-v1) and (814D-v1).

Background: Hyperpigmentation is a problem in all skin types. Safe depigmentation is a challenge. Cryotherapy with liquid nitrogen at -70 °C has been used in the treatment of solar skin lesions for many years but causes considerable damage. Difluoroethane sprays (CRYONOVE) induce skin temperatures from -5 to -15 °C which ablates melanocytes but leaves the other skin cells viable, causing less discomfort and damage. The prototype sprays in this proof of concept study have been proven safe and effective in the treatment of hyperpigmentation (solar lentigines) in Fitzpatrick skin types (FST) I to IV. Although lentigines are uncommon in darker phototypes, hyperpigmentation (PIH and melasma) is a major issue, thus this study seeks to assess the tolerance (acceptability) of the approach in hyperpigmented unexposed dorsal skin. Following the side effects occurring after conventional cryotherapy application, the sponsor has selected other sequences of a specific cryogenic spray which has been used effectively and safely for lentigos treatment in Fitzpatrick Phototypes I to IV, with benefit for the consumers without any adverse safety outcomes. There is therefore a need to test the devices on darker skin types (Fitzpatrick V and VI), which also encounter hyperpigmentation challenges. Design: In this proof of concept study, the sponsor aims to evaluate the tolerance of 4 prototypes of cryogenic spray. Intervention: The prototypes are (814A-v1), (814B-v1), (814C-v1) and (814D-v1) and will be applied on PIH located on the dorsal area. Each treatment corresponds to a specific sequence of a cryogenic spray. 12 subjects will be includes to reach at least 48 brown spots treated. The PIH spots must be between ≥ 3 mm to ≤ 6 mm in diameter. Each spot will be treated by one of a defined prototype (always the same prototype on the same spot all along the study) and will be treated twice during the study with a 15-day interval between each treatment. At D0, D14 for all the prototypes (814A-v1), (814B-v1), (814C-v1) and (814D-v1). The follow up visits will be programmed at D7, D21, D28 and D56 for the end visit. In total this study extends over 8 weeks and involves seven visits (D\<0 (inclusion visit), D0,D7, D14, D21, D28 and D56). Prior to any study device application, the dermatologist will assess the adverse events and will decide if the period between the two applications should be extended or not. The dermatologist will verify that the skin has not been treated by cosmetic products (no presence of cream that could interfere with the treatment) and is dry. An operator previously trained by the dermatologist will apply the study device to the patient's spots. Subjects will be lying on their abdomen to make application more stable, and the treatment will be administered with device.