A randomized, open-label, monocentric clinical phase I/IV study in healthy human volunteers to evaluate the skin tolerability and cosmetic acceptance of three marketed anti-acne drugs (Differin® Creme, Erylik® Gel, and Zindaclin® 1 % Gel)

INTERVENTION: Trade Name: Differin Creme Product Name: Differin Creme Pharmaceutical Form: Cream INN or Proposed INN: Adapalene CAS Number: 106685‐40‐9 Concentration unit: mg/g milligram(s)/gram Concentration type: equal Concentration number: 1‐ Trade Name: Erylik Product Name: Erylik Pharmaceutical Form: Gel INN or Proposed INN: Erythromycine CAS Number: 114‐07‐8 Concentration unit: % (W/W) percent weight/weight Concentration type: equal Concentration number: 4‐ INN or Proposed INN: Tretinoin CAS Number: 302‐79‐4 Concentration unit: % (W/W) percent weight/weight Concentration type: equal Concentration number: 0.025‐ Trade Name: Zindaclin 1% Gel Product Name: Zindaclin 1% Gel Pharmaceutical Form: Gel INN or Proposed INN: Clindamycin dihydrogenphosphate CAS Number: 24729‐96‐2 Concentration unit: mg/g milligram(s)/gram Concentration type: equal Concentration number: 11.88‐ CONDITION: PRIMARY OUTCOME: Main Objective: The objective of this study is the evaluation of skin tolerability and cosmetic acceptance of three marketed anti‐acne drugs in panelists (healthy volunteers) with healthy but mixed to oily skin. The aim is to find out the best tolerated and accepted formulation for a new anti‐acne drug. Primary end point(s): Assessment of Tolerability; Dermatological assessment of tolerability for subjective (itching, burning, tension, tickling, feeling of dryness, other) and objective (erythema, dryness, scaling, fissures, papules, pustules, edema, vesicles, weeping, other) dermatological parameters. This assessment will be performed before the first application of each product on study days 1, 8 and 15 and after the last application of each product on study days 5, 12 and 19 (end of study). Additionally the panelists will evaluate the overall skin tolerability of the test products on study days 5, 12 and 19.; ; Assessment of Cosmetic Acceptance; Before the first product application on study day 1 the panelists will be asked about the importance of product traits in general. Furthermore the texture, fragrance, application, spreading, stickiness, oiliness, greasiness, penetration, and the overall acceptance of the test products will be evaluated by the panelists immediately after each first application of the substances (days 1, 8, and 15). Secondary Objective: INCLUSION CRITERIA: •men and women with healthy but mixed to oily skin •between 18 and 50 years of age •willingness to actively participate in the study and to come to the scheduled visits •panelist is capable of understanding the purpose and risks of the study, has been fully informed and has given written informed consent to participate in the study •willingness to use test products once daily on facial skin throughout the course of the study and to refrain from use of other skin care products like creams or lotions for the facial skin two days before the start of the study and during the course of the study •willingness to continue with the normally used facial cleansing products and decorative cosmetics and to refrain from changing brands throughout the course of the study •willingness to refrain from decorative cosmetics (e.g. mascara, make‐up, cover cream, etc.) in the morning before the initial visit as well as before the final visit •signed written con