Dose-response Relationship Study of S42909 on Leg Ulcer Healing

S42909 is an inhibitor of β-Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase which also inhibits vascular leukocyte adhesion to endothelial cells, Matrix Metalloproteinase-2 (MMP-2) and Plasminogen Activator Inhibitor-1 (PAI-1) activity. It is proposed for development in the treatment of venous and mixed leg ulcers. This proof of concept study is a randomized, double-blind, placebo-controlled, multicenter, Phase IIa trial to evaluate the dose response of S42909 for the treatment of venous leg ulcers. Patients suffering from chronic venous disease and having at least one active venous leg ulcer will be selected at the selection visit (ASSE). One Reference Ulcer (RU) defined as the largest ulcer in size that is fitting the area selection criteria will be established. At ASSE, a first picture will be taken before cleansing and debridement and a second picture will be taken after cleansing and debridement. The investigator will check that the selection RU area is compliant with the selection criteria. Patients will start the selection period and will be switched from their current pharmacological and/or local treatment (if any) for venous leg ulcer to local wound care with sterile saline solution or sterile water, "non-active" dressings and standardized compression (same strength and type of compression). They will be administrated the placebo selection treatment for a period of fourteen days. Three (or four) working days before the inclusion visit, the participants will come to the site for a RU picture in order to get the RU area central measurement for inclusion visit (W000). At W000, the investigator will check that the inclusion RU area is compliant with the inclusion criteria. The investigator will also check that the participant is compliant with the selection treatment and stockings wearing. All participants found to be eligible for inclusion will be randomized to one of the following six groups - S42909: 100, 200, 400, 800 or 1200 mg per day- or placebo. The participants will enter a 6 weeks ambulatory Investigational Medicinal Product (IMP) treatment period on top of standard of care (standardized compression and local wound care with sterile saline solution or sterile water and "non-active" dressing) followed by a 2 weeks follow-up period of standard of care only. During this period the participants will return to the investigator's site for intermediate visits after one week (W001), two weeks (W002), three weeks (W003), four weeks (W004), six weeks (W006) and eight weeks (W008). Participants will continue receiving standardized compression therapy and local wound care (sterile saline solution or sterile water and "non-active" dressing) until the end of the study (W008).