The aim of the study is to assess safety, tolerability and preliminary efficacy of XSTEM-VLU when administered as a single topical dose to patients with difficult-to-heal venous leg ulcers. The study is randomised and the patients will receive either XSTEM-VLU or vehicle as add on to standard wound care.

The patients will be followed weekly for 10 weeks after treatment. At 4 months after treatment, the patients will return to the clinic for an end-of-study visit.

Major Inclusion Criteria:

• Written informed consent for participation in the study
• Male or female patient aged ≥18 years
• BMI ≥18.5 and ≥40.0 kg/m2
• Lower leg wound due to venous insufficiency
• Target wound has failed to heal despite standard wound care for a minimum of 6 weeks
• A surface area of the target wound of ≥2 and ≤40 cm2

Major Exclusion Criteria:

• Signs or symptoms of clinically significant ongoing infection i the target wound requiring anti-microbial treatment
• History of autoimmune disease, such as but not limited to systemic lupus erythematosus, Addison's disease, Crohn's disease and type I diabetes mellitus
• B-HbA1C value ≥52 mmol/mol
• Plaque psoriasis or any other skin disease that could interfere with the outcome of the study
• Arterial insufficiency
• History of any malignancy within the past 5 years
• Target wound diagnosed as a malignant wound, neuropathic wound, pressure wound or osteomyelitis
• Patients who are immunocompromised due to disease or for other reasons such as the use of systemic immunosuppressants