Randomized, Placebo-crontrolled Clinical Trial Evaluating the Efficacy and Safety of Heparan Sulfate 120 mg Prolonged-Release Tablets Compared With Placebo in Patients With Chronic Venous Disease

Inclusion Criteria: * Participants with an age ≥ 18 and ≤ 80 years * Diagnosed primary venous disease of the lower limbs in stage C2 - C5 according to the CEAP classification, involvement of the venous system of the lower limbs is verified by duplex ultrasonography * Presence of objective signs and subjective symptoms of the disease (classified according to rVCSS score ≥ 4) * Participants not using or planning to use compression therapy by their own decision * Provision of written informed consent as approved by the Ethics Committee (EC). Exclusion Criteria: * Use of a venoactive drug in the last month * Regular use of compression therapy or use of mechanical devices for reduction of edema in the last month * Heart Failure (NYHA class III and IV), congestive heart failure with peripheral edema * eGFR \< 30 mL/min/1.73 m² at screening or chronic kidney disease documented in the medical history * ALT or AST more than 3 times the upper limit of normal range at screening or advanced liver disease documented in the medical history * Deep venous thrombosis lower limb thrombosis and / or documented residual venous obstruction or deep venous reflux due to post-thrombotic alterations in the deep venous system * Superficial venous thrombosis of the lower limbs in the previous 6 months * Congenital venous/lymphatic malformation * Neuropathy of any aetiology * Diabetic foot syndrome * Refractory (uncontrollable) hypertension (inability to therapeutically achieve a systolic blood pressure ≤ 160 mmHg or a diastolic blood pressure ≤ 100 mmHg) * Symptomatic ischemic disease of lower limbs * Lymphoedema: primary, posttraumatic, postoperative, post-radiation, malignant * Manual/instrumental lymphatic drainage in the last 3 months * Invasive procedure on the lower limbs in the last 6 months * Trauma of the lower extremity that has not fully healed * Use of oral/parenteral anticoagulants * Use of dual antiplatelet therapy * Use of loop diuretics * Use of oestrogens or progesterone and its derivates -. Use of oral/parental corticosteroids in the last 6 weeks * Chronic pain treatment ≥ 14 days * Use of psychopharmaceuticals affecting fluid retention (antipsychotics, combined antidepressants) * Severe obesity (BMI \> 40 kg/m2) * Participants with active malignant disease or malignant disease in remission for less than 5 years * Myeloproliferative or immune disorders * Contraindications to the IMP/Placebo administration * Hypersensitivity to the IMP/Placebo excipients. General Conditions * Pregnant or breastfeeding women * Women of child-bearing potential not using at least one effective contraceptive method for the entire trial * Participation in other investigational drug or device clinical trials within 30 days prior to study screening -. Participants legally or mentally incapacitated unable to give informed consent for the participation in this trial * Participants unable or unwilling to comply with appointments or all protocol requirements.