Cytoflavin in the Treatment of Patients With Diabetic Polyneuropathy

Inclusion Criteria: * Signed informed consent form; * Men and women aged 45 to 74 (inclusive); * Confirmed diagnosis of type 2 diabetes lasting for 1 year or more; * Permanent scheme of therapy (without changing doses and drugs) by oral hypoglycemic drugs and / or insulin, long-term or ultra-long (adjustment of insulin dose is possible within 10% from baseline dose) and / or agonists of glucagon-like peptide-1 receptors (GLP-1) for at least 12 weeks before screening; * HbA1c from 7.0 and not higher than 10.0%; * BMI 22-40 kg / m2; * Symptomatic distal sensorimotor diabetic polyneuropathy; * Baseline TSS (Total Syptom Score) ˃5 points; * Score ≥2 by at least one of the TSS symptoms; * The severity of pain by the corresponding TSS subscale ≤ 2; * NISLL (Neuropathy Impairment Score Low Limbs) ≥ 2 points; * Patient consent to use adequate contraceptive methods for the entire study; * Consent to maintain a stable diet, exercise, therapy and diabetes control throughout the study; * Ability to comply with all protocol requirements. Exclusion Criteria: * Pregnant or lactating women, or women planning a pregnancy during a clinical trial; * Type 1 diabetes and other specific types of diabetes; * Acute metabolic complications of diabetes such as ketoacidosis or hyperosmolar state within 6 months prior to screening; * Therapy with short and ultra-short insulin within 3 months before screening; * Fasting plasma glucose at screening\> 15 mmol / l; * The presence of severe complications of diabetes; * Epilepsy, epileptiform seizures, head trauma with loss of consciousness, tumor, inflammatory and demyelinating diseases of the central nervous system; * Diseases requiring prior or current treatment by systemic corticosteroid drugs, cytostatics or penicillamine;malignant neoplasms within the last 5 years (excluding basal cell carcinoma); * Cardiovascular diseases in the stage of decompensation at present or within 3 months before screening; * Uncontrolled arterial hypertension with systolic arterial pressure\> 180 mm Hg and diastolic blood pressure\> 110 mm Hg at screening; * Nephrotic syndrome, severe chronic renal failure or significant kidney disease with a level of glomerular filtration rate (GFR) \<30 ml / min; * Active viral (hepatitis B and C) or cirrhotic liver disease; increased aspartate aminotransferase (AST) or serum alanine aminotransferase (ALT) 3 times from upper normal limit; increased total bilirubin 2 times from upper normal limit; * HIV; a severe infectious disease within 30 days before screening; * Anemia (hemoglobin ≤ 105 g / l in women or ≤ 115 g / l in men); acute blood loss or donation of at least one unit of blood (500 ml) or blood transfusion within the previous 12 weeks; * Drug or alcohol abuse; * Intake of Cytoflavin® for 3 months before screening; * Known allergies, hypersensitivity or contraindications to the drug Cytoflavin® or its components; * Intake of alpha-lipoic acid, thiamine derivatives, pyridoxine, cyanocobalamin (excluding multivitamins), antidepressants and derivatives of gabapentin within 3 months before screening; * Use of other investigational drugs within 3 months prior to screening; * Inability to read or write; unwillingness to understand and follow protocol procedures; non-compliance with the protocol requirements.