An Open Prospective Randomized Clinical Study of the Effectiveness, Tolerability and Safety of a Single Intraperitoneal Use of the Drug "Prospidelong, Powder for the Preparation of a Gel for Topical Use, 1000 mg in Vials, Package No. 1" in Patients With Disseminated Gastric Cancer, Phase I-II

Inclusion Criteria: * Gastric cancer without transition to the esophagus with peritoneal dissemination sT1-4N0-3M1. * Life expectancy of at least 6 months * Physical status on the ECOG scale 0 - 1. * The age of patients is from 18 to 75 years. * Absence of severe concomitant diseases in the decompensation stage. * Availability of written informed consent from the patient to participate in the study. * The ability of the patient and the personnel caring for him to comply with the instructions of the research physician and comply with the study design. Exclusion Criteria: * Pregnancy and lactation. * The presence of a primary multiple (synchronous or metachronous) malignant tumor. The exception is for patients who were treated for basal cell or squamous cell skin cancer, cervical cancer in situ, or other tumors more than 5 years ago and are expected to be completely cured. * Presence of severe concomitant diseases in the stage of decompensation; * Family relationships between the patient and the center staff. * Allergy to components of the study drug. * Refusal of the patient from the proposed treatment method. * Presence of heart disease class III or IV according to the New York Heart Association classification or a history of myocardial infarction within 6 months before the 1st day of the study. * Any history of epileptic seizures. * Severe diseases, including those with severe symptoms, untreated inflammatory and infectious processes, due to which the patient cannot receive treatment in accordance with the study protocol. * Chronic liver and/or kidney failure. * Legal incapacity or other circumstances due to which the patient or his immediate family are unable to understand the nature, scope and possible consequences of the treatment being carried out * Socioeconomic or geographic circumstances that cannot guarantee adequate compliance with protocol requirements for treatment and follow-up. * History of abuse of alcohol or any chemical substances for 2 years up to the 10th day before the start of the study. * Patient participation in another clinical trial. Non-inclusion criteria based on survey data: * Acute bleeding from the tumor. * Level of peripheral blood leukocytes less than 1.5 × 109 per l, platelets less than 75.0 × 109 per l. * Hemoglobin less than 80g per l. * Positive tests for human immunodeficiency virus (HIV), hepatitis B or hepatitis C. * Severe liver dysfunction - AST and ALT levels exceed the upper limit of normal by 5 times or more, bilirubin greater than or equal to 2.0 mg per dL (34.2 µmol per L). * Severe renal impairment - creatinine clearance less than 30 ml per minute, calculated using the Cockcroft-Gault formula - or the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula. * Diabetes mellitus in a state of clinical and metabolic decompensation. Criteria for exclusion (dropout) from the study: * Individual intolerance to drugs included in the treatment regimen. * The patient's desire to stop participating in the study. * Serious adverse events occurring in the patient during the study. * Violation by the patient of the research conditions of the investigational medicinal product (non-compliance). * Pregnancy. * Detection of a second malignant tumor