PD-1 Inhibitors Maintenance for cHL Post-autoHCT

Inclusion Criteria: * 18-70 years; * Diagnosis of r/r cHL with auto-HCT being performed as consolidation of 2 or later therapy lines; * High-risk cHL (Primary refractoriness after first-line therapy / Relapse after first line therapy within 12 months / PET/CT-positive status at the time of auto-HCT / Late relapse (\> 12 months) with unfavourable prognosis factors (extranodal lesion and/or bulky and/or B-symptoms) / More than one salvage regimen performed) * Complete or partial response by PET/CT after auto-HSCT * No evidence of grade 3-4 adverse events (CTCAEs) after auto-HCT at the time of inclusion in the study; * Achieved recovery of peripheral blood counts after auto-HSCT (white blood cell count\> 1 109/L, absolute neutrophil count\> 0.5 109/L, platelets \> 25 109/L); * ECOG 0-2; The decision to include patients that do not fulfil the criteria of hight-risk cHL is made in consultation with the PI Exclusion Criteria: * Patients who have received PD1-inhibitor therapy in the previous lines of treatment and had to interrupt treatment early due to the development of adverse events of therapy; * Severe organ failure: creatinine values more than 2 ULN; ALT, AST more than 5 ULN; bilirubin more than 1.5 ULN; * Respiratory failure of more than 1 degree at the time of inclusion in the study; * Unstable haemodynamics at the time of inclusion in the study; * Acute bacterial, viral or fungal infection at the time of inclusion; * Active autoimmune diseases (subjects with type 1 diabetes mellitus and hypothyroidism requiring only hormone replacement therapy, and skin diseases such as vitiligo, allopecia, or psoriasis that do not require systemic therapy may be eligible); * Pregnancy or breastfeeding, or planning pregnancy or parenthood during the study period; * Somatic or psychiatric pathology that prevents the signing of informed consent;