• Histologically confirmed classical HL (according to the latest version of the WHO classification).

• Primary refractory to first line chemotherapy, or in first relapse after any polychemotherapy regimen (e.g. ABVD, baseline BEACOPP or escalated BEACOPP, or other induction regimens).

• In case of relapse, the relapse must be histologically confirmed. In case histologic biopsy is not possible, at least confirmation of the relapse by fine needle aspirate (FNA) or sequential imaging is required.

• Measurable disease, based on Lugano criteria 2014 \[40\]; i.e. CT scans showing at least 2 or more clearly demarcated lesions with a long axis ≥ 1.5 cm and a short axis diameter ≥ 1.0 cm, or 1 clearly demarcated lesion with a long axis ≥ 2.0 cm and a short axis diameter ≥ 1.0 cm. These lesions must be FDG-PET-positive.

• Age 18-70 years inclusive.

• WHO/ECOG Performance Status ≤ 1 (see appendix C).

• No major organ dysfunction, unless HL-related:

‣ Total bilirubin \< 1.5x ULN (unless due to lymphoma involvement of the liver or a known history of Gilbert's syndrome; in that case bilirubin may be elevated up to 3 x ULN).

⁃ ALT/AST \< 3x ULN (unless due to lymphoma involvement of the liver; in that case ALT/AST may be elevated up to 5 x ULN).

⁃ GFR \> 60 ml/min as estimated by the Cockcroft\&Gault formula.

• Adequate BM function defined as:

‣ Absolute neutrophil count ≥ 1.5x109/L, unless caused by diffuse bone marrow infiltration by the HL.

⁃ Platelets ≥ 75 x109/L, unless caused by diffuse bone marrow infiltration by the HL.

⁃ Hemoglobin must be ≥ 8 g/dL (5 mmol/L).

• Resolution of toxicities from first-line therapy.

• Able to adhere to the study visit schedule and other protocol requirements.

• Negative pregnancy test at study entry.

• Female patient is either post-menopausal for at least 1 year before the screening visit or surgically sterile or if of childbearing potential, agrees to practice 2 effective methods of contraception, at the same time, from the time of signing the informed consent through at least 6 months after the last dose of study drug, or agrees to completely abstain from heterosexual intercourse.

• Male patient, even if surgically sterilized, (i.e., status post vasectomy) agrees to practice effective barrier contraception during the entire study period and through 6 months after the last dose of study drug, or agrees to completely abstain from heterosexual intercourse.

• Written informed consent.

• Patient is capable of giving informed consent.