Pembrolizumab in Progressive Multifocal Leukoencephalopathy (PML) in Immunocompromised Patients Without HIV Infection

Inclusion criteria

• Age ≥ 18 years old
• Diagnosis of definite PML since less than 2 months according to American Academy of Neurology
• Presence of JCV in the CSF in the last CSF sampling.
• Signed informed consent (from the patient, or if unable to consent, from a surrogate)
• For women of childbearing potential: negative serum or urine b-HCG test and agree to use a highly effective contraception methods during 8 months (i.e. until 6 months after end of experimental treatment)

Exclusion criteria

• Patients in whom immune reconstitution is achievable (HIV infection - Multiple sclerosis - Auto-immune and inflammatory diseases)
• Patients who have received solid organ transplantation
• Hypersensitivity to the active substance or to any of the excipients
• Life expectancy less than 1 month
• Pregnancy or lactating women or planning birth during the study period
• Having previously been treated by anti-PD1mAb
• Patient receiving IL-2 or IL-7 for the treatment of PML at inclusion
• Patient whose weight is > 100kg
• Participation in other interventional study [a patient already included in another interventional study for which the treatment can lead to an immunodepression can be included if:

• the investigational treatment has been completed and there is no risk of drug interaction with the administration of Pembrolizumab as defined in PENALTY study
• if this does not alter the study's ability to evaluate the effect of Pembrolizumab in terms of safety and efficacy (from the investigator's point of view)]
• Patient without national health insurance, and patient on AME (state medical aid)
• Patient under guardianship or curatorship
• Patient deprived of their liberty by a judicial or administrative decision