This is a randomized, double-blinded, Phase 2 trial in patients with PML due to JCPyV. Patients will receive treatment with a matched virus-specific T-cell product (CE VST01-JC) or placebo, and will then be monitored for response to therapy.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by JC polyomavirus (JCPyV) occurring in immunocompromised patients who face a disease that is usually progressive and often fatal (Padgett 1971; Tan 2010). Annually, it is estimated that 4,000 people develop PML in the United States and Europe combined (NORD 2015).

This is a randomized, double- blinded, Phase 2 trial in patients with PML due to JCPyV. Patients will receive treatment with a matched virus-specific T-cell product (CE VST01-JC) or placebo, and will then be monitored for response to therapy. The study is designed to evaluate whether CE-VST01-JC infusions will slow and ultimately halt neurological progression in patients with PML compared with placebo as evaluated by modified Rankin Score (mRS).

• Male or female subjects aged 18 years or older, with actively progressing PML confirmed by MRI and JCPyV present in CSF or in brain biopsy tissue (diagnosis confirmed according to algorithm diagnostic criteria for PML developed by the American Academy of Neurology).