The purpose of this study is to evaluate the safety and tolerability of ATA188 as a monotherapy in Parts 1 and 2, to determine the recommended Part 2 dose (RP2D) of ATA188 as monotherapy in Part 1, and to evaluate the effect of ATA188 treatment on clinical disability, as assessed by confirmed Expanded Disability Status Scale (EDSS) improvement at 12 months in Part 2 in participants with progressive forms of multiple sclerosis (MS) (primary progressive multiple sclerosis [PPMS] and secondary progressive multiple sclerosis [SPMS]).
A Phase 1/2, Two-part, Open-label Dose-escalation and Double-blind, Placebo-controlled Dose-expansion Study With an Open-label Extension to Evaluate the Safety and Efficacy of ATA188 in Subjects With Progressive Multiple Sclerosis
This is a multicenter, 2 part study in adult participants with progressive forms of MS (PPMS/SPMS) with an open-label, single-arm, sequential dose-escalation period (Part 1) and a double-blind, randomized, placebo-controlled dose-expansion period (Part 2) followed by open-label extension (OLE) period. Part 2 and the OLE have been initiated by the sponsor's discretion based on a review of data from the dose-escalation cohorts.
This study will evaluate the safety and efficacy of ATA188 administered by intravenous (IV) infusion. ATA188 will be selected for each participant based on matching 2 or more human leukocyte antigen (HLA) alleles shared between ATA188 and the participant, at least 1 of which is a HLA-restricting allele.
In Part 1, participants received 2 cycles of ATA188 and entered 12 months follow-up period after the last dose of ATA188. Participants who completed at least the first year of the dose-escalation period and were active in the study have entered the OLE period. In OLE period, participants will receive the same RP2D assigned to Part 2 participants at the time of the Part 1 participant's first dose in each year of the OLE. In OLE period, participants will receive 1 cycle of ATA188 treatment every 12 months (Q12M) for up to 4 years (ie, Years 2 to 5). Otherwise, end of study (EOS) visit will be conducted at 24 months after Cycle 1 Day 1.
In Part 2, participants will be randomized in 1:1 ratio to receive ATA188 at the RP2D or matching placebo, stratified by progressive MS diagnosis (PPMS vs SPMS) and any prior exposure to anti-CD20 therapy (yes vs no). Participants will receive 2 cycles of ATA188 at the RP2D or matching placebo and will be followed for at least 12 months after the first dose of study drug (ie, Year 1). In second year (Year 2), participants who received placebo in Year 1 will receive 2 cycles of ATA188 at the RP2D assigned at randomization and participants who received ATA188 at the RP2D in Year 1 will receive 1 cycle of ATA188 (at the RP2D assigned at randomization) and 1 cycle of placebo to maintain the blind. Participants who complete Year 2 will enter in OLE period to receive ATA188 Q12M for up to 3 years (ie, Years 3 to 5) at the RP2D that was last selected by the sponsor for Part 2. The end of study visit will be scheduled at 5 years (60 months) after the first dose of study drug (ie, Cycle 1 Day 1).
Based on interim analysis, the recruitment for Parts 1and 2 have completed.