A Study to Evaluate the Safety, Tolerability, Efficacy, and Drug Levels of CC-97540 in Participants With Relapsing Forms of Multiple Sclerosis, Progressive Forms of Multiple Sclerosis or Refractory Myasthenia Gravis (MG) (Breakfree-2)

A Phase 1, Multicenter, Single-arm, Dose-escalation Study of CC-97540 (BMS-986353), CD19-Targeted NEX-T Chimeric Antigen Receptor (CAR) T Cells, Evaluating Safety and Tolerability in Participants With Autoimmune Neurological Diseases: Relapsing Forms of Multiple Sclerosis (RMS), Progressive Forms of Multiple Sclerosis (PMS), or Refractory Myasthenia Gravis (MG).

The purpose of this study is to evaluate the safety, tolerability, efficacy, and drug levels of CC-97540 in participants with Relapsing Forms of Multiple Sclerosis (RMS), Progressive Forms of Multiple Sclerosis (PMS) or Refractory Myasthenia Gravis (MG).

Inclusion Criteria

- Relapsing forms of Multiple Sclerosis (RMS) - Cohort 1.

i) Participants must have an Expanded Disability Status Scale (EDSS) of ≥ 3.0 and ≤ 5.5.

ii) Participants must have a diagnosis of Multiple Sclerosis (MS) with relapsed/refractory MS or conversion to active secondary progressive multiple sclerosis (aSPMS), and worsening of disease within 12 months prior to Screening and while on treatment with a high-efficacy DMT for at least 6 months.

- Progressive forms of MS - Cohort 2.

i) Participants must have an EDSS ≥ 3.0 and ≤ 6.0.

ii) Participants must have a diagnosis of primary progressive multiple sclerosis (PPMS) that is treatment-resistant or diagnosis of inactive secondary progressive multiple sclerosis (iSPMS).

- Myasthenia Gravis - Cohort 3

i)MGFA classification of II-IV at screening

ii) Documentation of autoantibodies against AChR or MuSK (historical or at Screening)

iii) Refractory disease defined as disease activity on at least 2 immunosuppressants, including steroids, NSIs, or biologics.

iv) Has had thymectomy, only if indicated according to current guidelines.

Exclusion Criteria

• Cohorts 1 and 2: Participants that cannot complete the 9-Hole Peg Test (9-HPT) in at least 1 hand in <240 seconds unless extenuating medical conditions unrelated to MS prohibit this.
• Participants that cannot perform a Timed 25-Foot Walk Test (T25FWT) in < 150 seconds.
• Presence of other confounding peripheral nervous system disorders or other disorders that may impact muscle strength (eg, myositis) or cause weakness, stroke, chronic inflammatory demyelinating polyradiculoneuropathy, Lambert-Eaton myasthenic syndrome.
• Other protocol-defined Inclusion/Exclusion criteria apply.