• \- 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.