Inclusion Criteria:

1. Signed informed consent form
2. Age greater than or equal to 18 and less than or equal to 75 at the time of signing informed consent form (except for BP; Age greater than or equal to 18 and less than or equal to 85 with Karnofsky score greater than or equal to 60% at screening)
3. Ability to comply with the study protocol
4. For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use highly effective contraceptive methods
5. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating sperm
6. APS cohort: Established primary APS defined by the following criteria (at least one of the laboratory criteria and one of the clinical criteria must be met):

• Laboratory criteria (aPL profile)

a. Persistently positive lupus anticoagulant (LA) test

b. Persistently positive anticardiolipin (aCL) immunoglobulin G (IgG) isotype

c. Persistently positive anti-beta-2 glycoprotein-1 (aB2GPI) IgG isotype

• Clinical criteria

a. Livedoid vasculopathy and presence of skin ulcer

b. Acute/chronic aPL nephropathy

1. BP cohort:

• 1) Age greater than or equal to 18 and less than or equal to 85 with Karnofsky score greater than or equal to 60 %
• 2) Predominant cutaneous lesions
• 3) Diagnosis with BP with following assessments positive:
• a Positive direct immunofluorescence, and either
• b Positive indirect immunofluorescence, or
• c Positive serology on ELISA for BP180 autoantibody

• 4) Bullous Pemphigoid Disease Area Index (BPDAI) score greater than or equal to 20
• 5) Weekly average of daily Peak Pruritus Numerical Rating Score (PP-NRS) greater than or equal to 4
• 6) Accept to take photograph of bullous lesions

1. BS cohort:

• 1) Diagnosed with BS
• 2) Oral ulcers that occurred at least 3 times in the previous 12 month period
• 3) Have at least 2 oral ulcers over the 4 weeks prior to screening
• 4) Have at least 2 oral ulcers at Week 0
• 5) Have prior treatment with at least 1 non-biologic BS therapy
• 6) Patients who need systemic therapy as whose oral or mucocutaneous ulcers cannot be adequately controlled by topical therapy

1. DM cohort:

• 1) Diagnosed with definite or probable inflammatory myopathies and categorized as DM
• 2) Patients with inadequate response to corticosteroids and/or immune-suppressants or intolerance to DM therapies
• 3) Manual Muscle Test-8 (MMT-8) score less than 142, with at least one abnormality in the following Core Set Measures:
• Patient Global Activity Visual Analogue Scale (PtGA-VAS) greater than or equal to 2 cm
• Physician Global Activity Visual Analogue Scale (PhGA-VAS) greater than or equal to 2 cm
• Global extra-muscular activity greater than or equal to 2 cm
• At least one muscle enzyme greater than 1.5 times upper limit of normal (ULN)
• Health Assessment Questionnaire (HAQ) greater than or equal to 0.25

• 4) Moderate to severe DM defined as CDASI activity score greater than 14

1. IMNM cohort:

• 1) Clinically Diagnosed with IMNM as anti-HMGCR myopathy or anti-SRP myopathy
• 2) Creatine kinase (CK) greater than 1,000 U/L
• 3) Patients who have an inadequate response to corticosteroids and/or immunosuppressants or intolerance to IMNM therapies
• 4) MMT-8 score less than 142

1. ITP cohort:

• 1) Confirmed diagnosis of persistent/chronic ITP based on the following criteria:
• ITP defined per the current guidelines
• Platelet count less than or equal to 30 × 10^9/L on 2 consecutive occasions

• 2) Lack of an sustained adequate platelet count response to a thrombopoietin receptor agonist and at least one other ITP treatment or a second thrombopoietin receptor agonist (TPO-RA)

Note: Other protocol defined Inclusion/Exclusion criteria may apply.