This is a long-term extension trial of RAY121 in patients with immunological diseases such as antiphospholipid syndrome (APS), bullous pemphigoid (BP), Behçet's Syndrome (BS), dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM) and immune thrombocytopenia (ITP).

Inclusion Criteria:

1. Signed informed consent form
2. Have completed 4 doses of RAY121 administrations in RAY902CT trial and shown clinical responses
3. Ability to comply with the study protocol, in the investigator's judgment
4. For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use highly effective contraceptive methods during the treatment period and 20 weeks (140 days) after the last dose of RAY121
5. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating sperm

Exclusion Criteria:

1. History of anaphylaxis or hypersensitivity to a biologic agent
2. Known active infection with encapsuled bacteria
3. History of Neisseria meningitidis infection
4. Planned surgery
5. Pregnant or breastfeeding, or intending to become pregnant
6. Clinically significant electrocardiogram abnormalities
7. Illicit drug or alcohol abuse
8. Known or suspected immune deficiency
9. Treatment with investigational therapy other than RAY121
10. Vaccination with a live vaccine within 4 weeks

Qualified researchers may request access to individual patient level data through the clinical study data request platform. For further details on Chugai's Data Sharing Policy and how to request access to related clinical study documents, see here (www.chugai-pharm.co.jp/english/profile/rd/ctds\_request.html).