A Trial in Healthy Adult Participants and Adults With Autoimmune Disease to Test How HBM7020 is Tolerated and Absorbed in the Body

Key Inclusion Criteria for Healthy Participants (Part 1) 1. Participants who are of non-childbearing potential or are using acceptable contraception. 2. Body mass index (BMI) and body weight within an acceptable range. 3. Good general health based on medical history, physical examination, electrocardiogram (ECG), and laboratory assessments. Key Disease-Agnostic Inclusion Criteria for Patient Participants (Part 1) 1. BMI and body weight within an acceptable range. 2. Adequate hematologic, renal, hepatic, immunologic, and lymphocyte parameters. Key Disease-Specific Inclusion Criteria for Patient Participants (Part 1) 1. Confirmed autoimmune disease with appropriate supporting autoantibody findings. 2. Stable background therapy prior to dosing. 3. Active moderate to severe disease consistent with protocol-defined disease activity criteria for: * Systemic lupus erythematosus (SLE) * Systemic sclerosis (SSc) * Rheumatoid arthritis (RA) * Sjögren's disease (SjD) Key Inclusion Criteria for Rescreening Participants (Part 2) 1. Meets Part 1 disease-agnostic inclusion criteria. 2. Stable background autoimmune therapy prior to dosing. 3. Ongoing active moderate to severe disease based on protocol-defined disease-specific criteria. Key Exclusion Criteria for Parts 1 and 2 1. Pregnant or breastfeeding participants. 2. Recent vaccination within protocol-defined timelines. 3. Clinically significant medical history or abnormal physical examination findings. 4. Clinically significant cardiovascular abnormalities, including blood pressure, heart rate, syncope, or ECG findings. 5. Prior or recent therapies or conditions that may interfere with study participation or safety evaluations. 6. Severe pulmonary, renal, or cardiac disease, or clinically significant pulmonary hypertension.