Inclusion Criteria (SAD):

1. 18 to 65 years old
2. Body mass index 18-30 kg/m2 and weight 55-100 kg
3. Individuals in good health
4. Agree to abstain from consumption of alcohol 48 hours prior to study visits
5. Agree to the use of highly effective contraception as defined in the protocol

Inclusion Criteria (MAD and Part 2 Expansion):

Patients with RA:

1. 18 to 75 years old
2. Diagnosis of adult-onset RA
3. Class I-III RA
4. Moderately to severely active RA

Patients with SjD:

1. 18 to 75 years old
2. Diagnosis of primary SjD

Exclusion Criteria (SAD):

1. Inadequate clinical laboratory parameters at Screening
2. Active infection
3. Receipt of or inability to discontinue any excluded therapies
4. Individuals with immediate household contact with your children (eg, ≤ 6 years old) or immunocompromised persons
5. History of alcohol or drug abuse within last 12 months
6. Positive alcohol breathalyzer or drug screen prior to dosing
7. Inability to comply with protocol-mandated requirements
8. History of severe allergic or anaphylactic reactions to mAb therapy (or recombinant anti-body-related fusion proteins) or any constituents of study drug
9. Major surgery requiring use of general anesthesia within 12 weeks or planned or expected major surgery during the study
10. Blood donation or significant blood loss within 30 days
11. Individuals considered to be part of a vulnerable population (eg, incarceration)
12. Individuals that in the opinion of the Investigator, are not suitable for participation in the trial

Exclusion Criteria for patients with RA or SjD:

1. Inadequate clinical laboratory parameters at Screening
2. Active infection
3. Receipt of or inability to discontinue any excluded therapies
4. History of progressive multifocal leukoencephalopathy
5. Central nervous system disease
6. Presence of 1 or more significant concurrent medical conditions
7. Have a diagnosis or history of malignant disease within 5 years
8. History of severe allergic or anaphylactic reactions to mAb therapy (or recombinant antibody-related fusion proteins) or any constituents of study drug
9. Women who are pregnant or breastfeeding
10. Patients who do not agree to the use of highly effective contraception as defined by the protocol