A phase 3, randomized, double-blind, multicenter, placebo-controlled study of Inebilizumab efficacy and safety in IgG4-related disease

1. Male or female adults, who have reached the age of consent in the applicable
region (eg, >= 18 years in the US).

2. Written informed consent and any locally required authorization (eg, data
Privacy) obtained from the subject prior to performing any protocol-related
procedures, including screening evaluations.

3. Clinical diagnosis of IgG4-RD.

4. Fulfillment of the 2019 ACR/EULAR classification criteria (Appendix A) as
determined by the Eligibility Committee. Specifically, subjects must meet the
classification criteria entry requirements (including involvement of one of the
following organs: pancreas, bile ducts/biliary tree, orbits, lungs, kidneys,
lacrimal glands, major salivary glands, retroperitoneum, aorta, pachymeninges,
or thyroid gland [Riedel*s thyroiditis]), must not meet any of the
classification criteria exclusions, and must achieve at least 20 classification
criteria inclusion points.

5. Experiencing (or recently experienced) an IgG4-RD flare that requires
initiation or continuation of GC treatment at the time of informed consent.
This criterion may be met in two ways:

* On GC therapy for recent IgG4-RD flare, having received a maximum of 4 weeks
of treatment prior to informed consent at a dose no higher than 60 mg/day
prednisone or equivalent, and at 20 mg/day prednisone or equivalent on the day
prior to randomization, or

* Experiencing active disease not currently being treated at the time of
informed consent, with planned initiation of treatment for flare with GC at a
maximum dose of 60 mg/day prednisone (or equivalent) and with a plan to be
treated at a dose of 20 mg/day of prednisone (or equivalent) on the day prior
to randomization, for a total duration of GC treatment during screening period
of at least 3 weeks at the time of randomization.

This GC therapy can either be newly initiated or be increased from a
maintenance dose of <= 10 mg/day of prednisone or equivalent. Subjects unable to
be tapered to 20 mg/day of prednisone or equivalent by Visit 2 may not be
randomized.

Total duration of GC treatment must be at least 3 weeks and not exceed 8 weeks
prior to randomization.


6. IgG4-RD affecting at least 2 organs/sites at any time in the course of
IgG4-RD with documentation to confirm. One organ must meet the requirements for
the ACR/EULAR classification criteria (inclusion 4); the second organ is as
defined by the investigator.

7. Willing and able to comply with the protocol, complete study assessments,
and complete the study period.

8. Non-sterilized male subjects who are sexually active with a female partner
of childbearing potential must use a condom with spermicide (where spermicide
is available) from Day 1 through to the end of the study and must agree to
continue using such precautions for at least 6 months after the final dose of
IP.

Females of childbearing potential who are sexually active with a non-sterilized
male partner must use a highly effective method of contraception (Table 2 on
page 36 of Protocol Amendment 3 dated 16 April 2020) from signing informed
consent and must agree to continue using such precautions through the end of
the follow-up of the study and at least 180 days after the last dose of IP;
cessation of contraception after this point should be discussed with a
responsible physician. Periodic abstinence, the rhythm method, and the
withdrawal method are not acceptable methods of contraception. A recommendation
will be made that the female partners (of childbearing potential) of male study
participants should use a highly effective method of contraception other than a
barrier method.

Females of childbearing potential are defined as those who are not surgically
sterile (ie, surgical sterilization includes bilateral tubal ligation,
bilateral oophorectomy, or hysterectomy) or those who are not postmenopausal
(defined as 12 months with no menses without an alternative medical cause and a
follicle-stimulating hormone within the postmenopausal range as established by
the clinical laboratory).

1. Severe cardiovascular, respiratory, endocrine, gastrointestinal,
hematological, neurological, psychiatric, or systemic disorder, or any other
condition that, in the opinion of the Investigator, would place the patient at
unacceptable risk of complications, interfere with evaluation of the IP, or
confound the interpretation of patient safety or study results. 2. History of
solid organ or cell-based transplantation. 3. Known immunodeficiency disorder.
4. Active malignancy or history of malignancy that was active within the last
10 years, except as follows: * In situ carcinoma of the cervix following
apparently curative therapy > 12 months prior to screening, * Cutaneous basal
cell or squamous cell carcinoma following apparently curative therapy, or *
Prostate cancer treated with radical prostatectomy or radiation therapy with
curative intent > 3 years prior to screening and without known recurrence or
current treatment. or * Thyroid cancer for which surgery has been performed and
there is no evidence of active disease. 5. Receipt of any biologic B
cell-depleting therapy (eg, rituximab, ocrelizumab, obinutuzumab, ofatumumab,
inebilizumab) in the 6 months prior to screening. 6. Receipt of non-depleting
B-cell-directed therapy (eg, belimumab), abatacept, or other biologic
immunomodulatory agent within 6 months prior screening. 7. Receipt of
non-biologic DMARD or immunosuppressive agent other than GCs (eg, azathioprine,
mycophenolate mofetil, methotrexate, others) within 4 weeks prior to screening.
8. Receipt of any investigational agent < 12 weeks or < 5 half-lives of the
drug (whichever is longer) prior to screening. 9. Inability to be tapered off
of GC therapy by 8 weeks post-randomization (other than <= 2.5 mg/day prednisone
or equivalent for treatment of adrenal insufficiency or intolerance of taper)
in the opinion of the Investigator. 10. Receipt of live vaccine or live
therapeutic infectious agent within the 2 weeks prior to screening. 11.
Pregnancy, lactation, or planning to become pregnant within 6 months of the
last dose of IP. 12. Positive test for, or prior treatment for, hepatitis B or
HIV infection. A positive test for hepatitis B is detection of either (1)
hepatitis B surface antigen (HBsAg); or (2) hepatitis B core antibody
(anti-HBc); and in Japan only (3) hepatitis B surface antibody (HBsAb). 13.
History of untreated hepatitis C infection, or positive antibody test for
hepatitis C virus (HCV) unless patient is considered to be cured following
antiviral therapy and has a HCV viral load below the limit of detection at
least 24 weeks after completion of treatment at site or central lab. 14.
Evidence of active tuberculosis (TB) or being at high risk for TB based on: *
History of active TB or untreated/incompletely treated latent TB. Patients with
a history of active or latent TB who have documentation of completion of
treatment according to local guidelines may be enrolled. * History of recent (<=
12 weeks of screening) close contact with someone with active TB (close contact
is defined as >= 4 hours/week OR living in the same household OR in a house
where a person with active TB is a frequent visitor). * Signs or symptoms that
could represent active TB by medical history or physical examination. *
Positive, indeterminate, or invalid interferon-gamma release assay test result
at screening, unless previously treated for TB. Patients with an indeterminate
test result can repeat the test once, but if the repeat test is also
indeterminate, the patient is excluded. * Chest radiograph, chest computed
tomography (CT) or MRI scan that suggests a possible diagnosis of TB or
suggests that a work-up for TB should be considered; all patients must have had
lung imaging with an acceptable reading within 6 months prior to consent, or
during screening. 15. History of > 1 episode of herpes zoster (any grade)
and/or any other definite or probable opportunistic infection in the 12 months
prior to screening (see Appendix D for details on opportunistic infections that
require exclusion). 16. Known history of allergy or reaction to any component
of inebilizumab formulation or history of anaphylaxis to any human gamma
globulin therapy. 17. Allergy to or intolerance of protocol-required treatment,
including medications for prophylaxis of infusion reactions (antipyretic such
as paracetamol/acetaminophen or equivalent, diphenhydramine or equivalent, and
methylprednisolone or equivalent). 18. Estimated glomerular filtration rate <
30 mL/min/1.73 m2 by Modification of Diet in Renal Disease Study (MDRD)
equation (NIDDK). 19. Blood tests at screening that meet any of the following
criteria: * Hemoglobin < 7.5 g/dL * Neutrophils < 1200/mm3 * Platelets < 110 ×
10^9/L * Eosinophil count > 3000/mm3 * Prothrombin time > 1.2 x upper limit of
normal (ULN); however, subjects who are anticoagulated due to atrial
fibrillation and who have aspartate aminotransferase (AST) and alanine
aminotransferase (ALT) levels <= 2 x ULN are not excluded * Total
immunoglobulins < 600 mg/dL * CD19+ B cells at screen < 40 cells/*L; an
exclusionary value may be repeated. 20. Subjects with the following abnormal
liver function tests in the absence of hepatobiliary IgG4-RD activity: *
Aspartate aminotransferase (AST) > 2 × ULN * Alanine aminotransferase (ALT) > 2
× ULN * Total bilirubin (TBL) > 2 × ULN unless AST, ALT, and hemoglobin are
within central laboratory normal range and the patient has a known history of
Gilbert syndrome OR Subjects with the following abnormal liver function tests
in the presence of hepatobiliary IgG4-RD activity: * AST > 10 × ULN * ALT > 10
× ULN * TBL > 5 × ULN Screening liver function tests may be repeated prior to
randomization to permit abnormal values due to hepatobiliary IgG4-RD activity
to respond to GC treatment. 21. Known positive anti-neutrophil cytoplasmic
antibodies (ANCA) targeted against proteinase 3 or myeloperoxidase based on
patient records. 22. History of alcohol or drug abuse that, in the opinion of
the Investigator, might affect patient safety or compliance with visits or
interfere with safety or other study assessments. 23. Active, clinically
significant infection at the time of randomization (IP administration may be
delayed until recovery, if within screening window, otherwise subject may be
rescreened). 24. Participation in any clinical trial that includes use of any
pharmacologic intervention.