Elotuzumab in Immunoglobulin G4-Related Disease (IgG4-RD)

This is a two-part multi-center clinical trial in participants with active IgG4-RD.

Part 1 (Cohort 1a and Cohort 1B) is an open-label, dose escalation phase to determine the safety of elotuzumab for investigation in IgG4-RD.

Part 2 (Cohort 2) is a randomized, placebo-controlled, double-blinded (masked) trial phase to compare the effects of elotuzumab and prednisone to elotuzumab placebo and prednisone in participants with IgG4 RD.

Approximately 75 participants with active IgG4-RD will be enrolled in the overall program, 12 in Part 1 and 63 in Part 2. Randomization in Part 2: 2 to 1, with approximately forty-two participants randomized to elotuzumab plus prednisone taper, and twenty-one participants randomized to placebo for elotuzumab plus prednisone taper.

The total duration of participation for each participant in this trial will be 48 weeks (11 months).

Immunoglobulin G4-Related Disease (IgG4-RD) is a chronic fibro-inflammatory condition that can affect virtually every organ system, including the pancreas, biliary tract, salivary and lacrimal glands, orbits, lungs, kidneys, meninges, pituitary gland, prostate and thyroid. It may also involve the retroperitoneum. This multi-organ immune-mediated condition, once regarded as a group of isolated, single-organ diseases, is now recognized to be an overarching, single-disease entity linked by common histopathological and immunohistochemical features.

IgG4-RD tends to afflict middle-aged to elderly individuals. Although IgG4-RD can affect a single organ at presentation, it is not uncommon for participants to present with or develop multi-organ disease. As the disease progresses, additional organs develop lesions and the cellular inflammation characterizing early disease moves toward a more fibrotic stage, causing major tissue damage, dysfunction and ultimately organ failure. It is unclear whether IgG4 itself is involved in the pathogenesis of the disease.

The goals of IgG4-RD treatment are to reduce inflammation and organ swelling and to prevent or reverse tissue fibrosis. No approved therapy exists for IgG4-RD.

This study will enroll adult participants who meet the 2019 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) Classification Criteria for IgG4-RD, and who have active IgG4-RD with disease manifestations in at least two organ systems.

Primary study objectives:

* To determine the safety and tolerability of the addition of elotuzumab to prednisone in participants with IgG4-RD, and
* To compare the effect of the addition of elotuzumab versus placebo to prednisone on the IgG4-RD Responder Index (IgG4-RD RI), a measure of IgG4-RD disease activity.

Eligibility Criteria:
Inclusion Criteria:

Individuals who meet all of the following criteria are eligible for enrollment as study participants:

1. Participant must be able to understand and provide informed consent and be willing to comply with study procedures and follow up.
2. Are at least 18 years of age and not older than 70 years of age at screening.
3. Meet the ACR/EULAR Classification Criteria for IgG4-RD \[30, 31\].
4. Have active disease based at screening on an IgG4-RD RI ≥4, with disease manifestations in at least two organ systems.
5. May have newly-diagnosed or relapsing disease at screening. Relapsing disease is defined as IgG4-RD that has previously been in remission but is now active again.
6. May be on treatment or off treatment for IgG4-RD at the time of screening. If on treatment, must be willing to discontinue those other treatments before the baseline visit.
7. No history of severe allergic reactions to monoclonal antibodies.
8. Female participants of childbearing potential must have a negative pregnancy test upon study entry.
9. Female participants of childbearing potential and male participants with a partner of childbearing potential must agree to consistently and correctly use FDA approved highly effective methods of birth control for the entire duration of the study and 6 months after last elotuzumab infusion.
10. Immunization with one of the FDA authorized or licensed SARS-CoV-2 vaccines as per CDC recommendations at the time of informed consent is required for study entry. Vaccinations must have been completed at least 2 weeks prior to start of study therapy.

Exclusion Criteria:

Individuals who meet any of these criteria are not eligible for enrollment as study participants:

1. Presence of a condition other than IgG4-RD that (e.g., asthma) is likely to require systemic Glucocorticoids (GC) for disease control during the period of the trial.
2. Malignancy within 5 years (except successfully treated in situ cervical cancer, resected squamous cell or basal cell carcinoma of the skin.)
3. The following lab values as indicators of hepatic dysfunction:

   1. Serum aspartate aminotransferase (AST) or alanine aminotransferase (ALT) greater than three times the upper limit of normal (ULN)
   2. Total bilirubin \> two times the ULN unless caused by Gilbert's disease. Gilbert's disease with total bilirubin \> three times ULN.
   3. Serum albumin \< 2.5 gm/dL.
4. Evidence of another uncontrolled condition which, in the judgment of the investigator, could interfere with participation in the trial according to the protocol.
5. Active infection requiring hospitalization or treatment with systemic antimicrobial agents within the 30 days prior to treatment allocation/randomization.
6. Prior use of rituximab or other B cell depleting agents within 9 months of enrollment unless B cells have been demonstrated to have repopulated.
7. Use of any investigational agent or biologic and non-biologic DMARDs within 5 half-lives of the agent (or 6 months if the half-life is unknown) prior to enrollment.
8. Any of the following laboratory tests at the Screening Visit:

   1. White blood cell count (WBC) \< 3.0 x 103/µL.
   2. Absolute neutrophil count (ANC) \< 1.5 x 103/µL.
   3. Hemoglobin \< 10 g/dL.
   4. Platelet count \< 75 x 109/L.
   5. Estimated glomerular filtration rate (eGFR) ≤ 45 ml/minute/1.73 m2.
9. The use of supplemental oxygen at baseline.
10. At or within 90 days of screening: Positive Interferon-Gamma Release Assay (IGRA). Indeterminate IGRAs must be repeated (with same or other IGRA per local policy) and shown to be negative. Alternatively, if the assay remains indeterminant, a participant must have a negative PPD. Finally, if the participant has had the Bacille Calmette-Guerin (BCG) vaccine or has some other condition complicating the interpretation of TB testing, consultation with infectious disease specialist must be obtained before receipt of the first investigational infusion.

    a. Participants diagnosed with latent TB are eligible but must have received appropriate prophylaxis for 30 days before their first investigational infusion.
11. Medical history or serologic evidence at Screening of chronic infections including:

    1. Human immunodeficiency virus infection.
    2. Hepatitis B as indicated by surface antigen or hepatitis B core antibody positivity
    3. Hepatitis C as indicated by anti-hepatitis C antibody positivity; if a participant is Hepatitis C antibody positive, they will be eligible to participate in the study if he/she is negative for viral load at Screening.
12. Live vaccines within 8 weeks of initiating study therapy.
13. Participant is pregnant or breastfeeding, or planning a pregnancy while enrolled in the study.
14. Substance use disorder, including the recurrent use of alcohol and/or drugs within the past year associated with clinically significant impairment associated with failure to meet major responsibilities at work, school, or home.
15. IgG4-RD that is dominated primarily by advanced fibrotic lesions. Specifically, participants whose disease manifestations consist only of

    1. retroperitoneal fibrosis,
    2. fibrosing mediatinitis,
    3. sclerosing mesenteritis, or
    4. Riedel's thyroiditis. Participants with these disease manifestations can be included, however, only if they have disease in 2 organ systems that is not of an advanced fibrotic nature and otherwise meet the Inclusion and Exclusion Criteria.
16. Evidence a SARS-CoV-2 (COVID-19) infection started within the 30 days prior to treatment allocation/randomization. Participants diagnosed with SARS-CoV-2 (COVID-19) infection more than 30 days prior to treatment allocation/randomization must have symptoms resolved and be deemed fit to participate in the trial.