Study to Evaluate the Effect of XmAb®5871 on Disease Activity in Patients With IgG4-Related Disease (RD)

Study Overview
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Brief Summary
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The purpose of this Phase 2 study is to investigate the effect of XmAb5871 on IgG4-Related Disease (RD) activity

Official Title
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An Open-label, Single-arm, Pilot Study to Evaluate the Effect of XmAb®5871 on Disease Activity in Patients With IgG4-Related Disease

Conditions
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IgG4-RD

Intervention / Treatment
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* Biological: XmAb5871


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Active IgG4-RD Compatible pattern of organ involvement consistent with IgG4-RD that cannot be attributed to other causes Histopathologically-proven diagnosis of IgG4-RD Peripheral blood plasmablast count >900 cells/mL and/or elevated IgG4-RD levels during screening Able and willing to complete the entire study according to the study schedule Able and willing to provide written informed consent Exclusion Criteria: History or evidence of a clinically unstable/uncontrolled disorder, condition or disease other than IgG4-RD that, in the opinion of the Investigator would pose a risk to the patient safety or interfere with the study evaluation, procedures or completion Malignancy within 5 years (except successfully treated in situ cervical cancer, resected squamous cell or basal cell carcinoma of the skin, or prostate cancer with no recurrence ≥3 years following prostatectomy) Presence of recurrent or chronic infections, defined as ≥3 infections requiring antimicrobials over the past 6 months prior to screening Active infection requiring hospitalization or treatment with parenteral antimicrobials within the 60 days prior to randomization or oral antimicrobials within the 21 days prior to enrollment Patient is taking >40 mg of prednisone QD Prior use of rituximab (or other B cell depleting agents) within 6 months of enrollment. Prior use of any B cell depleting agent greater than 6 months from enrollment is allowed if the CD19+ B cell count is within the normal reference range during screening Use of any investigational agent within 5 half-lives of the agent (or 6 months if the half-life is unknown) prior to enrollment Immunosuppressive agent use within the three months prior to enrollment Has received live vaccines within 2 months of enrollment Patient is pregnant or breast feeding, or planning to become pregnant while enrolled in the study, up to end-of-study visit Unable or unwilling to partake in the follow-up assessments or required protocol procedures

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: XmAb5871<br>XmAb5871 administered by IV infusion for up to a total of 12 infusions | Biological: XmAb5871<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proportion of Patients With an Improvement in IgG4-RD Activity | Improvement of disease activity as defined by a decrease of IgG4-RD responder index >= 2 points from Day 1 pre-dose disease activity score. The IgG4-RD Responder Index Total Activity Score ranges from 0 to a maximum of 162. Higher scores represent greater (i.e. worse) disease activity. A score of 0 represents no disease activity other than residual fibrosis. | Baseline Day 1 to Day 169 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Patients Experiencing a Treatment-emergent Adverse Event as Assessed by CTCAE v4.3 | The number of patients experiencing a treatment-emergent adverse event as assessed by CTCAE v4.3 will be tabulated according to MedDRA system-organ class and preferred term, intensity and causality. | Baseline Day 1 to Day 197 |