Rituximab is dramatically effective in IgG4-related disease

SNOWMASS, COLO. – Glucocorticoids remain the first-line therapy in immunoglobulin G4-related disease, but it’s essential to bear in mind that their long-term efficacy in this immune-mediated fibroinflammatory disease is the exception rather than the rule, John H. Stone, MD, said at the Winter Rheumatology Symposium sponsored by the American College of Rheumatology.

Dr. Stone, professor of medicine at Harvard Medical School, Boston, was a coauthor of an international expert consensus statement on the treatment of IgG4-related disease (IgG4-RD) which emphasized that point (Arthritis Rheumatol. 2015 Jul;67[7]:1688-99).

“I typically start with prednisone at 40 mg/day, and there’s a dramatic response in these patients. Then I taper them off after 2-3 months. If 2-3 months doesn’t put them into a long-term sustained remission, it’s time to go to something else,” said Dr. Stone, who also serves as director of clinical rheumatology at Massachusetts General Hospital, Boston.

“Glucocorticoids are rapidly effective, but initial reports were overoptimistic about their long-term efficacy. They don’t cure this disease any more than they cure giant cell arteritis in most of our patients, or ANCA-associated vasculitis. And since patients with IgG4-related disease are often older and may already have disease-induced damage to the pancreas and other organs, the morbidity from steroids in this population is formidable,” the rheumatologist explained.

In his series of 125 patients with biopsy-proven IgG4-RD, 83% responded to steroids initially, but 77% of steroid-treated patients failed to achieve a stable steroid-free remission after treatment discontinuation (Arthritis Rheumatol. 2015 Sep;67[9]:2466-75).

There is no evidence at all to indicate that conventional steroid-sparing drugs such as methotrexate, azathioprine, and mycophenolate mofetil are effective in IgG4-RD, the rheumatologist noted.

So what’s the next move, then, after steroids fail? Dr. Stone was a pioneer in the strikingly successful use of B cell depletion via rituximab (Rituxan) in patients with IgG4-RD. First he and his coinvestigators demonstrated that this off-label use of rituximab led to rapid clinical and histologic improvement (Ann Rheum Dis. 2015 Jun; 74[6]:1171-7), then they showed it also causes levels of circulating plasmablasts, serum IgG4, and biomarkers of fibrosis to plunge, suggesting B cell depletion may halt the destructive process of collagen deposition that characterizes this immune-related disease (Ann Rheum Dis. 2015 Dec;74[12]:2236-43). They have also reported that patients with very elevated baseline serum IgG4 levels are at more than sixfold increased risk of relapse at a median of 244 days from their first rituximab infusion (Rheumatology [Oxford]. 2016 Jun;55[6]:1000-8).

The success with rituximab is just one example of how improved understanding of the pathophysiology of IgG4-RD has opened the door to novel treatments. Dr. Stone is the lead investigator in an ongoing phase II, open-label study in which 15 patients with active IgG4-RD will receive intravenous XmAb5871 every 2 weeks for 6 months to evaluate the effect on the IgG4-RD Responder Index. XmAb5871 is a monoclonal antibody that binds to CD19 and FCgammaRIIb in order to downregulate activated B cells and plasmablasts. It is also being developed for treatment of systemic lupus erythematosus.

Dr. Stone and his coinvestigators are working on a therapeutic approach to IgG4-RD that targets antigen presentation by activated B cells to CD4+ cytotoxic T cells at sites of disease. These CD4+ cytotoxic T cells contain signaling lymphocyte activation molecule F7 (SLAMF7) as a surface marker. Elotuzumab (Empliciti), an immunostimulatory humanized monoclonal antibody targeting SLAMF7, is already on the market for treatment of multiple myeloma, he noted.

Dr. Stone reported receiving IgG4-RD-related research funding from and serving as a consultant to Genentech and Xencor, which is developing XmAb5871.

bjancin@frontlinemedcom.com