B-Cell Depleting Drug Shows Benefit in IgG-Related Disease

WASHINGTON — The B-cell depleting agent inebilizumab (Uplizna) dramatically reduced the risk of flares and increased year-long remission of IgG4-related disease (RD), new research has found.

In a phase 3, multicenter, double-blind, randomized, placebo-controlled trial of 135 adults with active IgG4-RD, treatment with inebilizumab resulted in a significant 87% reduction in flare risk and nearly fivefold greater likelihood of flare-free remission at 1 year. The results were published online November 14 in the New England Journal of Medicine and were presented November 16 at the American College of Rheumatology (ACR) 2024 Annual Meeting. 

The drug’s manufacturer, Amgen, released top-line results of the trial, called MITIGATE, in June 2024.

Until now, the mainstay of management for the chronic multiorgan disease IgG4-RD has been glucocorticoids, which can cause numerous adverse effects. “It is hoped that inebilizumab can be used as an important steroid-sparing medication in this disease to reduce steroid toxicity,” lead author John H. Stone, MD, professor of medicine at Harvard Medical School, Boston, Massachusetts, told Medscape Medical News, noting that it may not entirely eliminate the need for steroid treatment, but for many, it appears to work after the remission induction period as a monotherapy without steroids. 

Asked to comment, Leonard H. Calabrese, DO, head of the Section of Clinical Immunology and manager of the Clinical Immunology Clinic at the Cleveland Clinic, Ohio, told Medscape Medical News: “There has been anecdotal or observational evidence for some effect with other immunosuppressive agents, including rituximab, but no robust clinical trial until this study. This clearly has demonstrated efficacy by reducing the risk of flares. And most importantly, putting people into remission means no active disease in any given organ…This gives us another tool in the toolbox to attack B-cell directed diseases, and I think it really makes a lot of sense.”

Calabrese cautioned, though, that “this is a disease that extends over many years. This is just a 1-year study. Label extensions will be important.”

And several questions remain, Calabrese noted: “How long do patients need to remain on drug? What will happen when the drug is stopped? Can they be retreated? These are the natural questions that arise in any sentinel study like this. But this is extremely encouraging. And I think it’s great for patients. I also think it’s a clarion call to increase awareness about this disease since there’s now strong evidence of effective treatment.” 

Underrecognized, Often Misdiagnosed as Cancer

Indeed, IgG4-RD, a chronic, relapsing, autoimmune, fibro-inflammatory multiorgan disease, was only first described in Japan in 2003. Since then, it has been reported all over the world yet remains vastly underrecognized. It is often misdiagnosed as cancer because it produces lesions in multiple organs. It received an ICD-10 code only about a year ago. A previous study estimated a prevalence of about 5.3 persons per 100,000 but that is likely to be a three- to fourfold underestimate, said Stone, who is also executive chairman of the IgG4ward! Foundation. 

“Nobody had heard of the disease until about 20 years ago…And there are many people in the world who have still not heard of it despite the fact that it is a multiorgan autoimmune disease and is probably as common, or more common, than many other diseases that rheumatologists spend a lot of time thinking about, such as scleroderma.”

While knowledge about the disease is increasing in rheumatology circles, it’s less well-recognized among many of the specialties where patients present, depending on the location of their lesions. These include gastroenterology, ophthalmology, pulmonary medicine, neurology, and nephrology. “All would be likely to see this disease,” Stone said. 

The disease can be mistaken for tumors in many of those locations and even as metastatic cancer, he noted, adding that “any time a patient has a mass lesion in a typical organ, the pancreas, the major salivary glands, the lungs, or the kidneys, this should be on the differential diagnosis.” 

The diagnosis of IgG4-RD is a clinical one, involving “quadrangulation between clinical features, serological findings, IgG4 levels in the blood, radiology studies, and then pathology biopsies when those are available,” Stone said. 

Calabrese characterized the current situation as “we’re all blind men on the elephant. To the neurologist or the neurosurgeon, it’s a mass in the brain. It could present to the ophthalmologist as an [eye] tumor. It can be thyroid gland failure, pulmonary disease, retroperitoneal fibrosis, hepatobiliary disease, and beyond. So, whoever sees that patient, there’s often a long lag time in recognizing it.”

And interestingly, Stone noted that unlike other autoimmune diseases, IgG4-RD primarily affects middle-aged men rather than younger-to-middle-aged women. And when IgG4-RD is diagnosed, glucocorticoid treatment can be particularly toxic when the pancreas is involved, heightening the risk for hyperglycemia and potentially causing diabetes. 

MITIGATE: Dramatic Improvement in Flares, Remission Achievement

MITIGATE is a phase 3, multicenter, double-blind, randomized, placebo-controlled trial in which 135 adults (mean age 58.2 years, 88 men) with active IgG4-RD were randomized 1:1 to receive 300-mg intravenous infusions of inebilizumab or placebo on days 1 and 15, and again at week 26. At baseline, 62 (45.9%) participants had newly diagnosed IgG4-RD and 73 (54.1%) had recurrent disease. 

Both groups received identical glucocorticoid tapers. Overall, 127 (94.1%) completed the 52 weeks of treatment. 

By 52 weeks, only seven patients in the inebilizumab group (10%) had experienced disease flares versus 40 (60%) in the placebo group, a significant difference with hazard ratio 0.13 (P

The percentage of participants achieving flare-free, treatment-free complete remission was 59 with inebilizumab (57%), compared with just 15 (22%) in the placebo group (odds ratio [OR], 4.68; P P

Excluding the 8-week glucocorticoid taper period, mean total glucocorticoid use was 1264.2 mg less in the inebilizumab than the placebo group, a significant reduction. Overall, 61 participants (90%) were able to entirely discontinue glucocorticoids during the trial, compared with just 25 (37%) in the placebo group. 

Adverse events of grade 3 or higher occurred in 12 participants (18%) in the inebilizumab group and 8 (12%) in the placebo group; serious adverse events occurred in 12 (18%) and 6 (9%), respectively. However, no serious adverse event occurred in more than one participant, and there were no deaths. Adverse events led to withdrawal from the trial in 6 patients (9%) in the inebilizumab group and 3 patients (4%) in the placebo group. 

Adverse events that occurred in more than 10% of participants in the inebilizumab group were COVID-19 in 16 participants (24%), lymphopenia in 11 (16%), and urinary tract infection in 8 (12%). 

Importantly, Stone noted, B-cell depletion can reduce responses to vaccines, so patients should receive all recommended vaccinations, including COVID-19, influenza, respiratory syncytial virus, and others, prior to initiating therapy. 

Uplizna (inebilizumab-cdon) was approved by the US Food and Drug Administration (FDA) for the treatment of neuromyelitis optica spectrum disorder in 2020. In October 2024, the US FDA granted Amgen breakthrough therapy designation for use in IgG4-RD. The company is also developing the drug for use in myasthenia gravis. 

The study was funded by Amgen. Stone has reported being a consultant for Amgen, Zenas, Argenx, Bristol Myers Squibb, Novartis, Sanofi, and Horizon Pharma. Calabrese has reported being a consultant and/or speaker for Amgen, AstraZeneca, Jansen, Sanofi, and UCB. 

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X (formerly Twitter) @MiriamETucker.