Leapfrogging Ahead
Not all the new drugs work in every indicated patient, Dr. Howard said. For example, up to 30% of patients do not respond to complement inhibitors. “We don’t understand why. It’s as if we have leapfrogged way ahead in terms of therapeutics, and now we have to go back and answer all the questions – the who, what, where, and why of an individual drug and its response in folks.”
In this climate, said Dr. Kaminski, heavy direct-to-consumer advertising of newer myasthenia gravis therapies creates complications. “My patients are highly excited to see, ‘that’s my disease being advertised on Jeopardy.’ ” Many patients are frustrated with the general lack of awareness regarding myasthenia gravis, he added. “But then I’ve had patients who clearly would never qualify for a certain medication getting mailings to their homes.”
Dr. Howard countered that broader awareness of myasthenia gravis can only help. “There’s increasing recognition of the disease, not only by patients, but to some extent, by the treating clinician. Patients are coming to our offices and saying, ‘am I a candidate for this new drug?’ It’s the responsibility of the clinician to decide.”
Individual physicians’ practice patterns vary greatly, said Dr. Kaminski, and very little quantitative data exist here. But based on personal communications, academic-center neurologists tend to use targeted treatments on patients who have failed conventional treatments.
Conversely, Dr. Howard said that, because community physicians rarely see myasthenia gravis, and targeted treatments remain relatively new, many of these providers rely on prednisone, azathioprine, and mycophenolate mofetil.
B-Cell Blockers in Development
Overall, said Dr. Howard, the field of myasthenia gravis treatment development is “very rich. And pharma’s interest in myasthenia has taken off like a rocket. It’s exceptionally gratifying to those of us who take care of these patients whose life is miserable” because of adverse effects and/or nonresponse to current drugs.
“In myasthenia,” added Dr. Kaminski, “we know that T cells are promoting the activity of these auto-reactive B cells.” Many drugs currently in phase 2 or 3 development aim to eliminate B cells or signaling between T and B cells, he said. “That’s where most of the drug development is.”
Leading candidates include telitacicept (Tai’ai, RemeGen), which is both a B-lymphocyte stimulator and a proliferation-inducing ligand. A phase 3 trial (NCT05737160) is ongoing, with primary completion expected in late 2026. A second phase 3 trial (NCT06456580) recently began enrolling. Dr. Howard said that, although early results warranted phase 3 analysis, telitacicept’s phase 2 trial was open label and lacked a placebo group.9 The latter is a critical concern because placebo response rates in myasthenia gravis trials average 35%-40%.
Combined with standard care, the FcRn inhibitor nipocalimab (Johnson & Johnson) enabled patients with AChR, MuSK, and/or LRP4 autoantibodies to improve by 4.70 points on the MG-ADL vs 3.25 points for placebo (P = .002) over 24 weeks in phase 3.10All FcRn inhibitors in development can broadly reduce autoantibody levels, said Dr. Howard. “But what role they will play in myasthenia gravis when they’re several years behind leaders in the field in terms of capturing market remains to be seen.”
Additionally, batoclimab (Immunovant/Harbour BioMed) showed positive topline results in phase 3, and an elevated rate of hypercholesterolemia in treated patients that was transient and consistent with previous research.11 Subsequent to efgartigimod, Dr. Howard said, FcRn inhibitors are full-size antibodies. “I believe that contributes to the adverse events that we see. Efgartigimod is a small FcRn fragment. That’s why it’s a cleaner drug, if you will.”
FcRn inhibitors require periodic retreatment. For example, said Dr. Howard, the ADAPT phase 3 trial of efgartigimod, on which he was lead investigator, employed a cyclic dosing schedule – 4 weeks’ treatment, then observation until patients needed retreatment — because patients demanded it.12 In clinical practice, some patients have gone more than 25 weeks before needing retreatment. One of his patients went beyond 40 weeks. “Others only get around 6-9 weeks. So patient choice again enters the decision-making process.”
Rituximab targets the CD20 protein on B cells nonspecifically, producing general immunosuppression. “That’s problematic in producing significant immunosuppression,” said Dr. Kaminski. Nevertheless, he said, rituximab is very effective for most patients with MuSK-specific MG, and its application to this indication has revealed differences between the MuSK subtype and AChR antibody–positive myasthenia. Specifically, MuSK antibody–positive patients have short-lived plasmablasts, which rituximab eliminates.13
Conversely, said Dr. Kaminski, patients with AChR antibody-positive myasthenia, especially long-term, likely have long-lived plasmablasts producing antibodies. This fact, and these patients’ lack of CD20, likely explain their poor response to rituximab.
A phase 3 trial (NCT04524273) of the CD19 blocker inebilizumab (Uplinza, Amgen) reached primary completion in May. Dr. Howard said that if topline results (unreleased at press time) prove positive, inebilizumab could replace rituximab in MG — provided payers do not reject inebilizumab because of cost.