Real-world use of gMG treatment in US mirrors patterns seen in trials
Though data show most Americans taking drug are older, may be overweight
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- A new study found that use of the approved gMG treatment Rystiggo in the U.S. mirrors patterns seen in clinical trials.
- Still, real-world patients starting Rystiggo are typically older and more frequently overweight than were trial participants.
- The researchers say these data provide key insights into the treatment's use by patient groups excluded from clinical testing.
Since its approval in the U.S. in 2023 for people with generalized myasthenia gravis (gMG), Rystiggo (rozanolixizumab-noli) has been prescribed to a wide range of adults with the autoimmune disease — but, according to researchers, with little understanding of the real-life “profile” of patients starting the infusion therapy.
Now, a real-world study led by U.S. scientists has found that the start of new Rystiggo treatment cycles occurs about as often as it did in clinical testing of the therapy. Overall, per the team, “treatment patterns [were] generally consistent with clinical trials.”
Still, the scientists noted that gMG patients in the real-world setting were older and more often overweight than participants in the main study supporting the treatment’s approval.
Because these patients are “often underrepresented in, or even excluded from, clinical studies … these real-world data provide important insights on these patient groups within an [gMG] population,” the researchers wrote.
Importantly, the team noted, “the alignment between the clinical and real-world data reported here suggests that the individualized approach to treatment in the clinical trials may be being reflected in clinical practice, and that patients can expect a similar treatment-free interval.”
The study, “Characterization of Patients Living with Generalized Myasthenia Gravis Initiating Rozanolixizumab in the USA,” was published in the journal Drugs – Real World Outcomes. It was funded by UCB, the drug’s developer; three of the five study authors are company employees.
In the U.S., Rystiggo is indicated for individuals 18 and older with gMG, a disease marked by muscle weakness and fatigue. It’s specifically cleared for use by patients who test positive for self-reactive antibodies against the acetylcholine receptor (AChR) protein or the muscle-specific tyrosine kinase (MuSK) protein. Those are the two most common disease-driving antibodies.
The therapy is given as a once-weekly subcutaneous, or under-the-skin, infusion over a six-week cycle. After that, later cycles are based on clinical evaluation.
Rystiggo’s regulatory approvals were mainly based on data from the Phase 3 MycarinG trial (NCT03971422), which showed that the therapy reduced gMG severity and improved activities of daily living in gMG patients positive for the most common antibodies.
Clinical trials usually exclude older patients, those with obesity
Still, the researchers noted that clinical trials enroll a selected group of participants, which often limits the inclusion of older patients, those with obesity and other conditions, and individuals with differing disease severity.
“The value of real-world data lies in its typical inclusion of a much broader and more [varied] patient population than Phase 3 trials, covering the whole spectrum of patients seen by clinicians,” the team wrote.
To understand the profile of gMG patients in the U.S. starting Rystiggo in the real-world setting, the researchers looked back at existing records from UCB’s ONWARD patient support program. That initiative was started in July 2023, shortly after the therapy’s U.S. approval, and involved three pharmacies that distributed the medication.
The value of real-world data lies in its typical inclusion of a much broader and more [varied] patient population than [late-stage clinical] trials, covering the whole spectrum of patients seen by clinicians.
A total of 887 adults, about evenly split by sex, were involved in the final analysis. All had a documented gMG diagnosis before starting Rystiggo in or before February 2025. Overall, these patients were slightly older than those in the MycarinG study, with a mean age of 62.2 years versus 51.8 years. A total of 60% were older than 60.
The median body weight of the real-world patients was 87 kg (about 191 pounds), with two-thirds weighing 50-99 kg (about 110-218 pounds). Nearly one third of patients weighed at least 100 kg (220 pounds), “a higher proportion than in MycarinG (30% versus 22%),” the researchers wrote.
Among patients with recorded antibody status, most (73%) had anti-AChR antibodies, while some (15%) had anti-MuSK antibodies.
Disease severity was described using the Myasthenia Gravis (MG) Foundation of America Clinical Classification, which ranges from Class I (mildest) to Class V (most severe). Most participants were in Classes II (38%) and III (46%), the researchers found.
The mean score on MG Activities of Daily Living (MG-ADL), a patient-reported measure of how MG affects everyday activities, was 8.4 at baseline, or the study’s start, using a scale from zero for symptom-free to 24, indicating severe symptoms. Baseline was defined as the period from the date of entry into the patient support program or specialty pharmacies.
Over half of gMG patients on Rystiggo previously took steroids
Available data showed that the most common previous treatment was corticosteroids, used by about 60%, and that the most frequently used therapy at the time of starting Rystiggo was acetylcholinesterase inhibitors, by 49%.
Nearly all participants — more than 98% — had not previously received Rystiggo, and neurologists (96%) were the main prescribing specialists.
Follow-up analyses covered 393 patients with specialty pharmacy data (68%) who had at least one additional infusion after the first. These individuals were followed for a median of 31 weeks, or about seven months (with a range of three weeks to about 1.5 years).
The data showed that these gMG patients started a mean of three treatment cycles. The mean time between the end of one cycle and the start of the next was 5.9 weeks.
Among the 100 patients with at least one year of follow-up after starting Rystiggo, the mean number of cycles started in the first year was 3.7. The team noted that this aligns with long-term findings from MycarinG and two extension studies, in which the mean number of cycles in the first year was 4.1.
Statistical analyses estimated that 50% of patients had started a second cycle by day 58, or about the eight-week mark, after the last infusion of the first cycle.
Recording MG-ADL scores was not mandatory, and follow-up scores, most commonly just one, were captured for 29 patients over up to 1.5 years. Most scores were recorded about one month after the first cycle. The greatest mean MG-ADL score reduction was of 2.6 points, which is considered clinically meaningful, the researchers noted.
According to the researchers, “the addition of real-world data to existing clinical data provides a richer data set that is more reflective of the complete patient population.” The team added that these new findings “potentially [facilitate] discussions on cycle frequency with patients and managing treatment expectations.”
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