UCB wins Korea nod for Rystiggo in rare muscle-weakness disorder

UCB Korea has secured marketing approval from the Ministry of Food and Drug Safety (MFDS) for Rystiggo (rozanolixizumab), a weekly subcutaneous injection targeting adults with the autoimmune disorder of generalized myasthenia gravis (gMG) who test positive for acetylcholine receptors (AChR) and muscle-specific tyrosine kinase (MuSK) antibodies, the company said Monday.

The green light positions Rystiggo as an add-on to standard therapies in a disease marked by fluctuating muscle weakness and life-threatening respiratory crises.

About 10,000 patients are diagnosed with gMG in Korea, with roughly 85 percent progressing to generalized forms, according to 2023 data presented by UCB. Existing treatments, largely built around immunosuppressants, often show delayed effects and carry serious long-term risks, leaving significant unmet needs, the company said in Monday’s release. 

Rystiggo is a lab-made antibody that lowers harmful immune proteins linked to the disease. It works by blocking a natural process that normally protects antibodies, helping the body clear out the ones that mistakenly attack muscles.

UCB said the MFDS based its approval on the phase 3 MycarinG trial, which enrolled 200 gMG patients over six weeks. Patients receiving Rystiggo showed statistically significant improvements in daily living scores (MG-ADL), muscle strength (QMG), and composite symptom measures (MGC) compared with placebo. In the MG-ADL, for instance, Rystiggo patients saw a 3.37-point improvement versus 0.78 points with placebo (difference -2.59; 95 percent confidence interval, -4.09 to -1.25; p<0.0001) on day 43.

UCB Korea said follow-up data from an open-label extension study confirmed that symptom control was sustained over time. 

“We’ve long faced limitations in treating generalized gMG, with existing therapies showing delayed onset and low remission rates,” UCB Korea General Manager Hwang Su-jin said. “Rystiggo directly targets the autoantibodies that drive the disease, offering rapid symptom improvement as early as day eight of treatment and demonstrating superior response rates compared to placebo at every assessment point.”