Rystiggo receives FDA approval, strengthening UCB’s myasthenia gravis portfolio

Belgian biopharmaceutical company UCB has announced that it has received approval from the US Food and Drug Administration (FDA) for its Rystiggo (rozanolixizumab) treatment.

Rystiggo is intended to treat generalised myasthenia gravis (gMG) in anti-acetylcholine receptor (AchR) or anti-muscle-specific tyrosine kinase (MuSK) antibody-positive adults.

Administered via subcutaneous injection, Rystiggo works as a humanised IgG4 monoclonal antibody, binding to the neonatal Fc receptor (FcRN). This reduces the circulation of the IgG antibody that drives gMG.

In a June 2023 statement, UCB claimed that Rystiggo is now the only FDA-approved treatment in adults for anti-AChR and anti-MuSK antibody-positive gMG, the two most common subtypes of gMG. It will be available in the US during the third quarter of 2023.

The approval comes from safety and efficacy data gathered in UCB’s Phase III MycarinG study (NCT03971422).

MG-ADL, a measurement tool for gMG, was used to assess the efficacy of Rystiggo. It assesses gMG’s impact on breathing, talking, chewing, swallowing, brushing teeth or hair, standing from a chair, vision and eyelid droop on a scale of zero (normal) to three (severely impaired). Using this tool, a patient’s overall functionality is graded a score out of 24.

The study found that patients receiving Rystiggo had an average 3.4-point reduction from the MG-ADL baseline, compared to a 0.8-point reduction in those receiving a placebo.

gMG is a rare disease, with an estimated prevalence of only 12.4 people per 100,000. It manifests in various ways, most notably causing severe muscle weakness. This is because the body attacks the communication system between nerves and muscles.

There have so far been five separate treatments available to gMG patients. AstraZeneca has historically led the market with its eculizumab and ravulizumab LA treatments; both complement C5 inhibitors. UCB acquired Ra Pharma in a $2.5bn takeover to acquire Zilucopan, another C5 inhibitor that could rival this dominance.

Rystiggo faces a battle on another front from argenx’s Vyvgard, another FcRN antagonist approved in 2021 for 80% of gMG patients that are anti-AChR positive.

This month, argenx obtained further approval for subcutaneous injection, making it a more versatile treatment. While argenx’s offerings will be tough competition for UCB in the anti-AChR positive arena, the Belgian biopharma retains an edge in the 15% of anti-MuSK positive patients.

GlobalData’s epidemiology database values the gMG market at $1.5bn across the seven major markets (United States, Germany, Spain, Italy, France, United Kingdom, and Japan). This is a significant increase from the $836m recorded in 2018, with the market predicted to grow even further to $1.9bn by 2028.

GlobalData’s senior neurology analyst Phillippa Salter believed the gMG market has potential and is becomingly increasingly competitive, highlighting an unmet need for refractory or difficult-to-treat disease. She added that UCB is well-positioned to become a “new key player” in this environment.

GlobalData is the parent company of Pharmaceutical Technology.