Rystiggo, Zilbrysq earn EU approvals for adults with gMG

The UCB therapies are still under review in several other countries

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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The European Commission has approved Rystiggo (rozanolixizumab) as an add-on to standard therapy for the treatment of certain adults with generalized myasthenia gravis (gMG), closely following its clearance of Zilbrysq (zilucoplan) as an add-on treatment last month.

These medications are sold by the biopharma company UCB. Zilbrysq is indicated for adults who are positive for antibodies against acetylcholine receptors (AChRs), while Rystiggo is cleared for those patients as well as adults with antibodies against muscle-specific tyrosine kinase (MuSK).

Rystiggo is the first therapy in Europe to be cleared not only for AChR-associated gMG — the most common form of the disease — but also for patients with MuSK antibodies, which are less common and thought to be associated with a more severe presentation.

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“With the European Commission approval of [Rystiggo], alongside their recent approval of [Zilbrysq], I’m very excited that our gMG portfolio is now approved for use by healthcare professionals across Europe,” Jean-Christophe Tellier, CEO of UCB, said in a press release.

“Our unique and differentiated portfolio of medicines reinforces our commitment to redefining treatment expectations for the gMG community,” Tellier noted in an earlier press release announcing Zilbrysq’s approval in Europe.

The approvals are valid in all European Union member states as well as Iceland, Liechtenstein, and Norway. UCB expects both medications to become available to patients in those areas in the coming months.

Rystiggo and Zilbrysq were approved similarly in the U.S. last year. In Japan, both medications also were cleared, but only for patients who inadequately responded to steroids or other immunosuppressant medications.

UCB awaiting approvals in other countries

Applications for Rystiggo also are under review in China, Australia, Canada, the U.K., and Switzerland. Zilbrysq is under review in Australia, the U.K., Canada, South Korea, and Switzerland. Feedback from regulators in these countries are expected this year.

In gMG, self-reactive antibodies attack proteins involved in nerve-muscle communication, leading to symptoms of muscle weakness and fatigue. The two newly approved medications work by different mechanisms to dampen these autoimmune attacks.

“We believe there is still a significant unmet need within the gMG community which can be addressed by bringing differentiated, generally well-tolerated, and effective treatment options to patients that address key aspects of gMG pathophysiology [disease mechanisms],” Tellier said.

Rystiggo is an antibody that targets the neonatal Fc receptor (FcRn), a protein that prevents the breakdown of antibodies circulating in the bloodstream, including the ones implicated in MG.

By blocking FcRn, Rystiggo aims to speed the breakdown of these harmful antibodies and lower their levels in the bloodstream. It is delivered as an under-the-skin (subcutaneous) injection at a weight-based dose once a week for six weeks. After the first treatment cycle, additional cycles will be given based on a person’s response.

Zilbrysq, given once per day as a subcutaneous injection, targets the C5 protein. This protein is involved in the immune system’s complement cascade. Through this mechanism, Zilbrysq is intended to suppress complement-mediated damage to the nerve-muscle communication.

Approvals based mainly on 2 generalized myasthenia gravis trials

The clearance of each medication was largely backed by findings from a Phase 3 clinical trial. The MycarinG study (NCT03971422) showed that Rystiggo led to statistically significant and clinically meaningful reductions in measures of disease severity compared to a placebo, with efficacy observed in patients with either anti-MuSK or anti-AChR antibodies.

Common side effects included headache, infections, diarrhea, fever, and nausea.

Zilbrysq was tested in the RAISE trial (NCT04115293) involving patients with anti-AChR antibodies. As with Rystiggo, Zylbrisq was associated with significant reductions in symptom severity and improved life quality among these patients relative to a placebo. Common side effects included injection site reactions, upper respiratory tract infections, and diarrhea.

“We extend our gratitude to the patients, care partners, and investigators who participated in our clinical studies and who have shared their insights with us,” Tellier said.