UCB Secures FDA Approval for Rare Disease Treatment Kygevvi, Continuing Strong Performance

Belgian pharmaceutical company UCB has received FDA approval for Kygevvi, a groundbreaking treatment for the ultra-rare genetic mitochondrial disease thymidine kinase 2 deficiency (TK2d). This approval marks UCB's third rare disease drug approval in less than three years, reinforcing the company's position in the rare disease market.

Kygevvi: A Targeted Approach to TK2d

Kygevvi, an oral solution comprising doxecitine and doxribtimine, is the first targeted medicine for TK2d, a muscle-weakening disorder that affects an estimated 1.64 in every 1 million people. The treatment is approved for both adult and pediatric patients who experience symptom onset by age 12.

TK2d can be particularly aggressive when it appears early in life, potentially leading to death within three years of symptom onset. The disease impairs patients' ability to walk, eat, and breathe independently.

Dr. Michio Hirano, a professor of neurology at Columbia University's Irving Medical Center, emphasized the significance of this approval: "We have been waiting for an approved treatment for many years, and this approval marks a significant milestone in how we can support and manage this debilitating condition."

Clinical Efficacy and Launch Plans

The FDA's decision was based on results from a phase 2 trial that demonstrated Kygevvi's ability to reduce the risk of death by 86% compared to an external control group of untreated patients. The study matched participants based on age at symptom onset.

UCB plans to launch Kygevvi in the first quarter of 2026, with European regulatory review currently underway. Donatello Crocetta, UCB's chief medical officer, stated, "The approval of doxecitine and doxribtimine represents a pivotal moment for the TK2d community, who previously had no FDA-approved treatment options for this rare genetic mitochondrial disease beyond supportive [palliative] care."

UCB's Growing Momentum in Rare Diseases

This latest approval continues UCB's positive trajectory in the rare disease space. The company has experienced significant growth, largely driven by the success of Bimzelx, approved for plaque psoriasis in 2023. Bimzelx generated sales of 799 million euros ($918 million) in the first half of this year.

Additionally, UCB's myasthenia gravis drugs Rystiggo and Zilbrysq, both approved in 2023, contributed 239 million euros ($274 million) in combined sales during the same period.

The company's strong performance is reflected in its financial results, with a 25% increase in revenue in the first half of 2025 and a 41% rise in market cap in the third quarter – the highest among top-20 companies in the industry.