Servier has entered into a definitive agreement to acquire KER-0193, a potential treatment for Fragile X syndrome (FXS), from Kaerus Bioscience in a deal worth up to $450 million. The acquisition represents Servier's first asset acquisition in neurology and marks a significant milestone in the company's 2030 strategy to establish a leading neurology franchise focused on rare diseases.
Novel Mechanism Targets Root Cause of Fragile X Syndrome
KER-0193 is an orally bioavailable small molecule modulator of BK channels that specifically addresses abnormal function of BK channels linked to the genetic cause of FXS. The drug represents a mechanistically novel approach by modulating BK channels to normalize nerve cell excitability, addressing the root pathophysiology of FXS rather than merely managing symptoms.
In preclinical studies, KER-0193 has demonstrated broad therapeutic-like effects on improving syndrome-relevant behavioral, sensory and cognitive deficits. The treatment was granted both Orphan Drug Designation and Rare Pediatric Drug Designations for the treatment of FXS by the U.S. Food and Drug Administration (FDA).
Strong Phase 1 Results Support Development
Kaerus Bioscience successfully completed a Phase 1 clinical study of KER-0193 in healthy volunteers in March 2025, which confirmed the treatment to be safe and well tolerated with excellent pharmacokinetics. The positive Phase 1 results provide a strong foundation for advancing into Phase 2 trials.
As part of the development strategy, Servier will prepare the launch of a Phase 2 clinical trial in 2026 in FXS patients in America and Europe.
Addressing Significant Unmet Medical Need
Fragile X syndrome is a rare genetic syndrome of neurodevelopment characterized by a wide range of cognitive and behavioral challenges. It is the most common genetic cause of intellectual disability and the leading single-gene form of autism spectrum disorder (ASD), affecting approximately 1 in 7,000 males and 1 in 11,000 females globally.
There are currently no approved treatments for FXS, which accounts for approximately 1% of ASD and intellectual disability cases globally. The condition affects approximately 122,000 diagnosed individuals in the seven major markets as of 2023.
Strategic Alignment with Neurology Expansion
"KER-0193 is Servier's first asset acquisition in neurology and so marks a significant milestone in our 2030 strategy, reinforcing our long-term commitment to establishing a leading neurology franchise focused on rare diseases," said Claude Bertrand, Executive Vice-President of R&D at Servier. "It reflects our determination to build a differentiated pipeline of innovative therapies for patients with underserved needs."
Dr. Robert Ring, Chief Executive Officer of Kaerus Bioscience, commented: "We strongly believe in the therapeutic potential of KER-0193 in Fragile X syndrome. Servier's firm commitment to neurology and global capabilities make it the ideal partner to further develop KER-0193 for patients worldwide."
Deal Structure and Market Potential
Under the terms of the agreement, Kaerus Bioscience will receive an upfront payment for the sale of KER-0193 and will also be eligible for development and commercial earn-out payments. The total value of the deal could reach up to $450 million.
The global orphan drugs market, which includes FXS therapies, is projected to grow at a 9.1% CAGR, reaching $486.51 billion by 2032. KER-0193's unique mechanism targeting BK channels differentiates it from competitors in the fragmented FXS treatment landscape, with peak sales estimates likely exceeding $500 million annually if approved.
The drug's orphan drug and rare pediatric disease designations provide regulatory and financial incentives, including seven years of market exclusivity and a rare pediatric disease voucher, which streamline regulatory pathways and reduce time-to-market.
