FDA Approves KYGEVVI® (doxecitine and doxribtimine), the First and Only Treatment for Adults and Children Living with Thymidine Kinase 2 deficiency (TK2d), a Rare and Devastating Mitochondrial Disease
This novel therapy offers the first FDA-approved option to address the root cause of this ultra-rare condition, which causes progressive muscle weakness impairing walking, breathing, and swallowing.
New York, Nov. 03, 2025 (GLOBE NEWSWIRE) -- New York, Monday, November 3, 2025 – The Muscular Dystrophy Association (MDA) marks another milestone today in our legacy of progress with the FDA approval of KYGEVVI® (doxecitine and doxribtimine), the first and only treatment for adults and children living with thymidine kinase 2 deficiency (TK2d), a rare and life-threatening mitochondrial myopathy. UCB will market the therapy in the U.S. Read their press release here.
“The approval today of KYGEVVI® (doxecitine and doxribtimine), provides real hope for
patients and families living with this devastating disease,” said Angela Lek, PhD,
interim Chief Research Officer at MDA. “Our longstanding investment in mitochondrial
disease research and clinical trial support has helped pave the way for this breakthrough,
and it reflects the power of a united community, scientists, families, advocates, all working
together toward treatments that improve lives.”
At the 2025 MDA Clinical & Scientific Conference, UCB presented compelling data
showing significant benefits for people living with TK2d. For those whose symptoms
began at age 12 or younger, treatment reduced the risk of death by over 90%. Additionally,
75% of these patients regained at least one previously lost motor skill, and many were
able to reduce or stop ventilatory support. The therapy was generally well tolerated, with
diarrhea as the most commonly reported side effect. TK2d profoundly impacts people’s
physical abilities and quality of life, as well as the emotional and physical wellbeing of
caregivers. Patient experience data presented alongside clinical results highlighted the
heavy burden TK2d places on families.
“After years of searching for treatment options, today’s approval represents a life
changing moment for our community,” said Olga Estopinan, MDA family member
whose son Arturito lives with mitochondrial myopathy. “It means more strength, more
time, and renewed hope for Arturito’s future.”
This milestone reflects decades of foundational research, clinical care, and advocacy led by
MDA since our founding in 1950, work that helped establish and shape the field of
neuromuscular disease research and care. MDA has long been a driving force behind
mitochondrial myopathy research. Early MDA research grant funding supported Dr. Michio
Hirano at Columbia University, an MDA Care Center, to develop a TK2-deficient mouse model,
which proved that targeted treatments could restore mitochondrial function. This led to FDA
granting compassionate use of the treatment that is now fully approved.
In 2024, MDA awarded approximately $482,000 in new research grants for mitochondrial
myopathy, including one funded in partnership with AFM-Téléthon. These grants are advancing
promising work on mitochondrial gene expression and structural integrity at leading institutions
where MDA funds research and care nationwide. MDA has invested more than $26 million in
research to advance treatments for mitochondrial myopathy.
“Bringing this therapy to FDA approval has been the culmination of decades of research and
collaboration,” said Michio Hirano, MD, MDA Care Center Director and Professor of
Neurology at Columbia University and Principal Investigator of the TK2d program. “We
saw the potential of pyrimidine nucleosides to restore mitochondrial function early in our mouse
studies. When Arturito Estopinan's condition rapidly declined, we sought compassionate use
because we believed in the science, and more importantly, in the urgent need to act. Today’s
approval validates that hope for many families.”
“Today’s approval is not only a medical breakthrough, it’s a testament to what’s possible when
advocacy, science, and regulatory policy align in service of people living with neuromuscular
conditions,” said Paul Melmeyer, Executive Vice President, Public Policy and Advocacy at
the Muscular Dystrophy Association. “As a convener, the Muscular Dystrophy Association
works alongside the FDA to ensure that the voices of our community are heard and that
promising treatments can reach people like Arturito in urgent need. This milestone underscores
the power of community involvement in clinical research and the importance of accelerating
regulatory pathways that prioritize patients and save lives.”
“When Arturito was diagnosed, we were told there was nothing we could do. But we
refused to give up hope,” said Art Estopinan, MDA family member and father of Arturito
Estopinan, who received early access to the therapy through compassionate use. “Thanks to Dr.
Hirano and the Muscular Dystrophy Association, and this treatment, we have more time with our
son than we ever thought possible. Today’s approval means other families won’t have to wait
and wonder, they’ll have access to something that can truly change lives.”
MDA also supports multidisciplinary care for the families we serve through the nationwide
network of MDA Care Centers, many of which supported clinical trials of this therapy.
Watch the video story here.
For guidance and support MDA families may contact the MDA Resource Center by
phone 1-833-ASK-MDA1 (1-833-275-6321) or email ResourceCenter@mdausa.org.
Media inquiries contact press@mdausa.org.
About Muscular Dystrophy Association
Muscular Dystrophy Association (MDA) is the #1 voluntary health organization in the
United States for people living with muscular dystrophy, ALS, and over 300 other
neuromuscular conditions. For 75 years, MDA has led the way in accelerating
research, advancing care, and advocating support and inclusion of families living with
neuromuscular disease. MDA's mission is to empower the people we serve to live
longer, more independent lives. To learn more visit mda.org and follow MDA
on Instagram, Facebook, X, Threads, Bluesky, TikTok, LinkedIn, and YouTube.
About Muscular Dystrophy Association’s 75th Anniversary
In 2025, the Muscular Dystrophy Association proudly marks 75 years of legacy, impact
and momentum in the fight against neuromuscular diseases. Since our founding, MDA
has been at the forefront of research breakthroughs, providing access to
comprehensive care, and championing the rights of people living with muscular
dystrophy, ALS, and over 300 other neuromuscular diseases. This milestone has been
made possible by generations of dedicated support from people living with
neuromuscular disease, their families, researchers, clinicians, volunteers, and donors—who boldly drive our mission forward. As we look ahead, we remain committed to honoring this legacy, building on the impact we’ve made together, and continuing our momentum toward transformative progress for people living with neuromuscular disorders. Learn more at MDA75.org.
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Mary Fiance, National Vice President, Strategic Communications Muscular Dystrophy Association press@mdausa.org
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