TK2d Patient Voices Elevated at FDA; United Mitochondrial Disease Foundation, MitoAction Champion First Ever Listening Session for this Rare Disease

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In a historic first, the Food and Drug Administration (FDA) held a listening session regarding Thymidine kinase 2 deficiency (TK2d), a rare mitochondrial disease and enzyme deficiency. The Jan. 31, 2022 videoconference -- cohosted by the United Mitochondrial Disease Foundation, MitoAction and TK2 Cures -- allowed the TK2d patient community to underscore the importance of new research and clinical trials for the disease.

Today, the United Mitochondrial Disease Foundation (UMDF) and MitoAction shared reactions from the historic dialogue held during a listening session with the U.S. Food and Drug Administration (FDA) regarding Thymidine kinase 2 deficiency (TK2d).

The Jan. 31, 2022, meeting, cohosted by UMDF, MitoAction and TK2 Cures, was requested by members of the TK2d community to help the FDA understand the vital importance of new research and clinical trials.

“Listening sessions like this are an integral part of helping the FDA understand the burden of TK2d,” said United Mitochondrial Disease Foundation President and Chief Executive Officer Brian Harman. “It’s imperative that we continue to lift up the voices of those who know this disease best – patients, their loved ones, researchers, and medical experts. We see this as an important first step in charting a course toward treatments and an eventual cure for TK2d.”

Said MitoAction Chief Executive Officer Kira Mann: “In addition to providing a platform for those affected by TK2d to share their journey, we recognize the importance for patients and caregivers to also gain an understanding around the FDA regulatory process. As patient advocacy organizations, we want to continue to provide opportunities for patients to be actively engaged in this process and to continue to raise their voices.”

Seven representatives from the TK2d patient community participated in the FDA videoconference, along with clinician Dr. Michio Hirano, M.D., of Columbia University.

Many of those present urged the FDA to act with expediency when it comes to potential TK2d treatments.

“I know the process of getting approval for medication. I have studied every aspect of his disease,” said Aneesa, mother of three-year-old Jeremiah, a TK2d patient. “I know the FDA and researchers need time. Sadly, for those with this disease, their fate doesn’t have time.”

UMDF and MitoAction shared their appreciation for the affected individuals and families who bravely shared their stories and Dr. Hirano for his expertise, as well as members of the FDA who listened intently and brought thoughtful questions to better understand the disease.

Thymidine kinase 2 deficiency, TK2 deficiency (TK2d), is a very rare genetic disease with approximately 100-200 individuals affected in the United States. TK2d is a mitochondrial disease and enzyme deficiency that is defined by muscle weakness with effects like difficulty breathing, limb weakness that impairs gait or causes loss of ability to walk, droopy or saggy eyelids, and trouble chewing and swallowing that is often treated with feeding tubes. Most TK2d patients experience onset of weakness in the pediatric age group, but occasionally onset is in adulthood. Early onset patients tend to progress more rapidly and suffer early mortality.

TK2d currently has no available FDA approved treatment, and treatment is focused on symptom management. The United Mitochondrial Disease Foundation (UMDF) and its partners are focused on advancing TK2d research, supporting clinical trials and generating awareness.

Founded in 1996, the United Mitochondrial Disease Foundation (UMDF) works to promote research and education for the diagnosis, treatment and cure of mitochondrial diseases and to provide support for affected individuals and families. Since its inception, the UMDF has funded nearly $14 million in research, making it the leading non-governmental contributor of grants focused solely on mitochondrial disease. Every year, UMDF provides support and education to thousands of patients and medical professionals across the globe. Learn more at

MitoAction is a nonprofit organization founded by patients, parents, and Boston hospital healthcare leaders who had a vision of improving quality of life for children and adults with mitochondrial disease. The organization began in 2005 as an idea and has evolved from a small New England support group to a dynamic, active service organization helping thousands of patients and families worldwide. Despite the growth of the organization, the mission remains the same: to make a measurable impact in the lives of those who are affected by mitochondrial disease. Learn more at

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