Kygevvi (Doxecitine and Doxribtimine)
Chemical Name: Doxecitine and Doxribtimine
Generic Available: No
Kygevvi (Doxecitine and Doxribtimine) is an FDA-approved therapy for the treatment of thymidine kinase 2 deficiency (TK2d) in adult and pediatric patients with an age of symptom onset on or before 12 years.
TK2d is an ultra-rare mitochondrial disease and enzyme deficiency defined by muscle weakness, breathing difficulty, limb weakness that impairs gait or causes loss of ability to walk, droopy or saggy eyelids, and trouble chewing and swallowing. While estimating TK2d population size is challenging, the most recent literature puts the disease’s prevalence at 1.64 patients per million people.
TK2d is caused by inherited mutations in TK2, a nuclear gene responsible for making a mitochondrial enzyme called thymidine kinase 2. These mutations reduce the amount and quality of mitochondrial DNA inside cells.
Clinical trials data showed treatment with Kygevvi reduced the overall risk of death from treatment start by approximately 86%.
Information for Patients | UCB
ONWARD® For Patient Support of KYGEVVI™ (doxecitine and doxribtimine)
UCB Cares
Phone Number: +1-844-599-CARE (2273)
Email Address: UCBCares@ucb.com
8am-8pm ET Monday-Thursday
8am-5pm ET Friday
The below information is provided by UMDF as an informational resource and does not substitute talking to your doctor. More information can be found at kygevvi.com.
Who is eligible for treatment?
Kygevvi is approved for the treatment of thymidine kinase 2 deficiency (TK2d) in adult and pediatric patients with an age of symptom onset on or before 12 years.
What should I talk to my doctor about before starting treatment?
Before starting Kygevvi, it’s important your healthcare provider understands all your medical conditions, especially if:
- have or have had liver problems
- are pregnant or plan to become pregnant
- are breastfeeding or plan to breastfeed
Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
What kind of diagnostic test is required before starting Kygevvi?
A prescription for Kygevvi will require genetic confirmation of a TK2d diagnosis, which traditionally is accomplished via genetic testing.
How is age of onset determined?
Your insurer will likely require some form of medical records showing that symptoms were present on or before age 12. The symptoms needed to demonstrate onset on or before age 12 could take many forms.
Remember, it is possible that someone developed symptoms as an infant or child but wasn’t diagnosed until after age 12. While symptoms may vary depending on the age of onset, the main symptom is typically muscle weakness. Symptoms may also include fatigue, trouble eating or breathing, and/or difficulty with motor skills like sitting up or walking.
How do I receive this treatment?
Kygevvi is a powder that is dissolved and taken orally or by feeding tube three times a day about 6 hours apart with food. Kygevvi should only be mixed with water and taken with food as directed. Make sure you follow the step-by-step instructions on how to dissolve the powder and take a dose.
What are the side effects of Kygevvi?
In clinical trials, the most common side effects reported were gastrointestinal symptoms such as diarrhea, abdominal pain, and vomiting.
Increased liver enzyme levels, which sometimes indicate that the liver is irritated, inflamed, or working harder than usual, in a patient’s blood were also common. Your healthcare provider should do blood tests to check your liver enzyme levels before starting treatment and during treatment.
Always report new or worsening symptoms to your healthcare provider. They may change your dose, temporarily stop, or permanently stop treatment. You can find more information on side effects here.
Can I take Kygevvi with my other medications or supplements?
Before starting Kygevvi, talk to your healthcare provider about all medications, vitamins, and supplements you take. While no major drug interactions have been reported, your doctor will consider your full medical history to ensure it is safe and effective for you. Kygevvi should only be mixed with water and taken with food as directed.
How is Kygevvi different from other treatments for TK2d?
Kygevvi is the first and only FDA-approved therapy specifically for treating TK2d. Unlike supportive care measures such as vitamins, supplements, and specialized nutrition, this medication is designed to address the underlying challenge in TK2d – impaired mitochondrial DNA replication. This approach aims to support mitochondrial function and energy production, which may help manage symptoms and slow disease progression.
How much does Kygevvi cost?
UCB has committed to making “medicines accessible in ways that are sustainable for people impacted by severe diseases, for UCB, and for society.” We’re told the price of Kygevvi will be made public along with timing on product availability here: How Much Should I Expect to Pay for KYGEVVI® (doxectine and doxribtimine)? | UCB
Will insurance cover Kygevvi?
Most private and federal insurance plans will cover rare disease therapies for the specific indication for which they are FDA approved, as Kygevvi for TK2d in adult and pediatric patients with an age of symptom onset on or before 12 years now is. A letter of medical necessity from the patient’s doctor will be required. Coverage will vary depending on your plan. Ask your healthcare provider or specialty pharmacy team to help you navigate prior authorizations and cost support.
If you receive a denial for Kygevvi when you believe you meet all the necessary requirements, please know you don’t have to face the appeals process alone. UMDF is here to support you with tools, resources, and guidance to help navigate insurance appeals. Our goal is to ensure that patients and families have the best chance of accessing the treatments they need. Reach out to UMDF Support for assistance at (888) 900-6486 or support@umdf.org. We are committed to standing alongside you every step of the way.
Is there financial assistance available?
Yes, via a program called Onward. You can find out more here: ONWARD® For Patient Support of KYGEVVI™ (doxecitine and doxribtimine)
Once enrolled, the Onward care coordinator is available to provide information about financial assistance.
When will it be available at my doctor’s office or pharmacy?
Kygevvi will be exclusively distributed via a specialty pharmacy. It will likely be available in Spring 2026.
Once everything is approved, how will I physically get the medicine?
To assist patients with the process, UCB has chosen PANTHERx Rare as their specialty pharmacy partner. PANTHERx Rare will work with UCB and your doctor and help coordinate directly with your insurance provider during the approval process.
To help with all this, UCB is offering a personalized support experience called Onward. Once you’ve enrolled in Onward, UCB will assign you a Care Coordinator, who will work alongside PANTHERx Rare to support your Kygevvi prescription, including:
- PANTHERx Rare will work with your doctor and help coordinate directly with your insurance provider during the approval process
- At the same time, your Care Coordinator will explain potential financial assistance options and keep you updated on your status
- Once approved, your dedicated pharmacy team at PANTHERx Rare will remind you how to appropriately prepare and administer KYGEVVI and provide ongoing coaching and check-ins as you start treatment
- Your Care Coordinator will also stay in contact to provide resources and personalized support tailored to your needs and experiences during treatment.
What should I talk to my doctor about before starting treatment?
Before starting Kygevvi, it’s important your healthcare provider understands all your medical conditions, especially if:
- have or have had liver problems
- are pregnant or plan to become pregnant
- are breastfeeding or plan to breastfeed
Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
What if a patient has TK2d, but doesn’t meet the requirement of having symptom onset on or before age 12?
For now, prescription coverage is limited to those with symptom onset on or before age 12.
If you’re already part of a compassionate use program, your treating healthcare provider will work with you and the manufacturer to ensure that your treatment plan is not interrupted.
Patients who do not receive coverage under their insurance plans, but who are at risk of severe disability or death, may pursue compassionate use access via their treating physician. Physicians would need to submit these requests to accessplus@ucb.com
Are patients with any other forms of mitochondrial disease eligible for the drug?
At this time, Kygevvi is FDA-approved only for the treatment of TK2d for patients with symptom onset on or before age 12. This means insurance coverage and access are currently limited to adult and pediatric patients that fit within those requirements. If you’re interested in therapies in development for other forms of mitochondrial disease, you can visit the UMDF Therapeutic Pipeline.
Can a doctor write me a prescription for Kygevvi even if I do not have TK2d?
Doctors are able to write a prescription for indications other than those approved by the FDA if they feel it is medically warranted (off-label use). While off-label use of medication is allowed in the USA, insurance coverage could be problematic. Insurance – both private and public – will typically only approve for use under the specific label, which is TK2d patients with symptom onset on or before age 12. If you have any questions about the potential role of Kygevvi in your medical care, please discuss this with your healthcare professional. You may also reach out to a clinician at any Mitochondrial Care Center, who have specific mitochondrial disease expertise.
I was in the clinical trial / Expanded Access Program and meet the new prescription criteria. What are the next steps for me to remain on the medicine?
If you’re already part of a compassionate use program for Kygevvi, your treating healthcare provider will work with you and the manufacturer to ensure that your treatment plan is not interrupted. After enrolling in Onward, a representative from UCB’s personalized support experience Onward should be in touch. If you have questions, reach out to your doctor who wrote the prescription.