Doxecitine and Doxribtimine (Kygevvi) Coverage Criteria
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Defines medical necessity and prior authorization criteria for Kygevvi for treatment of thymidine kinase 2 deficiency (TK2d) across applicable QualChoice lines of business.
Drug is now FDA approved - criteria updated per FDA labeling; extended initial approval duration from 6 to 12 months for this maintenance medication for a chronic condition; removed specific measures of positive response; references reviewed and updated.
Coverage Criteria
inv-01: Initial Therapy — Thymidine Kinase 2 Deficiency
Covered when ALL of the following are met:
See Appendix E for packet number guidance and Appendix D for symptom examples
inv-02: Continued Therapy — Thymidine Kinase 2 Deficiency
Covered when ALL of the following are met:
Approval duration 12 months
inv-03: Other Diagnoses/Indications
For requests not meeting the TK2d criteria, one of the following must apply:
References to specific policy numbers provided
Coverage for uses of Kygevvi that are not FDA‑approved and are not specifically addressed in this policy requires adequate supporting documentation. Per policy, non‑FDA indications are not authorized unless the provider supplies sufficient documentation of efficacy and safety in accordance with the referenced off‑label use policies (CP.CPA.09, HIM.PA.154, CP.PMN.53) or there is other documented evidence of coverage.
Requests for Kygevvi for non‑FDA approved indications that lack the required supporting evidence will not be authorized. Use for off‑label indications must comply with the referenced off‑label policies; absent that documentation, the request is considered not authorized.
Initial Therapy
inv-14: Initial Therapy — Initial therapy criteria for TK2d
Initial therapy criteria for TK2d:
See Appendix E for packet conversion and Appendix D for symptom examples
Continued Therapy
inv-15: Continued Therapy — Continued therapy criteria for TK2d
Continued therapy criteria for TK2d:
Approval duration 12 months
Provider Actions & Requirements
Prior Authorization: Submit evidence of diagnosis, prescriber, weight, and dose limits
Submit a prior authorization showing the member meets the listed clinical criteria for TK2d: documentation of a TK2 gene mutation, prescribing clinician (neurologist or metabolic disease specialist) or consultation, age of symptom onset ≤ 12 years, current weight in kg, and dosing within component limits (doxecitine ≤ 400 mg/kg and doxribtimine ≤ 400 mg/kg per day; total ≤ 800 mg/kg/day). Approvals are for 12 months and packet guidance is in Appendix E.
- Confirm genetic diagnosis: evidence of TK2 gene mutation
- Prescriber is a neurologist or metabolic disease specialist, or include consult note
- Document age of symptom onset (≤ 12 years) and relevant symptoms (see Appendix D)
- Provide current weight in kg for dose calculation
- Confirm requested dose does not exceed doxecitine 400 mg/kg and doxribtimine 400 mg/kg per day (see Appendix E for packet guidance)
- Note approval duration: 12 months
Step Therapy: No prior-agent requirements
No step therapy agents or prior failures are required by this policy; authorization decisions are based on meeting the diagnosis and the initial/continued therapy criteria listed in the policy.
Documentation Required: Provide clinical records and weight/dosing evidence
Include supporting clinical documentation with the authorization request—examples: office chart notes, laboratory results, and other clinical information demonstrating the member meets all approval criteria.
- Genetic test results confirming TK2 gene mutation
- Prescriber notes or consultation from neurologist/metabolic disease specialist
- Documentation of age of symptom onset and relevant clinical signs (see Appendix D)
- Current weight in kg and dosing calculations or packet count per Appendix E
- Progress notes showing response to therapy for continuation requests
Denial Risk: Off‑label (non‑FDA) uses require supporting off‑label policy evidence
Requests for non–FDA approved (off‑label) indications will be denied unless sufficient documentation of efficacy and safety is provided per the referenced off‑label use policies or an evidence of coverage allows it.
- Refer to off‑label use policies: CP.CPA.09 (Commercial), HIM.PA.154 (Health Insurance Marketplace), CP.PMN.53 (Medicaid)
- If recent label changes within 6 months apply, follow the listed formulary/no‑coverage/non‑formulary policies per the policy text
Coding
| No codes listed |
Step Therapy
| Step | Requirement / Notes |
|---|---|
| 1 | No prior-agent step therapy is specified. Approval is based on meeting the diagnostic and prescribing criteria listed in the policy (e.g., confirmed TK2 gene mutation, prescribed by or in consultation with a neurologist or metabolic disease specialist, age of symptom onset ≤ 12 years, documentation of current weight, and dosing within component and total daily limits). |
Quantity Limits
Site of Care
Product form and site‑of‑care
Kygevvi is supplied as a powder for oral solution and may be administered in the home; the policy does not impose site‑of‑care restrictions.
- Product formulation: powder for oral solution (2 g doxecitine and 2 g doxribtimine).
Background
Kygevvi is a combination pyrimidine nucleoside therapy used for treatment of thymidine kinase 2 deficiency (TK2d). The policy specifies that coverage decisions— including for non‑routine or off‑label uses—follow the stated authorization criteria and that non‑FDA indications are not covered unless sufficient documentation of efficacy and safety is provided per the applicable off‑label use policies or evidence of coverage documents.
Definitions
Revision History
Drug received FDA approval; criteria updated to align with FDA labeling, initial approval duration extended from 6 to 12 months, and measures of positive response removed; references reviewed and updated.
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