Last Review Date: 01/04/2024

Date of Origin: 01/04/2022

Dates Reviewed: 01/2022, 01/2023, 01/2024

1. Length of Authorization

Coverage will be provided for 1 dose only

2. Dosing Limits

A. Quantity Limit (max daily dose) [NDC Unit]:

• Rethymic slices: Up to 42 slices (approximately 55,000 mm² of Rethymic)

B. Max Units (per dose and over time) [HCPCS Unit]:

• Up to 42 slices (approximately 55,000 mm²) of Rethymic

3. Initial Approval Criteria

Coverage is provided in the following conditions:

Congenital Athymia † Ф  ^1,3

• Used for immune reconstitution in pediatric patients; AND
• Patient has a diagnosis of congenital athymia based on flow cytometry documenting fewer than 50 naïve T cells/mm³ (CD45RA+, CD62L+) in the peripheral blood or less than 5% of total T cells being naïve in phenotype (Note: Requests for naïve T-cell counts ≥50 cells/mm³ will be handled on a case-by-case basis); AND
  • Patient has athymia with a diagnosis of FOXN1 deficiency; OR
  • Patient has complete DiGeorge syndrome (cDGS), also referred to as complete DiGeorge anomaly (cDGA)§; AND
• Will not be used for the treatment of patients with severe combined immunodeficiency (SCID); AND
• Will not be used in patients with any of the following:
  • Heart surgery anticipated within 4 weeks prior to, or 3 months after, the planned Rethymic treatment date
  • Human immunodeficiency virus (HIV) infection
  • Deemed to be poor surgical candidates; AND
• Benefits and risks of treatment have been discussed with patients who have a pre-existing CMV infection or who have renal impairment; AND
• Patient has been screened for anti-HLA antibodies (Note: Patients who have previously received a hematopoietic cell transplant with a mismatched allele require HLA matching of the thymus to that allele); AND
• Patient will receive IVIG replacement and prophylactic antimicrobials prior to and after transplant until immune reconstitution (according to infection control protocols) occurs (Note: Immune reconstitution sufficient to protect from infection is unlikely to develop prior to 6-12 months after treatment with Rethymic); AND
• Patient will not receive live or inactivated vaccines until IVIG/immunosuppressive therapy is discontinued and immune reconstitution has occurred; AND
• Patients with elevated baseline T cell proliferative response to PHA ≥ 5,000 cpm or > 20-fold over background or have evidence of maternal engraftment will receive combination therapy with immunosuppressive agents (e.g., rabbit antithymocyte globulin with or without calcineurin inhibitors and/or steroids)

† FDA Approved Indication(s); ‡ Compendia Recommended Indication(s); Ф Orphan Drug

4. Renewal Criteria ¹

Coverage cannot be renewed.

5. Dosage/Administration ¹

6. Billing Code/Availability Information

HCPCS code:

• J3590 – Unclassified biologics
• C9399 – Unclassified drugs or biologicals  

NDC(s):

• Rethymic single-dose unit supplied with up to forty-two ready-to-use slices of processed thymus tissue: 72359-0001-xx

7. References

1. Rethymic [package insert]. Marlborough, MA; Sumitomo Pharma America, Inc.; July 2023. Accessed December 2023.
2. Collins C, Sharpe E, Silber A, Kulke S, Hsieh EWY. Congenital athymia: genetic etiologies, clinical manifestations, diagnosis, and treatment. J Clin Immunol. 2021;41(5):881-895. doi.org/10.1007/s10875-021-01059-7.
3. Markert ML, Gupton SE, McCarthy EA. Experience with cultured thymus tissue in 105 children. J Allergy Clin Immunol. Published online August 3, 2021. doi:10.1016/j.jaci.2021.06.028

Appendix 1 – Covered Diagnosis Codes

Appendix 2 – Centers for Medicare and Medicaid Services (CMS)

The preceding information is intended for non-Medicare coverage determinations. Medicare coverage for outpatient (Part B) drugs is outlined in the Medicare Benefit Policy Manual (Pub. 100-2), Chapter 15, §50 Drugs and Biologicals. In addition, National Coverage Determinations (NCDs) and/or Local Coverage Determinations (LCDs) may exist and compliance with these policies is required where applicable. Local Coverage Articles (LCAs) may also exist for claims payment purposes or to clarify benefit eligibility under Part B for drugs which may be self-administered. The following link may be used to search for NCD, LCD, or LCA documents: https://www.cms.gov/medicare-coverage-database/search.aspx. Additional indications, including any preceding information, may be applied at the discretion of the health plan. 

Medicare Part B Covered Diagnosis Codes (applicable to existing NCD/LCD/LCA): N/A