What is congenital athymia?

Congenital athymia is a rare immune condition that causes life-threatening immunodeficiency^1,2

Congenital athymia is a primary immunodeficiency characterized by the lack of a functioning thymus at birth, leading to an increased susceptibility to life-threatening infections.^1,3

The thymus is the only organ where T-cell progenitors can undergo positive and negative selection to become naive T cells.¹

Diagram of the thymus' function

Infant being monitored by medical equipment

Congenital athymia has been associated with multiple conditions¹

Congenital athymia has previously been referred to as complete DiGeorge anomaly, but has since been associated with other genetic conditions, congenital syndromes, and environmental exposures. These may include^1,2:

Complete DiGeorge syndrome (22q11.2 deletion syndrome)
CHARGE* syndrome
FOXN1 deficiency
Diabetic embryopathy

These multifaceted conditions and syndromes make managing congenital athymia even more challenging.¹
See how congenital athymia is diagnosed

*Coloboma, heart defects, atresia of the nasal choanae, retardation of growth and development, genitourinary anomalies, and ear anomalies.

Understanding the difference between congenital athymia and other primary immunodeficiencies is critical for early diagnosis.¹

Explore diagnosis

RETHYMIC is a first-of-its-kind, FDA-approved tissue-based treatment for congenital athymia engineered to help patients develop an immune system sufficient to fight infections.^5,6

Learn about RETHYMIC

RETHYMIC Connect™ provides support and resources for patients with congenital athymia and their caregivers.

Enroll your patients

Indication and Important Safety Information

Important Safety Information

Infection Control and Immunoprophylaxis: Immune reconstitution sufficient to protect from infection is unlikely to develop prior to 6-12 months after treatment with RETHYMIC. Follow infection control measures until the development of thymic function is established as measured by flow cytometry. Closely monitor patients for signs of infection. If fever develops, assess the patient via lab results and treat as clinically indicated. Patients should be maintained on immunoglobulin replacement therapy (IgG) and Pneumocystis jirovecii pneumonia prophylaxis until specified criteria are met. IgG trough level should be checked 2 months after stopping IgG to determine whether the patient may remain off IgG.

Graft versus Host Disease (GVHD): RETHYMIC may cause or exacerbate pre-existing GVHD, for which patients should be closely monitored and treated. Risk factors include atypical complete DiGeorge anomaly phenotype, prior hematopoietic cell transplantation (HCT), and maternal engraftment. Patients with specified elevated baseline T cell proliferative response to PHA should receive immunosuppressants to decrease this risk. GVHD may manifest as fever, rash, lymphadenopathy, elevated bilirubin and liver enzymes, enteritis, and/or diarrhea.

Autoimmune Disorders: Autoimmune-related adverse events occurred in patients treated with RETHYMIC. These events included thrombocytopenia, neutropenia, proteinuria, hemolytic anemia, alopecia, hypothyroidism, autoimmune hepatitis, autoimmune arthritis, transverse myelitis, albinism, hyperthyroidism, and ovarian failure. Monitor complete blood counts with differential, liver enzymes, serum creatinine, urinalysis, and thyroid function.

Renal Impairment: Pre-existing renal impairment is a risk factor for death.

Cytomegalovirus Infection (CMV): In the clinical studies, 4 out of 4 patients with pre-existing CMV infection died.

Malignancy: Due to underlying immune deficiency, patients who receive RETHYMIC may be at risk of developing post-treatment lymphoproliferative disorder. Patients should be tested for Epstein-Barr virus and CMV prior to and 3 months after treatment or after any suspected exposure.

Transmission of Serious Infections and Transmissible Infectious Diseases: Transmission of infectious disease may occur because RETHYMIC is derived from human tissue, and product manufacturing includes porcine- and bovine-derived reagents.

Vaccine Administration: Immunizations should not be given in patients treated with RETHYMIC until immune-function criteria have been met. Live virus vaccines should not be given until patients have met the criteria for and received inactivated vaccines.

Anti-HLA Antibodies: All patients should be screened for anti-HLA antibodies prior to receiving RETHYMIC. Patients testing positive should receive RETHYMIC from a donor who does not express those HLA alleles.

HLA Typing: HLA matching is required in patients who have received a prior HCT or a solid organ transplant. Patients who have received a HCT are at increased risk of developing GVHD after RETHYMIC if the HCT donor does not fully match with RETHYMIC.

Deaths: Of the 105 patients in clinical studies, 29 patients died, including 23 deaths in the first year (<365 days) after implantation.

Adverse Reactions: The most common (>10%) adverse events included hypertension, cytokine release syndrome, rash, hypomagnesemia, renal impairment/failure, thrombocytopenia, and GVHD.

Indication

RETHYMIC® is indicated for immune reconstitution in pediatric patients with congenital athymia.

Limitations of Use: RETHYMIC is not indicated for the treatment of patients with severe combined immunodeficiency (SCID).

References: 1. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 2. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/ 3. Markert ML, McCarthy EA, Gupton SE, Lim AP. Cultured thymus tissue transplantation. In: Sullivan KE, Stiehm ER, eds. Stiehm’s Immune Deficiencies: Inborn Errors of Immunity. 2nd ed. Elsevier; 2020:1229-1239.

References: 1. 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:10.1007/s10875-021-01059-7 2. Markert ML, Gupton SE, McCarthy EA. Experience with cultured thymus tissue in 105 children. J Allergy Clin Immunol. 2022;149(2):747-757. doi:10.1016/j.jaci.2021.06.028 3. Immune Deficiency Foundation. Patient & Family Handbook for Primary Immunodeficiency Diseases. 6th ed. 2019. 4. Hsieh EWY, Kim-Chang JJ, Kulke S, Silber A, O’Hara M, Collins C. Defining the clinical, emotional, social, and financial burden of congenital athymia. Adv Ther. 2021;38(8):4271-4288. doi:10.1007/s12325-021-01820-9 5. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 6. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/

References: 1. 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:10.1007/s10875-021-01059-7 2. Markert ML, Gupton SE, McCarthy EA. Experience with cultured thymus tissue in 105 children. J Allergy Clin Immunol. 2022;149(2):747-757. doi:10.1016/j.jaci.2021.06.028 3. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 4. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/

References: 1. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 2. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/ 3. Markert ML, McCarthy EA, Gupton SE, Lim AP. Cultured thymus tissue transplantation. In: Sullivan KE, Stiehm ER, eds. Stiehm’s Immune Deficiencies: Inborn Errors of Immunity. 2nd ed. Elsevier; 2020:1229-1239.

References: 1. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 2. Markert ML, Gupton SE, McCarthy EA. Experience with cultured thymus tissue in 105 children. J Allergy Clin Immunol. 2022;149(2):747-757. doi:10.1016/j.jaci.2021.06.028 3. Markert ML, McCarthy EA, Gupton SE, Lim AP. Cultured thymus tissue transplantation. In: Sullivan KE, Stiehm ER, eds. Stiehm’s Immune Deficiencies: Inborn Errors of Immunity. 2nd ed. Elsevier; 2020:1229-1239.

References: 1. Markert ML, McCarthy EA, Gupton SE, Lim AP. Cultured thymus tissue transplantation. In: Sullivan KE, Stiehm ER, eds. Stiehm’s Immune Deficiencies: Inborn Errors of Immunity. 2nd ed. Elsevier; 2020:1229-1239. 2. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 3. Food and Drug Administration. Summary Basis for Regulatory Action. October 8, 2021. BLA STN: 125685/0 4. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/

References: 1. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 2. Sumitomo Pharma America, Inc. Enzyvant receives FDA approval for RETHYMIC® (allogeneic processed thymus tissue-agdc), a one-time regenerative tissue-based therapy for pediatric congenital athymia. Accessed June 27, 2024. https://www.us.sumitomo-pharma.com/newsroom/press-releases/Enzyvant-Receives-FDA-Approval-for-RETHYMIC-allogeneic-processed-thymus-tissue-agdc-a-One-Time-Regenerative-Tissue-Based-Therapy-for-Pediatric/

References: 1. Hsieh EWY, Kim-Chang JJ, Kulke S, Silber A, O’Hara M, Collins C. Defining the clinical, emotional, social, and financial burden of congenital athymia. Adv Ther. 2021;38(8):4271-4288. doi:10.1007/s12325-021-01820-9 2. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023.

References: 1. RETHYMIC [package insert]. Marlborough, MA: Sumitomo Pharma America, Inc; 2023. 2. Markert ML, McCarthy EA, Gupton SE, Lim AP. Cultured thymus tissue transplantation. In: Sullivan KE, Stiehm ER, eds. Stiehm’s Immune Deficiencies: Inborn Errors of Immunity. 2nd ed. Elsevier; 2020:1229-1239 3. Gupton SE, McCarthy EA, Markert ML. Care of children with DiGeorge before and after cultured thymus tissue implantation. J Clin Immunol. 2021;41(5):896-905. doi:10.1007/s10875-021-01044-0