Post-treatment expectations
Post-treatment care is critically important after your patient receives RETHYMIC1
Immune reconstitution sufficient to protect against infection is unlikely to develop prior to 6 to 12 months after treatment with RETHYMIC. For some patients, it may take up to 2 years.1
After treatment with RETHYMIC, patients will return to the care of the referring healthcare provider and should be monitored regularly for autologous graft versus host disease and autoimmune disorders. Tests for monitoring autoimmune disorders will include/measure1-3:
- Complete blood count with differential
- Liver enzymes
- Serum creatinine levels
- Urinalysis
- Thyroid function
Once T cells reach certain levels, additional testing can be done to determine if patients can discontinue the following3:
- Immunosuppressants
- Immunoglobulin (IgG) replacement therapy
- Antibiotics
- Antifungals
Inactivated and live vaccines should not be administered until requirements outlined in the RETHYMIC Prescribing Information have been met.1
Careful monitoring and isolation are required to ensure your patient avoids infections after treatment with RETHYMIC. Your patient should also be monitored for other complications, like graft versus host disease and autoimmune disorders. Consider how best to work with the care teams and caregivers of your patients to determine what measures can be lifted and when.1
For additional guidance, please see below.
Immunosuppressants and IgG replacement therapy
Discontinuing immunosuppressants and IgG replacement therapy
Patients can be weaned off immunosuppressants when at least 10% of CD3+ T cells are naive in phenotype.1
- Patients should be maintained on IgG replacement therapy until all of the following criteria are met1:
- No longer taking immunosuppressants
- At least 9 months post-treatment
- Phytohemagglutinin response within normal limits
- Normal serum immunoglobulin A is desired but not required
Two months after stopping IgG replacement therapy, the IgG trough level should be checked. If the trough level is in the normal range for age, the patients can remain off therapy. If it is lower than the normal range for age, therapy should be restarted and continued for a year before being retested.1
Prophylaxis for Pneumocystis jirovecii
Discontinuing prophylaxis for Pneumocystis jirovecii
Patients should be maintained on Pneumocystis jirovecii pneumonia prophylaxis until all of the following criteria are met1:
- No longer taking immunosuppressants
- At least 9 months post-treatment
- Phytohemagglutinin response within normal limits
- CD4+ T cell count is >200 cells/mm3
Live and inactivated vaccines
Administering vaccines
Inactivated vaccines may be administered to patients who have received RETHYMIC when all of the following criteria have been met1:
- No longer taking immunosuppressants
- IgG replacement therapy has been discontinued
- Total CD4+ T cell count is >200 cells/mm3 and there are more CD4+ T cells than CD8+ T cells
Live virus vaccines should not be administered until the criteria for inactivated vaccines have been met and the patient has received vaccinations with inactivated agents (eg, tetanus toxoid).1
It is recommended that no more than 2 inactivated vaccines be given per month. With the exception of the inactivated influenza vaccine, no vaccines should be given within 6 months after the patient receives a measles-containing vaccine or within 2 months of receiving the varicella vaccine. Consider verifying response to vaccination with appropriate testing, in particular varicella and measles.1
Isolation
Relaxing strict isolation
As patients' immunities build and reach thresholds for fighting off infections, consider how best to work with the care teams and caregivers of your patients to determine what measures can be lifted and when.1
The efficacy and safety of RETHYMIC were studied across 10 clinical trials.1
Find useful information about congenital athymia and RETHYMIC for you and your patients’ caregivers.
Enzyvant CONNECT provides support and resources for patients with congenital athymia and their caregivers.
Indication and Important Safety Information
Important Safety Information
Immune reconstitution sufficient to protect from infection is unlikely to develop prior to 6-12 months after treatment with RETHYMIC. Given the immunocompromised condition of athymic patients, follow infection control measures until the development of thymic function is established as measured through flow cytometry. Monitor patients closely for signs of infection including fever. If a fever develops, assess the patient by blood and other cultures and treat with antimicrobials as clinically indicated. Patients should be maintained on immunoglobulin replacement therapy until specified criteria are met, and two months after stopping, IgG trough level should be checked. Prior to and after treatment with RETHYMIC, patients should be maintained on Pneumocystis jiroveci pneumonia prophylaxis until specified criteria are met.
RETHYMIC may cause or exacerbate pre-existing graft versus host disease (GVHD). Monitor and treat patients at risk for the development of GVHD. Risk factors for GVHD include atypical complete DiGeorge anomaly phenotype, prior hematopoietic cell transplantation (HCT) and maternal engraftment. GVHD may manifest as fever, rash, lymphadenopathy, elevated bilirubin and liver enzymes, enteritis, and/or diarrhea.
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 for the development of autoimmune disorders, including complete blood counts with differential, liver enzymes, serum creatinine, urinalysis, and thyroid function.
Pre-existing renal impairment is a risk factor for death.
In the clinical studies of RETHYMIC, 4 out of 4 patients with pre-existing cytomegalovirus infection died. The benefits/risks of treatment should be considered prior to treating patients with pre-existing CMV infection.
Because of the underlying immune deficiency, patients who receive RETHYMIC may be at risk of developing post-treatment lymphoproliferative disorder. Patients should be monitored for the development of lymphoproliferative disorder.
Transmission of infectious disease may occur because RETHYMIC is derived from human tissue and because product manufacturing includes porcine- and bovine-derived reagents.
Immunizations should not be administered in patients who have received RETHYMIC until immune-function criteria have been met.
All patients should be screened for anti-HLA antibodies prior to receiving RETHYMIC. Patients testing positive for anti-HLA antibodies should receive RETHYMIC from a donor who does not express those HLA alleles. HLA matching is required in patients who have received a prior HCT or a solid organ transplant. Patients who have received a prior HCT are at increased risk of developing GVHD after RETHYMIC if the HCT donor did not fully match the recipient.
Of the 105 patients in clinical studies, 29 patients died, including 23 deaths in the first year (< 365 days) after implantation.
The most common (>10%) adverse events related to RETHYMIC included: hypertension, cytokine release syndrome, rash, hypomagnesemia, renal impairment/failure, thrombocytopenia, and graft versus host disease.
To report suspected adverse reactions, please contact the FDA at 1-800-FDA-1088 or www.fda.gov/safety/medwatch
Indication
RETHYMIC® (allogeneic processed thymus tissue–agdc) 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. 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