Mayo Clinic Laboratories > Therapeutics > Precision therapeutics > Precision transplant therapeutics

Precision transplant therapeutics

Optimize outcomes with personalized drug monitoring

Precise immunosuppression is critical to transplant success. Small variations in drug levels — especially tacrolimus — can lead to rejection, toxicity, or serious complications.

With over 30,000 transplants performed annually in the U.S., a one-size-fits-all approach is no longer enough. Immunosuppressive therapy must be tailored to each patient’s evolving risk profile.

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Mayo Clinic Laboratories offers a precision-driven solution that combines:

  • Pharmacogenomics (PGx): Genetic testing (e.g., CYP3A5) to guide initial tacrolimus dosing in non-liver transplants.
  • Therapeutic drug monitoring (TDM): Real-time measurement to keep levels in range and reduce the risk of transplant rejection for all transplant types.
  • Expert clinical support: Access to Mayo Clinic’s transplant pharmacists, geneticists, and pathologists.
  • Decades of transplant leadership and research: Testing is supported by clinical trials, translational studies on antibody-mediated rejection, and multidisciplinary care protocols to improve outcomes in highly sensitized organ recipients — enabling faster, more informed decisions and better long-term results.

Precision transplant therapeutics test menu 

Cytochrome P450 3A5 (CYP3A5) and tacrolimus

CYP3A5 genotyping plays a critical role in personalizing tacrolimus therapy for non-liver transplant patients. Tacrolimus is metabolized primarily by CYP3A5 and has a narrow therapeutic index, making precise dosing essential to reduce the risk of rejection or toxicity.

Genetic variation in CYP3A5 significantly impacts how quickly a patient metabolizes tacrolimus. For example, individuals with at least one functional *1 allele (common in those of African ancestry) require higher initial doses to reach therapeutic levels. Conversely, those with two nonfunctional alleles—such as those with the *3/*3 genotype, which is more prevalent in individuals of European descent—do not require a dose adjustment based on their CYP3A5 genotype, but do metabolize the drug more slowly than those who carry a *1.

Key testing

Highlights


Therapeutic drug monitoring

While CYP3A5 genotyping offers important guidance for initial tacrolimus dosing, it does not capture the full complexity of drug metabolism, which is influenced by factors such as liver function, drug interactions, and patient adherence. It is also not likely to be predictive of metabolism in patients with a liver transplant, due to the test reflecting the patient’s original liver they were born with but not the new donor liver.

Immunosuppressants like tacrolimus, cyclosporine, and sirolimus all have narrow therapeutic windows and significant variability in absorption and response, making therapeutic drug monitoring (TDM) essential for ongoing dose adjustment.

By combining pharmacogenomic insights with real-time TDM, clinicians can optimize immunosuppression more safely and effectively, reducing the risks of rejection, toxicity, and long-term complications while improving graft survival.1

Key testing

Additional testing


References
  1. Lemke A, Wright J, May H. Pharmacogenomics and beyond! Customized pharmacotherapy for solid organ transplant recipients. Pharmacotherapy. 2023;43(7):596-608. doi:10.1002/phar.2798
  2. Clinical Pharmacogenetics Implementation Consortium (CPIC). Guideline for Tacrolimus and CYP3A5. Published Aug. 18, 2015. Updated Oct. 16, 2023. Accessed Feb. 17, 2025. https://cpicpgx.org/guidelines/guideline-for-tacrolimus-and-cyp3a5/
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