Immunosuppressants

Immunosuppressants and pharmacogenetics

Also known as: Transplant medications

4 medications 4 brand products TPMTCYP3A5

Why pharmacogenetics matter for immunosuppressants

Immunosuppressants prevent organ rejection after transplant and control autoimmune conditions like lupus, inflammatory bowel disease, and rheumatoid arthritis. Pharmacogenetics is unusually critical in this class because the drugs have narrow therapeutic windows: too little and the immune system rejects the graft (or reactivates autoimmune disease), too much and infection or kidney damage follow. TPMT and NUDT15 guide azathioprine dosing; CYP3A5 guides tacrolimus.

TPMT testing before azathioprine is one of the oldest and most established pharmacogenetic tests. CYP3A5 testing before tacrolimus is increasingly routine at transplant centers because getting the initial dose right in the first week post-transplant is critical to graft survival.

Key genes in this class

TPMT

Thiopurine S-Methyltransferase

TPMT inactivates thiopurine drugs like azathioprine, mercaptopurine, and thioguanine. About 1 in 300 people of European descent has essentially no TPMT activity, and standard doses can cause life-threatening bone marrow …

CYP3A5

Cytochrome P450 3A5

CYP3A5 is unusual: most people of European descent carry a non-functional variant and don't produce active enzyme at all. Most people of African descent do. For drugs like tacrolimus (used …

Medications in this class with pharmacogenetic guidelines

Each link goes to the drug's full pharmacogenetics page with CPIC and FDA phenotype recommendations.

Abrocitinib CYP2C19 Azathioprine NUDT15 / TPMT Siponimod CYP2C9 Tacrolimus CYP3A5

Brand products in the Immunosuppressants class

Combined products and brand names for the medications above. Each links to a pharmacogenetic breakdown.

Which immunosuppressants is right for your genetics?

This page covers the pharmacogenetics of immunosuppressants in general. A Gene2Rx report tells you how your personal genotype interacts with every drug on this page.

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Informational only, not medical advice. Pharmacogenetic guidelines describe population-level patterns that inform prescribing decisions. Never start, stop, or change a medication without talking to your prescribing clinician.