Is Tasigna affected by genetics?

Yes — the active ingredient is metabolized by a gene known to vary between individuals.

Relevant genes: UGT1A1

Used for: Chronic myeloid leukemia (CML), Philadelphia chromosome-positive

Tasigna (nilotinib) is a tyrosine kinase inhibitor used to treat CML, and it carries a notable pharmacogenetic story connected to UGT1A1. One of the drug's most closely watched side effects is elevated bilirubin (indirect hyperbilirubinemia), which can cause visible jaundice and sometimes forces dose reduction or treatment interruption. Patients who carry two copies of the UGT1A1*28 variant (which reduces the enzyme's ability to process bilirubin) have a significantly higher rate of clinically meaningful hyperbilirubinemia on nilotinib. This same variant is the basis of Gilbert's syndrome, a generally benign condition affecting roughly 5 to 10 percent of the US population. On nilotinib, though, it goes from benign curiosity to an actively managed clinical factor.

What's in Tasigna

nilotinib affected by UGT1A1

Affected by UGT1A1 · FDA · Moderate evidence

Nilotinib is metabolized by CYP3A4 but the clinically relevant genetic signal for dosing and side effects is UGT1A1 status, because nilotinib inhibits UGT1A1. In patients who already have reduced UGT1A1 activity (*28/*28 homozygotes), the combination of inherited reduced activity and drug-induced further inhibition elevates bilirubin levels markedly. The FDA label for Tasigna calls out UGT1A1 polymorphism as a factor in interpreting hyperbilirubinemia during treatment. Dose reduction generally resolves the elevation.

Read the full nilotinib genetics guide →

Nilotinib phenotype recommendations

Published guidance from FDA on how nilotinib should be dosed or substituted based on your UGT1A1 phenotype.

Phenotype	What it means	Recommendation	Evidence
Normal Metabolizer UGT1A1	Your body processes nilotinib at a normal rate. The standard dose should work as expected.	FDA Initiate therapy with recommended starting dose.	—
Intermediate Metabolizer UGT1A1	Your body processes nilotinib at a normal rate. The standard dose should work as expected.	FDA Initiate therapy with recommended starting dose.	—
Poor Metabolizer UGT1A1	Your body breaks down nilotinib more slowly than normal, which increases the risk of a buildup of bilirubin that can cause yellowing of the skin or eyes. Closer monitoring is recommended.	FDA Initiate therapy at standard dose with close monitoring for hyperbilirubinemia. Consider dose modification if elevated bilirubin occurs.	Moderate
Indeterminate UGT1A1	The impact of your genotype on response to this drug is unknown	FDA Initiate therapy with recommended starting dose.	—
Not available UGT1A1	The impact of your genotype on response to this drug is unknown	FDA Initiate therapy with recommended starting dose.	—

Source: FDA

The gene behind the guidance

UGT1A1 UDP Glucuronosyltransferase Family 1 Member A1

UGT1A1 clears bilirubin (the molecule that builds up in jaundice) and several drugs including irinotecan and nilotinib. A variant called *28, common in people of all ancestries, reduces UGT1A1 activity. It's the cause of Gilbert's syndrome, a benign condition, but it also makes cancer patients much more susceptible to severe side effects from irinotecan-based chemotherapy.

Oncology dosing of irinotecan is often adjusted down for patients carrying two copies of the UGT1A1*28 variant.

See all drugs affected by UGT1A1 →

Browse the full drug-class: Chemotherapy agents.

What this means for you

If you or a family member is starting Tasigna and a UGT1A1 test hasn't been ordered, it's worth asking about. The test is inexpensive and the clinical context (a drug that causes hyperbilirubinemia in a UGT1A1-dependent way) is exactly the setting where knowing your genotype up front saves time. A positive result doesn't mean avoiding nilotinib; it means anticipating the need for closer monitoring and potentially earlier dose adjustment.

FAQ

Is UGT1A1 testing required before Tasigna?

Not universally required, but recommended in practice and called out in the FDA label. Many oncology centers test UGT1A1 routinely when starting nilotinib, irinotecan (where it's even more actionable), or other UGT1A1-dependent drugs. If your center doesn't test routinely, asking for it is reasonable.

Is Tasigna the only CML drug affected by UGT1A1?

No. Other tyrosine kinase inhibitors have their own pharmacogenetic signals. Imatinib (Gleevec) is less UGT1A1-dependent but has CYP3A4 interactions that can affect plasma levels. Dasatinib and bosutinib have their own profiles. A UGT1A1 result is specifically useful for nilotinib; for other TKIs, different considerations apply.

Does Gilbert's syndrome mean I shouldn't take Tasigna?

No. Gilbert's syndrome is the benign name for the same UGT1A1*28 status. It just means your baseline bilirubin runs slightly elevated, and that nilotinib may push it higher. Most patients with Gilbert's syndrome tolerate nilotinib fine; the key is that your oncologist knows so that mild hyperbilirubinemia isn't mistaken for liver damage.

Find out how your genetics affect Tasigna

This page describes the general pharmacogenetics. A Gene2Rx report analyzes your own DNA to tell you which metabolizer group you fall into, across every medication.

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Informational only — not medical advice. Pharmacogenetic guidance describes population-level patterns; your individual response depends on many factors. Never start, stop, or change a medication without talking to your prescribing clinician.