PGx IRINOTECAN

Scientifically reviewed | Last updated
For more information see our editorial policy

UGT1A1

Irinotecan (a topoisomerase I inhibitor) is used to treat various types of cancer.

 

The enzyme UDP-glucuronosyltransferase (UGT1A1) plays a crucial role in the metabolism of irinotecan. Through glucuronidation, the active metabolite of irinotecan, SN-38, is converted into the inactive molecule SN-38G, allowing it to be excreted via the hepatobiliary or renal routes. The UGT1A1*6 and *28 alleles each lead to reduced UGT1A1 enzyme activity. As a result, the detoxification process for SN-38 is significantly impaired. Patients who are slow UGT1A1 metabolizers due to homozygosity or combined heterozygosity for the UGT1A1*6 and *28 alleles are at increased risk of accumulating SN-38 in their system, which may result in severe side effects at high doses of irinotecan, such as myelosuppression and difficult-to-treat diarrhea.

 

In December 2021, the German Federal Institute for Drugs and Medical Devices (BfArM) advised that a reduced starting dose of irinotecan should be considered for patients with decreased UGT1A1 activity. This recommendation applies to patients receiving doses above 180 mg/m² of body surface area or who are otherwise debilitated. Molecular genetic testing for the UGT1A1*28 and UGT1A1*6 alleles—both associated with reduced enzyme activity—is recommended. It should be noted that such testing cannot entirely rule out irinotecan toxicity, as other factors may influence drug tolerance.

 

Further information and current dosage recommendations can be found in various guidelines on irinotecan therapy (Dean L. et al, Bethesda [MD]: National Center for Biotechnology Information [US]; 2018) and in the PharmGKB database.

 

References

Red Hand Letter on Irinotecan-Containing Medicinal Products: Drug Toxicity in Patients with Reduced UGT1A1 Activity [in German]

 

Karas et al. 2021, JCO Oncol Pract 18:270 / Whirl-Carrillo et al. 2021, Clin Pharmacol Ther 110:563 / Dean L. 2018. In: Pratt V, McLeod H, Rubinstein W, et al., editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012) / Etienne-Grimaldi et al. 2015, Fundam Clin Pharmacol. 29:219 / Swen et al. 2011, Clin Pharmacol Ther 89:662

GENES
UGT1A1
HOW CAN YOU GET TESTED?
Step 1: Visit healthcare professional
Step 2: Sample collection (blood or buccal swab)
Step 3: Sequencing performed at our accredited laboratory
Step 4: Medical report
Step 5: Genetic counselling
FAQ

How does pharmacogenomic testing improve therapy with anticancer drugs?

Is pharmacogenomic testing recommended before starting cancer therapy with Irinotecan?

How long does it take to receive PGx Irinotecan test results?

CONTACT US

Please get in touch with us for any questions, inquiries, feedback or with any comments you might have.

LATEST ARTICLES

The endometrial microbiome is increasingly recognized as a factor in reproductive health, and imbalances in microbial composition have been linked to...

Read more

Spinal muscular atrophy is a rare genetic condition that weakens muscles by affecting the motor nerve cells in the spinal cord. It is a leading genet...

Read more

Summer encourages people to spend more time outdoors, soaking in the sun and enjoying the season’s warm weather. While sunlight can have beneficial...

Read more

We're thrilled to share the results of Medicover Genetics essay competition for high school students as well as the two winning essays. This competit...

Read more

Cystic fibrosis (CF) is a life-threatening, progressive, inherited condition that causes severe damage to the body, primarily affecting the organs of...

Read more

Down syndrome is a genetic condition caused by the presence of an extra copy of chromosome 21. It affects physical growth, facial features, and cogni...

Read more

Every year on April 25th, DNA Day celebrates the discovery of DNA’s double helix and the advances we’ve made in understanding genetics. D...

Read more

Neurodevelopmental disorders (NDDs) have diverse genetic origins, making diagnosis challenging. A new study analyzing over 1,100 pediatric patients f...

Read more

Colorectal cancer (CRC) remains one of the most prevalent and deadly cancers worldwide, with a significant number of cases presenting at an advanced ...

Read more

Carrier screening is a genetic test designed to identify whether an individual carries a gene with changes (mutations) associated with inherited diso...

Read more