Genotypizace UGT1A1: klinický pohled na metabolismus bilirubinu a toxicitu irinotekanu

UGT1A1 Genotyping: Clinical Insight into Bilirubin Metabolism and Irinotecan Toxicity

The UGT1A1 Promoter Polymorphism

The most clinically relevant genetic variation in UGT1A1 involves the number of TA repeats in the promoter region (TATA box) of the gene:

The wild-type allele (UGT1A1*1) contains six TA repeats (6TA).

The UGT1A1*28 variant (7TA/7TA homozygous) is the most common genetic cause of Gilbert syndrome in Caucasian and Afro-American populations. In these individuals, UGT1A1 activity may be reduced to 20–30% of normal, leading to mild chronic unconjugated hyperbilirubinemia. Alleles UGT1A1*36 (5TA) and UGT1A1*37 (8TA) are more frequently observed in individuals of African ancestry.

About the gb PHARM UGT1A1 Kit

The gb PHARM UGT1A1 is a CE IVD-certified in vitro diagnostic kit designed for genotyping TA-repeat polymorphisms in the UGT1A1 promoter region. The kit enables detection of:

• 5TA (UGT1A1*36)
• 6TA (UGT1A1*1 – wild type)
• 7TA (UGT1A1*28)
• 8TA (UGT1A1*37)

Melting curve analysis provides a reliable and precise method to distinguish between homozygous and heterozygous genotypes based on characteristic melting temperature profiles.

Clinical Implications

Gilbert Syndrome Diagnosis

UGT1A1 genotyping is commonly used to confirm Gilbert syndrome, a benign hereditary condition characterized by intermittent or persistent unconjugated hyperbilirubinemia without liver damage. Genetic confirmation prevents unnecessary diagnostic procedures and reassures patients.

Irinotecan Toxicity Risk

UGT1A1 is also responsible for the inactivation of SN-38, the active metabolite of the chemotherapeutic agent irinotecan. Patients carrying the **UGT1A128/28 genotype have reduced glucuronidation capacity, resulting in higher systemic exposure to SN-38 and increased risk of:

• Severe neutropenia
• Diarrhea
• Dose-limiting toxicity

Pharmacogenetic guidelines recommend considering dose reduction or careful monitoring in patients with homozygous UGT1A1*28 genotype prior to irinotecan therapy.

Clinical Interpretation Overview

Clinical Applications

UGT1A1 genotyping is recommended:

• To confirm Gilbert syndrome
• Prior to irinotecan treatment
• Before administration of other drugs metabolized by UGT1A1
• As part of personalized oncology protocols

Conclusion

The gb PHARM UGT1A1 kit provides a fast, reliable, and CE IVD-compliant method for detecting clinically significant UGT1A1 promoter polymorphisms. By identifying patients with reduced UGT1A1 activity, clinicians can:

• Improve diagnostic accuracy,
• Reduce the risk of chemotherapy-related toxicity,
• Support safer, personalized treatment strategies.

Radovan Haluza