Sacituzumab govitecan (Trodelvy)
A breast cancer medicine that carries its chemotherapy straight to the cancer cell. The same gene that matters for irinotecan, UGT1A1, changes how often its blood side effects happen.
What this drug connects to
The genes involved
Sacituzumab govitecan (Trodelvy), used for advanced triple-negative and some hormone-receptor-positive breast cancers, carries a chemotherapy that UGT1A1 clears. In its US label, severe drops in white blood cells happened in 57% of people with two copies of the slower UGT1A1*28 version, 48% with one and 41% with none, and came sooner in those with two copies: a median of 9 days against 19 and 21. The label does not lower the starting dose by genotype; it asks for close watching of people known to have low UGT1A1 activity.
US prescribing information for TRODELVY (sacituzumab govitecan-hziy), revised June 2026, section 5.5. This is the label itself, not a CPIC guideline.
How common these versions are, by ancestry
The share of people who carry at least one copy of each version. For the same medicine, it often differs more than tenfold between groups.
UGT1A1 *6 rs4148323 — a slower version of the enzyme
Worked out from each group's allele frequency: Korean from the Korean studies published in dbSNP, the rest from gnomAD's ancestry groups (via Ensembl), as the survey defines them, not races. How common a version is in a group says nothing about any one person; only a test does.
Questions about Sacituzumab govitecan (Trodelvy)
What is sacituzumab govitecan?
Sacituzumab govitecan, sold as Trodelvy, is an antibody joined to a chemotherapy drug. The antibody finds the cancer cell and delivers the chemotherapy there. In the US it is used for advanced triple-negative breast cancer and for some advanced hormone-receptor-positive breast cancers after other treatment.
What does UGT1A1 have to do with it?
The chemotherapy part is cleared by the liver enzyme UGT1A1, the same enzyme that matters for irinotecan. People with two copies of a common slower version, UGT1A1*28, clear it more slowly, and the label says they are at higher risk of low white blood cell counts and low red blood cell counts.
How big is the difference?
In the label, severe drops in white blood cells happened in 57% of people with two copies of UGT1A1*28, 48% with one copy and 41% with none. They also came sooner: a median of 9 days, against 19 and 21 days.
Does it change the dose?
The label does not set a lower starting dose by genotype. It asks the care team to watch people with known low UGT1A1 activity closely and to hold or stop the medicine if side effects need it. The medicine also carries a boxed warning about low white blood cell counts and diarrhoea for everyone.
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Sacituzumab govitecan (Trodelvy). MyGeneLog™. https://www.mygenelog.com/drugs/sacituzumab-govitecan