Yes — the active ingredient is metabolized by a gene known to vary between individuals.
Relevant genes: IFNL3
Pegasys is affected by pharmacogenetics through the IFNL3 gene. Your genotype for this gene can change how your body processes Pegasys, which can affect both how well it works and how well you tolerate it. The strongest evidence level on this page is Strong, based on CPIC or FDA guidelines.
Published guidance from CPIC on how peginterferon alfa-2a should be dosed or substituted based on your IFNL3 phenotype.
| Phenotype | What it means | Recommendation | Evidence |
|---|---|---|---|
|
Favorable response genotype
IFNL3
|
"Your body has a higher chance of responding well to a medication called peginterferon alfa-2a. This could potentially lead to a shorter treatment period, but it's ultimately your doctor's decision to choose the best plan for you." |
CPIC
Approximately 90% chance for SVR after 24-48 weeks of treatment. Approximately 80-90% of patients are eligible for shortened therapy (24-28 weeks vs. 48 weeks)d. Weighs in favor of using PEG-IFN alpha and RBV containing regimens.
|
Strong |
|
Unfavorable response genotype
IFNL3
|
"Your genetic test result suggests that the medication peginterferon alfa-2a may not work as well for you. However, changes to your treatment plan and duration could improve its effectiveness. Your doctor will help decide the best approach for you." |
CPIC
Approximately 60% chance for SVR after 24-48 weeks of treatment. Approximately 50% of patients are eligible for shortened therapy (24-28 weeks). Consider implications before initiating PEG-IFN and RBV containing regimens.
|
Strong |
Source: CPIC
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.
Get your report Look up another medicationInformational 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.