Yes — the active ingredient is metabolized by a gene known to vary between individuals.
Relevant genes: IFNL3
PegIntron is affected by pharmacogenetics through the IFNL3 gene. Your genotype for this gene can change how your body processes PegIntron, 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-2b should be dosed or substituted based on your IFNL3 phenotype.
| Phenotype | What it means | Recommendation | Evidence |
|---|---|---|---|
|
Favorable response genotype
IFNL3
|
Your genetics suggest a favorable response to peginterferon alfa-2b for treating hepatitis C. You have a higher chance of clearing the virus and may be eligible for a shorter treatment course. |
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 genetics suggest a less favorable response to peginterferon alfa-2b for treating hepatitis C. You have a lower chance of clearing the virus with this treatment, and alternative therapies should be considered. |
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
IFNL3 produces a type III interferon that helps the immune system clear viral infections. A variant in the gene's regulatory region (rs12979860) was, for a long time, the strongest known predictor of who would clear chronic hepatitis C on the old interferon-plus-ribavirin regimen. C/C carriers had roughly double the cure rate of T/T carriers.
Modern direct-acting antiviral (DAA) drugs cure hepatitis C in virtually everyone, so IFNL3 testing is no longer used to choose therapy. It remains historically important and may matter for future immune-related indications.
Browse the full drug-class: Antivirals.
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.