New study provides insights into how drug resistance evolves

In the late 1980s, when HIV treatments were first introduced, patients would often develop resistance to those treatments within six months. The introduction of triple-drug treatment regimens in the 1990s was intended to change that. Even when the virus developed resistance to one treatment, there would be two other drugs that could knock it out, essentially mitigating drug resistance ... or so the theory went. Unfortunately, some patients still develop resistance, leaving scientists with a critical question to answer: Why?

source https://medicalxpress.com/news/2021-11-insights-drug-resistance-evolves.html