Jul 26, 2003
Dear Dr. Wohl, I hope you realize what a great service you provide to all of the readers of your forum. You are very kind, thoughtful and knowledgeable. My question regards Epivir resistance. It seems that is a pretty common occurrence and I am pretty sure I have it (won't know until genotype in). If someone has Epivir resistance, what does that mean exactly? Would that person be immune to the entire class of drugs? Thank you very much for your time, JB
Response from Dr. Wohl
Thanks for your question and support.
Resistance to Epivir (3TC) is indeed very common and almost serves as a marker of 3TC exposure given how so many people on this drug develop resistance to it. The classic mutation that the virus develops to 3TC is called the 184V mutation.
This mutation is very interesting. For one thing, the 184V does not in and of itself lead to absolute resistance to any other drugs except for FTC which is a new medication that is very similar to 3TC. The mutation can decrease susceptibility of the virus to abacavir (Ziagen and a component of Trizivir) especially when other abacavir mutations also develop, but the 184V is definitely not a 'class killer'. Additionally, the 184V also seems to make the virus MORE susceptible to the antiviral effects of other drugs including AZT and tenofovir.
The 184V, like many drug resistance associated mutations, also has an effect on the virus to make it less fit compare to viruses without mutations. To survive with 3TC around the virus mutates, but it costs the virus as the mutant may not work as well as the non-mutated (wild type) virus. This is also called replication capacity.
So, yes, resistance to 3TC and FTC is common and may effect the ability of these drugs to kill the virus but there are some unexpected benefits of this resistance that can and are exploited in HIV treatment.
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