The current level of transmission of resistant strains of HIV in the US does not affect the outcome of treatment

The current increase in the transmission of resistant HIV strains to US antiretrovirals will not affect the success of treatment for patients taking first-line drugs and will not affect the effectiveness of ARV therapy in the near future, according to a large analysis published in the Clinical Infectious Diseases.

Fears related to the increase in the number of cases of transmission of HIV resistance to ARV therapy were the reason for the standard testing procedure in the United States since the early 2000s.

Although studies reported an increase in the prevalence of drug resistance, information on the likely effects of transferred drug resistance on new regimens based on integrase inhibitors was not available.

As the authors of the paper note, in the period from 2003 to 2015 in the clinics of Kaiser Permanente in Northern California, more than 4 thousand patients with HIV taking ARVT underwent genotypic testing of drug resistance.

Less than 14% of people reported drug resistance. The main mode of transmission was sex between men (60%).

The most common form of resistance was the absence of a virus response to non-nucleoside reverse transcriptase inhibitors (NNRTIs) (7.2% of all people) and nucleoside reverse transcriptase inhibitors (NRTIs) (5.8%). The resistance of HIV to the action of the protease inhibitor was less common (3.2%). Multiple resistance to different classes of drugs was registered in 1.9% of cases.

The annual testing of the median value of participants (305 people) and trend analysis showed that over time the prevalence of transmitted drug resistance increased by 5% per year (odds ratio 1.05, 95% CI 1.03-108, p <0.0001 ). Resistance to NNRTI increased by 11% a year (RR 1.11, 95% CI 1.08-1.15, p <0.001), and the prevalence of resistance to NRTI increased slightly.

The most common mutations of resistant strains of HIV were associated with high resistance to efavirenz or nevirapine (348 cases). Among all participants tested for resistance, less than 8% had some degree of resistance to efavirenz and 5% to rilpivirin.

Mutations of resistance to protease inhibitors were less common and in most cases were associated with drugs of this class that were no longer used for clinical purposes. Approximately 2% of the cohort had some degree of resistance to increased atazanavir and 0.3% to darunavir.

There is no reported resistance to integrase inhibitors.

The lack of evidence of the spread of HIV resistance to newer drugs in people with transmitted resistance indicates that most drug-resistant strains of HIV are transmitted by people who themselves have acquired a drug-resistant form of HIV, say the authors.

A study in the UK showed a similar pattern, while recent data analysis in Switzerland demonstrated that drug resistance does not affect treatment options.

"The evolution of US treatment guidelines for first-line regimens that include an integrase inhibitor [...] or [enhanced] darunavir means that preferred first-line regimens are very active in patients with susceptible drug resistance," conclude the study.