Development of a G118R mutation in HIV-1 integrase following a switch to dolutegravir monotherapy leading to cross-resistance to integrase inhibitors

Objectives

Dolutegravir shows a high barrier to resistance with no previously reported cases of acquired integrase mutations during first-line therapy. In this study, rapid development of the G118R mutation arose following a switch from first-line elvitegravir/cobicistat/tenofovir disoproxil fumarate/emtricitabine to dolutegravir monotherapy. The G118R mutation also arose in a treatment-experienced patient switched to dolutegravir monotherapy. The genetic basis for G118R selection and potential phenotypic outcome was ascertained.

Patient and methods

Genotypic analysis was performed on patients with virological failure (<1000 copies/mL) on dolutegravir-containing regimens. The Los Alamos database was queried for glycine codon 118 polymorphisms. Cell culture selections and phenotypic drug susceptibility assays assessed resistance via the G118R pathway.

Results

We report on two patients who developed viral failure while on dolutegravir monotherapy. Both patients had been on a current or previous regimen containing integrase inhibitors. Virological failure (<1000 copies/mL) emerged early within 2 months following the dolutegravir switch. The appearance of G118R in these two cases and subtype C and CRF02_AG in vitro selections were related to a rare GGA natural polymorphism at codon 118 (1.5% prevalence), facilitating a GGA to AGA transition. Cell culture selections were used to assess the in vitro progression of the G118R pathway leading to cross-resistance to all integrase inhibitors.

Conclusions

Although resistance to dolutegravir is typically rare, genetic polymorphisms and monotherapy can facilitate the acquisition of G118R.

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