Long-term efficacy among participants switched to bictegravir/emtricitabinetTenofovir alafenamide (B/F/TAF) from dolutegravir/abacavir/lamivudine (DTG/ABC/3TC) with preexisting resistance and viral blips

BACKGROUND: Study 1844 demonstrated the safety and noninferior efficacy of switching to bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF) from dolutegravir/abacavir/lamivudine (DTG/ABC/3TC). Here we present resistance, viral blips, and virologic outcomes through the end of the study.
METHODS: Virologically suppressed adults switched to B/F/TAF or continued DTG/ABC/3TC in a double-blind (DB) manner through Week (W) 48; then all remaining participants received B/F/TAF in an open-label (OL) extension. Preexisting HIV-1 drug resistance was determined by cumulative historical genotypes (documented resistance to study drugs was excluded) and retrospective baseline proviral DNA genotyping (participants with resistance to study drugs detected post-switch remained on study). Viral blips (transient HIV-1 RNA '¥50 copies/mL) and outcomes based on last available on-treatment HIV-1 RNA were assessed for all participants with '¥1 on-treatment HIV-1 RNA measurement.
RESULTS: Altogether, 562 randomized and treated participants had HIV-1 RNA data in the DB phase (281 B/F/TAF, 281 DTG/ABC/3TC), and 545 participants received B/F/TAF and had post-switch data in the DB and/or OL phases (B/F/TAF duration median 96 weeks, maximum 168 weeks). Cumulative baseline genotypic data from historical (n=271) and/or proviral DNA (n=499) genotypes were available for 96% (522/545) of B/F/TAF-treated participants: 31% (161/522) had '¥1 preexisting primary resistance substitution (to NRTIs [9%; 48/522], NNRTIs [17%; 88/522], PIs [10%; 54/522], and/or INSTIs [3%; 16/522]). The average frequency of viral blips was 1% per timepoint with 25 participants (10 B/F/TAF, 15 DTG/ABC/3TC) experiencing '¥1 viral blip through W48 and 9 on B/F/TAF experiencing '¥1 blip after W48. There were 40 total blip events in the DB and OL phases; 85% (34/40) were <200 copies/mL. Four participants (1 B/F/TAF, 2 DTG/ABC/3TC, 1 both) experienced >1 blip (range 2 ' 4 blips). Viral blips were not associated with any baseline characteristic, preexisting resistance, or virologic failure. Through 168 weeks of B/F/TAF treatment, 98% (535/545) had HIV-1 RNA <50 copies/mL at their last visit, including 99% (159/161) with preexisting resistance. No participant developed drug resistance.
CONCLUSIONS: Virologic suppression was maintained for '¥2 years of B/F/TAF treatment, including in those with preexisting resistance or viral blips. Long-term suppression and the absence of treatment-emergent resistance demonstrate the durable efficacy of B/F/TAF.