Early versus delayed antiretroviral therapy based on genotypic resistance test: Results from a large retrospective cohort study

Abstract Rapid start of antiretroviral therapy (ART) pending genotypic resistance test (GRT) has been recently proposed, but the effectiveness of this strategy is still debated. The rate of virological success (VS), defined as HIV‐RNA < 50 copies/ml, with and without GRT was compared in drug‐naïve individuals enrolled in the Italian ARCA cohort who started ART between 2015 and 2018. 521 individuals started ART: 397 without GRT (pre‐GRT group) and 124 following GRT (post‐GRT group). Overall, 398 (76%) were males and 30 (6%) were diagnosed with AIDS. In the pre‐GRT group, baseline CD4+ cell counts were lower (p < 0.001), and viral load was higher (p < 0.001) than in the post‐GRT group. The estimated probability of VS in pre‐GRT versus post‐GRT group was 72.54% (CI95: 67.78–76.60) versus 66.94% (CI95: 57.53–74.26) at Week 24 and 92.40% (CI95: 89.26–94.62) versus 92.92% (CI95: 86.35–96.33) at Week 48, respectively (p = 0.434). At Week 48, VS was less frequent among individuals with baseline CD4+ cell counts <200 versus >500 (90.33% vs. 97.33%), log viral load <5.00 versus >5.70 log10 cps/ml (97.17% vs 78.16%; p < 0.001), and those treated with protease inhibitors or non‐nucleoside reverse transcriptase inhibitors versus those treated with integrase strand transfer inhibitors (p < 0.001). The rate of VS does not seem to be affected by an early ART initiation pending GRT results, but it could be influenced by the composition of the ART regimen, as well as immuno‐virological parameters.

At Week 48, VS was less frequent among individuals with baseline CD4+ cell counts <200 versus >500 (90.33% vs. 97.33%), log viral load <5.00 versus >5.70 log 10 cps/ml (97.17% vs 78.16%; p < 0.001), and those treated with protease inhibitors or nonnucleoside reverse transcriptase inhibitors versus those treated with integrase strand transfer inhibitors (p < 0.001). The rate of VS does not seem to be affected by an early ART initiation pending GRT results, but it could be influenced by the composition of the ART regimen, as well as immuno-virological parameters. until CD4+ cells count fell below 350 cells/mm 3 or in case of symptomatic infection. However, in the following years, many studies proved that early ART initiation, even among PLWH with good immunological status, reduced the risk of mortality, 2-5 HIV transmission 6 and occurrence of AIDS-defining events, 7 protecting from the risk of virologic failure 8 and the selection of HIV drugresistant strains. 9 Consequently, current international guidelines recommend starting ART as soon as possible, regardless of the CD4+ cell count. Moreover, in the last few years, a new strategy for ART initiation called "same-day" 10 or "rapid" 11 ART has been proposed, pushing forward the concept of "early initiation." According to this strategy, ART should be provided during the first visit or within a short period thereafter. However, the disadvantages or the potential risks of this strategy are still debated. 12 Indeed, this approach might not be the safest in patients with mental health disorders, who are at risk for low compliance to ART, or whenever an underlying mycobacterial or cryptococcal opportunistic infection is suspected. Moreover, this strategy could be burdened by an increased risk of virologic failure due to undiagnosed transmitted drug resistance mutations. 13,14 Nevertheless, the advent of the newest ART regimens with a higher genetic barrier, like those containing the second-generation integrase strand inhibitors (INSTIs), has significantly reduced the risk of transmitted or acquired resistance-associated failure. 15 This stimulated the debate whether the availability of a genotypic resistance test (GRT) before treatment initiation is still needed.
Recent studies concluded that baseline GRT offers minimal clinical benefits and is not cost-effective, 15  For the present study, demographic, clinical, and treatment data, HIV-1 RNA load, CD4+ cell count, and drug resistance information were retrieved from ART-naïve PLWH who started treatment between 2015 and 2018 with at least 1 year of follow-up available.
Data of patients were retrieved from ART initiation since discontinuation, intended both as switch to other regimens or treatment interruption, for any cause.
VS was defined as the achievement of an HIV-1 RNA plasma value <50 copies/ml after the treatment initiation. Accordingly, the primary outcome was the probability of obtaining the VS at 24 and 48 weeks after ART initiation; on the contrary virological failure (VF) was defined as the first of two consecutive HIV-1 RNA plasma value >50 copies/ml or the at least one >200 copies/ml, after achievement of the VS.

| Pre-and post-GRT group categorization
The GRT was performed at diagnosis, or, when not feasible, within the next 72 h; in fact, the availability of a baseline GRT before the ART initiation is the "entry criteria" of ARCA cohort. In all cases, GRT testing was performed on plasma deriving from blood samples.
Accordingly, the date of diagnosis matches the date of GRT.
However, the actual date of GRT results availability is not recorded in the ARCA database. Therefore, a survey of the minimum time to acquire GRT after the blood sample collections was performed among centers included in the present study. In no case, the GRT was obtained in less than 14 days, except in selected and anecdotal cases with motivated request by clinicians; consequently, to divide individuals according to GRT availability, PLWH were categorized into (i) pre-GRT group, if ART was started within 14 days of GRT collection, assuming pending GRT; and (ii) post-GRT group, if ART was started more than 14 days after the date of GRT collection, assuming available GRT.

| Statistical analysis
The marginal and stratified survival distributions were estimated through the Kaplan-Meier product-limit estimator. The association between viral suppression and its predictors was evaluated by means of Cox proportional hazard regression at both univariable and multivariable levels. A significance level of α = 5% was specified before data analysis.
At multivariable analysis, for assessment of the independent prognostic performance of VS, we first performed variable selection through univariable analysis of all variables correcting the p value for false discovery rate (FDR) for multiple testing (q value < 0.01), and then including all the significantly associated confounders in the multivariable model. The differences of numerical covariate between the two groups were evaluated with unpaired t-test or Wilcoxon rank-sum test   PDRAMs associated with reduced susceptibility to NNRTIs were the most frequently identified; in particular, E138A/G/K was detected in 7.2%, followed by V106I in 3.2%, and K103N in 1.1%. For NRTIs, the more frequent PDRAM observed was M41L (1.1%), followed by D67N (0.9%) and L210W (0.6%) For PIs, L33F was detected in 2.8% and M46I/L in 1.7%. For INSTIs, only one case with T66I was found.
Concomitant resistance to two and three drug classes was detected in 4 (0.8%) and 1 (0.2%) cases, respectively, all in the post-GRT group. if compared with 2015 (41%; p < 0.001). As a consequence, the prescription of PI-based regimens and NNRTI-based regimens has reduced over the years (see Table S1, panel A). Similar results were found by replicating the analysis in the pre-and post-GRT groups (Table S1, panels B and C).   Figure 2B).

| First-line ART regimens
Baseline viral load also influenced the probability of achieving VS at 48 weeks ( Figure 2C) Figure 2D).
After performing a univariable Cox regression (Table S2)

| DISCUSSION
To the best of our knowledge, this study is one of the largest, which aimed to compare virologic outcomes of PLWH who started ART pending GRT versus those who started a GRT-based ART in a real-life setting. We did not detect any difference in the rate of virologic  GRT-based treatment choice was preferred. This is a possible explanation of the baseline difference between the two groups.
In line with previous studies conducted in Italy, 21  also in late or AIDS-presenters and/or with baseline RAMs. [21][22][23][24][25][26] In our cohort, NNRTIs were less frequently used in the pre-GRT group, probably because of the lower genetic barrier with respect to the other anchor drug classes. In the post-GRT group, NNRTIs were instead used more frequently than PIs (27% vs. 12%), probably due to the lower rate of drug-drug interactions and adverse effects and comparable level of effectiveness in absence of RAMs. 23  In conclusion, an early ART strategy with the current recommended first-line antiretroviral drugs starting pending GRT did not Further studies are needed to define the ideal profile of patients for whom rapid ART could not be a safe practice.