Increasing CD4/CD8 ratio confirmed after two years of long-acting cabotegravir and rilpivirine in the SCohoLART study

1 Introduction

Antiretroviral therapy (ART) for people with HIV (PWH) has undergone substantial evolution over the past two decades, yielding potent, safe, and increasingly convenient regimens that achieve durable virological suppression. Modern antiretroviral therapy (ART) has transformed HIV infection into a chronic condition, but lifelong daily oral therapy remains challenging due to adherence barriers, pill fatigue, stigma, and structural obstacles to continuous care (1). These limitations have driven the development of long-acting (LA) antiretroviral formulations designed to provide sustained drug exposure while reducing need on daily dosing. Among these, LA cabotegravir (CAB) and rilpivirine (RPV), administered intramuscularly every one or two months, constitute the first and only LA regimen approved for maintenance therapy in adult PWH on virological suppression (2).

Injectable CAB/RPV represents a paradigm shift by decoupling HIV treatment from daily oral intake. Data from pivotal clinical trials, including FLAIR, SOLAR, and ATLAS-2M, demonstrated that LA CAB/RPV was non-inferior to oral therapy in maintaining virological suppression and was associated with high treatment satisfaction (3–5). As the adoption of LA therapy expands, interest is increasing in its effects on immunologic, renal and metabolic parameters.

After initiating ART, CD4 restoration is well characterized; however, persistent CD8 expansion and failure of the CD4/CD8 ratio to normalize are recognized markers of immune activation, senescence, and increased risk of cardiovascular disease, malignancy, and mortality in PWH (6, 7). Despite effective viral suppression, many PWH under ART do not achieve a normalized CD4/CD8 ratio, making its change under newer treatment modalities clinically relevant. To date, the immunologic effects of LA CAB/RPV remain insufficiently defined. While pivotal trials on LA CAB/RPV primarily emphasized virological efficacy and safety, real world studies could allow a deeper examination of immune activation, lymphocyte subsets and inflammatory biomarkers.

Metabolic and renal outcomes constitute additional knowledge gaps. As PWH experience increased longevity, dyslipidemia, insulin resistance, weight gain, and cardiovascular disease have become prevalent (8). Several ART components, including some integrase inhibitors (INSTI), boosted protease inhibitors (PI) and tenofovir alafenamide (TAF), contribute to adverse metabolic profiles, whereas RPV generally exhibits neutral metabolic effects (9). Although LA CAB/RPV avoids TAF and other agents commonly associated with adverse metabolic effects, its long-term metabolic impact is not well defined. Clinical trials report minimal lipid changes and small improvements following discontinuation of regimens containing TAF or protease inhibitors, while real-world findings suggest modest lipid improvements but variable effects on weight (3–5, 10). Renal parameters also merit attention: pivotal studies showed a favorable renal safety profile, whereas real world data suggest a modest improvement of the renal function; however, available evidence remains limited (11).

This study evaluates the immunologic, metabolic, and renal effects of LA CAB/RPV in a real-world setting.

2 Materials and methods

The SCohoLART study (Cohort Study of HIV-positive People Treated with Long-Acting Antiretroviral Therapy; NCT05663580) is a single-center, prospective, phase IV observational cohort conducted at the Infectious Diseases Unit of the IRCCS San Raffaele Scientific Institute in Milan, Italy. The study aimed to systematically collect clinical and laboratory data from PWH who switched from oral ART to CAB/RPV while on virological suppression (12).

Baseline was defined as the date of switch to CAB and RPV. Plasma HIV-1 RNA was assessed at months 1, 3, and 6, and subsequently at six-month intervals; routine laboratory evaluations were conducted every six months in accordance with the clinical practice.

All the participants provided written informed consent. The study protocol received approval from the Ethics Committee of the IRCCS San Raffaele Scientific Institute on the 20^th of June 2022 (protocol 45/INT/2022) and was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines.

2.1 Statistical analysis

Baseline characteristics of study participants were summarized using appropriate descriptive statistics: continuous variables were reported as medians with interquartile ranges (IQR), while categorical variables were expressed as frequencies and percentages. To assess longitudinal changes in immunologic, metabolic, and renal parameters over time, linear mixed-effects models were employed. Each model included a random intercept for participants and a fixed effect for time, allowing estimation of crude annual mean changes (slopes) for each parameter. For all estimates, 95% confidence intervals (95% CI) were calculated, and statistical significance was evaluated using two-sided tests with a threshold of p < 0.05. Analyses were performed without adjustment for covariates to describe the observed trends in the cohort. To minimize potential confounding from concomitant lipid-lowering therapy, participants who initiated or discontinued statin treatment during follow-up were excluded from the analysis.

For immunologic outcomes, multivariable analyses were performed. To assess the impact of prior ART backbone, participants were categorized according to exposure to 0 or 1 nucleoside reverse transcriptase inhibitors (NRTI) versus 2 NRTI before switching to LA CAB/RPV. Effect modification was tested by including interaction terms between time and NRTI exposure group. Multivariable models were adjusted for age and CD4 nadir at baseline. Two-sided p-values <0.05 were considered statistically significant; interaction p-values were interpreted descriptively, with values close to 0.05 considered borderline significant.

3 Results

A total of 549 participants were included in the analysis. The cohort was predominantly male (91.3%), with a median age of 48.9 years (39.7–56.3). Participants had a long history of antiretroviral exposure, with a median duration of 11.3 years (7.9–17.3), had a median nadir CD4 of 335 (221-513) cells/microL and median CD4 count of 795 (604-994) cells/microL. The median follow-up time from the initiation of CAB/RPV was 24.0 months (17.0–26.8). Before switching to the LA regimen, participants were mainly receiving INSTI–based regimens (61.2%), followed by non-nucleoside reverse transcriptase inhibitors (NNRTI)-based regimens (25.3%), other regimens (10.6%), and protease inhibitors (PI)-based regimens (2.9%). Overall, 14 PWH (2.55% of all participants) were receiving a cobicistat-containing regimen. The distribution of the prior ART regimen is shown in Figure 1. Overall, 54 of 549 participants (9.8%) underwent an oral lead-in before initiating injectable therapy.

At the time of switching to the LA regimen, median CD4/CD8 ratio was 0.98 (0.70–1.28), accompanied by a median CD4 cell count of 795 cells/µL (604–994) and a median CD8 cell count of 850 cells/µL (642–1113). Metabolic and renal profiles at baseline were within expected ranges for the participants’ population: median total cholesterol was 179 mg/dL (158–201), and median LDL cholesterol was 112 mg/dL (95–135). Median serum creatinine was 1.1 mg/dL (0.9–1.20), with a median estimated glomerular filtration rate (eGFR) of 80 mL/min/1.73 m² (70–90). The characteristics of the participants at baseline are reported in Table 1.

Table 1. Characteristics of participants at baseline.

IQR, interquartile range; HDL, high-density-lipoprotein; LDL, low-density-lipoprotein; eGFR, estimated glomerular filtration ratio.

During follow-up, a progressive and statistically significant improvement in immunological markers was observed. The CD4/CD8 ratio increased by a yearly mean of 0.05 (95% CI 0.04–0.06; p <0.001), primarily driven by a decline in CD8 cell counts, which decreased by −27.90 cells/µL per year (p < 0.001). CD4 cell counts remained stable over time, supporting an overall favorable shift in immune balance. CD4/CD8 ratio and CD8 cell count changes are shown in Figure 2.

In multivariable linear mixed-effects models adjusted for age and CD4 nadir at baseline, CD8 cell counts showed a significant annual decline among participants previously exposed to 2 NRTI (−26.7 cells/µL per year; p=0.0024). In contrast, among those with 0/1 prior NRTI exposure, the estimated CD8 slope was negative but did not reach statistical significance (p=0, 1188). The interaction analysis did not demonstrate clear statistical heterogeneity between groups (p-inter=0, 5817).

For the CD4/CD8 ratio, a significant positive slope was observed in both groups after adjustment for age and CD4 nadir. The increase was numerically greater among participants previously exposed to 2 NRTI (0, 0515 vs 0, 0259; p-value <0.0001 and 0, 0300, respectively), although the interaction term was only borderline significant (p-inter 0, 0832).

Regarding metabolic outcomes, both total and low-dose-lipoprotein (LDL) cholesterol levels demonstrated modest but statistically significant reductions over time. Total cholesterol decreased by −1.72 mg/dL per year (p = 0.016), while LDL cholesterol declined by −4.40 mg/dL per year (p <0.001). Renal function also showed a favorable profile throughout follow-up. Median estimated glomerular filtration rate (eGFR) increased by +1.16 mL/min/1.73 m² per year (p <0.001), while serum creatinine decreased by −0.04 mg/dL per year (p <0.001), indicating a small but consistent improvement in renal parameters over time.

No significant changes were observed in body weight or body mass index (BMI) during the study period. Metabolic and renal slopes are summarized in Table 2.

Table 2. Yearly mean changes of metabolic and renal parameters after switching to long-acting cabotegravir/rilpivirine.

HDL, high-density-lipoprotein; LDL, low-density-lipoprotein; eGFR, estimated glomerular filtration ratio. In bold: statistically significant p-values.

4 Discussion

In this large, prospective real-world cohort of virologically suppressed people with HIV who switched to LA CAB/RPV, we observed favorable longitudinal trends in immunologic, metabolic, and renal parameters over a median follow-up of 24 months. Specifically, the CD4/CD8 ratio increased progressively over time, driven primarily by a sustained decline in CD8 cell counts, while CD4 cell counts remained stable. In parallel, modest but statistically significant reductions in total and LDL cholesterol were documented, and renal function showed gradual improvement, as reflected by increasing eGFR and decreasing serum creatinine. Collectively, these findings extend existing evidence by providing a comprehensive real-world assessment of systemic effects associated with LA CAB/RPV beyond virological maintenance.

The observed increase in the CD4/CD8 ratio represents a potentially clinically relevant immunologic trend. The CD4/CD8 ratio is widely regarded as an integrative marker of immune activation and immunosenescence and has been associated with non–AIDS-defining morbidity and all-cause mortality, even in individuals with long-term viral suppression and adequate CD4 recovery (13, 14). Persistent CD8 expansion and failure of ratio normalization have been linked to chronic inflammation, cardiovascular and oncologic risk (15). In this context, the consistent decline in CD8 cell counts observed in our cohort, accompanied by a stable CD4 compartment, may suggest a gradual shift toward immune restoration.

In multivariable models adjusted for age and CD4 nadir, different longitudinal patterns emerged according to prior NRTI backbone. Participants switching from regimens containing two NRTIs showed a statistically significant annual decline in CD8 cell counts, whereas among those previously exposed to 0/1 NRTI the estimated CD8 slope, although negative, did not reach statistical significance. Consistently, the CD4/CD8 ratio increased in both groups, but the magnitude of the increase was numerically greater in individuals discontinuing a 2-NRTI backbone. These findings suggest that the removal of a dual-NRTI backbone may be associated with a more pronounced improvement in immune restoration, characterized by a clearer reduction in CD8 expansion and a greater increase in the CD4/CD8 ratio compared with those switching from regimens containing 0/1 NRTI.

Immunologic changes under LA CAB/RPV were reported as secondary endpoints in pivotal phase 3/3b trials. Across these studies, CD4 cell counts generally remained stable or showed modest increases after switching to CAB/RPV. For example, ATLAS-2M reported a median CD4 cell count change of +5 cells/µL at week 48 in the group receiving LA CAB/RPV every 2 months (q8W), while the group receiving it every 4 weeks (q4W) demonstrated a median CD4 cell count change of −8 cells/µL at week 48 compared to baseline. Changes in both groups where not statistically significant (5).

Furthermore, in the phase 2b LATTE-2 trial, at week 256 of follow-up mean CD4 cell counts increased from week –20 by 326 cells/µL in the randomized q8W group and by 396 cells/µL in the randomized q4W group (16, 17).

Real-world data are still limited but generally align with our findings. In the context of the SCohoLART study, a similar trend was observed among individuals who switched to LA CAB/RPV from a second-generation integrase inhibitor–based regimen, with a mean increase of 0.08 in the CD4/CD8 ratio after one year of follow-up (18). In an all-female Italian population the mean CD4/CD8 ratio increased significantly by 0.1 at week 24 after switching to LA CAB/RPV (19).

Regarding CD8 cell count, recent prospective real-world data demonstrate a significant reduction in activated CD8 cells over 48 weeks of long-acting therapy, particularly in individuals switching from dual therapy regimens (20). Furthermore, a Japanese multicenter retrospective study on a population who switched to LA CAB/RPV demonstrated a significant decrease in both CD4 and CD8 cell counts, while no significant change in the CD4/CD8 ratio was observed after a median follow-up of 14 months (21).

The mechanisms which underlie these observations are unclear. The pharmacokinetic stability of long-acting formulations may reduce variability in drug exposure that can occur with imperfect adherence to daily oral regimens, potentially limiting residual viral replication, hence immune stimulation (22).

To conclude, while causality cannot be established in observational studies, our findings suggest an overall improvement in the immunologic profile of PWH who switch to LA CAB/RPV. This trend will necessitate a longer follow-up to be confirmed.

Beyond immunologic parameters, we observed modest but significant reductions in total and LDL cholesterol over time, even after excluding individuals who initiated or discontinued statin therapy. Although the magnitude of lipid changes was small (-1.72 mg/dL per year in total cholesterol and -4.40 mg/dL per year in LDL cholesterol), their persistence over multiple years may be clinically relevant, particularly in aging populations with increased cardiovascular risk.

These findings are consistent with prior clinical trial data and observational studies suggesting the metabolic safety of this regimen, with some phase 3/3b studies reporting improvements in lipid profiles. For instance, the SOLAR study demonstrated a slight decrease in total and LDL cholesterol in the LA CAB/RPV arm, whereas ATLAS-2M observed a modest increase in HDL cholesterol (5, 23). In contrast, the phase 3b CARES trial reported a slight worsening of the lipid profile in those switching to LA CAB/RPV, likely reflecting the discontinuation of tenofovir disoproxil fumarate (TDF) in many participants, a compound known to have lipid-lowering effects (24, 25). Similar to immunologic outcomes, real world data on metabolic outcomes of LA CAB/RPV remains limited. A recent retrospective Italian multicenter study observed a significant increase in HDL levels in PWH switching to CAB/RPV, significantly in the participants switching from a dolutegravir based regimen (26). Similarly, a Japanese multicenter retrospective study demonstrated a significant increase in serum HDL, while LDL and the total cholesterol/HDL ratio remained unchanged (21).

Furthermore, no significant changes in body weight or body mass index were detected during our follow-up. While weight gain has emerged as a concern with several contemporary ART regimens, particularly those containing integrase inhibitors in combination with TAF (9, 27, 28), our findings support the generally weight-neutral profile of LA CAB/RPV.

Renal parameters followed a favorable trajectory in our cohort, with a gradual increase in eGFR and a reduction in serum creatinine over time. These findings are consistent with the pharmacologic characteristics of LA CAB/RPV, which does not include agents commonly associated with renal toxicity or functional increases in serum creatinine, such as tenofovir disoproxil fumarate (TDF) or pharmacologic boosting (29, 30). Overall, our results are consistent with the renal safety profile of LA CAB/RPV observed in both clinical trials and real-world settings (21, 31).

Several strengths support the relevance of our findings. The prospective design, large sample size, and extended follow-up provide a robust real-world evaluation of 2-year-trends. The use of linear mixed-effects models allowed efficient use of repeated measurements and improved precision in estimating longitudinal changes.

However, our cohort was predominantly male and middle-aged, which may limit generalizability to women and older individuals with higher comorbidity burdens. The lack of a control group also limits the interpretability of the results.

In conclusion, in this large real-world cohort of virologically suppressed PWH, switching to LA CAB/RPV was associated with a progressive increase in the CD4/CD8 ratio over 24 months, primarily driven by a sustained decline in CD8 cell counts and consistent across prior ART backbones after adjustment. At the same time, we observed modest but persistent improvements in lipid parameters without significant weight gain, together with a favorable renal trajectory characterized by increasing eGFR and decreasing serum creatinine. Collectively, these findings support a stable or potentially advantageous immunologic, metabolic, and renal profile of LA CAB/RPV in routine clinical practice, warranting longer follow-up to determine whether these trends translate into clinically meaningful benefits.

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Footnotes

Edited by: Massimiliano Fabbiani, University of Siena, Italy

Reviewed by: Nicola Squillace, IRCCS San Gerardo dei Tintori Foundation, Italy

Alberto Borghetti, University of Pisa, Italy