Pharmacokinetics and tolerability of cabotegravir and rilpivirine long-acting intramuscular injections to the vastus lateralis (lateral thigh) muscles of healthy adult participants

Safety and efficacy of long-acting cabotegravir/rilpivirine versus standard oral antiretroviral therapy: a systematic review and meta-analysis

BACKGROUND

In 2023, there were 39.9 million people living with HIV (PLWH) worldwide and 630 000 deaths related to HIV. New strategies are needed, and long-acting antiretrovirals (LAAs) are now widely considered to have great potential to help end the HIV epidemic. This systematic review and meta-analysis compare the safety and efficacy of LAA versus standard oral treatment (SOT) for HIV.

METHODS

PubMed and Embase databases, supplemented by ClinicalTrials.gov and grey literature, were searched. Randomized controlled trials (RCTs) reporting efficacy and/or safety of LAA versus SOT for PLWH until June 2024 were included. Efficacy (HIV RNA < 50 copies/mL) and HIV RNA ≥ 50 copies/mL, adverse events (AEs), treatment discontinuation, CD4 count, metabolic parameters and drug resistance were assessed. Prespecified subgroup analyses were conducted. The risk of bias was assessed with Cochrane RoB 2.0. Certainty of evidence was assessed using GRADE.

RESULTS

Six RCTs were eligible for inclusion, involving 2829 participants. LAA was non-inferior to SOT in suppressing HIV RNA < 50 copies/mL [Risk Difference (RD), -0.00; 95% CI, -0.03-0.02; P = 0.83; I2 = 51%; high quality of evidence (QoE)]. LAA was associated with higher drug resistance (percentage pooled estimate, 57%; 95% CI, 33%-78% versus 9%; 95% CI, 2%-30%; moderate QoE) and risk of grade 1-4 AEs than SOT [Risk Ratio (RR), 1.22; 95% CI, 1.12-1.33; P < 0.001; I2 = 62%; moderate QoE].

CONCLUSIONS

LAA has non-inferior efficacy compared to SOT. However, participants receiving LAA were at a higher risk of developing drug resistance, cross-resistance and AEs.

Thigh Injections of Cabotegravir + Rilpivirine in Virally Suppressed Adults With Human Immunodeficiency Virus Type 1: A Substudy of the Phase 3b ATLAS-2M Study

BACKGROUND

Cabotegravir + rilpivirine (CAB + RPV) administered via intramuscular gluteal injections is the first complete long-acting regimen for maintaining human immunodeficiency virus type 1 (HIV-1) virologic suppression. We present substudy results on short-term repeat intramuscular CAB + RPV long-acting thigh injections in participants with ≥3 years of experience with gluteal administration during the ATLAS-2M study.

METHODS

Substudy phases included screening, thigh injection (day 1-week 16), and return to gluteal injection (week 16-week 24). The injection schedule was unchanged from the main study. Outcomes included pharmacokinetics, safety, tolerability, efficacy, and patient-reported outcomes. Pharmacokinetic parameters were determined using noncompartmental analysis and mixed-effects modeling. Population pharmacokinetic simulations were performed.

RESULTS

There were 118 participants. In the arm that received injections every 2 months (Q2M), first CAB thigh injection including area under the concentration-time curve and maximum observed concentration (Cmax) and first RPV thigh injection Cmax and all last RPV thigh injection parameters were statistically higher vs gluteal injections (paired comparison). No significant differences occurred with once-monthly (QM) dosing. No participants had HIV-1 RNA ≥50 copies/mL after thigh injections. Overall, 4%-7% of injection site reactions (ISRs) were grade 3. Five participants withdrew due to an ISR or injection intolerability. Overall, 30% preferred thigh vs gluteal injections. Simulations demonstrated the potential for chronic/continuous QM or ≤2 consecutive Q2M thigh injections.

CONCLUSIONS

These data demonstrate the potential use of chronic/continuous QM and rotational/short-term QM or Q2M (≤4 months of continuous dosing), CAB + RPV long-acting intramuscular thigh administration for HIV-1 treatment.

Population pharmacokinetics of cabotegravir following intramuscular thigh injections in adults with and without HIV

Cabotegravir intramuscular gluteal injection is approved for HIV treatment (with rilpivirine) and prevention. Thigh muscle is a potential alternative injection site. We aim to characterize cabotegravir pharmacokinetics and its association with demographics following intramuscular thigh injection in comparison with gluteal injection using population pharmacokinetic (PPK) analysis. Fourteen HIV-negative participants received 600 mg single thigh injection in phase 1 study 208832 and 118 participants with HIV received thigh injections 400 mg monthly 4× or 600 mg once-every-2-months 2× after ≥3 years of gluteal injections in phase 3b study ATLAS-2M provided 1,249 cabotegravir concentrations from 366 thigh injections and 1,998 concentrations from 1,618 gluteal injections. The established gluteal PPK model was modified by adding thigh injection compartment and fit to pharmacokinetic data following both gluteal and thigh injections, enabling within-person comparison in ATLAS-2M. Gluteal parameters were fixed. Similar to the gluteal absorption rate constant (KAgluteal), the thigh absorption rate constant (KAthigh) was slower in females than males and in participants with higher BMI. KAthigh was strongly correlated with KAgluteal (correlation coefficient 0.766), best described by the additive linear relationship KAthigh = KAgluteal + 0.0002527 h-1. Terminal half-life of thigh injection was 26% (male) and 39% (female) shorter than gluteal injection. Relative bioavailability of thigh to gluteal was estimated to be 89.9%. The impact of covariates on cabotegravir exposure following thigh injections was ≤35%. In conclusion, cabotegravir absorption following thigh injection was correlated with, faster than, and 10% less bioavailable than gluteal injection, and correlated with sex and BMI. The cabotegravir thigh PPK model can inform dosing strategies and future study design.

Real-world data on long-acting intramuscular maintenance therapy with cabotegravir and rilpivirine mirror Phase 3 results

INTRODUCTION

Cabotegravir, an integrase strand transfer inhibitor, and rilpivirine, an NNRTI, constitute the first long-acting (LA), injectable, two-drug ART regimen approved for the maintenance of virological suppression in persons living with HIV-1 (PLHIV). The aim of this study was to assess clinical effectiveness and tolerability of LA cabotegravir/rilpivirine in a real-world setting.

PATIENTS AND METHODS

We conducted a retrospective, single centre study, including all PLHIV receiving LA cabotegravir/rilpivirine as standard-of-care in our tertiary centre even if initiated in clinical trials.

RESULTS

Between 2014 and 2022, 126 PLHIV initiated LA cabotegravir/rilpivirine. All were ART-experienced, and 98.4% had a viral load (VL) of <50 copies/mL before LA cabotegravir/rilpivirine initiation. Median BMI at cabotegravir/rilpivirine initiation was 24 IQR (23-28). During a median follow-up of 9 months IQR (7-24), 27 patients discontinued cabotegravir/rilpivirine: 5 because of virological failure, 6 for adverse events, 11 for personal reasons unrelated to treatment tolerance and 5 for other reasons. Virological failure was not associated with a higher BMI, nor with weight gain during LA intramuscular (IM) cabotegravir/rilpivirine treatment, inadequate cabotegravir and rilpivirine concentrations, VL blips or the use of oral lead-in (OLI) or not. No drug resistance-associated mutation emerged. Adverse events leading to treatment interruption were injection-site pain (n = 3) and neuropsychological side effects (n = 3). A correlation between BMI and both cabotegravir and rilpivirine concentrations at 1 month post-initiation of LA-IM cabotegravir/rilpivirine was observed, with no impact of OLI.

CONCLUSIONS

Data from this real-world cohort of PLHIV who received cabotegravir/rilpivirine LA injections suggest that this regimen is effective and well tolerated. Virological failures were not associated with the acquisition of resistance mutations.

Population Pharmacokinetics of Cabotegravir Following Oral Administration and Long-Acting Intramuscular Injection in Real-World People with HIV

Long-acting cabotegravir has been studied mainly in the stringent framework of clinical trials, which does not necessarily reflect the situation of people with HIV (PWH) in routine clinical settings. The present population pharmacokinetic analysis aims to build real-world reference percentile curves of cabotegravir concentrations, accounting for patient-related factors that may affect cabotegravir exposure. The second objective is to simulate whether dosing interval adjustments of cabotegravir could be considered in specific subpopulations. Overall, 238 PWH contributed to 1,038 cabotegravir levels (186 during the initial oral administration phase and 852 after intramuscular injection). Cabotegravir pharmacokinetics was best described using a one-compartment model with distinct first order-absorption for oral and intramuscular administrations, and identical volume and clearance. Our model showed almost 40% faster absorption and 30% higher clearance than previously reported, resulting in a time to steady-state of 8 months and an elimination half-life of 4.6 weeks for long-acting cabotegravir. Sex and body mass index significantly influenced absorption, and bodyweight affected clearance. Model-based simulations showed that cabotegravir trough concentrations in females were 25% lower 4 weeks after the intramuscular loading dose, but 42% higher during the late maintenance phase. Finally, simulations indicated that in females, despite significantly higher cabotegravir concentrations, longer intervals between injections may not consistently ensure levels above the 4-fold protein-adjusted 90% inhibitory target concentration.

Long-acting prescriptions and therapy for HIV-1 from market launch to the present in Germany (May 2021 to December 2023)

Background

In Europe, the combination of cabotegravir (CAB) with rilpivirine (RPV) has been approved as a dual injection long-acting (LA) therapy for the treatment of human immunodeficiency virus type 1 (HIV-1) infections in adults since December 2020. Studies have shown that between 36 and 61% of people living with HIV (PLWHIV) prefer LA therapy. However, there are no real-world data on the number of people receiving LA therapy, in Germany or internationally. The aim of this study was to assess the current situation and trends in usage of LA therapy for the treatment of HIV-1 in Germany.

Methods

Based on pharmacy prescription data derived from Insight Health, the monthly number of prescriptions for oral CAB, CAB-LA, and RPV-LA over the entire period of availability in Germany was analyzed and evaluated (May 2021 to December 2023). The number of 1st and 2nd initiation injections and subsequent maintenance injections was calculated on the basis of the prescriptions for oral CAB initiation.

Results

The bimonthly schedule resulted in two growing cohorts from September 2021 with an estimated 14,523 CAB-LA prescriptions over the entire period. Accordingly, in December 2023, there were approximately 1,364 PLWHIV receiving LA therapy, of whom 1,318 were receiving maintenance therapy. Only treatments with bimonthly regimens were carried out. Accounting for people not covered by statutory health insurance (~13%), a total of ~1,600 PLWHIV were receiving LA therapy in Germany in December 2023. The average rounded annual cost of therapy in 2023 was €11,940 (maintenance therapy with initiation) and €10,950 (maintenance therapy without initiation).

Conclusion

To our knowledge, this is the first study of real-world use and number of people receiving LA therapy. A strength of our study is the nearly complete coverage of people with statutory health insurance in Germany. The predicted demand for LA therapy does not match the actual number of people receiving LA therapy. Although the number of PLWHIV receiving LA therapy increased steadily, they accounted for just under 2% of the estimated total number of people receiving HIV therapy in Germany in 2023, almost 2 years after the market launch. No significant increase in prescriptions is expected; on the contrary, the trend is leveling off and is unlikely to change drastically in the near future. Hence, the need for this mode of therapy in Germany appears to be limited. Follow-up studies at regular intervals on the further course would be useful and are recommended, as well as investigations into the possible reasons for the slow uptake to inform public health experts and possibly broaden treatment options.