Tacrolimus, Sirolimus and Everolimus Doses in HIV-Infected Solid-Organ Recipients, Requiring a Cobicistat-Based Antiretroviral Regimen: Report of Three Cases and Review

Switch from a ritonavir to a cobicistat containing antiretroviral regimen and impact on tacrolimus levels in a kidney transplant recipient

BACKGROUND

Solid-organ transplantation due to end-stage organ disease is increasingly performed in people living with HIV. Despite improved transplant outcomes, management of these patients remains challenging due to higher risk for allograft rejection, infection and drug-drug interactions (DDIs). Complex regimens for multi-drug resistant HIV-viruses may cause DDIs particularly if the regimen contains drugs such as ritonavir or cobicistat.

CASE PRESENTATION

Here we report on a case of an HIV-infected renal transplant recipient on long-term immunosuppressive therapy with mycophenolate mofetil and tacrolimus dosed at 0.5 mg every 11 days due to the co-administration of a darunavir/ritonavir containing antiretroviral regimen. In the presented case the pharmacokinetic booster was switched from ritonavir to cobicistat for treatment simplification. A close monitoring of tacrolimus drug levels was performed in order to prevent possible sub- or supratherapeutic tacrolimus trough levels. A progressive decrease in tacrolimus concentrations was observed after switch requiring shortening of tacrolimus dosing interval. This observation was unexpected considering that cobicistat is devoid of inducing properties.

CONCLUSIONS

This case highlights the fact that the pharmacokinetic boosters ritonavir and cobicistat are not fully interchangeable. Therapeutic drug monitoring of tacrolimus is warranted to maintain levels within the therapeutic range.

HIV-1 replication and latency are balanced by mTOR-driven cell metabolism

Human Immunodeficiency virus type 1 (HIV-1) relies on host cell metabolism for all aspects of viral replication. Efficient HIV-1 entry, reverse transcription, and integration occurs in activated T cells because HIV-1 proteins co-opt host metabolic pathways to fuel the anabolic requirements of virion production. The HIV-1 viral life cycle is especially dependent on mTOR, which drives signaling and metabolic pathways required for viral entry, replication, and latency. As a central regulator of host cell metabolism, mTOR and its downstream effectors help to regulate the expression of enzymes within the glycolytic and pentose phosphate pathways along with other metabolic pathways regulating amino acid uptake, lipid metabolism, and autophagy. In HIV-1 pathogenesis, mTOR, in addition to HIF-1α and Myc signaling pathways, alter host cell metabolism to create an optimal environment for viral replication. Increased glycolysis and pentose phosphate pathway activity are required in the early stages of the viral life cycle, such as providing sufficient dNTPs for reverse transcription. In later stages, fatty acid synthesis is required for creating cholesterol and membrane lipids required for viral budding. Epigenetics of the provirus fueled by metabolism and mTOR signaling likewise controls active and latent infection. Acetyl-CoA and methyl group abundance, supplied by the TCA cycle and amino acid uptake respectively, may regulate latent infection and reactivation. Thus, understanding and exploring new connections between cellular metabolism and HIV-1 pathogenesis may yield new insights into the latent viral reservoirs and fuel novel treatments and cure strategies.

The intersection of drug interactions and adverse reactions in contemporary antiretroviral therapy

PURPOSE OF REVIEW

Advances in antiretroviral therapy (ART) have transformed HIV infection into a chronic and manageable condition. The introduction of potent and more tolerable antiretrovirals (ARVs) with favorable pharmacokinetic profiles has changed the prevalence and nature of drug-drug interactions (DDIs). Here, we review the relevance of DDIs in the era of contemporary ART.

RECENT FINDINGS

Management of DDIs remains an important challenge with modern ART, primarily due to increased polypharmacy in older persons living with HIV. Significant DDIs exist between boosted ARVs or older nonnucleoside reverse transcriptase inhibitors and comedications for chronic comorbidities (e.g., anticoagulants, antiplatelets, statins) or complex conditions (e.g., anticancer agents, immunosuppressants). Newer ARVs such as unboosted integrase inhibitors, doravirine, and fostemsavir have reduced DDI potential, but there are clinically relevant DDIs that warrant consideration. Potential consequences of DDIs include increased toxicity and/or reduced efficacy of ARVs and/or comedications. Management approaches include switching to an ARV with less DDI potential, changing comedications, or altering medication dosage or dosing frequency. Deprescribing strategies can reduce DDIs and polypharmacy, improve adherence, minimize unnecessary adverse effects, and prevent medication-related errors.

SUMMARY

Management of DDIs requires close interdisciplinary collaboration from multiple healthcare disciplines (medicine, nursing, pharmacy) across a spectrum of care (community, outpatient, inpatient).