Nucleoside reverse transcriptase inhibitors induced hepatocellular mitochondrial DNA lesions and compensatory enhancement of mitochondrial function and DNA repair

Nucleoside reverse transcriptase inhibitors (NRTIs) are the backbone of combined antiretroviral therapy (cART) and are widely used in anti-human immunodeficiency virus (HIV) therapy. Long-term administration of NRTIs can result in mitochondrial dysfunction in certain HIV-1-infected patients. However, NRTI-associated liver mitochondrial toxicity is not well known. Herein, the liver autopsy of acquired immune deficiency syndrome (AIDS) patients and the liver tissues of mice with 12 months of NRTI exposure were used to identify NRTI-associated liver toxicity with immunofluorescence, quantitative real-time polymerase chain reaction (qPCR), Amplex red and horseradish peroxidase, and cloning and sequencing. Laser capture microdissection was used to capture hepatocytes from liver tissues. We observed DNA oxidative damage and mitochondrial DNA (mtDNA) loss in the livers of AIDS patients, and cART patients had higher DNA oxidative damage and lower DNA repair function in liver tissues than non-cART patients. We also observed liver oxidative damage, increased DNA repair and mtDNA loss in mice with exposure to four different NRTIs for 12 months, and hepatocytes had no more mtDNA loss than liver tissues. Although NRTIs could induce mitochondrial hydrogen peroxide production, increased mitochondrial oxygen consumption was found with a Clark-type electrode. The captured hepatocytes had greater diversity in their mtDNA D-loop, dehydrogenase subunit1 (ND1) and ND4 than the controls. Long-term NRTI exposure induced single nucleotide variation in hepatocellular mtDNA D-loop, ND1 and ND4. Our findings indicate that NRTIs can induce liver mtDNA lesions, but simultaneously enhance mitochondrial function and mtDNA repair.

Treatment-limiting renal tubulopathy in patients treated with tenofovir disoproxil fumarate

OBJECTIVES

Tenofovir disoproxil fumarate (TDF) is widely used in the treatment or prevention of HIV and hepatitis B infection. TDF may cause renal tubulopathy in a small proportion of recipients. We aimed to study the risk factors for developing severe renal tubulopathy.

METHODS

We conducted an observational cohort study with retrospective identification of cases of treatment-limiting tubulopathy during TDF exposure. We used multivariate Poisson regression analysis to identify risk factors for tubulopathy, and mixed effects models to analyse adjusted estimated glomerular filtration rate (eGFR) slopes.

RESULTS

Between October 2002 and June 2013, 60 (0.4%) of 15,983 patients who had received TDF developed tubulopathy after a median exposure of 44.1 (IQR 20.4, 64.4) months. Tubulopathy cases were predominantly male (92%), of white ethnicity (93%), and exposed to antiretroviral regimens that contained boosted protease inhibitors (PI, 90%). In multivariate analysis, age, ethnicity, CD4 cell count and use of didanosine or PI were significantly associated with tubulopathy. Tubulopathy cases experienced significantly greater eGFR decline while receiving TDF than the comparator group (-6.60 [-7.70, -5.50] vs. -0.34 [-0.43, -0.26] mL/min/1.73 m²/year, p < 0.0001).

CONCLUSIONS

Older age, white ethnicity, immunodeficiency and co-administration of ddI and PI were risk factors for tubulopathy in patients who received TDF-containing antiretroviral therapy. The presence of rapid eGFR decline identified TDF recipients at increased risk of tubulopathy.

In Vitro Activity of SPD754, a New Deoxycytidine Nucleoside Reverse Transcriptase Inhibitor (NRTI), against 215 HIV-1 Isolates Resistant to Other NRTIs

SPD754 (also known as AVX-754) is a deoxycytidine analogue nucleoside reverse transcriptase inhibitor (NRTI) with antiretroviral activity against HIV-1 and HIV-2 in vitro and against recombinant viruses containing thymidine analogue mutations (TAMs). In order to better establish the activity of SPD754 against HIV-1 containing TAMs, twelve panels of up to twenty clinical isolates with defined TAM combinations were selected from the ViroLogic database. Phenotypic viral susceptibility to SPD754 and five other NRTIs was tested using the PhenoSense HIV assay and expressed as median fold-change compared with a reference strain. In total, 215 isolates were selected, representing four TAM patterns in both pathways by which TAMs accumulate clinically. The presence of five TAMs in the 41, 215 pathway, at codons 41, 67, 210, 215, and 219 of reverse transcriptase (RT), produced a median 1.8-fold reduction in SPD754 susceptibility, compared with fold reductions to zidovudine, lamivudine, abacavir, didanosine and tenofovir of 438, 4.8, 4.5, 1.4 and 3.6, respectively. Five TAMs in the 67, 70, 219 pathway (at codons 41, 67, 70, 215 and 219) reduced SPD754 susceptibility by a median 1.3-fold, compared with fold reductions for the aforementioned NRTIs of 108, 3.2, 3.0, 1.3 and 2.5, respectively. M184V addition reduced SPD754 susceptibility by 1.8-fold in the presence or absence of TAMs. SPD754 retains a substantial proportion of its antiviral activity against HIV-1 containing multiple TAMs, with or without the M184V mutation. These data suggest that SPD754 is a promising new NRTI for the treatment of NRTI-experienced HIV-infected patients.

Challenges for the Clinical Development of New Nucleoside Reverse Transcriptase Inhibitors for HIV Infection

There is a need for new antiretroviral drugs with activity against HIV isolates resistant to currently available agents and improved short and long-term tolerability profiles. Clinical trial designs for nucleotide and nucleoside reverse transcriptase inhibitors (NRTIs) are restricted by the characteristics of these agents (for example, their cross-resistance, resistance threshold and interaction profiles), the ethical need to ensure that patients are not maintained on suboptimal regimens, and regulatory requirements (for example, with regards to trial designs and patient populations). For example, consideration of cross-resistance profiles must influence the way in which an NRTI in development is sequenced to minimize any impact on future treatment options. The resistance threshold is determined by the number of mutations required to diminish sensitivity to a given drug. Pharmacokinetic or pharmacodynamic interactions restrict how NRTIs may be combined during clinical development. Doses may be selected on the basis of results from short-term monotherapy studies in treatment-naive patients, but such studies cannot establish the long-term efficacy or tolerability of new agents used in combination regimens. Confirmatory studies in treatment-naive populations do not meet the medical and regulatory needs for clinical data in treatment-experienced populations, while studies in treatment-experienced populations are subject to numerous clinical and logistical difficulties. Intensification, switch and hybrid study designs all offer suitable approaches to the evaluation of NRTIs with novel resistance profiles. Switch studies are particularly useful for agents with resistance profiles that suggest a specific sequencing approach in treatment and for those with the potential, based on pharmacokinetic data, for interactions with other agents. The successful development of new NRTIs will depend upon a thorough appreciation of these many and complex issues, not only among those involved in the design of clinical studies, but also those contributing to their review and conduct.

Nucleoside and Nucleotide Analogue Reverse Transcriptase Inhibitors: A Clinical Review of Antiretroviral Resistance

Although advances in highly active antiretroviral therapy (HAART) have made long-term suppression of HIV an achievable goal of therapy, a substantial proportion of first-line regimens will eventually fail. Successful long-term treatment requires consideration of downstream treatment options at the time of initiating or changing regimens. An understanding of the patterns and interactions of resistance mutations, and the appropriate use of genotypic and phenotypic testing is an important component of successful drug sequencing. Resistance to multiple nucleoside reverse transcriptase inhibitors (NRTIs) may result from several genotypically distinct pathways, including the Q151M (151 complex), the 69 insertion complex, two distinct thymidine analogue mutational pathways and the K65R mutation. Knowledge of the clinical implications of these and other resistance pathways, as well as the antagonism or synergy between mutations, helps guide individualized treatment choices from initial therapy in the treatment-naive patient to salvage therapy in the highly treatment-experienced individual. The development of effective sequencing strategies will depend upon the continued understanding of drug resistance mutation patterns and their associations with specific HAART combinations. This review summarizes research advances that further the understanding of nucleoside and nucleotide analogue resistance mutations, and their interplay.