Low-level of mitochondrial DNA alterations during direct-acting antiviral treatment in leukocytes of people who inject drugs living with HCV

Direct-acting antivirals (DAAs) have revolutionized hepatitis C virus (HCV) treatment, offering high cure rates and favorable safety profiles. However, concerns remain regarding their long-term mitochondrial safety, particularly among vulnerable populations such as people who inject drugs (PWID), who are frequently exposed to multiple mitotoxic agents. This longitudinal study investigated mitochondrial DNA (mtDNA) instability, including deletions and single-nucleotide variants, among PWID living with HCV during DAA treatment, using whole mitochondrial genome sequencing. We analyzed samples of 33 PWID living with HCV before treatment (baseline), at the end of treatment (week 12), and after long-term follow-up (week 48), in comparison with 30 HCV-seronegative PWID. Associations with clinical events were assessed during a 3-year follow-up after study completion. mtDNA deletions were detected in 9.1% of PWID living with HCV at baseline and increased to 19.2% post-treatment, whereas no mtDNA deletions were observed in HCV-seronegative PWID. Heteroplasmy levels (i.e., proportion of mutated to wild-type mtDNA) remained below 1%. Variants were widespread in both HCV-positive and HCV-seronegative PWID, predominantly in the non-coding D-loop region. A small number of low-heteroplasmy treatment-emergent variants were detected during follow-up, but none persisted at long-term follow-up. No significant associations were found between mtDNA instability and hepatic or splenic complications assessed at 3 years. These findings suggest that DAA exposure is associated with low-level mtDNA instability in blood leukocytes. Nonetheless, long-term mitochondrial surveillance is warranted, especially in post-mitotic tissues, to fully assess the implications of cumulative mitotoxic exposures in this high-risk population. IMPORTANCE: Direct-acting antivirals (DAAs) have revolutionized hepatitis C virus (HCV) treatment, but their safety is still under debate. Given the nature of these regimens, mitochondrial genotoxicity could represent a potential off-target effect. We searched for mitochondrial DNA alterations in people who inject drugs living with HCV. The prevalence of HCV infection is high in this population, and any potential toxicity would be exacerbated as they are exposed to other mitotoxic drugs. We detected low-level mitochondrial DNA alterations in blood leukocytes, including a modest increase in mitochondrial DNA deletions, but these alterations remained at very low levels (below 1%) and were not associated with any clinical complications during 3 years of follow-up. These findings provide reassuring evidence regarding the short-term mitochondrial safety of DAA treatment in blood leukocytes while supporting the need for longer-term studies in post-mitotic tissues. CLINICAL TRIALS: This study is registered with Clinical Trial Registry as NCT03526939 and NCT03537196.