Cell-free miRNAs are pharmacodynamic biomarkers for enhanced DICER activity by enoxacin in human patients with ALS

The activity of the RNase III enzyme DICER is downregulated in both sporadic and genetic forms of amyotrophic lateral sclerosis (ALS). Accordingly, hundreds of microRNAs (miRNAs) are broadly downregulated, leading to de-repression of their mRNA targets. Enoxacin is a fluoroquinolone that enhances DICER activity and miRNA biogenesis. Here, we tested for the first time the molecular effect of enoxacin on miRNA biogenesis in ALS patients and demonstrated that enoxacin's engagement with DICER can be pharmacodynamically monitored via miRNA levels in human subjects. In an investigator-initiated, first-in-human study (REALS1), we explored miRNAs as pharmacodynamic biomarkers of DICER activation. Patients with sporadic ALS received oral enoxacin twice daily for 30 days in a double-blind, randomized clinical trial. The study demonstrated comparable enoxacin levels in plasma and cerebrospinal fluid (CSF). Furthermore, an increase in cell-free miRNA levels in both plasma and CSF at all time points following enoxacin treatment (400 or 800 mg/day), was measured relative to baseline. Additionally, no serious adverse events were reported. In conclusion, pharmacological enhancement of DICER activity by enoxacin increases miRNA biogenesis in patients with ALS. These results support further investigation of enoxacin efficacy in larger clinical trials.