Discovery of the Next Generation of Non-peptidomimetic Neurolysin Activators with High Blood-Brain Barrier Permeability: a Pharmacokinetics Study in Healthy and Stroke Animals

Imidazole Bioisostere Activators of Endopeptidase Neurolysin with Enhanced Potency and Metabolic Stability

The peptidase neurolysin (Nln) has been validated as a potential target for developing therapeutics for ischemic stroke (IS). Overexpression of Nln in a mouse model of IS provides significant cerebroprotection, leading to reduced infarction size and edema volume. Pharmacological inhibition of Nln in the post-stroke brain worsens neurological outcomes. A virtual screen identified dipeptide small-molecule activators of Nln. Optimization studies resulted in a class of peptidomimetic compounds with promising activity. However, these compounds still possessed an amide bond that compromised their stability in plasma and the brain. Herein, we report the synthesis and characterization of a series of amide bioisosteres based on our peptidomimetic leads. Imidazole-based bioisosteres afford scaffolds with increased potency to activate Nln combined with enhanced mouse plasma stability and significantly better brain permeability over the original dipeptide hits.

Systemic and Brain Pharmacokinetics of Milnacipran in Mice: Comparison of Intraperitoneal and Intravenous Administration

Milnacipran is a dual serotonin and norepinephrine reuptake inhibitor, clinically used for the treatment of major depression or fibromyalgia. Currently, there are no studies reporting the pharmacokinetics (PK) of milnacipran after intraperitoneal (IP) injection, despite this being the primary administration route in numerous experimental studies using the drug. Therefore, the present study was designed to investigate the PK profile of IP-administered milnacipran in mice and compare it to the intravenous (IV) route. First a liquid chromatography-mass spectrometry (LC-MS/MS) method was developed and validated to accurately quantify milnacipran in biological samples. The method was used to quantify milnacipran in blood and brain samples collected at various time-points post-administration. Non-compartmental and PK analyses were employed to determine key PK parameters. The maximum concentration (Cmax) of the drug in plasma was at 5 min after IP administration, whereas in the brain, it was at 60 min for both routes of administration. Curiously, the majority of PK parameters were similar irrespective of the administration route, and the bioavailability was 92.5% after the IP injection. These findings provide insight into milnacipran's absorption, distribution, and elimination characteristics in mice after IP administration for the first time and should be valuable for future pharmacological studies.