Novel Drp1 GTPase Inhibitor, Drpitor1a: Efficacy in Pulmonary Hypertension.

BACKGROUND: Drp1 (dynamin-related protein 1), a large GTPase, mediates the increased mitochondrial fission, which contributes to hyperproliferation of pulmonary artery smooth muscle cells in pulmonary arterial hypertension (PAH). We developed a potent Drp1 GTPase inhibitor, Drpitor1a, but its specificity, pharmacokinetics, and efficacy in PAH are unknown. METHODS: Drpitor1a's ability to inhibit recombinant and endogenous Drp1 GTPase was assessed. Drpitor1a's effects on fission were studied in control and PAH human pulmonary artery smooth muscle cells (hPASMC) and blood outgrowth endothelial cells (BOEC). Cell proliferation and apoptosis were studied in hPASMC. Pharmacokinetics and tissue concentrations were measured following intravenous and oral drug administration. Drpitor1a's efficacy in regressing monocrotaline-PAH was assessed in rats. In a pilot study, Drpitor1a reduced PA remodeling only in females. Subsequently, we compared Drpitor1a to vehicles in control and monocrotaline-PAH females. RESULTS: Drp1 GTPase activity was increased in PAH hPASMC. Drpitor1a inhibited the GTPase activity of recombinant and endogenous Drp1 and reversed the increased fission, seen in PAH hPASMC and PAH BOEC. Drpitor1a inhibited proliferation and induced apoptosis in PAH hPASMC without affecting electron transport chain activity, respiration, fission/fusion mediator expression, or mitochondrial Drp1 translocation. Drpitor1a did not inhibit proliferation or alter mitochondrial dynamics in normal hPASMC. Drpitor1a regressed monocrotaline-PAH without systemic vascular effects or toxicity. CONCLUSIONS: Drpitor1a is a specific Drp1 GTPase inhibitor that reduces mitochondrial fission in PAH hPASMC and PAH BOEC. Drpitor1a reduces proliferation and induces apoptosis in PAH hPASMC and regresses monocrotaline-PAH. Drp1 is a therapeutic target in PAH, and Drpitor1a is a potential therapy with an interesting therapeutic sexual dimorphism.

Efficacy of Drpitor1a, a Dynamin-Related Protein 1 inhibitor, in Pulmonary Arterial Hypertension.

Rationale: Dynamin-related protein 1 (Drp1), a large GTPase, mediates mitochondrial fission. Increased Drp1-mediated fission permits accelerated mitosis, contributing to hyperproliferation of pulmonary artery smooth muscle cells (PASMC), which characterizes pulmonary arterial hypertension (PAH). We developed a Drp1 inhibitor, Drpitor1a, and tested its ability to regress PAH. Objectives: Assess Drpitor1a's efficacy and toxicity in: a)normal and PAH human PASMC (hPASMC); b)normal rats versus rats with established monocrotaline (MCT)-induced PAH. Methods: Drpitor1a's effects on recombinant and endogenous Drp1-GTPase activity, mitochondrial fission, and cell proliferation were studied in hPASMCs (normal=3; PAH=5). Drpitor1a's pharmacokinetics and tissue concentrations were measured (n=3 rats/sex). In a pilot study (n=3-4/sex/dose), Drpitor1a (1mg/kg/48-hours, intravenous) reduced adverse PA remodeling only in females. Consequently, we compared Drpitor1a to vehicle in normal (n=6 versus 8) and MCT-PAH (n=9 and 11) females, respectively. Drpitor1a treatment began 17-days post-MCT with echocardiography and cardiac catheterization performed 28-29 days post-MCT. Results: Drpitor1a inhibited recombinant and endogenous Drp1 GTPase activity, which was increased in PAH hPASMC. Drpitor1a inhibited mitochondrial fission and proliferation and induced apoptosis, in PAH hPASMC but not normal hPASMC. Drpitor1a tissue levels were higher in female versus male RVs. In MCT-PAH females, Drpitor1a regressed PA obstruction, lowered pulmonary vascular resistance, and improved RV function, without hematologic, renal, or hepatic toxicity. Conclusions: Drpitor1a inhibits Drp1 GTPase, reduces mitochondrial fission, and inhibits cell proliferation in PAH hPASMC. Drpitor1a caused no toxicity in MCT-PAH and had no significant effect on normal rats or hPASMCs. Drpitor1a is a potential PAH therapeutic which displays an interesting therapeutic sexual dimorphism.

Deuterated Drugs and Biomarkers in the COVID-19 Pandemic.

Coronavirus disease 2019 (COVID-19) is a highly contagious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Initially identified in Wuhan (China) in December 2019, COVID-19 rapidly spread globally, resulting in the COVID-19 pandemic. Carriers of the SARS-CoV-2 can experience symptoms ranging from mild to severe (or no symptoms whatsoever). Although vaccination provides extra immunity toward SARS-CoV-2, there has been an urgent need to develop treatments for COVID-19 to alleviate symptoms for carriers of the disease. In seeking a potential treatment, deuterated compounds have played a critical role either as therapeutic agents or as internal MS standards for studying the pharmacological properties of new drugs by quantifying the parent compounds and metabolites. We have identified >70 examples of deuterium-labeled compounds associated with treatment of COVID-19. Of these, we found 9 repurposed drugs and >20 novel drugs studied for potential therapeutic roles along with a total of 38 compounds (drugs, biomarkers, and lipids) explored as internal mass spectrometry standards. This review details the synthetic pathways and modes of action of these compounds (if known), and a brief analysis of each study.