Transporter modulation of molnupiravir and its metabolite ß-D-N4-hydroxycytidine across the blood-brain barrier in a rat.

BACKGROUND: The antiviral drug molnupiravir is an orally bioavailable prodrug of the nucleoside analog ß-D-N4-hydroxycytidine (NHC), which is used to treat coronavirus disease 2019 (COVID-19). However, there is very little information on the barrier distribution of molnupiravir. Our hypothesis is that molnupiravir and NHC can penetrate the blood‒brain barrier (BBB) into brain tissue and that nucleoside transporters (equilibrative nucleoside transporters; ENT and concentrative nucleoside transporters; CNT) can modulate this process. METHODS: To investigate the mechanism of molnupiravir transport through the BBB, multiple microdialyses coupled to a validated ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC‒MS/MS) was developed to monitor dialysates, and nitrobenzylthioinosine (NBMPR; an inhibitor of ENT) was administered concomitantly with molnupiravir (100 mg/kg, i.v.) in the male rat. RESULTS: Here, we show that molnupiravir is rapidly metabolized to NHC in the blood and crossed the BBB in 20 min. Furthermore, when NBMPR is concomitantly administered to inhibit efflux, the concentrations of molnupiravir and NHC in the brain increased significantly. CONCLUSIONS: In summary, molnupiravir rapidly transforms into NHC and crosses the BBB and reaches the brain at approximately 0.3-0.8% of the blood‒brain ratio. The maximum concentration of NHC in the blood and brain is above the average half maximal inhibitory concentration (IC50) of the drug required to treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, suggesting a therapeutic effect. The penetration of NHC is modulated by NBMPR. These findings provide constructive information on brain disorders in clinical patients with COVID-19.

Due to the global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome (SARS-CoV-2), molnupiravir is used orally to treat COVID-19 with emergency use authorization. However, it is not well understood whether molnupiravir and its active component can cross the blood­brain barrier. The aim of the study was to develop an experimental mouse model to monitor the journey of molnupiravir and its active component through the bloodstream and eventually into the brain. Our experimental data suggest that a therapeutically useful amount of molnupiravir crosses from the bloodstream into the brain.

Transfer and biotransformation of the COVID-19 prodrug molnupiravir and its metabolite ß-D-N4-hydroxycytidine across the blood-placenta barrier.

BACKGROUND: Molnupiravir is an orally bioavailable prodrug of the nucleoside analogue ß-D-N4-hydroxycytidine (NHC) and is used to treat coronavirus disease 2019 (COVID-19). However, the pharmacokinetics and transplacental transfer of molnupiravir in pregnant women are still not well understood. In the present study, we investigated the hypothesis that molnupiravir and NHC cross the blood-placenta barrier into the fetus. METHODS: A multisite microdialysis coupled with a validated ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC‒MS/MS) system was developed to monitor the dialysate levels of molnupiravir and NHC in maternal rat blood and conceptus (the collective term for the fetus, placenta, and amniotic fluid). Molnupiravir was administered intravenously (100 mg/kg, i.v.) on gestational day 16. To investigate the mechanism of transport of molnupiravir across the blood-placenta barrier, we coadministered nitrobenzylthioinosine (NBMPR, 10 mg/kg, i.v.) to inhibit equilibrative nucleoside transporter (ENT). FINDINGS: We report that molnupiravir is rapidly metabolized to NHC and then rapidly transformed in the fetus, placenta, amniotic fluid, and maternal blood. Our pharmacokinetics analysis revealed that the area under the concentration curve (AUC) for the mother-to-fetus ratio (AUCfetus/AUCblood) of NHC was 0.29 ± 0.11. Further, we demonstrated that the transport of NHC in the placenta may not be subject to modulation by the ENT. INTERPRETATION: Our results show that NHC is the predominant bioactive metabolite of molnupiravir and rapidly crosses the blood-placenta barrier in pregnant rats. The NHC concentration in maternal blood and conceptus was above the average median inhibitory concentration (IC50) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), suggesting a therapeutic effect. These findings support the use of molnupiravir in pregnant patients infected with COVID. FUNDING: This study was supported in part by research grants from the National Science and Technology Council of Taiwan (NSTC 111-2113-M-A49-018 and NSTC 112-2321-B-A49-005).

Biotransformation and brain distribution of the anti-COVID-19 drug molnupiravir and herb-drug pharmacokinetic interactions between the herbal extract Scutellaria formula-NRICM101.

The aim of this study was to explore the effects of herbal drug pharmacokinetic interactions on the biotransformation of molnupiravir and its metabolite ß-D-N4-hydroxycytidine (NHC) in the blood and brain. To investigate the biotransformation mechanism, a carboxylesterase inhibitor, bis(4-nitrophenyl)phosphate (BNPP), was administered. Not only molnupiravir but also the herbal medicine Scutellaria formula-NRICM101 is potentially affected by coadministration with molnupiravir. However, the herb-drug interaction between molnupiravir and the Scutellaria formula-NRICM101 has not yet been investigated. We hypothesized that the complex bioactive herbal ingredients in the extract of the Scutellaria formula-NRICM101, the biotransformation and penetration of the bloodbrain barrier of molnupiravir are altered by inhibition of carboxylesterase. To monitor the analytes, ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLCMS/MS) coupled with the microdialysis method was developed. Based on the dose transfer from humans to rats, a dose of molnupiravir (100 mg/kg, i.v.), molnupiravir (100 mg/kg, i.v.) + BNPP (50 mg/kg, i.v.), and molnupiravir (100 mg/kg, i.v.) + the Scutellaria formula-NRICM101 extract (1.27 g/kg, per day, for 5 consecutive days) were administered. The results showed that molnupiravir was rapidly metabolized to NHC and penetrated into the brain striatum. However, when concomitant with BNPP, NHC was suppressed, and molnupiravir was enhanced. The blood-to-brain penetration ratios were 2% and 6%, respectively. In summary, the extract of the Scutellaria formula-NRICM101 provides a pharmacological effect similar to that of the carboxylesterase inhibitor to suppress NHC in the blood, and the brain penetration ratio was increased, but the concentration is also higher than the effective concentration in the blood and brain.

Preclinical Pharmacokinetics and Pharmacodynamics of Coptidis Preparation in Combination with Lovastatin in High-Fat Diet-Induced Hyperlipidemic Rats.

Lovastatin is a standard therapy for dyslipidemia. Alternatively, some ethnomedicines, such as Coptidis preparation, have been used for the treatment of dyslipidemia. Statins and complementary and alternative medicines may possess individual mechanisms of action against dyslipidemia. We hypothesize that the combination of Coptidis preparation and lovastatin may have synergistic effects for the treatment of dyslipidemia. To investigate this hypothesis, we developed a validated ultra-high-performance liquid chromatography-tandem mass spectrometry method to monitor lovastatin and its metabolites for pharmacokinetic studies in rats. This study was divided into four groups: lovastatin (10 mg/kg, p.o.) alone and lovastatin (10 mg/kg, p.o.) + Coptidis preparation (0.3, 1, or 3 g/kg, p.o.) for five consecutive days. In pharmacodynamic studies, a high-fat diet (HFD) was used to induce dyslipidemia in experimental rat models. The HFD rats were divided into four groups: treatment with HFD, HFD + lovastatin (100 mg/kg, p.o.), HFD + Coptidis preparation (1 g/kg, p.o.), and HFD + lovastatin (50 mg/kg, p.o.) + Coptidis preparation (1 g/kg, p.o.) for 28 consecutive days. The pharmacokinetic results demonstrated that Coptidis preparation significantly augmented the conversion of lovastatin into its main metabolite lovastatin acid in vivo. The pharmacodynamic results revealed that the Coptidis preparation and half-dose lovastatin group reduced the body weight, liver weight, and visceral fat in HFD rats. These findings provide constructive preclinical pharmacokinetic and pharmacodynamic applications of Coptidis preparation on the benefit of hyperlipidemia.

Protein unbound pharmacokinetics of ambroxol in the blood and brains of rats and the interaction of ambroxol with Polygala tenuifolia by multiple microdialysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Ambroxol elevates glucocerebrosidase (GCase) activity and reduces nigrostriatal alpha-synuclein burden to better ameliorate motor function in Parkinson's disease (PD). Polygala tenuifolia is a potential alternative botanical medicine for the treatment of many nonmotor symptoms of PD commonly used in Taiwanese patients. Co-administration of these two medicines pose potential herb-drug interaction. AIM OF THE STUDY: Our hypothesis is that ambroxol and P. tenuifolia may potentially possess herbal drug synergetic effects in the blood and brain. MATERIALS AND METHODS: To investigate this hypothesis, a multiple microdialysis system coupled with validated ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for rat blood and brain samples. Experimental rats were divided into three groups: low-dose and high-dose ambroxol alone (10 mg/kg, i.v. and 30 mg/kg, i.v., respectively) and ambroxol (10 mg/kg, i.v.) pretreated with P. tenuifolia extract (1 g/kg, p.o. for 5 consecutive days). RESULTS: Ambroxol easily penetrated into the brain and reached a maximum concentration in the striatum at approximately 60 min after low- and high-dose treatment. The area under the concentration curve (AUC) ratio increased proportionally at the doses of 10 and 30 mg/kg, which suggested a linear pharmacokinetic manner of ambroxol. The brain penetration of ambroxol was approximately 30-34%, which was defined as the ambroxol AUC blood-to-brain distribution ratio (AUCbrain/AUCblood). The P. tenuifolia extract did not significantly alter the pharmacokinetics of ambroxol in the blood and brain of rats. CONCLUSION: The present study suggests that it is safety without pharmacokinetic interactions for this dosing regimen to use P. tenuifolia extract and ambroxol together.

Scanning Electron Microscopy and Liquid Chromatography for Physical and Chemical Inspection of Industrial Pharmaceutical Traditional Chinese Herbal Medicine.

Multiherbal preparation of Coptidis rhizoma, Scutellariae radix, and Rhei rhizoma is a well-known herbal formula, which is widely used in the prescription for relieving heat toxicity, inflammation of the intestine, and eczema. However, little is known about the characteristics of the physical and chemical qualities of industrial pharmaceutical products. The aim of the study is to develop a liquid chromatography system to examine the quality and quantity of pharmaceutical products. Besides scanning electron microscopy, light microscopy photographs with Congo red staining and iodine-KI staining were used for physical examination of the quality of the pharmaceutical products. A reverse-phase C18 column was used to separate the analytes of baicalin, berberine, rhein, and p-hydroxybenzoate (internal standard) with a gradient eluent mobile phase of acetonitrile and 10 mM NaH2PO4 (pH 3.0, adjusted by orthophosphoric acid). The results demonstrated that a large variety of content range presents among the testing herbal pharmaceutical products. The contents of rhein, baicalin, and berberine were around 0.22-22.46, 0.44-50.79, and 0.41-2.48 mg/g, respectively. The physical examination data demonstrated that different brands of industrial pharmaceutical products have different shapes of granules or rods. In summary, to ensure the clinical efficacy of complicated herbal medicine, both quality and quantity controls are all very important. This study provides a reference standard operating procedure guide for the quality control (QC) with chemical and physical examination for the Chinese herbal pharmaceutical products of San-Huang-Xie-Xin-Tang (SHXXT).