Characterization of Pharmacokinetics, Biotransformation and Elimination of Pomotrelvir Orally Administered in Healthy Male Adults Using Two [14C]-Labeled Microtracers with Separate Labeling Positions

Pomotrelvir is an orally bioavailable, target antiviral inhibitor of the main protease (Mpro) of coronaviruses, including severe acute respiratory syndrome coronavirus 2, the etiological agent of Coronavirus Disease 2019. The pharmacokinetics, metabolism and elimination of two [14C]-labeled microtracers of 5 µCi/700 mg pomotrelvir with separate labeling positions (isotopomers), [lactam carbonyl-14C-pomotelvir] and [benzene ring-U-14C-pomotrelvir], following a single oral dose in healthy adult males was evaluated in two separate cohorts. Pomotrelvir was rapidly absorbed and eliminated primarily through metabolism and subsequently excreted via urine and feces. There were no differences in pomotrelvir pharmacokinetics between the two cohorts. The mean total radioactive dose recovered was 93.8% (n = 8) in the lactam cohort (58% in urine and 36% in feces) and 94.2% (n = 8) in the benzene cohort (75% in urine and 19% in feces), with ≥80% of [14C] recovered within 96 hours after dosing. About 5% and 3% of the intact pomotrelvir was recovered in feces and urine, respectively. Eleven major metabolites were detected and characterized using liquid chromatography-accelerator mass spectrometry and liquid chromatography tandem mass spectrometry methods, with three and six different metabolites elucidated in the samples collected from lactam and benzene cohorts, respectively, and two metabolites observed in both cohorts. The major metabolism pathway of pomotrelvir is through hydrolysis of its peptide bonds followed by phase II conjugations. These results support that the application of two radiolabeled isotopomers provided a comprehensive metabolite profiling analysis and was a successful approach in identifying the major disposition pathways of pomotrelvir that has complex routes of metabolism. SIGNIFICANCE STATEMENT: An unconventional approach using two differentially labeled [14C] microtracers, [lactam carbonyl-14C-pomotrelvir] and [benzene ring-U-14C-pomotrelvir] evaluated the mass balance of orally administered pomotrelvir in healthy adult males in two separate cohorts. The radioactive dose recovered in excreta was about 94% for both cohorts. While the two isotopomers of the radiolabeled-pomotrelvir showed no major differences in pharmacokinetics overall, they allowed for differential detection of their radiolabeled metabolites and appropriate characterization of their plasma exposure and excretion in urine and feces.

Hydrogel Microparticles Functionalized with Engineered Escherichia coli as Living Lactam Biosensors

Recently there has been an increasing need for synthesizing valued chemicals through biorefineries. Lactams are an essential family of commodity chemicals widely used in the nylon industry with annual production of millions of tons. The bio-production of lactams can substantially benefit from high-throughput lactam sensing strategies for lactam producer screening. We present here a robust and living lactam biosensor that is directly compatible with high-throughput analytical means. The biosensor is a hydrogel microparticle encapsulating living microcolonies of engineered lactam-responsive Escherichia coli. The microparticles feature facile and ultra-high throughput manufacturing of up to 10,000,000 per hour through droplet microfluidics. We show that the biosensors can specifically detect major lactam species in a dose-dependent manner, which can be quantified using flow cytometry. The biosensor could potentially be used for high-throughput metabolic engineering of lactam biosynthesis.

Optimization of desferrioxamine E production by Streptomyces parvulus

Siderophores are produced by a number of microbes to capture iron with outstandingly high affinity, which property also generates biomedical and industrial interests. Desferrioxamine E (DFO-E) secreted by streptomycetes bacteria can be an ideal candidate for iron chelation therapy, which necessitates its cost-effective production for in vitro and animal studies. This study focused on the optimization of DFO-E production by Streptomyces parvulus CBS548.68. Different combinations of various carbon and nitrogen sources as well as the addition of 3-morpholinopropane-1-sulfonic acid (MOPS) markedly affected DFO-E yields, which were attributed, at least in part, to the higher biomass productions found in MOPS-supplemented cultures. In MOPS-supplemented glucose and sodium glutamate medium, DFO-E productions as high as 2,009 ± 90 mg/l of culture medium were reached. High-performance liquid chromatography analysis demonstrated that a simple two-step purification process yielded DFO-E preparations with purities of ∼97%. Matrix assisted laser desorption ionization-time of flight mass spectrometry analysis showed that purified DFO-E always contained traces of desferrioxamine D2.

Determination of 7B3 residues in cotton plants by liquid chromatography/mass spectrometry

A method was developed for the determination of 7B3 (12-propyloxyimino-1,15-pentadecanlactam), a novel macrolactam fungicide, by liquid chromatography/mass spectrometry (LC/MS) with positive electrospray ionization (ESI+). The method used a reversed-phase C18 column and acetonitrile-water (60 + 40, v/v) mobile phase. The quick, easy, cheap, effective, rugged, and safe method was used for extraction of 7B3 from cotton plants, which involved the extraction of 10 g homogenized sample with 10 mL acetonitrile, followed by the addition of 4 g anhydrous MgSO4 and 1.0 g NaCl. After centrifugation, 1 mL of the buffered acetonitrile extract was transferred into a tube containing 50 mg primary secondary amine sorbent and 100 mg anhydrous MgSO4. After shaking and centrifugation, the final extract was transferred to an autosampler vial for concurrent analysis by LC/MS. The results of 7B3 determined by LC/MS in the selective ion monitoring mode were linear, and the matrix effect of the method was evaluated. The average recoveries of 7B3 fortified at different levels were within 84.1-100.2%, and the relative standard deviations were <7.5% for all samples analyzed. The method limit of detection and the limit of quantitation values were 0.03 and 0.1 mg/kg, respectively. The proposed method was successfully applied to determine 7B3 residues in practical samples. This method is sensitive, accurate, reliable, simple, and safe.

Reduction of in-source collision-induced dissociation and thermolysis of sulopenem prodrugs for quantitative liquid chromatography/electrospray ionization mass spectrometric analysis by promoting sodium adduct formation

Six chromatographically resolved sulopenem prodrugs were monitored for their potential to undergo both in-source collision-induced dissociation (CID) and thermolysis. Initial Q1 scans for each prodrug revealed the formation of intense [Prodrug2 + H]+, [Prodrug2 + Na]+, [Prodrug + Na]+, and [Sulopenem + Na]+ ions. Non-adduct-associated sulopenem ([Sulopenem + H]+) along with several additional lower mass ions were also observed. Product ion scans of [Prodrug3 + Na]+ showed the retention of the sodium adduct in the collision cell continuing down to opening of the beta-lactam ring. In-source CID and temperature experiments were conducted under chromatographic conditions while monitoring several of the latter ion transitions (i.e., adducts, dimers and degradants/fragments) for a given prodrug. The resulting ion profiles indicated the regions of greatest stability for temperature and declustering potential (DP) that provided the highest signal intensity for each prodrug and minimized in-source degradation. The heightened stability of adduct ions, relative to their appropriate counterpart (i.e., dimer to dimer adduct and prodrug to prodrug adduct ions), was observed under elevated temperature and DP conditions. The addition of 100 microM sodium to the mobile phase further enhanced the formation of these more stable adduct ions, yielding an optimal [Prodrug + Na]+ ion signal at temperatures from 400 to 600 degrees C. A clinical liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for sulopenem prodrug PF-04064900 in buffered whole blood was successfully validated using sodium-fortified mobile phase and the [PF-04064900 + Na]+ ion for quantitation. A conservative five-fold increase in sensitivity from previously validated preclinical assays using the [PF-04064900 + H]+ precursor ion was achieved.

Chemoselective Syntheses of γ-Butyrolactams Using Vinyl Sulfilimines and Dichloroketene

Reactions between vinyl sulfilimines and dichloroketene generated in situ from trichloroacetyl chloride in the presence of zinc-copper couple give mixtures of alpha-dichloro-gamma-butyrolactams and alpha-dichloro-gamma-butyrolactone imines. Fine-tuning of substituents within vinyl sulfilimines results in reactions with good chemoselectivity and yield for lactams.

Cold-temperature stability of five beta-lactam antibiotics in bovine milk and milk extracts prepared for liquid chromatography-electrospray ionization tandem mass spectrometry analysis

The stability of five major beta-lactam antibiotics (amoxicillin, ampicillin, cloxacillin, oxacillin, and penicillin G) in fortified milk and in milk extracts prepared for LC-ESIMS/MS analysis was studied at varying cold temperatures (4, -20, and -76 degrees C). Storage of milk samples at 4 degrees C resulted in measurable losses of all beta-lactams after 6 days (>50% in most cases). Slow degradation of penicillin G, cloxacillin, and oxacillin was observed in milk stored at -20 degrees C, but no losses were recorded at -76 degrees C over 4 weeks. All antibiotics showed good stability at all temperature tested in milk extracts prepared for LC-ESIMS/MS analysis. The results of this study emphasize adherence to adequate sample handling and storage protocols as to reflect residue levels at the time of sample submission.

Meeting maximum residue limits: an improved screening technique for the rapid detection of antimicrobial residues in animal food products

A rapid, high-throughput antimicrobial screening assay was developed using either a physical fluid extraction or a solvent extraction technique coupled to the commercially available PremiTest. The solvent extraction approach was fully validated for a wide range of tissues and the fluid extraction approach partially validated for porcine muscle. Both procedures can detect a wide range of antimicrobial compounds at or below maximum residue limit concentrations. The use of a solvent extraction provides an enhanced test capable of detecting a wider range of drugs than the fluid extraction approach at or below half maximum residue limit levels in a variety of matrices. Biochemical methods for the class-specific identification of beta-lactams and sulphonamides following initial screening were developed and validated. The approach is a significant improvement on existing methodologies as a tool for residues monitoring in surveillance programmes.

Efficient Syntheses of Oncinotine and Neooncinotine

We have synthesized two natural alkaloids, oncinotine (1) and neooncinotine (2), by means of efficient ring-closing metathesis (RCM) reactions. The required dienes for RCM were assembled from three basic components: 2-allylpiperidine (5), 9-decenoic acid (6), and diamines 7. We developed two different methods to achieve the linkage: the Michael addition of acrylamide and two amidations of succinic anhydride. The Grubbs catalyst was used to form the 17- and 18-membered lactams in 50% and 68% yields, respectively.

Structure elucidation of 11-amino-8-hydroxypentacyclo[5.4.0.0(2, 6).0(3, 10).0(5, 9)]undecane-8,11-lactam through selective acetylation and complete 1H and 13C NMR spectral assignment of the mono-, di- and triacetates

NMR techniques cannot unambiguously distinguish between 11-amino-8-hydroxypentacyclo[5.4.0.0(2, 6).0(3, 10).0(5, 9)]undecane-8,11-lactam and 8-amino-11-hydroxypentacyclo[5.4.0.0(2, 6).0(3, 10).0(5, 9)]undecane-8,11-lactam, both of which are possible products during the reaction of pentacyclo[5.4.0.0(2, 6).0(3, 10).0(5, 9)]undecane-8,11-dione with Strecker reagents. Treatment of 11-amino-8-hydroxy-pentacyclo[5.4.0.0(2, 6).0(3, 10).0(5, 9)]undecane-8,11-lactam with acetic anhydride at room temperature produced a monoacetate. With acetic anhydride containing sodium acetate, a triacetate was obtained at reflux temperature. Treatment with acetyl chloride and N,N-dimethylaniline produced a diacetate. High-field 1H and 13C NMR techniques were used in the structure elucidation and assignment of the different NMR resonances of these three acetylated compounds.

Development and validation of analytical methods for monomeric and oligomeric migrants from nylon 12 packaging materials

Analytical methods for the determination of laurolactam--the monomer of nylon 12--as well as the cyclic dimer and trimer were established. High performance liquid chromatography using ultraviolet (HPLC-UV) and mass spectrometric detection (HPLC-MS) were both found suitable to identify and quantify monomer, cyclic dimer and trimer well below the specific migration limit (SML) of laurolactam, being 5 mg/kg of food (simulant). Gas chromatography with flame ionisation detection (GC-FID) showed to be an appropriate method for the detection of only laurolactam in aqueous and fatty food simulants. Food simulants could be analysed directly by all three methods, or after a change of solvents. For olive oil, a method for sample clean-up by size-exclusion chromatography (SEC) was established.

Chiral separations by capillary electrophoresis in process chemistry

The utility of capillary electrophoresis in process chemistry to evaluate/optimize a synthetic organic process like classical resolution is demonstrated. Simultaneous monitoring of degradation products and optical purity is shown.

Identification of lactams as in vitro metabolites of piperidine-type phenothiazine antipsychotic drugs

The metabolism of the piperidine-type phenothiazine antipsychotic agents thioridazine, mesoridazine and sulforidazine was studied in vitro with 10,000 g liver supernatants obtained from rats and dogs. After incubations at 37 degrees C for different time intervals, the incubates were extracted with dichloromethane and the isolated compounds analyzed by HPLC, direct probe MS and on-line HPLC-MS. Five lactam metabolites of these three drugs were unequivocally identified in the rat in vitro system, but none was found in dog preparations; at least one lactam metabolite was identified for each drug in the rat. The lactams of thioridazine and thioridazine ring sulfoxide were characterized as metabolites of thioridazine for the first time in any system. The other three lactam metabolites, namely the lactams of mesoridazine, sulforidazine and mesoridazine ring sulfoxide, were found in vitro for the first time, although they have been previously reported as in vivo metabolites of these drugs. The results indicate that rat would be a more suitable animal model than dog for further studies on the formation of lactam metabolites of these drugs.

Relation of the heat resistance of bacterial spores to chemical composition and structure. II. Relation to cortex and structure

The relation between the amount of cortex, measured as total hexosamine, as diaminopimelic acid and as muramic lactam, and the heat resistance of spores of five different strains of Bacillus stearothermophilus was studied. Electron micrographs of thin sections of the spores were made to relate the structure of the spores to chemical and thermal characteristics. It was found that the amount of the cortex was significantly related to heat resistance of the spores. Strains with more electron-dense and better organized cortices were found to express higher heat resistance.

[The active structure of tumor promoters]

Diterpene esters containing 12-0-tetradecanoylphorbol-13-acetate (TPA) and the alkaloid teleocidins are structurally unrelated natural products that exhibit similar potent skin tumor-promoting activity. These promoters are classified as TPA-type promoters because they bind equally to the phorbol ester receptor. TPA can be considered as an amphiphilic compound, with a hydrophilic domain spanning the C-3 to C-20 region of the molecule and a lipophilic domain consisting of the acyl substituents on C-12 and C-13. Teleocidins can also be considered as amphiphilic compounds, with the hydrophilic domain spanning the C-11 to C-14 region of the molecule and the lipophilic domain consisting of the alkyl substituents on C-6, C-7 and C-12. Teleocidins exist in two conformational states, the TWIST form and the SOFA form, in solution. From the ratio of the two conformations in solution, the free-energy difference between them was calculated to be 0-1.5 kcal/mol. Therefore a possible role of one of the two conformations should be considered in the modeling of receptor mapping. Computer modeling of the SOFA form of teleocidins and TPA showed a marked similarity with regards to the hydrogen bonding sites of the hydrophilic substituents. In this case, good superposition of the lipophilic regions of both types of compounds was obtained.

Studies on the biosynthesis of clavulanic acid. III. Incorporation of DL-[3,4-13C2]glutamic acid

The role of glutamate in clavulanic acid biosynthesis was investigated by feeding DL-[3,4-13C2]glutamate to a Streptomyces clavuligerus fermentation. The DL-[3,4-13C2]glutamate was synthesised by reacting [2-13C]diethylmalonate with O-tosyl-N-benzoyl-[3-13C]dehydroserine ethyl ester, which in turn was synthesised by condensing [13C]ethylformate with N-benzoylglycine ethyl ester. 13C NMR examination of the benzyl clavulanate derived from the fermentation revealed the predicted labelling of carbons 2 and 8 with accompanying 13C-13C spin-spin coupling. Other enrichments and couplings were observed which could be explained by metabolism of the labelled glutamate via the tricarboxylic acid cycle to give further clavulanic acid precursors. These results confirm that glutamate provides the oxazolidine carbon skeleton as predicted by previous experiments.

Epithienamycins. II. Isolation and structure assignment

At least six distinct beta-lactam antibiotics of the epithienamycin family are produced by a strain of Streptomyces flavogriseus MB 4638. Each of the six can be isolated in substantially pure form by column chromatography using Dowex 1, Amberlite XAD-2 and Biogel packings. The structures were established by comparison of the ultraviolet, proton magnetic resonance and mass spectral characteristics with those of thienamycin and its derivatives. All six compounds contain the carbapenem ring system which is also found in thienamycin. They differ from each other and from thienamycin by chemical modifications and/or stereoisomerism. Enzymatically deacetylated epithienamycin A has the properties of an isomer of thienamycin.

Association of 6-oxo-piperidine-2-carboxylic acid with penicillin V. Production on Penicillium chrysogenum fermentations

Analysis of a 13C NMR spectrum of a concentrated broth from Penicillium chrysogenum fermentation revealed the presence of penicillin V and 6-oxo-piperidine-2-carboxylic acid(1) as the principal constituents. The latter lactam, identical to an authentic sample prepared by the cyclization of alpha-aminoadipic acid was present to the extent of 28 mol% of penicillin V. The lactam isolated form the broth was nearly racemic, having a slight excess of the L-isomer. This isolation provides further evidence regarding the biosynthetic precursors of the hydrophobic penicillins.

Effect of 60Co-irradiation on penicillin G procaine in veterinary mastitis products

The effect of 60Co-irradiation on penicillin G procaine in a peanut oil-based veterinary mastitis product was examined by reversed-phase high-performance liquid chromatography (HPLC). The HPLC method is capable of separating and quantifying procaine, penicillin G, and various degradation compounds. Penicillin G recovery from a placebo formulation was 100.4% with a relative standard deviation of less than 1%. When irradiated at 4.0 Mrads, the penicillin G in two product lots decreased slightly (approximately 1-2%) with a corresponding increase in two compounds inherently present in bulk penicillin G powder. These compounds may be formed in abundance by treating penicillin G in an acidic solution. From the mass spectrometric analysis and the relative retention data with authentic compounds, these compounds were identified as benzylpenilloaldehyde and benzylpenaldic acid. Values obtained by the HPLC method on the product irradiated and stored at various temperatures correlated well with those of the microbiological assay. No significant decrease in the procaine was detected even after 4.0-Mrad irradiation. The HPLC method is applicable for analysis of other beta-lactam antibiotics.

Determination of major impurity in chlordiazepoxide formulations and drug substance

Procedures for quantitating the lactam impurity, 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide, which can be present in chlordiazepoxide formulations, is presented. The method consists of trapping chlordiazepoxide in sulfuric acid in kieselguhr, eluting the impurity with ether, and quantitating by UV spectrophotometry in absolute alcohol at 312 nm.

Identification of ornithine and arginine conjugates of cholic acid by mass spectrometry

Nalpha-Cholylornithine, -arginine, and -histidine were prepared according to a method previously employed for the chemical synthesis of the monoamino acid conjugates of bile acids. The products were shown to involve the alpha amino group of the dibasic amino acids by examination of the mass spectra of the original compounds, their lactams, their methyl esters and the methyl ester acetates. Only the methyl ester acetates gave detectable amounts of molecular ion. The free acids and the methyl esters of Nalpha-cholylornithine and -arginine gave identical lactams upon sublimation from the direct insertion probe. The synthetic Nalpha-cholylarginine was shown to yield a mass spectrum identical to that of an arginocholic acid recovered from the bile of an isolated perfused rat liver.

Fluorometric and GLC analyses of aristolochic acid

Aristolochic acid is a natural product with possible implication in Balkan endemic nephropathy. A convenient fluorometric assay for the compound is described based on reduction to the lactam and measurement of the intensity of fluorescence. The limit of sensitivity was 0.05 mug/ml. A GLC assay is also described, based on flash methylation of aristolochic acid and its lactam using trimethylanilinium hydroxide. Conditions for optimum performance with a sensitivity limit of 1-5 mug/ml are described.

Spectrophotometric determination of ampicillin sodium in the presence of its degradation and polymerization products

A spectrophotometric method is described for the quantitative determination of ampicillin sodium [sodium salt of 6-(d(–)-phenylacetamido) penicillanic acid]. The method involves acetylation of ampicillin with acetic anhydride in aqueous solution at pH 9 to yield α-acetamido benzylpenicillin and subsequent measurement at 325 nm of α-acetamidobenzylpenicillenic acid mercuric mercaptide, formed in a quantitative yield on heating for 30 min at 60° in a 1·0m imidazole and 8 times 10−4m mercuric chloride solution at pH 6·8. It has been demonstrated that degradation products do not interfere in the method whereas those di- and polymerization products of ampicillin which contain an intact β-lactam ring are capable of reacting with imidazole with the formation of penicillenic acid. A technique involving acid-catalysed opening of the β-lactam ring of these products under conditions where ampicillin is degraded to only a minor extent has been developed, and besides permitting a selective determination of ampicillin the technique permits the determination of the polymeric substances.