ACD856, a novel positive allosteric modulator of Trk receptors, single ascending doses in healthy subjects: Safety and pharmacokinetics

PURPOSE

AlzeCure Pharma AB is developing novel positive allosteric modulators of Trk-receptors for treatment of Alzheimer's disease, depression, other psychiatric conditions and other disorders where cognition is impaired. The preceding candidate drug ACD855 was shown to have a too long half-life in humans to allow further development. To de-risk the development of the follow-up compound ACD856, the oral single ascending dose study of ACD856 in humans was preceded by an intravenous microdose study, assessing the elimination half-life in plasma.

METHODS

A phase 0 study with a microdose of ACD856 (0.100 mg), was conducted in six healthy male subjects all receiving ACD856. Sequentially, a randomized, placebo-controlled, double-blind Phase I single ascending oral dose study (1 - 150 mg) was conducted, including 56 healthy subjects. Both studies assessed the safety and tolerability, as well as the PK properties of ACD856 after single dose intravenous and oral administration.

RESULTS

ACD856 was well tolerated with no treatment emergent, or dose related adverse events or other safety assessments. In the microdose study, ACD856 exhibited a bi-exponential plasma decline, low distribution volume, low plasma clearance with a half-life of approximately 20 hours. Orally, ACD856 exhibited rapid absorption, an almost complete bioavailability and a dose proportional increase in exposure. While the Cmax was lowered and delayed by food intake, the effect on plasma half-life and the overall bioavailability was low. No renal elimination of ACD856 was detected.

CONCLUSION

The prediction proved accurate demonstrating the value of conducting a microdose study prior to ascending dose studies.

TRIAL REGISTRATION

NCT05783830 March 24, 2023 (microdose study, retrospectively registered) and NCT05077631 October 14, 2021 (single ascending dose study).

Safety, Tolerability, Pharmacokinetics and Quantitative Electroencephalography Assessment of ACD856, a Novel Positive Allosteric Modulator of Trk-Receptors Following Multiple Doses in Healthy Subjects

BACKGROUND

ACD856 is a positive allosteric modulator of tropomyosin receptor kinase (Trk) receptors which has shown to have pro-cognitive and anti-depressant-like effects in various animal models. It is currently in clinical development for the treatment of Alzheimer's disease and other disorders where cognition is impaired and is also considered for indications such as depression or other neuropsychiatric diseases. ACD856 has a novel mechanism of action modulating the activity of the Trk-receptors, resulting in increased stimulation of the neurotrophin signaling pathways. Previous studies applying single intravenous and oral doses of ACD856 indicate that ACD856 is safe and well-tolerated by healthy volunteer subjects, and that it has suitable safety and pharmacokinetic properties for further clinical development.

OBJECTIVES

To investigate the safety and tolerability of 7 days of treatment with multiple ascending oral doses of ACD856 in healthy subjects, and to characterize its pharmacokinetic (PK) properties. In addition, pharmacodynamic effects of ACD856 using quantitative electroencephalography (qEEG) as an indicator for central target engagement were assessed.

DESIGN

This was a prospective, phase I, double-blind, parallel-group, placebo-controlled, randomized study of the safety, tolerability, PK and pharmacodynamics of multiple ascending oral doses of ACD856 in healthy subjects. ACD856 or placebo were administered in 3 ascending dose cohorts of 8 subjects. Within each cohort, subjects were randomized to receive either ACD856 (n=6) or placebo (n=2).

SETTING

The study was conducted at a First-in-Human unit in Sweden.

PARTICIPANTS

Twenty-four healthy male and female subjects.

INTERVENTION

The study medication was administered as an oral solution, with ACD856 or the same contents without the active ingredient (placebo). The dose levels ranged from 10 mg to 90 mg. ACD856 was administered once daily for 7 days, targeting steady state.

MEASUREMENTS

Safety and tolerability assessments included adverse events, laboratory, vital signs, 12-lead electrocardiogram (ECG), physical examination, assessment of stool frequency and questionnaires to assess symptoms of anxiety, depression, as well as suicidal ideation and behavior. In addition, cardiodynamic ECGs were extracted to evaluate cardiac safety. PK parameters were calculated based on measured concentrations of ACD856 in plasma, urine, and cerebrospinal fluid (CSF) samples. Metabolite profiling, characterization and analysis was performed based on and urine samples. qEEG was recorded for patients in the two highest dose cohorts (30 and 90 mg/day) as a pharmacodynamic assessment to explore central target engagement.

RESULTS

Treatment with ACD856 was well tolerated with no serious adverse events. No treatment emergent or dose related trends were observed for any of the safety assessments. ACD856 was rapidly absorbed and reached maximum plasma exposure at 30 to 45 minutes after administration. Steady state was reached before Day 6, with an elimination half-life at steady state of approximately 20 hours. At steady state, ACD856 exhibited accumulation ratios for Cmax and AUC of approximately 1.6 and 1.9 respectively. The exposure, Cmax and AUC0-24, increased proportionally with the dose. There was no unchanged ACD856 detected in urine. The metabolic pattern in urine and plasma was similar, and in alignment with the metabolites observed in preclinical toxicology studies. The level of ACD856 measured in CSF at steady state increased with dose, indicating Central Nervous System (CNS) exposure at relevant levels for pharmacodynamic effects. ACD856 demonstrated significant dose-dependent treatment-associated changes on qEEG parameters. Specifically, increase of the relative theta power and decrease of the fast alpha and beta power was observed, leading to an acceleration of the delta+theta centroid and an increase in the theta/beta ratio.

CONCLUSIONS

ACD856 was well tolerated at the tested dose levels (10-90 mg/daily for 7 days) in healthy subjects. The compound has a robust pharmacokinetic profile, with rapid absorption and dose-dependent exposure. ACD856 was shown to pass the blood-brain-barrier, reach relevant exposure in the CNS and to induce dose-dependent treatment-related changes on qEEG parameters, indicating central target engagement.

Identification of Novel Positive Allosteric Modulators of Neurotrophin Receptors for the Treatment of Cognitive Dysfunction

Alzheimer's disease (AD) is the most common neurodegenerative disorder and results in severe neurodegeneration and progressive cognitive decline. Neurotrophins are growth factors involved in the development and survival of neurons, but also in underlying mechanisms for memory formation such as hippocampal long-term potentiation. Our aim was to identify small molecules with stimulatory effects on the signaling of two neurotrophins, the nerve growth factor (NGF) and the brain derived neurotrophic factor (BDNF). To identify molecules that could potentiate neurotrophin signaling, 25,000 molecules were screened, which led to the identification of the triazinetrione derivatives ACD855 (Ponazuril) and later on ACD856, as positive allosteric modulators of tropomyosin related kinase (Trk) receptors. ACD855 or ACD856 potentiated the cellular signaling of the neurotrophin receptors with EC50 values of 1.9 and 3.2 or 0.38 and 0.30 µM, respectively, for TrkA or TrkB. ACD855 increased acetylcholine levels in the hippocampus by 40% and facilitated long term potentiation in rat brain slices. The compounds acted as cognitive enhancers in a TrkB-dependent manner in several different behavioral models. Finally, the age-induced cognitive dysfunction in 18-month-old mice could be restored to the same level as found in 2-month-old mice after a single treatment of ACD856. We have identified a novel mechanism to modulate the activity of the Trk-receptors. The identification of the positive allosteric modulators of the Trk-receptors might have implications for the treatment of Alzheimer's diseases and other diseases characterized by cognitive impairment.

Assessment of Free Drug Concentration in Cyclodextrin Formulations Is Essential to Determine Drug Potency in Functional In Vitro Assays

Cyclodextrins (CD) have the ability to form inclusion complexes with drugs and can be used as excipients to enhance solubility of poorly soluble drugs. To make accurate estimations of the potency of the drug, knowledge of the free drug concentration is important. The aim of this study was to evaluate the applicability of calculated free drug concentrations toward response measurements in a transient receptor potential vanilloid receptor-1 cell-based in vitro assay. This included accounting for potential competitive CD binding of 2 transient receptor potential vanilloid receptor-1 active entities: 1 antagonist, and 1 agonist (capsaicin). Solubility of the CD-drug complexes was measured, and the ligand to substrate affinity in CD formulations was determined according to the phase-solubility technique. The total concentration of antagonist, agonist, CD, and the binding constants between ligands and CD were used to calculate the free concentration of CD ligands. For capsaicin and 2 of the 3 investigated model drugs, the calculated free drug concentration was consistent with the experimental in vitro data while it was overestimated for one of the compounds. In conclusion, the suggested approach can be used to calculate free drug concentration and competitive binding in CD formulations for the application of cell-based drug functionality assays.

The battle of Alzheimer's Disease - the beginning of the future Unleashing the potential of academic discoveries

Alzheimer's Disease (AD) is the most common form of dementia, affecting approximately 36 million people worldwide. To date there is no preventive or curative treatment available for AD, and in absence of major progress in therapeutic development, AD manifests a concrete socioeconomic threat. The awareness of the growing problem of AD is increasing, exemplified by the recent G8 Dementia Summit, a meeting held in order to set the stage and steer the compass for the future. Simultaneously, and paradoxically, we have seen key players in the pharmaceutical industry that have recently closed or significantly decreased their R&D spending on AD and other CNS disorders. Given the pressing need for new treatments in this area, other actors need to step-in and enter this drug discovery arena complementing the industrial efforts, in order to turn biological and technological progress into novel therapeutics. In this article, we present an example of a novel drug discovery initiative that in a non-profit setting, aims to integrate with both preclinical and clinical academic groups and pharmaceutical industry to explore the therapeutic potential of new concepts in patients, using novel biology, state of the art technologies and rapid concept testing.

Metabolism of sameridine to monocarboxylated products by hepatocytes isolated from the male rat

The metabolism of sameridine (LPB) (an amide-type local anesthetic-analgesic agent with a hexyl side chain) to carboxylic acid derivatives by isolated male rat hepatocytes was studied using gradient reversed-phase HPLC and mass spectrometry. Incubation of sameridine with hepatocytes resulted in the formation of numerous different metabolites. Two carboxylic acids, i.e., the C(6) and C(4) carboxylated derivatives of sameridine (LPB-6'-oic acid and LPB-4'-oic acid), were found to be produced from the intermediate omega-hydroxy metabolite (6'-hydroxy-LPB). Shortening of the alkyl chain in LPB-6'-oic acid by two carbon atoms resulted in LPB-4'-oic acid. However, incubation of rat hepatocytes with 5'-hydroxy-LPB [the (omega-1)-hydroxy derivative of sameridine] did not give rise to any carboxylated derivative. Addition of SKF525A inhibited the metabolism of sameridine by rat hepatocytes, indicating that the initial step is catalyzed by cytochrome P450. Furthermore, the metabolism of sameridine to LPB-4'-oic acid was enhanced in hepatocytes isolated from rats treated with clofibrate, an up-regulator of peroxisomal fatty acid beta-oxidation and of microsomal cytochrome P450 4A. L-Carnitine (which increases the rate of mitochondrial fatty acid beta-oxidation) had no effect on the level of LPB-4'-oic acid produced by isolated rat hepatocytes. The metabolism of 6'-hydroxy-LPB to LPB-6'-oic acid was inhibited almost completely by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase. Considered together, our findings suggest that cytochrome P450 4A, cytosolic dehydrogenases, and the enzymes involved in peroxisomal fatty acid beta-oxidation catalyze the metabolism of sameridine to LPB-4'-oic acid.

Liquid chromatographic bioanalytical determination of ropivacaine, bupivacaine and major metabolites

Bioanalytical methods for the determination of ropivacaine, bupivacaine and their major metabolites in urine and blood plasma are presented. Ropivacaine is a new local anaesthetic drug mainly used for surgery and for postoperative pain relief. The samples are hydrolysed and cleaned using solid-phase extraction and analysed using ion-pair reversed-phase liquid chromatography with gradient elution. The analytes are detected using UV at 210 nm. The methods are highly selective and the limits of quantification were 1 microM in urine and 0.1 microM in plasma, respectively. The between-day variance was generally below 3% (RSD).

Toxicity of bupivacaine and ropivacaine in relation to free plasma concentrations in pregnant rats: a comparative study

The relationship between free drug concentration and toxicity of bupivacaine and ropivacaine, a new local anaesthetic agent, was studied in a pregnant rat model. The compounds were given subcutaneously to rats in late pregnancy. Dose levels (bupivacaine 5.5 to 24 mg/kg and ropivacaine 5.3 to 26 mg/kg) were selected based upon the proposed human dosage and the known pharmacological activity of the compounds. Chewing, spasm, dyspnoea, drowsiness, salivation and convulsions were observed in a dose-dependent manner in the animals given 14 to 24 mg/kg of bupivacaine, while only a few animals receiving 26 mg/kg of ropivacaine showed less severe symptoms. Deaths from clonic convulsions were occasionally seen in animals receiving 14 mg/kg or more of bupivacaine. No animals receiving ropivacaine died. No effects on litter size offspring loss or weight of the offspring at birth were observed with one exception. After 24 mg/kg of bupivacaine an increased postnatal loss of the offsprings were noticed, most likely due to impaired maternal care. Protein binding, at expected Cmax, were significantly lower for ropivacaine (around 49%) compared with bupivacaine (around 69%) at dose levels. The results suggest an increased safety margin before onset of toxic side effects after treatment with ropivacaine, compared to bupivacaine, in pregnant rase.

A GC-MS study of three major acidic metabolites of delta 1-tetrahydrocannabinol

The major urinary metabolite of delta 1-tetrahydrocannabinol (delta 1-THC) (1), delta 1-THC-7-oic acid (2), has been extensively studied for several purposes, including testing in the workplace for drug abuse. Immunoassays in combination with more specific methods such as gas chromatography-mass spectrometry (GC-MS), are commonly used for verification of positive results in the screening. Two additional and recently synthesized acidic metabolites of 1, 4",5"-bisnor-delta 1-THC-7,3"-dioic acid (3) and 4"-hydroxy-delta 1-THC-7-oic acid (4), were studied to widen the scientific basis in the analysis. Five different derivatives were examined using GC-MS. In addition, a new deuterated internal standard for 2, [2H10]-2, was evaluated. According to our results, suitable derivatives of 2, 3, and 4, according to chromatographic properties, are the methyl ester/silyl ether (procedure a), the methyl ester/trifluoroacetate (procedure b), or the silyl ester/silyl ether (procedure c). The estimated recoveries of [2H5]-3 and [2H6]-4 using liquid-liquid extraction were 24% and 50%, respectively. The properties of [2H10]-2 as internal standard were equivalent to those of [2H9]-2 and, under the conditions used, did not appear to give rise to a significantly higher chromatographic resolution from that of 2. However, [2H10]-2 produces ions at different mass numbers, which makes it useful as a complement to the existing deuterated internal standards of 2.

Metabolism and excretion of ropivacaine in humans

The pharmacokinetics, biotransformation, and urinary excretion of ropivacaine (Naropin), a new local anesthetic agent, have been studied in six healthy male volunteers after a 15-min iv infusion of 152 mumol (50 mg) of [14C]ropivacaine, with a specific radioactivity of 22.5 kBq/mumol (8.8 kBq/mg). Blood, urine, and feces were collected for up to 96 hr after administration. The plasma and urine samples were analyzed for unchanged ropivacaine and for four of its metabolites, i.e. 3-OH-2',6'-pipecoloxylidide (3-OH-PPX), 4-OH-ropivacaine, 3-OH-ropivacaine, and the N-dealkylated metabolite PPX, using GC and HPLC methods. The presence of 2,6-xylidine in plasma was also analyzed. The metabolites were quantified after acidic hydrolysis. The radioactivity could be followed in plasma for up to 14 hr after administration, with ropivacaine being the predominant compound in the early samples. The concentrations of the aforementioned metabolites in plasma were below or just above the lower limit of quantification, and no 2,6-xylidine was detected. The maximum plasma concentration of ropivacaine was 5.9 +/- 2.6 microM (1.6 +/- 0.7 mg/liter), with an elimination half-life of 2.0 +/- 0.3 hr and a total plasma clearance of 397 +/- 127 ml/min. The maximum plasma concentration value for the total radioactivity was 5.5 +/- 2.4 microM (1.5 +/- 0.7 mg/liter) and the elimination half-life was 5.4 +/- 2.9 hr. [14C]Ropivacaine and its metabolites were mainly excreted in the urine, with a total recovery of 86 +/- 3% in the urine and 9 +/- 1% in the feces after 96 hr. Most of the radioactivity (about 68%) was excreted within 12 hr. Ropivacaine was extensively metabolized, and only 1 +/- 0.6% of the dose was excreted unchanged in the urine. The major metabolite identified in the urine was conjugated 3-OH-ropivacaine, which was excreted to an extent of 37 +/- 3% of the dose. The urinary excretion of 4-OH-ropivacaine was < 1%, whereas the N-dealkylated metabolites PPX and 3-OH-PPX accounted for 2 and 3% of the dose, respectively. An additional hydroxylated metabolite, 2-OH-methyl-ropivacaine, was tentatively identified in the urine of some volunteers, accounting for about 4-15% of the dose.

A urinary metabolite of delta 1-tetrahydrocannabinol. The first synthesis of 4",5"-bisnor-delta 1-tetrahydrocannabinol-7,3"-dioic acid, and a deuterium labelled analogue

The first synthesis of unlabelled and [2H5]-labelled 4",5"-bisnor-delta 1-THC-7,3"-dioic acid, the major dicarboxylated urinary metabolite of delta 1-THC in man, is presented (preliminary results of this work have been presented in part at the Melbourne Symposium on Cannabis, Australia, September 1987, Ref. 1). The synthesis of methyl 3-(3,5-dihydroxyphenyl)-[3,3-2H2]-propanoate (8) is described in a nine step sequence from 3,5-dimethoxybenzoic acid in an overall yield of 24%. Compound 8 is condensed with a terpene synthon 9 under acidic conditions, acetylated and hydrolyzed with red HgO and HgCl2 to afford the 1-formyl-4",5",7-trisnor-delta 1-THC-3"-oic acid derivative (11). Compound 11 is oxidized using NaClO2 in 2-methyl-2-butene and hydrolyzed to give (+/-)-4",5"-bisnor-delta 1-THC-7,3"-dioic acid (12). The same approach has been used to prepare both the labelled and unlabelled metabolite.

Lack of metabolic racemisation of ropivacaine, determined by liquid chromatography using a chiral AGP column

Ropivacaine hydrochloride monohydrate (ropivacaine) is a new local anaesthetic agent which is administered exclusively as the (-)-(S)-form. The aim of the study was to determine whether metabolic racemisation of (-)-(S)-ropivacaine occurs. This was tested in man, rat, dog, and sheep after different routes of administration. The enantiomers of ropivacaine and two of the major metabolites, 3-hydroxy-ropivacaine and 2',6'-pipecoloxylidide (PPX), were determined in urine samples by liquid chromatography on a Chiral AGP column after liquid-liquid extraction. It was possible to detect < 1% of the (+)-(R)-enantiomer of both ropivacaine and the two major metabolites. In the samples examined, no trace of metabolic racemisation was observed. In pharmacokinetic, pharmacodynamic, toxicological, and metabolic studies, therefore, nonchiral assays are considered to be adequate.

Human urinary excretion profile after smoking and oral administration of [14C]delta 1-tetrahydrocannabinol

The urinary excretion profiles of delta 1-tetrahydrocannabinol (delta 1-THC) metabolites have been evaluated in two chronic and two naive marijuana users after smoking and oral administration of [14C]delta 1-THC. Urine was collected for five days after each administration route and analyzed for total delta 1-THC metabolites by radioactivity determination, for delta 1-THC-7-oic acid by high-performance liquid chromatography, and for cross-reacting cannabinoids by the EMIT d.a.u. cannabinoid assay. The average urinary excretion half-life of 14C-labeled delta 1-THC metabolites was calculated to be 18.2 +/- 4.9 h (+/- SD). The excretion profiles of delta 1-THC-7-oic acid and EMIT readings were similar to the excretion profile of 14C-labeled metabolites in the naive users. However, in the chronic users the excretion profiles of delta 1-THC-7-oic acid and EMIT readings did not resemble the radioactive excretion due to the heavy influence from previous Cannabis use. Between 8-14% of the radioactive dose was recovered in the urine in both user groups after oral administration. Lower urinary recovery was obtained both in the chronic and naive users after smoking--5 and 2%, respectively.

Urinary excretion half-life of delta 1-tetrahydrocannabinol-7-oic acid in heavy marijuana users after smoking

The urinary excretion of the total amount of delta 1-tetrahydrocannabinol (delta 1-THC) metabolites, with special emphasis on delta 1-tetrahydrocannabinol-7-oic acid (delta 1-THC-7-oic acid), was studied in thirteen heavy Cannabis users after smoking administration of delta 1-THC, followed by a four week discontinuation period. The total amount of delta 1-THC metabolites and the levels of delta 1-THC-7-oic acid could be followed up to 25 days after abstinence using EMIT d.a.u. cannabinoid assay and high-performance liquid chromatography (HPLC). The urinary excretion half-life, calculated from the concentrations of delta 1-THC-7-oic acid versus time, ranged from 0.8-9.8 days with a mean (+/- SD) of 3.0 +/- 2.3 days. Most of the delta 1-THC-7-oic acid was excreted as conjugate and only trace amounts of unconjugated delta 1-THC-7-oic acid were detected. The total concentrations of delta 1-THC-7-oic acid in urine were compared to the concentrations of "cross-reacting cannabinoids", within the linear range of 20-75 ng/mL, obtained in the semiquantitative EMIT d.a.u. cannabinoid assay. The average ratio of "EMIT concentrations"/delta 1-THC-7-oic acid concentrations obtained by HPLC analysis was 1.23 +/- 84% (C.V.) for 78 urine samples. A total of 83% of the samples with positive EMIT levels (cutoff 20 ng/mL) was confirmed by HPLC analysis (cutoff 7 ng/mL).

Determination of delta 1-tetrahydrocannabinol in human fat biopsies from marihuana users by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric (GC/MS) method for analysis of delta 1-tetrahydrocannabinol (delta 1-THC) in human fat samples is described. The fat sample, obtained from heavy marihuana users 1 week before and 4 weeks after smoking, is homogenized in hexane + 2-propanol, centrifuged, and the supernatant mixed with Lipidex 5000. The solvent is evaporated and the dried gel is packed in a glass column. delta 1-THC is eluted from the column with methanol + water + acetic acid, diluted with water and the eluent is passed through a bed of Octadecylsilane-bonded silica. After washing and drying, the retained delta 1-THC is eluted with hexane, derivatized with N-methyl-N-(t-butyl-dimethysilyl)trifluoroacetamide (MTBSTFA) and finally purified by HPLC on an Octadecyl Sl 100 column in methanol. The amount of delta 1-THC is determined by GC/MS, using selected ion monitoring, and a deuterated internal standard. The recovery of delta 1-THC is about 80%, and the concentration of delta 1-THC in the fat samples analysed ranged between 0.4 and 193 ng/g wet tissue.

Terminal elimination plasma half-life of delta 1-tetrahydrocannabinol (delta 1-THC) in heavy users of marijuana

The terminal elimination half-life of delta 1-tetrahydrocannabinol (delta 1-THC) was investigated in eight men who were heavy users of marijuana. A stable isotope assay, following smoking deuterium-labeled delta 1-THC, was used to determine plasma concentrations. In two additional users plasma levels were followed after administration of unlabeled delta 1-THC. The subjects were asked to smoke a "loading dose" of 56 mg delta 1-THC during two days and then abstain from all marijuana use for 4 weeks. The pharmacokinetic behavior was consistent with a multicompartment model with a mean plasma elimination half-life of delta 1-THC of 4.3 days when concentrations were followed for 10-15 days after smoking. In the two subjects with detectable plasma levels during 4 weeks, half-lives of 9.6 and 12.6 days was obtained.

Prolonged apparent half-life of delta 1-tetrahydrocannabinol in plasma of chronic marijuana users

The aim of this study was to characterize the elimination half-life of delta 1-tetrahydrocannabinol in blood plasma in chronic marijuana users. The subjects smoked four cigarettes during a two day period, each cigarette containing 15 mg deuterium-labelled delta 1-tetrahydrocannabinol. The plasma concentrations of deuterium-labelled tetrahydrocannabinol were measured for 13 days using gas chromatography-mass spectrometry equipped with selected ion monitoring. The elimination half-life for delta 1-tetrahydrocannabinol in blood plasma was calculated to be 4.1 +/- 1.1 days (range 2.9-5.0 days) from the two week plasma level curves. Albeit the present results are based upon a small sample, an elimination half-life of delta 1-tetrahydrocannabinol in blood plasma of about 4 days is more in line with apparent half-life excretion of delta 1-tetrahydrocannabinol metabolites in the urine of chronic marijuana smokers.

Identification of 5-S-cysteinyldopa by high performance liquid chromatography in biopsies from patients with dysplastic melanocytic nevi

The appearance of 5-[(L)-S-cysteinyl]dopa, a major product in pheomelanogenesis was examined in affected and nonaffected skins from 20 patients with clinical signs of dysplastic melanocytic nevi. Analysis by high performance liquid chromatography and electrochemical detection showed that 20 of the 35 lesions had a pathological formation of 5-[(L)-S-cysteinyl]dopa (0.04-28.86 ng/micrograms acid soluble protein). 5-[(L)-S-cysteinyl]dopa was not detected in any of the normal uninvolved skin samples analyzed.

Pharmacokinetics and excretion of unique beta-adrenergic agonists

beta-Adrenergic agonist analogs (congeners) of isoproterenol in which the N-isopropyl group has been linked to a p-methyl- (119) or p-trifluoromethyl- (143) anilide moiety through a four carbon methylene spacer have been investigated with respect to their plasma pharmacokinetic profiles and biliary and urinary elimination characteristics in rats. In spite of the differences in selectivity of pharmacologic effects and durations of action between these unique beta-adrenergic agonists and isoproterenol, no differences were observed in their pharmacokinetic parameters in plasma after intravenous administration. Plasma clearances were rapid (67-78 ml/min) and the compounds were widely distributed. In contrast to the known elimination characteristics of isoproterenol, biliary excretion was the major pathway for elimination of 119 and 143. Parent drug and 'one' major metabolite peak appeared in HPLC chromatograms of bile collected from rats that received 119 and 143 by intravenous administration. Preliminary evidence suggests that this metabolite peak consists of one or more glucuronide and/or sulfate conjugates. Urinary excretion appears to be of lesser quantitative importance for 119 and 143 than for isoproterenol. The protracted duration of residence of the derivatives in the heart may help to explain the unusual effects and tissue-specific pharmacological properties of these unique beta-adrenergic agonists.

Unexpected adduct ion formation under chemical ionization conditions

As part of our efforts to characterize the in vivo metabolic fate of the antihypertensive agent alpha-methyldopa, we have examined the urine of alpha-methyldopa-treated rats with the aid of a direct insertion probe chemical ionization mass spectral assay. The mass spectrum of the sample obtained by chromatographic purification followed by treatment with ethanolic hydrochloric acid and pentafluoropropionic anhydride displayed an intense ion at m/z 812, consistent with the beta-ethoxy-N,O,O,O-tetrakispentafluoropropionyl derivative of 6-hydroxy-alpha-methyl-norepinephrine, a potential aromatic hydroxylation product of the known alpha-methyldopa metabolite alpha-methyl-norepinephrine. Comparison of this spectrum with the spectrum obtained with the corresponding synthetic 6-hydroxy-alpha-methylnorepinephrine, however, ruled out this possibility. A more thorough examination of the mass spectral data established that the ion at m/z 812 observed with the metabolic species was due to the formation of an unexpected adduct ion between a known metabolite of alpha-methyldopa and an impurity ion formed from a common constituent of urine. This paper summarizes the characterization of this adduct ion.

Stimulation of pheomelanogenesis in cultured B16 melanoma cells by 4-tertiary butylcatechol

Intermediates of pheomelanin in tissue cultured B16 melanoma cells were analyzed by high performance liquid chromatography, and reduced glutathione (GSH), L-dopa, 2-[(L)-S-cysteinyl]-L-dopa (2-SCD) and 5-[(L)-S-cysteinyl]-L-dopa (5-SCD) were quantified. The effects of 4-tertiary butylcatechol (TBC), an antioxidant which causes skin depigmentation, on the levels of the intermediate were then examined. A concentration of 10(-4) M TBC increased the intracellular levels of GSH, 2-SCD and 5-SCD, whereas the L-dopa level was unchanged. The time-course of the increased intermediates corresponded to the elevation of glutathione-metabolizing enzyme activities previously reported by Kawashima et al. [J. invest. Derm. 82, 53 (1984)] in the same cell line exposed to 10(-4) M TBC. The findings establish chemical evidence that TBC stimulates pheomelanogenesis in melanocytes.

A comparison between the metabolism of delta 1-tetrahydrocannabinol by perfused lung and liver of rat and guinea-pig

The metabolism of delta 1-tetrahydrocannabinol (delta 1-THC) by lung and liver of rat and guinea-pig have been studied by isolated perfused-organ techniques. Metabolites were identified by t.l.c. and mass fragmentography. Biotransformation in lungs showed a different quantitative pattern to the livers in both species. 4"-Hydroxy-delta 1-THC was a major metabolite in both rat and guinea-pig lung. 7-Hydroxy-delta 1-THC was another major metabolite in guinea-pig lung, but a minor one in rat lung. 6 alpha-Hydroxy-delta 1-THC and 6,7-dihydroxy-delta 1-THC were formed in small quantities in both species. Small amounts of 6 beta-hydroxy-delta 1-THC were detected in guinea-pig lung in addition to the metabolites mentioned. Livers of rat and guinea-pig formed 7-hydroxy-delta 1-THC as the most abundant metabolite together with minor amounts of 6 alpha-hydroxy- and 6,7-dihydroxy-delta 1-THC. 6 beta-Hydroxy-delta 1-THC was a minor liver metabolite in guinea-pig, and was found in rat only in trace amounts, together with delta 1-THC-6-one. No side-chain hydroxylated metabolites were detected in rat liver, while guinea-pig liver formed trace amounts of 3"-hydroxy- and 4"-hydroxy-delta 1-THC.

Identification of in vitro metabolites of delta 1-tetrahydrocannabinol formed by human livers

Metabolism of delta 1-tetrahydrocannabinol (delta 1-THC) in humans, has been studied in vitro with the 10,000g supernatant fraction of three human livers. One of the livers (H-13) showed very high enzyme activity compared to the other two. The metabolites were characterized by their mass spectra and in most cases by comparison of their mass spectra and chromatographic properties with those of available synthetic references. The metabolic pattern was similar in all three livers, with 7-hydroxy-delta 1-THC as the most abundant metabolite. Furthermore, they all formed compounds oxygenated in the 6-position. Sidechain oxygenation was most pronounced with H-13, whereas trace mounts of 7-hydroxy-epoxide were formed by livers H-13 and H-15.