Keloid treatments: an evidence-based systematic review of recent advances.

BACKGROUND: Keloids are pathologic scars that pose a significant functional and cosmetic burden. They are challenging to treat, despite the multitude of treatment modalities currently available. OBJECTIVE: The aim of this study was to conduct an evidence-based review of all prospective data regarding keloid treatments published between 2010 and 2020. METHODS: A systematic literature search of PubMed (National Library of Medicine), Embase (Elsevier), and Cochrane Library (Wiley) was performed in November of 2020. Search strategies with the keywords "keloid" and "treatment" were performed by a medical librarian. The search was limited to prospective studies that were peer-reviewed, reported on clinical outcomes of keloid therapies, and were published in the English language between January 1, 2010, and November 24, 2020. RESULTS: A total of 3462 unique citations were identified, of which 108 studies met inclusion criteria. Current literature supports silicone gel or sheeting with corticosteroid injections as first-line therapy for keloids. Adjuvant intralesional 5-fluorouracil (5-FU), bleomycin, or verapamil can be considered, although mixed results have been reported with each. Laser therapy can be used in combination with intralesional corticosteroids or topical steroids with occlusion to improve drug penetration. Excision of keloids with immediate post-excision radiation therapy is an effective option for recalcitrant lesions. Finally, silicone sheeting and pressure therapy have evidence for reducing keloid recurrence. CONCLUSIONS: This review was limited by heterogeneity of subject characteristics and study outcome measures, small sample sizes, and inconsistent study designs. Larger and more robust controlled studies are necessary to further understand the variety of existing and emerging keloid treatments, including corticosteroids, cryotherapy, intralesional injections, lasers, photodynamic therapy, excision and radiation, pressure dressings, and others.

Thyroid disease in cervical dystonia.

There are many possible etiologies for cervical dystonia (CD), but a cause cannot be identified in most cases. Most recent attention has focused on genetic causes, although a few prior studies have highlighted autoimmune mechanisms instead. Because autoimmune disorders frequently co-exist, the current study evaluated the hypothesis that autoimmune disorders might be more common in CD than neurological controls. The frequency of 32 common autoimmune disorders was evaluated using a systematic survey comparing 300 subjects with CD with 391 neurological controls. The frequency of thyroid disease was significantly higher in CD (20%) compared with controls (6%). Regression analyses that accounted for age and sex revealed an odds ratio of 4.5 (95% CI 2.5-8.1, p < 0.001). All other autoimmune disorders occurred with similar frequencies in CD and controls. Although these studies do not establish a mechanistic link between CD and autoimmune disease, they suggest the need for further attention to a potential relationship, and more specifically with thyroid disease.

The SGLT2i Dapagliflozin Reduces RV Mass Independent of Changes in RV Pressure Induced by Pulmonary Artery Banding.

BACKGROUND: Sodium glucose linked transporter 2 (SGLT2) inhibition not only reduces morbidity and mortality in patients with diagnosed heart failure but also prevents the development of heart failure hospitalization in those at risk. While studies to date have focused on the role of SGLT2 inhibition in left ventricular failure, whether this drug class is efficacious in the treatment and prevention of right heart failure has not been explored. HYPOTHESIS: We hypothesized that SGLT2 inhibition would reduce the structural, functional, and molecular responses to pressure overload of the right ventricle. METHODS: Thirteen-week-old Fischer F344 rats underwent pulmonary artery banding (PAB) or sham surgery prior to being randomized to receive either the SGLT2 inhibitor: dapagliflozin (0.5 mg/kg/day) or vehicle by oral gavage. After 6 weeks of treatment, animals underwent transthoracic echocardiography and invasive hemodynamic studies. Animals were then terminated, and their hearts harvested for structural and molecular analyses. RESULTS: PAB induced features consistent with a compensatory response to increased right ventricular (RV) afterload with elevated mass, end systolic pressure, collagen content, and alteration in calcium handling protein expression (all p < 0.05 when compared to sham + vehicle). Dapagliflozin reduced RV mass, including both wet and dry weight as well as normalizing the protein expression of SERCA 2A, phospho-AMPK and LC3I/II ratio expression (all p < 0.05). SIGNIFICANCE: Dapagliflozin reduces the structural, functional, and molecular manifestations of right ventricular pressure overload. Whether amelioration of these early changes in the RV may ultimately lead to a reduction in RV failure remains to be determined.

One year outcomes of atrial fibrillation ablation: Contemporary analysis of the United States Nationwide Readmission Database.

BACKGROUND: Data on long-term outcomes of catheter ablation (CA) for atrial fibrillation (AF) in outside of clinical trials settings are sparse. OBJECTIVE: We aimed to assess outcomes and readmissions at 1 year following admission for CA for AF. METHODS: Utilizing the Nationwide Readmissions Database (2016-2018), we identified patients with CA among all patients with a primary admission diagnosis of AF, and a control group by propensity score match adjusted for age, sex, comorbidities, CHA2DS2-VASc scores, and the hospital characteristics. The primary outcome was a composite of unplanned heart failure (HF), AF and stroke-related readmissions, and death at 1 year, and secondary outcomes were hospital outcomes and all-cause readmission rates. RESULTS: The study cohort consisted of 29,771 patients undergoing CA and 63,988 controls. Patients undergoing CA were younger with lower CHA2DS2-VASc scores and less comorbidities. Over a follow-up of 170 ±1.1 days, the primary outcome occurred in 5.2% in CA group and 6.0% of controls (hazard ratio [HR] and 95% confidence interval [CI]: 0.86 [0.76-0.94], p = .002). CA affected AF and stroke related readmission, but showed no effect on HF and mortality outcome. Male sex (HR: 0.83 [0.74-0.94], p = .03), younger age (HR: 0.71 [0.61-0.83], p < .001], and lower CHA2DS2-VASc scores (HR: 0.68 [0.55-0.84], p < .001) were associated with lower risk of primary outcome with CA. CONCLUSION: In this study, CA for AF was associated with significantly lower AF and stroke-related admissions, but not to HF or all-cause readmission. Better outcomes were seen among males, younger patients, and in patients with less comorbidities and low CHA2DS2-VASc scores.

Evolution of Multiple Domains of the HIV-1 Envelope Glycoprotein during Coreceptor Switch with CCR5 Antagonist Therapy.

HIV-1 uses CD4 as a receptor and chemokine receptors CCR5 and/or CXCR4 as coreceptors. CCR5 antagonists are a class of antiretrovirals used to inhibit viral entry. Phenotypic prediction algorithms such as Geno2Pheno are used to assess CCR5 antagonist eligibility, for which the V3 region is screened. However, there exist scenarios where the algorithm cannot give an accurate prediction of tropism. The current study examined coreceptor shift of HIV-1 from CCR5-tropic strains to CXCR4-tropic or dual-tropic strains among five subjects in a clinical trial of the CCR5 antagonist vicriviroc. Envelope gene amplicon libraries were constructed and subjected to next-generation sequencing, as well as single-clone sequencing and functional analyses. Approximately half of the amplified full-length single envelope-encoding clones had no significant activity for infection of cells expressing high levels of CD4 and CCR5 or CXCR4. Functional analysis of 9 to 21 individual infectious clones at baseline and at the time of VF were used to construct phylogenetic trees and sequence alignments. These studies confirmed that specific residues and the overall charge of the V3 loop were the major determinants of coreceptor use, in addition to specific residues in other domains of the envelope protein in V1/V2, V4, C3, and C4 domains that may be important for coreceptor shift. These results provide greater insight into the viral genetic determinants of coreceptor shift. IMPORTANCE This study is novel in combining single-genome sequence analysis and next-generation sequencing to characterize HIV-1 quasispecies. The work highlights the importance of mutants present at frequencies of 1% or less in development of drug resistance. This study highlights a critical role of specific amino acid substitutions outside V3 that contribute to coreceptor shift as well as important roles of the V1/V2, V4, C3, and C4 domain residues.

Nondestructive versus advanced post-transplant lymphoproliferative disorder in a single-center pediatric kidney transplant population.

BACKGROUND: Pediatric kidney transplant recipients are at risk for the development of post-transplant lymphoproliferative disorders (PTLD), a group of potentially devastating diseases that present on a spectrum of severity ranging from nondestructive PTLD to more histologically destructive lesions. Currently, there is inadequate evidence to guide evaluation and management of nondestructive PTLD. METHODS: This is a single-center case series of pediatric kidney transplant recipients between January 1, 2008 and December 31, 2019, who were diagnosed with PTLD. The aim was to describe clinical characteristics, presentation, and management of nondestructive versus advanced PTLD. RESULTS: Eighteen patients were diagnosed with nondestructive PTLD and seven with more advanced PTLD histopathology. The majority (66.7%) of nondestructive PTLD patients (n = 16) presented with tonsillar hypertrophy and/or snoring and were managed conservatively, with minimal reduction in tacrolimus dose and no further evaluation. No patient progressed to more advanced PTLD. Advanced PTLD patients (n = 7) were more likely to present with fever, elevated creatinine, a new mass of gastrointestinal symptoms. They received workup with imaging and oncology consultation, and were managed with chemotherapy. CONCLUSIONS: Patients with nondestructive PTLD often present with symptoms of sleep-disordered breathing and can be managed conservatively with excellent clinical outcomes. More study is needed to guide care of this under-researched population.

Use of technology for the objective evaluation of scratching behavior: A systematic review.

INTRODUCTION: Pruritus is a common symptom across various dermatologic conditions, with a negative impact on quality of life. Devices to quantify itch objectively primarily use scratch as a proxy. This review compares and evaluates the performance of technologies aimed at objectively measuring scratch behavior. METHODS: Articles identified from literature searches performed in October 2020 were reviewed and those that did not report a primary statistical performance measure (eg, sensitivity, specificity) were excluded. The articles were independently reviewed by 2 authors. RESULTS: The literature search resulted in 6231 articles, of which 24 met eligibility criteria. Studies were categorized by technology, with actigraphy being the most studied (n = 21). Wrist actigraphy's performance is poorer in pruritic patients and inherently limited in finger-dominant scratch detection. It has moderate correlations with objective measures (Eczema and Area Severity Index/Investigator's Global Assessment: rs(ρ) = 0.70-0.76), but correlations with subjective measures are poor (r2 = 0.06, rs(ρ) = 0.18-0.40 for itch measured using a visual analog scale). This may be due to varied subjective perception of itch or actigraphy's underestimation of scratch. CONCLUSION: Actigraphy's large variability in performance and limited understanding of its specificity for scratch merits larger studies looking at validation of data analysis algorithms and device performance, particularly within target patient populations.

V1 and V2 Domains of HIV Envelope Contribute to CCR5 Antagonist Resistance.

Vicriviroc (VCV) is a CCR5 antagonist that blocks the viral entry of CCR5-tropic (R5) virions by binding to and inducing a conformational change in the chemokine receptor. Clinical resistance to CCR5 antagonists occurs in two phases, competitive and noncompetitive stages. In this study, we analyzed two subjects, from a phase 2b VCV clinical trial, whose quasispecies contained R5 and dual-mixed virions at the earliest recorded time of virological failure (VF). Genotypic analysis of R5-tropic patient-derived envelope genes revealed significant changes in the V1/V2 coding domain and convergence toward a more homogenous sequence under VCV therapy. Additionally, a small population of baseline clones sharing similar V1/V2 and V3 domains with the predominant VF isolate was observed. These clones were denoted preresistant based on their genotype. Preresistant clones and chimeric clones containing V1/V2 regions isolated during VF displayed high 50% inhibitory concentration (IC50) values relative to those at baseline, consistent with early competitive resistance. Genotypic analysis of the dual-tropic clones also showed significant changes in the V1/V2 region, different from the resistant R5-tropic viruses. Our findings suggest that the V1/V2 domain plays a key role in the initial step of development of drug resistance.IMPORTANCE It is believed that each CCR5 antagonist-resistant isolate will develop its own unique set of mutations, making it difficult to identify a signature mutation that can effectively predict CCR5 antagonist resistance. This may explain why we do not observe shared mutations among clinical studies. The present study examined the earliest events in the development of drug resistance with viral quasispecies that continued the use of CCR5 for entry. Genotypic and phenotypic assays demonstrated a distinct role of the variable domain V1/V2 in competitive resistance to CCR5 antagonist therapy. Thus, future studies analyzing the development of clinical resistance should focus on the relationship between the V1/V2 and V3 domains.

Pharmacokinetics, metabolism, and excretion of [14C]axitinib, a vascular endothelial growth factor receptor tyrosine kinase inhibitor, in humans.

The disposition of a single oral dose of 5 mg (100 µCi) of [(14)C]axitinib was investigated in fasted healthy human subjects (N = 8). Axitinib was rapidly absorbed, with a median plasma Tmax of 2.2 hours and a geometric mean Cmax and half-life of 29.2 ng/ml and 10.6 hours, respectively. The plasma total radioactivity-time profile was similar to that of axitinib but the AUC was greater, suggesting the presence of metabolites. The major metabolites in human plasma (0-12 hours), identified as axitinib N-glucuronide (M7) and axitinib sulfoxide (M12), were pharmacologically inactive, and with axitinib comprised 50.4%, 16.2%, and 22.5% of the radioactivity, respectively. In excreta, the majority of radioactivity was recovered in most subjects by 48 hours postdose. The median radioactivity excreted in urine, feces, and total recovery was 22.7%, 37.0%, and 59.7%, respectively. The recovery from feces was variable across subjects (range, 2.5%-60.2%). The metabolites identified in urine were M5 (carboxylic acid), M12 (sulfoxide), M7 (N-glucuronide), M9 (sulfoxide/N-oxide), and M8a (methylhydroxy glucuronide), accounting for 5.7%, 3.5%, 2.6%, 1.7%, and 1.3% of the dose, respectively. The drug-related products identified in feces were unchanged axitinib, M14/15 (mono-oxidation/sulfone), M12a (epoxide), and an unidentified metabolite, comprising 12%, 5.7%, 5.1%, and 5.0% of the dose, respectively. The proposed mechanism to form M5 involved a carbon-carbon bond cleavage via M12a, followed by rearrangement to a ketone intermediate and subsequent Baeyer-Villiger rearrangement, possibly through a peroxide intermediate. In summary, the study characterized axitinib metabolites in circulation and primary elimination pathways of the drug, which were mainly oxidative in nature.

Pharmacokinetics, distribution, and metabolism of [14C]sunitinib in rats, monkeys, and humans.

Sunitinib is an oral multitargeted tyrosine kinase inhibitor approved for the treatment of advanced renal cell carcinoma, imatinib-refractory gastrointestinal stromal tumor, and advanced pancreatic neuroendocrine tumors. The current studies were conducted to characterize the pharmacokinetics, distribution, and metabolism of sunitinib after intravenous and/or oral administrations of [(14)C]sunitinib in rats (5 mg/kg i.v., 15 mg/kg p.o.), monkeys (6 mg/kg p.o.), and humans (50 mg p.o.). After oral administration, plasma concentration of sunitinib and total radioactivity peaked from 3 to 8 h. Plasma terminal elimination half-lives of sunitinib were 8 h in rats, 17 h in monkeys, and 51 h in humans. The majority of radioactivity was excreted to the feces with a smaller fraction of radioactivity excreted to urine in all three species. The bioavailability in female rats was close to 100%, suggesting complete absorption of sunitinib. Whole-body autoradioluminography suggested radioactivity was distributed throughout rat tissues, with the majority of radioactivity cleared within 72 h. Radioactivity was eliminated more slowly from pigmented tissues. Sunitinib was extensively metabolized in all species. Many metabolites were detected both in urine and fecal extracts. The main metabolic pathways were N-de-ethylation and hydroxylation of indolylidene/dimethylpyrrole. N-Oxidation/hydroxylation/desaturation/deamination of N,N'-diethylamine and oxidative defluorination were the minor metabolic pathways. Des-ethyl metabolite M1 was the major circulating metabolite in all three species.

Characterization of human corneal epithelial cell model as a surrogate for corneal permeability assessment: metabolism and transport.

The recently introduced Clonetics human corneal epithelium (cHCE) cell line is considered a promising in vitro permeability model, replacing excised animal cornea to predict corneal permeability of topically administered compounds. The purpose of this study was to further characterize cHCE as a corneal permeability model from both drug metabolism and transport aspects. First, good correlation was found in the permeability values (P(app)) obtained from cHCE and rabbit corneas for various ophthalmic drugs and permeability markers. Second, a previously established real-time quantitative polymerase chain reaction method was used to profile mRNA expression of drug-metabolizing enzymes (major cytochromes P450 and UDP glucuronosyltransferase 1A1) and transporters in cHCE in comparison with human cornea. Findings indicated that 1) the mRNA expression of most metabolizing enzymes tested was lower in cHCE than in excised human cornea, 2) the mRNA expression of efflux transporters [multidrug resistant-associated protein (MRP) 1, MRP2, MRP3, and breast cancer resistance protein], peptide transporters (PEPT1 and PEPT2), and organic cation transporters (OCTN1, OCTN2, OCT1, and OCT3) could be detected in cHCE as in human cornea. However, multidrug resistance (MDR) 1 and organic anion transporting polypeptide 2B1 was not detected in cHCE; 3) cHCE was demonstrated to possess both esterase and ketone reductase activities known to be present in human cornea; and 4) transport studies using probe substrates suggested that both active efflux and uptake transport may be limited in cHCE. As the first detailed report to delineate drug metabolism and transport characteristics of cHCE, this work shed light on the usefulness and potential limitations of cHCE in predicting the corneal permeability of ophthalmic drugs, including ester prodrugs, and transporter substrates.

Single- and multiple-dose disposition kinetics of sunitinib malate, a multitargeted receptor tyrosine kinase inhibitor: comparative plasma kinetics in non-clinical species.

PURPOSE: The purpose of these extensive non-clinical studies was to assess pharmacokinetics and dispositional properties of sunitinib and its primary active metabolite (SU12662). METHODS: Sunitinib was administered in single and repeat oral doses in mice, rats, and monkeys. Assessments were made using liquid-chromatography-tandem mass spectrometric methods, radioactive assays, and quantitative whole body autoradiography. RESULTS: Sunitinib was readily absorbed with good oral bioavailability and linear kinetics at clinically-relevant doses. SU12662 plasma levels were less than those of sunitinib in mice and monkeys, but greater in rats. Sunitinib was extensively distributed with moderate-to-high systemic clearance and eliminated primarily into feces. Single- and repeat-dosing kinetics were similar. A prolonged half-life allowed once-daily dosing, enabling adequate systemic exposure with limited-to-moderate accumulation. In multiple-dose studies with cyclic dosing, drug plasma concentrations cleared from one cycle to the next. CONCLUSIONS: Sunitinib exhibited advantageous pharmacokinetic and dispositional properties in non-clinical species, translating into favorable properties in humans.

Nonclinical antiangiogenesis and antitumor activities of axitinib (AG-013736), an oral, potent, and selective inhibitor of vascular endothelial growth factor receptor tyrosine kinases 1, 2, 3.

PURPOSE: Axitinib (AG-013736) is a potent and selective inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases 1 to 3 that is in clinical development for the treatment of solid tumors. We provide a comprehensive description of its in vitro characteristics and activities, in vivo antiangiogenesis, and antitumor efficacy and translational pharmacology data. EXPERIMENTAL DESIGN: The potency, kinase selectivity, pharmacologic activity, and antitumor efficacy of axitinib were assessed in various nonclinical models. RESULTS: Axitinib inhibits cellular autophosphorylation of VEGF receptors (VEGFR) with picomolar IC(50) values. Counterscreening across multiple kinase and protein panels shows it is selective for VEGFRs. Axitinib blocks VEGF-mediated endothelial cell survival, tube formation, and downstream signaling through endothelial nitric oxide synthase, Akt and extracellular signal-regulated kinase. Following twice daily oral administration, axitinib produces consistent and dose-dependent antitumor efficacy that is associated with blocking VEGFR-2 phosphorylation, vascular permeability, angiogenesis, and concomitant induction of tumor cell apoptosis. Axitinib in combination with chemotherapeutic or targeted agents enhances antitumor efficacy in many tumor models compared with single agent alone. Dose scheduling studies in a human pancreatic tumor xenograft model show that simultaneous administration of axitinib and gemcitabine without prolonged dose interruption or truncation of axitinib produces the greatest antitumor efficacy. The efficacious drug concentrations predicted in nonclinical studies are consistent with the range achieved in the clinic. Although axitinib inhibits platelet-derived growth factor receptors and KIT with nanomolar in vitro potencies, based on pharmacokinetic/pharmacodynamic analysis, axitinib acts primarily as a VEGFR tyrosine kinase inhibitor at the current clinical exposure. CONCLUSIONS: The selectivity, potency for VEGFRs, and robust nonclinical activity may afford broad opportunities for axitinib to improve cancer therapy.

Drug transporter and cytochrome P450 mRNA expression in human ocular barriers: implications for ocular drug disposition.

Studies were designed to quantitatively assess the mRNA expression of 1) 10 cytochrome P450 (P450) enzymes in human cornea, iris-ciliary body (ICB), and retina/choroid relative to their levels in the liver, and of 2) 21 drug transporters in these tissues relative to their levels in human small intestine, liver, or kidney. Potential species differences in mRNA expression of PEPT1, PEPT2, and MDR1 were also assessed in these ocular tissues from rabbit, dog, monkey, and human. P450 expression was either absent or marginal in human cornea, ICB, and retina/choroid, suggesting a limited role for P450-mediated metabolism in ocular drug disposition. In contrast, among 21 key drug efflux and uptake transporters, many exhibited relative expression levels in ocular tissues comparable with those observed in small intestine, liver, or kidney. This robust ocular transporter presence strongly suggests a significant role that transporters may play in ocular barrier function and ocular pharmacokinetics. The highly expressed efflux transporter MRP1 and uptake transporters PEPT2, OCT1, OCTN1, and OCTN2 may be particularly important in absorption, distribution, and clearance of their drug substrates in the eye. Evidence of cross-species ocular transporter expression differences noted in these studies supports the conclusion that transporter expression variability, along with anatomic and physiological differences, should be taken into consideration to better understand animal ocular pharmacokinetic and pharmacodynamic data and the scalability to human for ocular drugs.

Evaluation of capravirine as a CYP3A probe substrate: in vitro and in vivo metabolism of capravirine in rats and dogs.

Metabolism of [(14)C]capravirine was studied via both in vitro and in vivo means in rats and dogs. Mass balance was achieved in rats and dogs, with mean total recovery of radioactivity >86% for each species. Capravirine was well absorbed in rats but only moderately so in dogs. The very low levels of recovered unchanged capravirine and the large number of metabolites observed in rats and dogs indicate that capravirine was eliminated predominantly by metabolism in both species. Capravirine underwent extensive metabolism via oxygenation reactions (predominant pathways in both species), depicolylation and carboxylation in rats, and decarbamation in dogs. The major circulating metabolites of capravirine were two depicolylated products in rats and three decarbamated products in dogs. However, none of the five metabolites was observed in humans, indicating significant species differences in terms of identities and relative abundances of circulating capravirine metabolites. Because the majority of in vivo oxygenated metabolites of capravirine were observed in liver microsomal incubations, the in vitro models provided good insight into the in vivo oxygenation pathways. In conclusion, the diversity (i.e., hydroxylation, sulfoxidation, sulfone formation, and N-oxidation), multiplicity (i.e., mono-, di-, tri-, and tetraoxygenations), and high enzymatic specificity (>90% contribution by CYP3A4 in humans, CYP3A1/2 in rats, and CYP3A12 in dogs) of the capravirine oxygenation reactions observed in humans, rats, and dogs in vivo and in vitro suggest that capravirine can be a useful CYP3A substrate for probing catalytic mechanisms and kinetics of CYP3A enzymes in humans and animal species.

A unique example of drug metabolism: tetra- and penta-oxygenation reactions of capravirine in rats, dogs and humans.

Six tetra- and two penta-oxygenated capravirine metabolites observed in rats, dogs and humans represent the maximum numbers of isomers that can be predicted since oxygenations are restricted at the pyridinyl nitrogen (N-oxidation), sulfur (sulfoxidation), and isopropyl group (hydroxylation), exemplifying a unique case that is very unusual for sequential drug metabolism.

Identification of enzymes responsible for primary and sequential oxygenation reactions of capravirine in human liver microsomes.

Capravirine, a new non-nucleoside reverse transcriptase inhibitor, undergoes extensive oxygenation reactions, including N-oxidation, sulfoxidation, sulfonation, and hydroxylation in humans. Numerous primary (mono-oxygenated) and sequential (di-, tri-, and tetraoxygenated) metabolites of capravirine are formed via the individual or combined oxygenation pathways. In this study, cytochrome P450 enzymes responsible for the primary and sequential oxygenation reactions of capravirine in human liver microsomes were identified at the specific pathway level. The total oxygenation of capravirine is mediated predominantly (>90%) by CYP3A4 and marginally (<10%) by CYP2C8, 2C9, and 2C19 in humans. Specifically, each of the two major mono-oxygenated metabolites C23 (sulfoxide) and C26 (N-oxide), is mediated predominantly (>90%) by CYP3A4 and slightly (<10%) by CYP2C8, the minor tertiary hydroxylated metabolite C19 by CYP3A4, 2C8, and 2C19, and the minor primary hydroxylated metabolite C20 by CYP3A4, 2C8, and 2C9. However, all sequential oxygenation reactions are mediated exclusively by CYP3A4. Due to their relatively insignificant contributions of C19 and C20 to total capravirine metabolism, no attempt was made to determine relative contributions of cytochrome P450 enzymes to the formation of the two minor metabolites.

Inhibiting matrix metalloproteinases with prinomastat produces abnormalities in fetal growth and development in rats.

BACKGROUND: Matrix metalloproteinases (MMPs) play key roles in remodeling of the extracellular matrix during embryogenesis and fetal development. The objective of this study was to determine the effects of prinomastat, a potent selective MMP inhibitor, on fetal growth and development. METHODS: Prinomastat (25, 100, 250 mg/kg/day, p.o.) was administered to pregnant female Sprague-Dawley rats on gestational days (GD) 6-17. A Cesarian section was carried out on GD 20 and the fetuses were evaluated for viability and skeletal and soft tissue abnormalities. RESULTS: Prinomastat treatment at the 250 mg/kg/day dose produced a decrease in body weight and food consumption in the dams. A dose-dependent increase in post-implantation loss was observed in the 100 and 250 mg/kg/day-dose groups, resulting in only 22% of the dams having viable litters for evaluation at the 250 mg/kg/day dose. Fetal skeletal tissue variations and malformations were present in all prinomastat treated groups and their frequency increased with dose. Variations and malformation in fetal soft tissue were also increased at the 100 and 250 mg/kg/day doses. Prinomastat also interfered with fetal growth of rat embryo cultures in vitro. CONCLUSIONS: These data confirm that MMP inhibition has a profound effect on fetal growth and development in vivo and in vitro.

A simple sequential incubation method for deconvoluting the complicated sequential metabolism of capravirine in humans.

Capravirine, a non-nucleoside reverse transcriptase inhibitor for the treatment of human immunodeficiency virus type 1, undergoes extensive oxygenations to numerous sequential metabolites in humans. Because several possible oxygenation pathways may be involved in the formation and/or sequential metabolism of a single metabolite, it is very difficult or even impossible to determine the definitive pathways and their relative contributions to the overall metabolism of capravirine using conventional approaches. For this reason, a human liver microsome-based "sequential incubation" method has been developed to deconvolute the complicated sequential metabolism of capravirine. In brief, the method includes three fundamental steps: 1) 30-min primary incubation of [(14)C]capravirine, 2) isolation of (14)C metabolites from the primary incubate, and 3) 30-min sequential incubation of each isolated (14)C metabolite supplemented with an ongoing (30 min) microsomal incubation with nonlabeled capravirine. Based on the extent of both the disappearance of the isolated precursor (14)C metabolites and the formation of sequential (14)C metabolites, definitive oxygenation pathways of capravirine were assigned. In addition, the percentage contribution of a precursor metabolite to the formation of each of its sequential metabolites (called sequential contribution) and the percentage contribution of a sequential metabolite formed from each of its precursor metabolites (called precursor contribution) were determined. An advantage of this system is that the sequential metabolism of each isolated (14)C metabolite can be monitored selectively by radioactivity in the presence of all relevant metabolic components (i.e., nonlabeled parent and its other metabolites). This methodology should be applicable to mechanistic studies of other compounds involving complicated sequential metabolic reactions when radiolabeled materials are available.