Biomedical subjects

Stefan Hartmann

Publications and source records attributed to Stefan Hartmann.

11 recordsLinked to original sources

PubMed2026

An integrated single-cell and spatial proteotranscriptomics atlas of fibroblast-driven immunoregulation within the human adult oral cavity.

The immunoregulatory architecture of human oral tissues remains poorly defined. We present an integrated single-cell and spatial proteotranscriptomic atlas profiling >250,000 single-cell transcriptomes and >4 million spatially resolved cells across 13 niches. Using our AI-enabled AstroSuite, we defined neighborhoods and interaction modules, revealing peri-epithelial fibroblast-centered hubs enriched in effector cytokines. We harmonized fibroblast subtypes (universal, immune, peri-epithelial, peri-vascular, peri-neural, antigen-presenting cell [APC]-like, stress responsive, and myofibroblasts) with stress-responsive subtypes partitioning between mucosae and glands (type I and II). Spatial multiomics mapped ligand-receptor programs and identified mucosal stress-responsive fibroblasts as putative immunoregulatory hubs. Niche-aware integration of healthy and diseased datasets revealed fibroblast rewiring into inflammatory and reparative niches. Disease neighborhoods exhibited expansion of major histocompatibility complex (MHC)-I+, MHC-II+, and programmed cell death ligand 1 (PD-L1)+ fibroblasts and predicted spatial engagement with T cells at tertiary lymphoid structures. Together, this atlas identifies fibroblasts as central regulators of structural immunity and provides a scalable framework to target stromal-immune interactions across barrier organs.

Journal Article↗

PubMed2007

Oral-intravenous crossover study of fingolimod pharmacokinetics, lymphocyte responses and cardiac effects.

OBJECTIVE: The pharmacokinetics and lymphocyte responses to the immunomodulator fingolimod (FTY720) were characterized after oral and intravenous administration. METHODS: In this randomized, two-period crossover study 11 evaluable healthy subjects received single doses of fingolimod 1.25 mg orally and 1 mg intravenously infused over 2 h. The pharmacokinetics of fingolimod, blood lymphocyte counts and heart rate were characterized for 28 days after each dose. RESULTS: After oral administration, Cmax was 1.1+/-0.2 ng/ml occurring at 12 h postdose and the AUC was 201+/-31 ng.h/ml. After intravenous infusion, Cmax was 4.9+/-0.8 ng/ml, AUC was 175+/-50 ng. h/ml, clearance was 6.3+/-2.3 l/h and distribution volume was 1199+/-260 l. The oral/intravenous ratio of dose-normalized AUCs was 0.94 (95%CI: 0.78-1.12). The pharmacologically active metabolite fingolimod-phosphate was quantifiable near its peak after oral administration but not after intravenous administration. The mean lymphocyte nadir occurred on day 1 and was 35% lower after oral (0.74x10(9)/l) than after intravenous (1.15x10(9)/l) administration. Lymphocytes recovered to the normal range by day 15 for both treatments. The mean heart rate nadir occurred 3-4 h postdose and was 11% lower after oral administration (47 bpm) versus intravenous administration (53 bpm). CONCLUSIONS: Average systemic exposure to fingolimod was similar after oral and intravenous administration. However, the acute decrease in lymphocyte counts was weaker after intravenous administration, likely because of lower blood levels of the active metabolite fingolimod-phosphate compared with oral administration.

Administration, Oral↗

PubMed2006

Pimecrolimus: absorption, distribution, metabolism, and excretion in healthy volunteers after a single oral dose and supplementary investigations in vitro.

The absorption and disposition of pimecrolimus, a calcineurin inhibitor developed for the treatment of inflammatory skin diseases, was investigated in four healthy volunteers after a single oral dose of 15 mg of [(3)H]pimecrolimus. Supplementary information was obtained from in vitro experiments. Pimecrolimus was rapidly absorbed. After t(max) (1-3 h), its blood concentrations fell quickly to 3% of C(max) at 24 h, followed by a slow terminal elimination phase (average t(1/2) 62 h). Radioactivity in blood decreased more slowly (8% of C(max) at 24 h). The tissue and blood cell distribution of pimecrolimus was high. The metabolism of pimecrolimus in vivo, which could be well reproduced in vitro (human liver microsomes), was highly complex and involved multiple oxidative O-demethylations and hydroxylations. In blood, pimecrolimus was the major radiolabeled component up to 24 h (49% of radioactivity area under the concentration-time curve(0-24) h), accompanied by a large number of minor metabolites. The average fecal excretion of radioactivity between 0 and 240 h amounted to 78% of dose and represented predominantly a complex mixture of metabolites. In urine, 0 to 240 h, only about 2.5% of the dose and no parent drug was excreted. Hence, pimecrolimus was eliminated almost exclusively by oxidative metabolism. The biotransformation of pimecrolimus was largely catalyzed by CYP3A4/5. Metabolite pools generated in vitro showed low activity in a calcineurin-dependent T-cell activation assay. Hence, metabolites do not seem to contribute significantly to the pharmacological activity of pimecrolimus.

Adult↗

PubMed2006

A human lymph node in vitro--challenges and progress.

Extracorporeal human lymphatic organs are expected to be excellent tools in the study of human molecular and cellular bases of the immunologic balance and tissue harmony. A rational approach and process to design a device and a procedure to recreate the human lymph node environment in vitro is described with emphasis on T-cell activation. Based on this approach, a bioreactor and a process supporting self-assembly of human lymphatic tissues due to proper emulation of human architecture and homeostasis could be developed.

Bioreactors↗

PubMed2006

Fingolimod (FTY720) in severe hepatic impairment: pharmacokinetics and relationship to markers of liver function.

The authors assessed the impact of severe hepatic impairment on the disposition of fingolimod--a sphingosine-1-phosphate receptor immunomodulator primarily metabolized by CYP4F2--in 6 patients and 6 matched healthy controls who received a single 5-mg oral dose. Compared with healthy controls, severe hepatic-impaired subjects had a doubled area under the concentration time curve (AUC) and 50% prolonged elimination half-life but a similar peak blood concentration. When these data were combined with those from a previous study in mild and moderate hepatic-impaired subjects, there were significant positive correlations between fingolimod AUC versus bilirubin (r = 0.683) and prothrombin time (r = 0.777) and a significant negative correlation versus albumin (r = 0.578), confirming the importance of liver function for fingolimod clearance. For patients with severe hepatic impairment (Child-Pugh class C), a standard first dose of fingolimod could be given followed by a maintenance dose that is reduced by half from the normal maintenance dose.

Adult↗

PubMed2005

Exposure to retinyl esters, retinol, and retinoic acids in non-pregnant women following increasing single and repeated oral doses of vitamin A.

BACKGROUND: High intakes of vitamin A cause congenital malformations in experimental animals with elevated generation of retinoic acids (RA). Results in humans are conflicting. OBJECTIVE: To evaluate plasma concentration-time curves of retinyl esters, retinol and their metabolites at increasing doses of vitamin A. METHODS: An open-label dose-response study. Non-pregnant females (3 groups with n = 12; 18-40 years) received once daily oral doses of vitamin A palmitate up to 30,000 IU/day over 21 days. The area under the plasma concentration-time curve (AUC(24h)) served as indicator for exposure. RESULTS: AUC(24h) of retinyl esters increased linearly with dose. Retinol concentrations were unaffected. All-trans RA exhibited a diurnal-like concentration-time profile (Cmax at 3 h; Cmin at 8 h), concentrations decreasing below pre-dose levels at 5 h and regaining pre-dose levels at 16 h. The maximum temporary increase in exposure was 33% (single dose) and 19% (repeated doses) above baseline, but AUC(24h) remained unaltered. AUC(24h) increased linearly with dose for 13-cis RA and 13-cis-4-oxo RA. Repeated doses caused a 25% increase in exposure with the highest vitamin A intake. Accumulation of 13-cis-4-oxo RA at 30,000 IU/day doubled compared to the 4,000 IU/day intake. CONCLUSION: Repeated oral doses of up to 30,000 IU of vitamin A in addition to dietary vitamin A were without safety concern. Safe doses are probably higher, since plasma concentrations and exposure to RA remained at levels earlier shown to be without increased risk of teratogenicity in pregnant women.

Administration, Oral↗

PubMed2005

Exposure to retinoic acids in non-pregnant women following high vitamin A intake with a liver meal.

Animal liver is a rich source of vitamin A. Due to retinoic acid (RA) metabolites, vitamin A has a teratogenic potential and women are generally advised to avoid or to limit the consumption of liver during pregnancy. In a recent study in non-pregnant female volunteers following single and repeated doses of up to 30,000 IU/day of vitamin A as a supplement, the plasma concentration time curve of all-trans RA acid showed a diurnal-like profile. But, the overall exposure (AUC24h) remained essentially unaltered whereas AUC24h increased linearly with dose for 13-cis and 13-cis-4-oxo RA. The current study in non-pregnant female volunteers showed that a single high vitamin A intake with a liver meal (up to 120,000 IU) exhibited a similar diurnal-like plasma concentration time curve for all-trans RA and its overall exposure remained also unaltered, despite a temporary two-fold increase in peak plasma concentration. Concentrations of 13-cis and 13-cis-4-oxo RA increased several-fold after a liver meal, and exposure (AUC24h) increased three- to five-fold. Pooling our results with data in the literature revealed a linear relation between the mean AUC24h of 13-cis and 13-cis-4-oxo RA and vitamin A intake with liver. Metabolism to all-trans RA of vitamin A with liver seems not to be of safety concern. However, the observed increase of plasma concentrations and the dose-dependent increase in exposure to 13-cis and 13-cis-4-oxo RA support the current safety recommendations on vitamin A intake and suggest that women should be cautious regarding their consumption of liver-containing meals during pregnancy.

Adolescent↗

PubMed2003

Pharmacokinetics of pimecrolimus, a novel nonsteroid anti-inflammatory drug, after single and multiple oral administration.

OBJECTIVE: To investigate the pharmacokinetics and tolerability of the new nonsteroid anti-inflammatory pimecrolimus (SDZ ASM 981, Elidel) after oral administration. DESIGN: A single-dose, randomised, double-blind, placebo-controlled, dose-rising, parallel-group study in healthy male volunteers, and a multiple-dose, randomised, double-blind, placebo-controlled, dose-rising study in patients with psoriasis. SETTING: One centre in France (single-dose study) and one centre in Austria (multiple-dose study). METHODS: The first study investigated the pharmacokinetics and tolerability of ascending single oral doses of pimecrolimus (5-60mg). The 60mg dose was repeated in the same subjects after a fat-rich breakfast. The second study investigated the pharmacokinetics, tolerability, safety and efficacy of rising oral doses administered once daily (5-20mg) or twice daily (20 and 30mg) for 28 days. Only the pharmacokinetic, safety and tolerability data of this study are presented. OUTCOME MEASURES AND RESULTS: Oral administration of pimecrolimus was well tolerated up to the highest dose (60mg). Pimecrolimus was rapidly absorbed (time to maximum blood concentration 0.7-2 hours). A high-fat meal before drug administration delayed the time to peak concentration. Blood concentrations appear to have a long-terminal half-life (30-40 hours after a single dose in fasted subjects, 50-100 hours after the final dose on day 28 in psoriasis patients). After multiple doses, steady state was attained after 6-13 days. Maximum blood concentrations (C(max)) and exposure (area under the concentration-time curve; AUC) were broadly dose proportional. At the highest dose administered in the multiple-dose study (30mg twice daily), a C(max ) of 54.7 microg/L was measured and an AUC(24) of 589.8 microg.h/L was calculated at steady state (day 13). CONCLUSION: The results support further evaluation of the therapeutic potential of oral pimecrolimus for the treatment of inflammatory diseases.

Administration, Oral↗

PubMed2002

Pharmacokinetic and pharmacodynamic assessments of HMG-CoA reductase inhibitors when coadministered with everolimus.

The authors assessed the mutual influence of the immunosuppressant everolimus (Certican) and the HMG-CoA reductase inhibitors atorvastatin and pravastatin when coadministered based on pharmacokinetic and pharmacodynamic measures. In this randomized, open-label, three-way crossover study, 24 healthy men received three single-dose oral treatments: 2 mg everolimus, 20 mg atorvastatin (n = 12) or 20 mg pravastatin (n = 12), and the respective statin coadministered with everolimus. Consecutive treatments were separated by a 14-day washout. The pharmacokinetics of all three drugs and total HMG-CoA reductase inhibitors were measured. Everolimus Cmax was reduced by 9% and 10% with atorvastatin and pravastatin coadministration; the corresponding decreases in everolimus AUC were 5% and 6%, respectively. Everolimus coadministration increased the Cmax of atorvastatin by 11% but had no influence on atorvastatin AUC. Coadministration of everolimus with pravastatin was associated with a 10% decrease in pravastatin Cmax and a 5% decrease in the AUC. The elimination half-lives of the two statins were unaffected by everolimus. Changes in total HMG-CoA reductase inhibitors in plasma exhibited generally similar patterns as for the parent statin exposures. Single-dose administrations of everolimus with either atorvastatin or pravastatin did not influence the pharmacokinetics of everolimus, atorvastatin, pravastatin, or total HMG-CoA reductase inhibitors in plasma to a clinically relevant extent.

Adult↗

PubMed2002

Effect of rifampin on apparent clearance of everolimus.

OBJECTIVE: To assess the influence of the CYP3A4 enzyme inducer rifampin on the pharmacokinetics of the immunosuppressant everolimus to provide guidance for their coadministration. METHODS: In this open-label, single-sequence, crossover study, 12 healthy subjects received a single oral 4-mg dose of everolimus alone and again after an 8-day pretreatment with rifampin 600 mg/d. Urinary excretion of 6beta-hydroxycortisol was measured at various time points during rifampin treatment as a marker of CYP3A4 induction. RESULTS: Urine excretion of 6beta-hydroxycortisol was significantly elevated during treatment with rifampin compared with prestudy, indicating enzyme induction. When everolimus was coadministered during rifampin treatment, the apparent clearance of everolimus was significantly increased, on average by 172%. This was manifested as a decrease in maximum concentration in all subjects, on average by 58% (range 14-73%). The AUC remained unaffected in 1 subject (although 6beta-hydroxycortisol indicated enzyme induction) and decreased in the other 11 subjects. The average decrease in AUC in the full study population was 63% (range 0-82%). Everolimus half-life was reduced significantly, from an average of 32 hours to 24 hours. CONCLUSIONS: In everolimus-treated patients for whom rifampin is indicated, alternative agents with less enzyme induction potential than rifampin could be considered. Alternatively, the dose of everolimus could be individually titrated based on everolimus therapeutic drug monitoring during rifampin therapy.

Adult↗

PubMed2002

Effect of food on everolimus absorption: quantification in healthy subjects and a confirmatory screening in patients with renal transplants.

STUDY OBJECTIVE: To quantify the influence of a high-fat meal on the oral bioavailability of the immunosuppressant everolimus in a single-dose study in healthy subjects and to confirm the results in a small food-effect screening assessment in patients with renal transplants who were receiving multiple-dose everolimus. DESIGN: Randomized, open-label, crossover, single-dose study and confirmatory screening. SETTING: Phase 1 unit for the single-dose study and two German hospitals for the patient screening. SUBJECTS: Twenty-four healthy male volunteers; six clinically stable patients with renal transplants who were originally part of a phase I dose-escalation study. INTERVENTION: The 24 healthy men received everolimus 2 mg orally under fasting conditions and after a high-fat meal. The six patients received everolimus 2.5 mg/day orally, in addition to cyclosporine and prednisone. On two occasions, a pharmacokinetic profile was obtained over the dosing interval after drug administration under fasting conditions and after a high-fat meal in a randomized sequence. MEASUREMENTS AND MAIN RESULTS: In the single-dose study in healthy subjects, a high-fat meal delayed everolimus time to maximum concentration (Tmax) by a median 1.25 hours, reduced peak blood concentration (Cmax) by 60%, and reduced area under the concentration-time curve (AUC) by 16%. In the multiple-dose screening in patients with renal transplants, a high-fat meal delayed Tmax by a median 1.75 hours and reduced Cmax by 53% and AUC by 21%. Everolimus trough levels showed no food effect, whereas the peak-trough fluctuation was dampened by 52%. CONCLUSIONS: A high-fat meal modestly reduced everolimus AUC. To minimize longitudinal variability in exposure, everolimus should be administered consistently either with food or without food.

Administration, Oral↗