Publications by authors named "Peter Romeis"

3 Publications

  • Page 1 of 1

1,25-Dihydroxyvitamin D3-glycoside of herbal origin exhibits delayed release pharmacokinetics when compared to its synthetic counterpart.

J Steroid Biochem Mol Biol 2013 Jul 26;136:333-6. Epub 2012 Sep 26.

Herbonis AG, Gellertstrasse 33, CH-4001 Basel, Switzerland.

Vitamin D requires two metabolic steps to become biologically active. In a first step 25-hydroxyvitamin D3 is formed, which acts as storage form. After a tightly controlled step in kidney the active metabolite 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is formed. Because kidney is the relevant metabolic organ for this conversion, 1,25(OH)2D3 needs to be supplemented in patients with kidney malfunction or kidney failure. Synthetic 1,25(OH)2D3 (calcitriol) has been available as a drug for decades. Due to its high potency and its kinetic profile (fast absorption and rapid elimination) its therapeutic windows has proven to be relatively narrow. A natural form of the active metabolite was identified in a few plants, such as Solanum glaucophyllum (SG) and suggested as alternative for animal and human health. An extract of a SG variety bred for high and uniform level of glycosylated 1,25(OH)2D3 was chemically characterized. Among the typical pharmaceutically inactive plant components (carbohydrates 54.3%, protein 24.9%, minerals 17.1% and water 4.1%) high levels of 1,25(OH)2D3 and a unique flavonoid content was found (1.11mg total quercetin/g extract) consisting exclusively of the quercetin glycosides hyperoside, isoquercetin, rutin and apinosylrutin. The molecular distribution of glycosyl moieties in 1,25(OH)2D3 extracted from SG as determined by gel permeation chromatography was found to be 1-10 hexose units per aglycone. 1,25(OH)2D3-1-β-glucopyranoside was identified in the SG extract, while a di- and triglycoside have been identified in SG by other groups. The pharmacokinetic properties of synthetic 1,25(OH)2D3 and glycosylated 1,25(OH)2D3 extracted from SG were compared in male rats. When compared to synthetic 1,25(OH)2D3, SG-derived 1,25(OH)2D3 exhibited delayed absorption and elimination characteristics, resulting in delayed Tmax (6-12h vs. 1h) and increased T½ (approximately 30h vs. 23h). This putative modified release pattern may be attributed to the glycosylation of herbal 1,25(OH)2D3 because de-glycosylation by ubiquitous intestinal enzymes prior to intestinal uptake of the aglycone appears to be the rate limiting step. In effect, 1,25(OH)2D3 of herbal origin behaves like a precursor of calcitriol, resulting in a wider therapeutic window and thus better pharmacological tolerance. This article is part of a Special Issue entitled 'Vitamin D Workshop.'.
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July 2013

Quantitative analysis of D-24851, a novel anticancer agent, in human plasma and urine by liquid chromatography coupled with tandem mass spectrometry.

Rapid Commun Mass Spectrom 2004 ;18(13):1465-71

Department of Pharmacy and Pharmacology, Slotervaart Hospital/The Netherlands Cancer Institute, Louwesweg 6, 1066 EC Amsterdam, The Netherlands.

The development of a liquid chromatography/tandem mass spectrometric assay for the quantitative analysis of the novel tubulin inhibitor D-24851 in human plasma and urine is described. D-24851 and the deuterated internal standard were extracted from 250 microL of plasma or urine using hexane/ether (1:1, v/v). Subsequently, 10-microL aliquots of reconstituted extracts were injected onto an Inertsil ODS analytical column (50 x 2.0 mm i.d., 5 microm particle size). An eluent consisting of methanol/5 mM ammonium acetate, 0.004% formic acid in water (80:20, v/v) was pumped at a flow rate of 0.2 mL/min. An API 365 triple quadrupole mass spectrometer was used in the multiple reaction monitoring mode for sensitive detection. For human plasma a dynamic range of 1-1000 ng/mL was validated, and for human urine a range of 0.25-50 ng/mL. Validation was performed according to the most recent FDA guidelines and all results were within requirements. The assay has been successfully applied to support a phase I clinical trial with orally administered D-24851.
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September 2004

Crossover randomized comparison of intravenous versus intravenous/oral mesna in soft tissue sarcoma treated with high-dose ifosfamide.

Clin Cancer Res 2003 Dec;9(16 Pt 1):5829-34

Division of Hematology/Oncology, University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 48109-0948, USA.

Purpose: We conducted our study to determine the pharmacokinetics (PK) and clinical efficacy of oral mesna in patients receiving ifosfamide for soft tissue sarcoma.

Experimental Design: Seventeen patients were enrolled in a randomized prospective Phase I/II study. Seventeen patients were exposed to study medication. Ifosfamide was given at a dose of 2 g/m2/day for 5 days on a 21-day cycle. Before the first cycle, all patients were randomized onto a crossover design and received either the approved i.v. or i.v./oral mesna regimen, with crossover for the second cycle of chemotherapy. The i.v. mesna regimen consisted of dosings (20% ifosfamide dose) at 0, 4, and 8 h. The i.v./oral arm consisted of an i.v. mesna dosing (20% ifosfamide dose) at 0 h, followed by oral tablet dosing (40% ifosfamide dose) at 2 and 6 h. In-patient clinical monitoring and phlebotomy and urine sampling for mesna, dimesna, and ifosfamide PK were performed on all chemotherapy days.

Results: Thirteen patients were evaluable for PK and 17 for efficacy and toxicity. No significant differences were detected in the plasma PK of the concomitantly infused ifosfamide. Rates of hemorrhagic cystitis were similar across mesna schedules. Four of 10 evaluable patients demonstrated objective response.

Conclusion: On the basis of our study, an i.v./oral mesna regimen is at least as uroprotective as the approved i.v. regimen. The i.v./oral regimen will improve patient tolerance and convenience, allow for a reduction in elective hospitalizations for ifosfamide chemotherapy, reduce the potential morbidity associated with inpatient administration of chemotherapy, and likely result in decreased costs of care.
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December 2003