Abstract
N-[4-[[(2,4-diamino-6-pterdinyl)methyl]amino]benzoyl]-l/d-glutamic acid (l/d-AMT) is an investigational drug in phase 1 clinical development that consists of the l-and d-enantiomers of aminopterin (AMT). l/d-AMT is obtained from a novel process for making the l-enantiomer (l-AMT), a potent oral anti-inflammatory agent. The purpose of these studies was to characterize oral uptake and safety in the dog and human of each enantiomer alone and in combination and provide in vitro evidence for a mechanism of intestinal absorption. This is the first report of l /d-AMT in humans. In dogs (n = 40) orally dosed with l-AMT or d-AMT absorption was stereoselective for the l-enantiomer (6- to 12-fold larger peak plasma concentration after oral administration and area under the plasma concentration-time curve at 0–4 h; p < 0.001). d-AMT was not toxic at the maximal dose tested (82.5 mg/kg), which was 100-fold larger than the maximal nonlethal l-AMT dose (0.8 mg/kg). Dogs (n = 10) and humans with psoriasis (n = 21) orally administered l-AMT and l /d-AMT at the same l-enantiomer dose resulted in stereoselective absorption (absent d-enantiomer in plasma), bioequivalent l-enantiomer pharmacokinetics, and equivalent safety. Thus, the d-enantiomer in l/d-AMT did not perturb l-enantiomer absorption or alter the safety of l-AMT. In vitro uptake by the human proton-coupled folate transporter (PCFT) demonstrated minimal transport of d-AMT compared with l-AMT, mirroring the in vivo findings. Enantiomer selectivity by PCFT was attributable almost entirely to decreased binding affinity rather than changes in transport rate. Collectively, our results demonstrate a strong in vitro-in vivo correlation implicating stereoselective transport by PCFT as the mechanism underlying stereoselective absorption observed in vivo.
Footnotes
This work was supported in part by Syntrix Biosystems; the National Institutes of Health National Institute of Arthritis, Musculoskeletal, and Skin [Grant 1R43AR056547]; the National Institutes of Health National Institute of Allergy and Infectious Diseases [Grant 1R43AI68282]; and the National Institutes of Health National Cancer Institute [Grants 1R01CA53535, 1R01CA152316].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
ABBREVIATIONS:
- AMT
- aminopterin
- AE
- adverse event
- AUC
- area under the plasma concentration-time curve
- CHO
- Chinese hamster ovary
- CI
- confidence interval
- CL
- clearance
- Cmax
- peak plasma concentration after oral administration
- compound 1
- 2-({5-[4-(2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]pyrimidin-6-yl)-butyl]-thiophen-2-carbonyl}-amino)-pentanedioic acid
- CV
- coefficient of variation
- DMSO
- dimethyl sulfoxide
- DPBS
- Dulbecco's phosphate-buffered saline
- GFR
- glomerular filtration rate
- Kt
- whole-cell Michaelis constant
- LC-MS/MS
- liquid chromatography/tandem mass spectrometry
- l/d-AMT
- N-[4-[[(2,4-diamino-6-pterdinyl)methyl]amino]benzoyl]-l/d-glutamic acid
- ld-AMT-d3
- deuterated ld-AMT-α,γ,γ-d3
- MES
- 4-morpholineethanesulfonic acid
- MTX
- methotrexate
- NA
- no addition
- PCFT
- proton-coupled folate transporter
- PMX
- pemetrexed
- PT523
- Nα-(4-amino-4-deoxypteroyl)-Nδ-hemipththaloyl-l-ornithine
- QC
- quality control
- SAE
- serious adverse event
- Tmax
- time to Cmax
- VD
- apparent volume of distribution.
- Received April 12, 2012.
- Accepted May 30, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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