Validated chiral liquid chromatographic method for the enantiomeric separation of Pramipexole dihydrochloride monohydrate

(S)-Pramipexole and Its Enantiomer, Dexpramipexole: A New Chemoenzymatic Synthesis and Crystallographic Investigation of Key Enantiomeric Intermediates

A new chemoenzymatic method has been developed for the synthesis of (S)- and (R)-N-(6-hydroxy-4,5,6,7-tetrahydrobenzo[d]thiazol-2-yl) acetamide, two key synthons for the preparation of (S)-pramipexole, an anti-Parkinson drug, and its enantiomer dexpramipexole, which is currently under investigation for the treatment of eosinophil-associated disorders. These two building blocks have been obtained in good yields and high enantiomeric excess (30% and >98% ee for the R-enantiomer, and 31% and >99% ee for the S- one) through a careful optimization of the reaction conditions, starting from the corresponding racemic mixture and using two consecutive irreversible transesterifications, catalyzed by Candida antarctica lipase type A. Single crystal X-ray analysis has been carried out to unambiguously define the stereochemistry of the two enantiomers, and to explore in depth their three-dimensional features.

Design of selective molecularly imprinted sorbent for the optimized solid-phase extraction of S-pramipexole from the model multicomponent sample of human urine

The objective of this article was to design the selective molecularly imprinted sorbent dedicated to the solid-phase extraction of S-pramipexole from the complex matrix such as human urine. For that purpose, S-2,6-diamino-4,5,6,7-tetrahydrobenzothiazole was used as the template acting as the structural analog of S-pramipexole and five various monomers were employed in the presence of ethylene glycol dimethacrylate to produce molecularly imprinted polymers. The binding capabilities of resulted polymers revealed that the highest imprinting effect was noted for polymer prepared from the itaconic acid. The comprehensive analysis of morphology and the characterization of binding sites showed not only negligible differences in the extension of surfaces of imprinted and nonimprinted polymers but also higher heterogeneity of binding sites in the imprinted material. Comprehensive optimization of the molecularly imprinted solid-phase extraction allowed to select the most appropriate solvents for loading, washing, and elution steps. Subsequent optimization of mass of sorbent and volumes of solvents allowed to achieve satisfactory total recoveries of S-pramipexole from the model multicomponent real sample of human urine that equals to 91.8 ± 3.2% for imprinted sorbent with comparison to only 37.1 ± 1.1% for Oasis MCX.

Development and validation of a highly sensitive gradient chiral separation of pramipexole in human plasma by LC–MS/MS

Aim: Development of a high-sensitivity chiral LC–MS/MS method was required to evaluate a combination of pramipexole (S-PPX) and its enantiomer dexpramipexole (R-PPX) in a proposed clinical trial. The previously available methods suffered from low sensitivity for the (S)-enantiomer in the presence of the more abundant (R)-enantiomer. Based on the projected dosing regimen in the clinical trial, a 5000-fold improvement in sensitivity was required for the (S)-enantiomer. Methodology: Spiked human plasma samples were extracted by liquid–liquid extraction using ethyl acetate and injected onto a CHIRALPAK ID column under pH gradient conditions. Conclusion: An improved analytical method was developed and validated with a final LLQ for (S)-PPX of 0.1 ng/ml in the presence of 2000 ng/ml of (R)-PPX.

Development of a Validated LC Method for Separation of Process-Related Impurities Including the R-Enantiomer of S-Pramipexole on Polysaccharide Chiral Stationary Phases

Despite the availability of a few methods for individual separation of S-pramipexole from its process-related impurities, no common liquid chromatography (LC) method is reported so far in the literature. The present article describes the development of a single-run LC method for simultaneous determination of S-pramipexole and its enantiomeric and process-related impurities on a Chiralpak AD-H (150 x 4.6 mm, 5μm) column using n-hexane/ethanol/n-butylamine (75:25:0.1 v/v/v) as a mobile phase in an isocratic mode of elution at a flow rate of 1.2 ml/min at 30°C. The chromatographic eluents were monitored at a wavelength of 260 nm using a photodiode array detector. Excellent enantioseparation with good resolutions (Rs ≥ 2.88) and peak shapes (As ≤ 1.21) for all analytes was achieved. The proposed method was validated according to International Conference Harmonization (ICH) guidelines in terms of accuracy, precision, sensitivity, and linearity. Limits of quantification of impurities (0.25-0.55 μg/ml) indicate the highest sensitivity achievable by the proposed method. The method has an advantage of selectivity and suitability for routine determination of not only chiral impurity but also all possible related substances in active pharmaceutical ingredients of S-pramipexole.

Decellularization and cell seeding of whole liver biologic scaffolds composed of extracellular matrix

The definitive treatment for patients with end-stage liver disease is orthotropic transplantation. However, this option is limited by the disparity between the number of patients needing transplantation and the number of available livers. This issue is becoming more severe as the population ages and as the number of new cases of end-stage liver failure increases. Patients fortunate enough to receive a transplant are required to receive immunosuppressive therapy and must live with the associated morbidity. Whole organ engineering of the liver may offer a solution to this liver donor shortfall. It has been shown that perfusion decellularization of a whole allogeneic or xenogeneic liver generates a three-dimensional ECM scaffold with intact macro and micro architecture of the native liver. A decellularized liver provides an ideal transplantable scaffold with all the necessary ultrastructure and signaling cues for cell attachment, differentiation, vascularization, and function. In this review, an overview of complementary strategies for creating functional liver grafts suitable for transplantation is provided. Early milestones have been met by combining stem and progenitor cells with increasingly complex scaffold materials and culture conditions.

LC-MS/MS determination of pramipexole on rat dried blood spots: a pharmacokinetic study

A simple and selective liquid chromatography-tandem mass spectrometric method for determination of pramipexole on rat dried blood spots was developed and validated. Chromatographic separation was achieved on a Synergy polar-RP column using 10mM ammonium acetate and methanol (50:50, v/v) as mobile phase in an isocratic mode of elution at a flow rate of 1.0mL/min. LC-MS was performed in a positive ion electro spray ionization mode and the MS/MS ion transitions 212.10→153.03 for PRX and 198.10→153.03 for internal standard (2-amino-4,5,6,7-tetrahydro-6-ethyl-amino-benzthiazole) were monitored. The developed method exhibited a linear dynamic range over 100-5000pg/mL for PRX on dried blood spots. The overall extraction recovery of PRX from DBS was 96.7%. The intra- and inter-day accuracy and precision were within the pre-defined limits of ≤15% at all concentrations. Influence of hematocrit and spot volume on dried blood spot was also evaluated and found to be well within the acceptable limits. The method was successfully applied to pharmacokinetic studies of PRX in rats.

Establishment of inherent stability of pramipexole and development of validated stability indicating LC-UV and LC-MS method

Pramipexole belongs to a class of nonergot dopamine agonist recently approved for the treatment of early and advanced Parkinson's disease. A validated specific stability indicating reversed-phase liquid chromatographic method has been developed for the quantitative determination of pramipexole in bulk as well as in pharmaceutical dosage forms in the presence of degradation products. Forced degradation studies were performed by exposition of drug to hydrolytic (acidic and basic), oxidative and photolytic stress conditions, as defined under ICH guideline Q1A (R2). Significant degradation was observed under hydrolytic, oxidative and photolytic conditions and the degradation products formed were identified by LC–MS.