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DruQuaR Related impurities profile and in silico toxicity potential of the anti-malarial drug lumefantrine Sultan Suleman1, Bram Baert1, Elien Vangheluwe1, Mathieu Verbeken1, Luc Duchateau2, Bart De Spiegeleer1,* 1 Drug Quality and Registration (DruQuaR) group, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium. 2 Department of Physiology and Biometrics, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium. * Corresponding author: [email protected] (O. Ref.: 2010-282c) INTRODUCTION The investigation of related impurities is one of the most critical issues in drug development. The analytical evaluation of these impurities, including the rational specification settings, is required to guide production process and storage conditions. Due to their possible safety impact for the patient, regulators and authorities are very strict on this quality aspect. Thus, we investigated the related impurities in the anti-malarial drug lumefantrine, since no exhaustive impurity profile has been established up till now. Lumefantrine (syn. benflumetol) is a fluorene derivative belonging to the aryl amino alcohol class of anti-malarial drugs (Figure 1). The compound possesses marked blood schizontocidal activity against a wide range of plasmodia. Biochemical studies suggest that its anti-malarial effect involves lysosomal trapping of the drug in the food vacuole of the intra-erythrocytic parasite, followed by binding to haem that is produced in the course of haemoglobin digestion. This binding prevents the polymerization of haem into haemozoin, hence inhibiting the detoxification of haem. Lumefantrine is commercially available in fixed combination products Figure 1: Structure of with artemether. Lumefantrine OBJECTIVES To establish an exhaustive impurity profile and associated toxicity potential of the anti-malarial drug, lumefantrine. Materials and methods HPLC-UV-(DAD)-ESI/ion-trap-MS impurity profiling of retain and stability samples of API’s and different marketed FPP containing lumefantrine was performed: reversed phase RP-18 HPLC column (Merck Purospher, 150 × 4.6 mm, 5 µm with guard column) at 30 °C; mobile phase (ammonium acetate buffer and acetonitrile). UV detection and quantification was performed at 266 nm, with reporting threshold of 0.1%. ESI-ion trap MS detection was used for identification purposes. Toxicity potential of the related impurities versus lumefantrine was assessed in silico using Toxtree and Derek. RESULTS and DISCUSSION Impurity profiling: Next to the related compounds which are compendially specified in USP Salmous / Ph. Int., we found two new impurities which occur as potential degradants. Cl A. Compendial related impurities (USP Salmous, Ph.Int.) Cl (RS, Z)-2-(Dibutylamino)-2-(2,7dichloro-9-(4-chlorobenzylidene)9H-fluoren-4-yl)ethanol; isomeric compound [C30H32Cl3NO, 528.94] USP specification limit: 0.1% OH N Cl Cl Cl (1S,3R,5R)-1,3-bis((EZ)-2,7Dichloro-9-(4chlorobenzylidene)-9H-fluoren-4yl)-2,6-dioxabicyclo[3.1.0]hexane [C44H24Cl6O2, 797.39] USP specification limit: 0.1% Cl Cl Cl O Cl O Cl Cl Cl O O Cl Cl 2-((EZ)-2,6-Dichloro-9- (4chlorobenzylidene)-9H-fluoren4-yl)-3’-((EZ)-2,7-dichloro-9-(4chlorobenzylidene)-9H-fluoren4-yl)-2,2’-bioxirane [C44H24Cl6O2, 797.39] USP specification limit: 0.3% Cl 1. Impurity A [USP Salmous/Ph. Int (DS)] 2. Impurity BA (USP)/Impurity B (Ph. Int) 3. Impurity BB (USP)/Impurity C (Ph. Int) B. New related impurities Name and structure 1. N-oxide of lumefantrine [C30H32NO2Cl3; 544.16] MS spectrum Cl Conditions & max. concentrations • Oxidative stress of FPP [T2d 60°c / 1% H2O2 ]: 0.86% • In retain/stability samples: 0.12% RRT: 0.19 (N-oxide of Lumefantrine) RRT: 1.00 (Lumefantrine) Cl Cl + N O OH - RRT: 0.33 (DBK) 2. Desbenzylketo derivative (DBK) [C23H27NO2Cl2, 420.37] N HO Cl • Oxidative stress of FPP [T2d 60°c / 1% H2O2 ]: 1.49% • Acidic stress of FPP [T3d 50°c / 1 M HCl]: 4.26% [T6m 40°C / 75% RH]: 0.34% • In retain/stability samples: 0.26% Cl Figure 2: Typical UV chromatogram of lumefantrine and its two degradation impurities (Noxide and Desbenzyl keto derivatives) O In silico toxicity: Comparison of the in silico toxicity profile of lumefantrine versus both new related impurities showed no significant difference, except a plausible photo-toxicity/allergenicity for DBK. For these two degradants, Derek did not indicate any mutagenicity or carcinogenicity concern. CONCLUSIONS Using HPLC-UV/ESI-ion trap MS, we have established for the first time an exhaustive impurity profile of lumefantrine, with two new impurities identified (Noxide of lumefantrine and desbenzylketo derivative of lumefantrine). These two new possible degradants did not elicit a major toxicity warning. REFERENCES [1] USP 2009 [2] International Pharmacopoeia 6.0, 186/2008. [3] Suleman, Baert, De Spiegeleer, et al. New degradants in lumefantrine finished drug products as specified impurities (manuscript under preparation). This is PhD work done in the context of the IUC-JU project . Contacts: PhD: [email protected]; Supervisor: [email protected]