RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4,

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1 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, SPECIAL GUEST EDITOR SECTION Separation and Quantitation of Alkylphosphocholines and Analogues of Different Liposome Formulations by HPTLC HANNELORE RATZ, HORST SCHNELL, and MATTHIAS RISCHER ASTA Medica AG, Department Pharmaceutical Development, Weismüllerstr. 45, D Frankfurt, Germany HANS-JÖRG EIBL Max-Planck-Institute für Biophysical Chemistry, Department of Phospholipids, No. 145, Am Faßberg 11, D Göttingen, Germany High-performance thin-layer chromatographic (HPTLC) analysis of non UV-active phospholipids in biological matrixes is a common method for separation, detection, and quantitation. Liposomes containing new alkylphosphocholines and analogues with enhanced cytostatic activity had been prepared. The liposomal formulations were designed to enable the intravenous application of the alkylphosphocholines and analogues and to reduce dose-limiting toxicities observed after oral administration. For quality control the liposomes were analyzed by HPTLC for content of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), cholesterol, alkylphosphocholines, and analogues and their related compounds (main degradation products). Due to the differences in lipophily of the compounds, different mobile phases were necessary to achieve separation. Automated Multiple Development was used to reduce the number of plates and to improve the selectivity and the capacity of the chromatographic system to separate the described alkylphosphocholines and analogues from DPPG and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in one chromatographic system. The development of new active ingredients for the treatment of cancer is one of the challenges of the research and development laboratories in the pharmaceutical industry worldwide. Alkylphosphocholines and analogues with a new mode of action have been discovered by Eibl and Unger (1). Miltefosine (Miltex ), one of the compounds, showed excellent results in the topical, palliative treatment of cutaneous breast cancer metastasis. After oral application, however, gastrointestinal side effects were dose limiting (2). Thus, 2 new alkylphosphocholine analogues, Perifosine and D-21805, had been developed with a better intestinal tolerability after oral application. Liposomal formulations of alkylphosphocholines and analogues were designed to enable their intravenous application Guest edited as a special report on Planar Chromatographic Procedures in Pharmaceutical Analysis by Bernd Renger. and to reduce dose-limiting toxicities observed after oral administration (3). Small unilamellar vesicles containing Miltefosine or Perifosine, cholesterol, and 1,2-dipalmitoyl-snglycero-3-phosphoglycerol (DPPG sodium) were prepared. The alkylphosphocholines and analogues are included in the lipid bilayer of the liposomes. In contrast to lecithin-like phospholipids, alkylphosphocholines and analogues are amphiphilic single-chain molecules, which in water spontaneously form micelles instead of lipid bilayers. By addition of cholesterol, which increases the surface requirement of the nonpolar region of lipid mixtures, the described alkylphosphocholines and analogues can form bilayers and even stable liposomes in the presence of negatively charged phospholipids or negatively charged lipids (3). The chemical structures of the developed new alkylphosphocholines and analogues as inner salts are given in Figure 1. Due to the lack of UV absorbance of saturated phospholipids, high-perfromance liquid chromatographic (HPLC) analysis is difficult and can only be performed at low wavelengths (about 200 nm) because of matrix absorbance problems and baseline noise (4 7) or with special detectors, e.g., light scattering detector (8). Phospholipids like DPPG-sodium or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are widely used as emulsifying additives and just recently an HPLC method for separation of 5 phospholipids [DPPG, 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA), DPPC, 1,2-dicaproyl-sn-glycero-3-phosphocholine (DCPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-n-[poly (ethylene glycol)] (DPPE-PEG)] using SFC has been reported (9). Phospholipids like DPPG or DPPC are also used in the preparation of liposomes. The detection of Miltefosine in the presence of those phospholipids is very difficult with HPLC and it may require the development of several HPLC methods to detect all the compounds. Thin-layer chromatography (TLC) is a common method to separate and detect different types of the described new class of alkylphosphocholines and analogues in biological matrixes (10). Special detection reagents like molybdato phosphate or copper sulphate are needed to achieve a low detection limit of the compounds (11). The chemical structures of DPPG, DPPC, and cholesterol are given in Figure 2.

2 1278 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, 2001 Figure 1. Chemical structures of Perifosine, Miltefosine, and D Figure 2. Chemical structures of cholesterol, DPPC, and DPPG-sodium. During the late stage of clinical trial development of Miltefosine, an HPTLC method was developed for analysis of liposomes contaning Miltefosine. Knowing the exact conditions and composition of the liposomes, the HPTLC method was used to analyze the content of Miltefosine, DPPG, and cholesterol. Because loading of the liposome vesicles with the corresponding alkylphosphocholines and analogues depends strongly on the exact reproduction of the vesicle preparation, the method was useful for optimizing the preparation. Due to differences in lipophily and polarity of the liposome ingredients, 3 different mobile phases were developed for analysis. The use of an ion-pair reagent (sodium acetate) in the mobile phase was necessary to separate Miltefosine from DPPG and cholesterol. Saccharose was detected at the start (R f was about 0) and was therefore separated well in all 3 chromatographic systems. The content of Miltefosine, DPPG, and cholesterol was analyzed with a data-pair technique against standards of these compounds applied on the same plate. Detection was achieved by dipping the plates in a solution of copper sulphate in phosphoric acid and subsequent scanning at 500 nm (11). The mean of 5 measurements were used for calculation of the content and compared with the weight-in of the compounds (recovery calculation). The method developed for the analysis of liposomes containing Miltefosine was later applied to the analysis of liposomes containing Perifosine. To reduce time and chromatographic systems for complete analysis of liposomes, Automated Multiple Development (AMD) was investigated. AMD seemed to be suitable for separating and identifying different alkylphosphocholines and analogues like Miltefosine or Perifosine and DPPG from DPPC in one run. In a second approach, the AMD system was used to develop a method to separate the main degradation products of these new compounds from the matrix compounds of the liposomes. Figure 3 shows a typical degradation pathway of Perifosine leading to the formation of 1-octadecanol. Experimental All solvents and reagents were purchased from Merck (Darmstadt, Germany) and were of chromatography grade. Miltefosine, Perifosine, and D were prepared by our own research group. DPPG-sodium, DPPC, and cholesterol were purchased from Genzyme Pharmaceuticals (Liestal, Switzerland). The liposomes were prepared in the Department

3 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, Figure 3. Degradation pathway of Perifosine. of Phospholipids of the Max-Planck Institut for Biophysical Chemistry, Göttingen, Germany. Chromatography was performed on silica gel 60 F 254 HPTLC plates from Merck. Samples were applied on the plate with an ATS III unit from Camag (Muttenz, Switzerland). Plates were scanned with a Scanner II or III from Camag and were developed in single-trough chambers without previous saturation. The content of one vial of freeze-dried liposomes (ca 500 mg) was rehydrated in 2 ml water, shaken until the suspension was homogenous, and made up to 20 ml with methanol dichloromethane (1 + 1). The solution was diluted to give adequate concentrations for analysis of the active alkylphosphocholine or analogues, cholesterol, and DPPG-sodium (3 different solutions). In parallel, a reference solution containing the corresponding alkylphosphocholine or analogue, cholesterol, DPPG-sodium, and saccharose was prepared and diluted to nearly the same concentration (3 reference solutions). The preparation of different test and reference solutions was necessary due to the different amounts of ingredients included in the liposomes. Liposomes with high concentrations of alkylphosphocholine or analogues were dissolved in methanol, made up to 100 ml, and diluted to adequate concentrations with methanol dichloromethane (1 + 1). The test solutions (1 µl) and reference solutions (1 µl) were applied on the plates as a spot using the data-pair technique. Each test solution was applied 5 times on the plate. The plates were developed in different mobile phases: Mobile phase 20 for analysis of cholesterol. Chloroform. Mobile phase 86a for analysis of DPPG-sodium. Chloroform methanol 25% ammonia ( , v/v/v). Mobile phase 89b for analysis of Miltefosine and Perifosine. Chloroform methanol sodium acetate 1 mol/l in 25% ammonia ( , v/v/v). The plates were developed over 6 cm migration distance. After drying and cooling, the plates were dipped into a copper(ii) sulphate solution (10 g copper sulphate dissolved, in 100 ml 8% phosphoric acid) for a few seconds. After dipping, the plates were heated to 180 C for ca 20 min. The brown spots which appeared on a light blue background were scanned at 500 nm from the back side of the plate. The mean of 5 values for each compound was used for calculation against the values of the reference spots. For recovery determination, the results were compared with the theoretical content of the compounds. For AMD, 2 gradient systems were developed (for details, see Results and Discussion). Concentration of the compounds (saccharose was not included in the system because it did not Table 1. Recovery rates of Miltefosine, DPPG-sodium, and cholesterol in a liposome batch (30 Mol Miltefosine/g liposome) using the described isocratic HPTLC method Compound Recovery in 2 vials, % RSD, % Miltefosine 96.0/ /3.7 DPPG-sodium 94.8/ /3.1 Cholesterol 99.4/ /1.5 Table 2. R f values of Miltefosine, DPPG-sodium, cholesterol, and saccharose in the different chromatographic systems Compound MP 20 MP 86a MP 89b Miltefosine DPPG-sodium Cholesterol Saccharose

4 1280 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, 2001 Table 3. Loading of Miltefosine, Perifosine, DPPG-sodium, and cholesterol in 1 g liposome (high loading liposomes) using the described isocratic HPTLC system Compound Loading (µmol/g lip.) RSD, % Miltefosine DPPG-sodium Cholesterol Perifosine DPPG-sodium Cholesterol migrate and did not influence spot shape or retention time of the compounds) was calculated based on the amounts of the ingredients present in the liposomes. Preparation of the solutions and application was perfomed as described above. Results and Discussion The analysis of the first batch of liposomes containing the alkylphosphocholine Miltefosine did not lead to acceptable results, with a recovery of DPPG-sodium and cholesterol of about 80%. Because of the centrifugation step before lyophilization, it can be assumed that some of the material was lost during the centrifugation step. Thus, for the next batch, preparation of liposomes was slightly modified. The recovery rates of the compounds are summarized in Table 1. The results showed that the modification of the preparation had a positive effect on the recovery. Recovery was determined to be above 90% for all compounds, however with deviations from vial to Figure 4. Separation of Miltefosine, Perifosine, D-21805, DPPG, and DPPC as constituents of liposomes.

5 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, Figure 5. Separation of Perifosine, 1-octadecanol, DPPG, DPPC, and cholesterol as constitutents and possible degradation compunds of liposomes.

6 1282 RATZ ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 84, NO. 4, 2001 vial. The concentration of Miltefosine was determined to be about 30 µmol/g liposome. With an RSD value below 5%, the HPTLC method gave satisfying results. Recovery experiments performed by adding certain amounts of Miltefosine, DPPG-sodium, and cholesterol to a saccharose matrix prove the good precision of the method. The R f values in the different chromatographic systems are given in Table 2. In a next step, high concentrations of Miltefosine and Perifosine (total lipid concentration = about 200 mmol in the dispersion system) was used for preparation of liposomes. Due to the high viscosity of the dispersion system, it was clear that recoveries would be below 90% and therefore only the absolute concentration of Miltefosine (µmol/g liposome) and Perifosine was determined by HPTLC as shown in Table 3. All liposomes were measured with photon correlated spectroscopy (PCS) to give a particle size <100 nm. The sligthly higher RSD values may be caused by the high concentration of matrix components in the solution, leading to little deviations during application of the samples on the plate. To improve the selectivity and capacity of the chromatographic system, 2 new AMD systems were developed with the following targets: (1) Reduction to one chromatographic system in routine analysis; (2) identification of Miltefosine, Perifosine, and D in the same system; and (3) separation of related compounds (see Figure 3). Development of the AMD system starts with the use of methyl-tert-butyl ether as the most promising solvent of choice (12). However, after a few trials it was obvious that the use of chloroform showed superior separation. As it was impossible to use ionic pair reagents like sodium acetate in mobile phase 89b due to the lack of evaporation, another problem arose. To overcome the use of ionic pair reagents, the plate was preconditioned with 25% ammonia in the first gradient steps. Methanol was used as the polar and n-hexane as the unpolar solvent. The results are given in Figures 4 and 5. The exact conditions of the gradients, drying time, pressure, and temperatures are listed below each figure. The AMD results impressively demonstrate that the reduction of 3 chromatographic systems to one chromatgraphic system is possible. Although 13 gradient steps were necessary in one AMD system, the running time of about 90 min for one plate is fortunately low. Separation of different active alkylphosphocholines and analogues (like Miltefosine, Perifosine, and D-21805) in a phospholipid containing matrix (DPPG, DPPC) is possible in one run. In addition, degradation products like 1-octadecanol are separated well from the active ingredient in Perifosine and from the matrix components. Increase of the application amount should lead to a detection of about 0.5% 1-octadecanol in the liposome matrix, which is sufficient for indicating a degradation of the corresponding alkylphosphocholine analogue during preparation of the liposomes. Our results show that isocratic HPTLC systems are suitable for quantitation of alkylphosphocholines and analogues like Miltefosine, Perifosine, or D-21805, phospholipids like DPPG, and cholesterol even in highly loaded liposomes and that the use of AMD HPTLC systems can become a more powerful tool in the analysis of those compounds in biological matrixes. Even complex mixtures of phospholipids like DPPG, DPPC, and others in biological matrixes can be resolved in single spots with this new AMD HPTLC technique. References (1) Eibl, H., & Unger, C. (1990) Cancer Treatment Reviews 17, (2) Stekar, J., Nösner, G., Kutscher, B., Engel, J., & Hilgard, P. (1995) Angew. Chem. 107, (3) Kaufmann-Kolle, P., Klenner, T., Unger, C., & Eibl, H. (1998) Drugs of Today 34, (4) Olsen, N.U., Harding, A.J., Harper, C., & Salem, Jr, N. (1996) J. Chromatogr. B 681, 213 (5) Sakamoto, A., & Novotny, M. (1996) J. Microcol. Sep. 8, 397 (6) Szücs, R., Verleysen, K., Duchateau, G., Sandra, P., & Vandeginste, B. (1996) J. Chromatogr. A 738, 25 (7) Becart, J., Chevalier, C., & Blesse, J.P. (1990) J. High Resolut. Chromatogr. 13, 126 (8) Renger, B. (1998) J. AOAC Int. 81, (9) Eckard, P.R., Taylor, L.T., & Slack, G.C. (1998) J. Chromatogr. A 826, (10) Rustenbeck, I., & Lenzen, S. (1990) J. Chrom. Biomed Appl. 90, (11) Rischer, M., Schnell, H., Greguletz, R., Wolf-Heuss, E., & Engel, J. (1997) J. Planar Chromatogr. 10, (12) Information Camag to AMD Development, Camag, Muttenz, Switzerland

TENOFOVIR TABLETS: Final text for addition to The International Pharmacopoeia (June 2010)

June 2010 TENOFOVIR TABLETS: Final text for addition to The International Pharmacopoeia (June 2010) This monograph was adopted at the Forty-fourth WHO Expert Committee on Specifications for Pharmaceutical