Chapter 3. Results for quantification of Genotoxic Impurities in Sorafenib Tosylate by Ultra performance liquid chromatography

Transcription

1 Chapter 3 Results for quantification of Genotoxic Impurities in Sorafenib Tosylate by Ultra performance liquid chromatography

2 3.0 Introduction Sorafenib tosylate Chemical name: 4-[4-[[4-chloro-3-(trifluoromethyl)phenyl]carbamoylamino] carboxamide tosylate phenoxy]-n-methyl-pyridine-2- Chemical structure:.c 7 H 8 O 3 S Fig.1 Structure of Sorafenib tosylate Physical properties Molecular weight: Empirical formula: C 21 H 16 ClF 3 3N 4 O 3.C 7 H 8 O 3 S Appearance and color: White to yellowish brown powder Solubility: In soluble in water, slightly soluble in alcohol, Soluble in Dimethyl formamide and Dimethyl sulphoxide. Therapeutic category: Anticancer Agent

3 Dosage: Tablet Pharmacology: Sorafenib is a small molecular Inhibetor of several tyrosine protein kinases and Raf Kinases. Protein kinases are overactive in many of the molecular pathways that cause cells to become cancerou. These pathways include Raf kinase, PDGC, VEGF receptor 2 and 3 kinases and c Kit the receptor for Stem cell factor. Related impurities of Sorafenib tosylate are as follows O S O CH 3 O O CH 3 O S O CH 3 O S O O CH 3 H 3 C H 3 C H 3 C Methyl Tosylate Ethyl Tosylate Isopropyl tosylate Fig.2 Impurites of Sorafenib Tosylate Chemically the related impurity of Methyl tosylate (Methyl-p-toluenesulphonate), Ethyl tosylate(ethyl-p-toluenesulphonate) and Isopropyl tosylate (Isopropyl-p-toluene sulphonate) is a process impurity in Sorafenib tosylate. 3.1 LHASA predictions of Derek Nexus Report for Methyl Tosylate, Ethyl Tosylate and Isopropyl Tosylate LHASA predictions for Methyl Tosylate:

4 REASONING SUMMARY Carcinogenicity in mammal is PLAUSIBLE Chromosome damage in vitro in mammal is Plausible Mutagenicity in vitro in bacterium is Plausible Skin sensitisaiton in mammal is Plausible Tetratogenicity in mammal is plausible ALERTS FOUND 073 alkylating agent 027 alkylating agent 027 alkylating agent 414 Alkyl Sulphate or sulphonate 516 Alkyl sulphonate Table 1. LHASA predictions for Methyl Tosylate The predictions have been proved in bacterium and mammals. Alkyl sulphonate act as direct DNA alkulating agents forming nboth mono-adducts, and in the case of bifunctional sulphonates, DNA cross-links. The mechanism of reaction of sulphonates with DNA follows usually as SN2 pathway with the sulphonate moiety acting as leaving group. There is no particular embryopathy for alkyl sulphonagtes, since they directly after the DNA of the developing foetus leading to multiple and various malformation. In human, alkyl sulphonagte containg compounds such as busulfan produce primarily craniofacial (e.g microcephaly, cleft lip and palate), skeleton (e.g limb, digit defects), visceral (e.g kidney defects, hydroureter) and central nervous system anomalies. Intrauterine gowth retardation is also a common feature. Most of the reported exposures are during the first trimester. Similar malformations are observed, for the rabbit and rat, Weingarten et al, during organogenesis LHASA predictions for Ethyl Tosylate:

5 REASONING SUMMARY Carcinogenicity in mammal is PLAUSIBLE Chromosome damage in vitro in mammal is PLAUSIBLE Mutagenicity in vitro in bacterium is PLAUSIBLE Skin sensitisaiton in mammal is PLAUSIBLE Tetratogenicity in mammal is PLAUSIBLE ALERTS FOUND 073 alkylating agent 027 alkylating agent 027 alkylating agent 414 Alkyl Sulphate or sulphonate 516 Alkyl sulphonate Table 2. LHASA predictions for Ethyl Tosylate The predictions have been proved in bacterium and mammals. Carcinogenicity The alert has demonstrated the following predictive performance: CPDB data set: 81 compounds activate this alert of whrg1 61 are reported positive. ToxRefDB Data set: 9 Compounds activate this alert of whrg1 5 are reported positive. ISSCAN data set: 75 Compound activate this alert of whrg1 61 are reported positive. Marketed pharmaceutivcal data set: 8 Compound activate this alert of whrg1 7 are reported positive. Chromosome damage: in vitro chromosome aberration test Sofuni data set: 28 compounds activate this alert of whrg1 21 are reported positive.

6 FDA CFSAN data set: 99 compounds activate this alert of whrg1 28 are reported positive. Benchmark chromosome damage data set: 44 compounds activate this alert of whrg1 4 are reported positive. Marketed pharmaceuticals data set: 7 Compounds activate this alert of whrg1 4 are reported positive LHASA predictions for Isopropyl Tosylate: REASONING SUMMARY Carcinogenicity in mammal is PLAUSIBLE Chromosome damage in vitro in mammal is PLAUSIBLE Mutagenicity in vitro in bacterium is PLAUSIBLE Skin sensitisaiton in mammal is PLAUSIBLE Tetratogenicity in mammal is PLAUSIBLE ALERTS FOUND 073 alkylating agent 027 alkylating agent 027 alkylating agent 414 Alkyl Sulphate or sulphonate 516 Alkyl sulphonate Table 3. LHASA predictions for Isopropyl Tosylate

7 The predictions have been proved in bacterium and mammals. Carcinogenicity The alert has demonstrated the following predictive performance: CPDB data set: 81 compounds activate this alert of whrg1 61 are reported positive. ToxRefDB Data set: 9 Compounds activate this alert of whrg1 5 are reported positive. ISSCAN data set: 75 Compound activate this alert of whrg1 61 are reported positive. Marketed pharmaceutivcal data set: 8 Compound activate this alert of whrg1 7 are reported positive. Preparation of salt is a useful technique for optimizing the physicochemical processing (formulation), biopharmaceutics or therapeutic properties of active pharmaceutical ingredients (APIs), and sulfonate salts are widely used for this purpose (5). However sulfonic acids can react with low molecular weight alcohols such as RR2, ethanol, or isopropanol to form the corresponding sulfonate esters. In general, sulfonic acid esters are considered as potential alkylating agents that may exert genotoxic effects in bacterial and mammalian cell systems and possibly carcinogenic effects in vivo; thus, these compounds have raised safety concerns in recent times (6-7). Sorafenib, an antineoplastic agent acts as protein kinase. Sorafenib inhibits tumor cell proliferation and the tumor cell vacularisation through activating the receptor tyrosine kinase signalling RAS/RAF/MEK/ERK cascade pathway. In this work we demonstrate the practical example for the analytical control of three genotoxic impurites in Sorafenib Tosylate. These impurities Methyl Tosylate, Ethyl Tosylate, Isopropyl Tosylate and Sorafenib Tosylate were characterized and structure was deduced (Fig. 1-12). These impurities were observed to be process impurities. From the literature it was found out that these impurites are genotoxic (8-16). The method is based on Ultra performance liquid chromatography (UPLC) for determination of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. The method was validated as RG1 guidelines. (17).

8 3.2. MATERIAL AND METHODS: Drug and reagents Sorafenib Tosylate was purchased from G.M fine chemicals (Hydrabad, India). Standards of Methyl Tosylate, Ethyl Tosylate and Iso-propyl Tosylate were obtained from Sigma AldrRG1. Analytical reagent (AR) grade Sodium perchlorate was purchased from Fluka (Banglore, India), acetic acid from Merck (Mumbai, India) and RR1from sigma AldrRG1 (Mumbai, India). Water for UPLC studies was obtained from milipore water purifying system Apparatus and equipment LC was carried out on WATERS Aquity UPLC (USA) with photodiode array detector. The signal was monitored and processed using Empower 2 software. In all the studies, separations were attained on RRHD Eclipsed Plus C-18 column (50 mm x 2.1 mm i.d., particle size 1.8µm) procured from LCGC (Banglore, INDIA). A ph/ion analyzer (Labindia, made in) was used to check and adjust the ph of buffer solutions. All the instruments used were calibrated and were used within the specified dyanamic range Mobile phase preparation The mobile phase comprised of 50mM Sodium Perchlorate in water and ph- 3.0 with RR3and RR1in the volume ratio of 60: Chromatographic conditions The numbers of column chemistries like C8, Penta Fluro Phenyl, Phenyl were used during method development. The best separation was achieved on RRHD Eclipsed Plus C-18 column (50 mm x 2.1 mm i.d., particle size 1.8µm) using isocratic mixture of 50mM Sodium Perchlorate in water and ph adjusted to 3.0 with RR3and RR1in the volume ratio of 60:40 with the flow rate

9 set at 0.5ml/min. The HPLC column oven temperature was set at 40 o C. Iinjection volume 10µl and detector wavelength 226nm were set Sample preparation for method developments The diluent selected for dissolving Sorafenib Tosylate and the impurities was mobile phase. Stock solution of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate prepared in diluenting solution with concentration of 0.2mg/ml. Further 5 ml of individual impurities stock solution were shifted to a single 100ml volumetric flask and diluted up the volume with diluent. Further transferred 2 ml this solution was transferred to 100ml volumetric flask and diluted up the volume with diluent. Sorafenib Tosylate sample solutions were prepared in the concentration 15mg/ml. The concentration of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate impurities was 13 ppm w.r.s Sorafenib Sample and impurities preparation Stock solution of methyl tosylate, ethyl tosylate and iso-propyl tosylate impurities and Sorafenib was prepared in diluent. This stock solution is further diluted using diluents to achived the required concentration of impurites RESULTS AND DISCUSSION Development of HPLC method and column selection Chemical structure of Sorafenib Tosylate and Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate impurities are shown in (Fig. 1-2). The manufacturing sample of Sorafenib Tosylate was selected for method development and validation studies. Mobile phase with different composition and different stationary phases were tried for method development of Methyl Tosylate, Ethyl Tosylate and isopropyl Tosylate content in sorafenib Tosylate.. Poor peak shape and resolution was observed when Waters Acquity BEH C18 (50 x 2.1mm, 1.7µm) and mobile phase consisting of mixture of 0.1% triethylamine in water: RR1and RR2(80:10:10 v/v/v) retension time of sorafenib was 5 min with good separation, however peak shape of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate impurities was not good. By using another

10 attempt with mixture of mobile phase 0.1% Triethylamine, RR1and RR2 (75:15:10 v/v/v/) and column Waters Acquity BEH C8 (50 x 2.1mm, 1.7µm), ethyl Tosylate eluted in close proximity to iso-propyl Tosylate. The separation was achieved using Sodium perchlorate buffer and RR1in the ratio of (50:50). The concentration of buffer was optimized for better peak shape of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. Sodium perchlorate buffer with concentration of 50mM with different composition of RR1was employed. In the next approach mixture of Sodium perchlorate buffer and RR1in the ratio of (60:40 v/v/) using RRHD Eclipsed Plus C18 (50 x 2.1mm, 1.8µm) column. Under these condition Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate impurities eluted in close proximity to Sorafenib s other unknown impurities. With decrease of RR1content and increased content of buffer, the required resolution was obtained. Ref. (Fig.3) Fig. 3 Impurity Standard chromatogram of sarafenib tosylate

11 3.3.2 Method validation RV1 Specificity of the method is its ability to measure specifically and selectively the analyte present in the drug substances. Identification solution of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate were injected at working RHconcentration along with Sorafenib Tosylate 15mg/ml. A spiked sample of Sorafenib Tosylate with Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate was also injected.the peaks of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate were well resolved from each other as well as Sorafenib and its other impurities. Spectral data confirmed that the peaks were pure and there was no interference at the Rt of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. (Fig.4-6) Fig. 4 Spiked sample Chromatogram

12 Table 4: Result of System suitability Parameters Resolution between Methyl Tosylate and Ethyl Tosylate and Ethyl tosylate and Isopropyl tosylate Limit RM2 2.0 Value Methyl Tosylate 1.53 Tailing factor Ethyl Tosylate RM Isopropyl Tosylate 1.32 Fig. 5 UPLC Chromatogram for Methyl Tosylate

13 Fig. 6 UPLC Chromatogram for Ethyl Tosylate Fig. 7 UPLC Chromatogram for Isopropyl Tosylate

14 RV4 RV4 was determined by preparing and injecting solution of various concentration 0.09 ppm (RH1), 0.1 ppm (RH2), 0.15 ppm (RH3), 0.2 ppm (RH4), 0.25 ppm (RH5) and 0.3 ppm (RH6) for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. RH1 and RH6 was injected six times were as RH2, RH3, RH4 and RH5 was injected twice. Graph plotted impurity area Vs concentration. The RS1for Methyl Tosylate was , ethyl Tosylate and iso-propyl Tosylate was , whrg1 indicates good linearity. The %Y intercept for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate was found to be 2.64, and 0.37 respectively. Ref (Fig 8). Fig. 8 Linearity graph for Methyl Tosylate, Ethyl Tosylate and Isopropyl Tosylate

15 RV6 RV6 of the method was assessed by adding known amount of impurity in durg substances at different concentration at 0.09, 0.1, 0.2 and 0.3 ppm of analyte concentration 15mg/ml. Each spiked RHof Methyl Tosylate, Ethyl Tosylate and Isopropyl Tosylate solution was prepred three times and injected. Recovery of Methyl Tosylate ranged from %, %, % and %, Ethyl Tosylate ranged from %, %, % and % and Isopropyl Tosylate ranged from %, %, % and % respectively. Content are shown in Table No.1 respectively. The criteria for acceptance RHof recovery at a concentration RHof 0.09 ppm is between 85% and 115% and at 0.1, 0.2 and 0.3 ppm is 90% to 110%. (Fig. 8) Fig. 9 RV6 Chromatogram

16 Table 5 Recovery results for Methyl Tosylate Added (µg) Recovered (µg) %Recovery %RSD

17 Table 6 RV6 results of Ethyl Tosylate Added (µg) Recovered (µg) %Recovery %RSD

18 Table 7 RV6 results of Isopropyl Tosylate Added (µg) Recovered (µg) %Recovery %RSD

19 RV2 It is characteristic of limit test. The lowest concentration of analyte in sample that can be detected, but not necessarily quantitated as an exact value under the stated experimental condition. Limit for detection (S/N ratio) for any impurity is usually between 3-10 is considerally acceptable. The RL1 was found to be ppm for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. The RL1 & RL2 results are shown in the Table 8. Table 8 RL1 AND RL2 RESULTS OF IMPURITIES Compound RL1(ng/ml) S/N RL2(ng/ml) S/N %RSD Name Ratio Ratio Methyl Tosylate Ethyl Tosylate Isopropyl Tosylate Fig. 10 RV2 Chromatogram Limit of quantification

20 The Limit of Quantitation (RL2) is the lowest concentration of analyte that can be quantitatively determined with acceptable RV5 and RV6. Limit for S/N ratio was between The RL2 was determined to be 0.09 ppm for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate. The results are shown in Table 8 and Fig.11. Fig. 11 Limit of Quantification Chromatogram System and method RV5 The RV5 for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate in Sorafenib was checked by forming repeatability. The sample was prepared by spiking Sorafenib with the solution concentration of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate 0. 2 ppm and injected six times. The %R.S.D was found to be less than 1.3% for content of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate for six replicate injections. To check method RV5 by using six independent RV6 solution with limit RHconcentration of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate a concentration of 0. 2 ppm. Each limit RHRV6 solution injected once. The variation in the results for the content of Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate were calculated in terms of % R.S.D. The values was 2.8%, 1.6% and 2.2% respectively for Methyl Tosylate, ethyl Tosylate and iso-propyl Tosylate, indicating satisfactory method RV5.

21 3.4. Sample preparation of Sorafenib Tosylate for routine analysis. Transferred 150mg of Sorafenb Tosylate sample in 10ml volumetric flask, add 4ml of RR1to dissolve and dilute up the volume with buffer. Filtered this solution using 0.45µ syringe filter. Injected this solution into UPLC and check the content of impurities present in the sample. Three batches of Sorafenib Tosylate was analyzed as per developed method and results were shown in in Table 3. The chromatogram obtained after the analysis was shown in (Fig. 12). Fig. 12 Sample Chromatogram 3.5. Conclusion The analytical method used for the quantification of Genotoxic impurities, Methyl Tosylate, ethyl Tosylate and Isopropyl Tosylate present in Sorafenib is complies with acceptance criteria of RG1 guidelines. Hence the method is capable of detecting three process impurities.

22 Hence this method is useful for the detection of Potential Genotoxic impurities present in Sorafenib Tosylate. Table 9 Results of Methyl Tosylate ethyl Tosylate and isopropyl Tosylate are given below Compound name Methyl Tosylate Ethyl Tosylate Isopropyl Tosylate B.No. A O O O B.No. B O O O B.No. C O O O Fig.13 Methyl Tosylate UV spectra Fig.14 Ethyl Tosylate UV spectra

23 Fig.15 Isopropyl Tosylate UV spectra Fig. 16 Sorafenib Tosylate UV spectra Methyl Tosylate Fig. 17 Mass data for Methyl Tosylate

24 Ethyl Tosylate Fig. 18 Mass data for Ethyl Tosylate Isopropyl Tosylate Fig. 19 Mass data for Isopropyl Tosylate

25 Fig. 20 Proton NMR for Methyl Tosylate Fig. 21 Proton NMR for Ethyl Tosylate

26 Fig. 22 Proton NMR for Isopropyl Tosylate References: 1. McGovern, T. & Jacobson-Kram, D. (2006). Regulation of genotoxic and carcinogenic, Impurities in drug substances and products. Trends in Analytical Chemistry, Vol. 25, pp Dearfield, K. L., Cimino, M. C., McCarroll, N. E., Mauer, I. & Valcovic, L. R. (2002).Genotoxicity risk assessment: a proposed classification strategy. Mutation Research -Genetic Toxicology and Environmental Mutagenesis, Vol. 521, pp Robinson, D. I. (2010). Control of genotoxic impurities in active pharmaceutical 4. ingredients:a review and perspective. Organic Process Research and Development, Vol.14, pp Ashby, J. (1990). Determination of the genotoxic status of a chemical. Mutation Research,Vol.248, pp Elder, D. P. & Snodin, D. J. (2009). Drug substances presented as sulfonic acid salts:overview of utility, safety and regulation. Journal of Pharmacy and Pharmacology,Vol.61, pp

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28 15. CHMP Safety Working Party, EMA/CHMP/SWP/431994/ Anthony J. DeStefano, ppt:/ Genotoxic Impurity-US and European Regulatory Perspective, 6-7, Guidance on genotoxicity testing and data interpretation for pharmaceuticals intended for human use, S2 (R1) 18. Validation of analytical procedure, Text and methodology Q2 (R1).