DESC:FIELD OF THE INVENTION:
The present invention relates to Lumacaftor and Ivacaftor impurities, process for preparation of these impurities and use of these impurities as a reference standard.

BACKGROUND OF THE INVENTION:
Lumacaftor is chemically known as 3-[6-({[1-(2,2-difluoro-1,3-benzodioxol-5-yl)cyclopropyl]carbonyl}amino)-3-methylpyridin-2-yl]benzoic acid. Its chemical structure is depicted below in formula (A). Its molecular formula is C24H18F2N2O5 and its molecular weight is 452.41.

Ivacaftor is chemically known as N-(2,4-di-tert-butyl-5-hydroxyphenyl)-l,4-dihydro-4oxoquinoline-3-carboxamide. Its molecular formula is C24H28N2O3 and its molecular weight is 392.49. Its chemical structure is depicted below in formula (B).

ORKAMBI® is a combination of lumacaftor and ivacaftor, a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator, indicated for the treatment of cystic fibrosis (CF) in patients age 6 years and older who are homozygous for the F508del mutation in the CFTR gene. ORKAMBI® is approved in US and Europe as a fixed dose combination (FDC) pink immediate-release film-coated tablet for oral administration.
It is well known in the art that, for human administration, safety considerations require the establishment, by national and international regulatory authorities, of very low limits for identified and/or unidentified, toxicologically characterized and/or uncharacterized impurities, before an active pharmaceutical ingredient (API) product is commercialized. Therefore, in the manufacture of APIs, the purity of the products, is required before commercialization, as is the purity of the active agent in the manufacture of formulated pharmaceuticals.
It is also known in the art that impurities in an API may arise from the manufacturing process, including the chemical synthesis, and degradation of the API itself, which is related to the stability of the pure API during storage. Process impurities include unreacted starting materials, chemical derivatives of impurities contained in starting materials, synthetic by-products, and degradation products.
As is known by those skilled in the art, the management of process impurities is greatly enhanced by understanding their chemical structures and synthetic pathways, and by identifying the parameters that influence the amount of impurities in the final product.
Like any synthetic compound, lumacaftor and ivacaftor can contain extraneous compounds or impurities that can come from many sources. They can be unreacted starting materials, by-products of the reaction, products of side reactions, or degradation products.

SUMMARY OF THE INVENTION:
In one embodiment, the present invention relates to lumacaftor impurities.
In another embodiment, the present invention provides method of preparing lumacaftor impurities.
In yet another embodiment, the present invention relates to ivacaftor impurities.
In yet another embodiment, the present invention provides method of preparing ivacaftor impurities.
In yet another embodiment, the present invention provides use of lumacaftor and ivacaftor impurities as a reference standard.
In yet another embodiment, the present invention provides a chromatographic method for testing the purity of a sample comprising lumacaftor or ivacaftor, salts, or solvates thereof by determining the presence of the lumacaftor impurities of formula (I)-(VIII) or ivacaftor impurities of formula (i)-(vii) respectively.
In yet another embodiment, the present invention provides a method for preparing lumacaftor or ivacaftor, salts, or solvates thereof suitable for pharmaceutical use and substantially free of the lumacaftor impurities of formula (I)-(VIII) or ivacaftor impurities of formula (i)-(vii) respectively.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 : HPLC of a standard solution of the dihydroxy impurity of Formula (I)
Figure 2 : HPLC of a standard solution of the dimer impurity of Formula (II)
Figure 3 : HPLC of a standard solution of the methyl ester impurity of Formula (III)
Figure 4 : HPLC of a standard solution of the N-oxide impurity of Formula (IV)
Figure 5 : HPLC of a standard solution of the descyclopropyl impurity of Formula (V)
Figure 6 : HPLC of a standard solution of the positional isomer impurity of Formula (VI)
Figure 7 : HPLC of a standard solution of the pentanoyl impurity of Formula (VII)
Figure 8 : HPLC of a standard solution of the PBAB acid dimer impurity of Formula (VIII)
Figure 9 : HPLC of a standard solution of the dimer impurity of formula (i)
Figure 10 : HPLC of a standard solution of the methyl ether impurity of formula (ii)
Figure 11 : HPLC of a standard solution of the nitro ester impurity of formula (iii)
Figure 12 : HPLC of a standard solution of the amino ester impurity of formula (iv)
Figure 13 : HPLC of a standard solution of the methyl carbonate impurity of formula (v)
Figure 14 : HPLC of a standard solution of the 2-hydroxy Isomer impurity of formula (vi)
Figure 15 : HPLC of a standard solution of the aniline derivative impurity of formula (vii)
Figure 16 : HPLC of a sample of lumacaftor active pharmaceutical ingredient containing the lumacaftor impurities of formula (I) to (VIII)
Figure 17 : HPLC of a sample of ivacaftor active pharmaceutical ingredient containing the ivacaftor impurities of formula (i) to (vii)

DETAILED DESCRIPTION OF THE INVENTION
Various aspects and embodiments of the present invention are described hereafter.
The term "substantially free of”, as used herein, refers to lumacaftor or ivacaftor, salts, or solvates thereof having less than 1%, preferably less than 0.5%, and the most preferably less than 0.1%, of the lumacaftor impurities of formula (I)-(VIII) or ivacaftor impurities of formula (i)-(vii) respectively. The term "substantially free of" may also include lumacaftor or ivacaftor, salts, or solvates thereof having no detectable amount of the lumacaftor impurities of formula (I)-(VIII) or ivacaftor impurities of formula (i)-(vii) respectively.
As used herein, the term "reference standard" refers to a compound that may be used both for quantitative and qualitative analysis of an active pharmaceutical ingredient such as lumacaftor or ivacaftor, salts, or solvates thereof. The reference standard may be used for identifying the different components of a mixture based on the difference in their retention time in a chromatographic method, such as in an HPLC chromatogram, Liquid Chromatography-Mass Spectrometry (LC-MS) chromatogram, or on a Thin Layer Chromatography (TLC) plate.
In the context of the present invention, the phrase "comparing the retention time" means comparing the retention time of one of the different components of a sample of lumacaftor or ivacaftor, salts, or solvates thereof which has been separated by a chromatographic technique with the retention time of lumacaftor or ivacaftor impurities respectively under the same chromatographic conditions.
In one embodiment the present invention is directed to impurities of lumacaftor and ivacaftor, which were previously unidentified, preparation of these impurities, and to the use of these impurities as reference standards for the analytical quantification of lumacaftor and ivacaftor purity respectively, as required in the manufacture of high purity lumacaftor and ivacaftor.
In another embodiment, the present invention provides impurities of lumacaftor as:
i) dihydroxy impurity: 3-(6-(1-(3,4-dihydroxyphenyl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid depicted below in formula (I),
(I)
ii) dimer impurity: N-(6-bromo-5-methylpyridin-2-yl)-3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzamide depicted below in formula (II),
(II)
iii) methyl ester impurity: methyl 3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoate depicted below in formula (III)
(III)
iv) N-oxide impurity: 2-(3-carboxyphenyl)-6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridine 1-oxide depicted below in formula (IV)
(IV)
v) descyclopropyl impurity: 3-(6-(2-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)acetamido)-3-methylpyridin-2-yl)benzoic acid depicted below in formula (V)
(V)
vi) positional isomer impurity : 3-(4-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid depicted below in formula (VI)
(VI)
vii) pentanoyl impurity: 1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)-N-(5-methyl-6-(3-pentanoylphenyl)pyridin-2-yl)cyclopropane-1-carboxamide depicted below in formula (VII)
(VII)
viii) PBAB acid dimer impurity: [1,1'-biphenyl]-3,4'-dicarboxylic acid depicted below in formula (VIII)
(VIII)

In yet another embodiment, the present invention provides impurities of ivacaftor as:
i) dimer impurity: 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate depicted below in formula (i)
(i)
ii) methyl ether impurity: N-(2,4-di-tert-butyl-5-methoxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide depicted below in formula (ii)
(ii)
iii) nitro ester impurity: 2,4-di-tert-butyl-5-nitrophenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate depicted below in formula (iii)
(iii)
iv) amino ester impurity: 5-amino-2,4-di-tert-butylphenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate depicted below in formula (iv)
(iv)
v) methyl carbonate impurity: 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl methyl carbonate depicted below in formula (v)
(v)
vi) 2-hydroxy isomer impurity: N-(3,5-di-tert-butyl-2-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide depicted below in formula (vi)
(vi)
vii) aniline derivative impurity: 4-oxo-N-phenyl-1,4-dihydroquinoline-3-carboxamide depicted below in formula (vii)
(vii)

In yet another embodiment the present invention provide the process for preparation of lumacaftor impurities of the present invention as follows.
The process for the preparation of dihydroxy impurity (I) comprising reacting lumacaftor (A) with the O-phosphoric acid (H3PO4) to yield dihydroxy impurity (I) as shown below:

The process for the preparation of dimer impurity (II) comprising reacting lumacaftor (A) with 6-bromo-5-methylpyridin-2-amine (BMPA) in presence of triethylamine (TEA), oxalyl chloride and dichloromethane (DCM) as solvent to yield dimer impurity (II) as shown below:

The process for the preparation of methyl ester impurity (III) comprising reacting lumacaftor (A) with thionyl chloride (SOCl2) in methanol (MeOH) to yield methyl ester impurity (III) as shown below:

The process for the preparation of N-oxide impurity (IV) comprising reacting lumacaftor (A) with meta-Chloroperoxybenzoic acid (mPCBA) in dichloromethane to yield N-oxide impurity (IV) as shown below:

The process for the preparation of descyclopropyl impurity (V) comprising reacting descyclopropyl cyano compound with sodium hydroxide (NaOH) in ethanol to yield descyclopropyl impurity step-I, which is reacted with oxalyl chloride in dichloromethane to yield chloro compound, this chloro compound is then reacted with 6-bromo-5-methylpyridin-2-amine (BMPA) and triethylamine in dichloromethane to form descyclopropyl impurity step-II which is reacted with (3-(tert-butoxycarbonyl)phenyl)boronic acid (PBAB ester), potassium carbonate (K2CO3) and Pd(PPh3)4 in dimethylformamide (DMF) to yield descyclopropyl impurity step-III, which is hydrolized with O-phosphoric acid in acetonitrile (ACN) to yield descyclopropyl impurity (V) as shown below:

The process for the preparation of positional isomer impurity (VI) comprising reacting 1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxylic acid (CPCA) with oxalyl chloride in dichloromethane to yield chloro compound, which is then reacted with isomer of 2-bromo-3-methylpyridin-4-amine (isomer of BMPA) and triethylamine in dichloromethane to form positional isomer impurity step-I which is reacted with (3-(tert-butoxycarbonyl)phenyl)boronic acid (PBAB ester), potassium carbonate, Pd(PPh3)4 in dimethylformamide to yield positional isomer impurity step-II which on hydrolysis with O-phosphoric acid in acetonitrile yields positional isomer impurity (VI) as shown below:

The process for the preparation of pentanoyl impurity (VII) comprising reacting N-(6-bromo-5-methylpyridin-2-yl)-1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclo propane-1-carboxamide (LMC-II) with (3-Pentanoyl phenyl) boronic acid in dimethylformamide with potassium carbonate, water and Pd(PPh3)4 to yield pentanoyl impurity (VII) as shown below:

The process for the preparation of PBAB acid dimer impurity (VIII) comprising reacting (3-(tert-butoxycarbonyl)phenyl)boronic acid (PBAB ester) with 3-bromo t-butyl benzoate, potassium carbonate, Pd(PPh3)4 and water in dimethylformamide to yield PBAB acid dimer step-I which is reacted with O-phosphoric acid in acetonitrile to yield PBAB acid dimer impurity (VIII) which is then reacted with sodium hydroxide in water to form sodium salt of PBAB acid dimer Impurity (VIII) as shown below:

In yet another embodiment the present invention provide the process for preparation of ivacaftor impurities of the present invention as follows.
The process for the preparation of dimer impurity (i) comprising reacting ivacaftor (B) with acid intermediate (IVF-I), N, N’-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) in presence of dimethylformamide to yield dimer impurity (i) as shown below:

The process for the preparation of methyl ether impurity (ii) comprising reacting ivacaftor (B) with methyl iodide (MeI), sodium hydroxide and water in presence of methanol to yield methyl ether impurity (ii) as shown below:

The process for the preparation of nitro ester impurity (iii) comprising reacting acid intermediate (IVF-I) with 2,4-di-tert-butyl-5-nitrophenol (IVF-II), triphenylphosphine (PPh3), iodine (I) and triethylamine in presence of dichloromethane to yield nitro ester impurity (iii) as shown below:

The process for the preparation of amino ester impurity (iv) comprising reacting acid intermediate (IVF-I) with 2,4-di-tert-butyl-5-nitrophenol (IVF-II), Triphenylphosphine (PPh3), iodine (I), triethylamine in presence of dichloromethane to yield nitro ester impurity (V) which is reduced in Pd/C hydrogen in methanol and dichloromethane to yield amine ester impurity (iv) as shown below:

The process for the preparation of methyl carbonate impurity (v) comprising reacting ivacaftor (B) with methyl chloroformate, triethylamine in presence of tetrahydrofuran (THF) to yield methyl carbonate impurity (v) as shown below:

The process for the preparation of 2-hydroxy isomer impurity (vi) comprising reacting acid intermediate (IVF-I) with 2-amino-4,6-di-tert-butylphenol (IVF-III), N,N,N',N'-tetramethyl-o-(1h-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU) and triethylamine in presence of dimethylformamide to yield 2-hydroxy isomer impurity (vi) as shown below:

The process for the preparation of aniline derivative impurity (vii) comprising reacting acid intermediate (IVF-I) with aniline, N,N,N',N'-tetramethyl-o-(1h-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU) and triethylamine in presence of dimethylformamide to yield aniline derivative impurity (vii) as shown below:

In further embodiment, the invention is directed to a method of using lumacaftor and ivacaftor impurities as reference standard for analyzing the purity of the lumacaftor and ivacaftor respectively.
The presence of the lumacaftor of the present invention in a sample of lumacaftor, salts, or solvates thereof may be determined by chromatographic techniques such as HPLC, LC-MS, or TLC by comparing the retention time of different components of a sample of lumacaftor, salts, or solvates thereof with the retention time of the lumacaftor impurities of the present invention.
The presence of the ivacaftor impurities of the present invention in a sample of ivacaftor, salts, or solvates thereof may be determined by chromatographic techniques such as HPLC, LC-MS, or TLC by comparing the retention time of different components of a sample of ivacaftor, salts, or solvates thereof with the retention time of the ivacaftor impurities of the present invention.
One such method for testing the purity of a sample comprising lumacaftor or ivacaftor, salts, or solvates thereof by determining the presence of the lumacaftor or ivacaftor impurities of the present invention respectively in the sample comprising the steps of:
a) dissolving lumacaftor or ivacaftor, salts, or solvates thereof in a solvent to obtain a sample solution;
b) dissolving a sample of the lumacaftor or ivacaftor impurities of the present invention respectively in a solvent to make a reference standard solution;
c) subjecting the sample solution and the reference standard solution to a chromatographic technique; and
d) determining the presence of the lumacaftor or ivacaftor impurities of the present invention respectively in the sample of lumacaftor or ivacaftor, salts, or solvates thereof using the reference standard solution.
The reference standard solution comprises the sample of the lumacaftor or ivacaftor impurities in a solvent selected from methanol, acetonitrile, tetrahydrofuran and water.
In yet another embodiment the present invention provides a method for preparing lumacaftor or ivacaftor, salts, or solvates thereof suitable for pharmaceutical use, comprising the steps of:
a) preparing lumacaftor or ivacaftor, salts, or solvates thereof;
b) assessing the purity of lumacaftor or ivacaftor, salts, or solvates thereof by using the lumacaftor impurities of formula (I)-(VIII) or ivacaftor impurities of formula (i)-(vii) as a reference standard respectively; and
c) subjecting the lumacaftor or ivacaftor, salts, or solvates thereof to purification, wherein step c) may be carried out before or after step b).
The lumacaftor or ivacaftor, salts, or solvates thereof may be prepared by any of the processes known in the art.
The purification of lumacaftor or ivacaftor, salts or solvates thereof may be carried out using purification techniques known to the skilled in the art, such as chromatography, distillation, and crystallization.
In yet another embodiment the present invention provides lumacaftor, salts, or solvates thereof substantially free of the impurities of formula (I)-(VIII).
In yet another embodiment the present invention provides ivacaftor, salts, or solvates thereof substantially free of the impurities of formula (i)-(vii).
METHODS:
The IR spectrum was recorded using a PerkinElmer-400 Series FTIR.
The Mass spectrum was recorded using an waters Aquity QDa mass Spectrometer system.
The NMR spectrum was recorded using a Bruker A vance III HD 500 MHz instrument.
For lumacaftor: The HPLC purity was determined using an Ascentis Express C8, (4.6 mm x 150 mm), 2.7 µm column with a flow rate 1.0 ml / minute; Column oven temperature: 25°C; Sample tray temperature: 10°C; Detector: UV at 215 nm; Injection volume: 5 µl; Run time: 45 minutes.
For ivacaftor: The HPLC purity was determined using an Zorbax SB-Aq(4.6 x 250) mm ,5 µm column with a flow rate 1.5 Ml/minute Column oven temperature: 20°C; Auto Sampler temperature: 10°C; Detector: UV at 215 nm; Injection volume: 5µL; Run time: 55minutes.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents may be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
EXAMPLES:
EXAMPLE 1: Synthesis of 3-(6-(1-(3,4-dihydroxyphenyl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid (dihydroxy impurity of formula (I)):

10 gm of lumacaftor (A) and 100 ml ortho phosphoric acid were heated under stirring at 100° C ± 5° C for 43-46 hrs. The resulting mixture was then poured in 200 ml ice cold water and then the aqueous phase was extracted with 400 ml ethyl acetate. The organic phase was dried over Na2SO4 and concentrated under vacuum to produce solid residue to which 25 ml acetone was added. The solid was filtered, washed with acetone and dried in oven yielding Dihydroxy impurity.
Yield: 22 .47 %
1HNMR (400 MHz, DMSO), ?? (in ppm): 12.89 (S, 1H), 9.10 (2H), 8.14-7.54 (7H), 6.85-6.60 (3H), 2.84 (3H), 1.45-1.43 (2H), 1.08-1.05 (2H).
Mass: 405.3 [M+H]+
IR in KBr, (in cm-l): 3368, 1678, 1512, 1473, 1136 and 801.
Figure 1 provides the HPLC of a standard solution of the dihydroxy impurity of Formula I.
EXAMPLE 2: Synthesis of N-(6-bromo-5-methylpyridin-2-yl)-3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl) benzamide (dimer impurity of formula (II)):

5.29 gm oxalyl chloride was added dropwise under N2 atmosphere to 15 gm of lumacaftor (A) in 150 ml dichloromethane. 2-3 drops of dimethylformamide was added to the above mixture, stirred for 3-4 hrs and then concentrated under N2 atmosphere. To this solid was added dropwise a mixture of 5.2 gm 6-bromo-5-methylpyridin-2-amine (BMPA) and 8.43 gm of triethylamine under N2 atmosphere, stirred for 2-3 hrs, added 100 ml water, extracted organic phase, washed organic phase with 100 ml 10% HCl solution and then with 100 ml 5 % NaHCO3 and 100 ml water. Organic phase dried over Na2SO4 and the product is separated over column chromatography using hexane and ethyl acetate as solvent yielding dimer impurity.
Yield: 54.9 %
1HNMR (400 MHz, DMSO-d6) + DCl, ?? (in ppm): 8.26-8.08 (5H), 7.81-7.78 (2H), 7.69-7.28 (4H), 2.53-2.50 (6H), 1.61-1.59 (2H), 1.28-1.26 (2H).
Mass: 621.1 [M+H]+ , 1242.7 [2M+H]+
IR in KBr, (in cm-l):2926, 1675, 1520, 1063 and 833.
Figure 2 provides the HPLC of a standard solution of the dimer impurity of Formula II.
EXAMPLE 3: Synthesis of methyl 3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoate (methyl ester impurity of formula (III)):

4.7 gm of thionyl chloride was added dropwise to 7 gm lumacaftor (A) in 35 ml of methanol at 0°-5°C. The reaction mixture was stirred to 20°-25°C and then heated to 45°-55°C for 6-7 hrs. The reaction mixture was then allowed to cool to 30°-35°C to obtain the solid to which 100 ml of water was added. The solid obtained was filtered, washed with water and dried under vacuum yielding methyl ester impurity.
Yield: 90.2 %
1HNMR (400 MHz, DMSO-d6), ?? (in ppm): 9.31 (1H), 8.89 (1H), 8.0-7.30 (8H), 3.85 (3H), 2.50-2.49 (3H), 1.53 (2H), 1.18 (2H).
Mass: 467.4, 468.4 [M+H]+, 933.5, 934.5 [2M+H]+
IR in KBr, (in cm-l): 3124, 1704, 1598, 1033, 923 and 757.
Figure 3 provides the HPLC of a standard solution of the methyl ester impurity of Formula III.
EXAMPLE 4: Synthesis of 2-(3-carboxyphenyl)-6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridine 1-oxide (N-Oxide impurity of formula (IV)):

7 gm of meta-chloro per benzoic acid (m-PCBA) in 100 ml dichloromethane was added dropwise to 10 gm lumacaftor (A) in 100 ml dichloromethane and then stirred for 24 hrs at 20°-35°C. The solid obtained was filtered, washed with dichloromethane and dried under vacuum yielding N-oxide impurity.
Yield: 90.2 %
1HNMR (400 MHz, DMSO –d6), ?? (in ppm): 13.11 (1H), 9.90 (1H), 8.26-7.40 (9H), 1.96 (3H), 1.59-1.57 (2H), 1.27-1.25 (2H).
Mass: 469.3 [M+H]+, 937.5 [2M+H]+ , 467.3 [M-H]-, 936.5 [M-H]- .
IR in KBr, (in cm-l): 3273, 1695, 1368, 978 and 695.
Figure 4 provides the HPLC of a standard solution of the N-oxide impurity of Formula IV.
EXAMPLE 5: Synthesis of 3-(6-(1-(3,4-dihydroxyphenyl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid (descyclopropyl impurity of formula (V)):

6M sodium hydroxide solution was added to 10 gm descyclopropyl cyano compound in 100 ml ethanol, the reaction mixture was heated to 75°-85°C for 17-18 hrs. The reaction mixture was cooled to 20°-30°C and concentrated to obtain the oily residue to which 100 ml of water and 100 ml of methyl tertiary butyl ether was added, followed by 400 ml 1N HCl solution up to pH = 2-3. The organic phase was separated, dried over Na2SO4 and concentrated to obtain 11 gm descyclopropyl impurity step-I as oil.
8.14 gm of oxalyl chloride was added dropwise to 11 gm descyclopropyl impurity step-I in 80 ml dichloromethane, the reaction mixture was stirred for 1-2 hrs at 20°-30°C and then concentrated under vacuum. To this was added dropwise a mixture of 8 gm 6-bromo-5-methylpyridin-2-amine (BMPA) in 40 ml dichloromethane and 12.9 gm of triethylamine and stirring was continued for 2-3 hrs. To this mixture 100 ml of water was added, separated organic phase, washed organic phase with 200 ml 10% HCl solution, then with 100 ml 5 % NaHCO3 and then with 100 ml water. Organic phase dried over Na2SO4 and concentrated to give 13.7 gm descyclopropyl impurity step-II as oil.
8.3 gm (3-(tert-butoxycarbonyl)phenyl)boronic acid (PBAB ester) was added to 13.7 gm descyclopropyl impurity step-II in 110 ml dimethylformamide, followed by 9.8 gm potassium carbonate and 0.6 gm Pd(PPh3)4. The reaction mixture was heated to 105°-115°C for 4-5 hrs, then cooled to 85°-95°C and 250 ml of water was added and heating continued for overnight, extracted with dichloromethane, separated the organic phase, concentrated and the product is separated over column chromatography using hexane and ethyl acetate as solvent yielding 4 gm descyclopropyl impurity step-III as solid.
6 ml ortho phosphoric acid was added to 4 gm descyclopropyl impurity step-III in 40 ml acetonitrile. The reaction mixture was heated to 70°-80°C for overnight, cooled to 20°-30°C, 100 ml of water was added, stirred, filtered, and washed with water. To this solid was added 10 % NaHCO3 up to pH = 6-8, stirred, filtered the solid, washed with water and dried under vacuum yielding descyclopropyl impurity.
Yield: 51.44 %
1HNMR (400 MHz, DMSO), ?? (in ppm): 13.11 (1H), 10.77 (1H), 8.11-7.16 (9H), 3.36 (2H), 2.52-2.49 (3H),
Mass: 853 [M+H]+, 851.1, 852.1[M-H]-
IR in KBr, (in cm-l): 3060, 1681, 1499, 1239, 1036 and 701.
Figure 5 provides the HPLC of a standard solution of the descyclopropyl impurity of Formula V.
EXAMPLE 6: Synthesis of 3-(4-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid (positional isomer impurity of formula (VI)):

6.8 ml oxalyl chloride was added under N2 atmosphere to 15.5 gm 1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxylic acid (CPCA) in 120 ml dichloromethane and 1 ml dimethylformamide, stirred for 2-3 hrs at 20° to 30°C, concentrated under N2 atmosphere. To this was added dropwise at 10° to 20°C mixture of 10 gm 2-bromo-3-methylpyridin-4-amine (isomer of BMPA) in 60 ml dichloromethane and 22.3 ml triethylamine, stirred overnight at 20° to 30°C, 200 ml water was added, separated organic phase, organic phase washed with 400 ml 10% HCl then with 200 ml 5 % NaHCO3 and then with 200 ml water. Organic phase dried over Na2SO4, concentrated, co-distilled with 50 ml isopropyl alcohol, added 50 ml isopropyl alcohol, heated to 40° to 55°C, cooled to 0° to 5°C, filtered solid, washed with chilled isopropyl alcohol and dried under vacuum yielding 3.3 gm positional isomer impurity step-I.
1.87 gm (3-(tert-butoxycarbonyl)phenyl) boronic acid (PBAB ester) and 2.2 gm potassium carbonate was added to 3.3 gm positional isomer impurity step-I compound in 27 ml dimethylformamide followed by 7 ml water and 0.13 gm Pd(PPh3)4. The reaction mixture was heated to 110°-120°C 4-5 hrs, cooled to 90°-95°C, added 60 ml water, cooled to 20°-30°C, extracted with 200 ml dichloromethane, separated organic phase, concentrated under vacuum to obtain the oil which was poured in ice cold water, stirred, filtered the solid, washed with water and dried under vacuum yielding 8 gm positional isomer impurity step-II.
12 ml of ortho phosphoric acid was added to 8 gm positional isomer impurity step-II compound in 80 ml acetonitrile, heated to 60°-65°C for 3-4 hrs, cooled to 20°-30°C, poured the mixture in 160 ml water, extracted with 400 ml dichloromethane, separated the organic phase, organic phase dried over Na2SO4, concentrated under vacuum to obtain the solid which was purified by using acetone and dried under vacuum yielding positional isomer impurity.
Yield: 16.90 %
1HNMR (400 MHz, DMSO-d6), ?? (in ppm): 1.22-1.20 (2H), 1.54-1.52 (2H), 1.92 (3H), 7.40-7.37 (2H), 8.40-7.41 (6H).
Mass: 453.1 [M+H]+, 905.1 [2M+H]+
IR in KBr, (in cm-l): 3412, 2923, 1696, 1495, 1166, 855 and 749
Figure 6 provides the HPLC of a standard solution of the positional isomer impurity of Formula VI.
EXAMPLE 7: Synthesis of 1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)-N-(5-methyl-6-(3-pentanoylphenyl)pyridin-2-yl)cyclopropane-1-carboxamide (pentanoyl impurity of formula (VII)):

2.19 gm (3-pentanoyl phenyl) boronic acid was added to 4 gm N-(6-bromo-5-methylpyridin-2-yl)-1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclo propane-1-carboxamide (LMC-II) in 32 ml dimethylformamide, followed by 2.6 gm potassium carbonate, 8 ml water and 0.16 gm Pd(PPh3)4. The reaction mixture was heated to 105° to 120°C 4-5 hrs, cooled to 90° to 95°C, added 70 ml water, cooled to 20° to 30°C, extracted with 100 ml dichloromethane, separated organic phase, concentrated under vacuum to obtain the oil which was poured in ice cold water, stirred, filtered the solid, washed with water, solid obtained was stirred with hexane, filtered and dried under vacuum yielding pentanoyl impurity.
Yield: 68 %
1HNMR (400 MHz, DMSO-d63), ?? (in ppm): 0.91-0.88 (3H), 1.18-1.15 (2H), 1.34-1.31 (2H), 2.51-1.50 (7H), 3.33-3.00 (2H), 7.99-7.34 (9H), 8.93 (1H).
Mass: 491.2 [M+H]+, 985.2 [2M+H]+
IR in KBr, (in cm-l): 3381, 1959, 1679, 1444, 1157 and 835.
Figure 7 provides the HPLC of a standard solution of the pentanoyl impurity of Formula VII.
EXAMPLE 8: Synthesis of [1,1’-biphenyl]-3,4’-dicarboxylic acid (PBAB acid dimer impurity of formula (VIII)):

9.1 gm (3-(tert-butoxycarbonyl)phenyl)boronic acid (PBAB ester) was added to 10 gm 3-bromo t-butyl benzoate in 80 ml dimethylformamide, followed by 10.7 gm potassium carbonate and 0.7 gm Pd(PPh3)4. The reaction mixture was heated to 100° to 110°C 4-5 hrs, cooled to 90° to 95°C, added 500 ml cooled water (10° to 15°C), extracted with 300 ml ethyl acetate, separated organic phase, organic phase dried over Na2SO4, concentrated under vacuum to obtain the 15.1 gm PBAB acid dimer step-I as oil.
19.5 ml ortho phosphoric acid was added to 13 gm PBAB acid dimer step-I in 130 ml acetonitrile, heated to 60° to 75°C for 3-4 hrs, cooled to 20° to 30°C, reaction mixture was poured in 200 ml water, filtered the solid, washed with water and dried under vacuum to obtain PBAB acid dimer impurity which was converted to its sodium salt using sodium hydroxide in water.
Yield: 73.6 %
1HNMR (400 MHz, DMSO-d6), ?? (in ppm): 1.58 (1 H), 8.19-7.33 (4H).
Mass: 241 [M+H]+
IR in KBr, (in cm-l): 3390, 1610, 1558, 1387, 747, 690
Figure 8 provides the HPLC of a standard solution of the PBAB acid dimer impurity of Formula VIII.
EXAMPLE 9: Synthesis of 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate (dimer impurity of formula (i)):

5.0 gm ivacaftor (B) was charged under N2 atmosphere at 0° to 5°C to a mixture of 2.4 gm acid intermediate (IVF-I) in 100 ml dimethylformamide, 3.1 gm N, N’-dicyclohexylcarbodiimide (DCC) and 0.46 gm 4-dimethylaminopyridine (DMAP) prepared under N2 atmosphere at 0° to 5°C. The reaction mixture was stirred for 95-100 hrs at 20° to 25°C. To the above mixture 500 ml water was added dropwise, stirred for 1.5-2 hrs and solid obtained was filtered. The solid obtained was dissolved in 200 ml methanol, stirred, filtered, concentrated and then again dissolved in 400 ml (1:1) mixture of ethyl acetate and water, stirred, separated the organic layer, concentrated and the solid obtained was dried under vacuum yielding dimer impurity.
Yield: 35.79 %
1HNMR (400 MHz, DMSO), ?? (in ppm):12.71 (2H), 12.06 (1H), 8.85-7.54 (12H), 1.49-1.37 (18H)
Mass: 564.2[M+H] +
IR in KBr, (in cm-l): 3445, 3063, 1845, 1738, 1476, 1291, 1190, 873 and 771
Figure 9 provides the HPLC of a standard solution of the dimer impurity of formula (i).
EXAMPLE 10: Synthesis of N-(2,4-di-tert-butyl-5-methoxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (methyl ether impurity of formula (ii)):

3.0 gm ivacaftor (B) in 15 ml methanol was added to sodium hydroxide solution prepared from 0.6 gm sodium hydroxide and 15 ml water. To the above mixture 2.1 gm methyl iodide was added dropwise at -20° to -30°C. After the addition, the reaction mixture was allowed to cool at 20°-30°C and then heated to 90°-100°C. The reaction mixture was stirred for 5-6 hrs and then the reaction mixture was then allowed to cool at 20°-30°C, solid obtained was filtered, dissolved in 1:1 dichloromethane and ethyl acetate, and separated over column chromatography using hexane, dichloromethane and ethyl acetate as solvent yielding methyl ether impurity.
Yield: 24.71 %
1HNMR (400 MHz, DMSO), ?? (in ppm):11.78 (1H), 9.2 (1H), 8.98-7.08 (7H), 4.0 (3H), 1.38-1.35 (18H)
Mass: 407.3[M+H]+ 813.4[2M+H]+
Figure 10 provides the HPLC of a standard solution of the methyl ether impurity of formula (ii).
EXAMPLE 11: Synthesis of 2,4-di-tert-butyl-5-nitrophenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate (nitro ester impurity of formula (iii)):

20 gm 2,4-di-tert-butyl-5-nitrophenol (IVF-II) was added at 0° to 5°C under N2 atmosphere to a mixture of 15.09 gm acid intermediate (IVF-I) in 300 ml dichloromethane, 22.9 gm triphenylphosphine (PPh3) and 22.2 gm iodine prepared under N2 atmosphere. 24.1 gm triethylamine was added dropwise to the above mixture at 0° to 5°C and stirred at 20° to 25°C for 24-27 hrs, concentrated the reaction mixture under vacuum and, charged 200 ml ethyl acetate to this, stirred the mixture at 20° to 30°C for 1-2 hrs, filtered, washed with water. The solid was heated with 200 ml acetonitrile at 70° to 80°C for 1-2 hrs, allowed to cool at 20° to 30°C, filtered, washed with acetonitrile and dried under vacuum yielding nitro ester impurity.
Yield: 46.7 %
1HNMR (400 MHz, DMSO), ?? (in ppm):12.67-12.65 (1H), 8.80-7.47(7H), 1.38 (18H)
Mass: 421.2[M-H]-, 845.1[M+H]+
IR in KBr, (in cm-l): 3437, 1368, 2960, 1724, 1627, 1616, 1297, 1074, 912 and 762
Figure 11 provides the HPLC of a standard solution of the nitro ester impurity of formula (iii).
EXAMPLE 12: Synthesis of 5-amino-2,4-di-tert-butylphenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate (amino ester impurity of formula (iv)):

1 liter dichloromethane was added to the 7.0 gm nitro ester impurity (iv) dissolved in 1 liter methanol, filtered the solution. The 3.0 gm solid obtained was again dissolved in 500 ml methanol, added to 500 ml dichloromethane and filtered. The filtrates were combined and to this was added 1.5 gm 10% Pd/C and the reaction mixture was stirred under 4 kg H2 gas pressure for 12 hrs. The reaction mixture was filtered over 100gm celite, washed with 500 ml methanol, organic layer concentrated under vacuum. The residue was dissolved in 100 ml 1:1 methanol & dichloromethane, stirred, filtered, and then again dissolved in 100 ml methanol, stirred, filtered and dried under vacuum yielding amine ester impurity.
Yield: 25.11%
1HNMR (400 MHz, DMSO), ?? (in ppm):8.76(1H), 8.22(1H), 7.77-7.23(5H), 1.43-1.29 (18H)
Mass: 393.2 [M+H]+
IR in KBr, (in cm-l): 3494, 3381, 2963, 1738, 1536, 1296, 1197 and 765
Figure 12 provides the HPLC of a standard solution of the amino ester impurity of formula (iv).
EXAMPLE 13: Synthesis of 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl methyl carbonate (methyl carbonate impurity of formula (v)):

5.1 gm triethylamine was added dropwise to 5 gm ivacaftor (B) in 100 ml tetrahydrofuran followed by dropwise 12 gm methyl chloroformate. The reaction was stirred at 20° to 30°C for 16-17 hrs, 200 ml water and 200 ml dichloromethane was added to above reaction mixture. Organic layer separated, washed with Na2CO3, dried under Na2SO4, concentrated under vacuum and separated over column chromatography using hexane, dichloromethane and ethyl acetate as solvent yielding methyl ether impurity.
Yield: 65.60 %
1HNMR (400 MHz, DMSO), ?? (in ppm):12.94 (1H), 12.08 (1H), 8.87 (1H), 8.35-7.39 (7H), 3.85 (3H), 1.46-1.32 (18H)
Mass: 451.2[M+H]+
IR in KBr, (in cm-l): 3264, 3065, 2911, 1767, 1656, 1520, 1189 and 763
Figure 13 provides the HPLC of a standard solution of the methyl carbonate impurity of formula (v).
EXAMPLE 14: N-(3,5-di-tert-butyl-2-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (2-hydroxy isomer impurity of formula (vi)):

2.7 gm triethylamine was added dropwise to a mixture of 1.7 gm acid intermediate (IVF-I) in 35 ml dimethylformamide and 4.7 gm N,N,N',N'-tetramethyl-o-(1h-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU) and stirred at 20° to 30°C for 1 hr. To this was added 2.3 gm 2-amino-4,6-di-tert-butylphenol (IVF-III) in 17 ml dimethylformamide and stirred at 20° to 30°C for 16-18 hrs. 100 ml water was added to the above mixture, stirred, filtered, washed with water, filtered and dried under vacuum yielding 2-hydroxy isomer impurity.
1HNMR (400 MHz, DMSO), ?? (in ppm):13.03-13.00 (1H), 9.27-9.93 (1H), 8.36 (1H), 8.36-8.34 (1H), 7.58-7.9 (6H)
Mass: 393.3 [M+H]+
Figure 14 provides the HPLC of a standard solution of the 2-hydroxy isomer impurity of formula (vi).
EXAMPLE 15: 4-oxo-N-phenyl-1,4-dihydroquinoline-3-carboxamide (aniline derivative impurity of formula (vii)):

3.2 gm triethylamine was added dropwise under N2 atmosphere to a mixture of 2.0 gm acid intermediate (IVF-I) in 20 ml dimethylformamide and 4.8 gm N,N,N',N'-tetramethyl-o-(1h-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU) and stirred at 20° to 30°C for 0.5-1 hr. To this was added dropwise 1.37 gm aniline and stirred at 20° to 30°C for 75-80 hrs. 100 ml ethyl acetate and 50 ml saturated NaHCO3 solution was added to the above mixture, separated organic layer, added 50 ml water to organic layer and adjusted the pH= 4-5 using 1:1 HCl, separated organic layer and concentrated. 150 ml ethyl acetate was added to the above residue, 80 ml water was added, stirred, filtered, separated the ethyl acetate layer, concentrated under vacuum yielding aniline derivative impurity.
Yield: 25.73 %
1HNMR (400 MHz, DMSO), ?? (in ppm):12.95 (1H), 12.50 (1H), 8.89 (1H), 8.34-8.3391H), 7.83-7.08(8H)
Mass: 263.1[M+H]+
IR in KBr, (in cm-l): 3023, 2981, 1669, 1619, 1523, 1442, 1357, 1297 and 755
Figure 15 provides the HPLC of a standard solution of the aniline derivative impurity of formula (vii).
EXAMPLE 16: HPLC method for the analysis lumacaftor impurities.
The chromatographic separation was carried out using an Ascentis Express C8, (4.6 mm x 150 mm), 2.7 µm column with a flow rate 1.0 ml / minute; Column oven temperature: 25°C; Sample tray temperature: 10°C; Detector: UV at 215 nm; Injection volume: 5 µl; Run time: 45 minutes.
The buffer solution was prepared by homogeneously mixing 0.2% v/v perchloric acid in water, adjusting the pH of the solution to 2.30 + 0.05 with 20% aqueous potassium hydroxide solution.
The mobile phase was prepared by mixing the buffer solution and acetonitrile. Acetonitrile is used as diluent.
The analysis of the lumacaftor impurities of the present invention in a sample lumacaftor was carried out by injecting the test sample (prepared by dissolving 40 mg of lumacaftor in 25 ml of diluent, 5.0 ml methanol, 2.0 ml water and then making up the volume to 50 ml by adding the diluent) into the column and running the chromatogram for 45 minutes.
The retention time for lumacaftor and its impurities is shown in HPLC chromatogram.
Figure 16 provides the HPLC of a sample of lumacaftor active pharmaceutical ingredient containing the lumacaftor impurities of the present invention.

EXAMPLE 17: HPLC method for the analysis ivacaftor impurities.
The chromatographic separation was carried out using an Zorbax SB-Aq(4.6 x 250) mm ,5 µm column with a flow rate 1.5 Ml/minute Column oven temperature: 20°C; Auto Sampler temperature: 10°C; Detector: UV at 215 nm; Injection volume: 5µL; Run time: 55minutes.
The buffer solution was prepared by homogeneously mixing 0.2% v/v perchloric acid in water, adjusting the pH of the solution to 2.30 + 0.05 with 20% aqueous potassium hydroxide solution.
The mobile phase was prepared by homogeneously mixing water, acetonitrile and perchloric acid (2000:20:0.4).
The diluent was prepared by dissolving 0.77 gm ammonium acetate in homogeneous mixture of 1000 ml acetonitrile and 100 ml water.
The analysis of the ivacaftor impurities of the present invention in a sample ivacaftor was carried out by injecting the test sample (prepared by dissolving 50 mg of ivacaftor in 2 ml of tetrahydrofuran, 5.0 ml methanol and then making up the volume to 50 ml by adding the diluent) into the column and running the chromatogram for 55 minutes.
The retention time for ivacaftor and its impurities is shown in HPLC chromatogram.
Figure 17 provides the HPLC of a sample of ivacaftor active pharmaceutical ingredient containing the ivacaftor impurities of the present invention.
,CLAIMS:1) Lumacaftor impurities
a) 3-(6-(1-(3,4-dihydroxyphenyl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid of formula (I)

b) N-(6-bromo-5-methylpyridin-2-yl)-3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzamide of formula (II)

c) Methyl 3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoate of formula (III)

d) 2-(3-carboxyphenyl)-6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridine 1-oxide of formula (IV)

e) 3-(6-(2-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)acetamido)-3-methylpyridin-2-yl)benzoic acid of formula (V)

f) 3-(4-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)cyclopropane-1-carboxamido)-3-methylpyridin-2-yl)benzoic acid of formula (VI)

g) 1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl)-N-(5-methyl-6-(3-pentanoylphenyl) pyridin-2-yl)cyclopropane-1-carboxamide of formula (VII)

h) [1,1'-biphenyl]-3,4'-dicarboxylic acid of formula (VIII)

2) Use of the lumacaftor impurities as claimed in claim 1, as a reference standard for analyzing the purity of lumacaftor, salts, or solvates thereof in a sample comprising lumacaftor, salts, or solvates thereof.
3) A chromatographic method for testing the purity of a sample comprising lumacaftor, or salts, or solvates thereof by determining the presence of the lumacaftor impurities as claimed in claim 1, comprising the steps of:
a) dissolving lumacaftor, salts, or solvates thereof in a solvent to obtain a sample solution;
b) dissolving a sample of the lumacaftor impurities of formula (I)-(VIII), in a solvent to make a reference standard solution;
c) subjecting the sample solution and the reference standard solution to a chromatographic technique; and
d) determining the presence of the lumacaftor impurities of formula (I)-(VIII), in the sample using the reference standard solution.
4) A method for preparing lumacaftor, salts, or solvates thereof suitable for pharmaceutical use, comprising the steps of:
a) preparing lumacaftor, salts, or solvates thereof;
b) assessing the purity of lumacaftor, salts, or solvates thereof by using the lumacaftor impurities of formula (I)-(VIII) as a reference standard; and
c) subjecting the lumacaftor, salts, or solvates thereof to purification, wherein step c) may be carried out before or after step b).
5) Lumacaftor, salts, or solvates thereof substantially free of the impurities as claimed in claim 1.
6) Ivacaftor impurities
a) 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate of formula (i)

b) N-(2,4-di-tert-butyl-5-methoxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide of formula (ii)

c) 2,4-di-tert-butyl-5-nitrophenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate of formula (iii)

d) 5-amino-2,4-di-tert-butylphenyl 4-oxo-1,4-dihydroquinoline-3-carboxylate of formula (iv)

e) 2,4-di-tert-butyl-5-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl methyl carbonate of formula (v)

f) N-(3,5-di-tert-butyl-2-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide of formula (vi)

g) 4-oxo-N-phenyl-1,4-dihydroquinoline-3-carboxamide of formula (vii)

7) Use of the ivacaftor impurities as claimed in claim 6, as a reference standard for analyzing the purity of ivacaftor, salts, or solvates thereof in a sample comprising ivacaftor, salts, or solvates thereof.
8) A chromatographic method for testing the purity of a sample comprising ivacaftor, or salts, or solvates thereof by determining the presence of the ivacaftor impurities as claimed in claim 6, comprising the steps of:
a) dissolving ivacaftor, or salts, or solvates thereof in a solvent to obtain a sample solution;
b) dissolving a sample of the ivacaftor impurities of formula (i)-(vii), in a solvent to make a reference standard solution;
c) subjecting the sample solution and the reference standard solution to a chromatographic technique; and
d) determining the presence of the ivacaftor impurities of formula (i)-(vii), in the sample using the reference standard solution.
9) A method for preparing ivacaftor, salts, or solvates thereof suitable for pharmaceutical use, comprising the steps of:
a) preparing ivacaftor, salts, or solvates thereof;
b) assessing the purity of ivacaftor, salts, or solvates thereof by using the lumacaftor impurities of formula (i)-(vii) as a reference standard; and
c) subjecting the ivacaftor, salts, or solvates thereof to purification, wherein step c) may be carried out before or after step b).
10) Ivacaftor, salts, or solvates thereof substantially free of the impurities as claimed in claim 6.