Pemetrexed Disodium

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₂₀H₁₉N₅Na₂O₆ · 7H₂O            597.49

l-Glutamic acid, N-[4-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-, disodium salt, heptahydrate; Disodium N-{p-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-l-glutamate heptahydrate CAS RN®: 357166-29-1; UNII: 9T47E4OM16. (RB 7-Aug-2024)

C₂₀H₁₉N₅Na₂O₆            471.38

Anhydrous CAS RN®: 150399-23-8; UNII: 2PKU919BA9 (RB 7-Aug-2024)

C₂₀H₂₁N₅O₆             427.42

Pemetrexed (free acid) CAS RN®: 137281-23-3; UNII: 04Q9AIZ7NO.

C₂₀H₁₉N₅Na₂O₆ · 2.5 H₂O 516.42

Hemipentahydrate CAS RN®: 357166-30-4; UNII: F4GSH45R4C. (RB 7-Aug-2024)

1 DEFINITION

Pemetrexed Disodium contains NLT 97.5% and NMT 102.0% of pemetrexed disodium (C₂₀H₁₉N₅Na₂O₆), calculated on the anhydrous and solvent-free basis.

[Caution—Handle pemetrexed disodium with great care as it alters genetic material and may be irritating to the eyes and skin.]

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or 197K

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Enantiomeric Purity test.

C. Identification Tests—General 〈191〉, Chemical Identification Tests, Sodium

3 ASSAY

Procedure

Buffer: 0.17% (v/v) glacial acetic acid in water. Adjust with a 50% sodium hydroxide solution to a pH of 5.3 ± 0.1.

Mobile phase: Acetonitrile and Buffer (11:89)

Standard solution: 0.15 mg/mL of USP Pemetrexed Disodium RS in water

Sample solution: 0.15 mg/mL of Pemetrexed Disodium in water

3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 285 nm

Column: 4.6-mm × 7.5-cm; 3.5-µm packing L7

Column temperature: 30°

Injection volume: 20 µL 

3.2 System suitability 

Sample: Standard solution 

Suitability requirements 

Tailing factor: 0.8–1.5 

Relative standard deviation: NMT 0.73% 

3.3 Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of pemetrexed disodium (C₂₀H₁₉N₅Na₂O₆) in the portion of Pemetrexed Disodium taken: 

Result = (r_U/r_S) × (C_S /C_U ) × 100  

r_U = peak response from the Sample solution 

r_S = peak response from the Standard solution 

C_S = concentration of USP Pemetrexed Disodium RS in the Standard solution (mg/mL) 

C_U = concentration of Pemetrexed Disodium in the Sample solution (mg/mL) 

Acceptance criteria: 97.5%–102.0% on the anhydrous and solvent-free basis

4 IMPURITIES

4.1 Organic Impurities 

Buffer: 1.45 g/L of ammonium formate in water. Adjust with formic acid to a pH of 3.5 ± 0.1.

Solution A: Acetonitrile and Buffer (5:95)

Solution B: Acetonitrile and Buffer (30:70)

Mobile phase: See Table 1. [Note—After each injection, re-equilibrate the chromatographic system at the initial condition for a minimum of 13 min.]

Table 1

System suitability stock solution: Prepare 3 mg/mL of USP Pemetrexed Disodium RS in 0.1 N sodium hydroxide. Heat this solution at 70° for 40 min.

[Note—The preparation degrades pemetrexed and generates the pemetrexed R-dimer and pemetrexed S-dimer as follows: Pemetrexed R-dimer: (2S,2′S)-2,2′-{[(R)-2,2′-Diamino-4,4′,6-trioxo-1,4,4′,6,7,7′-hexahydro-1′H,5H-5,6′-bipyrrolo[2,3-d]pyrimidine-5,5′- diyl]bis(ethylenebenzene-4,1-diylcarbonylimino)}diglutaric acid.

Pemetrexed S-dimer: (2S,2′S)-2,2′-{[(S)-2,2′-Diamino-4,4′,6-trioxo-1,4,4′,6,7,7′-hexahydro-1′H,5H-5,6′-bipyrrolo[2,3-d]pyrimidine-5,5′- diyl]bis(ethylenebenzene-4,1-diylcarbonylimino)}diglutaric acid.]

System suitability solution: Transfer 1 mL of the System suitability stock solution to a 10-mL volumetric ask and dilute with water to volume. Sensitivity solution: 0.1 µg/mL of USP Pemetrexed Disodium RS in water

Sample solution: 0.2 mg/mL of Pemetrexed Disodium in water. Do not sonicate.

4.1.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 250 nm

Column: 4.6-mm × 15-cm; 3.5-µm packing L7

Autosampler temperature: 2°–8°

Flow rate: 1 mL/min

Injection volume: 20 µL

4.1.2 System suitability

Samples: System suitability solution and Sensitivity solution

[Note—The relative retention times for the pemetrexed R-dimer and pemetrexed S-dimer peaks are 0.87 and 0.88, respectively.]

Suitability requirements

Peak-to-valley ratio: The ratio of the height of the pemetrexed R-dimer peak to the height of the valley between the pemetrexed R-dimer and pemetrexed S-dimer is NLT 1.5, System suitability solution.

Signal-to-noise ratio: NLT 10, Sensitivity solution

4.1.3 Analysis

Sample: Sample solution

Calculate the percentage of each impurity in the portion of Pemetrexed Disodium taken:

Result = (r_U /r_T ) × 100

r_U = peak area of each impurity from the Sample solution

r_T = total peak areas from the Sample solution

Acceptance criteria: See Table 2. Disregard any peak less than 0.05%.

Table 2

^a {4-[2-(2-Amino-1-methyl-4-oxo-4,7-dihydro-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-l-glutamic acid.

^b {4-[2-(2-Amino-4-oxo-4,7-dihydro-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-4-l-glutamyl-l-glutamic acid.

4.2 Enantiomeric Purity

Buffer: Dissolve 8 g of anhydrous beta cyclodextrin in 1 L of water. Add 15 mL of triethylamine to this solution and mix. Add about 6 mL of phosphoric acid and adjust with additional phosphoric acid to a pH of 6.0.

Mobile phase: Acetonitrile and Buffer (5:95)

Standard solution: 0.24 mg/mL of USP Pemetrexed Disodium RS in water

Sensitivity solution: 0.12 µg/mL of USP Pemetrexed Disodium RS in water from the Standard solution

Sample solution: 0.24 mg/mL of Pemetrexed Disodium in water

4.2.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 230 nm

Column: 4.6-mm × 25-cm; 5-µm packing L1

Temperatures

Autosampler: 2°–8°

Column: 40°

Flow rate: 1 mL/min

Injection volume: 50 µL

4.2.2 System suitability

Samples: Standard solution and Sensitivity solution

[Note—USP Pemetrexed Disodium RS contains a small amount of pemetrexed enantiomer disodium (disodium N-{p-[2-(2-amino-4,7-dihydro 4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-d-glutamate). The relative retention times for pemetrexed enantiomer and pemetrexed are about 0.94 and 1.0, respectively.]

Suitability requirements

Peak-to-valley ratio: The ratio of the height of the pemetrexed enantiomer peak to the height of the valley between the pemetrexed enantiomer and pemetrexed is NLT 5.0, Standard solution

Signal-to-noise ratio: NLT 10 for the pemetrexed peak, Sensitivity solution

4.2.3 Analysis

Sample: Sample solution

Calculate the percentage of pemetrexed enantiomer in the portion of Pemetrexed Disodium taken:

Result = (r_U /r_T ) × 100

r_U = peak area of pemetrexed enantiomer from the Sample solution

r_T = total peak areas of pemetrexed enantiomer and pemetrexed from the Sample solution

Acceptance criteria: NMT 0.3%

5 SPECIFIC TESTS

Change to read:

Water Determination 〈921〉, Method I, Method Ia or Method Ic:

For heptahydrate form: (RB 7-Aug-2024) 19.5%–22.1%

For hemipentahydrate form: 8.0%–10.5% (RB 7-Aug-2024)

pH 〈791〉

Sample: 56 mg/mL in water

Acceptance criteria: 7.5–8.4

Bacterial Endotoxins Test 〈85〉: It contains less than 0.17 USP Endotoxin Units/mg of pemetrexed.

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers. Store at room temperature.

Add the following:

Labeling: Label to indicate where it is hemipentahydrate form. (RB 7-Aug-2024)

Change to read:

USP Reference Standards 〈11〉

(RB 7-Aug-2024)

USP Pemetrexed Disodium RS