Fosamprenavir Calcium

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

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

DOWNLOAD PDF HERE

C₂₅H₃₄CaN₃O₉PS 623.67

Carbamic acid, [(1S,2R)-3-[[(4-aminophenyl)sulfonyl](2-methylpropyl)amino]-1-(phenylmethyl)-2-(phosphonooxy)propyl]-, C-[(3S)-tetrahydro-3-furanyl] ester, calcium salt (1:1);

(3S)-Tetrahydro-3-furyl [(αS)-α-[(1R)-1-hydroxy-2-(N¹-isobutylsulfanilamido)ethyl] phenethyl]carbamate, calcium phosphate (ester) (1:1);

Calcium (2R,3S)-1-[(4-amino-N-isobutylphenyl)sulfonamide]-4-phenyl-3-[({[(S)-tetrahydrofuran-3-yl]oxy}carbonyl)amino]butan-2-yl phosphate. CAS RN®: 226700-81-8; UNII: ID1GU2627N.

1 DEFINITION

Fosamprenavir Calcium contains NLT 98.0% and NMT 102.0% of fosamprenavir calcium (C₂₅H₃₄CaN₃O₉PS), calculated on the anhydrous and solvent-free basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197M 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 Assay.

C. Identification Tests—General 〈191〉, Chemical Identification Tests, Calcium: Meets the requirements

3 ASSAY

3.1 Procedure

Buffer: 4.68 g/L of monobasic sodium phosphate dihydrate in water. Add 1.5 mL of phosphoric acid per 1 L of this solution.

Mobile phase: Acetonitrile and Buffer (35:65)

Diluent: Acetonitrile and Buffer (20:80)

Standard solution: 0.26 mg/mL of USP Fosamprenavir Calcium RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Sample solution: 0.26 mg/mL of Fosamprenavir Calcium in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

3.2 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 266 nm

Column: 4.6-mm x 15-cm; 3.5-μm packing L1

Column temperature: 40°

Flow rate: 1.5 mL/min

Injection volume: 10 μL

3.3 System suitability

Sample: Standard solution

3.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 1.0%

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of fosamprenavir calcium (C₂₅H₃₄CaN₃O₉PSS) in the portion of Fosamprenavir Calcium taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of fosamprenavir from the Sample solution

r_S = peak response of fosamprenavir from the Standard solution

C_S = concentration of USP Fosamprenavir Calcium RS in the Standard solution (mg/mL)

C_U = concentration of Fosamprenavir Calcium in the Sample solution (mg/mL)

Acceptance criteria: 98.0%–102.0% on the anhydrous and solvent-free basis

4 IMPURITIES

4.1 Organic Impurities: Early-Eluting Impurities

Buffer, Mobile phase, Diluent, Sample solution, and Chromatographic system: Proceed as directed in the Assay.

System suitability solution: 0.26 mg/mL of USP Fosamprenavir System Suitability Mixture RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Standard solution: 0.26 μg/mL of USP Fosamprenavir Calcium RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

4.1.1 System suitability

Samples: System suitability solution and Standard solution

4.1.2 Suitability requirements

Resolution: NLT 1.5 between fosamprenavir pyrophosphate and fosamprenavir n-propyl homolog, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

4.1.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any individual early-eluting impurity in the portion of Fosamprenavir Calcium taken:

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × 100

r_U = peak response of any individual impurity from the Sample solution

r_S = peak response of fosamprenavir from the Standard solution

C_S = concentration of USP Fosamprenavir Calcium RS in the Standard solution (mg/mL)

C_U = concentration of Fosamprenavir Calcium in the Sample solution (mg/mL)

F = relative response factor (see Table 1)

Acceptance criteria: See Table 1. The reporting threshold is 0.03%.

Table 1

^a (2R,3S)-3-Amino-1-[(4-amino-N-isobutylphenyl)sulfonamide]-4-phenylbutan-2-yl dihydrogen phosphate.

^b(S)-Tetrahydrofuran-3-yl {(2S,3R)-4-[(4-amino-N-isobutylphenyl)sulfonamide]-3-([hydroxy(phosphonooxy)phosphoryl]oxy)-1-phenylbutan-2-yl}carbamate.

^c Calcium (2R,3S)-1-[(4-amino-N-propylphenyl)sulfonamide]-4-phenyl-3-[({[(S)-tetrahydrofuran-3-yl]oxy}carbonyl)amino]butan-2-yl phosphate.

^d Exclude any individual unspecified impurity that elutes after fosamprenavir.

^e Total impurities include the sum of all impurities determined in Organic Impurities: Early-Eluting Impurities, Organic Impurities: Late-Eluting

Impurities, and Limit of Fosamprenavir Related Compound A.

4.2 Organic Impurities: Late-Eluting Impurities

Buffer: 1.58 g/L of ammonium formate in water. Adjust with ammonia solution to a pH of 9.0.

Solution A: Acetonitrile and Buffer (19:81)

Solution B: Acetonitrile, tetrahydrofuran, and Buffer (45:5:50)

Solution C: 4.68 g/L of monobasic sodium phosphate dihydrate in water. Add 1.5 mL of phosphoric acid per 1 L of this solution.

Mobile phase: See Table 2.

Table 2

Diluent: Acetonitrile and Solution C (20:80)

System suitability solution: 0.26 mg/mL of USP Fosamprenavir System Suitability Mixture RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Standard solution: 0.26 μg/mL of USP Fosamprenavir Calcium RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Sample solution: 0.26 mg/mL of Fosamprenavir Calcium in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

4.2.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 266 nm

Column: 4.6-mm × 15-cm; 3.5-μm packing L1

Column temperature: 40°

Flow rate: 1 mL/min

Injection volume: 20 μL

4.2.2 System suitability

Samples: System suitability solution and Standard solution

4.2.3 Suitability requirements

Resolution: NLT 2 between fosamprenavir and fosamprenavir n-butyl isomer, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

4.2.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any individual late-eluting impurity in the portion of Fosamprenavir Calcium taken:

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × 100

r_U = peak response of any individual impurity from the Sample solution

r_S = peak response of fosamprenavir from the Standard solution

C_S = concentration of USP Fosamprenavir Calcium RS in the Standard solution (mg/mL)

C_U = concentration of Fosamprenavir Calcium in the Sample solution (mg/mL)

F = relative response factor (see Table 3)

Acceptance criteria: See Table 3. The reporting threshold is 0.03%.

Table 3

^a Calcium (2R,3S)-1-[(4-amino-N-butylphenyl)sulfonamide]-4-phenyl-3-[({[(S)-tetrahydrofuran-3-yl]oxy}carbonyl)amino]butan-2-yl phosphate.

^b Ethyl {(2S,3R)-4-[(4-amino-N-isobutylphenyl)sulfonamide]-1-phenyl-3-(phosphonooxy)butan-2-yl}carbamate.

^c Bis[(3S)-tetrahydro-3-furanyl] (3S,4R,12R,13S)-4,12-bis({[(4-aminophenyl)sulfonyl](2-methylpropyl)amino}methyl)-6,8,10-trihydroxy-3,13-bis(phenylmethyl)-5,7,9,11-tetroxa-2,14-diaza-6,8,10triphosphapentadecanedioate 6,8,10-trioxide.

^d Bis[(3S)-tetrahydro-3-furanyl] (3S,4R,10R,11S)-4,10-bis({[(4-aminophenyl)sulfonyl](2-methylpropyl)amino}methyl)-6,8-dihydroxy-3,11-bis(phenylmethyl)-5,7,9-trioxa-2,12-diaza-6,8-diphosphatridecanedioate 6,8-oxide.

^e(3S)-Tetrahydro-3-furanyl (3S,4R)-4-({[(4aminophenyl) sulfonyl]isobutylamino}methyl)-6-[(4S,5R)-5-({[(4-aminophenyl) sulfonyl] isobutylamino}methyl) - 2-oxo-4-benzyl-3-oxazolidinyl]-8,8-dihydroxy-6-oxo-3-benzyl-5,7-dioxa-2-aza-6,8-diphosphaoctanoate 8-oxide.

^f 4-Amino-N-{[(4S,5R)-4-benzyl-2-oxooxazolidin-5-yl]methyl}-N-isobutylbenzenesulfonamide.

^g(S)-Tetrahydrofuran-3-yl {(2S,3R)-4-[(4-amino-N-isobutylphenyl)sulfonamide]-3-hydroxy-1-phenylbutan-2-yl}carbamate.

^h Exclude any individual unspecified impurity that elutes before fosamprenavir.

ⁱ Total impurities include the sum of all impurities determined in Organic Impurities: Early-Eluting Impurities, Organic Impurities: Late-Eluting

Impurities, and Limit of Fosamprenavir Related Compound A.

4.3 Limit of Fosamprenavir Related Compound A

Buffer: 1.54 g/L of ammonium acetate in water. Adjust with glacial acetic acid to a pH of 4.0.

Solution A: 0.5 mL/L of trifluoroacetic acid in water

Solution B: 0.5 mL/L of trifluoroacetic acid in acetonitrile

Mobile phase: See Table 4.

Table 4

Diluent: Methanol and Buffer (50:50)

Sensitivity solution: 0.3 μg/mL of USP Fosamprenavir Calcium RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Standard solution: 0.003 mg/mL of USP Fosamprenavir Related Compound A RS in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

Sample solution: 1 mg/mL of Fosamprenavir Calcium in Diluent. Sonicate to dissolve prior to final dilution, if necessary.

4.3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 266 nm

Column: 4.6-mm × 15-cm; 3.5-μm packing L1

Column temperature: 30°

Flow rate: 1 mL/min

Injection volume: 10 μL

4.3.2 System suitability

Samples: Sensitivity solution and Standard solution

[Note - The relative retention times for fosamprenavir and fosamprenavir related compound A are 1.0 and 3.6, respectively.]

4.3.3 Suitability requirements

Tailing factor: NMT 2, Standard solution

Relative standard deviation: NMT 5.0%, Standard solution

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

4.3.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of fosamprenavir related compound A in the portion of Fosamprenavir Calcium taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of fosamprenavir related compound A from the Sample solution

r_S = peak response of fosamprenavir related compound A from the Standard solution

C_S = concentration of USP Fosamprenavir Related Compound A RS in the Standard solution (mg/mL)

C_U = concentration of Fosamprenavir Calcium in the Sample solution (mg/mL)

Acceptance criteria: NMT 0.3% of fosamprenavir related compound A

5 SPECIFIC TESTS

Change to read:

 Water Determination 〈921〉, Method I: NMT 14.5% (RB 1-Feb-2023)

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers. Store at controlled room temperature.

USP Reference Standards 〈11〉

USP Fosamprenavir Calcium RS

USP Fosamprenavir Related Compound A RS

Calcium (6R,7S,16S,17R)-4,19-bis[(4-aminophenyl)sulfonyl]-7,16-dibenzyl-2,21-dimethyl-9,14-dioxo-10,13-dioxa-4,8,15,19-tetraazadocosane-6,17-diyl bis(phosphate).

C₄₄H₅₈Ca₂N₁₆O₆P₂S₂ 1133.20

USP Fosamprenavir System Suitability Mixture RS

A mixture of fosamprenavir calcium, fosamprenavir pyrophosphate, fosamprenavir n-propyl homolog, and fosamprenavir n-butyl isomer. Other impurities may also be present.