Fosamprenavir calcium salt (GW433908G), the prodrug's calcium salt, was selected for additional research because it seemed to have the most promise for creating novel drug formulations [1].

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
No published information is available on the use of fosamprenavir during breastfeeding. Fosamprenavir is not recommended during breastfeeding. Achieving and maintaining viral suppression with antiretroviral therapy decreases breastfeeding transmission risk to less than 1%, but not zero. Individuals with HIV who are on antiretroviral therapy with a sustained undetectable viral load and who choose to breastfeed should be supported in this decision. If a viral load is not suppressed, banked pasteurized donor milk or formula is recommended.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Gynecomastia has been reported among men receiving highly active antiretroviral therapy. Gynecomastia is unilateral initially, but progresses to bilateral in about half of cases. No alterations in serum prolactin were noted and spontaneous resolution usually occurred within one year, even with continuation of the regimen. Some case reports and in vitro studies have suggested that protease inhibitors might cause hyperprolactinemia and galactorrhea in some male patients, although this has been disputed. The relevance of these findings to nursing mothers is not known. The prolactin level in a mother with established lactation may not affect her ability to breastfeed.

[1]. Pharmacokinetics of GW433908, a prodrug of amprenavir, in healthy male volunteers. J Clin Pharmacol. 2002 Aug;42(8):887-98.

Fosamprenavir (brand name: Lexiva) is a prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of HIV infection in adults and children. Fosamprenavir is always used in combination with other HIV medicines.
Although fosamprenavir is FDA-approved for use in adults and children, it is no longer commonly used or recommended as an HIV treatment. The Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents with HIV and the Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection no longer contain detailed or updated information on the use of fosamprenavir. Please refer to the FDA drug label for additional information regarding the use of fosamprenavir in people with HIV.
HIV medicines cannot cure HIV/AIDS, but taking HIV medicines every day helps people with HIV live longer, healthier lives. HIV medicines also reduce the risk of HIV transmission. If you are taking HIV medicines, do not cut down on, skip, or stop taking them unless your health care provider tells you to.
Fosamprenavir Calcium is the calcium salt form of fosamprenavir, prodrug of amprenavir, and a human immunodeficiency virus (HIV) protease inhibitor with antiviral property. Fosamprenavir is converted to amprenavir by cellular phosphatases in the epithelial cells of the intestine. Then amprenavir binds to the active site of HIV-1 protease, thereby preventing the proteolytic cleavage of viral Gag-Pol polypeptide into individual functional proteins, thereby leading to the formation of immature non-infectious viral particles.
See also: Amprenavir (has active moiety).

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Drug Indication
Telzir in combination with low-dose ritonavir is indicated for the treatment of human-immunodeficiency-virus-type-1-infected adults, adolescents and children of six years and above in combination with other antiretroviral medicinal products. , , In moderately antiretroviral-experienced adults, Telzir in combination with low-dose ritonavir has not been shown to be as effective as lopinavir / ritonavir. No comparative studies have been undertaken in children or adolescents. , , In heavily pretreated patients, the use of Telzir in combination with low-dose ritonavir has not been sufficiently studied. , , In protease-inhibitor-experienced patients, the choice of Telzir should be based on individual viral resistance testing and treatment history. ,

C25H34CAN3O9PS

623.67

623.137

226700-81-8

Fosamprenavir;226700-79-4

131535

White to off-white solid powder

282-284ºC

5.449

2

11

13

40

901

3

CC(C)CN(C[C@H]([C@H](CC1=CC=CC=C1)NC(=O)O[C@H]2CCOC2)OP(=O)([O-])[O-])S(=O)(=O)C3=CC=C(C=C3)N.[Ca+2]

PMDQGYMGQKTCSX-HQROKSDRSA-L

InChI=1S/C25H36N3O9PS.Ca/c1-18(2)15-28(39(33,34)22-10-8-20(26)9-11-22)16-24(37-38(30,31)32)23(14-19-6-4-3-5-7-19)27-25(29)36-21-12-13-35-17-21/h3-11,18,21,23-24H,12-17,26H2,1-2H3,(H,27,29)(H2,30,31,32)/q+2/p-2/t21-,23-,24+/m0./s1

calcium[(2R,3S)-1-[(4-aminophenyl)sulfonyl-(2-methylpropyl)amino]-3-[[(3S)-oxolan-3-yl]oxycarbonylamino]-4-phenylbutan-2-yl] phosphate

Lexiva GW433908G Amprenavir phosphate calcium UNII-ID1GU2627N GW 433908 GW 433908G GW 908 GW-433908 GW-433908G GW-908

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~50 mg/mL (~80.17 mM)
H2O : ~0.25 mg/mL (~0.40 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.01 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.01 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (4.01 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)