fostemsavir FTR (AI)
Standard DoseOne tablet twice daily, with or without food. For heavily treatment-experienced people with multidrug-resistant virus on a failing HIV regimen due to resistance, intolerance, or safety considerations. Must be taken in combination with another antiretroviral(s).
Take missed dose as soon as possible, unless it is closer to the time of your next dose. Do not double up on your next dose. Tablet should be swallowed whole; do not chew, crush, or split tablets.
- See package insert for more complete information on potential side effects and interactions.
Potential Side Effects and Toxicity
At the time of approval in 2020, the most common side effect was nausea in 10% of study participants. Other side effects, observed less often, were diarrhea, fatigue, and headache. Use with caution in people who have a history of QTc prolongation (these abnormal heart rhythms can make the heart stop). Liver problems can occur, but are very rare. The risk may be greater for people with a history of hepatitis B or C, but may occur in people without a history of liver disease.
Potential Drug Interactions
Dose modification of fostemsavir is not required when co-administering with atazanavir/ritonavir (Reyataz + Norvir), cobicistat (Tybost), darunavir/cobicistat (Prezcobix), darunavir/ritonavir (Prezista + Norvir) with and without etravirine (Intelence), maraviroc (Selzentry), raltegravir (Isentress HD), ritonavir, or tenofovir DF (found in Truvada). Dose modification is also not required when co-administering with buprenorphine/naloxone, famotidine, methadone, norethindrone, or rifabutin (with or without ritonavir). It is not recommended to co-administer with rifampin, an antimycobacterial used for tuberculosis treatment, due to significantly reduced levels of fostemsavir. Cannot be taken with (contraindicated with) enzalutamide (an androgen receptor inhibitor), the anticonvulsants carbamazepine and phenytoin, the cancer drug mitotane, or the herb St. John’s wort. Fostemsavir increases concentrations of statins (medications that treat cholesterol). Use the lowest possible starting dose for statins and monitor for statin-associated adverse effects. Rukobia should be used with caution when taken with other medications with a known risk for torsades de pointes or QT prolongation (these abnormal heart rhythms can make the heart stop). Fostemsavir could affect oral contraceptive concentrations, especially those containing ethinyl estradiol. If a booster is not given in the regimen with fostemsavir, it may be co-administered with a combined oral contraceptive containing norethindrone and 30 mcg or less of ethinyl estradiol. It cannot be taken by trans women on estrogen hormone therapy due to the significantly increased risk for a blood clot. May increase levels of the hepatitis C virus (HCV) drugs grazoprevir and voxilaprevir; however, the magnitude of increase in exposure is currently unknown. Increased levels of grazoprevir may increase the risk of liver enzymes. Use an alternative HCV regimen if possible. Tell your provider or pharmacist about all medications, herbals, and supplements you are taking or thinking of taking, prescribed or not, as there may be other drug interactions which are not listed here.
Rukobia is designed to be used in highly treatment-experienced people, who typically have fewer options for HIV treatment than those just starting antiretroviral therapy. An option for treatment-experienced individuals is a good thing. “Even in the era of modern HAART [highly active antiretroviral therapy], antiretroviral [ARV] failure and resistance is still a problem worldwide,” wrote HIV specialist Dr. Pedro Cahn and colleagues in Current Opinion in HIV and AIDS published July 2018. Dr. Cahn worked on fostemsavir research. Rukobia is a gp120 attachment inhibitor. A member of the drug class of HIV entry inhibitors, Rukobia works on the gp120 envelope protein that lies on the surface of the virus. It’s a necessary part of getting the virus to enter the cell. Rukobia prevents attachment to the CD4 immune cell by blocking gp120 from binding to the CD4 receptor binding sites. This causes the virus to accumulate in extracellular space and is subsequently removed by the body’s immune system. Watch a video of its mechanism of action at youtu.be/WnreXE-TVi8. Given that Rukobia does not appear to have cross-resistance to any currently approved antiretroviral, as well as its activity regardless of HIV tropism, it is a welcome new drug for people with very limited treatment options. Rukobia is active against CCR5, CXCR4, and dual-mixed virus (Selzentry is only active against CCR5). For individuals with HIV-2, commonly found in some other countries, Rukobia would not be recommended, as HIV-2 is inherently resistant to it. For more data, including medications added for optimized therapy. Go to the FDA approval announcement at fda.gov/news-events/press-announcements/fda-approves-new-hiv-treatment-patients-limited-treatment-options. Pregnant individuals can voluntarily enroll in the Antiretroviral Pregnancy Registry through their provider; go to apregistry.com.
Dr. Melanie Thompson:
Fostemsavir is a first-in-class oral attachment inhibitor that prevents HIV from entering the T-cell. It is active against HIV that is resistant to all other classes and approved only for people who are treatment-experienced. The drug must be taken twice daily, but is generally well tolerated, with mild nausea as the most common side effect. Fostemsavir should not be taken with the androgen receptor inhibitor enzalutamide, some seizure and tuberculosis medicines, mitotane, and St. John’s wort. It can increase plasma concentrations of the hepatitis C drugs grazoprevir and voxilaprevir, the oral contraceptive ethinyl estradiol (a maximum dose of 30 mcg is recommended), and most of the statins. Fostemsavir should not be used in pregnancy due to insufficient safety data.
Fostemsavir is the most expensive oral HIV drug with a wholesale acquisition cost of $8,027 per month, likely due to the relatively small market for the drug. There is a patient assistance program for people with commercial insurance that is intended to make the drug affordable to people despite high cost.
Activist Joey Wynn:
Rukobia (fostemsavir) is the first drug in a new class called attachment inhibitors. This is a vital choice for those heavily treatment-experienced individuals who are running out of options. This is for use only in highly treatment-experienced people, so definitely not a choice if this is your first time choosing the right regimen.