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New Drugs

Lauren Howell, PharmD

Molecular model of a Human Immunodeficiency Virus Type 1 (HIV-1).

In December 2022, FDA approved Sunlenca (Gilead Sciences, Inc.), the first medication in a new class of drugs used to treat HIV type 1 (HIV-1) in patients who are unable to be successfully treated with other available medications.

For heavily treatment-experienced adults with multidrug-resistant HIV-1 infection failing their current antiretroviral regimen due to resistance, intolerance, or safety considerations, Sunlenca offers the potential for a longer, healthier life.

Recommended dosage and how it works

Sunlenca (lenacapavir) is an HIV-1 capsid inhibitor that works by blocking the protein shell of the virus, interfering with multiple essential steps of the viral lifecycle. It is currently available as a 300 mg tablet and a 463.5 mg/1.5 mL single-dose vial for injection. Injected doses must be administered by a health care provider. Treatment with Sunlenca can be initiated through either of two methods, followed by a maintenance dose every 6 months.

The first option for initiation dosing is 927 mg by S.C. injection and 600 mg orally on day 1, followed by 600 mg orally on day 2. The second option is 600 mg orally on day 1, 600 mg orally on day 2, 300 mg orally on day 8, and 927 mg by S.C. injection on day 15.

Once initiation dosing has been completed, the maintenance dose is 927 mg by S.C. injection every 6 months from the date of the last injection, with a flexibility window of +/- 2 weeks. If more than 28 weeks have passed since the last injection, patients must restart with initiation dosing again.

Drug interactions

Lenacapavir is a substrate of P-gp, UGT1A1, and CYP3A. Concomitant administration of Sunlenca with strong CYP3A inducers is contraindicated due to decreased lenacapavir plasma concentrations, leading to loss of effect and development of resistance to Sunlenca. Use of Sunlenca concomitantly with moderate CYP3A inducers is also not recommended. Concomitant administration of Sunlenca with combined P-gp, UGT1A1, and strong CTP4A inhibitors is not recommended due to the possibility of significantly increased plasma concentrations of Sunlenca. Because lenacapavir has a long half-life and is a moderate inhibitor of CYP3A, it may increase the exposure of drugs primarily metabolized by CYP3A initiated within 9 months after the last S.C. dose of Sunlenca.

Examples of drug classes with which interactions may occur include antiarrhythmics, anticoagulants, anticonvulsants, antiretroviral agents, antimycobacterials, systemic corticosteroids, ergot derivatives, herbal products, HMG-CoA reductase inhibitors, narcotic analgesics, opioid antagonists, phosphodiesterase-5 inhibitors, and sedatives/hypnotics. Based on drug interaction studies that have been conducted, no clinically significant interactions have been observed with darunavir/cobicistat, cobicistat, famotidine, pitavastatin, rosuvastatin, tenofovir alafenamide, or voriconazole.

Adverse effects

The most common adverse reactions in patients being treated with Sunlenca are nausea and injection site reactions. Immune reconstitution syndrome and injection site reactions may occur. Residual concentrations of lenacapavir may remain in systemic circulation for up to 12 months or longer. Lack of adherence may result in loss of virologic response and development of resistance. If treatment with Sunlenca is discontinued, a fully suppressive antiretroviral regimen should initiated no later than 28 weeks after the final injection.

Clinical trials

The safety and efficacy of Sunlenca were established through a multicenter clinical trial with 72 patients. All patients had HIV infections that were resistant to multiple classes of HIV medications and had high levels of the virus in their blood despite their current antiretroviral therapy. Patients were randomized into one of two study groups and either received Sunlenca or a placebo. Of the patients who received Sunlenca, 87.5% achieved a certain level of reduction in virus during the initial 14 days of therapy compared to 16.7% of patients who received placebo. After 26 weeks of therapy with Sunlenca, 81% of participants achieved HIV RNA suppression. After 52 weeks, 83% of participants continued to have HIV RNA suppression.

Patient counseling

Patients being treated with Sunlenca should be counseled on potential drug interactions and encouraged to report the use of any other prescription or nonprescription medication or herbal products to their health care provider. Patients should be advised to inform their health care provider immediately of any signs or symptoms of infection. Lastly, patients should be counseled on the importance of medication adherence to maintain viral suppression and reduce the risk of developing resistance. Patients should tell their health care provider immediately if they stop taking Sunlenca or any other drug in their antiretroviral regimen. ■



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