Merck’s HIV-1 Drugs Delstrigo and Pifeltro Get FDA Approval

Fixed-dose combination tablet and new non-nucleoside reverse transcriptase inhibitor are two new antiretroviral treatment options.

With the recent approval by the US Food and Drug Administration (FDA) of two new drugs from Merck & Co. (known as MSD outside the United States and Canada), patients now have access to even more treatment options. 

Delstrigo is a once-daily fixed-dose combination tablet of doravirine, lamivudine and tenofovir disoproxil fumarate. Pifeltro (doravirine) is a new non-nucleoside reverse transcriptase inhibitor designed to be administered in combination with other antiretroviral medicines. Both are once-daily oral drugs indicated for the treatment of HIV-1 infection in adult patients with no prior antiretroviral treatment experience. 

As with other HIV medicines, these two new drugs do not cure HIV-1 infection or AIDS, and Delstrigo comes with a boxed warning regarding post-treatment acute exacerbation of hepatitis B (HBV) infection. In addition, Delstrigo and Pifeltro are contraindicated when co-administered with drugs that are strong cytochrome P450 (CYP)3A enzyme inducers, because significant decreases in doravirine plasma concentrations may occur, leading to reduced effectiveness of both drugs. Delstrigo is also contraindicated in patients with a previous hypersensitivity reaction to 3TC.

The approvals by FDA were based on the results obtained in the randomized, multicenter, double-blind, active controlled Phase 3 trials DRIVE-AHEAD and DRIVE-FORWARD, which evaluated the efficacy and safety of delstrigo and pifeltro, respectively, in participants infected with HIV-1 with no antiretroviral treatment history.


Cynthia A. Challener, Ph.D.

Dr. Challener is an established industry editor and technical writing expert in the areas of chemistry and pharmaceuticals. She writes for various corporations and associations, as well as marketing agencies and research organizations, including That’s Nice and Nice Insight.