In vitro characterization of MK-1439, a novel HIV-1 nonnucleoside reverse transcriptase inhibitor

Abstract

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are a mainstay of therapy for treating human immunodeficiency type 1 virus (HIV-1)-infected patients. MK-1439 is a novel NNRTI with a 50% inhibitory concentration (IC50) of 12, 9.7, and 9.7 nM against the wild type (WT) and K103N and Y181C reverse transcriptase (RT) mutants, respectively, in a biochemical assay. Selectivity and cytotoxicity studies confirmed that MK-1439 is a highly specific NNRTI with minimum off-target activities. In the presence of 50% normal human serum (NHS), MK-1439 showed excellent potency in suppressing the replication of WT virus, with a 95% effective concentration (EC95) of 20 nM, as well as K103N, Y181C, and K103N/Y181C mutant viruses with EC95 of 43, 27, and 55 nM, respectively. MK-1439 exhibited similar antiviral activities against 10 different HIV-1 subtype viruses (a total of 93 viruses). In addition, the susceptibility of a broader array of clinical NNRTI-associated mutant viruses (a total of 96 viruses) to MK-1439 and other benchmark NNRTIs was investigated. The results showed that the mutant profile of MK-1439 was superior overall to that of efavirenz (EFV) and comparable to that of etravirine (ETR) and rilpivirine (RPV). Furthermore, E138K, Y181C, and K101E mutant viruses that are associated with ETR and RPV were susceptible to MK-1439 with a fold change (FC) of <3. A two-drug in vitro combination study indicated that MK-1439 acts nonantagonistically in the antiviral activity with each of 18 FDA-licensed drugs for HIV infection. Taken together, these in vitro data suggest that MK-1439 possesses the desired properties for further development as a new antiviral agent.

FIG 1

Structures of MK-1439 (A), EFV (B), RPV (C), and ETR (D).

FIG 2

Susceptibility of mutant viruses containing NNRTI-associated mutants to NNRTIs. (A) MK-1439; (B) EFV; (C) RPV; (D) ETR. An asterisk indicates that the EC₅₀ was not reached at highest concentration tested. CNDO is a drug-sensitive reference standard that is used to determine the fold changes in drug susceptibility of patient samples. The EC₅₀ were 1, 0.9, 0.6, and 2.4 nM for EFV, RPV, ETR, and MK-1439, respectively, against CNDO. MDRC4 is a multidrug-resistant virus control that is used to evaluate and monitor assay performance. The fold change was defined by the ratio of EC₅₀ between the mutant virus and CNDO. The EC₅₀ was obtained from a single compound titration (n = 1).

FIG 3

Susceptibility of a panel of 96 clinically relevant NNRTI-associated mutant viruses to NNRTIs. (A) MK-1439; (B) EFV; (C) RPV; (D) ETR.

FIG 4

Susceptibility of EFV, ETR, and RPV Resistant Viruses to MK-1439. (A) MK-1439- versus EFV-resistant viruses; (B) MK-1439- versus RPV-resistant viruses; (C) MK-1439- versus ETR-resistant viruses.

FIG 5

Susceptibility of RPV-associated mutant viruses to NNRTIs. Black bar, EFV; gray bar, RPV; cross-hatched bar, ETR; open bar, MK-1439. The experiments were repeated at least 3 times. Fold changes are in means ± standard deviations.

FIG 6

Mean three-dimensional plot of MK-1439 and other antiviral agents in the two-drug combination study. (A) MK-1439 and FTC; (B) MK-1439 and TDF; (C) MK-1439 and RAL; (D) MK-1439 and DRV.