Lersivirine (UK-453061)

Lersivirine binds to HIV-1 wt reverse transcriptase (RT) with K_d of 624 nM. Lersivirine is a very weak inhibitor of human DNA polymerase beta, with an extrapolated geometric mean IC50 of approximately 20 mM resulting in a predicted selectivity index of 166,000. Lersivirine is able to inhibit HIV-1 virus replication in MT-2 cells infected with wt NL4-3, with an EC50 ranging from 5 nM to 35 nM against an MOI ranging from 0.005 to 0.5. Lersivirine retains activity against 80% of viruses with genotypes containing K103N as a single NNRTI mutation (versus 7% for efavirenz), 57% of viruses with genotypes containing Y181C as a single NNRTI mutation (43% for efavirenz), and 46% of viruses with genotypes containing G190A as a single NNRTI mutation (0% for efavirenz). Lersivirine inhibits the replication of strain Ba-L in PBL, with a geometric mean EC50 equal to 3.38 nM (95% CI, 2.26 to 5.05 nM) and an EC90 equal to 9.87 nM (95% CI, 6.63 to 14.7 nM), with no cytotoxicity observed up to 50 μM. Combinations of lersivirine with drugs of the NRTI class (abacavir, didanosine, emtricitabine, lamivudine, tenofovir, and zidovudine) results in synergistic interactions. ^[1]

Lersivirine is not teratogenic in mice.^[3]

• RT enzyme assays

  The activities of lersivirine and efavirenz against wt RT (BH10 strain) are determined using a primer extension assay incorporating a DNA/RNA primer/template. The 5’biotinylated primer DNA is a 16mer oligo(dT), which is annealed to a poly(rA) template of approximately 300 bases in length. Incorporation of [³H]TTP(dTTP) by reverse transcription results in extension of the primer. During the reaction the primer/template is bound to a streptavidin-coated flashplate (NEN). The incorporated tritiated nucleotides can then stimulate the scintillant to produce a signal that is measured using a scintillation counter. Compounds that inhibit the RNA-dependent DNA polymerase activity of RT produce a reduced signal.

• Cell lines

  SupT1 cells

• Concentrations

  increasing concentrations from 5 nM

• Incubation Time

  Every 7 days

• Method

  For inhibitor escalation studies, SupT1 cells are initially infected with HIV-1 NL4-3 wt for 1 h at 37°C and the virus-infected cells are passaged weekly in SupT1 cells in the presence of increasing concentrations of lersivirine from a starting concentration of 5 nM (IC50 in this assay system) in 12-well plates (6 × 10⁵ cells/well). Throughout the passaging period, ongoing virus replication is monitored weekly by observing cytopathic effects (syncytia). Every 7 days, virus supernatant is passaged onto fresh cells at the same density with fresh lersivirine-containing medium. The concentration of lersivirine is increased by 2-fold and 5-fold that of the previous concentration upon subsequent passage whenever evidence of viral replication is observed. Virus stocks for phenotypic characterization are produced in SupT1 cells in the absence of compound and are tested for their sensitivity to lersivirine in an antiviral assay using HeLaP4 cells.

• Animal Models

  Mated Crl:CD1(ICR) mice

• Dosages

  150 mg/kg, 350 mg/kg, 500 mg/kg

• Administration

  Oral gavage