HIV Reverse transcription (IC50 = 119 nM); NNRTI
Non-nucleoside HIV reverse transcriptase inhibitor (NNRTI) (HIV-1 wild-type reverse transcriptase (RT) IC50 = 0.119 μM) [1]

In line with the promising results seen against isolated RT enzymes, lerivirine shows outstanding efficacy against a variety of drug-resistant and wild-type HIV strains. [1]
Lersivirine is a second-generation NNRTI undergoing clinical development for the treatment of HIV-1. Lersivirine is structurally divergent from efavirenz and binds the RT enzyme in a novel way [2].

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Lersivirine (UK-453061) exhibited potent inhibition of HIV-1 reverse transcriptase (RT) with an IC50 of 0.119 μM. [1]
Lersivirine (UK-453061) demonstrated potent antiviral activity in cell culture against the RF strain of HIV-1 in SupT1 cells with an IC50 (AVE50) of 4.9 nM. [1]
Lersivirine (UK-453061) displayed a favorable resistance profile against a panel of mutant RT enzymes, showing relatively low fold-resistance changes compared to wild-type RT for several key mutations, such as K103N (1.6-fold), Y181C (2.7-fold), and F227L (5.0-fold). [1]
Lersivirine (UK-453061) showed a cytotoxic concentration (CC50) of >30 μM in SupT1 cells, indicating a high therapeutic index in vitro. [1]

Lersivirine causes skeletal variations in mated Crl:CD1(ICR) mice, which are linked to developmental delays and reduced fetal ossification. Lersivirine (oral gavage; 0, 150, 350, and 500 mg/kg; once daily; days 6 to 17 of gestation, followed by caesarean section on day 18 of gestation) induces hepatic metabolic enzymes at 250 mg for the first 2 days/ kg, followed by increasing the dose to 500 mg/kg/day.

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Maternal and Cesarean Section Observations [2]
There was no effect of treatment on maternal survival, abortion, or early delivery; 21, 19, 18, and 22 females carried a litter to term at 0, 150, 350, and 500 mg/kg/day, respectively (Table 1). Body weights and body weight gains were unaffected by lersivirine treatment; GD 18 body weights were 100, 99, and 102% of controls at 150, 350, and 500 mg/kg/day, respectively (Table 2). Feed consumption was decreased at 350 and 500 mg/kg/day (Table 2). Feed consumption for the entire dosage period (GD 6–18) was significantly lower (p < 0.05 or p < 0.01) than the concurrent control group values at 350 and 500 mg/kg/day (92 and 90%, respectively, of the control).

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Fetal Morphology [2]
There were no external, visceral, or skeletal malformations associated with maternal lersivirine treatment (Table 4). A medial cleft in the palate was observed at external examination for three fetuses (1.3%/litter) at 350 mg/kg/day and three fetuses (1.1%/litter) at 500 mg/kg/day; however, given the background incidence in this laboratory ranges to 3.2% per litter, the occurrence was not considered lersivirine-related. Rotated fore- and/or hindlimbs were noted in five (2.1%/litter), four (1.6%/litter), five (2.1%/litter), two (0.7%/litter) at 0, 150, 350, and 500 mg/kg/day, respectively; however, given the lack of a dose-response increase in incidence, this finding was not attributed to lersivirine. The only skeletal malformation that occurred in the 500 mg/kg/day group was fused lumbar arch in two (1.4%/litter) fetuses, given the lack of other evidence of skeletal dysmorphogenesis this occurrence in two fetuses from a single litter was not attributed to lersivirine.

The reverse transcriptase (RT) inhibition assay measured the IC50 values of compounds against wild-type and mutant HIV-1 RT enzymes. The assay details have been reported separately. [1]
The in vitro dofetilide binding assay was used to assess potential hERG channel inhibition as an indicator of ion channel selectivity and off-target pharmacology. [1]

Antiviral activity (IC50, AVE50) was determined in cell culture using SupT1 cells infected with the RF strain of HIV-1. The assay details have been reported separately. [1]
Cytotoxicity (CC50) was evaluated in SupT1 cells to assess the compound's potential toxic effects. [1]

Animals and Treatment [2]
One hundred presumed pregnant female Crl:CD1(ICR) mice were randomly assigned to four groups of 25 mice per group. Sixty-three additional presumed pregnant mice were assigned for use in toxicokinetic sample collection; control group of 9 and 18 per group for lersivirine dose groups. Mice were approximately 72 days of age and approximately 28 gm in weight upon arrival. Mice were individually housed in stainless steel, wire-bottomed cages. Water and feed were given ad libitum and the room was on a 12-hr light/dark cycle.
Suspensions of lersivirine in 0.5% methylcellulose aqueous solution with 0.1% Tween 80 were administered orally via gavage once daily on days 6 through 17 of presumed gestation (gestation days 6–17) at doses of 0, 150, 350, and 500 mg/kg/day at a dosage volume of 10 ml/kg. At the highest dose tested (500 mg/kg/day), an initial dose of 250 mg/kg/day at a dosage volume of 5 ml/kg was administered for the first 2 days of dosage administration after which the mice were treated at 500 mg/kg/day. This dosing regimen allowed for maintenance of the maximum tolerable exposure following metabolizing enzyme induction; lersivirine has previously been shown to induce metabolism in rodents (Walker et al., 2009). The doses were based on a preliminary study in which pregnant mice (10/group) were dosed from GD 6 to 17 at doses of 150, 350, and 700 mg/kg/day (the 700 mg/kg/day group was dosed the first 2 days at 350 mg/kg/day). In this study, 4 of 10 mice in the 700 mg/kg/day group were euthanized moribund; all other animals survived until the scheduled euthanasia. Therefore, 500 mg/kg/day (with first 2 dose days at 250 mg/kg/day) was estimated to be the maximum tolerated dose in pregnant mice.

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Assessment of Lersivirine Exposure [2]
On GD 17, blood samples (approximately 0.5 ml) were collected from the vena cava of three mice/group/time point after sacrifice. For lersivirine-treated mice, samples were collected before dosage and at approximately 0.5, 2, 4, 8, and 24 hr post-dose. Blood samples were transferred into lithium heparin–coated tubes, plasma was separated from whole blood by centrifugation and stored frozen at –20°C until analyzed. Plasma concentrations of lersivirine were determined by a validated HPLC assay.

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Rat pharmacokinetic studies were conducted. Lersivirine (UK-453061) was administered intravenously (iv) at a dose of 2 mg/kg. Blood samples were collected over time to determine pharmacokinetic parameters. [1]

Maternal toxicokinetics [2] Table 6 lists the plasma concentrations of lersivirine on day 17 of pregnancy following administration from day 6 to day 17 of pregnancy. Maternal plasma lersivirine exposures were similar across the three dose groups. In human liver microsomes (HLM), the half-life (T1/2) of lersivirine (UK-453061) was greater than 30 minutes. [1] In human hepatocyte assays, the expected free clearance (CLb) was 7 mL/min/kg. [1] In a rat pharmacokinetic study at an intravenous dose of 2 mg/kg, the clearance (CL) of lersivirine (UK-453061) was 25.9 mL/min/kg, the volume of distribution (Vd) was 1.6 L/kg, and the half-life (T1/2) was 1.6 hours. This is an improvement over the previous lead compound 3, which had a higher clearance (>100 mL/min/kg) and a shorter half-life (0.1 h). [1]
Lersivirine (UK-453061) has good water solubility and formulation properties. [1]

Lercilvirine is a second-generation non-nucleoside reverse transcriptase inhibitor currently in clinical development for the treatment of HIV-1. This study conducted an embryo-fetal developmental toxicity study to evaluate the maternal and developmental toxicity of lercilvirine in pregnant mice. Mated Cr1:CD1 (ICR) mice were administered 0, 150, 350, and 500 mg/kg of lercilvirine once daily by gavage from day 6 to 17 of gestation, followed by cesarean section on day 18 of gestation. The high-dose group received 250 mg/kg for the first two days to induce the expression of hepatic metabolic enzymes, after which the dose was increased to 500 mg/kg/day. This dosing regimen maintained drug exposure in the high-dose group even after significant autoinduction in rodents following lercilvirine treatment. Lercilvirine did not cause an increase in external, visceral, or skeletal malformations. Intrauterine growth retardation, manifested as reduced fetal weight and increased variability associated with delayed skeletal ossification, was observed at doses of 350 and 500 mg/kg/day. These results indicate that lecithin is nonteratogenic in mice. [2]

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Levivirin (UK-453061) exhibited a cytotoxic concentration (CC50) of >30 μM in SupT1 cells. [1]
In the dofetilide binding assay, the IC50 of lecithin (UK-453061) was 6% displacement, indicating a low inhibitory potential for hERG channels at the tested concentration. [1]
The microsomal free fraction of lecithin (UK-453061) was 80%, indicating that a considerable portion of the free drug was available for metabolism in the microsomal stability assay. [1]

[1]. Pyrazole NNRTIs 4: selection of UK-453,061 (lersivirine) as a development candidate. Bioorg Med Chem Lett. 2009 Oct 15;19(20):5857-60.

[2]. Developmental toxicity study of lersivirine in mice. Birth Defects Res B Dev Reprod Toxicol. 2012 Jun;95(3):225-30.

Lercilvirine is an aromatic ether. Lercilvirine has been used in clinical trials for the treatment of HIV-1. Lercilvirine is a new-generation pyrazole non-nucleoside reverse transcriptase inhibitor. Lercilvirine remains active against HIV viruses with mutations at the Y181 site, which lead to resistance to efavirenz, etravirine, and nevirapine. The results of this study indicate that ercilvirine is not teratogenic in mice. Furthermore, ercilvirine is also not teratogenic in rabbits (Campion et al., concurrently). The results of the ercilvirine study, combined with the absence of significant teratogenic signals observed with other first-generation non-nucleoside reverse transcriptase inhibitors (NNRTIs) such as deraviridine and nevirapine (Watts et al., 2004), support the conclusion that if the teratogenic signal of efavirenz (Lewis-Hall, 2005; Mofenson, 2005) truly exists, it is limited to that compound and does not represent a general effect of NNRTIs. Although lecivirine treatment did not cause fetal malformations, developmental toxicity was observed in fetuses born to mothers treated with lecivirine at doses of 350 and 500 mg/kg/day. The main manifestation of developmental toxicity was intrauterine growth retardation, specifically manifested as reduced fetal weight, increased skeletal variation, and reduced ossification sites. The increased skeletal variation was primarily associated with delayed ossification and rib hypoplasia. Skeletal variation refers to skeletal changes common in the experimental species and strains that represent reversible developmental delays or accelerations. This differs from fetal malformations, which are irreversible changes occurring at a low incidence in the species and strain. The primary indicator of intrauterine growth retardation was fetal weight. At doses of 350 and 500 mg/kg/day, fetal weight was 16% and 21% lower than in the control group, respectively; however, at a dose of 150 mg/kg/day, there was no change in fetal weight. In addition to reduced fetal weight, maternal skeletal variations suggestive of developmental delay at doses of lecivirine (350 mg/kg/day) included incomplete ossification of the supraoccipital, nasal, frontal, cervical arch, pubis, or ischium, as well as absence of the supraoccipital bone. Furthermore, reduced ossification of the hyoid, caudal, central sternal, forelimb phalanges, hindlimb tarsi, and hindlimb phalanges was observed in both the 350 and 500 mg/kg/day groups. Delayed ossification is well-known to be associated with reduced fetal weight in mice (Deol and Truslove, 1957; McLaren and Michie, 1958), while reduced fetal weight is not considered to be associated with the pathogenesis of structural malformations (Grüneberg, 1955). Besides intrauterine growth retardation, two stillbirths were also observed in the 500 mg/kg/day dose group. No other evidence of impaired fetal survival was found; the number of surviving fetuses was comparable across groups, and lecivirine treatment was not associated with an increase in the number of resorbed fetuses. However, given the historically low stillbirth rate, a potential association with treatment cannot be ruled out. With repeated daily administration starting on day 6 of gestation, maternal plasma exposure to lecivirine remained essentially stable by day 17 of gestation as the dose increased from 150 mg/kg/day to 500 mg/kg/day (approximately three-fold). Lecivirine is characterized by moderate clearance and volume of distribution, resulting in good oral bioavailability, with complete clearance occurring in the liver (Allan et al., 2008). However, in rodents, lecivirine administration induces hepatic enzymes, and this self-induction limits the systemic exposure achievable at steady state (Walker et al., 2009). The degree of self-induction resulted in an 8- to 10-fold decrease in the area under the curve (AUC) at 0–24 hours between days 1 and 12 post-administration in mice (Walker et al., 2009). Therefore, although the exposures were largely similar across the dose groups on day 17 (GD 17), the exposures on day 1 within the same dose range showed an increase of approximately 5-fold and 10-fold in Cmax and AUC (0–24 hr), respectively (from unpublished data from a 1-month toxicology study). Therefore, although not measured in this study, lecivirine exposure in this dose range may increase dose-proportionately during early organogenesis, and this increase was not reflected in the measurements on day 17, and the differences in exposure between different dose levels may be toxicologically significant. In summary, the results of this study indicate that lecivirine treatment does not cause fetal malformations in mice. The main effect of maternal exposure to lecivirine was intrauterine growth retardation, manifested as reduced fetal weight and skeletal variations associated with delayed ossification. [2]

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We prepared three independent groups of potent nonnucleoside HIV reverse transcriptase inhibitors (NNRTIs) based on the recently reported 3-cyanophenoxypyrazole lead compound 3. Several of these compounds exhibited promising anti-HIV activity, safety, pharmacokinetic, and pharmacological properties in vitro. We describe our analysis and conclusions regarding the selection of alcohol compound 5 (UK-453,061, lecivirine) for clinical development. [1]

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Levivirine (UK-453061) was selected from a range of pyrazole NNRTIs as a candidate for clinical development based on its compelling overall in vitro properties, including potent anti-HIV activity, good resistance, good metabolic stability, and improved pharmacokinetic properties. [1]
This drug is designed to have broad-spectrum activity against HIV strains with clinically significant resistance mutations, reduce the burden of medication, minimize the risk of side effects and drug interactions, and improve tolerability compared to existing non-nucleoside reverse transcriptase inhibitors (NNRTIs). [1]
Clinical trials have been initiated to evaluate its potential for treating HIV infection. [1]

C17H18N4O2

310.3504

310.142

C, 65.79; H, 5.85; N, 18.05; O, 10.31

473921-12-9

147362-57-0 (Loviride); 16837-52-8 (Oxymatrine）

16739244

Light yellow to khaki solid powder

1.2±0.1 g/cm3

455.4±45.0 °C at 760 mmHg

229.2±28.7 °C

0.0±1.2 mmHg at 25°C

1.595

3.3

1

5

6

23

456

0

MCPUZZJBAHRIPO-UHFFFAOYSA-N

InChI=1S/C17H18N4O2/c1-3-15-17(16(4-2)21(20-15)5-6-22)23-14-8-12(10-18)7-13(9-14)11-19/h7-9,22H,3-6H2,1-2H3

5-((3,5-diethyl-1-(2-hydroxyethyl)-1H-pyrazol-4-yl)oxy)isophthalonitrile

UK 453061; UK-453061; UK-453,061; UK453,061; Lersivirine; 473921-12-9; 3-CYANO-5-[[3,5-DIETHYL-1-(2-HYDROXYETHYL)-1H-PYRAZOL-4-YL]OXY]BENZONITRILE; UK-453,061; 5-((3,5-diethyl-1-(2-hydroxyethyl)-1H-pyrazol-4-yl)oxy)isophthalonitrile; 5-[3,5-diethyl-1-(2-hydroxyethyl)pyrazol-4-yl]oxybenzene-1,3-dicarbonitrile; R3ZGC15A9A; UK453061; UK 453,061

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~50 mg/mL (~161.11 mM)

Solubility in Formulation 1: ≥ 3 mg/mL (9.67 mM) (saturation unknown) in 10% DMSO + 40% PEG300 +5% Tween-80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 + to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)