HCV polymerase (IC50 = 0.31 μM; Ki = 52.3 nM)
IDX184 targets the HCV NS5B polymerase, which is a key enzyme in the viral replication complex responsible for the synthesis of viral RNA. The compound acts as a nucleoside polymerase inhibitor. The resistance to IDX184 is driven by mutations in the HCV polymerase, which hinder the drug's binding. IDX184 inhibits HCV polymerase with an IC50 of 0.31 μM and a Ki of 52.3 nM.

The prodrug IDX184 targets the liver and contains the nucleotide 2'-MeG-MP. Hepatitis C virus nucleotide polymerase is inhibited by IDX184, a liver-targeted medication [1]. In comparison to the parent nucleoside, IDX184 is a second-generation oral bioavailable nucleotide prodrug that is intended to offer enhanced anti-HCV efficacy and safety. IDX184 had the highest potency (EC50=0.3-0.45) among all modified nucleosides (2' or 4'; EC50=4-6 μM) in HCV replicon testing. It was also efficacious against viruses infected with JFH-1 (EC50=0.06-0.11 μM). Among the cell lines studied, IDX184 did not cause any toxicity (CC50>100μM) [2].
IDX184 potently inhibits HCV polymerase in cell-free enzymatic assays with an IC50 of 0.31 μM and a Ki of 52.3 nM. The compound is not toxic (CC50 > 100 μM) in any tested cell line, indicating a favorable selectivity index. IDX184 is a liver-targeted prodrug of the nucleotide 2'-MeG-MP.

IDX184 is a nucleotide prodrug designed to enhance formation in the liver of the active triphosphate of 2'-methylguanosine (2'-MeG), a potent and specific polymerase inhibitor of the hepatitis C virus (HCV). In the present study, single ascending oral doses of 5, 10, 25, 50, 75, and 100 mg IDX184 were administered sequentially to cohorts of 8 healthy subjects, randomized 6:2, active/placebo. Plasma and urine pharmacokinetic sampling was performed over a period of 120 h after dosing. Upon absorption, IDX184 rapidly disappeared from plasma, with a mean half-life (t(1/2)) of approximately 1 h, while plasma concentrations of 2'-MeG gradually increased. Consistent with a liver-targeting approach, plasma exposure of IDX184 and 2'-MeG was low and was also dose related: the mean maximum concentrations ranged from 1.1 to 17 ng/ml for IDX184 and 1.7 to 19 ng/ml for 2'-MeG, and the respective mean total area under the curve ranged from 1.2 to 22.7 and 17.3 to 334 ng·h/ml. Mean 2'-MeG plasma concentrations 24 h after dosing were 0.6 to 3 ng/ml for the 25- to 100-mg doses. Mean 2'-MeG t(1/2) values ranged from 18 to 43 h for doses of 25 mg and above. Mean cumulative urine excretion was 0.2% and 12 to 20% of administered doses for the unchanged IDX184 and 2'-MeG, respectively. IDX184 was safe and well tolerated; no serious adverse events (SAEs), dose-dependent adverse events (AEs), or dose-limiting toxicities were observed. The incidence of AEs and laboratory abnormalities was low and was similar among subjects receiving IDX184 or a placebo. All AEs were mild to moderate and resolved at the end of study. The favorable safety and pharmacokinetic profiles support further clinical evaluation of IDX184 in HCV-infected patients [1].
IDX184 is effective in inhibiting HCV replication in cell culture. As a liver-targeted nucleotide prodrug, it has anti-HCV activity. It is orally bioavailable and can be used in combination with pegylated interferon-α2a and ribavirin for the primary treatment of chronic hepatitis C. The compound has demonstrated potent inhibition of HCV replication in preclinical models.

The primary in vitro assay for IDX184 is a cell-free polymerase activity assay using purified HCV NS5B polymerase. The enzyme is incubated with a template-primer and nucleotide substrates in the presence of the compound. The incorporation of radiolabeled nucleotides into the growing RNA strand is measured to determine the IC50. The Ki value is determined from the inhibition kinetics. This assay directly measures the compound's ability to inhibit the enzymatic activity of the viral polymerase.

In vitro cellular experiments for IDX184 involve treating HCV replicon cell lines or HCV-infected cells with the compound. Viral replication is measured by quantifying HCV RNA levels using real-time PCR or by measuring the expression of reporter genes. The CC50 (cytotoxic concentration for 50% of cells) is determined using standard cell viability assays such as MTT or CellTiter-Glo. The selectivity index is calculated as the ratio of CC50 to IC50.

In HCV-infected chimpanzees receiving 10 mg/kg/day of IDX184 as a single agent for 4 days, the viral response at the end of treatment correlated significantly with 2′-MeG exposure but not with IDX184 exposure. Trough concentrations of 2′-MeG ranging from 2 to 8 ng/ml were associated with 1 to 4 log10 reductions in HCV RNA (6, 7). In the current study, plasma concentrations of 2′-MeG remained quite sustained, i.e., still above 2 ng/ml 24 h after a single dose of 50 to 100 mg IDX184. Steady-state trough concentrations were predicted to be around 10 ng/ml after repeat once-per-day (QD) dosing (data not shown). In light of the pharmacokinetic/pharmacodynamic (PK/PD) relationship established in the chimpanzees, a dose-dependent viral response can be anticipated with IDX184 treatment in HCV-infected patients [1].
In vivo animal experiments for IDX184 have been conducted in mouse models of HCV infection or in transgenic mice expressing HCV replication components. The compound is typically administered orally, and its effects on viral load are measured in serum and liver tissue. Pharmacokinetic parameters such as Cmax, Tmax, and half-life are determined. The liver-targeting properties are evaluated by measuring the concentration of the active metabolite in the liver versus plasma.

Plasma pharmacokinetics. [1]
IDX184 is a prodrug that delivers a monophosphate of nucleoside 2′-MeG in the liver. Plasma concentrations of the parent drug IDX184 and its nucleoside metabolite 2′-MeG were monitored. Figure 2 shows the mean (± standard deviation [SD]) plasma concentration-time curves of IDX184 (left) and 2′-MeG (right) after a single administration of 5 to 100 mg escalating doses of IDX184. Table 2 lists the pharmacokinetic parameters. After a single oral administration of IDX184 to healthy subjects on an empty stomach, the drug was rapidly absorbed, and the time to peak concentration (Tmax) was consistent with the time of first sampling in most subjects, with a cohort median of 0.25 to 0.49 hours, independent of the administered dose. Plasma exposure to IDX184 was low and proportional to the administered dose. As the dose increased from 5 mg to 100 mg, the cohort mean Cmax and AUC0-∞ varied from 1.12 to 17.3 ng/ml and 1.19 to 22.7 ng·h/ml, respectively. The pharmacokinetic dose-proportionality of IDX184 within the study dose range was assessed by regression analysis on logarithmically transformed parameters of exposure and dose. The model slope estimates for Cmax (b = 0.98; 95% CI = 0.76 to 1.21) and AUC0-∞ (b = 1.01; 95% CI = 0.85 to 1.17) were close to 1. Plasmokinetic profiles of IDX184 showed a steep clearance phase, with plasma concentrations rapidly decreasing below the limit of quantitation (0.1 ng/ml), and short but stable mean half-lives (t1/2) ranging from 0.58 to 1.06 hours across all dose groups. The cohort-normalized mean clearance (CL/F) and volume of distribution (Vd/F) ranged from 49.0 to 92.1 L/h/kg and 67.8 to 122 L/kg, respectively, regardless of the dose of IDX184. Rapid elimination of IDX184 from plasma was accompanied by the gradual appearance of 2′-MeG. Similar to the parent drug, plasma concentrations of 2′-MeG were also low, peaking at mean time to peak (Tmax) of 4.00 to 6.00 hours across all dose groups. Within the 5 to 50 mg dose range, the mean Cmax and mean C24 values of 2′-MeG increased tenfold, from 1.74 ng/ml to 18.6 ng/ml and from 0.25 ng/ml to 2.88 ng/ml, respectively. However, at higher doses, the dose-dependent relationship of these parameters weakened (Table 2). The slopes (b-values, 95% CI) obtained from dose-proportioning analysis were: Cmax 0.76 (0.60 to 0.92), C24 0.84 (0.65 to 1.03). At IDX184 doses of 50 to 100 mg, the mean Cmax and mean C24 values for 2′-MeG were 14.6 to 18.6 ng/ml and 2.23 to 2.88 ng/ml, respectively. In contrast, the mean AUC0-∞ of 2′-MeG increased 20-fold with increasing dose, from 17.3 ng·h/ml to 334 ng·h/ml, and these values were dose-proportional within the studied dose range (b = 1.04; 95% CI = 0.88 to 1.19). The mean elimination half-life (t1/2) of 2′-MeG depended on the observed elimination phase (concentration > LOQ), ranging from 5.42 to 12.2 hours at doses up to 10 mg and from 18.0 to 42.5 hours at doses ≥ 25 mg.
Based on molar concentration, the cohort mean ratio of AUC0-∞ of IDX184 to 2′-MeG was low (<4%) and independent of dose, indicating that the biotransformation of IDX184 was nearly complete and unsaturated within the dose range studied.

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Urinary excretion. [1]
Urinary excretion of parental IDX184 and its nucleoside metabolite 2′-MeG was monitored in all subjects within 120 hours after administration. Except for one sample, IDX184 was detected in urine only up to 12 hours after administration; in that sample, IDX184 was detected up to 24 hours after administration. Cumulative urinary excretion of IDX184 increased with increasing dose, but remained low across all groups, representing only 0.2% of the administered dose (Table 3). In contrast, 2′-MeG was quantifiable in all urine samples throughout the 120-hour post-dose collection period. Overall, cumulative urinary excretion of 2′-MeG increased with increasing dose (Table 3). Cumulative urinary excretion of 2′-MeG was higher than that of IDX184, representing 12% to 20% of the administered dose on a molar basis. Cumulative urinary excretion of 2′-MeG approached its maximum between 48 and 72 hours, with more than half of the total 2′-MeG excretion recovered within the first 24 hours. Renal clearance (CLR) was independent of the administered dose and remained consistent across groups, with mean values of 123 to 177 ml/min for IDX184 and 271 to 322 ml/min for 2′-MeG.
IDX184 has a molecular weight of 626.62 and a molecular formula of C25H35N6O9PS. It is orally bioavailable and is a liver-targeted nucleotide prodrug. The compound is designed to deliver the active nucleotide monophosphate specifically to the liver, where it is converted to the active triphosphate form. This liver-targeting strategy enhances efficacy and reduces systemic side effects. The prodrug is metabolized to release the active nucleotide 2'-MeG-MP.

Safety and Tolerability. [1]
Single dose of IDX184 was well tolerated. No serious adverse events (SAEs) or dose-limiting toxicities occurred. The most common adverse event (AE) was dizziness, which occurred in 2 of 36 subjects (5.6%) in the IDX184 group and in 3 of 12 subjects (25%) in the placebo group. Other less frequent adverse events were observed in both the placebo and active drug groups, including contact dermatitis, dysmenorrhea, fatigue, and headache. All reported adverse events were mild or moderate and resolved by the end of the study. There were no significant differences in the pattern of adverse events between the treatment groups. Laboratory parameters remained stable in all treatment groups. No clinically significant changes were observed in vital signs, physical examination results, or electrocardiogram parameters.
IDX184 is not toxic (CC50 > 100 μM) in any tested cell line. The compound has been evaluated in preclinical studies for its safety profile. As a nucleoside analog, its potential toxicities are related to mitochondrial toxicity or effects on host polymerases, but IDX184 has shown a favorable safety profile in preclinical evaluations. No significant toxicity has been reported in the available data.

[1]. Safety and Pharmacokinetics of IDX184, a Liver-Targeted Nucleotide Polymerase Inhibitor of Hepatitis C Virus, in Healthy Subjects. Antimicrob Agents Chemother. 2011 Jan;55(1):76-81.

[2]. IN VITRO ANTIVIRAL ACTIVITY AND PHARMACOLOGY OF IDX184, A NOVEL AND POTENT INHIBITOR OF HCV REPLICATION.

Currently, due to ethical concerns and technical challenges, it is not possible to directly assess intracellular IDX184 and its associated phosphorylated form, 2′-MeG, in humans. Although liver biopsy specimens were not obtained in this study, the degree of conversion of IDX184 to 2′-MeG-MP and its subsequent phosphates can still be approximated by the ratio of parent IDX184 to 2′-MeG plasma exposure. Despite a 20-fold dose variation, the mean molar ratio of IDX184 to 2′-MeG AUC0-∞ (2.2% to 3.8%) was consistently low across different doses, indicating near-complete conversion and that saturation was not reached at the highest IDX184 dose studied. Both parent IDX184 and its metabolite 2′-MeG are excreted in the urine. Although no formal statistical analysis was performed, the recovery of both substances in the urine appears to be dose-related. Urinary excretion of IDX184 is limited, while the cumulative urinary excretion of 2′-MeG is considerable, accounting for approximately 12% to 20% of the administered dose. Renal clearance, especially 2′-MeG clearance, was higher than normal glomerular filtration rate by 80 to 120 ml/min, indicating that the active ingredient was involved in renal clearance. In summary, single oral administration of 5 mg to 100 mg of IDX184 was safe and well-tolerated in healthy subjects in this study. The plasma concentrations of IDX184 and 2′-MeG were low after oral administration, which is consistent with the fact that IDX184 is a liver-targeted prodrug. The good safety and pharmacokinetic characteristics of IDX184 support further clinical evaluation of IDX184 in patients with HCV infection. [1]
IDX184 is a potent, orally bioavailable, liver-targeted nucleotide prodrug inhibitor of HCV NS5B polymerase. It has been investigated in combination with pegylated interferon-α2a and ribavirin for the treatment of chronic hepatitis C. The compound is a prodrug of the nucleotide 2'-MeG-MP and is designed for liver targeting. Resistance to IDX184 is driven by mutations in the HCV polymerase.

C25H35N6O9PS

626.62

626.192

C, 47.92; H, 5.63; N, 13.41; O, 22.98; P, 4.94; S, 5.12

1036915-08-8

135565589

White to off-white solid powder

1.892

6

13

14

42

1060

4

FGHMGRXAHIXTBM-TWFJNEQDSA-N

InChI=1S/C25H35N6O9PS/c1-24(2,13-32)22(35)42-10-9-38-41(37,28-11-15-7-5-4-6-8-15)39-12-16-18(33)25(3,36)21(40-16)31-14-27-17-19(31)29-23(26)30-20(17)34/h4-8,14,16,18,21,32-33,36H,9-13H2,1-3H3,(H,28,37)(H3,26,29,30,34)/t16-,18-,21-,25-,41?/m1/s1

S-[2-[[(2R,3R,4R,5R)-5-(2-amino-6-oxo-1H-purin-9-yl)-3,4-dihydroxy-4-methyloxolan-2-yl]methoxy-(benzylamino)phosphoryl]oxyethyl] 3-hydroxy-2,2-dimethylpropanethioate

IDX-184; IDX184; 1036915-08-8; Guanosine, 2'-C-methyl-, 5'-(2-((3-hydroxy-2,2-dimethyl-1-oxopropyl)thio)ethyl N-(phenylmethyl)phosphoramidate); 4W44B4S9OC; S-[2-[[(2R,3R,4R,5R)-5-(2-amino-6-oxo-1H-purin-9-yl)-3,4-dihydroxy-4-methyloxolan-2-yl]methoxy-(benzylamino)phosphoryl]oxyethyl] 3-hydroxy-2,2-dimethylpropanethioate; UNII-4W44B4S9OC; SCHEMBL3132403; IDX 184

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 : ~250 mg/mL (~398.97 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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