HSV-1(IC50=0.02 μM);HSV-2(IC50=0.02 μM)

Pritelivir (formerly known as AIC316, BAY 57-1293) is a novel and potent helicase primase inhibitor that showed antiviral effect on herpes simplex virus (HSV) with IC50 of 20 nM for both HSV-1 and HSV-2. It represents a new class of potent inhibitors of HSV that target the virus helicase primase complex. BAY 57-1293 exhibits anti-herpes activity through inhibiting the helicase-primase and affecting the viral DNA synthesis. In the in vitro viral replication assay, BAY 57-1293 shows inhibition against HSV-1 F, HSV-2 G and acyclovir-resistant HSV-1 F mutant with IC50 value of 20nM. Thus, BAY 57-1293 has significant potential for the treatment of HSV disease in humans, including those resistant to current medications. The mechanism of action is that BAY 57-1293 directly inhibits the ATPase activity of the viral helicase-primase enzyme complex in a dose-dependent manner. BAY 57-1293 also shows potent antiviral activity against acyclovir resistant HSV mutants. BAY 57-1293 reduces Aβ and P-tau induced by herpes simplex virus type 1 in vero cells.

Pritelivir is the first antiviral medication in a class that targets the viral helicase-primase enzyme complex to prevent HSV replication[2]. The dosage of pritelivir (0.03–45 mg/kg) considerably improves survival. In HSV-1, E-377, pritelivir (0.3–30 mg/kg) lowers mortality. Pritelivir possesses strong and antiviral efficacy that breaks resistance, making it a promising treatment for potentially fatal HSV type 1 and 2 infections, such as herpes simplex encephalitis[3]. When compared to the vehicle-treated group, combination therapies using Pritelivir at 0.1 or 0.3 mg/kg/dose and Acyclovir (10 mg/kg/dose) are protective against HSV-2, strain MS[3].

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HSV shedding among placebo recipients was detected on 16.6% of days; shedding among Pritelivir recipients was detected on 18.2% of days among those receiving 5 mg daily, 9.3% of days among those receiving 25 mg daily, 2.1% of days among those receiving 75 mg daily, and 5.3% of days among those receiving 400 mg weekly. The relative risk of viral shedding with pritelivir, as compared with placebo, was 1.11 (95% confidence interval [CI], 0.65 to 1.87) with the 5-mg daily dose, 0.57 (95% CI, 0.31 to 1.03) with the 25-mg daily dose, 0.13 (95% CI, 0.04 to 0.38) with the 75-mg daily dose, and 0.32 (95% CI, 0.17 to 0.59) with the 400-mg weekly dose. The percentage of days with genital lesions was also significantly reduced, from 9.0% in the placebo group to 1.2% in both the group receiving 75 mg of pritelivir daily (relative risk, 0.13; 95% CI, 0.02 to 0.70) and the group receiving 400 mg weekly (relative risk, 0.13; 95% CI, 0.03 to 0.52). The rate of adverse events was similar in all groups. Conclusions: Pritelivir reduced the rates of genital HSV shedding and days with lesions in a dose-dependent manner in otherwise healthy men and women with genital herpes. (Funded by AiCuris; ClinicalTrials.gov number, NCT01047540.). [2]

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Pritelivir, a helicase-primase inhibitor, has excellent in vitro and in vivo activity against human herpes simplex virus (HSV). Mice lethally infected with HSV type 1 or 2, including acyclovir-resistant strains, were treated 72 h after infection for 7 days with pritelivir or acyclovir. Both drugs were administered orally twice daily either alone or in combination. Dosages of Pritelivir from 0.3 to 30 mg/kg reduced mortality (P < 0.001) against HSV-1, E-377. With an acyclovir resistant HSV-1, 11360, pritelivir at 1 and 3 mg/kg increased survival (P < 0.005). With HSV-2, MS infected mice, all dosages higher than the 0.3 mg/kg dose of Pritelivir were effective (P < 0.005). For acyclovir resistant HSV-2, strain 12247, pritelivir dosages of 1-3 mg/kg significantly improved survival (P < 0.0001). Combination therapies of pritelivir at 0.1 or 0.3 mg/kg/dose with acyclovir (10 mg/kg/dose) were protective (P < 0.0001) when compared to the vehicle treated group against HSV-2, strain MS (in line with previous data using HSV-1). An increased mean days to death (P < 0.05) was also observed and was indicative of a potential synergy. Pharmacokinetic studies were performed to determine pritelivir concentrations and a dose dependent relationship was found in both plasma and brain samples regardless of infection status or time of initiation of dosing. In summary, pritelivir was shown to be active when treatment was delayed to 72 h post viral inoculation and appeared to synergistically inhibit mortality in this model in combination with acyclovir. We conclude pritelivir has potent and resistance-breaking antiviral efficacy with potential for the treatment of potentially life-threatening HSV type 1 and 2 infections, including herpes simplex encephalitis [3].

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BAY 57-1293 belongs to a new class of antiviral compounds and inhibits replication of herpes simplex virus (HSV) type 1 and type 2 in the nanomolar range in vitro by abrogating the enzymatic activity of the viral primase-helicase complex. In various rodent models of HSV infection the antiviral activity of BAY 57-1293 in vivo was found to be superior compared to all compounds currently used to treat HSV infections. The compound shows profound antiviral activity in murine and rat lethal challenge models of disseminated herpes, in a murine zosteriform spread model of cutaneous disease, and in a murine ocular herpes model. It is active in parenteral, oral, and topical formulations. BAY 57-1293 continued to demonstrate efficacy when the onset of treatment was initiated after symptoms of herpetic disease were already apparent. [6]

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BAY 57-1293 (p.o.) shows profound antiviral activity in murine and rat lethal challenge models of disseminated herpes (0.5 mg/kg), in a murine zosteriform spread model of cutaneous disease (15 mg/kg), and in a murine ocular herpes model.

Pritelivir (formerly known as AIC316, BAY 57-1293) is a novel and potent helicase primase inhibitor that showed antiviral effect on herpes simplex virus (HSV) with IC50 of 20 nM for both HSV-1 and HSV-2.

In the in vitro viral replication assay, BAY 57-1293 shows inhibition against HSV-1 F, HSV-2 G and acyclovir-resistant HSV-1 F mutant with IC50 value of 20nM. In the plaque reduction assay and the conventional cytopathogenicity assay, BAY 57-1293 shows IC50 values of 0.01-0.02μM and 0.01-0.03μM, respectively.

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The strains of HSV-1 utilized were the laboratory strain E-377 and the clinical isolate11360 and the strains of HSV- 2 were the laboratory strain MS and the clinical isolate 12247. Isolates were gifts of Jack Hill, Burroughs Wellcome. The susceptibilities of these viruses have been reported previously (Prichard et al., 2009; Tardif et al., 2014). The in vitro half maximal efficacy concentration (EC50) for ACV for strain 11360 was >100 µM and for strain 12247 was also >100 µM and both strains are considered ACV resistant. The strains have the following polymorphisms with ACV resistance-mediating mutations underlined: TK polymorphisms C6G, N23S, K36E, S181N, A192V, G251C, A265T, V267L, P268T, D286E, and N376H (relative to NC_001806) for strain 11360 and G39E, N78D, L140F and C337Y (relative to NP044492.1) and DNA polymerase polymorphisms A9T, P15S and L60P for strain 12247 (relative to NP 044500.1), and S33G, V905M, A1203T, and T1208A (NC_001806) for strain 11360. Human foreskin fibroblast (HFF) cells were prepared as primary cultures from freshly obtained newborn human foreskins and virus stocks were prepared and quantified in HFF cells for use in vivo by methods reported previously (Prichard et al., 2013). [3]

Animal/Disease Models: Female balb/c (Bagg ALBino) mouse[3]
Doses: 0.03 to 45 mg/kg
Route of Administration: Administered orally, twice (two times) daily at approximately 12 h intervals, for 7 days
Experimental Results: Survival was Dramatically increased to 80-100% as compared to the vehicle treatment. Even the lowest dose of 0.3 mg/kg was effective in increasing survival to 53%.

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Pritelivir (PTV) was suspended in 1.0% carboxymethylcellulose (CMC) in water for oral delivery to mice. ACV was also suspended in 1.0% CMC for oral administration. Compounds were prepared in a 0.2 ml volume. Treatments for efficacy and drug distribution evaluations were administered to mice for 7 consecutive days beginning 24–72 h post viral inoculation by oral gavage using doses ranging from 0.03 to 45 mg/kg of Pritelivir (PTV) or 1 to 50 mg/kg of ACV given twice daily at approximately 12 h intervals depending on the specific protocol. For combination studies, data was used from previous studies which indicated that the lowest effective dose of ACV was 30 mg/kg administered orally twice daily (Prichard et al., 2011). The lowest effective dose of Pritelivir (PTV) was determined in these studies to be 0.3 mg/kg when given orally twice daily. Dose levels of 10 mg/kg for ACV and 0.3 mg/kg for Pritelivir (PTV) were selected as the highest dosages to enable the detection of improved efficacy of the combination by employing an experimental design previously reported (Quenelle et al., 2007). All mice in combination studies were dosed twice daily beginning 72 h following viral inoculation using a total volume of 0.2 ml solution of vehicle or drug solutions to equilibrate stress.[3]

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For pharmacokinetic studies, five mice each from vehicle and drug-treated groups were euthanized on day 8, 9 or 10 post viral inoculation following the last treatment for aseptic collection of brain and serum. Treatments were initiated at 24, 48 or 72 h post viral inoculation and uninfected mice were included for comparison. Mice were anesthetized with ketamine-xylazine via intraperitoneal injection for retro-orbital collection of whole blood using capillary tubes into a heparinized tube setting in an ice bath. Blood was stored on ice then centrifuged 134 × g for 7 min. Plasma was collected and transferred to a new vial and immediately frozen at −80°C until assayed for Pritelivir (PTV) levels by high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) (below). Mice were euthanized via carbon dioxide-oxygen asphyxiation for aseptic retrieval of brain samples. Samples were snap frozen on ethanol-dry ice and stored frozen at −80° C until assayed for Pritelivir (PTV) concentrations by HPLC-MS (below).[3]

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The four dosing regimens for Pritelivir were a loading dose of 20 mg followed by a daily dose of 5 mg, a loading dose of 100 mg followed by a daily dose of 25 mg, a loading dose of 300 mg followed by a daily dose of 75 mg, and a weekly dose of 400 mg. The regimen for the administration of placebo was the same as it was for the administration of pritelivir. The study drug was taken for a period of 28 days. [2]

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Dissolved in 0.5% tylose in PBS; 0.5 mg/kg or 15 mg/kg; p.o.

Murine and rat lethal challenge models of disseminated herpes, a murine zosteriform spread model of cutaneous disease, a murine ocular herpes model.

Pharmacokinetic analysis of drug concentrations showed that the concentration of PTV in both infected and uninfected mice was dose-dependent. The mean plasma concentrations were 2 µg/ml, 4 µg/ml and 9 µg/ml, respectively, after twice-daily administration of 5 mg/kg, 15 mg/kg or 45 mg/kg doses, and were independent of infection status or time of administration (Figure 5). Similarly, the mean concentrations in brain tissue samples were approximately 0.05 µg/g in the 5 mg/kg dose group, approximately 0.11 µg/g in the 15 mg/kg dose group and approximately 0.22 µg/g in the 45 mg/kg dose group, and were independent of infection status or time of administration (Figure 6). [3] Pharmacokinetic results [4] Single escalation dose (Experiment 1) [4] The plasma concentration-time curve of preceptvir was characterized by rapid initial absorption with no significant lag time. The maximum or near-maximum plasma concentration was reached approximately 1.5 hours after administration, followed by a plateau phase lasting approximately 4.5 hours. This plateau phase was characterized by multiple absorption peaks. Following the plateau phase, plasma concentrations exhibited a multi-exponential decline, initially sharp (starting 4.5 hours post-dose), followed by a slower rate of decline (starting 5 to 5.5 hours post-dose). A slight increase in preripanevir plasma concentrations was observed in most subjects between 8 and 16 hours post-dose (Figure 1A). Terminal concentrations at all dose levels generally showed a parallel decreasing trend (Figure 1B). The shape of the preripanevir plasma concentration-time curves was similar in female subjects to that in male subjects, but initial plasma concentrations were higher in female subjects (Figures 2A and 2B). Table S2 summarizes the pharmacokinetic parameters of preripanevir after a single dose for all dose groups. Cmax, AUC0-24h, AUC0-last, and AUC0-inf all increased with increasing dose within the dose range of 5 to 480 mg. AUC0-last and AUC0-inf could not be accurately determined in the 5 mg and 10 mg dose groups due to the initial pharmacokinetic sampling protocol (120 hours) being insufficient to characterize the terminal elimination phase. No further increase in exposure was observed from 480 mg to 600 mg (Table S2, Figure 3). Within the dose range of 20 to 480 mg, no statistically significant deviations were observed in Cmax, AUC0-24h, AUC0-last, and AUC0-inf relative to dose ratio (Table S3). Inter-subject variability (%CV) was comparable across dose groups, ranging from 10% to 51% for Cmax and 15% to 32% for AUC0-inf. The elimination half-life was accurately determined using concentration-time curves starting from 20 mg. The mean t1/2z ranged from 52 to 83 hours. The percentage of unchanged drug excreted in urine was negligible, not exceeding 0.3%, across all dose groups. Compared to men, women had mean 1.5-fold and 1.1-fold higher Cmax and AUC0-inf, respectively (Table S4). The intersubject variability (%CV) of Cmax was higher in women (33%) than in men (10%), while the intersubject variability of AUC0-inf was similar (16% in men and 17% in women).

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Food effect (Trial 2)[4]
The mean plasma concentration of preceptvir rose faster in the fasting state than in the eating state, but the mean maximum plasma concentration was lower. The plateau period of approximately 1.5 to 4.5 hours after administration observed in the fasting state was not observed in the eating state (Figure 4). The median tmax was later in the eating state than in the fasting state (5 hours vs. 3.5 hours). The mean Cmax and AUC0-last were both higher in the eating state than in the fasting state (Table S5), with least squares mean ratios of 133% and 116%, respectively (Table S6). The difference between the eating and fasting states was statistically significant, with the upper limit of the 90% confidence interval for the least squares mean ratio being higher than the 125% equivalence limit. No lag time was observed in either the eating or fasting state. Tmax was prolonged by 1.5 hours in the eating state compared to the fasting state; however, this difference was not statistically significant. The variability (%CV) of inter-subject exposures (Cmax, AUC0-last, and AUC0-inf) was lower in the eating state (13%–18%) than in the fasting state (22%–28%).

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Multiple dose escalation (Trials 3 and 5) [4]
On day 1 and day 21 (day 16 for the 400 mg dose group), the mean plasma concentration of preceptvir increased with increasing dose (Figure 5). The plasma concentration-time curves of preceptvir were similar in shape after a single dose (day 1) and multiple doses (days 21/16). The terminal phase concentrations at all dose levels generally showed a parallel decreasing trend. Table S7 summarizes the pharmacokinetic parameters of preceptvir after single and multiple doses in all dose groups. On days 1 and 21, both Cmax and AUC0-24h increased proportionally with the dose. The increase in mean Cmin appeared to be slightly smaller. The dose varied proportionally from 100 mg to 200 mg. It should be noted that the accuracy of Cmin, Cmax, and AUC0-24h was lower in the 400 mg dose group because sampling only began 3 hours after administration on day 16. Steady state was typically reached between days 8 and 13. Based on the least-squares mean ratio, the cumulative folds of Cmax and AUC0-24h were 4.4 to 5.0 and 4.4 to 5.1, respectively (Table S6). Statistical analysis showed that on days 1 and 21/16, Cmax and AUC0-24h did not show significant deviations from the dose ratio in the 5–400 mg dose range, while Cmin showed a significant deviation from the dose ratio in the 5–400 mg dose range (Table S3). Statistically significant differences were observed in pairwise comparisons between dose groups. On day 21, Cmax was compared between the 100 mg and 200 mg dose groups, and AUC0-24h was compared between the 100 mg and 200 mg dose groups and the 100 mg and 400 mg dose groups. For Cmin, pairwise comparisons showed statistically significant differences between the 5 mg, 25 mg, and 100 mg dose groups and the 200 mg and 400 mg dose groups.

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Absolute bioavailability (Experiment 4)[4]
After intravenous administration of a microdose, the mean plasma concentration of dose-normalized 14C-labeled preripabin was higher than that of oral unlabeled preripabin (Fig. 6A). Except for the initial phase of the curve, the plasma concentration-time curves of 14C-labeled and unlabeled preripabin were similar in shape, due to the lack of an absorption phase for intravenously administered 14C-labeled preripabin. The terminal phase concentration showed a parallel decreasing trend (Fig. 6B). The mean t_1/2z value of 14C-labeled preripabin was comparable to that of unlabeled preripabin. Systemic clearance and volume of distribution after intravenous administration were consistent with the mean CL/F values observed after oral administration (adjusted for bioavailability). Based on average bioavailability, the absolute oral bioavailability of preripamide was 73% (Table S8), while the absolute oral bioavailability based on AUC_last and AUC_0-inf was 72%. The least squares mean ratio of oral unlabeled preripamide and intravenously dose-normalized 14C-labeled preripamide, AUC_0-last and AUC_0-inf, were 72.4% and 71.9%, respectively (Table S6).

Safety and Tolerability [4]
In trials 1, 2, 3, 4 and 5 (up to 200 mg doses), single doses of 5 to 600 mg of preripabinvir (5-600 mg in trial 1, 80 mg [fasting and postprandial] in trial 2, and 100 mg of unlabeled preripabinvir plus 3 μg of 14C-labeled preripabinvir in trial 4) and once daily doses of 5 to 200 mg for 21 days (trials 3 and 5) were well tolerated. The highest doses in trials 1 and 3 did not reach the maximum tolerated dose. No clinically significant results or dose-related trends were observed in safety parameters such as adverse events, vital signs, electrocardiograms or routine clinical laboratory tests. Many of the reported adverse events were nonspecific and were typically observed in clinical trials in healthy volunteers. The incidence of adverse events was not clinically significant between the placebo and preripamide groups (66.7% and 56.9% in Trial 1, 85.0% and 79.2% in Trial 3, and 87.5% and 79.2% in Trial 5, respectively). No deaths, serious adverse events, or other significant adverse events occurred. An overview of all treatment-related adverse events is provided in Tables S9 (Trial 1), S10 (Trial 2), S11 (Trial 4), and S12 (Trials 3 and 5). In the 400 mg dose group of Trial 5, an increased number of adverse events was observed in almost all subjects (100% of subjects experiencing adverse events), particularly regarding skin and subcutaneous tissue diseases associated with standard of care (SOC). Three subjects discontinued treatment before day 16 due to adverse events. Due to these three adverse events, as well as adverse events in four other subjects in this dose group (see Tables S12 and S13), the trial was terminated early on the morning of day 16 after the last dose of the investigational drug. One subject (400 mg dose group) experienced a deterioration in general health, diagnosed by an ENT specialist as most likely a viral infection; however, the possibility of an allergic reaction could not be ruled out. Additionally, subjects in the placebo group also experienced treatment-associated adverse events (TEAEs) related to skin and subcutaneous tissue diseases treated with standard of care (SOC). Laboratory results showed elevated immunoglobulin E levels, decreased neutrophil and leukocyte levels in five subjects in the 400 mg dose group, and elevated C-reactive protein levels in a few individuals. One subject in the placebo group also experienced a clinically significant increase in immunoglobulin E levels. No clinically significant changes in vital signs or ECG parameters were observed in the 400 mg dose group. No deaths, serious adverse events, or other significant adverse events occurred in any dose group.

[1]. Identification of Amino Acids Essential for Viral Replication in the HCMV Helicase-PrimaseComplex. Front Microbiol. 2018 Oct 23;9:2483.

[2]. Helicase-primase inhibitor Pritelivir for HSV-2 infection. N Engl J Med. 2014 Jan 16;370(3):201-10.

[3]. Efficacy of pritelivir and acyclovir in the treatment of herpes simplex virus infections in a mouse model of herpes simplex encephalitis. Antiviral Res. 2018 Jan;149:1-6.

[4]. First-in-Human, Single- and Multiple-Ascending-Dose, Food-Effect, and Absolute Bioavailability Trials to Assess the Pharmacokinetics, Safety, and Tolerability of Pritelivir, a Nonnucleoside Helicase-Primase Inhibitor Against Herpes Simplex Virus in Healthy Subjects. Clin Pharmacol Drug Dev. 2023 Jul;12(7):749-760.

[5]. New helicase-primase inhibitors as drug candidates for the treatment of herpes simplex disease. Nat Med.2002 Apr;8(4):392-8;
[6]. Potent in vivo antiviral activity of the herpes simplex virus primase-helicase inhibitor BAY 57-1293. Antimicrob Agents Chemother.2002 Jun;46(6):1766-72.

Pritelivir (PRR) has been used in clinical trials for the prevention of herpes simplex virus type 2 (HSV-2) and genital herpes. PRR is a thiazolamide helicase-primase inhibitor effective against both HSV-1 and HSV-2. PRR is an inhibitor of the helicase-primase complex, preventing the helicase or primase-catalyzed cycle of viral DNA, thereby interfering with DNA replication and proliferation. This drug does not require HSV thymidine kinase activation and has a longer plasma half-life than nucleoside analogs. Novel inhibitors targeting the viral helicase-primase complex have been reported to block the replication of herpes simplex virus and varicella-zoster virus, but they are ineffective against another herpesvirus—human cytomegalovirus (HCMV). The HCMV helicase-primase complex (pUL105-pUL102-pUL70) is crucial for viral DNA replication and may therefore be an important antiviral target. The functions of the individual subunits that make up this complex remain to be elucidated. By sequence alignment of herpesvirus homologs, we identified conserved amino acids in the pUL105 putative ATP-binding site and the pUL70 putative zinc finger domain. Mutation analysis of several such amino acids in pUL105 and pUL70 showed that they are essential for viral replication. We also constructed the theoretical structure of the pUL105 N-terminal domain by homology modeling, which showed that conserved amino acids mutated in this domain may be involved in ATP hydrolysis. [1]

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Background: Pritelivir is a viral helicase-primase complex inhibitor that has shown antiviral activity in vitro and in animal models of herpes simplex virus (HSV) infection. We tested the efficacy and safety of pritelivir in healthy individuals infected with genital herpesvirus type 2 (HSV-2). Methods: We randomly assigned 156 HSV-2 positive patients with a history of genital herpes to four oral preceptivir groups (5, 25 or 75 mg daily, or 400 mg weekly) or placebo groups for 28 days. Genital swabs were collected daily from the subjects for HSV-2 testing using polymerase chain reaction (PCR). Genital signs and symptoms were also recorded from the subjects. The primary endpoint was genital HSV shedding rate. [2] This study shows that preceptivir, as the first novel antiviral drug for the treatment of herpes simplex virus infection, can effectively inhibit viral shedding and lesion development in patients with genital herpes. Further studies are needed to evaluate the clinical benefit of preceptivir in the treatment of herpes simplex virus (HSV) infection and to determine its effectiveness in treating severe HSV disease and reducing sexual transmission. In May 2013, the U.S. Food and Drug Administration (FDA) suspended the clinical development of preceptivir due to unexplained skin and hematological abnormalities in a toxicology study in monkeys. In this study, monkeys received daily doses ranging from 75 mg to 1000 mg per kilogram of body weight (70 to over 900 times the human dose of 75 mg). Researchers are currently investigating the cause of these abnormalities in the monkeys; no similar abnormalities were observed in this trial. [2] In this study, PTV showed potent antiviral activity against both HSV-1 and HSV-2 (including ACV-resistant strains) in vivo. When treatment was delayed until 72 hours after viral inoculation, the antiviral activity of PTV was significantly higher than that previously reported at the time of treatment initiation (6 hours after viral inoculation) (Betz et al., 2002). Delaying treatment until 72 hours after infection is considered to better simulate the clinical situation where patients seek medical attention after the onset of symptoms and then receive treatment. The activity of PTV in combination with ACV suggests that PTV has at least an additive effect against HSV-2 MS strains, and possibly even a synergistic effect. We previously reported a potential synergistic effect of PTV against HSV-1 E-377 strain in a similar study, where a combination of 10 mg/kg ACV and 0.3 mg/kg PTV significantly improved survival compared to either drug alone (Quenelle et al., 2016). While further research is needed to formally confirm the synergistic effect, the data suggest that PTV, alone or in combination with ACV, could be a novel treatment option for HSV encephalitis, given the less-than-ideal efficacy of ACV and the need for more effective therapies. Furthermore, the different molecular targets of these two compounds (PTV targets the HSV helicase-primase complex, while ACV targets the viral polymerase) would significantly reduce the risk of resistance. Moreover, as our model demonstrates, PTV therapy could be used to treat ACV-resistant infections due to its different mechanisms of action, as previously reported in HSV encephalitis (Kakiuchi et al., 2012; Schepers et al., 2014; Bergmann et al., 2017). Equally important, we were able to confirm the presence of PTV in plasma and brain tissue. PTV was detected in the brain tissue of both uninfected and infected animals, and the level of PTV exposure in brain tissue was directly proportional to the level in plasma. Since herpes simplex virus (HSV) encephalitis is caused by viral replication in the brain, leading to acute inflammation, congestion, and/or hemorrhage (Whitley 2006), the delivery and activity of drugs within the central nervous system are crucial for treating this disease. In previous studies (Betz et al., 2002), PTV treatment significantly reduced viral load in the cerebral cortex compared to placebo and valacyclovir treatment. Therefore, the level of PTV exposure in the brain is considered sufficient to exert therapeutic effects. In a human dose-exploration clinical trial in patients with genital HSV-2 infection, PTV reduced lesions and viral shedding. Furthermore, no HSV-2 resistant isolates were found after 4 weeks of daily treatment (Edlefsen et al., 2016). These results, along with the new data presented in this paper, suggest that PTV may be effective in treating HSV encephalitis in the future. [3] The pharmacokinetics and safety of preceptvir, a novel herpes simplex virus helicase-primase inhibitor, were evaluated in five Phase I clinical trials: a single-dose escalation trial, two multiple-dose escalation trials, a food effect trial, and an absolute bioavailability trial in healthy male subjects. The single-dose escalation trial included a cohort of healthy female subjects. After a single dose, the pharmacokinetics of preceptvir were linear up to 480 mg; after once-daily multiple-dose administration, they were also linear up to 400 mg. The half-life was 52 to 83 hours, and steady-state plasma concentrations were reached within 8 to 13 days. Compared with male subjects, female subjects had 1.5-fold higher peak plasma concentrations and 1.1-fold higher area under the plasma concentration-time curve (AUC) from 0 to the last quantifiable concentration. The absolute bioavailability in fasting condition was 72%. Following a high-fat diet, the time to peak concentration of preripamide was delayed by 1.5 hours, and the peak plasma concentration and the area under the plasma concentration-time curve (from 0 to the last quantifiable concentration) increased by 33% and 16%, respectively. A single dose of 600 mg preripamide and multiple doses of 200 mg preripamide daily were both safe and well-tolerated. Given the therapeutic dose of 100 mg once daily, preripamide demonstrated good safety, tolerability, and pharmacokinetic profiles in healthy subjects, supporting its further development. [4]

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Studies tested a wide dose range of 5 to 600 mg (single dose) and 5 to 400 mg (once daily). Since the pharmacokinetic profile at the 80 mg dose was well-described, consistent with other dose levels, and considered safe and well-tolerated, the sex effect and food effect were tested at the 80 mg dose, and the absolute bioavailability was tested at the 100 mg dose. In addition, based on pharmacokinetic/pharmacodynamic calculations and the results of the Phase II clinical trial, the therapeutic dose of 100 mg once daily was determined to be well within the evaluation range. All Phase I clinical trials were conducted in healthy male subjects. Initially, only male subjects were enrolled because specific toxicological data regarding maternal and embryo/fetal toxicity were unavailable at the start of the first-in-human trial (SAD, Trial 1). Results from two Phase II studies (rats and rabbits) during the SAD trial allowed for the inclusion of women of reproductive age. Therefore, a cohort of female subjects was enrolled to obtain basic information on sex differences in the pharmacokinetics of preripamide. More sex data will be collected in future trials. Following oral administration, the plasma concentration-time profile of preripamide was characterized by rapid initial absorption, a plateau phase of 1.5 to 4.5 hours (fasting), and a slight increase in concentration 8 to 16 hours post-administration. These characteristics may be related to the pH-dependent solubility (ionization degree 5.2) of the administered preripamide mesylate, with lower pH favoring its dissolution. The increased plasma concentration observed 8 to 16 hours post-administration may be due to other absorption processes, such as enterohepatic circulation. Following a single dose, the pharmacokinetics of preripabin are linear, with a maximum dose of 480 mg; with multiple daily doses, the maximum dose is 400 mg (the highest multiple-dose dose tested). Some fluctuations in dose-normalized parameters between dose groups are not uncommon, given the small number of subjects in each dose group (n = 6). Following a single 600 mg dose of preripabin, no further increases in any exposure parameters were observed, indicating that gastrointestinal absorption had reached saturation. An increase in CL/F at this dose level confirms reduced absorption. Steady state is typically reached between days 8 and 13 after multiple doses of preripabin; therefore, although the pharmacokinetic parameters measured on day 16 for the 400 mg dose group are considered approximate (since the first pharmacokinetic sample for this dose group was collected 3 hours after administration), these parameters are still representative of steady state. The cumulative drug amount at steady state is approximately 5 times the initial value. At a dose of 400 mg, the AUC0-inf in the single-dose trial (SAD) was similar to the AUC0-24h in the multiple-dose trial (MAD) at steady state, indicating that the pharmacokinetics of preripamide are independent of time. Female subjects had higher initial plasma concentrations compared to male subjects, resulting in a higher mean Cmax (1.5-fold) and a slightly higher AUC0-inf (1.1-fold). The mean CL/F value was 1.1-fold higher in male subjects than in female subjects, but this value decreased by approximately 10% after adjusting for individual weight (Table S4). Due to the small differences and the very small sample size (n=6 per group), it is not possible to draw definitive conclusions about the effect of sex or weight on the pharmacokinetics of preripamide. Future studies with more female subjects will further explore this. The effect of food was assessed at an 80 mg dose under fasting and postprandial (high-fat breakfast) conditions. After a high-fat breakfast, the median tmax was delayed by 1.5 hours compared to the fasting condition due to slower initial absorption. The mean Cmax and AUC0-last increased by 33% and 16%, respectively. The clinical significance of this increase should be interpreted with caution, as a more conventional diet may have a smaller impact on the pharmacokinetics of preceptvir. Overall, given the high oral bioavailability of preceptvir and its minimal food-related influence, it can be administered without food intake in future trials. Pharmacokinetics of preceptvir following intravenous administration were determined in an absolute bioavailability study. Using sensitive accelerator mass spectrometry (AMS), only a 3 μg (9.3 kBq) dose was required to detect ¹⁴C-labeled preceptvir in plasma, minimizing radiation exposure. The time to peak concentration (t_max) was consistent with that after 100 mg oral administration to ensure that the pharmacokinetics of the microdose reflected the pharmacokinetics at pharmacologically relevant plasma concentrations. Oral bioavailability showed no absorption problems, and the calculated bioavailability results indicated a high concentration (72%), thus supporting oral administration. The observed mean volume of distribution of 14C-labeled preripamide (79 L) was significantly greater than the total body fluid volume (±42 L), indicating that preripamide is distributed in tissues. The mean clearance after intravenous infusion (0.82 L/h) was much lower than the hepatic blood flow (±87 L/h), indicating that preripamide is a low-clearance drug. The CL/F after oral administration of 100 mg was 1.18 L/h, reflecting its absolute bioavailability. Preripamide was well tolerated in healthy male subjects with single oral doses up to 600 mg, in female subjects with single oral doses up to 80 mg, and in multiple doses of up to 200 mg once daily for 21 consecutive days. No clinically significant results were found in safety parameters, and there was no significant trend or correlation between treatment-exclusive adverse events (TEAEs) and dose. In placebo-controlled trials, there were no significant clinical differences in the number, type, and incidence of TEAEs between the placebo and preripamide groups. Several subjects experienced adverse events falling under the standard treatment (SOC) category of skin and subcutaneous tissue disorders when taking 400 mg once daily (two moderate and the rest mild), leading to the early termination of Trial 5. Notably, this occurred after administration of preripamide and placebo, and the preripamide exposure was approximately four times the expected therapeutic dose/exposure after a 100 mg once daily dose. Skin observations were generally mild and rapidly resolved; these effects were limited to the skin surface and self-limiting, with no signs of pustular reactions or serious systemic illness (no drug rash with eosinophilia and systemic symptoms). The presence of signs and symptoms of viral infection in several subjects in both the preripamide and placebo groups may have contributed to the adverse events; however, the influence of preripamide cannot be completely ruled out. Preripamide is a carbonic anhydrase isoenzyme inhibitor. ¹⁵ Approved carbonic anhydrase inhibitors, such as acetazolamide, have been associated with the following adverse reactions when used at therapeutic doses: urinary urgency, decreased function, hearing impairment, acidosis, hypercalciuria, depression, and liver dysfunction. Therefore, in Trial 1, its potential inhibitory effect on carbonic anhydrase was assessed by measuring renal excretion of Na+, K+, and Cl-. No effect on renal excretion of sodium, potassium, and chloride was detected in urine samples from any dose group during all collection periods within 48 hours after administration, indicating that no significant carbonic anhydrase inhibition was observed at the administered dose. Based on the results of these trials, a suitable dosing regimen was selected for further development to achieve trough concentrations that inhibit viral replication throughout the dosing interval. The 90% effective concentration (EC90) of HSV-2 was calculated to be 66 ng/mL based on the in vitro 50% effective concentration of 12 ng/mL and was used as the threshold. 6. After adjusting for plasma protein binding in the MAD trial (2.8%, determined by equilibrium analysis; data archived), the free steady-state trough concentrations for once-daily dosing regimens of 5, 25, 100, and 200 mg were approximately 5, 23, 105, and 157 ng/mL, respectively, indicating that once-daily doses of 100 mg or higher would result in plasma concentrations exceeding EC90 throughout the dosing interval. Based on these data, the ongoing Phase 3 trial (PRIOH-1, NCT03073967) in immunocompromised patients with acyclovir-resistant mucocutaneous HSV infection has selected a once-daily dose of 100 mg and has been successfully used in an international early access program for immunocompromised HSV patients resistant to or intolerant of acyclovir and foscarnet. 16, 17 Overall, the pharmacokinetic characteristics of preceptvir include high oral bioavailability, supporting oral administration; dose-dependent distribution over a wide dose range; Vd indicating extravascular tissue distribution; trough concentration levels exceeding the EC90 for in vitro inhibition of viral replication, starting with 100 mg once daily; and safety and tolerability data supporting dosing regimens up to 200 mg once daily. This supports further development of preceptvir as a novel HSV drug and exploration of dosing regimens that can produce sufficiently high concentrations to sustain HSV replication inhibition. [4]

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The vast majority of the world’s population is infected with at least one human herpesvirus. Herpes simplex virus (HSV) infection is the cause of cold sores and genital herpes, and can lead to life-threatening or blinding illnesses, primarily affecting immunocompromised patients, pregnant women, and newborns. No new non-nucleoside antiherpes drugs have been introduced since the late 1970s with the advent of acyclovir (Zovirax), a nucleoside inhibitor of herpesvirus DNA polymerase. This article reports a novel HSV helicase-primase inhibitor with potent in vitro antiherpetic activity, a novel mechanism of action, low resistance rate, and excellent efficacy against HSV in animal models. BAY 57-1293 (N-[5-(aminosulfonyl)-4-methyl-1,3-thiazolyl-2-yl]-N-methyl-2-[4-(2-pyridyl)phenyl]acetamide) is a well-tolerated member of this class of compounds, significantly shortening healing time, preventing disease rebound after drug withdrawal, and most importantly, reducing the frequency and severity of recurrent disease. Therefore, this class of drugs has great potential in treating human herpes simplex virus infections, including infections resistant to existing drugs. [5]

C19H22N4O6S3

498.596180438995

498.07

C, 45.77; H, 4.45; N, 11.24; O, 19.25; S, 19.29

1428333-96-3

Pritelivir;348086-71-5;Pritelivir mesylate hydrate;1428321-10-1

11950374

White to off-white solid powder

2

10

5

32

709

0

S(C1=C(C)N=C(N(C)C(CC2C=CC(C3C=CC=CN=3)=CC=2)=O)S1)(N)(=O)=O.S(C)(=O)(=O)O

PPAJHCGEURRDOG-UHFFFAOYSA-N

InChI=1S/C18H18N4O3S2.CH4O3S/c1-12-17(27(19,24)25)26-18(21-12)22(2)16(23)11-13-6-8-14(9-7-13)15-5-3-4-10-20-15;1-5(2,3)4/h3-10H,11H2,1-2H3,(H2,19,24,25);1H3,(H,2,3,4)

N-methyl-N-(4-methyl-5-sulfamoylthiazol-2-yl)-2-(4-(pyridin-2-yl)phenyl)acetamide mesylate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

DMSO : ~83.33 mg/mL ( ~167.13 mM )

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.17 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 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 20.8 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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Solubility in Formulation 2: ≥ 2.08 mg/mL (4.17 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in 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 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (4.17 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (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 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 10% DMSO+40% PEG300+5% Tween-80+45% Saline: ≥ 2.08 mg/mL (4.17 mM)

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