Discovery, Chemistry, and Preclinical Development of Pritelivir, a Novel Treatment Option for Acyclovir-Resistant Herpes Simplex Virus Infections

Replacement of sulfonamide by sulfoximine within a helicase-primase inhibitor with restricted flexibility

Helicase-primase is an interesting target for the therapy of herpes simplex virus (HSV) infections. Since amenamevir is already approved for varicella-zoster virus (VZV) and HSV in Japan and pritelivir has received breakthrough therapy status for the treatment of acyclovir-resistant HSV infections in immunocompromised patients, the target has sparked interest in me-too approaches. Here, we describe the attempt to improve nervous tissue penetration in Phaeno Therapeutics drug candidate HN0037 to target the latent reservoir of HSV by installing less polar moieties, mainly a difluorophenyl instead of a pyridyl group, and replacing the primary sulfonamide with a methyl sulfoximine moiety. However, all obtained stereoisomers exhibited a weaker inhibitory activity on HSV-1 and HSV-2.

Emerging drugs for the treatment of herpetic keratitis

INTRODUCTION

Herpes simplex keratitis stands as a prominent factor contributing to infectious blindness among developed nations. On a global scale, over 60% of the population tests positive for herpes simplex virus type-1 (HSV-1). Despite these statistics, there is currently no vaccine available for the virus. Moreover, the conventional nucleoside drugs prescribed to patients are proving ineffective in addressing issues related to drug resistance, recurrence, latency, and the escalating risk of vision loss. Hence, it is imperative to continually explore all potential avenues to restrict the virus. This review article centers on the present treatment methods for HSV-1 keratitis (HSK), highlighting the ongoing clinical trials. It delves into the emerging drugs, their mode-of-action and future therapeutics.

AREAS COVERED

The review focuses on the significance of a variety of small molecules targeting HSV-1 lifecycle at multiple steps. Peer-reviewed articles and abstracts were searched in MEDLINE, PubMed, Embase, and clinical trial websites.

EXPERT OPINION

The exploration of small molecules that target specific pathways within the herpes lifecycle holds the potential for substantial impact on the antiviral pharmaceutical market. Simultaneously, the pursuit of disease-specific biomarkers has the capacity to usher in a transformative era in diagnostics within the field.

Mass Balance and Metabolite Profile after Single and Multiple Oral Doses of Pritelivir in Healthy Subjects

Pritelivir is a helicase-primase inhibitor active against HSV. Two human mass balance trials (a multiple-dose trial and a single-dose trial) were performed to characterize the absorption, distribution, metabolism, and excretion of 100 mg oral pritelivir combined with a single microdose of 14C-pritelivir. Blood, urine, and feces samples were collected up to 26 days postdose. The plasma half-life of pritelivir was 63-67 hours. Overall, 92% and 66% of the administered dose was recovered in the multiple and single dose trials, respectively. The low recovery after the single dose (66%) was most likely related to the formulation used. The major metabolic pathway was amide hydrolysis leading to amino thiazole sulfonamide (ATS) and pyridinyl phenyl acetic acid (PPA). In plasma, pritelivir, ATS, PPA, and PPA-acyl glucuronide accounted for 40.6%, 9.4%, 5.1%, and 0.2% of total radioactivity. More than 90% of drug-related material was eliminated 624 hours postdose. The majority was excreted in urine (75% and 77%), followed by feces (16% and 23%). The main components in urine were PPA-acyl glucuronide (and its isomers), ATS, and its N-demethylated isomers. Only minor metabolites were observed in feces. In conclusion, the major metabolic pathways of pritelivir have been identified with the primary excretion route being renal.

A Multicenter Assessment of the Outcomes and Toxicities of Foscarnet for Treatment of Acyclovir-Resistant Mucocutaneous Herpes Simplex in Immunocompromised Patients

Background

Acyclovir-resistant mucocutaneous herpes simplex virus (HSV) infection is an uncommon problem typically seen in immunocompromised hosts. Systemic treatment options are limited. The performance of foscarnet and its toxicities in this population are poorly characterized.

Methods

This was a multicenter retrospective study of adults treated with foscarnet for HSV infection between January 2012 and December 2017. Relevant data were collected including demographics, baseline conditions, previous anti-HSV medications, concomitant medications, HSV outcomes, and adverse events. Acyclovir-resistant HSV infection was defined based on genotypic or phenotypic testing results; refractory infection was defined as infection not improving after 5 days of treatment-dosed antiviral therapy in those not tested for resistance.

Results

Twenty-nine patients had 31 episodes of HSV (15/18 resistant; among episodes without resistance testing, 7/10 refractory; 3 not evaluable) treated with foscarnet. All patients were immunocompromised including 19 (66%) with hematologic malignancy and 9 (31%) with HIV. Median duration of foscarnet was 16 days (range, 6-85 days). Fifteen episodes (48%) healed by the end of or after foscarnet. Median time to healing among those with resolution was 38 days (range, 9-1088 days). At least 1 adverse event during therapy was reported in 26 (84%) treatment episodes including 23 (74%) that were considered drug related. Common adverse events were electrolyte disturbance (20 [65%]) and kidney dysfunction (13 [42%]). Foscarnet was discontinued in 10 episodes (32%) due to an adverse event, including 6 due to kidney dysfunction.

Conclusions

Among 31 episodes of HSV treated with foscarnet, only half resolved with treatment, and adverse events were common.

In vitro evaluation of inhibitory effect of Lactobacillus reuteri supernatant on the replication of herpes simplex virus type 1 and expression of UL54, UL52 and UL27 genes

Background and Objectives

Human herpes virus type 1 (HSV-1) is a neurotropic pathogen that is infected more than 70% of the world population. The increasing of viral resistance to antiviral drugs and the emergence of side effects has motivated researchers to study the use of probiotics as new antiviral agents. The aim of the present study was to study for the first time the potential antiviral activity of Lactobacillus reuteri (L. reuteri) supernatant against HSV-1.

Materials and Methods

After measuring the cytotoxicity of L. reuteri supernatant by MTT assay, 1:16 dilution of it was added to HeLa cells before and after HSV-1 infection, after 1.5 hours incubation with HSV-1, and simultaneously with HSV-1 infection. After 48 hours of incubation at 37°C, the viral titer and expression levels of UL54, UL52 and UL27 genes were measured by tissue culture infectious dose 50 (TCID50 ) and Real-Time PCR methods, respectively.

Results

HSV-1 titer in the treatment conditions before infection, incubation with HSV-1, simultaneously with infection and after infection was reduced by 0.42, 3.42, 1.83, and 0.83 log 10 TCID50/ml, respectively. When the bacterial supernatant was first incubated with the virus and then added to the cell, or when it was added simultaneously with the virus, the expression of the UL27, UL52, and UL54 genes decreased significantly (p<0.05). When the bacterial supernatant is added to the cell before or after virus infection, the expression of UL52 and UL54 genes does not change significantly (P>0.05).

Conclusion

The study findings indicated that the supernatant of L. reuteri has a potent anti-HSV-1 effect especially if it is incubated with the virus before inoculation into the cell. Its possible antiviral mechanism is to inhibit the virus by binding to it or changing the surface structure of the virus. Metabolites of L. reuteri can be considered as a novel inhibitor of HSV-1 infection.

Preparation and characterization of ι-carrageenan nanocomposite hydrogels with dual anti-HPV and anti-bacterial activities

Sexually transmitted diseases (STDs) are usually caused by co-infections of bacteria and viruses. However, there is a lack of products that possess both antibacterial and antiviral activities without using chemical drugs. Here, we developed a carrageenan silver nanoparticle composite hydrogel (IC-AgNPs-Gel) based on the antiviral activity of iota carrageenan (IC) and the antibacterial effect of silver nanoparticles (AgNPs) to prevent STDs. IC-AgNPs-Gel showed excellent biocompatibility, hemostasis, antibacterial and antiviral effects. IC-AgNPs-Gel not only effectively prevented S. aureus, E. coli, P. aeruginosa, and C. albicans without using antibiotics, but also significantly inhibited human papilloma virus (HPV)-16 and HPV-6 without using chemotherapy drugs. Moreover, IC-AgNPs-Gel showed the effects of accelerating infected wound healing and reducing inflammation in a rat wound model infected with S. aureus. Therefore, the multifunctional hydrogel shows great potential application prospect in preventing STDs.

Combined Treatment with Host-Directed and Anticytomegaloviral Kinase Inhibitors: Mechanisms, Synergisms and Drug Resistance Barriers

Despite the availability of currently approved antiviral drugs, infections with human cytomegalovirus (HCMV) still cause clinically challenging, sometimes life-threatening situations. There is an urgent need for enhanced anti-HCMV drugs that offer improved efficacy, reduced dosages and options for long-term treatment without risk of the development of viral drug resistance. Recently, we reported the pronounced anti-HCMV efficacy of pharmacological inhibitors of cyclin-dependent kinases (CDKs), in particular, the potential of utilizing drug synergies upon combination treatment with inhibitors of host CDKs and the viral CDK-like kinase pUL97 (vCDK/pUL97). Here, we expand this finding by further assessing the in vitro synergistic antiviral interaction between vCDK and CDK inhibitors towards HCMV as well as non-human cytomegaloviruses. An extension of this synergy approach was achieved in vivo by using the recombinant MCMV-UL97/mouse model, confirming the high potential of combination treatment with the clinically approved vCDK inhibitor maribavir (MBV) and the developmental CDK7 inhibitor LDC4297. Moreover, mechanistic aspects of this synergistic drug combination were illustrated on the levels of intracellular viral protein transport and viral genome replication. The analysis of viral drug resistance did not reveal resistance formation in the case of MBV + LDC4297 combination treatment. Spanning various investigational levels, these new results strongly support our concept, employing the great potential of anti-HCMV synergistic drug treatment.

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

The pharmacokinetics and safety of the novel herpes simplex virus helicase-primase inhibitor pritelivir were evaluated in 5 phase 1 trials: a single-ascending-dose trial, 2 multiple-ascending-dose trials, a food-effect trial, and an absolute bioavailability trial in healthy male subjects. One cohort of healthy female subjects was included in the single-ascending-dose trial. Pritelivir pharmacokinetics were linear up to 480 mg following single and up to 400 mg following multiple once-daily doses. The half-life ranged from 52 to 83 hours, and steady state was reached between 8 and 13 days. Maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 1.5- and 1.1-fold higher in female compared to male subjects. Absolute bioavailability was 72% under fasted conditions. Following a fatty diet, pritelivir time to maximum concentration was 1.5 hour delayed and maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 33% and 16% higher, respectively. Pritelivir was safe and well tolerated up to 600 mg following single and up to 200 mg following multiple once-daily doses. Considering a therapeutic dose of 100 mg once-daily, pritelivir demonstrated a favorable safety and tolerability and pharmacokinetic profile in healthy subjects to support further development.

Five-Membered Heterocyclic Sulfonamides as Carbonic Anhydrase Inhibitors

The development of heterocyclic derivatives has progressed considerably over the past decades, and many new carbonic anhydrase inhibitors (CAIs) fall into this field. In particular, five-membered heterocyclic sulfonamides have been generally shown to be more effective inhibitors compared to six-membered rings ones. Despite the importance of oxygen and nitrogen five-membered heterocyclic aromatic rings in medicinal chemistry, the installation of sulfonamide moiety on such heterocycles has not received much attention. On the other hand, 1,3,4-thiadiazole/thiadiazoline ring-bearing sulfonamides are the scaffolds which have been widely used in a variety of pharmaceutically important CAIs such as acetazolamide, metazolamide and their many derivatives obtained by using the tail approach. Here, we reviewed the field focusing on the diverse biological activities of these CAIs, such as antiglaucoma, antiepileptic, antitumor and antiinfective properties. This review highlights developments involving five-membered heterocyclic sulfonamides over the last years, with a focus on their pharmacological/clinical applications.

Optimizing Antiviral Dosing for HSV and CMV Treatment in Immunocompromised Patients

Herpes simplex virus (HSV) and cytomegalovirus (CMV) are DNA viruses that are common among humans. Severely immunocompromised patients are at increased risk of developing HSV or CMV disease due to a weakened immune system. Antiviral therapy can be challenging because these drugs have a narrow therapeutic window and show significant pharmacokinetic variability. Above that, immunocompromised patients have various comorbidities like impaired renal function and are exposed to polypharmacy. This scoping review discusses the current pharmacokinetic (PK) and pharmacodynamic (PD) knowledge of antiviral drugs for HSV and CMV treatment in immunocompromised patients. HSV and CMV treatment guidelines are discussed, and multiple treatment interventions are proposed: early detection of drug resistance; optimization of dose to target concentration by therapeutic drug monitoring (TDM) of nucleoside analogs; the introduction of new antiviral drugs; alternation between compounds with different toxicity profiles; and combinations of synergistic antiviral drugs. This research will also serve as guidance for future research, which should focus on prospective evaluation of the benefit of each of these interventions in randomized controlled trials.