Acyclovir-resistant Herpes Simplex Virus Infection Research Articles

Management of Refractory/Resistant Herpes Simplex Virus Infections in Haematopoietic Stem Cell Transplantation Recipients: A Literature Review.

Herpes simplex virus (HSV) infections in allogeneic haematopoietic stem cell transplantation (HSCT) recipients pose significant challenges, with higher incidence, severity, and risk of emergence of resistance to antivirals due to impaired T-cell mediated immunity. This literature review focuses on acyclovir-refractory/resistant HSV infections in HSCT recipients. The review addresses the efficacy of antiviral prophylaxis, the incidence of acyclovir-refractory/resistant HSV infections, and the identification of risk factors and potential prognostic impact associated with those infections. Additionally, alternative therapeutic options are discussed. While acyclovir prophylaxis demonstrates a significant benefit in reducing HSV infections in HSCT recipients and, in some cases, overall mortality, concerns arise about the emergence of drug-resistant HSV strains. Our systematic review reports a median incidence of acyclovir-resistant HSV infections of 16.1%, with an increasing trend in recent years. Despite limitations in available studies, potential risk factors of emergence of HSV resistance to acyclovir include human leucocyte antigen (HLA) mismatches, myeloid neoplasms and acute leukaemias, and graft-versus-host disease (GVHD). Limited evidences suggest a potentially poorer prognosis for allogeneic HSCT recipients with acyclovir-refractory/resistant HSV infection. Alternative therapeutic approaches, such as foscarnet, cidofovir, topical cidofovir, optimised acyclovir dosing, and helicase-primase inhibitors offer promising options but require further investigations. Overall, larger studies are needed to refine preventive and therapeutic strategies for acyclovir-refractory/resistant HSV infections in allogeneic HSCT recipients and to identify those at higher risk.

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.

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

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

Management of oral herpes simplex virus infections: The problem of resistance. A narrative review.

Herpes Simplex Virus (HSV) type 1 (HSV-1) and type 2 (HSV-2) are among the most common human viral pathogens, affecting several billion people worldwide. Although in healthy patients clinical signs and symptoms of HSV infection are usually mild and self-limiting, HSV-infections in immunocompromised patients are frequently more aggressive, persistent, and even life-threatening. Acyclovir and its derivatives are the gold standard antiviral drugs for the prevention and treatment of HSV infections. Although the development of acyclovir resistance is a rather uncommon condition, it may be associated with serious complications, especially in immunocompromised patients. In this review, we aim to address the problem of drug resistant HSV infection and discuss the available alternative therapeutic interventions. All relative studies concerning alternative treatment modalities of acyclovir resistant HSV infection published in PubMed between 1989 to 2022 were reviewed. Long-term treatment and prophylaxis with antiviral agents predisposes to drug resistance, especially in immunocompromised patients. Cidofovir and foscarnet could serve as alternative treatments in these cases. Although rare, acyclovir resistance may be associated with severe complications. Hopefully, in the future, novel antiviral drugs and vaccines will be available in order to avoid the existing drug resistance.

Medicinal plants and natural compounds against acyclovir-resistant HSV infections.

Herpes simplex virus (HSV), an alphaherpesvirus, is highly prevalent in the human population and is known to cause oral and genital herpes and various complications. Represented by acyclovir (ACV), nucleoside analogs have been the main clinical treatment against HSV infection thus far. However, due to prolonged and excessive use, HSV has developed ACV-resistant strains. Therefore, effective treatment against ACV-resistant HSV strains is urgently needed. In this review, we summarized the plant extracts and natural compounds that inhibited ACV-resistant HSV infection and their mechanism of action.

Helicase-primase inhibitors from Medshine Discovery Inc. (WO2018/127207 and WO2020/007355) for the treatment of herpes simplex virus infections – structure proposal for Phaeno Therapeutics drug candidate HN0037

ABSTRACT Helicase-primase is an interesting target for small-molecule therapy of herpes simplex virus (HSV) infections. With amenamevir already approved for varicella-zoster virus and with pritelivir’s granted breakthrough therapy designation for the treatment of acyclovir-resistant HSV infections in immunocompromised patients, the target has sparked interest for me-too approaches. We describe the opportunities and limitations of the helicase-primase inhibitor patent portfolio from Phaeno Therapeutics and propose the structure of their drug candidate HN0037, which has been in-licensed from Medshine Discovery.

Delay of alternative antiviral therapy and poor outcomes of acyclovir-resistant herpes simplex virus infections in recipients of allogeneic stem cell transplant - a retrospective study.

Acyclovir is commonly used to prevent and treat herpes simplex virus (HSV) reactivation after hematopoietic cell transplant (HCT), and only few reports have been published on acyclovir-resistant HSV in HCT recipients. We reviewed the medical records of patients with a microbiologic diagnosis of acyclovir-resistant HSV by plaque reduction test who received an HCT from 2002 through 2014. A total of 4 028 HCTs were performed during the study period, and 18 of the recipients met the diagnostic criteria for acyclovir-resistant HSV. All cases had undergone allogeneic HCTs. Most patients were in the pre-engraftment period or on systemic corticosteroid therapy for graft-versus-host disease (GVHD). The median time between diagnosis and susceptibility testing was 15 days, and antiviral therapy was changed at a median of 27 days. Patients required prolonged therapy (~80 days), and many had serious complications including renal failure and hospitalization. In conclusion, acyclovir-resistant HSV infection is more likely during the period of profound deficit in T-cell-mediated immunity and is associated with significant morbidities. Higher doses of acyclovir prophylaxis might be needed for patients with history of HSV during pre-engraftment or GVHD treatment. In patients who do not respond or progress after 1 week of acyclovir therapy, testing for drug-resistant HSV, and early switch to an alternative antiviral should be considered.

Brincidofovir (CMX-001) for refractory and resistant CMV and HSV infections in immunocompromised cancer patients: A single-center experience

BackgroundThe emergence of resistance to available antiviral drugs may cause higher Cytomegalovirus (CMV)-associated morbidity and mortality in hematopoietic cell transplant (HCT) recipients. Few novel antiviral drugs are being developed with potential effect against refractory or resistant CMV infections. Brincidofovir, an oral nucleotide analog and prodrug of cidofovir, has shown in vitro activity against CMV. MethodsWe reviewed data of 4 cancer patients with resistant CMV or herpes simplex virus (HSV) infections and were treated with brincidofovir under emergency IND application. ResultsThree out of the 4 patients with resistant CMV or HSV infections responded to brincidofovir. Brincidofovir achieved virological response in 2 patients with confirmed UL97 mutation (ganciclovir-resistant CMV infection), but failed to control CMV when a specific UL54 mutation was present (conferring resistance to foscarnet and cidofovir), as seen with patient 3. Furthermore, brincidofovir was effective for treatment of acyclovir resistant HSV infection, as described in patient 4 which is in alignment with the high in vitro potency of brincidofovir (about 100-fold more than acyclovir) for inhibition of HSV replication. Only one patient had brincidofovir-related diarrhea without any evidence of concurrent gastrointestinal GVHD. ConclusionWithout the nephrotoxicity of cidofovir, brincidofovir could be an effective alternative for CMV-resistant and HSV-resistant infections. Combination therapy of brincidofovir with other antiviral agent, at a conventional or a lower dose, could be considered to potentiate efficacy and minimize side effects of the approved antiviral agents.

Long-term follow-up of HIV-infected patients once diagnosed with acyclovir-resistant herpes simplex virus infection

Acyclovir-resistant herpes simplex virus (HSV) infection is common in immunocompromised patients, but the course of such infection is little known. We describe the long-term follow-up of HIV-infected patients diagnosed once with acyclovir-resistant HSV infections. We retrospectively studied all HIV-infected patients between 2000 and 2010 diagnosed with virologically confirmed acyclovir-resistant HSV infection. Patients' socio-demographic and immunovirological characteristics were described. Response to foscarnet or cidofovir and recurrences were reported. Among 5295 HIV-infected patients, 13 (0.2%) were once diagnosed with an acyclovir-resistant HSV infection. Twelve patients were men, nine patients were of African origin. All patients reported previous acyclovir exposure and median CD4 count was 183 cells/mm(3) Ten patients presented exclusively with cutaneous lesions. Initially, 11 patients were treated with foscarnet and two with cidofovir. The median follow-up was 67 months (6-145). All patients recurred, 10 presenting at least one acyclovir-resistant HSV recurrence. The median number of acyclovir-resistant HSV recurrences per patient was 2 (0 - 5). Regarding the first and second recurrences, 7/13 (54%) and 5/11 (45%) HSV clinical isolates exhibited resistance to acyclovir, respectively. Acyclovir-resistant HSV infection prevalence was low in our cohort. The rate of acyclovir-resistant HSV episodes averaged 50% during the two first recurrences.

Treatment of Severe Acyclovir-Resistant Herpes Simplex Virus Infection with Continuous Infusion of High Dose Acyclovir Following Hematopoietic Cell Transplantation.

Abstract 2224Poster Board II-201Although acyclovir (ACV)-resistant herpes simplex virus (HSV) occurs in healthy patients, higher rates have been reported in 7-27% of immunocompromised patients, particularly in the setting of acyclovir prophylaxis. Infection due to ACV-resistant HSV (ACV-R HSV) is frequently severe and poses challenges to treatment, particularly following hematopoietic cell transplantation (HCT). Unfortunately, currently available alternative therapies including foscarnet, cidofovir, and ganciclovir are frequently limited by their toxicity profile. We present a series of five HCT patients from 1997-2008 with severe infections due to ACV-R HSV who were successfully treated with continuous infusion of high dose acyclovir. A Pubmed search of published literature from 1948-2009 confirmed this as the first report of ACV-R HSV in HCT patients treated with this regimen.The characteristics of the patients are summarized in the table. Patients ranged in age from 24 to 55 and had undergone an allogeneic HCT following a myeloablative preparative regimen. All grafts were composed of peripheral blood hematopoietic cells. Underlying diseases included acute myelogenous leukemia, myelodysplastic syndrome, and essential thrombocytosis. Four of the five patients were receiving treatment for GVHD of the skin (grades 2-4), with regimens that included varying doses of prednisone. Infection was due to HSV-1 in three patients and HSV-2 in two. In vitro testing revealed that high median inhibitory concentrations were necessary to inhibit viral replication by 50% (MIC50) for all five isolates consistent with resistance to acyclovir, ganciclovir, and foscarnet. Failed HSV treatment regimens included standard, intermittent doses of acyclovir (5-10 mg/kg IV every eight hours), foscarnet, cidofovir, and/or famciclovir. Adverse reactions to these agents included severe renal insufficiency, hyponatremia, and neutropenia. The doses of ACV administered via continuous infusion ranged from 30 to 50 mg/kg per day, and time to resolution of lesions ranged from 1 week to 2 months. No patients experienced toxicity associated with continuous infusion of high dose acyclovir and therapy could be continued as an outpatient when appropriate.Age, sexDiseaseHCT TypeConcomitant risk factorsHSV Serotype, locationMIC50(mcg/mL)Failed HSV Treatment Regimens***High-dose continuous ACV (mg/kg/d)Outcome, Time to responseGVHDPREDOtherACVGCVFOS37, FAMLTCD URD MASkin, Grade 2 GI<0.5 mg/k/dCSAHSV-2; genitalia102222ACV IV FOS IV CID IV30Resolved; 3 weeks47, FMDS, AMLURD MASkin, Grade 4<0.5-2 mg/k/dFK506 MMFHSV-2; genitalia, buttocks, upper thighs>48>48>200ACV IV FOS IV45Resolved; 2 months55, FMDSURD MASkin, Grade 250 mg qdTAC MMFHSV-1; Oro-pharynx>48>48>48ACV IV FOS IV30Resolved; 1 week44, FET, AMLURD MASkin, Grade 460 mg qdPrografHSV-1; Tongue>48>48>48ACV IV FAM PO30 - 50Partially resolved***24, MATMRD MANoneNoneCSA ATGHSV-1 Nare>48>48>100ACV PO FAM PO30Resolved; 1 week*All pts received allogeneic transplants and HSV prophylactic regimen of acyclovir**Dose ranges: Acyclovir 400 mg po 5x qd to 10 mg/kg IV q 8 hrs; cidofovir 5 mg/kg q week; foscarnet 40 mg/kg qd to 25 mg/kg q 12 hrs; famciclovir 500 mg po bid to 1000 mg po tid***Patient expired prior to resolution of lesions MDS = myelodysplastic syndrome; AML = acute myelogenous leukemia; URD = unrelated donor; MRD = matched-related donor; TCD = T-cell depleted; MA = myeloablative; ET = Essential thrombocytosis, AT = Amegakarocytic thrombocytopenia PRED = prednisone PO ; ACV = acyclovir, GCV = ganciclovir; FOS = foscarnet; CID = cidofovir; FAM = famciclovir; TAC = tacrolimus Conclusions:Continuous infusion of high dose acyclovir for acyclovir resistant HSV is an attractive and more tolerable alternative for patients failing standard dose intermittent infusion acyclovir or intolerant of alternative standard therapies such as foscarnet, cidofovir, or ganciclovir. At this time it is not clear how the altered pharmacokinetics that results from continuous infusion of high doses of acyclovir overcomes viral resistance. We are currently investigating the mechanisms by which the sustained levels of ACV provide this therapeutic advantage. Disclosures:No relevant conflicts of interest to declare.

Emergence of UL97 mutations in AIDS patients with CMV infection before or after the introduction of highly active antiretroviral therapy (HAART)

The emergence of resistance to available antiviral drugs may cause higher Cytomegalovirus (CMV)-associated morbidity and mortality in hematopoietic cell transplant (HCT) recipients. Few novel antiviral drugs are being developed with potential effect against refractory or resistant CMV infections. Brincidofovir, an oral nucleotide analog and prodrug of cidofovir, has shown in vitro activity against CMV.We reviewed data of 4 cancer patients with resistant CMV or herpes simplex virus (HSV) infections and were treated with brincidofovir under emergency IND application.Three out of the 4 patients with resistant CMV or HSV infections responded to brincidofovir. Brincidofovir achieved virological response in 2 patients with confirmed UL97 mutation (ganciclovir-resistant CMV infection), but failed to control CMV when a specific UL54 mutation was present (conferring resistance to foscarnet and cidofovir), as seen with patient 3. Furthermore, brincidofovir was effective for treatment of acyclovir resistant HSV infection, as described in patient 4 which is in alignment with the high in vitro potency of brincidofovir (about 100-fold more than acyclovir) for inhibition of HSV replication. Only one patient had brincidofovir-related diarrhea without any evidence of concurrent gastrointestinal GVHD.Without the nephrotoxicity of cidofovir, brincidofovir could be an effective alternative for CMV-resistant and HSV-resistant infections. Combination therapy of brincidofovir with other antiviral agent, at a conventional or a lower dose, could be considered to potentiate efficacy and minimize side effects of the approved antiviral agents.

Topical Cidofovir for Resistant Herpes

Topical cidofovir gel applied once daily is more effective than placebo for acyclovir-resistant herpes simplex virus (HSV) disease. Therapy for acyclovir-resistant HSV infection continues to be unsatisfactory, with intravenous foscarnet the only reliably active treatment. Topical trifluridine is effective against small lesions but must be applied frequently and is difficult to apply evenly to mucocutaneous lesions. Given the …

Use of human renal proximal tubule cell cultures for studying foscarnet-induced nephrotoxicity in vitro.

Foscarnet is an antiviral agent used for the treatment of cytomegalovirus retinitis and acyclovir-resistant herpes simplex virus infections in AIDS patients. Renal impairment has been reported for many patients treated with foscarnet. We have studied the effects of foscarnet on the viability (estimated by neutral red inclusion) and ultrastructure of cultures of human renal proximal tubule cells (HRPTC) isolated from the kidneys of five cadavers and cultured. The degree of foscarnet-induced toxicity was dose dependent and varied among the HRPTC cultures. The data obtained by using the in vitro system of HRPTC mimic the data of the clinical trials in that there is a dose-dependent individual variation among human cases in response to foscarnet treatment. Thus, these cultures are extremely well-suited to investigations of the mechanism of toxicity at the subcellular level.

Potential for combined therapy with 348U87, a ribonucleotide reductase inhibitor, and acyclovir as treatment for acyclovir-resistant herpes simplex virus infection.

Inhibitors of the ribonucleotide reductase of herpes simplex viruses (HSV) potentiate the activity of acyclovir in vitro and in animal studies. In addition, the combination of the ribonucleotide reductase inhibitor 348U87 and acyclovir has synergistic therapeutic effects against infections in mice due to thymidine kinase-deficient, thymidine kinase-altered, and DNA polymerase mutants of HSV. We performed a pilot study of topical combination therapy with 348U87 (3%) and acyclovir (5%) cream for acyclovir-resistant, anogenital HSV infections in ten human immunodeficiency virus (HIV)-infected patients. Our results, with lack of complete reepitheliazation of lesions in all patients and poor virologic response, suggest that this therapy is unlikely to be useful for this indication.

Foscarnet treatment of acyclovir-resistant herpes simplex virus infection in patients with acquired immunodeficiency syndrome: Preliminary results of a controlled, randomized, regimen-comparative trial

Herpes simplex virus (HSV) resistant to acyclovir can produce persistent mucocutaneous ulcerative disease in patients with the acquired immunodeficiency syndrome (AIDS). The incidence of clinically significant acyclovir-resistant HSV disease has dramatically increased since the advent of the AIDS epidemic. The primary mechanism of acyclovir resistance is induction of viral mutants defective or deficient in thymidine kinase, the viral-encoded enzyme, which catalyzes the rate-limiting step in the triphosphorylation of acyclovir to its active form (acyclovir triphosphate). Foscarnet, a potent inhibitor of HSV DNA polymerase, does not require phosphorylation for its antiviral activity. This compound has been found to be effective in the treatment of acyclovir-resistant HSV infection by several investigators. A recently completed dose-comparative trial of foscarnet in AIDS patients with acyclovir-resistant HSV has confirmed the safety and efficacy of two doses of foscarnet (40 mg/kg every 8 or 12 hours) in the treatment of this disease, as well as providing preliminary evidence supporting the utility of foscarnet maintenance therapy in delaying recurrence of HSV lesions. Analysis of data from this trial has been complicated by the tremendous variability in lesion size at initiation of therapy, making any statistically valid comparison of treatment regimens almost impossible. A further trial in AIDS patients with acyclovir-resistant HSV infection has been designed to define better the role of foscarnet maintenance and, in light of evidence that a significant proportion of initial recurrences are due to acyclovir-sensitive HSV, to examine the potential utility of acyclovir maintenance following foscarnet induction therapy.

Management of patients following successful healing of acyclovir-resistant herpes simplex virus infection

Management of patients following successful healing of acyclovir-resistant herpes simplex virus infection

Acyclovir-Resistant Herpes Simplex Virus Infections in Patients with the Acquired Immunodeficiency Syndrome

RECURRENT herpes simplex virus (HSV) infections are frequent in patients with the acquired immunodeficiency syndrome (AIDS). Although they are usually self-limiting in the normal host, such infections may produce extensive and persistent ulcerative disease in compromised hosts.1 Several studies have demonstrated the beneficial effects of systemic acyclovir in severe HSV infections in immunodeficient patients, and this drug has become the antiviral agent of choice in the treatment of such infections.2 3 4 5 6 Virtually all HSV strains isolated from patients with acute HSV infections are highly susceptible to acyclovir, but acyclovir-resistant strains have been recovered occasionally from persons who have received prolonged therapy . . .