A randomized, controlled trial of foscarnet in the treatment of cytomegalovirus retinitis in patients with AIDS

Physicochemical Characteristics of Antimicrobials and Practical Recommendations for Intravenous Administration: A Systematic Review

Most antimicrobial drugs need an intravenous (IV) administration to achieve maximum efficacy against target pathogens. IV administration is related to complications, such as tissue infiltration and thrombo-phlebitis. This systematic review aims to provide practical recommendations about diluent, pH, osmolarity, dosage, infusion rate, vesicant properties, and phlebitis rate of the most commonly used antimicrobial drugs evaluated in randomized controlled studies (RCT) till 31 March 2023. The authors searched for available IV antimicrobial drugs in RCT in PUBMED EMBASE®, EBSCO® CINAHL®, and the Cochrane Controlled Clinical trials. Drugs' chemical features were searched online, in drug data sheets, and in scientific papers, establishing that the drugs with a pH of <5 or >9, osmolarity >600 mOsm/L, high incidence of phlebitis reported in the literature, and vesicant drugs need the adoption of utmost caution during administration. We evaluated 931 papers; 232 studies were included. A total of 82 antimicrobials were identified. Regarding antibiotics, 37 reach the "caution" criterion, as well as seven antivirals, 10 antifungals, and three antiprotozoals. In this subgroup of antimicrobials, the correct vascular access device (VAD) selection is essential to avoid complications due to the administration through a peripheral vein. Knowing the physicochemical characteristics of antimicrobials is crucial to improve the patient's safety significantly, thus avoiding administration errors and local side effects.

An overview of diagnosis and management of drug-induced hypomagnesemia

Magnesium (Mg) is commonly addressed as the "forgotten ion" in medicine. Nonetheless, hypomagnesemia should be suspected in clinical practice in patients with relevant symptomatology and also be considered a predisposing factor for the development of other electrolyte disturbances. Furthermore, chronic hypomagnesemia has been associated with diabetes mellitus and cardiovascular disease. Hypomagnesemia as a consequence of drug therapy is relatively common, with the list of drugs inducing low serum Mg levels expanding. Culprit medications linked to hypomagnesemia include antibiotics (e.g. aminoglycosides, amphotericin B), diuretics, antineoplastic drugs (cisplatin and cetuximab), calcineurin inhibitors, and proton pump inhibitors. In recent years, the mechanisms of drug-induced hypomagnesemia have been unraveled through the discovery of key Mg transporters in the gut and kidney. This narrative review of available literature focuses on the pathogenetic mechanisms underlying drug-induced hypomagnesemia in order to increase the insight of clinicians toward early diagnosis and effective management.

Classification Criteria for Cytomegalovirus Retinitis

PURPOSE

The purpose of this study was to determine classification criteria for cytomegalovirus (CMV) retinitis.

DESIGN

Machine learning of cases with CMV retinitis and 4 other infectious posterior/ panuveitides.

METHODS

Cases of infectious posterior/panuveitides were collected in an informatics-designed preliminary database, and a final database was constructed of cases achieving supermajority agreement on diagnosis using formal consensus techniques. Cases were split into a training set and a validation set. Machine learning using multinomial logistic regression was used in the training set to determine a parsimonious set of criteria that minimized the misclassification rate among the infectious posterior/panuveitides. The resulting criteria were evaluated in the validation set.

RESULTS

A total of 803 cases of infectious posterior/panuveitides, including 211 cases of CMV retinitis, were evaluated by machine learning. Key criteria for CMV retinitis included: 1) necrotizing retinitis with indistinct borders due to numerous small satellites; 2) evidence of immune compromise; and either 3) a characteristic clinical appearance, or 4) positive polymerase chain reaction assay results for CMV from an intraocular specimen. Characteristic appearances for CMV retinitis included: 1) wedge-shaped area of retinitis; 2) hemorrhagic retinitis; or 3) granular retinitis. Overall accuracy for infectious posterior/panuveitides was 92.1% in the training set and 93.3% (95% confidence interval: 88.2-96.3) in the validation set. The misclassification rates for CMV retinitis were 6.9% in the training set and 6.3% in the validation set.

CONCLUSIONS

The criteria for CMV retinitis had a low misclassification rate and appeared to perform sufficiently well for use in clinical and translational research.

Safety profile of the concomitant use of foscarnet and aerosolized pentamidine in allogeneic hematopoietic stem cell transplantation recipients

BACKGROUND

Concomitant use of foscarnet and intravenous pentamidine can very frequently cause severe hypocalcemia. However, it is unknown whether aerosolized pentamidine has a similar adverse interaction with foscarnet. The present study was aimed at examining the safety profile of concomitantly used foscarnet and aerosolized pentamidine in patients receiving allogeneic hematopoietic stem cell transplantation.

METHODS

Data from allogeneic hematopoietic stem cell recipients who had been administered foscarnet therapy for over 7 days were analyzed. We compared electrolyte abnormalities and serum creatinine level between patients who received aerosolized pentamidine concomitantly and those who did not.

RESULTS

A total of 84 consecutive patients and 135 episodes of foscarnet therapy between May 2011 and April 2016 were evaluable. Of these 135 episodes, 25 episodes of therapy included concurrent therapy with 300 mg dose of aerosolized pentamidine once a month (pentamidine group) and 110 episodes did not (non-pentamidine group). The incident rates of grade 3/4 hypocalcemia did not significantly differ between the pentamidine and non-pentamidine groups (P = .207; 0/25 [0%] vs 10/110 [9.1%], respectively). In addition, we observed no significant difference in the incident rates of grade 3/4 serum creatinine increase between the two groups (P = 1.00; 0/25 [0%] vs 4/110 [3.6%], respectively).

CONCLUSION

Our results suggest that the drug interactions between foscarnet and aerosolized pentamidine may not be clinically significant.

Cytomegalovirus retinitis in the post-cART era

Purpose of review

To review the epidemiology, diagnosis, and management of cytomegalovirus retinitis (CMVR) in the post-combined antiretroviral era (cART) era.

Recent findings

Although cART has dramatically reduced CMVR incidence and morbidity in the HIV population, CMVR continues to cause significant vision loss in both HIV and non-HIV patients, especially amongst patients without immune reconstitution. Advances in imaging including ultra-widefield fundus and autofluorescence imaging, optical coherence tomography, and adaptive optics may reflect CMVR activity; however, the diagnosis remains a clinical one. There have been minimal advances in therapy, with several agents no longer available due to market concerns.

Summary

Despite reduced incidence and morbidity in the post-cART HIV population, CMVR continues to cause vision loss amongst HIV and non-HIV patients. Diagnosis remains primarily clinical, and therapy centers upon immune reconstitution along with systemic and/or intravitreal antivirals. Further studies are necessary to determine whether advanced imaging can influence management, and whether novel antiviral agents or adoptive immune transfer have a role in treatment of drug-resistance CMVR.

Antiviral Drugs in Newborn and Children

This article focuses on the clinically relevant approved antiviral medications available for the treatment of infants and children. A brief overview of drug categories, mechanism of action, resistance, pharmacokinetics, and side effects is provided for the more commonly prescribed antivirals. The patient categories addressed are treatment and prophylaxis of influenza, neonatal herpes simplex virus and congenital cytomegalovirus, treatment and prophylaxis of viral disease in the immunocompromised host, and a brief introduction to the antivirals available to treat hepatitis B and hepatitis C in children.

Management of Cytomegalovirus Retinitis in HIV and Non-HIV Patients

As CMVR continues to affect HIV-positive and non-HIV immunosuppressed patients, ophthalmologists must continue to tailor diagnostics and therapeutics to individual cases. In HIV-related disease, ocular fluid sampling and intravitreal drug delivery are considerations, but systemic antiviral therapy is paramount in the initial management from both ophthalmic and systemic morbidity standpoints. Non-HIV-related disease should be approached with a multidisciplinary team, including an ophthalmologist/vitreoretinal/uveitis specialist for consideration of intravitreal antiviral therapy with qualitative and quantitative aqueous PCR monitoring, and consideration of PCR genome sequencing for CMV strains that may become resistant to antiviral therapies from long-term antiviral prophylactic exposure. Hematologists or oncologists may help with patients who remain bone marrow-suppressed following transplantation or systemic chemotherapy. Because of related toxicities of the anti-CMV medications and immunosuppressive medications (eg, bone marrow suppression and cytopenias), infectious disease consultation can help in the treatment and monitoring of side effects.

Intracellular Metabolism of 3′-Azido-3′-Deoxythymidine in the Presence of Ganciclovir or Foscarnet

Comparisons were made between the intracellular phosphorylation of 3′-Azido-3′-deoxythymidine (AZT) alone and in combination with ganciclovir (GCV) or foscarnet (PFA) in lymphocytes, uninfected fibroblasts and CMV-infected fibroblasts. The effects of AZT and the combinations of AZT with GCV or PFA on cellular dNTP pools were also examined. The phosphorylation of AZT was not altered by the presence of GCV or PFA in lymphocytes, and neither AZT nor the combinations of AZT with GCV or PFA changed the levels of cellular dNTP pools in these cells. AZT was phosphorylated to a greater extent in lymphocytes when compared to fibroblasts, but the proportion of AZT di- and triphosphates was greater in fibroblasts. The infection of fibroblasts with CMV enhanced AZT phosphorylation and increased the levels of cellular dNTP pools. GCV caused a specific reduction in AZT phosphorylation in CMV-infected fibroblasts, with a seven-fold drop in AZT triphosphate compared to AZT alone. GCV did not affect AZT phosphorylation in uninfected fibroblasts, nor did GCV reduce the dTTP pool compared to AZT alone. The effects of GCV upon AZT phosphorylation in CMV-infected cells may shed light on the antagonistic effects of GCV upon the anti-HIV activity of AZT, and are of importance for the development of effective combination therapies for the treatment of AIDS patients infected with CMV.

Cidofovir, a New Agent with Potent Anti-Herpesvirus Activity

Cidofovir is a potent, broad spectrum antiviral agent with activity in vitro and in vivo against cytomegalovirus and other members of the herpesvirus family, as well as certain other DNA viruses. After uptake into cells it is converted enzymatically to cidofovir diphosphate, a structural analogue of deoxycytidine triphosphate, which selectively inhibits viral DNA polymerases relative to host cell polymerases. Cross-resistance to cidofovir is not usually seen with human cytomegalovirus isolates that are foscarnet-resistant, or isolates that are ganciclovir-resistant due to a deficiency in ganciclovir phosphorylation. Cross-resistance is seen, however, with isolates that are ganciclovir resistant due to polymerase mutations. A prolonged elimination phase seen in vivo, correlates with a long intracellular half-life seen in vitro and allows for efficacy in animal models of virus infection with infrequent dosing or prophylaxis. Clinical studies of intravenous cidofovir in cytomegalovirus retinitis in patients with AIDS are claimed to show delay of retinitis progression with maintenance doses given once every 2 weeks.

Foscarnet, zidovudine and dolutegravir combination efficacy and tolerability for late stage HIV salvage therapy: A case-series experience

Salvage therapy including foscarnet (PFA), zidovudine (ZDV) and an optimized background ART (OBT) has been shown to be effective in patients with advanced HIV infection, and no therapeutic options. Dolutegravir (DTG) may offer a more active combination. Objective was to describe efficacy and tolerability of PFA-ZDV-DTG containing regimen. In our cohort, we identified patients who: (i) had plasma HIV-1 RNA load (pVL) >50 c/ml (>100 for HIV-2) on combination ART (cART); (ii) had at least 1 PI/r, 1 NRTI, 1 NNRTI (for HIV-1), and at least 1 raltegravir resistance mutations; (iii) were naive to DTG; and (iv) initiated on a PFA-ZDV-DTG containing-regimen with 48 weeks (W48) of follow-up. Out of 5 patients, 2 were infected with HIV-2. At PFA-ZDV-DTG initiation, CD4 cell count was (/mm(3) ) of 64, 40, 10, in HIV-1, and 37, 199, in HIV-2 infected patients; and pVL (log10 c/ml) of 4.8, 5.1, 4.4, in HIV-1, and 3.6, 4.2, in HIV-2 infected patients, respectively. Median OBT genotypic sensitivity score was 1.5 [1-2]. PFA was discontinued in one patient, due to an acute renal failure. At W48, one HIV-1 infected patient had a pVL <50 c/ml and two <200 c/ml; the two HIV-2 infected patients had pVL >100 c/ml. No lack of treatment adherence was observed. In treatment experienced HIV-infected patients, failing cART and without other therapeutic options, a PFA-ZDV-DTG combination therapy could be effective. Renal adverse events should be monitored.

Incidence Rate and Risk Factors for Contralateral Eye Involvement among Patients with AIDS and Cytomegalovirus Retinitis Treated with Local Therapy

PURPOSE

To calculate the incidence of, and to identify the risk factors for developing contralateral eye involvement among patients with AIDS and unilateral cytomegalovirus retinitis (CMV retinitis), who were treated, in the era of highly-active antiretroviral therapy (HAART), with repetitive intravitreal ganciclovir injections.

MATERIALS AND METHODS

The clinical records of 119 patients were included. The main outcome measurement was the occurrence of contralateral eye involvement.

RESULTS

Over a mean follow-up period of 1.6 years, the overall incidence rate of contralateral involvement was 0.17/person-year. The cumulative incidence of contralateral involvement at 6 months and 1 year was 23.8% and 28.4%, respectively. Receiving HAART at the visit before the event was associated with a decreased risk of developing contralateral retinitis (hazard ratio [HR] = 0.26, P = 0.002).

CONCLUSIONS

The use of HAART, associated with subsequent immune recovery, significantly reduced the incidence of contralateral eye involvement by approximately 75% among patients in our setting.

Cytomegalovirus: pathogen, paradigm, and puzzle

Human cytomegalovirus (CMV), one of the eight herpesviruses that commonly infect humans, is best known for its propensity to cause disease in immunocompromised patients, especially transplant recipients, patients with advanced AIDS, and congenitally infected newborns. Advances in molecular virology coupled with improvements in diagnostic methods and treatment options have vastly improved our understanding of and ability to manage CMV, but many uncertainties remain, including the mechanisms of persistence and pathogenesis and its hypothesized roles in a variety of human illnesses. Here we review recent advances that are reshaping our view and approach to this fascinating virus.

Ocular microdialysis: a continuous sampling technique to study pharmacokinetics and pharmacodynamics in the eye

The unique anatomy and physiology of the eye present many challenges to the successful development and delivery of ophthalmic drugs. Any therapeutic strategy developed to control the progression of anterior and posterior segment diseases requires continuous monitoring of effective drug concentrations in the relevant ocular tissues and fluids. Ocular microdialysis has gained popularity in recent years due to its ability to continuously monitor drug concentrations and substantially reduce the number of animals needed. The intrusive nature of ocular microdialysis experimentation has restricted these studies to animal models. This review article intends to highlight various aspects of ocular microdialysis and its relevance in examining the disposition of drugs in the anterior and posterior segments.

Cytomegalovirus retinitis and the acquired immunodeficiency syndrome--bench to bedside: LXVII Edward Jackson Memorial Lecture

PURPOSE

To update information on cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS) and to integrate information on its pathogenesis and clinical outcomes.

DESIGN

Literature review.

METHODS

Selected articles from the medical literature, particularly large epidemiologic studies, including the Johns Hopkins Cytomegalovirus Retinitis Cohort Study, the Longitudinal Study of the Ocular Complications of AIDS, and the Cytomegalovirus Retinitis and Viral Resistance Study, were reviewed. Clinical information is discussed in light of knowledge on CMV, its pathogenesis, and its interactions with human immunodeficiency virus (HIV).

RESULTS

Cytomegalovirus uses several mechanisms to evade the immune system and establish latent infection in immunologically normal hosts. With immune deficiency, such as late-stage AIDS, CMV reactivates, is disseminated to the eye, and establishes a productive infection, resulting in retinal necrosis. HIV and CMV potentiate each other: CMV accelerates HIV disease, and CMV retinitis is associated with increased mortality. Randomized clinical trials have demonstrated the efficacy of treatments for CMV retinitis. Systemically administered treatment for CMV retinitis decreases AIDS mortality. Highly active antiretroviral therapy (HAART) effectively suppresses HIV replication, resulting in immune recovery, which, if sufficient, controls retinitis without anti-CMV therapy. Resistant CMV, detected in the blood, correlates with resistant virus in the eye and is associated with worse clinical outcomes, including mortality. Host factors, including host genetics and access to care, play a role in the development of CMV retinitis.

CONCLUSIONS

Clinical outcomes of CMV retinitis in patients with AIDS are dependent on characteristics of the virus and host and on HIV-CMV interactions.

Intravitreal injection of therapeutic agents

BACKGROUND

Intravitreal injection (IVI) with administration of various pharmacological agents is a mainstay of treatment in ophthalmology for endopthalmitis, viral retinitis, age-related macular degeneration, cystoid macular edema, diabetic retinopathy, uveitis, vascular occlusions, and retinal detachment. The indications and therapeutic agents are reviewed in this study.

METHODS

A search of the English, German, and Spanish language MEDLINE database was conducted. A total of 654 references spanning the period through early 2008 were individually evaluated.

RESULTS

The advantage of the IVI technique is the ability to maximize intraocular levels of medications and to avoid the toxicities associated with systemic treatment. Intravitreal injection has been used to deliver several types of pharmacological agents into the vitreous cavity: antiinfective and antiinflammatory medications, immunomodulators, anticancer agents, gas, antivascular endothelial growth factor, and several others. The goal of this review is to provide a detailed description of the properties of numerous therapeutic agents that can be delivered through IVI, potential complications of the technique, and recommendations to avoid side effects.

CONCLUSION

The IVI technique is a valuable tool that can be tailored to the disease process of interest based on the pharmacological agent selected. This review provides the reader with a comprehensive summary of the IVI technique and its multitude of uses.

[Treatment of opportunistic infections in adolescent and adult patients infected with the human immunodeficiency virus during the era of highly active antiretroviral therapy. AIDS Study Group (GESIDA) and National AIDS Plan Expert Committee]

Despite the huge advance that highly active antiretroviral therapy has represented for the prognosis of infection by human immunodeficiency virus (HIV), opportunistic infections continue to be a cause of morbidity and mortality in HIV-infected patients. This is often the case because of severe immunodepression, poor adherence to antiretroviral therapy, failure of therapy, or the fact that patients are unaware of their HIV-positive status and debut with an opportunistic infection. This article updates the guidelines on treatment of acute episodes of various opportunistic infections in HIV-infected patients, including infections due to parasites, fungi, viruses, mycobacteria, and bacteria. This edition has a new chapter on imported parasite infections as well as additional information on endemic mycoses in the chapter on fungal infections, taking into account the growing number of immigrants in our setting. Lastly, the chapter on the immune reconstitution syndrome has also been updated, providing relevant data on a phenomenon that has clinical and diagnostic repercussions in patients who start antiretroviral therapy while they are severely immunodepressed (English version available at http://www.gesida.seimc.org).

Management of oral infections in cancer patients

The myelosuppressive and mucosal-damaging consequences of cancer and cancer therapies place patients at high risk for developing infectious complications. Bacterial, fungal, and viral infections are all commonly encountered in the oral cavity, contributing to both morbidity and mortality in this patient population. Prevention, early and definitive diagnosis, and appropriate management are critical to ensure optimal treatment outcomes. With the majority of cancer patients treated as outpatients in the community setting, oral health care professionals play an important role in managing such infectious complications of cancer therapy.

Treatment of CMV retinitis with intravitral ganciclovir in the HAART era

OBJECTIVE

To describe the course and outcome of cytomegalovirus (CMV) retinitis among AIDS patients treated with intravitreal ganciclovir and systemic highly active antiretroviral therapy (HAART). The secondary objective was to compare the course of CMV retinitis between patients receiving HAART and those not receiving this treatment.

DESIGN

A retrospective cohort design consisting of 21 eyes from 16 patients with AIDS and CMV retinitis consecutively enrolled between January 1996 and August 1999. All patients received intravitreal ganciclovir therapy, and half of the patients began HAART as well. Duration of intravitreal therapy and ensuing disease quiescence, as well as CD4+ T cell counts at diagnosis and at cessation of ganciclovir, were calculated. Secondly, instantaneous hazards for outcomes such as CMV retinitis progression, ocular complications and mortality were compared.

SETTING

Tertiary care centre in Ottawa, Ontario.

RESULTS

Five of eight patients receiving HAART discontinued intravitreal ganciclovir after a mean treatment period of 428 days. During this period, their mean CD4+ count rose from 7.5 to 190microL. Subsequently, none of these patients experienced retinitis progression during follow-up periods lasting up to 820 days (mean of 617 days). Progression of CMV retinitis was 11.4 times more likely among those not receiving HAART (P=0.049).

CONCLUSIONS

On initiating HAART, patients with CMV retinitis may enjoy significant recovery in CD4+ counts and sustained retinitis quiescence without specific anti-CMV therapy. Intravitreal ganciclovir injections seem well suited to offer effective CMV control during temporary periods of decreased CD4+ counts while awaiting HAART-mediated immune system reconstitution.

Low bone-mineral density in patients with HIV: pathogenesis and clinical significance

PURPOSE OF REVIEW: Low bone-mineral density is a recently recognized metabolic complication of HIV infection and its treatment. While the clinical impact of low bone-mineral density remains uncertain, the prolongation of survival attributable to more effective antiretroviral therapy has contributed to an aging population of HIV-infected patients who may be prone to developing fragility fractures. RECENT FINDINGS: While most of the available data are on young men, recent publications have increased our understanding of the epidemiology of low bone-mineral density and bone loss in HIV-positive women. Most studies suggest that initiation of certain combinations of antiretroviral agents may be associated with moderate bone loss initially, but bone-mineral density usually stabilizes or improves with longer follow-up. Most studies suggest that, despite lower bone-mineral density, fragility fractures are relatively uncommon in HIV-positive patients, perhaps because of their relative youth. SUMMARY: The pathogenesis of low bone-mineral density in HIV-positive patients is complex and multifactorial, and its clinical impact remains unclear. Further research is needed to clarify the approach to optimal screening and treatment of osteoporosis in the setting of HIV infection.

Treatment of cytomegalovirus retinitis with oral valganciclovir in an acquired immunodeficiency syndrome patient unresponsive to combination antiretroviral therapy

BACKGROUND

Cytomegalovirus (CMV) retinitis was a much-feared visual complication of late-stage acquired immunodeficiency syndrome (AIDS) in the past. Its incidence has waned significantly owing to the benefits of potent antiretroviral combination therapy, which for many individuals has provided some degree of immune reconstitution and avoidance of opportunistic infections, particularly this blinding disease.

CASE REPORT

A 45-year-old white man with long-standing, multidrug-resistant human immunodeficiency virus (HIV) infection and severe immunodeficiency despite multiple antiretroviral drug regimens, presented to the eye clinic reporting decreased vision and spider web patterns in his left eye for the past week. Best-corrected visual acuity was 20/20 in the right (O.D.) and 20/25 in the left eye (O.S.). Dilated funduscopic examination of the left eye found vasculitis of the midperipheral inferonasal arcade in the midperiphery, with surrounding intraretinal hemorrhage and granular retinal necrosis. Diagnosis of cytomegalovirus retinitis was made, and the patient began induction therapy with oral valganciclovir 900 mg twice a day for 3 weeks. Maintenance therapy after retinitis stabilization was 900 mg every day until any observed recurrence of infection. Three months after complete resolution of the active retinitis, the patient returned to the clinic reporting new floaters of recent onset. A reactivation of the CMV retinitis warranted a reinduction with valganciclovir 900 mg orally twice a day for 3 weeks.

CONCLUSION

This case is illustrative of the efficacy and relative ease of administration of valganciclovir, the newest medication approved for treatment and maintenance of CMV retinitis. Despite his severe immunodeficiency, our patient tolerated the induction and maintenance therapy of oral valganciclovir well, and the CMV retinitis was stabilized and resolved with full recovery of visual acuity.

Drug-induced glomerulopathies

Normal renal function depends upon an intact glomerular apparatus. Many drugs and chemicals are capable of damaging the glomerulus, causing its increased permeability to large molecules. Glomerular lesions are usually responsible for proteinuria and the nephrotic syndrome. This also holds true for the drug-induced glomerulopathies, of which membranous glomerulo-nephritis is the most frequent type of lesion encountered. Apart from this, several cases of different glomerular changes such as focal segmental glomerulosclerosis and crescentic glomerulonephritis have also been reported. The drug-induced glomerulopathies are probably immune mediated. This is, for instance, reflected in the fact that patients with drug-induced nephritic syndrome frequently have the HLA-B8 and DR3 antigens. In depth information is provided for the previously mentioned disorders.

Achievements and challenges in antiviral drug discovery

The last 40 years have seen the development of several antiviral drugs with therapeutic value in treating life-threatening or debilitating diseases such as those caused by HIV, hepatitis B virus, herpesviruses (such as herpes simplex virus and varicella zoster virus) and influenza virus. These relatively recent advances have been due to technical breakthroughs in the cultivation of viruses in the laboratory, identification of viral enzymes and, more recently, their molecular biology. We describe here the antecedence of several of the existing antivirals and their strengths and weaknesses. We indicate where the major challenges lie for future improvements of current therapies and possible new indications, such as hepatitis C virus and papillomavirus. We also describe how current antiviral therapies are restricted to a rather limited number of viral diseases of sufficient interest to the pharmaceutical industry. Finally we describe the potential threat of emerging viruses and bio-weapons and the challenges that they present to therapy.

Drug-induced hypomagnesaemia : scope and management

Nearly 50 medications have been implicated as inducing hypomagnesaemia, sometimes based on insufficient data regarding clinical significance and frequency of occurrence. In fact, clinical effects attributed to hypomagnaesemia have been reported in only 17 of these drugs. A considerable amount of literature relating to individual drugs has been published, yet a comprehensive overview of this issue is not available and the hypomagnesaemic effect of a drug could be either overemphasised or under-rated. In addition, there are neither guidelines regarding treatment, prevention and monitoring of drug-induced hypomagnesaemia nor agreement as to what serum level of magnesium may actually be defined as 'hypomagnesaemia'. By compiling data from published papers, electronic databases, textbooks and product information leaflets, we attempted to assess the clinical significance of hypomagnesaemia induced by each drug. A practical approach for managing drug-induced hypomagnesaemia, incorporating both published literature and personal experience of the physician, is proposed. When drugs classified as inducing 'significant' hypomagnesaemia (cisplatin, amphotericin B, ciclosporin) are administered, routine magnesium monitoring is warranted, preventive treatment should be considered and treatment of hypomagnesaemia should be initiated with or without overt clinical manifestations. In drugs belonging to the 'potentially significant' category, among which are amikacin, gentamicin, laxatives, pentamidine, tobramycin, tacrolimus and carboplatin, magnesium monitoring is justified when either of the following occurs: clinical manifestations are apparent; persistent hypokalaemia, hypocalcaemia or alkalosis are present; other precipitating factors for hypomagnesaemia coexist; or treatment is with more than one potentially hypomagnesaemic drug. No preventive treatment is required and treatment should be initiated only if hypomagnesaemia is accompanied by symptoms or clinically significant relevant laboratory findings. In those drugs whose hypomagnesaemic effect is labelled as 'questionable', including furosemide and hydrochlorothiazide, routine monitoring and treatment are not required.

HIV-associated retinopathy in the HAART era

BACKGROUND

The effectiveness of highly active antiretroviral therapy (HAART) in restoring immune function in patients with acquired immunodeficiency syndrome (AIDS) has led to changes in the incidence, natural history, management, and sequelae of human immunodeficiency virus (HIV)-associated retinopathies, especially cytomegalovirus (CMV) retinitis.

METHODS

The medical literature pertaining to HIV-associated retinopathies was reviewed with special attention to the differences in incidence, management strategies, and complications of these conditions in the eras both before and after the widespread use of HAART.

RESULTS

In the pre-HAART era, CMV retinitis was the most common HIV-associated retinopathy, occurring in 20%-40% of patients. Median time to progression was 47 to 104 days, mean survival after diagnosis was 6 to 10 months, and indefinite intravenous maintenance therapy was mandatory. Retinal detachment occurred in 24%-50% of patients annually. Herpetic retinopathy and toxoplasmosis retinochoroiditis occurred in 1%-3% of patients and Pneumocystis carinii choroiditis, syphilitic retinitis, tuberculous choroiditis, cryptococcal choroiditis, and intraocular lymphoma occurred infrequently. In the HAART era the incidence of CMV retinitis has declined 80% and survival after diagnosis has increased to over 1 year. Immune recovery in patients on HAART has allowed safe discontinuation of maintenance therapy in patients with regressed CMV retinitis and other HIV-associated retinopathies. Immune recovery uveitis (IRU) is a HAART dependent inflammatory response that may occur in up to 63% of patients with regressed CMV retinitis and elevated CD4 counts and is associated with vision loss from epiretinal membrane, cataract, and cystoid macular edema.

CONCLUSIONS

The incidence, visual morbidity, and mortality of CMV retinitis and other HIV-associated retinopathies have decreased in the era of HAART and lifelong maintenance therapy may safely be discontinued in patients with restored immune function. Patients with regressed CMV retinitis, however, may still lose vision from epiretinal membrane, cystoid macular edema, and cataract secondary to IRU.

Emerging therapies for herpes viral infections (types 1 – 8)

There are eight members of the herpesviridae family: herpes simplex virus-1 (HSV-1), HSV-2, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpes virus-6, human herpes virus-7 and human herpes virus-8. The diseases caused by viruses of the herpesviridae family are treated with and managed by systemic and topical antiviral therapies and immunomodulating drugs. Because these viruses establish a latent state in hosts, antiherpetic agents, such as nucleoside analogues, only control symptoms of disease or prevent outbreaks, and cannot cure the infections. There is a need for treatments that require less frequent dosing, can be taken even when lesions are more advanced than the first signs or symptoms, and can treat resistant strains of the viruses without the toxicities of existing therapies. Immunomodulating agents, such as resiquimod, can act on the viruses indirectly by inducing host production of cytokines, and can thereby reduce recurrences of herpes. The new helicase primase inhibitors, which are the first non-nucleoside antiviral compounds, are being investigated for treatment of HSV disease, including infections resistant to existing therapy.

Posterior segment manifestations of HIV/AIDS

The ocular posterior segment manifestations of AIDS may be divided into four categories: retinal vasculopathy, unusual malignancies, neuro-ophthalmologic abnormalities, and opportunistic infections. Microvasculopathy is the most common manifestation. Opportunistic infections, particularly cytomegalovirus retinitis and progressive outer retinal necrosis, are the most likely to result in visual loss due to infection or subsequent retinal detachment. Diagnosis and treatment are guided by the particular conditions and immune status of the patient.

Comparability of two fundus photograph reading centers in grading cytomegalovirus retinitis progression

PURPOSE

To compare grading of cytomegalovirus retinitis progression by two different fundus photograph reading centers (FPRCs).

DESIGN

Patients with AIDS followed in an ophthalmology service were enrolled in a prospective epidemiologic study of the prevalence and incidence of resistant cytomegalovirus in vitro.

METHODS

We compared masked replicate gradings by two different FPRCs of monthly fundus photographs for retinitis progression (onset of a separate new lesion or expansion of an existing lesion by > or =one-half disk diameter).

RESULTS

For 77 patients, Kaplan-Meier plots of progression over time were similar between FPRCs (median time to progression, 65 vs 69 days). Agreement between FPRCs was 51% (kappa [kappa] =.37, "fair") on exact visit of progression (28 patients) or on absence of progression through follow-up (11 patients) and 62% (kappa =.38) on progression visit +/- 1 month. Eight of 12 patients with progression graded as more than 1 month apart were only 2 months apart. Considering each monthly visit as a choice point, overall agreement on progression was 78% (kappa =.55, "moderate"). Baseline evaluation of retinitis showed 95% agreement on presence/absence and a concordance correlation coefficient of.75 for extent in combined zones 1 and 2. Rates of retinal loss over follow-up were estimated as 2.8%/month vs 2.0%/month (P =.015).

CONCLUSIONS

By adopting similar protocols and procedures, different FPRCs can achieve good agreement on presence and extent of cytomegalovirus retinitis. Further efforts to harmonize evaluation through ongoing comparison of gradings would likely improve agreement on retinitis progression.

HIV infection--a risk factor for osteoporosis

Osteopenia and osteoporosis have recently been described as complications of antiretroviral therapy in HIV-infected patients. The advent of highly active antiretroviral therapy in conjunction with improved standard antiviral and antibiotic regimens has dramatically changed the clinical course of HIV infection, resulting in prolonged survival. The pathogenesis and role of each individual medication are poorly understood. Avascular necrosis has also been described in AIDS patients receiving or not receiving antiretroviral therapy. This article is a clinically focused review of the literature on osteopenia, osteoporosis, and mineral metabolism related to HIV infection. In patients with HIV infection, the risks of osteopenia and osteoporosis are not very clear. The suggested risk factors for the development of osteopenia are use of protease inhibitors, longer duration of HIV infection, high viral load, high lactate levels, low bicarbonate levels, raised alkaline phosphatase level, and lower body weight before antiretroviral therapy. There have also been a few case reports of pathologic fractures in AIDS patients with antiretroviral therapy-induced osteopenia and osteoporosis. The underlying mechanism triggering bone loss in HIV-infected patients is unknown. The proinflammatory cytokines tumor necrosis factor and interleukin-6 have been found to be constitutionally produced in increased amounts in HIV-positive individuals, and they may have a role in osteoclast activation and resorption. Serum markers of bone formation are decreased and resorption is increased in patients with advanced clinical disease. Hypocalcemia, hypercalcemia, and abnormalities of the parathyroid hormone axis have been described in HIV infection. Histomorphometric analyses have shown altered bone remodeling in HIV-infected patients when compared with controls. Patients with known risk factors for osteoporosis-advancing age, low body weight, and prolonged duration of HIV infection-and those receiving protease inhibitor treatment should be considered for dual x-ray absorptiometry imaging. If bone mineral density is osteopenic or osteoporotic, then the patient should also be screened for other known medical causes of osteoporosis and consider treatment with a bisphosphonate or, if hypogonadal, testosterone replacement under close monitoring.

The human cytomegalovirus

Human cytomegalovirus (HCMV), a betaherpesvirus, represents the major infectious cause of birth defects, as well as an important pathogen for immunocompromised individuals. The viral nucleocapsid containing a linear double-stranded DNA of 230 kb is surrounded by a proteinaceous tegument, which is itself enclosed by a loosely applied lipid bilayer. Expression of the HCMV genome is controlled by a cascade of transcriptional events that leads to the synthesis of three categories of viral proteins designated as immediate-early, early, and late. Clinical manifestations can be seen following primary infection, reinfection, or reactivation. About 10% of infants are infected by the age of 6 months following transmission from their mothers via the placenta, during delivery, or by breastfeeding. HCMV is a significant post-allograft pathogen and contributes to graft loss independently from graft rejection. Histopathologic examination of necropsy tissues demonstrates that the virus enters via the epithelium of the upper alimentary, respiratory, or genitourinary tracts. Hematogenous spreading is typically followed by infection of ductal epithelial cells. Infections are kept under control by the immune system. However, total HCMV clearance is rarely achieved, and the viral genome remains at selected sites in a latent state. Virological and molecular detection of HCMV, as well as serological demonstration of a specific immune response, are used for diagnosis. Treatment of HCMV infections is difficult because there are few options. The presently available drugs produced a significant clinical improvement, but suffer from poor oral bioavailability, low potency, development of resistance in clinical practice, and dose-limiting toxicities.

A safety study of oral valganciclovir maintenance treatment of cytomegalovirus retinitis

Valganciclovir, an oral prodrug of the anti-cytomegalovirus (CMV) agent ganciclovir, was evaluated in a single-arm open-label safety study. AIDS patients (median CD4 lymphocyte count of 140 cells/microL) with treated CMV retinitis (N = 212) received 900-mg once-daily valganciclovir maintenance therapy with courses of 900-mg twice-daily valganciclovir induction therapy as needed to treat progression. After a median treatment duration of 372 days, the adverse event profile was similar to that reported for intravenous (IV) and oral ganciclovir. Adverse event rates of note were diarrhea (35%), nausea (23%), fever (18%), neutropenia (absolute neutrophil count <500 cells/microL) (10%), and anemia (hemoglobin <8.0 g/dL) (12%). Consistent with prior treatment studies of oral ganciclovir, IV catheter-related adverse events were uncommon (6%) and lower than previously reported for IV ganciclovir. The mortality rate was 0.072 deaths per patient-year. Progression of CMV retinitis occurred in 17% of patients during the study treatment period, usually in association with a low CD4 cell count. Other than a higher than expected frequency of oral candidiasis (17%), no clinical toxicities or laboratory abnormalities occurred during treatment with valganciclovir that have not been observed during treatment with ganciclovir.

A controlled trial of valganciclovir as induction therapy for cytomegalovirus retinitis

BACKGROUND

Valganciclovir is an orally administered prodrug that is rapidly hydrolyzed to ganciclovir. We compared the effects of oral valganciclovir with those of intravenous ganciclovir as induction therapy for newly diagnosed cytomegalovirus retinitis in 160 patients with the acquired immunodeficiency syndrome (AIDS).

METHODS

The primary end point was photographically determined progression of cytomegalovirus retinitis within four weeks after the initiation of treatment. Secondary end points included the achievement of a prospectively defined satisfactory response to induction therapy and the time to progression of cytomegalovirus retinitis. After four weeks, all patients received valganciclovir as maintenance therapy.

RESULTS

Eighty patients were randomly assigned to each treatment group. Of the patients who could be evaluated, 7 of 70 assigned to intravenous ganciclovir (10.0 percent) and 7 of 71 assigned to oral valganciclovir (9.9 percent) had progression of cytomegalovirus retinitis during the first four weeks (difference in proportions, 0.1 percentage point; 95 percent confidence interval, -9.7 to 10.0). Forty-seven of 61 patients (77.0 percent) assigned to intravenous ganciclovir and 46 of 64 (71.9 percent) assigned to valganciclovir had a satisfactory response to induction therapy (difference in proportions, 5.2 percentage points; 95 percent confidence interval, -20.4 to 10.1). The median times to progression of retinitis were 125 days in the group assigned to intravenous ganciclovir and 160 days in the group assigned to oral valganciclovir. The mean values for the area under the curve for the ganciclovir dosage interval were similar at both induction doses and maintenance doses. The frequency and severity of adverse events were similar in the two treatment groups.

CONCLUSIONS

Orally administered valganciclovir appears to be as effective as intravenous ganciclovir for induction treatment and is convenient and effective for the long-term management of cytomegalovirus retinitis in patients with AIDS.

Safety of intravitreous fomivirsen for treatment of cytomegalovirus retinitis in patients with AIDS

PURPOSE

To report data regarding the safety of intravitreous fomivirsen for treatment of cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS).

DESIGN

Critical review of safety data from three randomized controlled clinical trials with supplemental information from an expanded drug access program.

METHODS

Adverse ocular events reported by clinician investigators were listed using terms modified from the COSTART dictionary. Data for two doses (165-microg/injection [35 eyes, 30 patients] and 330-microg/injection [153 eyes, 120 patients]) and two 330-microg/injection dose schedules of different intensity were pooled to calculate incidence rates for each event. Rates were calculated as "events/patient-year" (based on total cumulative reported events and duration of treatment) for events that could recur during treatment. Rates were calculated as "patients with events/person-year" for the following events: retinal detachment, cataract, visual field disturbance, and retinal pigment epitheliopathy. To assess the ability to manage events, we reviewed treatments given for two events (anterior chamber inflammation, increased intraocular pressure) in one trial. We also report an analysis comparing the proportion of eyes that developed one or more key events to the cumulative number of injections.

RESULTS

Incidence rates were dose and schedule dependent (165 microg/injection, 4.06 events/patient-year; 330 microg/injection, 6.58 events/patient-year [less intense regimen] and 8.35 events/patient-year [more intense regimen]). The most frequently reported events were anterior chamber inflammation and increased intraocular pressure. We found no evidence that the proportion of patients with events increased as the number of injections increased.

CONCLUSIONS

Intravitreous fomivirsen is well tolerated with an acceptable safety profile. Adverse ocular events associated with doses and schedules used clinically can be managed successfully with medical therapy.

A randomized controlled clinical trial of intravitreous fomivirsen for treatment of newly diagnosed peripheral cytomegalovirus retinitis in patients with AIDS

PURPOSE

To assess the efficacy of intravitreous fomivirsen sodium, an antisense oligonucleotide, for newly diagnosed peripheral cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS).

DESIGN

Randomized treatment intervention clinical trial.

METHODS

A multicenter, prospective, and randomized clinical trial compared immediate treatment of CMV retinitis with fomivirsen (165 microg administered intravitreously) to deferral of treatment until CMV retinitis lesions progressed by standard definitions. Included were patients with CMV retinitis lesions at least 750 microm outside of zone 1. Fomivirsen was injected weekly for three doses as induction therapy, followed by injection every other week as maintenance therapy. All patients were examined regularly until evidence of retinitis progression. Time to first progression was determined by two independent masked fundus photography reading centers (principal outcome) and by clinician investigators based on indirect ophthalmoscopy. Patients in the deferral of treatment group were offered fomivirsen therapy at the time of clinically determined retinitis progression.

RESULTS

Patients in the immediate treatment group (n = 18) and the deferral of treatment group (n = 10) were comparable at baseline. Median time to first progression of disease for the immediate treatment group was 71 days (95% confidence interval [CI] 28 days-not determinable) and for the deferral of treatment group was 13 days (95% CI 9-15 days; P =.0001, Wilcoxon rank sum test). Progression occurred in 44% of patients in the immediate treatment group during the study compared with 70% of patients in the deferral of treatment group during the study. There were no retinal detachments among eyes treated with fomivirsen.

CONCLUSIONS

Fomivirsen is an effective treatment for CMV retinitis in patients with AIDS that utilizes a mechanism of action different than that of ganciclovir, foscarnet, and cidofovir.

Randomized dose-comparison studies of intravitreous fomivirsen for treatment of cytomegalovirus retinitis that has reactivated or is persistently active despite other therapies in patients with AIDS

PURPOSE

To compare the efficacy of two regimens of intravitreous fomivirsen for treatment of cytomegalovirus (CMV) retinitis that had reactivated or was persistently active despite other anti-CMV therapies in patients with acquired immunodeficiency syndrome (AIDS).

DESIGN

Randomized treatment intervention clinical trials.

METHODS

Two multicenter prospective randomized open-label controlled clinical trials (USA/Brazilian study; EuroCanadian study) each compared two treatment regimens of intravitreous fomivirsen (330 microg/injection), a more intense schedule (regimen A) consisting of 3 weekly injections as induction, followed by injections every 2 weeks as maintenance therapy, and a less intense schedule (regimen B), consisting of two injections at day 1 and day 15 as induction, followed by injections every 4 weeks as maintenance therapy. A total of 61 patients (67 eyes) were treated with regimen A and a total of 32 patients (39 eyes) were treated with regimen B. Time to progression was determined by masked evaluation of serial fundus photographs. The proportion of patients whose lesions became less active or inactive is described for the USA/Brazilian study as an additional measure of efficacy.

RESULTS

Results were similar for both regimens. In the USA/Brazilian study, the median time to progression was 106 days for regimen A and 267 days for regimen B (P =.2179, Wilcoxon rank sum test). In the EuroCanadian study, the median time to progression was not determinable for regimen A (25th percentile: 91 days), but was 403 days for regimen B. In the USA/Brazilian study, lesion activity decreased in 80% of patients and became inactive in 55% of patients during therapy.

CONCLUSIONS

Both regimens of intravitreous fomivirsen can be effective treatment for patients with CMV retinitis that has not been controlled by other anti-CMV drugs. The less intense regimen may be preferable in terms of convenience and safety.

High dose oral ganciclovir treatment for cytomegalovirus retinitis

BACKGROUND

The oral formulation of ganciclovir is approved at a dose of 3.0 g/day for maintenance treatment of cytomegalovirus (CMV) retinitis following an initial induction course of intravenous (IV) anti-CMV therapy. Median time to progression of CMV retinitis is 12-20 days shorter with oral compared to IV ganciclovir maintenance, likely due to the limited oral bioavailability of ganciclovir.

OBJECTIVES

We hypothesized that higher systemic drug exposures associated with increased doses of oral ganciclovir would be associated with increased efficacy.

STUDY DESIGN

Maintenance treatment of CMV retinitis with higher than standard doses of oral ganciclovir (>3.0 g/day) was studied in 281 AIDS patients with previously treated, stable retinitis randomized to 3.0, 4.5 or 6.0 g/day oral, or 5 m/kg/day IV ganciclovir. Graders unaware of treatment assignments determined retinitis progression using fundus photographs. Vision, other ophthalmic measures and safety were assessed open-label.

RESULTS

Median days to photographic progression were 41, 50, 57 and 70, respectively (P=0.052; 3.0 g vs. IV). Hazard ratios for progression relative to IV were 1.66, 1.28 and 1.19 (P=0.016 for 3.0 g). NONMEM-modeled estimates of average serum ganciclovir concentration area under the curve (AUC(0-24)) correlated best with time to progression (P=0.0019). Six grams per day oral ganciclovir was most similar in efficacy to IV, although broad confidence intervals prevented a conclusive comparison. Patients receiving oral ganciclovir had a lower frequency of sepsis and IV catheter events.

CONCLUSIONS

This study suggests that the efficacy of ganciclovir for the maintenance treatment of CMV retinitis improves with increasing total drug exposure (measured as average serum concentration AUC(0-24)). All four regimens of ganciclovir were reasonably well tolerated, with safety profiles similar to what has been reported in prior work.

Engineered RNase P ribozymes inhibit gene expression and growth of cytomegalovirus by increasing rate of cleavage and substrate binding

We have previously employed an in vitro (genetic) selection procedure to select RNase P ribozyme variants for their activity in cleaving a mRNA substrate from a pool of ribozymes containing randomized sequences. In this study, one of the variants was used to target the overlapping region of the mRNAs encoding the major transcription regulatory proteins, IE1 and IE2, of human cytomegalovirus (HCMV). The ribozyme variant exhibited an enhanced substrate binding and rate of chemical cleavage, and was at least 25 times more efficient in cleaving the target mRNA in vitro than the ribozyme derived from the wild-type sequence. Our results provide the first direct evidence that a point mutation at nucleotide 86 of RNase P catalytic RNA from Escherichia coli (A(86)-->C(86)) increases the rate of chemical cleavage while another mutation at nucleotide 205 (G(205)-->C(205)) enhances substrate binding of the ribozyme. Moreover, the variant was also more effective in inhibiting IE1 and IE2 expression and HCMV growth in cultured cells. A reduction of more than 97% in IE1 and IE2 expression and a reduction of 3000-fold in viral growth were observed in cells expressing the variant. Thus, RNase P ribozyme variant is highly effective in inhibiting HCMV gene expression and growth. Our results provide the direct evidence that increasing the rate of chemical cleavage and substrate-binding affinity of the ribozymes should lead to an improvement of their anti-HCMV efficacy. Moreover, our data also suggest that highly effective anti-HCMV ribozyme variants can be developed using genetic engineering approaches including in vitro selection.

Inhibition of ganciclovir-susceptible and -resistant human cytomegalovirus clinical isolates by the benzimidazole L-riboside 1263W94

The average 50% inhibitory concentration (IC(50)) values for AD169 were 0.22 +/- 0.09 microM 1263W94 and 5.36 +/- 0.12 microM ganciclovir. For 35 human cytomegalovirus (HCMV) clinical isolates the average IC(50) was 0.42 +/- 0.09 microM 1263W94, and for 26 ganciclovir-susceptible HCMV clinical isolates the average IC(50) was 3.78 +/- 1.62 microM ganciclovir. Nine HCMV clinical isolates that were resistant to ganciclovir were completely susceptible to 1263W94.