Randomized, controlled study of the safety and efficacy of intravenous cidofovir for the treatment of relapsing cytomegalovirus retinitis in patients with AIDS

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.

Tribute to John C. Martin at the Twentieth Anniversary of the Breakthrough of Tenofovir in the Treatment of HIV Infections

At Bristol-Myers (BM) (1985–1990), John C. Martin started his HIV career with directing the clinical development of didanosine (ddI) and stavudine (d4T). During this period, he became aware of the acyclic nucleoside phosphonates (ANPs), such as (S)-HPMPA and PMEA, as potential antiviral drugs. Under his impulse, BM got involved in the evaluation of these ANPs, but the merger of BM with Squibb (to become BMS) incited John to leave BM and join Gilead Sciences, and the portfolio of the ANPs followed the transition. At Gilead, John succeeded in obtaining the approval from the US FDA for the use of cidofovir in the treatment of cytomegalovirus (CMV) retinitis in AIDS patients, which was reminiscent of John’s first experience with ganciclovir (at Syntex) as an anti-CMV agent. At Gilead, John would then engineer the development of tenofovir, first as TDF (tenofovir disoproxil fumarate) and then as TAF (tenofovir alafenamide) and various combinations thereof, for the treatment of HIV infections (i), TDF and TAF for the treatment of hepatitis B (HBV) infections (ii), and TDF and TAF in combination with emtricitabine for the prophylaxis of HIV infections (iii).

Alkoxylalkyl Esters of Nucleotide Analogs Inhibit Polyomavirus DNA Replication and Large T Antigen Activities

Polyomavirus infections occur commonly in humans and are normally nonfatal. However, in immunocompromised individuals, they are intractable and frequently fatal. Due to a lack of approved drugs to treat polyomavirus infections, cidofovir, a phosphonate nucleotide analog approved to treat cytomegalovirus infections, has been repurposed as an antipolyomavirus agent. Cidofovir has been modified in various ways to improve its efficacies as a broad-spectrum antiviral agent. However, the actual mechanisms and targets of cidofovir and its modified derivatives as antipolyomavirus agents are still under research. Here, polyomavirus large tumor antigen (Tag) activities were identified as the viral target of cidofovir derivatives. The alkoxyalkyl ester derivatives of cidofovir efficiently inhibit polyomavirus DNA replication in cell-free human extracts and a viral in vitro replication system utilizing only purified proteins. We present evidence that DNA helicase and DNA binding activities of polyomavirus Tags are diminished in the presence of low concentrations of alkoxyalkyl ester derivatives of cidofovir, suggesting that the inhibition of viral DNA replication is at least in part mediated by inhibiting single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) binding activities of Tags. These findings show that the alkoxyalkyl ester derivatives of cidofovir are effective in vitro without undergoing further conversions, and we conclude that the inhibitory mechanisms of nucleotide analog-based drugs are more complex than previously believed.

Overview of Biologically Active Nucleoside Phosphonates

The use of the phosphonate motif featuring a carbon-phosphorous bond as bioisosteric replacement of the labile P–O bond is widely recognized as an attractive structural concept in different areas of medicinal chemistry, since it addresses the very fundamental principles of enzymatic stability and minimized metabolic activation. This review discusses the most influential successes in drug design with special emphasis on nucleoside phosphonates and their prodrugs as antiviral and cancer treatment agents. A description of structurally related analogs able to interfere with the transmission of other infectious diseases caused by pathogens like bacteria and parasites will then follow. Finally, molecules acting as agonists/antagonists of P2X and P2Y receptors along with nucleotidase inhibitors will also be covered. This review aims to guide readers through the fundamentals of nucleoside phosphonate therapeutics in order to inspire the future design of molecules to target infections that are refractory to currently available therapeutic options.

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.

N(4)-Acyl derivatives as lipophilic prodrugs of cidofovir and its 5-azacytosine analogue, (S)-HPMP-5-azaC: chemistry and antiviral activity

Even number fatty acid residues-docosanoyl (behenoyl) and stearoyl were selected for introduction to the N(4)-position of (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine) (HPMPC, cidofovir), and its 5-azacytosine counterpart, (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine) (HPMP-5-azaC) with the aim to prepare a new type of lipophilic prodrugs. The study on the influence of these modifications to the stability and biological activity of both antivirals was performed. Different reactivity of both systems towards acylation reactions was also found: the 4-NH2 group of cidofovir was more reactive compared to that of HPMP-5-azaC. In 5-azacytosine derivatives, we found mostly a destabilizing effect of the N(4)-acylation but this could be compensated by a positive influence of the esterification of the phosphonate group. Chemical stability of the 5-azacytosine moiety in the HPMP series is increasing in the following order: HPMP-5-azaC<cyclic HPMP-5-azaC<HPMP-5-azaC esters. From the view of prodrug development, the best chemical stability was observed in case of the double prodrug 7: the N(4)-behenoyl derivative of the hexadecyloxyethyl ester of cyclic HPMP-5-azaC. The free phosphonic acid (N(4)-behenoyl-HPMPC) appeared to be a more potent and selective inhibitor of herpesvirus replication than the parent HPMPC derivative.

Single-dose pharmacokinetics of cidofovir in continuous venovenous hemofiltration

Dosage recommendations for cidofovir are available for renally competent as well as impaired patients; however, there are no data for patients undergoing continuous renal replacement therapy. We determined the single-dose concentration-versus-time profile of cidofovir in a critically ill patient undergoing continuous venovenous hemofiltration (CVVH). One dose of 450 mg cidofovir (5 mg/kg) was administered intravenously due to a proven cytomegalovirus (CMV) infection and failure of first-line antiviral therapy. Additionally, 2 g of probenecid was administered orally 3 h prior to and 1 g was administered 2 h as well as 8 h after completion of the infusion. The concentrations of cidofovir in serum and ultrafiltrate were assessed by high-performance liquid chromatography. The peak serum concentration measured at 60 min postinfusion was 28.01 mg/liter at the arterial port. The trough serum level was 19.33 mg/liter at the arterial port after 24 h. The value of the area under the concentration-versus-time curve from 0 to 24 h was 543.8 mg·h/liter. The total body clearance was 2.46 ml/h/kg, and the elimination half-life time was 53.32 h. The sieving coefficient was 0.138±0.022. Total removal of the drug was 30.99% after 24 h. Because of these data, which give us a rough idea of the concentration profile of cidofovir in patients undergoing CVVH, a toxic accumulation of the drug following repeated doses may be expected. Further trials have to be done to determine the right dosage of cidofovir in patients undergoing CVVH to avoid toxic accumulation of the drug.

Comparison of the safety and pharmacokinetics of ST-246® after i.v. infusion or oral administration in mice, rabbits and monkeys

BACKGROUND

ST-246® is an antiviral, orally bioavailable small molecule in clinical development for treatment of orthopoxvirus infections. An intravenous (i.v.) formulation may be required for some hospitalized patients who are unable to take oral medication. An i.v. formulation has been evaluated in three species previously used in evaluation of both efficacy and toxicology of the oral formulation.

METHODOLOGY/PRINCIPAL FINDINGS

The pharmacokinetics of ST-246 after i.v. infusions in mice, rabbits and nonhuman primates (NHP) were compared to those obtained after oral administration. Ten minute i.v. infusions of ST-246 at doses of 3, 10, 30, and 75 mg/kg in mice produced peak plasma concentrations ranging from 16.9 to 238 µg/mL. Elimination appeared predominately first-order and exposure dose-proportional up to 30 mg/kg. Short i.v. infusions (5 to 15 minutes) in rabbits resulted in rapid distribution followed by slower elimination. Intravenous infusions in NHP were conducted at doses of 1 to 30 mg/kg. The length of single infusions in NHP ranged from 4 to 6 hours. The pharmacokinetics and tolerability for the two highest doses were evaluated when administered as two equivalent 4 hour infusions initiated 12 hours apart. Terminal elimination half-lives in all species for oral and i.v. infusions were similar. Dose-limiting central nervous system effects were identified in all three species and appeared related to high C(max) plasma concentrations. These effects were eliminated using slower i.v. infusions.

CONCLUSIONS/SIGNIFICANCE

Pharmacokinetic profiles after i.v. infusion compared to those observed after oral administration demonstrated the necessity of longer i.v. infusions to (1) mimic the plasma exposure observed after oral administration and (2) avoid C(max) associated toxicity. Shorter infusions at higher doses in NHP resulted in decreased clearance, suggesting saturated distribution or elimination. Elimination half-lives in all species were similar between oral and i.v. administration. The administration of ST-246 was well tolerated as a slow i.v. infusion.

Antiretroviral medications: adverse effects on the kidney

The widespread introduction of highly active antiretroviral therapy (HAART) in the mid-1990s dramatically altered the course of human immunodeficiency virus (HIV) infection, with improvements in survival and reductions in the incidence of AIDS-defining illnesses. Although antiretroviral therapy has been shown to reduce the incidence of both AIDS-defining and non-AIDS conditions, long-term exposure to HAART may also be associated with significant toxicity. This article reviews the potential nephrotoxicity of specific antiretroviral agents and the impact of antiretroviral therapy on related metabolic disorders. The antiretroviral agents most strongly associated with direct nephrotoxicity include the nucleotide reverse transcriptase inhibitor, tenofovir, and the protease inhibitor indinavir, although other agents have been implicated less frequently. Tenofovir and related nucleotide analogs have primarily been associated with proximal tubular dysfunction and acute kidney injury, whereas indinavir is known to cause nephrolithiasis, obstructive nephropathy, and interstitial nephritis. Kidney damage related to antiretroviral therapy is typically reversible with early recognition and timely discontinuation of the offending agent, and nephrologists should be familiar with the potential toxicity of these agents to avoid delays in diagnosis.

Intermediate dose cidofovir does not cause additive nephrotoxicity in BK virus allograft nephropathy

BKVAN has emerged as a major morbidity in kidney transplant recipients. Among treatment options is cidofovir, which can be nephrotoxic. We previously reported that intermediate dose cidofovir could be used without significant nephrotoxicity. We present extended results of the same treatment protocol in a larger cohort and with longer follow up. Diagnosis of BKVAN was based on detection of BK viral DNA from plasma and renal allograft biopsy tissue. All patients received cidofovir (0.25-1 mg/kg/dose) every 2-3 wk. Total number of cidofovir doses ranged from 1 to 18 (mean 8). This report includes eight patients, aged 5-21 yr, treated with intermediate dose cidofovir. Median follow-up was 11 months (range 4-32). Mean fall in reciprocal of serum creatinine (1/sCr) from baseline at BKVAN diagnosis was 64% (range 28-120%). A time-series plot of plasma BK virus PCR and 1/sCr showed marked reduction in viral loads without significant deterioration in 1/sCr from the initial value at BKVAN diagnosis. In this larger series with extended follow up, intermediate dose cidofovir without probenecid for the treatment of BKVAN continues to show stabilization of renal function without progression to renal failure.

[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).

Successful treatment of florid cutaneous warts with intravenous cidofovir in an 11-year-old girl

Cutaneous warts, commonly seen in children and the immunosuppressed are socially distressing and are often resistant to traditional treatments. Here, we report an 11-year-old girl with bilateral florid verrucous lesions on her hands, feet and chin, which were refractory to a number of standard treatments including cryotherapy, cantharidin preparations, topical salicylic acid, surgical debulking techniques, oral Cimetidine, and topical and intralesional Cidofovir. As the disfiguring lesions had a marked adverse effect on her quality of life, a trial of IV Cidofovir was instituted. We administered five cycles of IV Cidofovir with a 1-week interval between the first and second treatment, followed by 2-week intervals thereafter. This regime was well tolerated and we report dramatic resolution of the lesions with persistent clearance 6 months after completion of the fifth infusion. Resolution of recalcitrant warts with IV Cidofovir has been reported in a limited number of cases. Our experience supports its efficacy in this setting, and to the best of our knowledge this is the first report of successful treatment of cutaneous warts with IV Cidofovir in a pediatric case.

Antiviral Chemistry & Chemotherapy's Current Antiviral Agents FactFile (2nd Edition): DNA Viruses

Although most of the recent attempts to develop new antiviral agents have been focussed on RNA viruses (in particular, HIV and hepatitis C virus), a few new compounds are now awaiting their entry into the field of DNA viruses, particularly poxviruses, such as variola virus, because of the bioterrorist context, and herpesviruses, such as herpes simplex virus and cytomegalovirus, where the market scene has for many years been dominated by acyclovir, penciclovir and ganciclovir and their respective orally bioavailable prodrugs: valaciclovir, famciclovir and valganciclovir. Here, we review the current ‘state of the art’ with old compounds ready to rotate off and new compounds eagerly awaiting to appear on the continuously evolving scene of antiviral drug development.

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.

Intravenous cidofovir-induced resolution of disfiguring cutaneous human papillomavirus infection

Human papillomavirus infection is one of the most common and most distressing cutaneous diseases in patients with HIV infection. It is also a common, and often therapeutically challenging, infection in individuals who are immunologically competent. A wide range of therapeutic options exists for treating cutaneous human papillomavirus infections, but none is uniformly effective. In this report we describe a man with HIV-1 infection and disfiguring facial verruca vulgaris who demonstrated complete clinical response to intravenous cidofovir. Our report provides further support for the use of intravenous cidofovir as therapy for treatment-resistant and/or widespread cutaneous human papillomavirus infection.

Antiretroviral therapy and the kidney: balancing benefit and risk in patients with HIV infection

The widespread introduction of highly active antiretroviral therapy (HAART) has revolutionised the treatment and course of HIV infection, with complications of chronic HIV infection and HAART playing an increasingly important role in morbidity and mortality. Both HIV infection and HAART have been associated with the development of acute and chronic kidney disease. The incidence of HIV-associated nephropathy, the classic kidney disease of HIV, reached a plateau following the introduction of HAART, consistent with the pathogenic role of direct viral infection of the kidney. At the same time, antiretroviral agents and related therapies have demonstrated a range of nephrotoxic effects, including crystal-induced obstruction, lactic acidosis, tubular toxicity, interstitial nephritis and electrolyte abnormalities. This article reviews the impact of HAART on the epidemiology of HIV-related kidney disease, the potential nephrotoxicity of specific antiretroviral agents and related medications, and guidelines for monitoring kidney function in HAART-treated patients.

Intermediate-dose cidofovir without probenecid in the treatment of BK virus allograft nephropathy

BK virus allograft nephropathy (BKVAN) is a rising complication in kidney transplant recipients. Reducing immunosuppression has been the initial form of therapy in most cases, but is not always associated with improvement in graft function. Anti-viral therapy with low-dose cidofovir (0.25-0.42 mg/kg/dose) has been used successfully in some patients, but dose-related nephrotoxicity has limited its use. We present our experience with 3 kidney transplant recipients diagnosed with BKVAN who received intermediate-dose cidofovir (0.75-1.0 mg/kg/dose) without probenecid, and without concomitant nephrotoxicity. Three female patients, ages 8, 19 and 20 yr, presented with elevated serum creatinine (SCr) values, BK virus stain positive on renal biopsy and high plasma BK viral loads. As a result of viral loads being >2 million copies/ml in two patients and a lack of response to reduction in immunosuppression in the third, we initiated therapy with low-dose cidofovir. Because of persistent positive BK stain and positive plasma viral load, we then administered intermediate-dose cidofovir, without probenecid, for several subsequent doses (seven to 15 infusions till date). All patients tolerated the intermediate-dose cidofovir with no significant rise in SCr during the course of the infusions. The most recent SCr values in all three patients were improved from those at the initial diagnosis of BKVAN. All three patients showed a marked drop in BK viral loads when on intermediate-dose cidofovir, with complete clearing of viremia in two patients. In our experience, intermediate-dose cidofovir without probenecid, used judiciously, is not associated with additional nephrotoxicity and may provide an additional alternative for treatment.

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.

Antiviral Drug-Induced Nephrotoxicity

Drug-induced kidney injury is a major side effect in clinical practice, frequently leading to acute renal failure (ARF). It accounts for more than 2% to 15% of cases of ARF in patients admitted to the hospital or in the intensive care unit, respectively. The exact frequency of nephrotoxicity induced by antiviral drugs is difficult to determine. Antiviral drugs cause renal failure through a variety of mechanisms. Direct renal tubular toxicity has been described with a number of new medications with unique effects on epithelial cells of the kidney. These include cidofovir, adefovir dipivoxil, and tenofovir, as well as acyclovir. Additionally, crystal deposition in the kidney may promote the development of renal failure. Several different drugs have been described to induce crystal nephropathy, including acyclovir and the protease inhibitor indinavir. Renal injury associated with antiviral drugs involves diverse processes having effects on the renal transporters, as well as on tubule cells. In this article, we review the pathogenesis of antiviral drug-induced kidney injury, common nephrotoxic renal syndromes, and strategies for preventing kidney injury.

Drug-induced renal failure: a focus on tubulointerstitial disease

Therapeutic agents induce acute renal failure (ARF) by promoting various types of injury to the kidney. Acute interstitial nephritis (AIN) develops from medications that incite an allergic reaction, leading to interstitial inflammation and tubular damage. Acute tubular necrosis (ATN) is a dose-dependent process that develops from direct toxicity on tubular epithelia, typically in the absence of inflammation. Additional, less common patterns of drug-induced renal injury include osmotic nephropathy, crystal nephropathy, and acute nephrocalcinosis. This review focuses on the multitude of patterns of drug-induced renal failure due to tubulointerstitial disease.

Drug-Induced Renal Failure in the ICU

Drug-induced renal failure is a frequent complication in the setting of ICU. Generally spoken pathomechanisms leading to drug-induced renal failure can be divided into hemodynamic effects, epithelial toxicity or crystalline nephropathy. The risk of drug-induced renal failure is increased by any form of hypovolemia (i.e. true hypovolemia or reduced effective circulating volume), older age, pre-existent renal impairment, and concomitant application of two or more nephrotoxins. This article reviews drugs most frequently responsible for renal failure in the ICU and discusses preventive measures. (Int J Artif Organs 2004; 27: 1034-42)

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.

Clinical potential of the acyclic nucleoside phosphonates cidofovir, adefovir, and tenofovir in treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates HPMPC (cidofovir), PMEA (adefovir), and PMPA (tenofovir) have proved to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections: cidofovir against herpesvirus (herpes simplex virus types 1 and 2 varicella-zoster virus, cytomegalovirus [CMV], Epstein-Barr virus, and human herpesviruses 6, 7, and 8), polyomavirus, papillomavirus, adenovirus, and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus, and orf virus) infections; adefovir against herpesvirus, hepadnavirus (human hepatitis B virus), and retrovirus (human immunodeficiency virus types 1 [HIV-1] and 2 [HIV-2], simian immunodeficiency virus, and feline immunodeficiency virus) infections; and tenofovir against both hepadnavirus and retrovirus infections. Cidofovir (Vistide) has been officially approved for the treatment of CMV retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) has been approved for the treatment of HIV infections (i.e., AIDS), and adefovir dipivoxil (Hepsera) has been approved for the treatment of chronic hepatitis B. Nephrotoxicity is the dose-limiting side effect for cidofovir (Vistide) when used intravenously (5 mg/kg); no toxic side effects have been described for adefovir dipivoxil and tenofovir disoproxil fumarate, at the approved doses (Hepsera at 10 mg orally daily and Viread at 300 mg orally daily).

Cytomegalovirus Disease in the Highly Active Antiretroviral Therapy Era

Cytomegalovirus (CMV) is a major cause of morbidity and mortality in AIDS patients. Epidemiologic studies indicate that until 10 years ago, nearly one half of HIV-infected patients eventually developed CMV end-organ disease, including chorioretinitis, esophagitis, colitis, pneumonia, and central nervous system disease. Since the introduction of highly active antiretroviral therapy (HAART) this incidence has declined dramatically. Nonetheless, patients still present with CMV disease and resistance or intolerance to HAART does develop, which may give rise to a resurgence of CMV syndromes in AIDS patients. Until recently, only intravenous ganciclovir and foscarnet were available for management of CMV infection. With the advent of additional agents, clinicians now face the challenge of optimizing therapy for individual patients. This paper reviews the most common clinical syndromes caused by CMV, the treatment options, as well as an approach to diagnosing and treating antiviral resistance.

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.

Drug-induced renal failure: update on new medications and unique mechanisms of nephrotoxicity

Medications cause renal failure through a variety of mechanisms. Hemodynamic renal failure may result from drugs that reduce renal prostaglandins and hence renal blood flow and glomerular filtration rate. A relatively new group of drugs with this potential is the cyclooxygenase-2 selective inhibitors. Direct renal tubular toxicity has also been described with a number of new medications with unique effects on the epithelial cells of the kidney. These include the antiviral agents cidofovir, adefovir, and tenofovir as well as the bisphosphonate pamidronate. Additionally, crystal deposition in the kidney may promote the development of renal failure. Several different drugs have been described to induce crystal nephropathy, including the antiparasitic drug sulfadiazine, the antiviral agent acyclovir, and the protease inhibitor indinavir. Finally, an unusual form of renal failure characterized by swollen, vacuolated proximal tubular cells can develop from hyperosmolar substances. Agents recently described to induce an "osmotic nephrosis" include intravenous immunoglobulin and the plasma expander hydroxyethyl starch.

Pharmacokinetics and renal effects of cidofovir with a reduced dose of probenecid in HIV-infected patients with cytomegalovirus retinitis

To reduce possible nephrotoxicity, intravenous prehydration with normal saline and administration of probenecid must be used with each infusing of the antiviral cidofovir. The recommended standard-dose probenecid (SDP) regimen is 2 g at 3 hours before cidofovir, then 1 g at 2 and 8 hours after cidofovir (total 4 g). A new regimen of reduced-dose probenecid (RDP), 2 g at 1 hour before cidofovir without additional probenecid administrations after infusion (total 2 g), was compared with SDP using a randomized, open-label, parallel design. A single dose of cidofovir (5 mg/kg) was given as a 1-hour infusion after saline prehydration to 24 HIV-infected patients (11 males, 13 females) with cytomegalovirus retinitis and good renal function. Blood was sampled for 48 hours and urine for 24 hours after the start of the cidofovir infusion. Cidofovir pharmacokinetics did not differ significantly between groups. Average key pharmacokinetic parameters (Cmax, tmax, lambda z, AUC0-infinity, Vss, CL, CLR, fe, ER) for RDP differed by less than 17% from SDP and were consistent with previously reported SDP data. Renal function parameters, other safety endpoints, and adverse events were similar between the groups. Therefore, the reduced-dose regimen of probenecid provided renal protection after a single dose of cidofovir and did not alter the pharmacokinetics of cidofovir in patients with moderately good renal function. Although the overall pharmacokinetic results do not show a significant difference in cidofovir exposure with the new probenecid regimen, the main issue of safety of the new dose regimen, both relating to renal toxicity and probenecid-related adverse events, is not adequately addressed in a small study.

Rapid communication: acute renal failure associated with tenofovir: evidence of drug-induced nephrotoxicity

Drug-induced renal failure is a relatively common event in patients infected with HIV. This group of patients receives a number of potentially nephrotoxic medications for a variety of illnesses. The acyclic nucleoside phosphonates cidofovir and adefovir are antivirals that possess significant nephrotoxicity. Interestingly, tenofovir disoproxil fumurate (DF) is structurally similar to these 2 agents, yet seems to be less nephrotoxic based on a few published studies in HIV patients with intact renal function. We present a case in which acute renal failure developed after therapy with tenofovir DF in a patient with HIV and stable chronic kidney disease.

Intravenous Cidofovir therapy for disseminated adenovirus in a pediatric liver transplant recipient

BACKGROUND

No definitive antiviral therapy exists for adenovirus (ADV) in immunosuppressed hosts. Cidofovir (CDV), a broad spectrum anti-DNA viral agent, has previously been shown to be of therapeutic benefit in life-threatening adenoviral disease in bone marrow stem-cell recipients.

METHODS

A 71/2-month-old girl with a history of biliary atresia developed fevers, hematochezia, tachypnea, and laboratory evidence of hepatitis and pancreatitis 12 days after liver transplantation. A stool culture, oropharyngeal culture, blood viral culture, and blood polymerase chain reaction (PCR) confirmed ADV. Cidofovir 1 mg/kg intravenously three times per week was initiated. The patient received intravenous hydration and probenecid with the infusions to reduce the nephrotoxicity of CDV. Immunosuppression was reduced to achieve tacrolimus trough levels of approximately 8 ng/mL and prednisone at 0.1 mg/kg per day. Complete blood cell count, urinalysis, and viral studies were obtained weekly.

RESULTS

Detection of ADV DNA by PCR made a transition from positive to negative during CDV therapy. Blood viral cultures became negative after two CDV doses. Alanine aminotransferase normalized by 5 weeks of therapy. CDV was discontinued after 7 weeks secondary to transient acidosis and proteinuria. The patient never developed azotemia, neutropenia, or ocular abnormalities.

CONCLUSIONS

CDV was associated with improved clinical status, viral clearance, and minimal transient side effects in a pediatric liver transplant recipient with disseminated adenoviral disease. The current report documents clearance of disseminated ADV infection in a liver transplant recipient receiving CDV infusions.

Phase I dose escalation trial evaluating the pharmacokinetics, anti-human cytomegalovirus (HCMV) activity, and safety of 1263W94 in human immunodeficiency virus-infected men with asymptomatic HCMV shedding

1263W94 [maribavir; 5,6-dichloro-2-(isopropylamino)-1,beta-L-ribofuranosyl-1-H-benzimidazole] is a novel benzimidazole compound for treatment of human cytomegalovirus (HCMV) infection and disease, with potent in vitro activity against HCMV and good oral bioavailability. A phase I study was conducted to determine the pharmacokinetics (PK), anti-HCMV activity, and safety of 1263W94 administered as multiple oral doses to human immunodeficiency virus type 1-infected adult male subjects with asymptomatic HCMV shedding. Subjects received one of six dosage regimens (100, 200, or 400 mg three times a day, or 600, 900, or 1,200 mg twice a day) or a placebo for 28 days. 1263W94 demonstrated linear PK, with steady-state plasma 1263W94 profiles predictable based on single-dose data. 1263W94 was rapidly absorbed following oral dosing, and values for the maximum concentration of the drug in plasma and the area under the concentration-time curve increased in proportion to the dose. 1263W94 demonstrated in vivo anti-HCMV activity in semen at all of the dosage regimens tested, with mean reductions in semen HCMV titers of 2.9 to 3.7 log(10) PFU/ml among the four regimens evaluated for anti-HCMV activity. 1263W94 was generally well tolerated; taste disturbance was the most frequently reported adverse event over the 28-day dosing period.

CNS manifestations of cytomegalovirus infections: diagnosis and treatment

Cytomegalovirus (CMV) infection of the CNS occurs most commonly in patients with severe immunosuppression such as those with advanced HIV infection (i.e. AIDS) or those who have undergone bone marrow or solid organ transplantation. Immunocompetent patients are affected very rarely. The infection of the CNS may affect the brain (diffuse encephalitis, ventriculoencephalitis, cerebral mass lesions) or the spinal cord (transverse myelitis, polyradiculomyelitis). Diagnosis is very difficult and should be based on clinical presentation, results of imaging and virological markers. The most specific diagnostic tool is the detection of CMV DNA by polymerase chain reaction in the CSF. Treatment should be initiated promptly if CMV infection is suspected. Antiviral therapy consists of intravenous ganciclovir, intravenous foscarnet or a combination of both. Cidofovir is the treatment of second choice. Patients who experience clinical improvement or stabilisation during induction therapy should be given maintenance therapy. After immune reconstitution (in HIV-positive patients) or discontinuation of immunosuppressive therapy (in transplant recipients), maintenance therapy may be stopped. Despite therapy, the prognosis for long-term survival is very poor, especially in patients with AIDS.

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.

Cytomegalovirus infection: the point in 2001

The incidence of cytomegalovirus (CMV) disease, one of the most prevalent opportunistic infections in HIV-infected persons in the early 1990s, has decreased by more than 80% since the introduction of highly active antiretroviral therapy (HAART). The rare cases of CMV disease still observed in Western countries occur mainly in profoundly immunosuppressed patients who have failed to respond to HAART. A new finding is the occasional occurrence of inflammatory retinitis in some patients on HAART with a history of healed retinitis. New tools for CMV detection have become available recently, including use of polymerase chain reaction (PCR) to detect CMV DNA from plasma. It has been possible to redefine, in the HAART period, patients at risk for CMV disease as those who have a low CD4 cell count as well as a blood marker of CMV blood dissemination (plasma CMV DNAaemia or high pp65 antigenaemia). Besides the classical therapeutic approach using ganciclovir (GCV), foscarnet and cidofovir, development of valganciclovir (VGCV), an orally administered prodrug of GCV, appears promising. There is evidence to suggest that it is as effective as intravenous GCV for the treatment of CMV retinitis, and it is currently being studied as a pre-emptive therapy in patients at high risk for CMV disease. Finally, patients with inactive CMV retinitis receiving HAART and with stable immune reconstitution may be able to discontinue maintenance therapy provided a regular ophthalmological and virological surveillance is maintained.

Oral valganciclovir: a new option for treatment of cytomegalovirus infection and disease in immunocompromised hosts

Immunocompromised hosts are at increased risk of cytomegalovirus (CMV) infection and serious CMV disease. CMV infection is an important cause of morbidity among patients infected with HIV and after solid organ transplantation (SOT) and may cause life-threatening disease in allogeneic stem cell transplant (SCT) recipients. The introduction into clinical use of potent antiviral compounds and of rapid detection assays for CMV during the past two decades has allowed development of strategies for the prevention and treatment of disease caused by CMV in these groups of immunocompromised patients. At present, the antiviral drugs ganciclovir, foscarnet and cidofovir are commonly used in the treatment of CMV infection and disease. However, these agents have a poor oral bioavailability and, for systemic use, require iv. administration for most indications. Valganciclovir is an oral prodrug of ganciclovir, with a 10-fold greater bioavailability than oral ganciclovir. Studies of the pharmacokinetics of valganciclovir among HIV-infected CMV-seropositive patients and liver transplant recipients suggest that this oral compound has the potential to replace both oral and iv. ganciclovir in many situations if it is shown to be as efficacious and safe as those ganciclovir formulations in immunodeficient patients. In the first part of this review, currently established approaches to the management of CMV infection and disease in SCT and SOT recipients and HIV-infected patients are discussed to highlight possible indications for future valganciclovir use; in the second part, data from human studies of valganciclovir are presented.

Cytomegalovirus treatment options in immunocompromised patients

Cytomegalovirus (CMV) infection was recognised in congenitally infected infants in the first half of the 20th century. Following the increased use of immunosuppressive regimens for bone marrow and solid organ transplantation, various manifestations of CMV disease were recognised. Milder symptoms included fever, anorexia and malaise but severe symptoms included pneumonitis, hepatitis, gastrointestinal ulceration, choreoretinitis and encephalopathy, all with a high morbidity or mortality. With the onset of the AIDS epidemic, manifestations of CMV became evident, predominantly retinitis. Ganciclovir used intravenously has been the principal anti-CMV agent investigated. However, ganciclovir has problems with suboptimal efficacy, toxicity, poor oral bioavailability and evolution of resistant strains. Additional studies have been performed on foscarnet and cidofovir, although the use of both have been limited by their nephrotoxicity. Combination therapy with ganciclovir and foscarnet for resistant strains has been used. There are promising newer drugs like the methylenecyclopropane nucleoside analogues and benzimidazole. The most novel compound is the antisense oligonucleotide fomivirsen that has been evaluated principally in CMV retinitis. The role of immunotherapy with either immunoglobulin prophylaxis or the novel adoptive immunotherapy needs further evaluation.

Prophylaxis against herpesvirus infections in transplant recipients

Herpesvirus infections are important after stem cell and organ transplant. During the last decades several antiviral agents have been introduced with efficacy against herpesviruses. These agents are the nucleoside analogues aciclovir, valaciclovir, famciclovir, and ganciclovir; the nucleotide analogue cidofovir; and the pyrophosphate analogue foscarnet. Several studies have been performed with antiviral agents with the aim to reduce morbidity and mortality associated with herpesvirus infections in transplant recipients. Aciclovir and valaciclovir have been examined in randomised, controlled trials in both solid organ and stem cell transplant patients, and were shown to be very effective for the prevention of herpes simplex virus (HSV) and varicella-zoster virus infections. In addition, these drugs were shown to reduce cytomegalovirus (CMV) infection and improve survival in allogenic stem cell transplant patients and to reduce CMV infection, CMV disease (aciclovir and valaciclovir), and acute rejection (valaciclovir) in renal transplant patients. Ganciclovir is very effective for the prevention of CMV infection and disease in both stem cell and solid organ transplant recipients. It can also be used in preemptive strategies in which the aim is to prevent CMV disease in patients who have ongoing CMV infection documented by antigenaemia or detection of CMV DNA. The latter strategy has the advantage of reducing the exposure to the drug and thereby the risk for toxicity. Foscarnet has also been shown to be effective as preemptive therapy for CMV in allogenic stem cell transplant patients and as therapy for aciclovir-resistant HSV infections. Finally cidofovir is an interesting agent with broad spectrum antiherpesvirus efficacy. However, because of the drug's toxicity profile, further studies are needed.