In vivo additive antiretroviral effect of combined zidovudine and foscarnet therapy for human immunodeficiency virus infection (ACTG Protocol 053)

Selective excision of chain-terminating nucleotides by HIV-1 reverse transcriptase with phosphonoformate as substrate

A major mechanism for human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) resistance to nucleoside analogs involves the phosphorolytical removal of the chain-terminating nucleotide from the 3'-end of the primer. In this work, we analyzed the effect of phosphonoformate (PFA) and other pyrophosphate (PP(i)) analogs on PP(i)- and ATP-dependent phosphorolysis catalyzed by HIV-1 RT. Our experimental data demonstrated that PFA did not behave as a linear inhibitor but as an alternative substrate, allowing RT to remove AZT from a terminated primer through a PFA-dependent mechanism. Interestingly, in non-terminated primers, PFA was not a substrate for this reaction and competitively inhibited PP(i)- and ATP-dependent phosphorolysis. In fact, binding of PFA to the RT.template/primer complex was hindered by the presence of a chain terminator at the 3'-end of the primer. Other pyrophosphate analogs, such as phosphonoacetate, were substrates for the excision reaction with both terminated and nonterminated primers, whereas pamidronate, a bisphosphonate that prevents bone resorption, was not a substrate for these reactions and competitively inhibited the phosphorolytic activity of RT. As expected from their mechanisms of action, pamidronate (but not PFA) synergistically inhibits HIV-1 RT in combination with AZT-triphosphate in the presence of PP(i) or ATP. These results provide new clues about the mechanism of action of PFA and demonstrate that only certain pyrophosphate analogs can enhance the effect of nucleosidic inhibitors by blocking the excision of chain-terminating nucleotides catalyzed by HIV-1 RT. The relevance of these findings in combined chemotherapy is discussed.

Inhibition of murine AIDS by a new azidothymidine homodinucleotide

A new antiretroviral drug (azidothymidine homodinucleotide, AZTp2AZT), designed for the protection of macrophages against retroviral infection, was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS) alone and in combination with oral azidothymidine (AZT). C57BL/6 mice were infected with the retroviral complex LP-BM5 and treated for 3 months by weekly administrations of 15 nmol of AZTp2AZT encapsulated into autologous erythrocytes for macrophage protection. AZTp2AZT treatment was found to reduce lymphoadenopathy (48%), splenomegaly (26%), and BM5d proviral DNA content in lymph nodes, spleen, and brain of 37%, 40%, and 36%, respectively, compared with untreated animals. AZT administration in drinking water (0.25 mg/ml) was more effective than administration of AZTp2AZT encapsulated into erythrocytes in reducing lymphoadenopathy, splenomegaly, gammaglobulinemia, and proviral DNA content in lymph nodes, but it caused a reduction in erythrocyte count and hematocrit levels. Although combined treatments do not provide additive responses in the several parameters investigated, they were found to be much more effective in reducing the proviral DNA content in brain (67%) than were monotherapies. Furthermore, no apparent signs of hematotoxicity were observed. Thus, macrophage delivery of antiviral drugs may contribute to brain protection from retroviral infections by mechanisms other than those exerted by oral AZT administration.

Antiretroviral effect of combined zidovudine and reduced glutathione therapy in murine AIDS

A combination of antiretroviral drugs acting at different points in the virus replication cycle was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). Intramuscular administration of high doses of reduced glutathione (GSH, 100 mg/mouse/day) and AZT (0.25 mg/ml in drinking water) was found to reduce lymphoadenopathy (92%), splenomegaly (80%), and hypergammaglobulinemia (90%) significantly more than AZT alone. Combined treatment resulted in a reduction in proviral DNA content of 69, 66, and 60%, respectively, in lymph nodes, spleen, and bone marrow. Furthermore, the stimulation index of B cells was also significantly higher in animals receiving GSH and AZT whereas additional responses were not observed in the T cell stimulation index and blood lymphocyte phenotype analyses. In conclusion, the administration of high doses of GSH and AZT, a new combination of antiviral drugs, seems to provide additional advantages compared to single-agent therapy.

Clonal selection of HIV type 1 variants associated with resistance to foscarnet in vitro: confirmation by molecular evolutionary analysis

Foscarnet (trisodium phosphonoformate, PFA) is an effective inhibitor of retroviral reverse transcriptase (RT) and is known to block the replication of human immunodeficiency virus type 1 (HIV-1). In this article we analyzed the evolutionary process in generating HIV-1 strains related to drug resistance, using PFA as a selective pressure. PFA inhibited virus replication and protected the virus-induced cell killing, but it did not completely eliminate HIV-1 during the course of 7 weeks of treatment. The nucleotide sequence of the 859-bp DNA fragment spanning the core region of the HIV-1 pol gene was determined for 51 clones obtained from genomic DNA of the HIV-1-infected cells at different time points during PFA treatment. The nucleotide sequence analysis documented the presence of a minor HIV-1 variant prior to the PFA treatment. Molecular evolutionary techniques were utilized to analyze how the minor HIV-1 clones became predominant during this evolutionary process under the selective pressure of PFA. A phylogenetic tree analysis divided these 51 HIV-1 clones into 3 groups. One of the groups consisted of the clones associated with the resistance to PFA. The clones belonging to this group became predominant over time during the course of PFA treatment. Thus, the acquisition of PFA resistance by HIV-1 was considered to be due to clonal selection. Furthermore, among the various amino acid substitutions observed, the substitution of arginine at position 172 by lysine (Arg172Lys) clearly distinguished this group from the others. Since the consistent amino acid substitution observed here has not been identified in the HIV-1 strains resistant to other RT inhibitors, PFA in combination with other RT inhibitors is considered to be a feasible candidate for a convergent combined chemotherapy against HIV-1 in the treatment of patients with AIDS and related conditions.

Predictors of cytomegalovirus disease, natural history and autopsy findings in a cohort of patients with AIDS

OBJECTIVE

To identify the predictors of acquiring cytomegalovirus (CMV) disease, and to describe natural history, therapeutic management and autopsy findings in affected patients.

DESIGN

Observational study of a consecutive cohort of AIDS patient diagnosed and followed in the same institution.

METHODS

All of the patients with CMV were included. Statistical analyses were performed to establish the risk of acquiring the disease at or after AIDS presentation, survival, and the occurrence and time of relapses in relation to maintenance therapy. The presence of CMV infection at autopsy was also investigated.

RESULTS

CMV disease was diagnosed in 304 (24.8%) out of 1,227 patients, its incidence increasing according to the year of AIDS diagnosis. Women, homosexual men, patients given zidovudine and Pneumocystis carinii pneumonia (PCP) prophylaxis before AIDS, and severely immunodepressed patients were at higher risk for the disease. CMV disease was an independent factor of worse survival (hazard ratio, 1.7 versus PCP; 95% confidence intervals, 1.28-2.13). Patients untreated during the acute phase had a 4.3 higher risk of dying than those treated. Relapses occurred less frequently and later in patients given continuous maintenance treatment (23 out of 113; 17 months) than in untreated patients (13 out of 16; 3 months) or those given discontinuous therapy (22 out of 40; 7 months), whereas survival was independent from treatment. CMV infection was found in 97 out of 134 patients at autopsy, but was unassociated with relapse.

CONCLUSIONS

CMV is a severe disease whose frequency is higher in severely immunodepressed patients. Continuous treatment leads to a lower relapse rate even if it does not change survival or eradicate the infection.

Antiviral efficacy and toxicity of ribavirin and foscarnet each given alone or in combination in the murine AIDS model

The antiviral efficacy and toxicity of ribavirin, foscarnet (PFA), and combinations of both drugs at two different doses have been evaluated in the murine AIDS (MAIDS) model. Our results clearly demonstrated that infected mice treated with ribavirin at 100 mg/ kg/day were protected against splenomegaly, lymphadenopathy, and hypergammaglobulinemia whereas PFA alone at 180 or 360 mg/kg/day did not afford any protection. Treatment with drug combinations showed protective effects similar to those observed with ribavirin alone. Hyperplasia and deorganization of the lymphoid architecture were noted in spleen and lymph nodes of infected mice compared to those of the uninfected group. However, treatment with ribavirin restored the lymphoid tissue architecture and reduced the emergence of germinal centers. Electron microscopic examination of renal cortex of animals treated with PFA at 360 mg/kg/day revealed clear mitochondrial necrosis (bursting of mitochondria) of the distal tubules and vacuolization of the proximal tubules which was more striking with combination therapy. Regarding hematotoxicity, PFA did not cause significant hematotoxicity at both doses, whereas ribavirin was hematotoxic at both doses (50 and 100 mg/kg/day), this toxicity being more evident at the higher dose. In conclusion, treatment with ribavirin showed clear efficacy against MAIDS whereas PFA had no efficacy. Furthermore, ribavirin treatment caused hematoxicity and PFA treatment resulted in nephrotoxicity.

Inhibition of murine AIDS by combination of AZT and dideoxycytidine 5'-triphosphate

SUMMARY

A combination of antiretroviral drugs acting on different cell types (lymphocytes and macrophages) was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). In a first experiment, C57BL/6 mice were infected with a single i.p. administration of LP-BM5 and treated with 0.125 or 0.25 mg/ml AZT in drinking water for 3 months. AZT treatment was found to reduce lymphadenopathy (60 and 65 percent, respectively), splenomegaly (37 and 50 percent, respectively), and hypergammaglobulinemia (6 and 50 percent, respectively). Furthermore, at the highest AZT concentration, BM5d proviral DNA content in lymph nodes and in the spleen showed a reduction of 78 and 70 percent, respectively, compared to untreated animals. In a second experiment, infected mice were treated with AZT (0.25 mg/ml in drinking water) and with 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) encapsulated into autologous erythrocytes for macrophage protection. Combined treatments resulted in a further reduction of lymphadenopathy (a further 33 percent with respect to the single treatment of AZT) and splenomegaly (a further 28 percent respect to the single treatment of AZT) but not of gammaglobulinemia. Proviral DNA in lymph nodes and spleen showed a reduction of 82 and 77 percent, respectively, compared to infected mice. Stimulation index of T cells was also significantly increased in animals receiving both treatments versus AZT only. In conclusion, the selective administration of antiviral drugs that preferentially protect different cell types seems to provide additional advantages compared to single-agent therapy.

Foscarnet alters antidiuretic hormone-mediated transport

Therapy with foscarnet is associated with acute renal failure. Prior studies have emphasized foscarnet's proximal tubular toxicity, but there have been isolated reports of foscarnet-induced nephrogenic diabetes insipidus. As a phosphate analog, foscarnet is a competitive inhibitor of NaPO4 cotransport. However, foscarnet's effect on antidiuretic hormone (ADH)-induced transport has not been previously investigated. We studied foscarnet's modulation of transport in the toad urinary bladder. Foscarnet at 10 microM to 10 mM did not alter basal water or urea flux. Urea transport induced by a maximal dose of ADH (24 mIU/ml) was inhibited by 0.1 to 5.0 mM foscarnet. In tissues challenged with 0.5 to 1.0 mIU of ADH per ml, 1.0 to 10 mM foscarnet increased water flow but did not alter urea flux. Foscarnet also increased water flow induced by 1.0 to 10 microM forskolin. In tissues pretreated with 10 microM naproxen, foscarnet did not alter water flow induced by 0.5 to 1.0 mIU of ADH per ml or forskolin. These results indicate that foscarnet stimulates water flow induced by 0.5 to 1.0 mIU of ADH per ml at a site proximal to that of the generation of cyclic AMP and inhibits urea flux induced by a maximal dose of ADH at a separate site. In humans, foscarnet nephrotoxicity is likely not limited to the proximal nephron, but extends to the collecting duct. Patients receiving foscarnet should be closely monitored for disorders of urinary concentration.

Cytomegalovirus esophagitis in AIDS: a prospective evaluation of clinical response to ganciclovir therapy, relapse rate, and long-term outcome

PURPOSE

Although cytomegalovirus (CMV) esophagitis is an important complication of acquired immunodeficiency syndrome, there has been little study specifically addressing the response to currently available antiviral therapy, relapse rate without maintenance therapy, and long-term outcome.

PATIENTS AND METHODS

Over a 45-month period, 44 patients with CMV esophagitis established endoscopically and histopathologically were prospectively identified from among all human immunodeficiency virus (HIV)-infected patients undergoing endoscopy. Induction therapy consisted of intravenous ganciclovir at 10 mg/kg per day for approximately 14 days. Foscarnet was given at 60 mg/kg every 8 hours for nonresponders to ganciclovir.

RESULTS

Of these patients, 35 completed induction ganciclovir therapy, resulting in a complete response in 17 (49%) and a partial response in 10 (29%), yielding a 77% overall response rate. Seven of 8 nonresponders were subsequently treated with foscarnet, with a clinical response seen in 5 patients. In the 18 eventual complete responders to ganciclovir or foscarnet followed up without maintenance therapy, 7 (39%) relapsed at a median of 4 months (range 2 to 18 months). In all cases, relapse was manifested by recurrent odynophagia. Reinduction ganciclovir therapy yielded a complete response in 1 patient and a partial response in 2, and induction foscarnet treatment resulted in a complete response in the other treated patients. During long-term follow-up, 1 complete responder developed CMV colitis with concurrent retinitis, and 4 other patients developed retinitis. The median survival after diagnosis was 8.2 months, although survival for greater than 1 year was seen in 4 patients. No patient died as a direct result of esophageal disease, although ulcer-related bleeding may have contributed to death in 2 patients with end-stage liver diseases and hepatic encephalopathy.

CONCLUSIONS

CMV esophagitis has a favorable response to induction ganciclovir therapy, and a long-term remission may occur after induction therapy alone. Despite the favorable response to ganciclovir therapy, the long-term survival is poor, reflecting the severe immunodeficiency of these patients.

Foscarnet. A reappraisal of its antiviral activity, pharmacokinetic properties and therapeutic use in immunocompromised patients with viral infections

The DNA polymerase of human herpes viruses, including cytomegalovirus (CMV), and the reverse transcriptase of human immunodeficiency virus (HIV) are selectively inhibited in vitro by the pyrophosphate analogue foscarnet. Inhibition is reversible on withdrawal of foscarnet and additive or synergistic effects have been demonstrated in vitro with other antiviral drugs, including ganciclovir and zidovudine. Foscarnet appears to have negligible effects on host enzymes and cells. Complete or partial clinical resolution of ocular symptoms is obtained in more than 89% of patients with acquired immunodeficiency syndrome (AIDS) and CMV retinitis during foscarnet induction therapy, but relapse occurs soon after ceasing treatment. Maintenance treatment given daily can extend the period of remission considerably. Foscarnet and ganciclovir monotherapy had similar efficacy in the treatment of CMV retinitis in patients with AIDS in several studies, and have been used concomitantly in immunocompromised patients with recalcitrant CMV infections. In 1 trial, patients receiving foscarnet survived for significantly longer than those receiving ganciclovir. Foscarnet has been used successfully in the treatment of limited numbers of immunocompromised patients with CMV-associated gastrointestinal (improvement in over 67% of patients) and other infections. Aciclovir-resistant herpes simplex infections in immunocompromised patients have also been treated successfully with foscarnet. Almost 90% of a foscarnet dose is excreted in the urine. Reversible nephrotoxicity is common during foscarnet therapy, but may be reduced by dosage adjustment and adequate hydration. Anaemia, nausea and vomiting, disturbances in electrolyte levels and genital ulceration have also been associated with administration of the drug. The different tolerability profiles of foscarnet and zidovudine facilitate the use of these agents in combination in patients with AIDS and CMV infection; whereas ganciclovir, like zidovudine, is associated with dose-limiting haematological toxicity. The apparent survival benefits seen in these patients when receiving foscarnet and zidovudine (possibly linked to synergy between zidovudine and foscarnet and/or the inherent anti-HIV activity of foscarnet), appear to offer potentially important advantages for foscarnet over ganciclovir in the treatment of selected patients with AIDS and CMV infections.

Current management of cytomegalovirus disease in patients with AIDS

Cytomegalovirus (CMV) infection is common in both homosexual and heterosexual HIV-infected patients, and causes disease in a substantial proportion of patients with AIDS and very low CD4+ cell counts. Both ganciclovir, an analog of the nucleoside guanosine, and foscarnet, an analog of pyrophosphate, are licensed for treatment of CMV retinitis. They may also have a role in the treatment of gastrointestinal disease caused by CMV. In the Studies of Ocular Complications of AIDS comparative trial the two agents were equally effective against CMV retinitis, but patients receiving foscarnet had significantly longer survival, even after adjusting for covariates including antiretroviral therapy. Ongoing studies are evaluating higher dosages of foscarnet for maintenance therapy and combined therapy with ganciclovir and foscarnet. Tolerance of ganciclovir therapy has been facilitated by adjunctive therapy with colony-stimulating factors. Because both ganciclovir and foscarnet must be administered by intravenous infusion and are associated with significant toxicities, other anti-CMV agents are under active development, including HPMPC and an oral formulation of ganciclovir. Management of CMV retinitis involves individualizing therapy, balancing side effects and administration requirements, and, in many clinical settings, the overall cost of treatment.

Alternating versus continuous drug regimens in combination chemotherapy of human immunodeficiency virus type 1 infection in vitro

We compared the in vitro efficacies of two-, three-, and four-drug combinations given continuously or in alternating regimens against a clinical isolate of human immunodeficiency virus type 1. In H9 cells and peripheral blood mononuclear cells, at the drug concentrations used in this study, there was greater suppression of human immunodeficiency virus type 1 infection as the number of drugs in the regimen was increased from one to four simultaneously administered agents. Although alternating drug regimens were effective, they were not better than continuous administration of either single drugs or combinations of agents and were less effective than giving all drugs of an alternating regimen simultaneously.

Long-term foscarnet therapy not associated with the development of foscarnet-resistant human immunodeficiency virus type 1 in an acquired immunodeficiency syndrome patient

Sequential human-immunodeficiency virus type 1 (HIV-1) isolates from an acquired immunodeficiency syndrome (AIDS) patient on long-term foscarnet and zidovudine therapy were examined for the emergence of foscarnet resistance. One isolate obtained before therapy, and three post-foscarnet therapy HIV isolates had similar foscarnet sensitivity profiles, despite the emergence of foscarnet-resistant herpes simplex virus type 2 (HSV-2) during the period of therapy. Virion reverse transcriptases from these isolates were also equally inhibited by foscarnet. In contrast, sequential HIV isolates taken pre- and postzidovudine therapy showed a gradual increase in IC50 to this drug. In this patient, long-term foscarnet and zidovudine therapy selected foscarnet-resistant HSV and zidovudine-resistant HIV; in contrast, HIV remained susceptible to foscarnet. Concurrent administration of other anti-HIV drugs (zidovudine and interferon-alpha) may have hindered the development of foscarnet resistant HIV-1 in vivo.

Safety of alternating ganciclovir and foscarnet maintenance therapy in human immunodeficiency virus (HIV)-related cytomegalovirus infections. An open-labeled pilot study

In the treatment of cytomegalovirus (CMV) disease in patients with AIDS, a life-long suppression therapy following an induction therapy consisting of ganciclovir or foscarnet is essential. Due to drug-related toxicities, anti-CMV therapy frequently has to be discontinued. To determine whether toxicities and side effects may be reduced with an alternating combination therapy consisting of ganciclovir and foscarnet (ganciclovir: 5 mg/kg every other day; foscarnet: 120 mg/kg every other day), 10 AIDS patients with CMV disease received this maintenance therapy for a median time of 18.5 weeks (5-51 weeks). Side effects were reported from 5 patients (nausea 5, malaise/fatigue 2, penile ulcers 1). Hematological or renal toxicities were mild, 1-week discontinuation of therapy due to neutropenia was necessary in 1 patient. Progression of CMV disease was observed in 3 patients at 2, 6, and 30 weeks of maintenance therapy. Median relapse-free interval for all patients was 105 days. We conclude that combination therapy with ganciclovir and foscarnet can be used safely for induction and maintenance therapy. Therefore, this regimen should be assessed in further trials to evaluate safety, efficacy, and the development of resistance in comparison to ganciclovir or foscarnet monotherapy.

Penetration of foscarnet into cerebrospinal fluid of AIDS patients

The diffusion of foscarnet into cerebrospinal fluid (CSF) was studied in 27 patients with AIDS. Foscarnet was administered intravenously at various dosages at 12-h intervals. Concentrations in plasma and CSF at the end of foscarnet infusion or 1, 3, 5, 6, and 12 h after infusion were determined by high-performance liquid chromatography. Thirty-seven samples were obtained. The median concentration of foscarnet in CSF was 80 mumol/liter (range, 0 to 500 mumol/liter). The CSF foscarnet concentration was greater than the 50% inhibitory concentration for human immunodeficiency virus type 1 and was equal to or greater than the 50% inhibitory concentration for cytomegalovirus in most cases. The penetration of foscarnet into CSF, as expressed by the ratio of the concentration in CSF to the simultaneous concentration in plasma, ranged from 0 to 3.4 (median, 0.27) and was highly correlated with the presence of cells within CSF and the length of foscarnet therapy. Good diffusion of foscarnet in CSF allows evaluation of this drug in central nervous system cytomegalovirus and human immunodeficiency virus infections in patients with AIDS.

Antiviral therapy in human immunodeficiency virus infections. Current status (Part II)

Part I of this article reviewed the targets against which anti-HIV drugs can be directed, problems in assessing active compounds (e.g. resistance development and use of surrogate end-points). and nucleoside analogues effective against HIV reverse transcriptase. Intensive research is currently being undertaken in laboratories and hospitals to design and evaluate new inhibitors of HIV. In this work, combining different drugs is one important approach, both to decrease toxicity and to offset the rate of resistance development, which seems to be a major problem associated with therapy directed against the ever-changing HIV. Therapeutic vaccines and immunomodulators are other modalities being actively evaluated against HIV and AIDS, although this effort has not yet yielded any licensed treatment. It appears likely that new antiviral drugs and immunotherapies will be forthcoming during the next 5 years, that they will be used in a variety of combinations, and that the treatment options available for opportunistic infections will increase. These developments should improve the survival and the quality of life of patients with HIV infection.

Foscarnet penetrates the blood-brain barrier: rationale for therapy of cytomegalovirus encephalitis

Foscarnet (phosphonoformate) is a potent virustatic drug against herpes-like viruses and is widely used in the therapy of cytomegalovirus infections in immunosuppressed patients. To obtain data on its penetration across the blood-brain barrier, we determined concentrations of foscarnet in cerebrospinal fluid and in plasma specimens from 26 patients with human immunodeficiency virus (stages 2 to 6 by Walter Reed Army Institute of Research classification) after a single infusion of 90 mg of foscarnet per kg of body weight and at steady state by electrochemical detection by high-pressure liquid chromatography. Penetration coefficients were correlated with the integrity of the blood-brain barrier. After a single infusion of foscarnet, levels in plasma ranged from 297 to 1,775 micrograms/ml (990 to 5,920 mumol/liter), with a mean of 766 +/- 400 micrograms/ml. Corresponding levels in cerebrospinal fluid were 57 to 225 micrograms/ml (190 to 750 mumol/liter), with a mean of 131 +/- 52 micrograms/ml. The penetration coefficient was 0.05 to 0.72 (mean, 0.23 +/- 0.16). At steady state, mean foscarnet levels in plasma were 464 +/- 219 micrograms/ml (1,553 mumol/liter) and mean levels in cerebrospinal fluid were 308 +/- 155 micrograms/ml (1,023 mumol/liter). The penetration coefficient was 0.66 +/- 0.11. Although penetration coefficients were highly variable after a single administration and at steady state, the concentrations of foscarnet attained in cerebrospinal fluid are sufficient for complete inhibition of cytomegalovirus replication in vitro. In conclusion, we show that foscarnet seems to be the drug of choice for the treatment of cytomegalovirus encephalitis, because it penetrates the blood-brain barrier and is found in the cerebrospinal fluid in virustatic concentrations. Foscarnet might be considered for additive therapy for human immunodeficiency virus encephalitis in combination with zidovudine or dideoxyinosine.

Ocular complications of the acquired immunodeficiency syndrome. Focus on the treatment of cytomegalovirus retinitis with ganciclovir and foscarnet

The most common ocular complication in patients with the acquired immunodeficiency syndrome (AIDS) is cytomegalovirus retinitis. Incidence figures vary from 20 to 76%. Patients with cytomegalovirus may suffer from mild visual impairment of one or both eyes, but as the disease progresses the retinitis will almost certainly lead to blindness. Although cytomegalovirus retinitis is not a life-threatening infection, it can largely diminish the patient's quality of life. Clinical trials for the treatment of cytomegalovirus retinitis with a number of antiviral drugs have resulted in two drugs of choice, ganciclovir and foscarnet. Both drugs have an initial efficacy with induction therapy of 80-90%, but maintenance therapy is always needed to prevent a relapse. To exclude systemic side-effects of ganciclovir, intravitreal administration has been investigated with good results. Combination therapy of foscarnet and ganciclovir may be worthwhile in resistant cytomegalovirus retinitis.

Increased survival of a cohort of patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis who received sodium phosphonoformate (foscarnet)

PURPOSE

To evaluate the impact of foscarnet on the longevity of persons with human immunodeficiency virus, type 1 (HIV-1) infection and cytomegalovirus (CMV) retinitis.

PATIENTS AND METHODS

A cohort of 24 patients with acquired immunodeficiency syndrome (AIDS) and CMV retinitis received sodium phosphonoformate (foscarnet) as part of a controlled efficacy trial at the National Institutes of Health. Foscarnet was continued for as long as it was tolerated. Antiretroviral therapy was given to the patients as tolerated. Long-term follow-up was available on all patients.

RESULTS

Seventeen patients received zidovudine during or after receiving foscarnet, 2 patients received dideoxyinosine, 2 patients zidovudine and dideoxyinosine, and 3 patients received no specific antiretroviral agent. Patients received foscarnet for a mean of 6.2 months (median, 4 months; range, 10 days to 22 months). Ten patients required a change to ganciclovir therapy at some time after receiving foscarnet. The median time from the diagnosis of CMV retinitis until death was 13.5 months (range, 3 to 34 months). Patients lived longer than untreated or ganciclovir-treated historical controls with AIDS and CMV retinitis. There was no difference in the survival of patients treated with foscarnet at the time of diagnosis and those patients treated with foscarnet only after progression of their CMV retinitis.

CONCLUSIONS

These data suggest that foscarnet may prolong the survival of persons with AIDS and CMV retinitis and should be the initial treatment of choice in these patients.

Pharmacokinetics of concomitantly administered foscarnet and zidovudine for treatment of human immunodeficiency virus infection (AIDS Clinical Trials Group protocol 053)

Foscarnet and zidovudine (ZDV) pharmacokinetic parameters were not altered in five patients receiving 14 days of concomitant therapy. Foscarnet clearance in plasma averaged (+/- standard deviation) 0.16 +/- 0.03 and 0.13 +/- 0.05 liter/h/kg of body weight in the absence and presence of ZDV. ZDV parameters were also not significantly altered, with a mean (+/- standard deviation) oral clearance of 2.7 +/- 1.0 and 2.6 +/- 0.8 liter/h/kg for the 2 study days, respectively.

Systemic antiviral drugs used in ophthalmology

Over the past two decades, the recognition of viral enzymes and proteins that can serve as molecular targets of drugs has revolutionized the treatment of viral infections. Beginning with acyclovir, a number of systemically administered agents which are both relatively safe and effective for the treatment of herpetic infections and human immunodeficiency virus (HIV) infections have become widely available. Because of increased numbers of herpes virus infections, as well as the rising epidemic of HIV infections, the ophthalmologist is, more likely than ever before to be involved in the treatment of severe and frequent ocular infections caused by herpes viruses. In addition, the acute retinal necrosis (ARN) syndrome has been demonstrated to be caused by herpes viruses and a once rare retinal infection caused by cytomegalovirus is common in patients with the acquired immunodeficiency syndrome (AIDS). In this article, four systemic antiviral drugs (Vidarabine, Acyclovir, Ganciclovir, and Foscarnet) that have demonstrated usefulness in the treatment of ophthalmic disease are reviewed in detail with regard to their mechanisms, applications, effectiveness, and side effects.

Antiviral therapy: current concepts and practices

Drugs capable of inhibiting viruses in vitro were described in the 1950s, but real progress was not made until the 1970s, when agents capable of inhibiting virus-specific enzymes were first identified. The last decade has seen rapid progress in both our understanding of antiviral therapy and the number of antiviral agents on the market. Amantadine and ribavirin are available for treatment of viral respiratory infections. Vidarabine, acyclovir, ganciclovir, and foscarnet are used for systemic treatment of herpesvirus infections, while ophthalmic preparations of idoxuridine, trifluorothymidine, and vidarabine are available for herpes keratitis. For treatment of human immunodeficiency virus infections, zidovudine and didanosine are used. Immunomodulators, such as interferons and colony-stimulating factors, and immunoglobulins are being used increasingly for viral illnesses. While resistance to antiviral drugs has been seen, especially among AIDS patients, it has not become widespread and is being intensely studied. Increasingly, combinations of agents are being used: to achieve synergistic inhibition of viruses, to delay or prevent resistance, and to decrease dosages of toxic drugs. New approaches, such as liposomes carrying antiviral drugs and computer-aided drug design, are exciting and promising prospects for the future.

Mortality in patients with the acquired immunodeficiency syndrome treated with either foscarnet or ganciclovir for cytomegalovirus retinitis

BACKGROUND AND METHODS

We performed a multicenter, randomized, unblinded clinical trial (the Foscarnet-Ganciclovir Cytomegalovirus Retinitis Trial) designed to compare ganciclovir with foscarnet in the treatment of cytomegalovirus retinitis in patients with the acquired immunodeficiency syndrome (AIDS). Of 234 patients, 127 were randomly assigned to ganciclovir and 107 to foscarnet; the study drugs were administered according to a common protocol at the 11 participating clinical centers. Antiretroviral therapy (with zidovudine, didanosine, or dideoxycytidine) was given as dictated by best medical judgment. The patients were followed for the progression of retinitis, visual loss, and death.

RESULTS

Excess mortality in the ganciclovir group (as compared with the foscarnet group) led the Policy and Data Monitoring Board to recommend suspension of the treatment protocol 19 months after the trial started. As of that time, 65 of the patients assigned to ganciclovir had died, as compared with 36 of those assigned to foscarnet (51 percent vs. 34 percent, P = 0.007; relative risk, 1.79; 95 percent confidence interval, 1.17 to 2.73). The median survival was 8.5 months in the ganciclovir group and 12.6 months in the foscarnet group. Although the patients assigned to ganciclovir received less antiretroviral therapy on average than those assigned to foscarnet, the excess mortality could not be explained entirely by differences in exposure to antiretroviral drugs. In the forscarnet group, the only subgroup of patients identified as having excess mortality were those whose renal function was compromised at entry. There was no difference between the two treatment groups in the rate of progression of retinitis (relative risk, 0.95; P = 0.751).

CONCLUSIONS

These results suggest that for patients with AIDS, and cytomegalovirus retinitis, treatment with foscarnet offers a survival advantage over treatment with ganciclovir, although the patients may not tolerate foscarnet as well as ganciclovir.