Randomized multicenter trial of foscarnet versus ganciclovir for preemptive therapy of cytomegalovirus infection after allogeneic stem cell transplantation.

The present study compared foscarnet with ganciclovir for preemptive therapy of cytomegalovirus (CMV) infection after allogeneic blood or marrow stem cell transplantation (SCT). Patients with CMV infection, as detected by weekly antigenemia or polymerase chain reaction (PCR) in blood leukocytes, were randomized to intravenous therapy for 2 weeks with either foscarnet at 60 mg/kg or ganciclovir at 5 mg/kg administered every 12 hours; if CMV infection remained detectable, patients received an additional 2 weeks of intravenous foscarnet at 90 mg/kg or ganciclovir at 6 mg/kg given once daily for 5 days per week, after which therapy was stopped. Primary efficacy endpoint was the occurrence of CMV disease or death from any cause within 180 days after SCT. A total of 213 patients were treated with either foscarnet (n = 110) or ganciclovir (n = 103). Kaplan-Meier estimates of event-free survival within 180 days after SCT were similar in the 2 treatment groups (P =.6). During study treatment, severe neutropenia (< 0.5 x 10(9)/L) occurred in 11 (11%) patients on ganciclovir versus 4 (4%) patients on foscarnet (P =.04), and impaired renal function was observed in 5 (5%) patients on foscarnet versus 2 (2%) patients on ganciclovir (P =.4). Neutropenia or thrombocytopenia required discontinuation of ganciclovir in 6 (6%) patients but in no foscarnet-treated patient (P =.03). After allogeneic SCT, preemptive therapy of CMV infection with foscarnet shows similar efficacy as with ganciclovir, but is associated with a lower proportion of patients who develop severe neutropenia and who require discontinuation of antiviral therapy due to hematotoxicity.

Foscarnet--an alternative for cytomegalovirus prophylaxis after allogeneic stem cell transplantation?

Cytomegalovirus (CMV) disease is a serious complication after allogeneic hematopoietic stem cell transplantation (HSCT) and is associated with high morbidity and mortality. Early detection of the disease by antigenemia testing and polymerase chain reaction (PCR) along with pre-emptive antiviral therapy has been shown to be very effective in decreasing the incidence of CMV. We performed an uncontrolled observational study in 21 patients after HSCT (14 related, 7 unrelated donors) to evaluate the efficacy and toxicity of foscarnet administered as prophylaxis for CMV reactivation. Ten patients received bone marrow, and eleven patients received peripheral blood stem cells. All patients received foscarnet prophylaxis to study side effects, incidence of CMV reactivation, CMV disease, and transplant-related mortality. Foscarnet (90 mg/kg) was given every 12 h, day +11 to day +16. Thereafter, foscarnet (90 mg/kg) was given once per day, three times per week until day +60. The incidence of CMV reactivation detected by antigenemia (pp65 antigen) or PCR was 23.8% (5 of 21 patients). Two patients developed CMV disease and one patient died of CMV-pneumonia. Seventeen patients (81%) reported severe side effects, such as gastrointestinal disturbance, headache, and urethritis. In eight patients (38%), the dose of foscarnet had to be reduced and, in six patients (28.5%), foscarnet application was discontinued because of side effects. Compared with other groups, we believe that the potential benefit of foscarnet administration in this early setting is outweighed by the risks of severe toxicity.

Sodium lauryl sulfate increases the efficacy of a topical formulation of foscarnet against herpes simplex virus type 1 cutaneous lesions in mice.

The influence of sodium lauryl sulfate (SLS) on the efficacies of topical gel formulations of foscarnet against herpes simplex virus type 1 (HSV-1) cutaneous infection has been evaluated in mice. A single application of the gel formulation containing 3% foscarnet given 24 h postinfection exerted only a modest effect on the development of herpetic skin lesions. Of prime interest, the addition of 5% SLS to this gel formulation markedly reduced the mean lesion score. The improved efficacy of the foscarnet formulation containing SLS could be attributed to an increased penetration of the antiviral agent into the epidermis. In vitro, SLS decreased in a concentration-dependent manner the infectivities of herpesviruses for Vero cells. SLS also inhibited the HSV-1 strain F-induced cytopathic effect. Combinations of foscarnet and SLS resulted in subsynergistic to subantagonistic effects, depending on the concentration used. Foscarnet in phosphate-buffered saline decreased in a dose-dependent manner the viability of cultured human skin fibroblasts. This toxic effect was markedly decreased when foscarnet was incorporated into the polymer matrix. The presence of SLS in the gel formulations did not alter the viabilities of these cells. The use of gel formulations containing foscarnet and SLS could represent an attractive approach to the treatment of herpetic mucocutaneous lesions, especially those caused by acyclovir-resistant strains.

Intravitreal toxicology and therapeutic efficacy of the carboxymethyl ester of the 1-O-octadecyl-sn-glycerol-3-phosphonoformate (ODG-PFA-O-Me), a novel lipid antiviral prodrug for intraocular drug delivery.

This study was conducted to evaluate the vitreous clarity and intraocular therapeutic index of three preparations ofthe carboxymethyl ester of 1-O-octadecyl-sn-glycerol-3-phosphonoformate (ODG-PFA-O-Me), a long acting lipid derivative of foscarnet with potent anti-CMV activity. Twenty-six New Zealand white rabbits were intravitreally injected with one of three preparations of ODG-PFA-O-Me or control diluent. The vitreous clarity was graded after injection using indirect ophthalmoscopy and fundus photography. Drug intraocular toxicity was evaluated by electroretinography and by post-sacrifice tissue pathology using light and electron microscopy. Intravitreal injection of micellar ODG-PFA-O-Me showed variable local retinal toxicity and vitreal compound aggregates in eyes with the middle and high doses. The intraocular therapeutic index was lower than 465:1. Intravitreal injection of liposomal ODG-PFA-O-Me, either free acid or sodium salt, revealed clear vitreous for the 0.632 and 0.84 mM final intravitreal concentrations. No retinal toxicity was confirmed for the 1.12 mM final intravitreal concentration at the eight week observation following injection. The intraocular therapeutic index was between 585-1037:1. ODG-PFA-O-Me possesses better vitreous compatibility than ODG-PFA. Liposomal ODG-PFA-O-Me can be intravitreally injected with a resulting clear vitreous and high intraocular therapeutic index. Liposomal ODG-PFA-O-Me could be a long acting nontoxic intravitreous injectable drug for CMV retinitis.

Intravitreal toxicology in rabbits of two preparations of 1-O-octadecyl-sn-glycerol-3-phosphonoformate, a sustained-delivery anti-CMV drug.

PURPOSE: To determine intraocular toxicity and efficacy of the lipid prodrug of foscarnet, 1-O-octadecyl-sn-glycerol-3-phosphonoformate (ODG-PFA), as a long-acting, nontoxic intravitreous injectable drug delivery system for cytomegalovirus (CMV) retinitis. METHODS: ODG-PFA was synthesized by coupling the phosphonate residue of PFA to the 3 hydroxyl of 1-O-octadecyl-sn-glycerol and formulated as micelles and liposomes at concentrations so that, after injection into the rabbit vitreous, the resultant intravitreal concentrations were 0.2 mM, 0.63 mM, and 2 mM in micellar formulation and 0.02 mM, 0.063 mM, 0.2 mM, and 0.63 mM for liposomal formulation. The compounds were injected, and toxicology evaluations were performed. RESULTS: Intravitreal injections of micellar ODG-PFA resulted in aggregation of the material in vitreous and variable local retinal damage. Intravitreal injections of the liposomal ODG-PFA revealed even dispersion of the compounds and a clear vitreous, using final concentration in the vitreous of 0.2 mM. No intraocular toxicity was found with the 0.632 mM final concentration. The 50% inhibitory concentration (IC50) for CMV of ODG-PFA was 0.43+/-0.27 microM, and the therapeutic index of ODG-PFA after intravitreal injection was estimated to be 1470:1. CONCLUSIONS: Lipid-derivatized foscarnet liposome formulations may be a useful long-acting delivery system for the therapy of CMV retinitis.

Neurotoxicodynamics of the interaction between ciprofloxacin and foscarnet in mice.

The potential for convulsions induced by the coadministration of ciprofloxacin (CPFX) and foscarnet (PFA) may be due not to a change in the distribution of CPFX to the brain but to a potential CPFX-induced inhibition of gamma-aminobutyric acid (GABA)-GABA(A) receptor binding in the presence of PFA.

Determination of ocular toxicity in multiple applications of foscarnet iontophoresis.

This is the first study of multiple applications of drug iontophoresis in the eye. We repeated ocular foscarnet iontophoresis in 10 eyes of 10 rabbits every third day at the same paralimbal site for a total of seven applications over a period of 21 days to determine the efficacy and toxicity of multiple applications of ocular foscarnet iontophoresis. Mean vitreous human foscarnet concentration of 189 +/- 50.6 microM (SD) was achieved four hours after the seventh consecutive iontophoretic application over a period of twenty-one days. These levels were within the therapeutic range (25-800 microM) for the treatment of CMV retinitis and comparable to the intravitreal foscarnet concentrations achieved in eyes treated with a only a single application of ocular iontophoresis. Electroretinography (ERG) and Slit-lamp biomicroscopy responses revealed no evidence of ocular toxicity. Indirect ophthalmoscopy of the retinas and gross examinations of the calottes revealed a single, small burn in the retina and choroid corresponding to the application site of the iontophoresis probe similar to the lesion resulting from a single application of iontophoresis. Light and electron microscopy revealed local tissue injury and fibrosis at the iontophoresis site, but adjacent areas were unaffected.

In vivo toxicity of foscarnet and zidovudine given alone or in combination.

The toxicities of foscarnet (PFA) and zidovudine (AZT) given alone or in combination have been investigated in mice. PFA administered at a dose of 500 mg/kg/day and AZT at a dose of 400 mg/kg/day for 17 days caused clear hematotoxicity and nephrotoxicity. Each drug alone showed little hematotoxicity, but using a combination of both drugs significantly and dramatically decreased RBC (approximately 50%), Hb (approximately 43%), and hematocrit (approximately 43%) and increased platelets (approximately 45%) on Day 11 of treatment. It seems that there is a synergistic or at least an additive effect between PFA and AZT in terms of red blood cell toxicity. Surprisingly, AZT significantly increased serum creatinine levels on Days 5 and 11 of treatment (up to 40% increase), whereas PFA was less toxic (only approximately 17% increase on Day 5 of treatment). Using a combination of the two drugs, PFA seems to reduce the nephrotoxic effect of AZT on Day 11 of treatment. None of the treatments had any effect on BUN. At a lower dose level of 340 mg PFA/kg/day and 270 mg AZT/kg/day for 15 days there was hematotoxicity (much less evident than that at the higher dose level), but no nephrotoxicity. Electron microscopic examination of the renal cortex of animals from the experiments testing the higher dose levels revealed a clear vacuolization in proximal tubules and necrosis of mitochondria in distal tubules. These effects were more striking with the combination and less evident with PFA or AZT alone. In conclusion, even though we have used a high dose of AZT, there was synergistic/additive hematotoxicity. The combination was less nephrotoxic, only on Day 11 of treatment, than either of these agents used alone although histopathology, at the time of euthanization, showed more severe damage.

Synergistic inhibition of human immunodeficiency virus isolates (including 3'-azido-3'-deoxythymidine-resistant isolates) by foscarnet in combination with 2',3'-dideoxyinosine or 2',3'-dideoxycytidine.

The combinations of foscarnet plus 2',3'-dideoxyinosine and foscarnet plus 2',3'-dideoxycytidine synergistically inhibit the replication of human immunodeficiency virus type 1 isolates, including two 3'-azido-3'-deoxythymidine-resistant isolates. The combination of 2',3'-dideoxyinosine plus 2',3'-dideoxycytidine showed additive inhibition of the majority of the human immunodeficiency virus isolates tested. All three combinations showed pronounced antagonistic cytotoxicity and thus were less toxic to the growth of peripheral blood mononuclear cells than the separate drugs.

A method for detection of HHV-6 antigens and its use for evaluating antiviral drugs.

A simple and reproducible method for detection of human herpesvirus 6 (HHV-6) antigens was developed using a dot blot assay in order to assess virus titer and to evaluate the effect of antiviral drugs against HHV-6. The titer of virus stocks obtained by the dot blot assay was the same as that determined by an immunofluorescence assay (IFA). This method was then applied to evaluate the effect of several antiviral drugs against HHV-6, including phosphonoformic acid (PFA), 9-(2-hydroxyethoxymethyl)guanine (ACV), 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (DHPG) and (S)-1-[(3-hydroxy-2-phosphonylmethoxy)propyl]cytosine [(S)-HPMPC]. The end-point concentrations (EPC, which was determined visually) of DHPG and (S)-HPMPC were approximately 1 microgram/ml. These drugs were more effective than the others which had EPCs of approximately 16 micrograms/ml each. The EPC values of four drugs were almost similar to EC90 values determined by measuring density of each dot blot. Thus, the EPC values can be utilized to determine the efficacy of these drugs in the inhibition of HHV-6 replication. The block in virus replication was not due to toxic effect of these drugs on cord blood mononuclear cells (CBMCs). These results suggest that a dot blot method which detects HHV-6 antigens can be useful for titrating virus yield and evaluating antiviral drugs against HHV-6 replication.

Anti-infective therapy for viral pneumonia.

The recognition of viruses as causes of pneumonia in both immunocompetent and immunocompromised hosts has expanded dramatically. The number of therapeutic agents available for treatment of these illness also has increased in the last decade. Each of these agents has demonstrated a limited therapeutic indication for treatment of viral pneumonia. Many of these agents inhibit viral DNA synthesis through actions as nucleoside analogs (such as acyclovir and ganciclovir). However, a variety of alternative mechanisms of inhibition of viral replication are used. Ribavirin, while being a nucleoside analogue, also appears to exert broad antiviral activity by a variety of enzymatic inhibitory mechanisms. Foscarnet, an inorganic pyrophosphate analogue, offers additional treatment options for herpesviruses by acting as a direct virus DNA polymerase inhibitor. The tricyclic amines amantadine and rimantadine inhibit influenza A replication by interfering with viral uncoating after cell penetration. Thus, these two agents are largely effective as prophylaxis. The search for novel antiviral drugs, such as neuraminadases inhibitors with selective influenza activity, is currently in progress.

Ocular toxicity of iontophoretic foscarnet in rabbits.

Transscleral iontophoresis of foscarnet is a noninvasive drug delivery system for the local treatment of cytomegalovirus (CMV) retinopathy. We determined the retinotoxic effects of transscleral iontophoresis of foscarnet. Slit-lamp biomicroscopy revealed no toxic effects for any of the treated eyes. Indirect ophthalmoscopy showed retinal and choroidal burns 1-3 mm in diameter at the site of iontophoresis in both foscarnet-treated eyes and saline-treated control eyes. Light and electron microscopy revealed focal retinal, retinal pigment epithelial, and choroidal necrosis at the site of iontophoresis but no abnormalities elsewhere. Ganzfeld electroretinographic studies revealed no response differences between foscarnet-treated eyes vs. controls.

Toxicologic and pharmacokinetic analysis of intravitreal injections of foscarnet, either alone or in combination with ganciclovir.

PURPOSE: The retinal toxicity of single and repeated intravitreal injections of foscarnet was investigated. In addition, the effects of a combination of foscarnet and ganciclovir were studied, and a pharmacokinetic study to determine the ocular pharmacokinetics of foscarnet after intravitreal injection was carried out. METHODS: Forty rabbits (both albino and pigmented) were used in this study. The electroretinographic (ERG) a-waves and b-waves and oscillatory potentials (OP) were used as as indicators of retinal toxicity. Potential toxicity was also assessed by ophthalmoscopy and histologic studies (light and electron microscopy). RESULTS: The a-wave and b-wave were not deteriorated with 2.4 mg foscarnet after single or repeated injections. The OP remained unchanged. There was no ERG change after intravitreal injection of a combination of both drugs. No evidence of retinal toxicity was observed by indirect ophthalmoscopy in any case. Light and electron microscopy on semithin sections of retina failed to demonstrate any adverse effects, and showed normal organization and cytoarchitecture of all the layers of the retina without evidence of cytopathology. The ocular pharmacokinetics of foscarnet determined by noncompartmental analysis showed a 34-hour terminal elimination half-life and an apparent volume of distribution of 1.9 ml. CONCLUSIONS: Based on these results, high doses of foscarnet were not judged toxic to the rabbit retina, with single or repeated injections. Moreover, concomitant injection of the two drugs did not induce any retinal toxicity. These findings suggest that when systemic treatment is to be stopped in patients with AIDS for toxic side effects, either ganciclovir or foscarnet may be used intravitreally as an alternative. Because a combination of the two drugs has been shown to be synergistic, both ganciclovir and foscarnet might be simultaneously injected into the vitreous cavity to block progression of cytomegalovirus retinitis.

Intravitreal use of foscarnet: retinotoxicity of repeated injections in the rabbit eye.

Cytomegalovirus retinitis is the most frequent ocular opportunistic infection in AIDS patients. In selected cases intravitreal injections of foscarnet may be the sole therapeutic possibility. The retinal toxicity of the drug, however, has not yet been thoroughly investigated. Our present study in the rabbit eye concerns the retinal toxicity of 2, 4, and 6 intravitreal injections of 3.6 mg of foscarnet, using ophthalmoscopy, histology and electrophysiology to evaluate retinal damage. The results show that foscarnet may be employed intravitreally without substantial damage to the retina, but only in short courses of injections when no other therapeutic possibility may be utilized.

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

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

A dose escalation study to determine the toxicity and maximally tolerated dose of foscarnet.

OBJECTIVE: To determine the maximum tolerated dose of intravenous foscarnet (trisodium phosphonoformate hexahydrate); and to examine antiviral activity at plasma levels shown to inhibit HIV-1. DESIGN: Dose escalation study in three male subjects with AIDS who received foscarnet by continuous intravenous infusion at a dose of 200 mg/kg per day, after a 20 mg/kg loading dose. The dose was increased until a plasma level > 150 micrograms/ml was attained. RESULTS: Foscarnet was discontinued due to progressive renal insufficiency in all three patients (days 11, 19, and 21). Renal function normalized in all three, and no adverse sequelae due to foscarnet were observed at 1 year of follow-up. A seizure was observed in one patient on day 19. Maximum daily doses of foscarnet achieved were 395 mg/kg, 389 mg/kg, and 523 mg/kg. No changes in serum Ca2+, Mg2+, or PO4- were observed. CONCLUSIONS: Renal effects and toxicity of foscarnet in evolving renal insufficiency is self-limiting and reversible when the drug is discontinued. Incremental increases in dose can result in rapid rises in the plasma level with renal failure and may be compounded by concomitant medications and underlying illnesses.