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

Susceptibilities of human cytomegalovirus clinical isolates to BAY38-4766, BAY43-9695, and ganciclovir

BAY38-4766 and BAY43-9695 are nonnucleosidic compounds with activities against human cytomegalovirus (HCMV). Two phenotypic assays were used to determine the drug susceptibilities of 36 HCMV clinical isolates to the BAY compounds and ganciclovir. Using either assay, both BAY compounds at a concentration of approximately 1 microM inhibited the replication of all 36 HCMV clinical isolates, including 11 ganciclovir-resistant clinical isolates, by 50%.

Fluid and electrolyte abnormalities

Patients with cancer are at risk for developing a variety of fluid and electrolyte disturbances caused by the disease process or by complications from therapy. An understanding of the pathophysiology of these potential abnormalities allows the clinician to manage patients expectantly and to avoid severe metabolic disarray by correcting imbalances promptly.

The ganciclovir implant plus oral ganciclovir versus parenteral cidofovir for the treatment of cytomegalovirus retinitis in patients with acquired immunodeficiency syndrome: The Ganciclovir Cidofovir Cytomegalovirus Retinitis Trial

PURPOSE

To compare the regimen of the ganciclovir implant plus oral ganciclovir to one of intravenous cidofovir for the treatment of cytomegalovirus retinitis.

METHODS

Sixty-one patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis were randomized either to the regimen of the ganciclovir implant plus oral ganciclovir, 1 gm three times daily, or intravenous cidofovir, 5 mg/kg once weekly for two doses, followed by 5 mg/kg every other week.

RESULTS

Mortality was similar between the two treatment groups. Mortality rates were 0.41 per person-year in patients assigned to the ganciclovir regimen and 0.49 per person-year in patients assigned to cidofovir (P =.59). Ocular outcomes were similar between the two groups. Retinitis progression occurred at a rate of 0.67 per person-year in the ganciclovir group and 0.71 per person-year in the cidofovir group (P =.72). A loss of visual acuity of 15 letters or more occurred at a rate of 0.78 per person-year in the ganciclovir group and 0.47 per person-year in the cidofovir group (P =.28). The rate of loss of visual field was 7 degrees per month in the ganciclovir group and 2 degrees per month in the cidofovir group (P =.048). Vitreous hemorrhage was more common in the ganciclovir implant group (0.13 per person-year) than in the cidofovir group (no cases, P =.014), whereas uveitis appeared to be more common in the cidofovir group (0.35 per person-year) than in the ganciclovir group (0.09 per person-year, P =.066). Nephrotoxicity (serum creatinine 1.6 mg/dL or greater) occurred at a rate of 0.18 per person-year in the ganciclovir group and 0.48 per person-year in the cidofovir group (P =.10).

CONCLUSIONS

Although the small number of patients in this study limits definitive interpretation, these data suggest that in the era of highly active antiretroviral therapy, the regimens of the ganciclovir implant plus oral ganciclovir and of intravenous cidofovir are similar for controlling cytomegalovirus retinitis and preventing visual loss but have different side effects.

Ocular pharmacokinetics in rabbits using a novel dual probe microdialysis technique

Ocular infections involve delicate internal structures of the eye that often require treatment with antimicrobial agents. A major constraint to the study of ocular drug absorption from systemic administration is the inaccessibility of the vitreous for continuous serial sampling. A novel dual probe microdialysis technique has been employed in our laboratory, which will enable the delineation of complete ocular pharmacokinetics of a drug. New Zealand albino rabbits weighing 2--2.5 kg were used. The animals were kept under anesthesia throughout the experiment. A concentric probe was implanted in the vitreous chamber about 3 mm below the corneal scleral limbus. Simultaneously a linear probe was implanted in the anterior chamber across the cornea. Intraocular pressure (IOP) was measured using Schiotz tonometer. The total protein concentrations in the aqueous and vitreous humors were determined using the Bio-Rad protein assay method. The aqueous and vitreous elimination kinetics of fluorescein were studied after intravitreal and systemic administrations over a period of 10 hr. Microdialysis technique was also compared to the conventional direct sampling technique by determining the intravitreal kinetics of fluorescein. Results suggest that IOP reverted to normal within 2 hr after the implantation of the probes. The increase in the vitreal total protein concentration was not significantly different from the baseline. The increase in the aqueous total protein concentration was less than five times the basal concentration throughout the experiment. The blood-aqueous and blood-retinal barrier integrity was delineated by determining the permeability index for fluorescein and were found to be 9.48 +/- 4.25% and 1.99 +/- 0.66% for the anterior and vitreous chamber, respectively. The rate constant of penetration of fluorescein into the anterior chamber was found to be 8.48 +/- 1.33 x 10(-2) min(-1), which was significantly higher than into the vitreous i.e. 4.34 +/- 2.82 x 10(-2) min(-1). The terminal elimination rate constant of fluorescein from the anterior chamber (1.48 +/- 0.79 x 10(-2) min(-1)) was found to be similar to that of the plasma terminal elimination rate constant (1.57 +/- 0.25 x 10(-2) min(-1)), but significantly higher than from the vitreous (3.0 +/- 0.7 x 10(-3) min(-1)). The terminal vitreal elimination rate constant of fluorescein after intravitreal administration was found to be similar by both microdialysis (3.98 +/- 0.6 x 10(-3) min(-1)) and direct sampling (4.38 +/- 1.4 x 10(-3) min(-1)) techniques. In case of direct sampling technique the area under the vitreous concentration-time curve was higher compared to that obtained by the microdialysis technique. There was no breakdown of the blood ocular barriers as shown by a very small change in the intraocular fluid protein concentrations. This was also confirmed by the fluorescein kinetics, which were in accordance with the previous studies. IOP data suggests that the intraocular fluid dynamics were not affected and the animals stabilized within 2 hr after the implantation of the probes. Fluorescein data suggests that the vitreous compartment is surrounded by a tighter barrier compared to the anterior chamber. This technique appears to be more sensitive, reproducible and requires only one animal for the determination of entire ocular pharmacokinetic profile.

Discontinuation of maintenance therapy for cytomegalovirus retinitis in HIV-infected patients receiving highly active antiretroviral therapy

OBJECTIVE

To study the safety of discontinuing cytomegalovirus (CMV) maintenance therapy among patients with cured CMV retinitis receiving highly active antiretroviral therapy (HAART).

METHODS

Patients with a history of CMV retinitis who were receiving anti-CMV maintenance therapy and who had a CD4 cell count > 75 x 10(6) cells/l and a plasma HIV RNA level < 30000 copies/ml while on HAART were included in a multicentre prospective study. Maintenance therapy for CMV retinitis was discontinued at enrolment and all the patients were monitored for 48 weeks by ophthalmological examinations and by determination of CMV markers, CD4 cell counts and plasma HIV RNA levels. T helper-1 anti-CMV responses were assessed in a subgroup of patients. The primary study endpoint was recurrence of CMV disease.

RESULTS

At entry, the 48 assessable patients had been taking HAART for a median of 18 months. The median CD4 cell count was 239 x 10(6) cells/l and the median HIV RNA load was 213 copies/ml. Over the 48 weeks, 2 of the 48 patients had a recurrence of CMV disease. The cumulative probability of CMV retinitis relapse was 2.2% at week 48 (95% confidence interval, 0.4-11.3) and that of all forms of CMV disease 4.2%. CMV blood markers remained negative throughout follow-up. The proportion of patients with CMV-specific CD4 T cell reactivity was 46% at baseline and 64% at week 48.

CONCLUSIONS

CMV retinitis maintenance therapy may be safely discontinued in patients with CD4 cell counts above 75 x 10(6) cells/l who have been taking HAART for at least 18 months.

Incremental cost effectiveness of prophylaxis for cytomegalovirus disease in patients with AIDS

Cytomegalovirus (CMV) disease, an opportunistic complication in patients with AIDS, causes substantial morbidity and has high treatment costs. Although prevention of this disease is highly desirable, incremental cost-effectiveness estimates for proposed prophylactic strategies in the era prior to the availability of highly active antiretroviral therapy (HAART) were unfavourable relative to other specific antimicrobial prophylactic strategies in patients with AIDS. With the availability of HAART, several inputs upon which previous estimates of the incremental cost-effectiveness ratio for anti-CMV prophylaxis were based probably changed substantially. To assess the incremental cost effectiveness of prophylaxis in the HAART era, data are needed on visual outcomes and utility for patients with CMV retinitis and AIDS, on better strategies for identifying subpopulations at high risk for CMV disease and on the prophylactic efficacy of valganciclovir. Cost-effectiveness analysis could potentially contribute by exploring thresholds of population risk, prophylactic effectiveness, and drug pricing in order to identify conditions under which prophylaxis for CMV disease in patients with AIDS could potentially become cost effective.

Economic evaluation of systemic treatments for cytomegalovirus retinitis in patients with AIDS

OBJECTIVE

To determine the cost of using systemic therapy to treat newly diagnosed cytomegalovirus (CMV) retinitis in persons with AIDS.

DESIGN

Incidence-based simulation model of CMV treatment from a government payer perspective.

SETTING

Swiss healthcare system.

PATIENTS AND PARTICIPANTS

Patients with AIDS and newly diagnosed CMV retinitis.

INTERVENTIONS

Patients were assigned to 1 of 4 treatment regimens for induction and maintenance therapy: (i) intravenous (IV) cidofovir induction and maintenance (cidofovir IV/IV); (ii) IV foscarnet induction and maintenance (foscarnet IV/IV); (iii) IV ganciclovir induction and maintenance (ganciclovir IV/IV); and (iv) IV ganciclovir induction and oral (PO) ganciclovir maintenance (ganciclovir IV/PO). Following a second relapse, patients were assigned to one of the other regimens.

MAIN OUTCOME MEASURES

Time to first and subsequent progression, duration of maintenance treatment and direct medical expenditures [1998 Swiss francs (SwF)] .

RESULTS

The median time to first progression was longest for cidofovir IV/IV, followed by foscarnet IV/IV, ganciclovir IV/IV and ganciclovir IV/PO. Mean survival was 13 months and mean costs for this period in the base case were lowest in those initially treated with cidofovir (SwF146,742), followed by initial treatment with foscarnet IV/IV (SwF194,809), ganciclovir IV/PO (SwF195,190) and ganciclovir IV/IV (SwF243,964). Costs were most sensitive to changes in efficacy estimates.

CONCLUSIONS

Of the regimens studied, initiation of treatment with systemic cidofovir appears least costly over a 13-month period.

Management and Prevention of Opportunistic Infections in the HIV-Infected Patient

With the introduction of potent antiretroviral therapy, the incidence of opportunistic infections (OIs) as well as death has dramatically decreased since 1996. Opportunistic infections are seen mainly in three groups: (1) newly diagnosed patients not receiving antiretroviral therapy and presenting with an OI, (2) patients nonadherent to antiretroviral and OI treatment regimens or (3) patients whose antiretroviral therapy has failed. This article will review the most common opportunistic infections (OIs) seen in the HIV-infected individual and their treatment. The current guidelines for the prophylaxis against these OIs will also be discussed.

A double-blind placebo-controlled crossover trial of intravenous magnesium sulfate for foscarnet-induced ionized hypocalcemia and hypomagnesemia in patients with AIDS and cytomegalovirus infection

Foscarnet (trisodium phosphonoformate hexahydrate) is an antiviral agent used to treat cytomegalovirus disease in immunocompromised patients. One common side effect is acute ionized hypocalcemia and hypomagnesemia following intravenous administration. Foscarnet-induced ionized hypomagnesemia might contribute to ionized hypocalcemia by impairing excretion of preformed parathyroid hormone (PTH) or by producing target organ resistance. Prevention of ionized hypomagnesemia following foscarnet administration could blunt the development of ionized hypocalcemia. To determine whether intravenous magnesium ameliorates the decline in ionized calcium and/or magnesium following foscarnet infusions, MgSO(4) at doses of 1, 2, and 3 g was administered in a double-blind, placebo-controlled, randomized, crossover trial to 12 patients with AIDS and cytomegalovirus disease. Overall, increasing doses of MgSO(4) reduced or eliminated foscarnet-induced acute ionized hypomagnesemia. Supplementation, however, had no discernible effect on foscarnet-induced ionized hypocalcemia despite significant increases in serum PTH levels. No dose-related, clinically significant adverse events were found, suggesting that intravenous supplementation with up to 3 g of MgSO(4) was safe in this chronically ill population. Since parenteral MgSO(4) did not alter foscarnet-induced ionized hypocalcemia or symptoms associated with foscarnet, routine intravenous supplementation for patients with normal serum magnesium levels is not recommended during treatment with foscarnet.

Prognostic factors of survival of HIV-infected patients with cytomegalovirus disease: Aquitaine Cohort, 1986-1997. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine (GECSA)

OBJECTIVE

To analyse survival of HIV-infected patients who developed cytomegalovirus (CMV) disease and to identify prognostic factors of their survival.

METHODS

Cases of CMV disease diagnosed in the Aquitaine Cohort of HIV-infected patients (n = 4297) during the 1986-1996 period, were reviewed using standardised definitions. Follow-up was extended to December 1997. Cox model was used to determine factors associated with survival after the initial manifestations of CMV disease, considering protease inhibitor (PI) prescription and anti-CMV treatment as time dependent covariates.

RESULTS

253 patients presented a CMV disease of which 221 (87.3%) died (median survival: 7 months). A better prognosis for survival was associated with: PI prescription [relative hazard (RH): 0.26; 95% confidence interval (CI): 0.11-0.59], anti-CMV treatment (RH: 0.37; CI: 0.25-0.54), CD4+ lymphocyte cell count > 50/mm3 (RH: 0.66; CI: 0.47-0.94) and absence of neoplasia (RH: 0.70; CI: 0.52-0.94) whereas the disseminated CMV disease worsened prognosis (RH: 1.83; CI: 1.20-2.80).

CONCLUSION

Antiretroviral treatment including PI, improved short-term prognosis of CMV disease regardless of its clinical manifestations.

Foscarnet-induced electrolyte abnormalities in a bone marrow transplant patient receiving parenteral nutrition

Cytomegalovirus (CMV) is a serious complication of immunosuppressed patients receiving bone marrow transplantation. Foscarnet, a pyrophosphate analog, has been used in the treatment of CMV infections. Renal impairment and electrolyte abnormalities are potential adverse reactions associated with the use of foscarnet. We report a case of significant electrolyte changes after initiation of foscarnet in a bone marrow transplant patient receiving parenteral nutrition.

Antiviral properties of a series of 1,6-naphthyridine and 7, 8-dihydroisoquinoline derivatives exhibiting potent activity against human cytomegalovirus

A series of 1,6-naphthyridine (L. Chan, H. Jin, T. Stefanac, J. F. Lavallee, G. Falardeau, W. Wang, J. Bedard, S. May, and L. Yuen, J. Med. Chem. 42:3023-3025, 1999) and isoquinoline (L. Chan, H. Jin, T. Stefanac, W. Wang, J. F. Lavallee, J. Bedard, and S. May, Bioorg. Med. Chem. Lett. 9:2583-2586, 1999) analogues exhibiting a high level of anti-human cytomegalovirus (HCMV) activity were investigated in a series of studies aimed at better understanding the mechanism of action of some representatives of this class of compounds. In vitro antiviral profiling revealed that these compounds were active against a narrow spectrum of viruses, essentially the human herpesviruses and type 2 rhinovirus. In HCMV assays, a 39- to 223-fold lower 50% inhibitory concentration was obtained for compound A1 than for ganciclovir against strains AD 169 and Towne. In addition, ganciclovir, foscarnet, cidofovir, and BDCRB (2-bromo-5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole)-resistant HCMV strains remained susceptible to 1,6-naphthyridines and 7, 8-dihydroisoquinolines tested in this study, supporting the view that a novel mechanism of action could be involved. Drug combination studies showed a small but significant synergistic antiviral effect between compound B2 and ganciclovir. Cytotoxicity profiling of representative compounds under various cell growth conditions indicated a generally similar cytotoxic effect, relative to ganciclovir, in log-phase growing cells. However, in stationary cells, a relatively higher level of toxicity was observed than that for control compound. Effect of time of drug addition showed that the anti-HCMV activity of compound A1, ganciclovir, and cidofovir was lost at approximately the same time (72 h postinfection), indicating that the compound was affecting events at the early and late stage of virus replication. This interpretation is also supported by reduction of de novo synthesis of pp65 tegument protein and lack of any effect of the compound on viral adsorption. A reduction of the HCMV enhancer-promoter-directed luciferase expression was also observed in a stably transfected cell line when compound A1 was present at relatively high concentrations.

Removal of Foscarnet by Hemodialysis using Dialysate-Side Values

Foscarnet is an antiviral agent widely used in the treatment of cytomegalovirus (CMV) infection. We describe a cardiac transplant patient, who while being maintained with hemodialysis because of tobramycin-induced acute renal failure, was given Foscarnet for disseminated CMV infection. Using dialysate-side clearance methodology, we found the dialyzer clearance of Foscarnet to be in the order of 89 ml/min. (Int J Artif Organs 2000; 23: 165–7)

Therapeutic developments in cytomegalovirus retinitis

The incidence of cytomegalovirus (CMV) retinitis in AIDS has declined significantly due to the use of highly active antiretroviral therapy (HAART). However, patients with HIV, especially those failing HAART, may still suffer with CMV retinitis, which can lead to significant loss of vision and blindness. Ganciclovir has traditionally been considered the recommended treatment for CMV retinitis; however, due to side effects and the possibility of developing viral resistance, other agents may be preferred in certain situations. Foscarnet, which has similar efficacy to ganciclovir but a different side effect profile, is more difficult to administer and is less well-tolerated. Intravenous cidofovir, which may be more effective than either iv. ganciclovir or foscarnet, can also be used as a first line agent; however, it is associated with toxicity (renal and ocular) and thus needs careful use. Local therapy for CMV retinitis has been a significant advance. The intraocular ganciclovir implant has the highest efficacy of the approved agents and is well-tolerated. Fomivirsen, an oligonucleotide injected intravitreally, is a newly approved agent which offers alternative treatment. Intravitreal ganciclovir or foscarnet, although not approved, have been used successfully in some patients especially those with recurrent or refractory disease. The development of new anti-CMV agents has been stalled by the decreased incidence of the disease. Valganciclovir, a prodrug of ganciclovir, offers excellent oral bioavailability and is the closest to approval of all the new anti-CMV drugs. High ganciclovir blood levels are achieved without the complications associated with the requirement for long-term iv. access. The monoclonal antibody (mAb) MSL-109, did not offer a significant advantage when added to traditional anti-CMV therapy. Development plans of other agents such as cyclic HPMPC and lobucavir have been put on hold by their respective manufacturers. Adefovir is a nucleotide analogue that possesses anti-CMV activity, but is currently only being pursued for the treatment of hepatitis B virus. Other compounds possessing significant anti-CMV activity, including BAY 38-4766 and GW1263W94 are still in the early stages of development.

Fomivirsen - a phosphorothioate oligonucleotide for the treatment of CMV retinitis

Fomivirsen is a 21-nucleotide phosphorothioate oligonucleotide which, when injected into a human eye, is capable of inhibiting CMV retinitis. Its mode of action is consistent with an antisense mechanism. Prior to human trials, fomivirsen was tested in a number of in vitro cell lines and was found to inhibit CMV replication in a dose-dependent manner with a mean 50% inhibitory concentration between 0.03 and 0.2 microM. Intravitreal drug clearance studies have revealed first-order kinetics with a half-life in the rabbit of 62 hours. In a clinical trial of patients with newly diagnosed CMV retinitis receiving 165 mg per injection, time to progression was interpolated to 71 days with 44% of the patients remaining on treatment for over one year. In patients who failed other anti-CMV treatments, the interpolated time to progression was 91 days when receiving 330 mg per injection. No systemic absorption of the drug could be detected. Reported adverse events have been for the most part mild to moderate in intensity and either resolved spontaneously or were treatable with topical medications. Locally administered fomivirsen effectively inhibits CMV retinitis using a mode of action which is complementary to existing DNA polymerase inhibitors.

Reducing chorioretinal viral counts with intravitreal foscarnet injections in a rabbit model of Herpes simplex virus type-1 retinitis

The efficacy of intravitreal foscarnet injections was evaluated in a rabbit model of Herpes simplex virus type-1 (HSV-1) retinitis. In untreated infected animals, viral titration revealed that the optic chiasm, vitreous and chorioretina were positive for HSV-1. On the other hand, foscarnet treatment significantly decreased the viral count in the chorioretina when compared to the untreated group. Immunolocalization of HSV in untreated infected animals clearly showed infected cells in the outer and inner layers of the retina and also in the ciliary body of the eye. Clinical examination by indirect ophthalmoscopy indicated an absence of optic nerve congestion and a lower level of vitritis in foscarnet treated animals compared to the untreated group. It is concluded that intravitreal injections of foscarnet reduced the viral titer in the chorioretina in a rabbit model of HSV-1 retinitis. This route of administration might be valuable for the treatment of CMV retinitis in AIDS patients with sight threatening lesions or intolerance to intravenous anti-CMV drugs.

Management of CMV retinitis in the era of highly active antiretroviral therapy

Although the epidemiological features of CMV retinitis is changing in patients receiving highly active antiretroviral therapy (HAART), continued attention must be paid to detect and treat earlier CMV infections in AIDS patients to prevent severe ophthalmic complications. Initial therapy must be based on characteristics of the CMV retinitis and patient conditions. Long term therapy of HAART must be pursued, even in patients with increased CD4 and undetectable HIV viral load, until results from large controlled studies are available. reserved.

Nonnucleoside pyrrolopyrimidines with a unique mechanism of action against human cytomegalovirus

Based upon a prior study which evaluated a series of nonnucleoside pyrrolo[2,3-d]pyrimidines as inhibitors of human cytomegalovirus (HCMV), we have selected three active analogs for detailed study. In an HCMV plaque-reduction assay, compounds 828, 951, and 1028 had 50% inhibitory concentrations (IC(50)s) of 0.4 to 1.0 microM. Similar results were obtained when 828 and 951 were examined by HCMV enzyme-linked immunosorbent assay (IC(50)s = 1.9 and 0.4 microM, respectively) and when 828 was tested in a viral DNA-DNA hybridization assay (IC(50) = 1.3 microM). In yield-reduction assays with a low multiplicity of infection (MOI), all three compounds caused multiple log(10) reductions in virus titer, and the activities of these compounds were comparable to the activity of ganciclovir (GCV; IC(90) = 0.2 microM). In contrast to the reduction of viral titers by GCV, the reduction of viral titers by 828, 951, and 1028 decreased with increasing MOI. Cytotoxicity in human foreskin fibroblasts and KB cells ranged from 32 to >100 microM. In addition, 828 (the only compound tested) was less toxic against human bone marrow progenitor cells than GCV. Time-of-addition and time-of-removal studies established that the three pyrrolopyrimidines inhibited HCMV replication before GCV had an effect on viral DNA synthesis but after viral adsorption. Compound 828 was equally effective against GCV-sensitive and GCV-resistant HCMV clinical isolates. Combination studies with 828 and GCV showed that the effects of the two compounds on HCMV were additive but not synergistic. Taken together, the data indicate that these pyrrolopyrimidines target a viral protein that is required in an MOI-dependent manner and that is expressed early in the HCMV replication cycle.

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.

Antiviral drug susceptibility assays: going with the flow

This review describes the procedures for the use of fluorochrome labeled monoclonal antibodies and flow cytometry for the detection and quantification of virus infected cells. The application of this technology for (1) identifying virus infected cells in clinical specimens obtained from human cytomegalovirus (HCMV) and human immunodeficiency virus (HIV) infected individuals; (2) screening antiviral compounds active against HCMV, HDSV and HIV; and (3) performing drug susceptibility testing for HCMV, HSV and HIV clinical isolates are reviewed. The flow cytometry drug susceptibility assay is rapid, quantitative, and easily performed. It should be considered by anyone interested in performing drug susceptibility testing for any virus for which there are reliable monoclonal antibodies.

Treatment of recurrent cytomegalovirus retinitis with the ganciclovir implant

PURPOSE

To evaluate preoperative characteristics and outcome of the treatment of recurrent cytomegalovirus (CMV) retinitis with the ganciclovir implant.

METHODS

Records of 54 patients with acquired immunodeficiency syndrome and active, previously treated CMV retinitis who received a ganciclovir implant in one (n = 31) or both (n = 23) eyes were reviewed. Entry criteria included prior insertion and removal of an indwelling catheter or failure to respond to tolerated doses of ganciclovir and foscarnet. Preoperative factors that might correlate with outcome were analyzed, including demographic factors, duration of human immunodeficiency virus disease and CMV retinitis, indications for surgery, prior anti-CMV treatment, and extent of retinitis.

RESULTS

Forty-six patients completed 1 month of follow-up and were analyzed for outcome. Thirty-one (67.4%) had inactive retinitis at 1 month vs 15 (32.6%) with active retinitis, and they received a mean of 23.5 +/- 22.9 weeks of preoperative ganciclovir vs 58.0 +/- 52.0 weeks in patients with active retinitis (P = .003). Involvement of more than 25% of retinal area by CMV retinitis was also correlated with activity at 1 month (P < .001). Patients who received implants because of lack of venous access had a median time to progression of 8.0 +/- 3.0 months vs 2.0 +/- 1.2 months for patients who had inadequate response or intolerance to intravenous medication (P = .073). Patients with 6 months or less vs more than 6 months of preoperative ganciclovir treatment had progression at a median time of 8.0 +/- 1.7 months vs 2.0 +/- 0.3 months, respectively (P = .016).

CONCLUSION

Longer duration of preoperative ganciclovir or larger area of CMV retinitis correlates with lower success of ganciclovir implant therapy for recurrent retinitis.

Comparative study of the anti-human cytomegalovirus activities and toxicities of a tetrahydrofuran phosphonate analogue of guanosine and cidofovir

Cidofovir is the first nucleoside monophosphate analogue currently being used for the treatment of human cytomegalovirus (HCMV) retinitis in individuals with AIDS. Unfortunately, the period of therapy with the use of this compound may be limited due to the possible emergence of serious irreversible nephrotoxic effects. New drugs with improved toxicity profiles are needed. The goal of this study was to investigate the anticytomegaloviral properties and drug-induced toxicity of a novel phosphonate analogue, namely, (-)-2-(R)-dihydroxyphosphinoyl-5-(S)-(guanin-9'-yl-methyl) tetrahydrofuran (compound 1), in comparison with those of cidofovir. The inhibitory activities of both compounds on HCMV propagation in vitro were similar against the AD 169 and Towne strains, with 50% inhibitory concentrations ranging from 0.02 to 0.17 microgram/ml for cidofovir and < 0.05 to 0.09 microgram/ml for compound 1. A clinical HCMV isolate that was resistant to ganciclovir and that had a known mutation within the UL54 DNA polymerase gene and a cidofovir-resistant laboratory strain derived from strain AD 169 remained sensitive to compound 1, whereas their susceptibilities to ganciclovir and cidofovir were reduced by 33- and 10-fold, respectively. Both compound 1 and cidofovir exhibited equal potencies in an experimentally induced murine cytomegalovirus (MCMV) infection in mice, with a prevention or prolongation of mean day to death at dosages of 1.0, 3.2, and 10.0 mg/kg of body weight/day. In cytotoxicity experiments, compound 1 was found to be generally more toxic than cidofovir in cell lines Hs68, HFF, and 3T3-L1 (which are permissive for HCMV or MCMV replication) but less toxic than cidofovir in MRC-5 cells (which are permissive for HCMV replication). Drug-induced toxic side effects were noticed for both compounds in rats and guinea pigs in a 5-day repeated-dose study. In guinea pigs, a greater weight loss was noticed with cidofovir than with compound 1 at dosages of 3.0 and 10.0 mg/kg/day. An opposite effect was detected in rats, which were treated with the compounds at relatively high dosages (up to 100 mg/kg/day). Compound 1 and cidofovir were nephrotoxic in both rats and guinea pigs, with the epithelium lining the proximal convoluted tubules in the renal cortex being the primary target site. The incidence and the severity of the lesions were found to be dose dependent. The lesions observed were characterized by cytoplasm degeneration and nuclear modifications such as karyomegaly, the presence of pseudoinclusions, apoptosis, and degenerative changes. In the guinea pig model, a greater incidence and severity of lesions were observed for cidofovir than for compound 1 (P < 0.001) with a drug regimen of 10 mg/kg/day.

A high throughput colorimetric cell proliferation assay for the identification of human cytomegalovirus inhibitors

A colorimetric assay based on the cleavage of the tetrazolium salt WST-1 has been developed for human cytomegalovirus (HCMV) antiviral susceptibility testing and adapted to a microtiter plate format. Optimal conditions were determined and the standard routine assay was calibrated with a viral input of 0.05-0.10 plaque forming unit (p.f.u.)/cell with a density of 2000 cells/well in a 96-well microtiter plate for an incubation period of 7 days. Ganciclovir (9-(2-hydroxy-1(hydroxymethyl) ethyoxymethyl) guanine; DHPG), and cidofovir ((S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine; HPMPC) were used as positive control test compounds to validate the assay. The effective EC50 concentration values obtained with the two antiviral compounds in the present assay were in good agreement with plaque reduction assay results performed in parallel experiments. This method presents the advantage of being easy and rapid to perform, reliable, reproducible, and convenient for use in a high throughput screening capacity.

Changing patterns of HIV related ocular disease

Cytomegalovirus (CMV) retinitis is the commonest ocular complication of AIDS and the prevention of recurrence has been dependent on lifelong maintenance treatment. Recently there has been a dramatic downturn in the number of new cases of CMV retinitis, which has been attributed to the introduction of highly active antiretroviral therapy (HAART) and subsequent improved survival. Whereas paucity of inflammation has been considered to be the hallmark of the ophthalmic manifestations of AIDS, with immune recovery, a new pattern of ophthalmic AIDS has emerged. This is characterised by a heightened inflammatory response and more frequent complications associated with this response--for example, vitritis, cystoid macular oedema. In spite of this, regression of CMV retinitis has been reported, as well as absence of reactivation or progression after withdrawal of anti-CMV maintenance treatment. How long this situation will continue is not known and we remain cautious about the future of CMV retinitis and other opportunistic ocular infections.

Catheter complications in AIDS patients treated for cytomegalovirus retinitis

PURPOSE

To describe the complications of central venous catheter use for intravenous therapy of cytomegalovirus (CMV) retinitis in patients with AIDS.

METHODS

Retrospective review of 388 patients with AIDS and CMV retinitis treated with intravenous medications through an indwelling catheter.

RESULTS

The catheter complication rate was 1.2 complications per person-year (0.33 complications per 100 catheter-days). Current injecting drug use increased the risk of infectious complications [hazard ratio (HR), 1.73; P=0.04] whereas former use did not (HR, 0.96; P=0.88). Subdermal port catheters increased the risk of bacteremia (HR, 1.78; P=0.05). Mortality for the first complication was 5.8%. Forty percent of patients required catheter removal, and 86.8% of these patients required reinsertion of another catheter.

CONCLUSIONS

Catheter complications are a substantial problem in patients with CMV retinitis treated with daily intravenous therapy.

Cytomegalovirus retinitis and viral resistance: 3. Culture results. CMV Retinitis and Viral Resistance Study Group

PURPOSE

To evaluate the relationship between blood and urine cultures for cytomegalovirus and clinical outcomes in patients with cytomegalovirus retinitis.

METHODS

Prospective epidemiologic study of 108 patients with newly diagnosed cytomegalovirus retinitis. Blood and urine were cultured for cytomegalovirus at diagnosis of retinitis, at 1 month and 3 months after diagnosis, and every 3 months thereafter.

RESULTS

Of the patients, 80.6% were found to have either a positive blood culture or urine culture for cytomegalovirus at the time of diagnosis of retinitis, and a positive blood culture at diagnosis was associated with an increased mortality (odds ratio = 1.91, P = .012). Follow-up cultures were positive in approximately 20% of patients, and the rate was constant over time. The development of a positive blood or urine culture during follow-up correlated with the occurrence of cytomegalovirus retinitis in the contralateral eye in those patients with unilateral disease at diagnosis (odds ratio = 5.74, P = .001).

CONCLUSIONS

Patients with cytomegalovirus retinitis and positive blood cultures for cytomegalovirus have a poorer prognosis.

Incidence of foscarnet resistance and cidofovir resistance in patients treated for cytomegalovirus retinitis. The Cytomegalovirus Retinitis and Viral Resistance Study Group

Cytomegalovirus (CMV) retinitis is a common opportunistic infection in patients with AIDS. With long-term therapy for CMV retinitis, resistant CMV may develop. In a prospective study of 122 patients with CMV retinitis, 2.4 and 0.8% of patients had foscarnet-resistant blood culture isolates (50% inhibitory concentration [IC50], >400 microM) and urine culture isolates, respectively, at diagnosis of CMV retinitis prior to treatment, whereas 4.1 and 6.6% had cidofovir-resistant (IC50, >2 microM) blood and urine culture isolates, respectively. Patients were treated according to best medical judgement. Of 44 foscarnet-treated patients, 26% had a resistant blood or urine culture isolate by 6 months of treatment and 37% had a resistant isolate by 9 months; of 13 cidofovir-treated patients, 29% had a resistant blood or urine culture isolate by 3 months of therapy. The probabilities of developing foscarnet resistance while on foscarnet and developing cidofovir resistance while on cidofovir were not significantly different from that for developing ganciclovir resistance while on ganciclovir (odds ratios, 1.87 [P = 0.19] and 2.28 [P = 0.15], respectively).

High-dose (2000-microgram) intravitreous ganciclovir in the treatment of cytomegalovirus retinitis

OBJECTIVE

The authors prospectively studied visual outcome, relapse, complications, and survival of patients with acquired immune deficiency syndrome (AIDS)-related cytomegalovirus (CMV) treated with high-dose intravitreous ganciclovir (2 mg/0.1 ml) injections. The outcomes were compared with those of patients treated with standard doses of intravenous ganciclovir in the same institution. The histopathologic and electrophysiologic effects of high-dose intravitreous ganciclovir injections in rabbits also were studied.

DESIGN

A nonrandomized case series.

PARTICIPANTS

A total of 42 patients (74 eyes) were treated with intravitreous injections and 18 patients (27 eyes) were treated with intravenous ganciclovir. Five eyes of three New Zealand white rabbits were injected with ganciclovir, and the sixth eye was a control specimen.

INTERVENTION

Patients treated with intravitreous injections received twice-weekly doses of 2 mg/0.1 ml ganciclovir for 3 weeks, then weekly injections. Patients treated with intravenous ganciclovir received standard doses. Patients were monitored with regular examinations. Rabbit eyes were given intravitreous injections of 1 mg/0.1 ml of ganciclovir weekly for 4 weeks.

MAIN OUTCOME MEASURES

Assessments of vision, retinal inflammation, and survival were made. Electroretinograms were performed on the rabbit eyes, and they were processed for light and electron microscopy.

RESULTS

In the intravitreous group, visual acuity (VA) was stable in 64 of 74 eyes, 5 improved, and 5 deteriorated. Sixty-three (85%) of 74 eyes had final VA of 20/20 to 20/40. Relapse occurred in five eyes (7%; median time, 42 weeks). There were three cases of endophthalmitis. Median survival after diagnosis of CMV retinitis was 36 weeks. In the intravenous group, VA was stable in 18 eyes, 0 improved, and 9 deteriorated. Sixteen (59%) of 27 eyes had final VA of 20/20 to 20/40. Relapse occurred in 15 eyes (56%) at a median time of 21 weeks. Median survival was 21 weeks. The rabbit studies showed no evidence of toxicity.

CONCLUSION

High-dose intravitreous ganciclovir effectively suppressed CMV retinitis, preserved vision, and prevented relapse without deterioration in survival.

Discontinuation of maintenance therapy in patients with quiescent cytomegalovirus retinitis and elevated CD4+ counts

OBJECTIVE

To determine whether maintenance therapy can be discontinued safety in patients with quiescent cytomegalovirus retinitis (CMVR) and increased CD4+ counts after treatment with highly active antiretroviral therapy (HAART).

DESIGN

A prospective observational case series.

PARTICIPANTS

Eight human immunodeficiency virus (HIV)-positive patients with quiescent CMVR who were taking HAART and had CD4+ counts above 100 cells/microliter elected to discontinue anti-CMV maintenance treatment.

INTERVENTION

Biweekly-to-monthly indirect ophthalmoscopy and fundus photographs, monthly-to-quarterly CD4+ counts, and quarterly HIV viral loads were ordered.

MAIN OUTCOME MEASURES

Twelve previously affected eyes were examined for evidence of recurrent retinitis, which was defined as any retinal whitening, border opacification, or expansion of areas of retinal pigment epithelial (RPE) atrophy greater than 750 microns. Four previously unaffected fellow eyes were observed for new CMVR.

RESULTS

There was no reactivation or progression of retinitis in any patient during the mean follow-up interval of 11.4 months (range, 3-16 months). No previously unaffected eye developed CMVR. CD4+ remained elevated in all patients (range, 70-725; mean, 255). The HIV viral load ranged from undetectable to 139,000 copies.

CONCLUSION

Discontinuation of maintenance therapy may be considered in patients with HAART-induced elevated CD4+ counts above 100 cells/microliter, prolonged relapse-free intervals during the reconstitution period before CD4+ counts rise above 100 cells/microliter, and completely quiescent retinitis characterized by RPE scarring only. Reduced risks of drug toxicity and drug-resistant organisms are potential benefits. Close observation for evidence of recurrent retinitis is indicated.

Increasing survival in AIDS patients with cytomegalovirus retinitis treated with combination antiretroviral therapy including HIV protease inhibitors

OBJECTIVE

To assess the effect of combination antiretroviral therapy including HIV protease inhibitors on the survival of patients with cytomegalovirus retinitis (CMVR).

DESIGN AND PARTICIPANTS

A longitudinal study of patients with CMVR diagnosed between October 1992 and May 1996 and followed to May 1997.

SETTING

UK National Health Service specialist HIV medicine department.

OUTCOME MEASURE

Time to death from first diagnosis of CMVR. Data were censored on 31 May 1997.

RESULTS

Data were available on 147 patients with CMVR. Median survival of CMVR patients before December 1995 was 256 days [95% confidence interval (CI), 197-315]. Following the introduction of protease inhibitors in December 1995 this rose to 555 days (95% CI, 351-759). By 31 May 1996 median survival for the entire group of patients alive with CMVR had risen to 720 days (95% CI, 551-889). The mean survival after CMVR diagnosis was 224 days (n=89; 95% CI, 186-261; 1-year survival, 16%) in those who took no further antiretroviral therapy, 353 days in those who took nucleoside reverse transcriptase inhibitors but no protease inhibitors (n=34; 95% CI, 289-418; 1 -year survival, 50%), and 914 days in those who took a protease inhibitor (n=24; 95% CI, 768-1059; 1-year survival, 83%; P < 0.0001). Multivariate analysis showed that the strongest independent predictor of improved survival was having ever received a protease inhibitor after CMVR (relative risk of death, 0.063; 95% CI, 0.027-0.149; P < 0.0001).

CONCLUSIONS

The use of HIV protease inhibitors in combination antiretroviral therapy has been associated with a marked increase in the survival of patients with CMVR.

Anterior uveitis and hypotony after intravenous cidofovir for the treatment of cytomegalovirus retinitis

OBJECTIVE

This study aimed to describe the incidence and risk factors for the development of anterior uveitis in patients receiving intravenous cidofovir for the treatment of longstanding cytomegalovirus retinitis.

DESIGN

The study design was a retrospective cohort.

PARTICIPANTS

Eighteen patients (30 eyes) receiving parenteral cidofovir for the treatment of complicated cytomegalovirus retinitis participated.

MAIN OUTCOME MEASURES

The clinical response to parenteral cidofovir; the occurrence of anterior uveitis, and the management and outcome of patients with this complication; and the effect of cidofovir on intraocular pressure measurements were measured.

RESULTS

There was no progression or relapse of retinitis in patients receiving intravenous cidofovir. Eight (44%) of the 18 patients developed anterior uveitis, which occurred after a median of 4 doses of intravenous cidofovir. The median CD4+ cell count at the time of development of iritis was 101/mm3. Patients who developed uveitis had a mean increase in serum creatinine over baseline measurements (P = 0.05). The use of human immunodeficiency virus type-1 (HIV-1) protease inhibitors was not different between both groups of patients (P = 1.0). The development of anterior uveitis and visually significant hypotony necessitated withdrawal of cidofovir in only one patient.

CONCLUSIONS

Anterior uveitis was a common complication after intravenous cidofovir therapy. Despite the frequency of this complication, continued treatment with intravenous cidofovir was possible in the majority of patients. Patients with anterior uveitis after intravenous cidofovir may be treated successfully with topical corticosteroid therapy and cycloplegic agents.

Chronic multifocal retinal infiltrates in patients infected with human immunodeficiency virus

PURPOSE

To describe the clinical features of a disorder characterized by chronic multifocal retinal infiltrates and uveitis in individuals with human immunodeficiency virus (HIV) disease.

METHODS

We reviewed the medical records of HIV-infected patients with multifocal retinal infiltrates of unknown cause seen by investigators at four institutions. The following data were collected: demographic characteristics, presenting signs and symptoms, laboratory test results, and course of disease.

RESULTS

We identified 26 HIV-infected patients (50 involved eyes) with this syndrome. Median CD4+ T-lymphocyte count at presentation was 272 per microl (range, 7 to 2,118 per microl). The most common presenting symptom was floaters. Median visual acuity of involved eyes at presentation was 20/20 (range, 20/15 to 20/100) and remained stable (median, 20/20; range, 20/15 to 20/70) after a median follow-up period of 9 months (range, 0 to 110 months). Typical retinal lesions were gray-white or yellow, irregular in shape, and less than 200 microm in greatest dimension. All were located in the midperiphery or anterior retina and enlarged slowly or remained static in size. Mild to moderate anterior chamber or vitreous humor inflammatory cells were present in 47 of 50 eyes (26 of 26 patients). Retinal lesions possibly responded to zidovudine but not to acyclovir or ganciclovir. Anterior chamber and vitreous humor inflammatory reactions responded to topical or periocular injections of corticosteroid.

CONCLUSIONS

Uveitis with chronic multifocal retinal infiltrates is a distinct clinical entity of unknown cause that occurs in HIV-infected patients. Retinal lesions may respond to antiretroviral therapy. Visual prognosis is good.

Pharmacokinetics and absolute bioavailability of oral foscarnet in human immunodeficiency virus-seropositive patients

The pharmacokinetics, absolute bioavailability, accumulation, and tolerability over 8 days of an oral formulation of foscarnet (90 mg/kg of body weight once daily [QD] [n = 6], 90 mg/kg twice daily [BID] [n = 6], and 180 mg/kg QD [n = 31) were investigated in 15 asymptomatic, human immunodeficiency virus-seropositive male patients free of active cytomegalovirus infection and with normal upper gastrointestinal function. Peak plasma drug concentrations were (mean +/- standard deviation) 46.4 +/- 10.8 microM (90 mg/kg QD), 45.7 +/- 6.9 microM (90 mg/ kg BID), and 64.9 +/- 31.7 microM (180 mg/kg QD) on day 1 and rose to 86.2 +/- 35.8, 78.7 +/- 35.2, and 86.4 +/- 25.0 microM, respectively, on day 8. The mean peak concentration in plasma following the intravenous administration of foscarnet (90 mg/kg) was 887.3 +/- 102.7 microM (n = 13). The terminal half-life in plasma remained unchanged, averaging 5.5 +/- 2.2 h on day 1 (n = 15) and 6.6 +/- 1.9 h on day 8 (n = 13), whereas it was 5.7 +/- 0.7 h following intravenous dosing. Oral bioavailabilities were 9.1% +/- 2.2% (90 mg/kg QD), 9.5% +/- 1.7% (90 mg/kg BID), and 7.6% +/- 3.7% (180 mg/kg QD); the accumulation ratios on the 8th day of dosing were 2.1 +/- 1.1, 1.8 +/- 0.4, and 1.7 +/- 0.7, respectively. The overall 24-h urinary excretion of oral foscarnet averaged 7.8% +/- 2.6% (day 1) and 13.4% +/- 6.0% (day 8), whereas it was 95.0% +/- 4.9% after intravenous dosing. The glomerular filtration rate and creatinine clearance remained constant, and the mean 24-h renal clearances of foscarnet for the entire study group were 96 +/- 18 ml/min (day 1), 88 +/- 13 ml/min (day 8), and 103 +/- 16 ml/min after intravenous dosing. Adverse effects were largely confined to gastrointestinal disturbances, with all subjects experiencing diarrhea that was dose dependent in its severity. The results suggest that the formulation studied would require significant improvement with respect to tolerability and bioavailability to gain clinical acceptance.

Plasma cytomegalovirus (CMV) DNA load predicts CMV disease and survival in AIDS patients

In this study, baseline plasma from 619 persons with acquired immunodeficiency syndrome (AIDS) (median CD4+ lymphocyte count -21/microl) who participated in a trial to determine the efficacy of oral ganciclovir for cytomegalovirus (CMV) disease prevention were evaluated for CMV DNA load by qualitative and quantitative polymerase chain reaction (PCR), and correlated with the development of CMV disease and survival. For participants without detectable plasma CMV DNA, the 12-mo Kaplan-Meier CMV disease event rate was 14% and 1% for the placebo and ganciclovir groups, respectively (P < 0.001). For PCR positive participants, CMV disease developed in 43% of placebo and 26% ganciclovir recipients (P < 0.017). Among placebo recipients, CMV PCR positivity was associated with a 3.4-fold increased risk of developing CMV disease (P < 0.001) whereas CD4+ lymphocyte count was not a useful predictor (P = 0.47). A positive plasma CMV DNA PCR was also associated with a 2.5-fold increased risk of death. Each log10 increase in baseline CMV DNA load was associated with a 3.1-fold increase in CMV disease (P < 0.001) and a 2.2-fold increase in mortality (P < 0.001). These data indicate that the risk of developing CMV disease and death in persons with advanced AIDS is directly related to the quantity of CMV DNA in plasma, and is a better predictor than CD4+ lymphocyte count in this population.

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.