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

Continuous High-Dose (6 mg) vs. Low-Dose (3 mg) Intravitreal Ganciclovir for Cytomegalovirus Retinitis After Haploidentical Hematopoietic Stem Cell Transplantation: A Randomized Controlled Study

Purpose: To evaluate the safety and efficacy of continuous high-dose (6 mg) intravitreal ganciclovir injections (IVG) for cytomegalovirus (CMV) retinitis (CMVR) after haploidentical hematopoietic stem cell transplantation (Haplo-HSCT), and to explore factors that may influence the treatment procedure.

Design: Prospective, randomized, single-blinded, positive-controlled, interventional, comparative study.

Methods: A total of 22 patients with CMVR (32 eyes) were randomized to either high-dose group (IVG 6 mg weekly) or low-dose group (IVG 3 mg given twice weekly for 2 weeks as induction phase and weekly thereafter as maintenance phase). Patients who were recorded any positive CMV DNAemia or other active CMV diseases and needed systemic anti-CMV treatment during the study period were excluded. The vision outcome, variables of the treatment procedure, and incidence of complication and CMVR recurrence were analyzed and compared. Logistic regression was applied to determine the factors that may have an impact on the treatment process at baseline.

Results: Compared to the low-dose group, the high-dose group resulted in a median of two less intravitreal injections (4 vs. 6 times, respectively, P = 0.016), while the rate of vision stability or improvement (81.2 vs. 87.5%), the incidence of complication (6.2 vs. 18.8%), and CMVR recurrence (12.5% vs. 6.2%) were similar (all P > 0.05). No drug-related toxicity was observed. Initial aqueous CMV-DNA load (OR: 6.872, 95% CI: 1.335–35.377, P = 0.021) and extension of lesion (OR: 0.942, 95% CI: 0.897 to .991, P = 0.020), but not dosing regimen (P = 0.162), were predictors of the treatment duration.

Conclusions: Continuous high-dose regimen was well tolerated and resulted in less intravitreal injections, with similar vision outcomes and safety profiles. The clinical course of CMVR after Haplo-HSCT was determined by its own nature at baseline and could not be modified by treatment protocols under consistent immune background.

Management of Intraocular Infections in HIV

Purpose: Overview of treatment options for the most common intraocular opportunistic infections in patients with acquired immunodeficiency syndrome (AIDS), including ocular syphilis, ocular tuberculosis, toxoplasmic chorioretinitis, and viral retinitis. Method: Narrative Review. Results: Despite the huge advances in the development of combined antiretroviral therapy (cART) for the management of patients with human immunodeficiency virus (HIV) infection, opportunistic infections still represent a significant diagnostic dilemma and cause of ocular morbidity in patients with HIV. Conclusion: Although the treatment of intraocular infections in patients with AIDS may be challenging, prompt assessment of the clinical features and appropriate aggressive management of the underlying etiology are critical to avoid life and vision threatening.

Virus-Induced Anterior Uveitis (VIAU) in Immunocompromised Patients

PURPOSE

To describe the clinical characteristics, diagnosis, and treatment of VIAU in immunocompromised patients.

METHODS

A critical review of literature was performed.

RESULTS

Diagnosis and treatment of VIAU in immunocompromised patients may be a challenge due to atypical clinical-courses, severe presentations, and more frequent recurrences. A conclusive diagnosis can be made by aqueous-humour PCR-analysis. Visual prognosis depends on early diagnosis and prompt treatment. Frequent ocular examinations are recommended in HIV patients with CD-4-counts below 100 in order to rule out opportunistic ocular coinfections. It is essential to bear in mind the potential side-effects of therapeutic interventions and consider the possibility of Immune Recovery Uveitis (IRU) in eyes with treated viral retinitis after the initiation of HAART.

CONCLUSIONS

Early diagnosis and treatment of VIAU in immunocompromised patients can be achieved with high suspicion, recognizing clinical features, and obtaining specimens for molecular diagnostic testing in order to avoid usually severe ocular morbidity.

Evolution of Intravitreal Therapy for Retinal Diseases-From CMV to CNV: The LXXIV Edward Jackson Memorial Lecture

PURPOSE

To present the evolution of intravitreal therapy for retinal diseases and its impact on clinical practice.

DESIGN

Retrospective literature review and personal perspective.

METHODS

Retrospective literature review and personal perspective.

RESULTS

Pharmacotherapeutic advances in retinal disease have been remarkable over the last 25 years. Almost all of the new drugs developed have required intravitreal administration to be highly effective, leading to an exponential increase in the annual number of intravitreal injections given. The use of intravitreal antibiotic injections to treat endophthalmitis, usually on a one-time basis, first familiarized ophthalmologists with this method of drug delivery. Ganciclovir was the first widely available, relatively inexpensive compounded drug that was used for repeat intravitreal injection to treat a chronic retinal disease, followed by triamcinolone for diabetic macular edema and bevacizumab for neovascular age-related macular degeneration. Ganciclovir was formulated for sustained-release drug delivery to avoid frequent intravitreal injections, a goal that has been more elusive for anti-VEGF drugs. Political obstacles encountered while conducting some of the trials to evaluate these treatments were substantial. Addressing the issues they raised led to important national policy changes that will impact the conduct of future clinical trials. The first comparative efficacy trial of intravitreal therapies was the Comparison of AMD Treatments Trials (CATT). The primary results from CATT and the many publications that followed continue to shape the use of intravitreal therapy today.

CONCLUSION

Intravitreal therapy has proven highly effective for the treatment of many retinal diseases. The treatment burden for patients from numerous injections, the cost to health care systems, and the impact on workflows in clinical practice have been substantial. Efforts to develop effective intravitreal therapies with reduced treatment burden and cost are ongoing.

High-dose (5000-μg) Intravitreal Ganciclovir Combined with Highly Active Antiretroviral Therapy for Cytomegalovirus Retinitis in HIV-Infected Patients in Venezuela

Purpose

To describe the use of high doses of intravitreal ganciclovir combined with highly active antiretroviral therapy (HAART) for the treatment of cytomegalovirus (CMV) retinitis in human immunodeficiency virus (HIV)-infected patients.

Methods

Thirteen HIV-infected patients (18 eyes) with active CMV retinitis (83.3% in zone 1 and 38.4% resistant) participated in this prospective interventional case series. Patients were treated with high dose intravitreal ganciclovir (5.0 mg/0.1 mL once a week) in combination with HAART therapy. Intravitreal injections were discontinued once CMV retinitis healed if there was a significant increase in CD4+ count (any increase of ≥50 cells/μL to levels over 100 cells/μL sustained for at least 3 months). Mean follow-up was 15.6 months. Main outcome measures included assessment of visual acuity and retinal inflammation (CMV retinitis activity). A matched historical control group of 20 eyes (15 patients) with CMV retinitis treated with systemic ganciclovir (intravenous [induction] and oral [maintenance]) was included.

Results

Complete regression of the retinitis was obtained with high doses of intravitreal ganciclovir in 88.8% of eyes (two patients died during follow-up) at a mean of 4.5 weeks (2 to 8 weeks). Visual acuity improved two or more lines in 61.1% of eyes. No ganciclovir retinal toxicity was identified. Three eyes presented CMV retinitis reactivation at a mean of 25.6 days after their last injection. Complications (33.3%) included retinal detachment (RD; 3 eyes), immune recovery uveitis (IRU; 2 eyes), and endophthalmitis (1 eye). In our control group complete regression of the retinitis was obtained in 100% of eyes at a mean of 4 weeks (3 to 7 weeks). However, 12 eyes (60%) presented with CMV retinitis relapse at a mean of 29 days (21 to 32 days) after initiating oral ganciclovir (maintenance). Complications included RD (7 eyes, 35%) and IRU (3 eyes, 15%). Severe neutropenia occurred in 2 patients (13%).

Conclusions

High doses of intravitreal ganciclovir (5.0 mg) once a week in combination with HAART therapy is effective to control CMV retinitis, and may be discontinued after CMV retinitis has healed if immune reconstitution with a significant increase in CD4+ count has occurred.

High ocular CMV copies and mismatched receipts may predict poor visual prognosis in CMV retinitis patients following allogeneic haematopoietic stem cell transplantation

BACKGROUND

To summarize the clinical characteristics and potential factors affecting the visual outcomes in patients with cytomegalovirus retinitis following allogeneic haematopoietic stem cell transplantation (HSCT).

METHODS

This retrospective study enrolled 12 patients (19 eyes) with cytomegalovirus retinitis after HSCT at Guangzhou First People's Hospital in China between January 2013 and December 2014. Demographic and clinical characteristics, ocular manifestations and visual outcomes were evaluated by reviewing medical records at the Departments of Hematology and Ophthalmology. All patients were followed up at least 6 months after stopping antiviral therapy. The visual outcome was defined as improvement, stabilization and deterioration.

RESULTS

The subjects were composed of 7 human leucocyte antigen-matched and 5 mismatched receipts. All patients received combined systemic and intravitreous antiviral therapy. Eleven eyes gained improved or stabilized visual acuity, while 8 eyes suffered deterioration. Eyes with cytomegalovirus load less than 1 × 10⁴ copies/ml in vitreous accounted for higher rate in eyes with good visual prognosis than those with cytomegalovirus copies above 1 × 10⁴ copies/ml (52.63% vs 5.26%, P < 0.001). Human leucocyte antigen-matched receipts gained better visual prognosis than those mismatched ones (47.37% vs10.53%, P < 0.05). The virus types, cytomegalovirus peak in the blood, involved retinal zone and size had no influence on the visual outcomes (all P > 0.05).

CONCLUSIONS

High ocular cytomegalovirus copies and mismatched receipts may be potential adverse factors affecting visual outcomes in cytomegalovirus retinitis patients following allogeneic HSCT.

Treatment outcomes of reduced-dose intravitreal ganciclovir for cytomegalovirus retinitis

Background

Cytomegalovirus retinitis (CMVR) is one of the most common opportunistic infection in immunocompromised individuals. Intravitreal ganciclovir injection has been used successfully but no standard regimen was established. Risks of drug toxicity, endophthalmitis, and injection-related complications increased with number and frequency of injection. The aim of this study is to evaluate the outcomes of reduced-dose intravitreal ganciclovir (2 mg/0.04 mL) for the treatment of CMVR.

Methods

A prospective observational cohort study involving 67 eyes of 49 patients with CMVR was performed. Induction therapy involved intravenous ganciclovir (10 mg/kg/day) for 2 weeks unless contraindicated or patients refused. Patients were then treated with reduced-dose intravitreal ganciclovir every week for 4 weeks, and then every other week until the lesion healed. The patients’ demographic data were recorded, and vision parameters were examined every visit.

Results

Twenty eyes (29.9 %) presented with initial visual acuities less than 6/60. The majority of patients were diagnosed with CMVR in zones 1 or 2 (63 eyes, 94 %), and, at least, one quadrant of the retina was involved (56 eyes, 83.6 %). Forty-one eyes (61.2 %) completely resolved after treatment within the 6-month follow-up. There was no significant difference in healing time, whether or not patients received induction treatment with intravenous ganciclovir (111.00 ± 12.96 vs 105.00 ± 28.32 days, p = 0.8). Five eyes (12.2 %) of patients with healed CMVR had visual acuities less than 6/60.

Conclusions

Reduced-dose intravitreal ganciclovir is a safe and effective treatment option. It provides comparable results to other weekly regimens. Induction with intravenous ganciclovir is not crucial in a resolution of retinitis, although it may be necessary to reduce systemic cytomegalovirus loads and mortality rates.

Trial registration

The trial was registered with Thai Clinical Trials Registry (TCTR) on 16 March 2016 – TCTR20160316001.

Improved intraocular bioavailability of ganciclovir by mucoadhesive polymer based ocular microspheres: development and simulation process in Wistar rats

BACKGROUND

The poor ocular bioavailability of the conventional eye drops is due to lack of corneal permeability, nasolacrimal drainage and metabolic degradation. To overcome this issue, drug encapsulated in mucoadhesive polymer based ocular microspheres have the advantages of improved drug stability, easy administration in liquid form, diffuse rapidly and better ocular tissue internalization.

METHODS

The ganciclovir chitosan microspheres (GCM) were prepared by modified water-in-oil emulsification method. The formulation was optimized and characterized by investigating in vitro release study, release kinetics, XRD and microspheres stability. Ocular irritancy, in vivo ocular pharmacokinetic parameters and histopathology study was evaluated in Wistar rats. The use of pharmacokinetic/pharmacodynamic indices and simulation process was carried out to further ensure clinical applicability of the formulation.

RESULTS

The in vitro release study showed initial burst (nearly 50 %) in first few minutes and followed Fickian (R(2) = 0.9234, n-value = 0.2329) type of diffusion release mechanism. The XRD and stability studies showed favorable results. The Wistar rat eyes treated with GCM showed significant increase in ganciclovir AUC (~4.99-fold) and Cmax (2.69-fold) in aqueous humor compared to ganciclovir solution and delay in Tmax. The Cmax/MIC90, AUC0-24/MIC90, AUC above MIC90 and T above MIC90 were significantly higher in GCM group. The aqueous humor concentration-time profile of ganciclovir in GCM and ganciclovir solution was simulated with every 28.1 and 12.8 h, respectively. The simulated concentration-time profile shows that in duration of 75 h, the ganciclovir solution require six ocular instillations compared to three ocular instillations of the GCM formulation. The photomicrograph of GCM and ganciclovir solution treated rat retina showed normal organization and cytoarchitecture.

CONCLUSIONS

Correlating with in vitro data, the formulation showed sustained drug release along with improved intraocular bioavailability of ganciclovir in Wistar rats.

Outcome of cytomegalovirus retinitis in immunocompromised patients without Human Immunodeficiency Virus treated with intravitreal ganciclovir injection

PURPOSE

To study the outcomes of treatment with intravitreal ganciclovir injection for cytomegalovirus (CMV) retinitis in patients without Human Immunodeficiency Virus (HIV) infection.

METHODS

In this retrospective cohort study, demographic and clinical characteristics of patients with CMV retinitis without HIV were noted. Patients received intravitreal ganciclovir injection (2 mg/0.1 ml) alone until quiescence. The outcome measures were time taken for the lesions to heal, number of injections, change in best-corrected visual acuity (BCVA), recurrence of retinitis, occurrence of immune recovery uveitis (IRU) or injection-related complications and retinal detachment (RD).

RESULTS

18 eyes of ten patients (six males) with mean age of 33.7 years from June 2004 to March 2013 were included. Thirteen eyes with active lesions (mean BCVA of 0.51 ± 0.41) received 5.54 ± 3.36 intravitreal ganciclovir injections with complete healing within 1.81 ± 1.25 months. The final BCVA was 0.43 ± 0.52. IRU was observed in six eyes (33.33%) and RD developed in one eye. One eye had recurrence 1 month after stopping ganciclovir injections. The rest of the patients had recurrence-free follow-up at 9.46 ± 12.42 months.

CONCLUSIONS

Non-HIV patients with CMV retinitis can be successfully treated with intravitreal ganciclovir injection alone, avoiding the systemic side effects of systemic anti-CMV therapy.

Cytomegalovirus Retinitis in an ALL child on exclusive chemotherapy treated successfully with intravitreal ganciclovir alone

A child suffering from acute lymphoblastic leukemia on treatment with exclusive chemotherapy presented with vision-threatening cytomegalovirus (CMV) retinitis in 1 eye. Prompt diagnosis and treatment with 3 weekly doses of 2 mg/0.1 mL intravitreal ganciclovir resulted in successful healing of CMV retinitis with restoration of visual acuity. In children with acute lymphoblastic leukemia on exclusive chemotherapy without hematopoietic stem cell transplantation, CMV retinitis has been reported in only 1 case in literature. This child was treated successfully with intravenous ganciclovir. This report highlights the use of successful intravitreal ganciclovir in pediatric age group to avoid side effects of systemic ganciclovir.

Intravitreal ganciclovir for neonatal cytomegalovirus-associated retinitis: a case report

Congenital cytomegalovirus (CMV) infection is a major cause of birth defects and childhood disorders in the United States. Retinitis occurs in 25% of infants with severely symptomatic congenital CMV and in ∼1% of asymptomatic infants. Intravitreal ganciclovir is recommended in adults with CMV retinitis (CMVR) refractory or noncompliant to intravenous therapy. No literature is available discussing the use of intravitreal ganciclovir for CMVR in neonates. We report a term neonate who received intravenous and intravitreal ganciclovir for treatment of CMVR. Three doses of intravitreal ganciclovir (2 mg per dose in each eye) were administered. Intravitreal injections of ganciclovir appeared to be well tolerated and improvement of the retinitis was appreciated. Intravitreal ganciclovir is an effective treatment of CMVR in adult acquired immunodeficiency syndrome (AIDS) patients. We report one case of intravitreal ganciclovir in a term neonate with promising results.

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

PURPOSE

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

DESIGN

Literature review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Complications of intravitreal injections

PURPOSE OF REVIEW

Over the past few years, the results of many studies have highlighted the risks and benefits of intravitreal injection of a number of medications, the most common being triamcinolone, antivascular endothelial growth factor (VEGF) agents, antibiotics, antivirals, antifungals, and methotrexate. The purpose of this review is to highlight the complications associated with these injections.

RECENT FINDINGS

Elevated intraocular pressure and glaucoma are the most common complications of intraocular triamcinolone. There is also an increased incidence of cataract formation/progression over time. The immunosuppressive effect of triamcinolone does not appear to increase the risk of endophthalmitis. Recent reports suggest that intravitreal anti-VEGF injections have a low complication rate. Similarly, antimicrobials also have low rates of injection-associated complications.

SUMMARY

Intravitreal injections play a critical role in daily ophthalmic practice. The overall risk of endophthalmitis and retinal detachment appears to be low and most of the commonly used drugs are well tolerated, even with repeat injection. Further long-term studies need to be performed to elucidate ways of increasing the safety of these procedures and medications.

Effect of duration and intensity of ganciclovir exposure on lymphoblastoid cell toxicity

INTRODUCTION

Human cytomegalovirus infection is still a major complication after pediatric bone marrow transplantation and could be fatal in some cases. The toxicity of the drug in dividing transplanted haematopoietic cells combined with the suppression of cell growth caused by the virus remains a major problem in managing human cytomegalovirus infection.

METHODS

The aim of the current in vitro study was to evaluate the effect of the intensity (1-20 mg/l) and duration (1, 2, 7 or 14 days) of ganciclovir exposure on toxicity in B lymphoblastoid cells (using cell counting and viability measurements).

RESULTS

A correlation was found between the dose of ganciclovir exposure and a decrease in total cell number when duration exceeded 2 days (r(2)=0.92 and 0.93 after 7 and 14 days, respectively). High levels (20 mg/l) of ganciclovir were not more toxic than lowest levels (1 mg/l) for the shortest durations of ganciclovir exposure (1 and 2 days). Moreover, 50% cytotoxic concentrations markedly decreased with the duration of ganciclovir exposure (374-3 mg/l from 1 to 14 days respectively) after 14 days of culture.

CONCLUSIONS

This in vitro study demonstrated for the first time that ganciclovir exhibited an in vitro duration-dependent toxicity on haematopoietic-derived cells when in vivo doses of the drug were used.

MINIMIZING THE RISK OF ENDOPHTHALMITIS FOLLOWING INTRAVITREOUS INJECTIONS

PURPOSE

To review techniques that are important in preventing endophthalmitis following intravitreous injections based on the available evidence.

METHODS

A review of the literature regarding existing evidence that is relevant to post-injection endophthalmitis prophylaxis.

RESULTS

The available evidence regarding endophthalmitis prophylaxis is largely based on intraocular surgery, particularly cataract surgery. Despite the controversy and the paucity of evidence regarding endophthalmitis prophylaxis for intravitreous injections, it is recommended that povidone-iodine should be used prior to intravitreous injections to minimize or eliminate the presence of ocular surface bacteria. Administration of topical antibiotics may also be considered before and after the intravitreous injections. Strict adherence to aseptic techniques, including the use of an eyelide speculum is also important.

CONCLUSION

Endophthalmitic can occur following intravitreous injections. Prophylaxis with topical povidone-iodine, and possibly antibiotics, as well as adherence to aseptic technique may minimize the risk of post-injection endophthalmitis.

RISKS OF INTRAVITREOUS INJECTION: A COMPREHENSIVE REVIEW

PURPOSE

To evaluate the prevalence of the most common serious adverse events associated with intravitreous (IVT) injection.

METHODS

A systematic search of the literature via PubMed from 1966 to March 1, 2004, was conducted to identify studies evaluating the safety of IVT injection. Data submitted in New Drug Applications to the U.S. Food and Drug Administration for drugs administered into the vitreous were included where available. Serious adverse events reported in each study were recorded, and risk per eye and risk per injection were calculated for the following serious adverse events: endophthalmitis, retinal detachment, iritis/uveitis, intraocular hemorrhage, ocular hypertension, cataract, and hypotony. Rare complications also were noted.

RESULTS

Data from 14,866 IVT injections in 4,382 eyes were analyzed. There were 38 cases of endophthalmitis (including those reported as pseudoendophthalmitis) for a prevalence of 0.3% per injection and 0.9% per eye. Excluding cases reported specifically as pseudoendophthalmitis, the prevalence of endophthalmitis was 0.2% per injection and 0.5% per eye. Retinal detachment, iritis/uveitis, ocular hypertension, cataract, intraocular hemorrhage, and hypotony were generally associated with IVT injection of specific compounds and were infrequently attributed by the investigators to the injection procedure itself. Retinal vascular occlusions were described rarely in patients after IVT injection, and it was unclear in most cases whether these represented true injection-related complications or chance associations.

CONCLUSION

The risk of serious adverse events reported after IVT injection is low. Nevertheless, careful attention to injection technique and appropriate postinjection monitoring are essential because uncommon injection-related complications may be associated with permanent vision loss.

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

PURPOSE

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

DESIGN

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

PURPOSE

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

DESIGN

Randomized treatment intervention clinical trials.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Intravitreal sustained-release ganciclovir implants for severe bilateral cytomegalovirus retinitis after stem cell transplantation

PURPOSE

To describe the treatment of cytomegalovirus (CMV) retinitis with intravitreal sustain-release ganciclovir devices in a 16-year-old patient in third remission of acute lymphoblastic leukemia after stem cell transplantation.

METHODS

The patient received a stem cell transplant from an unrelated bone marrow donor after which he contracted a serious CMV infection manifested in the lungs and retinae. His immune system at this time was almost completely depleted. Implantation of a sustained-release ganciclovir device was performed in both eyes when retinitis progressed in spite of aggressive antiviral intravenous treatment.

RESULTS

No per- or postoperative complications were noted. Infiltrates, hemorrhages and macular edema present preoperatively dissolved over a period of six months. The final visual acuity was 1.0 in both eyes. The patients immune system and lung function slowly recovered during the same time period.

CONCLUSIONS

The intravitreal ganciclovir implant provides safe and effective therapy against CMV retinitis, and should be considered in patients acquiring the infection after stem cell transplantation.

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

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

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.

Etoposide as a virocidal anticytomegalovirus therapy: intravitreal toxicology and pharmacology in rabbits

BACKGROUND

Although Cytomegalovirus (CMV) retinitis is now a common intraocular infection, current therapy is only virostatic so ongoing treatment is required. Etoposide was found to be virocidal for CMV in laboratory experiments and it might prove to be beneficial clinically. We investigated the toxicity and intraocular concentration of etoposide (VP16) and its new analogue etoposide-phosphate (VP16P) following intravitreal injections in rabbit eyes.

METHODS

First a sequential dose-response was assessed with flash electroretinogram for both eyes of light- and dark-adapted rabbits (n = 7; one rabbit for each dose) over a range of light intensities before and after intravitreal injection of VP16 or VP16P to one eye; the other eye was injected with normal saline as a control. A multidose study was then performed on four rabbits. A non-toxic dose of VP16P (50 or 75 g) was injected into the vitreous of one eye on four occasions 1 week apart. A photopic electroretinogram was performed before the first injection and 6 weeks after the last injection. All the eyes from the electroretinogram studies were fixed in formalin, placed in paraffin, then stained with haematoxylin and eosin and examined under a light microscope. To determine the time-course of the intraocular concentrations of VP16P a sequential pharmacokinetic study was performed using a further 12 rabbits. Each rabbit was injected with 50 g VP16P to one eye and 75 g VP16P to the other eye. Three of these rabbits were killed at 1, 3, 6 and 9 h after injection. Samples of vitreous were assayed for both VP16 and VP16P using HPLC. An in vitro dose response assay was performed using third-passage bovine retinal pigment epithelial (RPE) cells cultured in Dulbecco's modified Eagles medium with fetal calf serum. The effect of a log-dose increment of VP16P on the RPE cell proliferation was assessed using tritiated thymidine incorporation.

RESULTS

The electroretinogram studies suggested that VP16 was toxic even with the 10 g dose. For VP16P a toxic effect was noted following injection of a single dose greater than 100 g. Multiple injections of 50 or 75 g VP16P did not produce a toxic response. Histological examination demonstrated significant abnormality only with the 500 g dose of VP16 or VP16P. VP16P was rapidly metabolized to VP16 in the eye, producing concentrations of 2.0 g/mL or more for up to 9 h following a 75-microg dose. This suggests that the electroretinogram findings following VP16 injections were confounded by a toxic effect of the ethanol solvent (which is absent from the VP16P preparation). VP16P was quite potent, the ID50 was about 0.1 g/mL for bovine RPE cells in the in vitro assay.

DISCUSSION

These results indicate that multiple 75-gVP16P intravitreal injections were not toxic to the rabbit eye and provide a therapeutic intraocular concentration for up to 9 h after the injection.