Combined intravenous ganciclovir and foscarnet for children with recurrent cytomegalovirus retinitis

In vitro combination of anti-cytomegalovirus compounds acting through different targets: role of the slope parameter and insights into mechanisms of Action

Conventional therapy for human cytomegalovirus (CMV) relies on inhibition of the viral DNA polymerase. Ganciclovir (GCV) is the first-line therapy, but when GCV-resistant strains emerge, alternative therapies are extremely limited and are associated with significant toxicities. Combination of anti-CMV agents that act on different targets or stages of virus replication has not been well studied, mostly because of the limited number of anti-CMV agents. We report our investigation of combinations of agents that inhibit CMV by targeting the viral DNA polymerase, cellular kinases, or other cell/virus mechanisms yet to be discovered. The selected compounds differed by the slopes of their dose-response curve: compounds with a slope of 1 (GCV) representing one target or noncooperativity and compounds with high slopes indicating positive cooperativity. Analysis of anti-CMV drug combinations using the Bliss model (which accounts for the slope parameter) distinguished between combinations with synergistic, antagonistic, and additive activities. The combination of GCV and foscarnet was slightly synergistic; strong synergism was found when GCV was used with artemisinin-derived monomers or dimers or the MEK inhibitor U0126. The combination of GCV and cardiac glycosides (digoxin, digitoxin, and ouabain) was additive. The monomeric artemisinin artesunate was synergistic when combined with U0126 or the multikinase inhibitor sunitinib. However, the combination of artemisinin-derived dimers (molecular weights, 606 and 838) and U0126 or sunitinib was antagonistic. These results demonstrate that members of a specific drug class show similar patterns of combination with GCV and that the slope parameter plays an important role in the evaluation of drug combinations. Lastly, antagonism between different classes of CMV inhibitors may assist in target identification and improve the understanding of CMV inhibition by novel compounds.

Antiviral treatment of cytomegalovirus infection and resistant strains

This review discusses the management of resistant cytomegalovirus and prevention strategies for fatal therapy failures. Five drugs, ganciclovir/valganciclovir, cidofovir, foscarnet and fomivirsen, have been approved so far for the treatment of human cytomegalovirus (HCMV) diseases. Except for fomivirsen, all of the approved drugs share the same target molecule, the viral DNA polymerase. The emergence of drug-resistant HCMV has also been reported for all of them. For optimal care of patients, the clinical virologist has to provide the most meaningful assays for monitoring of therapy and early detection of emerging drug-resistant HCMV. Additionally, a quantitative drug monitoring would be helpful. New antiviral agents are urgently needed with less adverse effects, good oral bioavailability and possibly novel targets or mechanisms of action to avoid cross-resistance and to improve the ability to suppress the selection of resistant virus strains by combination therapy. Compounds like maribavir, leflunomide and artesunate, which exhibit anti-HCMV activity in vitro and in patients need to be evaluated in clinical studies. Besides these, new therapy approaches like immunotherapy or new diagnostic techniques like pyrosequencing have to be considered in the future.

Foscarnet therapy for ganciclovir-resistant cytomegalovirus retinitis after stem cell transplantation: effective monitoring of CMV infection by quantitative analysis of CMV mRNA

We report three pediatric patients with ganciclovir-resistant cytomegalovirus (CMV) retinitis who were successfully treated with foscarnet. The patients were recipients of hematopoietic stem cell transplantation (SCT) from HLA-mismatched donors. Because these patients had developed or experienced progressive CMV retinitis during ganciclovir therapy, they received foscarnet therapy at 60 mg/kg every 8 h. Their retinitis resolved promptly after initiating foscarnet therapy, suggesting foscarnet's effectiveness in treating ganciclovir-resistant CMV infection. The amount of CMV mRNA was quantitatively measured using an NASBA technique, which amplified the beta2.7 transcripts specific for CMV replication. This technique was useful for monitoring disease activity in a more rapid and sensitive manner than the PCR assay for CMV DNA.

Cytomegalovirus retinitis in immunosuppressed children

PURPOSE

To describe the ocular and systemic features of children with cytomegalovirus retinitis and their disease outcomes.

METHODS

Review of all cases of cytomegalovirus retinitis diagnosed or treated at a tertiary care pediatric hospital during a 10-year period.

RESULTS

Nine immunocompromised children younger than 16 years were diagnosed as having cytomegalovirus retinitis. The underlying causes of immunocompromise were severe combined immunodeficiency syndrome (n = 2), severe combined immunodeficiency syndrome after bone marrow transplantation (n = 1), acquired immunodeficiency syndrome (AIDS) (n = 2), AIDS and previous bone marrow transplantation for leukemia (n = 1), immunosuppressive therapy after renal transplantation (n = 1), chemotherapy for leukemia (n = 1), and congenital cytomegalovirus infection (n = 1). Five children (56%) had symptomatic extraocular cytomegalovirus infection. Only two children reported visual symptoms with cytomegalovirus retinitis at initial examination. Cytomegalovirus retinitis was bilateral in eight children (89%) and involved the posterior pole in at least one eye of all nine children. Four children (44%) died within 10 months of being diagnosed with cytomegalovirus retinitis. The remaining five children were alive, with follow-up ranging from 14 to 70 months. Successful bone marrow transplantation in one child and discontinuation of immunosuppressive medications in two children improved systemic immune function and permitted discontinuation of anticytomegaloviral therapy.

CONCLUSION

Pediatric cytomegalovirus retinitis is often asymptomatic and bilateral and involves the posterior pole at initial examination. Recovery of systemic immune function may occur in some children. Evaluation of children at risk and prompt treatment of cytomegalo. virus retinitis are important to prevent long-term visual morbidity.

Cytomegalovirus infection after intestinal transplantation in children

Sixteen episodes of cytomegalovirus (CMV) disease occurred in 10 of 41 children undergoing intestinal transplantation from 1990 to 1995. Stratification of CMV disease by donor (D)/recipient (R) serological status was as follows: 3 of 8, D+/R-; 3 of 9, D+/R+; 4 of 9, D-/R+; and 0 of 15, D-/R-. Treatment resulted in resolution of CMV disease in 93.3% of episodes. No deaths attributable to CMV disease occurred in this series. CMV in D+/R- children resulted in more extensive and persistent disease. However, patient and graft survival rates were similar in the different D/R subgroups and between children with and without CMV disease. Cumulative dose of steroid boluses (relative risk [RR], 1.59; 95% confidence interval [CI], 1.14-2.21) and history of steroid recycles (RR, 2.72; 95% CI, 1.21-6.13) were associated with CMV disease. These results suggest that although CMV-associated morbidity in pediatric intestinal transplant recipients was substantial, it was not associated with an increased rate of mortality or graft loss, even among high-risk D+/R- patients.

Treatment of bilateral cytomegalovirus retinitis with sustained-release ganciclovir implants in a child

PURPOSE

To report treatment of bilateral cytomegalovirus (CMV) retinitis in an 11-year-old girl with acquired immunodeficiency syndrome (AIDS).

METHOD

Case report describing the use of intravitreal ganciclovir sustained-release devices to treat CMV retinitis, involving zones 1 through 3, which progressed despite single and combination intravenous therapy with ganciclovir and foscarnet.

RESULTS

Stabilization with no active CMV retinitis was achieved after bilateral implantation of intravitreal sustained-release ganciclovir devices. There was no reactivation of the retinitis during the 5 months of follow-up.

CONCLUSION

Sustained-release ganciclovir implants can be used to achieve local control of CMV retinitis in the pediatric patient.