Efficacy of Amphotericin B at Suboptimal Dose Combined with Voriconazole in a Murine Model of Aspergillus fumigatus Infection with Poor In Vivo Response to the Azole

[Combination antifungal therapy for invasive fungal disease in children with hematologic disease]

OBJECTIVE

To evaluate antifungal combination strategy in children with hematologic diseases and invasive fungal disease( IFD).

METHODS

A retrospective clinical study was performed based on 67 childhood patients with hematologic diseases and IFD who firstly accepted combination antifungal therapy for ≥ 7 days during January 2012 and December 2014. Of them, 11 cases received combination of echinocandin with azole, 10 cases received combination of echinocandin with amphotericin B, and 46 cases received combination of azole with amphotericin B.

RESULTS

Overall response rate was 79.1%. Univariate analysis revealed that granulocyte recovery (P=0.031), status of underling disease (P=0.023) and the duration of the therapy (P=0.046) were significantly associated with efficacy. Multivariate analysis showed that the independent prognostic factor was the duration of combination antifungal therapy (OR=0.229, 95% CI 0.061- 0.863, P=0.029). The response rates of echinocandin combined with azole, echinocandin combined with amphotericin B and azole combined with amphotericin B were 81.8%, 60.0% and 82.6%, respectively (P>0.05), and 12-week survival rates were 81.8%, 80.0% and 86.5%, respectively (P>0.05). The drug- related adverse reactions occurred 59 times in 34 patients. BUN increasing, hypokalemia and abnormal liver functions were considered the main side effects.

CONCLUSION

For IFD in children with hematologic disease, to extend the duration of treatment (≥ 14 days) could significantly improve the curative effect. Combinations of echinocandin with azole, echinocandin with amphotericin B and azole with amphotericin B can be used as a combination treatment options. Combination of Azole with amphotericin B is efficacious, safe and economic treatment option considering efficacy, survival rate, cost and dosage form.

In Vivo Synergy of Amphotericin B plus Posaconazole in Murine Aspergillosis

Aspergillus fumigatus is the main mold causing invasive fungal infection that shows high mortality rates. Therapeutic failure and the increase in drug resistance make it necessary to explore alternative treatments for this infection. We have evaluated the efficacy of amphotericin B at 0.8 mg/kg or 0.3 mg/kg of body weight combined with 40 mg/kg of posaconazole against three A. fumigatus isolates in a murine model of disseminated infection. The combination of the polyene and the azole led to a greater increase in survival and a significantly greater reduction in tissue burden than monotherapies.

Optimization of polyene-azole combination therapy against aspergillosis using an in vitro pharmacokinetic-pharmacodynamic model

Although amphotericin B-azole combination therapy has traditionally been questioned due to potential antagonistic interactions, it is often used successfully to treat refractory invasive aspergillosis. So far, pharmacodynamic (PD) interactions have been assessed with conventional in vitro tests, which do not mimic human serum concentrations and animal models using limited doses. We therefore simulated the human serum concentration profiles of amphotericin B and voriconazole in an in vitro dialysis/diffusion closed pharmacokinetic-pharmacodynamic (PK-PD) model and studied the pharmacodynamic interactions against an azole-resistant and an azole-susceptible Aspergillus fumigatus isolate, using Bliss independence and canonical mixture response surface analyses. Amphotericin B dosing regimens with the drug administered every 24 h (q24h) were combined with voriconazole q12h dosing regimens. In vitro PK-PD combination data were then combined with human PK data by using Monte Carlo analysis. The target attainment rate and the serum concentration/MIC ratio were calculated for isolates with different MICs. Synergy (20 to 31%) was observed at low amphotericin B-high voriconazole exposures, whereas antagonism (-6 to -16%) was found at high amphotericin B-low voriconazole exposures for both isolates. Combination therapy resulted in 17 to 48% higher target attainment rates than those of monotherapy regimens for isolates with voriconazole/amphotericin B MICs of 1 to 4 mg/liter. Optimal activity was found for combination regimens with a 1.1 total minimum concentration of drug in serum (tCmin)/MIC ratio for voriconazole and a 0.5 total maximum concentration of drug in serum (tCmax)/MIC ratio for amphotericin B, whereas the equally effective monotherapy regimens required a voriconazole tCmin/MIC ratio of 1.8 and an amphotericin B tCmax/MIC ratio of 2.8. Amphotericin B-voriconazole combination regimens were more effective than monotherapy regimens. Therapeutic drug monitoring can be employed to optimize antifungal combination therapy with low-dose (≤0.6 mg/kg) amphotericin B-based combination regimens against resistant isolates for minimal toxicity.

Successful treatment of Paecilomyces variotii peritonitis in a liver transplant patient

Paecilomyces variotii has previously been reported as a causative pathogen for peritonitis in patients on continuous ambulatory peritoneal dialysis and shown to be usually sensitive to amphotericin B and resistant to voriconazole. We report the first case, to our knowledge, of P. variotii peritonitis in a liver transplant patient, which was unresponsive to initial liposomal amphotericin B (L-AmB) treatment and resolved dramatically after the addition of voriconazole. The present case provides evidence for the clinical and microbiological effectiveness of voriconazole combined with L-AmB in treating P. variotii peritonitis refractory to initial L-AmB treatment.

In vitro combination of voriconazole and miltefosine against clinically relevant molds

Invasive infections caused by filamentous fungi are a major threat for immunocompromised patients. Innate/acquired resistance to antifungal drugs might necessitate combination therapies. We assessed the potential combination of voriconazole with miltefosine, an original drug with antifungal activity against 33 clinically relevant mold isolates, including both azole-susceptible and -resistant Aspergillus. Using complete inhibition as an endpoint, interactions were indifferent for 32/33 isolates. An alternative 50% inhibition endpoint showed synergistic interactions for 14/33 isolates. Antagonism was absent.