A Review of Population Pharmacokinetic Models of Posaconazole

Posaconazole is often used for the prophylaxis and treatment of invasive fungal infections (IFI). However, intra- and inter-individual differences and drug interactions affect the efficacy and safety of posaconazole. Precision dosing of posaconazole based on the population pharmacokinetic (PopPK) model may assist in making significant clinical decisions. This review aimed to comprehensively summarize the published PopPK models of posaconazole and analyze covariates that significantly influence posaconazole exposure. Articles published until May 2022 for PopPK analysis of posaconazole were searched in PubMed and EMBASE databases. Demographic characteristics, model characteristics, and results of PopPK analysis were extracted from the selected articles. In addition, the steady-state pharmacokinetic profiles of posaconazole were simulated at different covariate levels and dosing regimens. Out of the 13 studies included in our review, nine studies included adults, three included children, and one included both adults and children. All oral administration models were one-compartment models, and all intravenous administration models were two-compartment models. Body weight, proton pump inhibitors, and incidence of diarrhea were found to be important covariates. Clinically, the potential impact of factors such as patient physiopathologic characteristics and comorbid medications on posaconazole pharmacokinetics should be considered. Dose adjustment in combination with TDM or replacement with a tablet or intravenous formulation with higher exposure may be an effective way to ensure drug efficacy as well as to reduce fungal resistance. Meanwhile, published models require further external evaluation to examine extrapolation.

Epidemiology, clinical features, therapeutic interventions and outcomes of mucormycosis in Shiraz: an 8-year retrospective case study with comparison between children and adults

Mucormycosis is an invasive fungal infection with high morbidity and mortality rate despite the early diagnosis and proper therapeutic interventions. Given the importance of epidemiological data in reviewing the attitude toward infectious diseases in developing countries, the current retrospective case study aimed to compare the epidemiological aspects, risk factors, clinical characteristics, therapeutic interventions, and outcomes of mucormycosis between adults and children during eight years (2013-2021) in the main infectious disease referral centers in the southwest of Iran. The median age of 164 patients included in this study was 47 years (IQR 22-59). The median length of hospitalization was 33 days.The annual incidence of mucormycosis-related hospitalizations was estimated 1.76 per 10,000 admissions during the study period. Moreover, the incidence of infection was 2.4 times higher in males than females in children. Diabetes mellitus was the most frequent predisposing factor in adults (46.0%). The main risk factor in children was hematologic malignancy (52.6%), but a considerable proportion of them (28.9%) were immunocompetent.The most frequent antifungal agent used was liposomal amphotericin B (82.3%) as monotherapy. The combination therapy was used more in adults (15.8%) than children (7.9%). In addition, surgical intervention with antifungal therapy was considered the most effective therapeutic approach. The in-hospital mortality rate was 14.6% for adults, whereas it was zero for children. Our findings provide a recent epidemiologic analysis of mucormycosis among hospitalized patients in both children and adults. Mucormycosis mainly affects individuals with diabetes mellitus or hematological malignancies and presents as rhino-orbito-cerebral form. Proven diagnosis of mucormycosis according to clinical manifestations and histopathology observations accompanied by proper antifungal treatments may improve survival rates.

Dental and Oral Manifestations of COVID-19 Related Mucormycosis: Diagnoses, Management Strategies and Outcomes

It has been nearly two years since the pandemic caused by the novel coronavirus disease (COVID-19) has affected the world. Several innovations and discoveries related to COVID-19 are surfacing every day and new problems associated with the COVID-19 virus are also coming to light. A similar situation is with the emergence of deep invasive fungal infections associated with severe acute respiratory syndrome 2 (SARS-CoV-2). Recent literature reported the cases of pulmonary and rhino-cerebral fungal infections appearing in patients previously infected by COVID-19. Histopathological analysis of these cases has shown that most of such infections are diagnosed as mucormycosis or aspergillosis. Rhino-orbital-cerebral mucormycosis usually affects the maxillary sinus with involvement of maxillary teeth, orbits, and ethmoidal sinuses. Diabetes mellitus is an independent risk factor for both COVID-19 as well as mucormycosis. At this point, there is scanty data on the subject and most of the published literature comprises of either case reports or case series with no long-term data available. The aim of this review paper is to present the characteristics of COVID-19 related mucormycosis and associated clinical features, outcome, diagnostic and management strategies. A prompt diagnosis and aggressive treatment planning can surely benefit these patients.

Real-world assessment of the effectiveness of posaconazole for the prophylaxis and treatment of invasive fungal infections in hematological patients: A retrospective observational study

The aim of the study was to analyze the efficacy of posaconazole for the prophylaxis and treatment of invasive fungal diseases (IFDs) in patients with hematological malignancies.In this retrospective observational multi-center study, 762 patients from 25 Chinese hematological centers were enrolled. Inclusion criteria were patients with hematological malignancy or they had undergone hematopoietic stem cell transplantation and received at least 1 dose of posaconazole. The primary endpoints were the observation of breakthrough rates and the clinical efficacy of posaconazole prophylaxis. The secondary endpoint was the efficacy of posaconazole for the treatment of IFDs.Of the 762 enrolled patients, 456 (59.8%) were prescribed posaconazole prophylactically while 243 (31.9%) received posaconazole as an IFD treatment (12 proven, 61 probable, 109 possible, and 61 unclassified IFD cases) for ≥7 days. The overall IFD breakthrough rate (probable cases) for the ≥4 days prophylactic treatment (n = 445) group was 1.6% (95% Cl: 0.6%-3.2%), with breakthrough rates of 2.6% for acute myeloid leukemia/myelodysplastic syndrome patients undergoing chemotherapy and 2.2% for hematopoietic stem cell transplantation patients. For primary antifungal prophylaxis, the breakthrough rate was 1.9% and for secondary antifungal prophylaxis 0%. The overall effective IFD remission rate of patients treated for ≥7 days with posaconazole was 56.0% and the effective remission rate of proven/probable/possible IFD cases was 59.3%. The effective remission rate of posaconazole as salvage therapy was 50% (95% CI: 32.4%-67.6%) including 75% (CI: 19.4%-99.4%) for Aspergillus infections.The present retrospective study confirmed posaconazole as IFD prophylaxis and medication for hematological malignancy patients undergoing various treatments in China.

Posaconazole Serum Drug Levels Associated With Pseudohyperaldosteronism

BACKGROUND

Posaconazole tablets are well tolerated and efficacious in the prophylaxis and treatment of aspergillosis, mucormycosis, and other invasive fungal infections. There have been case reports of posaconazole-induced pseudohyperaldosteronism (PIPH); however, its occurrence and association with serum posaconazole drug levels have not previously been investigated.

METHODS

In this single-center, retrospective, observational study, we examined the occurrence of PIPH in outpatients newly starting posaconazole and evaluated differences in serum posaconazole concentrations and clinical characteristics between those with and without this syndrome.

RESULTS

Sixty-nine patients receiving posaconazole were included, of whom 16 (23.2%) met the definition of PIPH. Patients with PIPH were significantly older (61.1 vs 44.7 years, P = .007) and more frequently had hypertension prior to starting posaconazole (68.8% vs 32.1%, P = .009). Patients with PIPH had a significantly higher median serum posaconazole level than those without PIPH (3.0 vs 1.2 µg/mL, P ≤ .0001). There was a positive correlation between serum posaconazole levels and changes in systolic blood pressure (r = .37, P = .01), a negative correlation between serum posaconazole levels and changes in serum potassium (r = -.39, P = .006), and a positive correlation between serum posaconazole levels and serum 11-deoxycortisol (r = .69, P < .0001).

CONCLUSIONS

Posaconazole is associated with secondary hypertension and hypokalemia, consistent with pseudohyperaldosteronism, and development is associated with higher serum posaconazole concentrations, older age, and baseline hypertension.

Efficacy and safety of posaconazole for the prevention of invasive fungal infections in immunocompromised patients: a systematic review with meta-analysis and trial sequential analysis

Invasive fungal infections are a potentially life-threatening complication in immunocompromised patients. The aim of this study was to assess the efficacy and safety of posaconazole as compared with other antifungal agents for preventing invasive fungal infections in immunocompromised patients. Embase, CENTRAL, and MEDLINE were searched for randomized conweekmonthtrolled trials (RCTs) up to June 2020. A systematic review with meta-analysis of RCTs was performed using random-effects model. Trial sequential analysis (TSA) was conducted for the primary outcome to assess random errors. A total of five RCTs with 1,617 participants were included. Posaconazole prophylaxis was associated with a significantly lower risk of IFIs (RR, 0.43 [95% CI 0.28 to 0.66, p = 0.0001]) as compared to other antifungal agents. No heterogeneity was identified between studies (I² = 0%). No significant associations were observed for the secondary outcomes measured, including risk reduction of invasive aspergillosis and candidiasis, clinical failure, all-cause mortality, and treatment-related adverse events, except for infection-related mortality (RR, 0.31 [95% CI 0.15 to 0.64, p = 0.0001]). Subgroup analysis favoured posaconazole over fluconazole for the prevention of IFIs (RR, 0.44 [95% CI 0.28 to 0.70, p = 0.0004]). TSA confirmed the prophylactic benefit of posaconazole against IFIs. Posaconazole is effective in preventing IFIs among immunocompromised patients, particularly those with hematologic malignancies and recipients of allogenic hematopoietic stem cell transplantation.

Candidaemia in haematological malignancy patients from a SEIFEM study: Epidemiological patterns according to antifungal prophylaxis

BACKGROUND

Candidaemia is an important infectious complication for haematological malignancy patients. Antifungal prophylaxis reduces the incidence of candidaemia but may be associated with breakthrough candidaemia.

OBJECTIVE

To analyse the Candida species' distribution and relative antifungal susceptibility profiles of candidaemia episodes in relation to the use of antifungal prophylaxis among Italian SEIFEM haematology centres.

METHODOLOGY

This multicentre retrospective observational SEIFEM study included 133 single-species candidaemia episodes of haematological malignancy patients for whom antifungal susceptibility testing results of blood Candida isolates were available between 2011 and 2015. Each participating centre provided both clinical and microbiological data.

RESULTS

Non-Candida albicans Candida (NCAC) species were the mostly isolated species (89, 66.9%), which accounted for C parapsilosis (35, 26.3%), C glabrata (16, 12.0%), C krusei (14, 10.5%), C tropicalis (13, 9.8%) and uncommon species (11, 8.3%). C albicans caused the remaining 44 (33.1%) episodes. Excluding 2 C albicans isolates, 23 of 25 fluconazole-resistant isolates were NCAC species (14 C krusei, 6 C glabrata, 2 C parapsilosis and 1 C tropicalis). Fifty-six (42.1%) of 133 patients developed breakthrough candidaemia. Systemic antifungal prophylaxis consisted of azoles, especially fluconazole and posaconazole, in 50 (89.3%) of 56 patients in whom a breakthrough candidaemia occurred. Interestingly, all these patients tended to develop a C krusei infection (10/56, P = .02) or a fluconazole-resistant isolate's infection (14/50, P = .04) compared to patients (4/77 and 10/77, respectively) who did not have a breakthrough candidaemia.

CONCLUSIONS

Optimisation of prophylactic strategies is necessary to limit the occurrence of breakthrough candidaemia and, importantly, the emergence of fluconazole-resistant NCAC isolates' infections in haematological malignancy patients.

Retrospective analysis of goal drug level attainment of posaconazole for invasive fungal infection prophylaxis in patients with acute myeloid leukemia pre- and post-switch to tablet formulation

Background

Posaconazole is approved for invasive fungal infection prophylaxis in patients with hematologic malignancies. Posaconazole suspension is plagued by poor oral absorption and dietary requirements that are difficult for patients to meet. The delayed-release tablet formulation of posaconazole may be taken without regards to meals and has significantly better oral absorption than posaconazole suspension.

Objectives

We sought to determine if a switch to posaconazole tablets improved steady-state drug level attainment for invasive fungal infection prophylaxis in patients with acute myeloid leukemia.

Methods

All adult inpatients with acute myeloid leukemia undergoing chemotherapy, who received posaconazole for invasive fungal infection prophylaxis between 2012 and 2015, were included. The primary outcome was proportion of patients with first posaconazole level greater than 700 ng/mL. Secondary outcomes included proportion of patients with first posaconazole level greater than 1000 ng/mL, invasive fungal infection within 100 days, and adverse drug events.

Results

Forty patients received posaconazole tablets and 34 patients received suspension. Posaconazole levels were significantly higher at first measurement in patients receiving tablet than suspension (1296 ng/mL vs. 788 ng/mL, p < 0.01). Thirty-seven patients receiving tablets had a serum drug level greater than 700 ng/mL on first measurement versus 18 receiving suspension (p < 0.01). Patients receiving tablets were also more likely to have a serum drug level over 1000 ng/mL on first measurement (26 vs. 11, p < 0.01). Rates of invasive fungal infection and adverse events were not statistically different.

Conclusions

Patients receiving posaconazole tablets attained significantly higher serum drug levels than those receiving suspension.

Inhibition of 11β-hydroxysteroid dehydrogenase 2 by the fungicides itraconazole and posaconazole

Impaired 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)-dependent cortisol inactivation can lead to electrolyte dysbalance, hypertension and cardiometabolic disease. Furthermore, placental 11β-HSD2 essentially protects the fetus from high maternal glucocorticoid levels, and its impaired function has been associated with altered fetal growth and a higher risk for cardio-metabolic diseases in later life. Despite its important role, 11β-HSD2 is not included in current off-target screening approaches. To identify potential 11β-HSD inhibitors among approved drugs, a pharmacophore model was used for virtual screening, followed by biological assessment of selected hits. This led to the identification of several azole fungicides as 11β-HSD inhibitors, showing a significant structure-activity relationship between azole scaffold size, 11β-HSD enzyme selectivity and inhibitory potency. A hydrophobic linker connecting the azole ring to the other, more polar end of the molecule was observed to be favorable for 11β-HSD2 inhibition and selectivity over 11β-HSD1. The most potent 11β-HSD2 inhibition, using cell lysates expressing recombinant human 11β-HSD2, was obtained for itraconazole (IC₅₀ 139±14nM), its active metabolite hydroxyitraconazole (IC₅₀ 223±31nM) and posaconazole (IC₅₀ 460±98nM). Interestingly, experiments with mouse and rat kidney homogenates showed considerably lower inhibitory activity of these compounds towards 11β-HSD2, indicating important species-specific differences. Thus, 11β-HSD2 inhibition by these compounds is likely to be overlooked in preclinical rodent studies. Inhibition of placental 11β-HSD2 by these compounds, in addition to the known inhibition of cytochrome P450 enzymes and P-glycoprotein efflux transport, might contribute to elevated local cortisol levels, thereby affecting fetal programming.

Itraconazole-induced thrombocytopenia

Itraconazole is one of the systemic treatment options for extensive tinea versicolor. A male patient who developed thrombocytopenia during the treatment of tinea versicolor by itraconazole is reported in this manuscript. He was diagnosed to develop thrombocytopenia on the third day of treatment. In the literature, there are two reports of itraconazole-induced thrombocytopenia both in malignancy patients. One report contained three patients who developed thrombocytopenia as a result of a drug interaction between bortezomib and itraconazole. The other report contained a patient who developed thrombocytopenia following six weeks of treatment with itraconazole. It is hypothesized by the author of this manuscript that this patient's thrombocytopenia developed as a result of selective bone marrow suppression which is brought about by itraconazole's effect on megakaryocytes.

[Not Available]

Posaconazole, systemic antifungal marketed in France since 2006, is indicated as second line in curative treatment of invasive fungal infections (IFI) (aspergillosis. . . ) and prophylaxis of IFI in patients receiving chemotherapy or hematopoietic stem cell transplantation. The analysis of the literature indicates a concentration-efficacy relationship, but to date, no study has been able to show a concentration-toxicity correlation due to its favourable safety profile and the difficulty to obtain high concentrations. In curative, maintenance of trough plasma concentrations between 0.5 and 1.5 mg/L seems to be associate with an efficacy. In prophylaxis, a threshold of 0.5 mg/L corresponds to a minimal exposure. However this target is not yet well defined. Saturation of absorption above the 800 mg oral dose limits the adjustment of concentrations. As such, the Therapeutic Drug Monitoring of posaconazole can be recommended.

Posaconazole treatment in Korea: single-center experience over 5 years

PURPOSE

Posaconazole is a second-generation triazole with a broad spectrum. However, there is a lack of data to support a significant role for posaconazole in the treatment of invasive fungal infection (IFI), especially in Korea. Until recently, posaconazole was available only through the Korean Orphan Drug Center. This study was designed to review the use of posaconazole at a single-center in Korea.

MATERIALS AND METHODS

Data from patients who received posaconazole treatment at Catholic Blood and Marrow Transplantation Center were retrospectively reviewed between January 2007 and September 2012.

RESULTS

A total of 11 cases (3 males and 8 females, median age 52 years) received posaconazole. Five patients were given the drug for mucormycosis, two for invasive aspergillosis, and four for unspecified IFI for which galactomannan (GM) assays were negative. The treatment duration ranged from 4-250 days. Three patients received posaconazole for management refractory IFI, two for intolerance of previous antifungal therapy, and six for long-term maintenance treatment. The overall successful response rate to posaconazole was 55% (six of eleven patients). Five of eleven patients died during the study period. However, only one death was attributed to the progression of IFI. None of the patients discontinued posaconazole therapy due to adverse events.

CONCLUSION

Posaconazole is an attractive oral antifungal agent for salvage treatment of IFI, particularly upon diagnosis of mucormycosis or in cases in which mucormycosis cannot be ruled out due to a negative GM.

Posaconazole therapeutic drug monitoring in pediatric patients and young adults with cancer

BACKGROUND

Limited information exists regarding the use of posaconazole for treating systemic fungal infections in children, adolescents, and young adults with cancer. At St. Jude Children's Research Hospital, the recommended posaconazole dose in patients weighing less than 34 kg is 18-24 mg/kg daily, given in 4 divided doses. For patients aged 13 years or older or those weighing 34 kg or more, the recommended dose is 800 mg daily, given orally in 4 divided doses.

OBJECTIVE

To determine whether the current posaconazole dosing guidelines achieve target posaconazole plasma concentrations of 0.7 μg/mL or greater.

METHODS

This retrospective clinical study examined data from patients who received treatment-dose posaconazole and had at least 1 posaconazole plasma concentration measurement.

RESULTS

Data from 33 patients who received posaconazole for the treatment of fungal infections were analyzed. The median age of patients was 11.5 years (range 0.5-23.2). Twenty-one of 33 patients (63.6%) had posaconazole concentrations of 0.7 μg/mL or greater (median 1.4; range 0.7-2.98) at the first measurement. The median posaconazole dosage referenced to total body weight in these patients was 20 mg/kg/day. Patients with concentrations less than 0.7 μg/mL (median 0.4; range 0.025-0.69) received lower posaconazole dosages when referenced to body weight (median 12.9 mg/kg/day; p = 0.02). Of the 12 patients with concentrations less than 0.7 μg/mL, 7 (58.3%) were aged 13 years or older.

CONCLUSIONS

The current dosing approach for posaconazole yielded therapeutic plasma concentrations more frequently in patients younger than 13 years than in those 13 years or older. This difference may be related to the practice of capping adolescent and young adult doses at the suggested maximum adult daily dose. Therefore, we recommend weight-based dosing in all pediatric, adolescent, and young adult patients with cancer, with routine therapeutic drug monitoring to ensure adequate concentrations.

Cerebral phaeohyphomycosis caused by Rhinocladiella mackenziei in a woman native to Afghanistan

Rhinocladiella mackenziei is a recognized cause of endemic cerebral phaeohyphomycosis in the Middle East area. Surgical resection of the abscesses and posaconazole treatment have improved the ominous prognosis of this disease. We describe the case of a native Afghan woman living in France who presented with brain abscesses due to R. mackenziei.

A nonazole CYP51 inhibitor cures Chagas' disease in a mouse model of acute infection

Chagas' disease, the leading cause of heart failure in Latin America, is caused by the kinetoplastid protozoan Trypanosoma cruzi. The sterols of T. cruzi resemble those of fungi, both in composition and in biosynthesis. Azole inhibitors of sterol 14alpha-demethylase (CYP51) successfully treat fungal infections in humans, and efforts to adapt the success of antifungal azoles posaconazole and ravuconazole as second-use agents for Chagas' disease are under way. However, to address concerns about the use of azoles for Chagas' disease, including drug resistance and cost, the rational design of nonazole CYP51 inhibitors can provide promising alternative drug chemotypes. We report the curative effect of the nonazole CYP51 inhibitor LP10 in an acute mouse model of T. cruzi infection. Mice treated with an oral dose of 40 mg LP10/kg of body weight twice a day (BID) for 30 days, initiated 24 h postinfection, showed no signs of acute disease and had histologically normal tissues after 6 months. A very stringent test of cure showed that 4/5 mice had negative PCR results for T. cruzi, and parasites were amplified by hemoculture in only two treated mice. These results compare favorably with those reported for posaconazole. Electron microscopy and gas chromatography-mass spectrometry (GC-MS) analysis of sterol composition confirmed that treatment with LP10 blocked the 14alpha-demethylation step and induced breakdown of parasite cell membranes, culminating in severe ultrastructural and morphological alterations and death of the clinically relevant amastigote stage of the parasite.

Structural characterization of CYP51 from Trypanosoma cruzi and Trypanosoma brucei bound to the antifungal drugs posaconazole and fluconazole

BACKGROUND

Chagas Disease is the leading cause of heart failure in Latin America. Current drug therapy is limited by issues of both efficacy and severe side effects. Trypansoma cruzi, the protozoan agent of Chagas Disease, is closely related to two other major global pathogens, Leishmania spp., responsible for leishmaniasis, and Trypansoma brucei, the causative agent of African Sleeping Sickness. Both T. cruzi and Leishmania parasites have an essential requirement for ergosterol, and are thus vulnerable to inhibitors of sterol 14alpha-demethylase (CYP51), which catalyzes the conversion of lanosterol to ergosterol. Clinically employed anti-fungal azoles inhibit ergosterol biosynthesis in fungi, and specific azoles are also effective against both Trypanosoma and Leishmania parasites. However, modification of azoles to enhance efficacy and circumvent potential drug resistance has been problematic for both parasitic and fungal infections due to the lack of structural insights into drug binding.

METHODOLOGY/PRINCIPAL FINDINGS

We have determined the crystal structures for CYP51 from T. cruzi (resolutions of 2.35 A and 2.27 A), and from the related pathogen T. brucei (resolutions of 2.7 A and 2.6 A), co-crystallized with the antifungal drugs fluconazole and posaconazole. Remarkably, both drugs adopt multiple conformations when binding the target. The fluconazole 2,4-difluorophenyl ring flips 180 degrees depending on the H-bonding interactions with the BC-loop. The terminus of the long functional tail group of posaconazole is bound loosely in the mouth of the hydrophobic substrate binding tunnel, suggesting that the major contribution of the tail to drug efficacy is for pharmacokinetics rather than in interactions with the target.

CONCLUSIONS/SIGNIFICANCE

The structures provide new insights into binding of azoles to CYP51 and mechanisms of potential drug resistance. Our studies define in structural detail the CYP51 therapeutic target in T. cruzi, and offer a starting point for rationally designed anti-Chagasic drugs with improved efficacy and reduced toxicity.

Efficacy of posaconazole in a murine disseminated infection by Candida tropicalis

We evaluated the efficacy of posaconazole against Candida tropicalis in a systemic infection model with immunosuppressed mice. Posaconazole at 50 mg/kg of body weight/day prolonged the survival of mice and reduced the fungal tissue burden of mice infected with any of the five strains tested, with the exception of one strain that had a high MIC against this drug. Our results demonstrate the efficacy of posaconazole in the treatment of invasive murine infection caused by C. tropicalis.

Correlation of in vitro activity, serum levels, and in vivo efficacy of posaconazole against Rhizopus microsporus in a murine disseminated infection

A broth microdilution method was used to evaluate the in vitro activities of seven antifungal agents against 15 clinical strains of Rhizopus microsporus. Amphotericin B (AMB) and posaconazole (POS) were the most active drugs. In a model of disseminated R. microsporus infection in immunosuppressed mice, we studied the efficacy of POS administered once or twice daily against four of the strains previously tested in vitro and compared it with that of liposomal AMB (LAMB). LAMB was the most effective treatment for the two strains with intermediate susceptibility to POS. For the two POS-susceptible strains, LAMB and POS at 20 mg/kg of body weight twice a day orally showed similar efficacies. The in vivo efficacy of POS administered twice a day orally correlated with the in vitro susceptibility data and the serum drug concentrations.

Synthesis of a highly water-soluble derivative of amphotericin B with attenuated proinflammatory activity

Amphotericin B (AmB), a well-known polyene antifungal agent, displays a marked tendency to self-associate and, as a consequence, exhibits very poor solubility in water. The therapeutic index of AmB is low and is associated with significant dose-related nephrotoxicity, as well as acute, infusion-related febrile reactions. Reports in the literature indicate that the toxicity of AmB may be related to the physical state of the drug. Reaction of AmB in dimethylformamide with bis(dimethylaminopropyl)carbodiimide yielded an unexpected N-alkylguanidine/N-acylurea bis-adduct of AmB which was highly water-soluble. The absorption spectrum of the AmB derivative in water indicated excellent monomerization, and the antifungal activities of reference AmB and its water-soluble derivative against Candida albicans were found to be virtually identical. Furthermore, the water-soluble adduct is significantly less active in engaging TLR4, which would suggest that the adduct may be less proinflammatory.