The paper states that for fungal infections, the active metabolite isavuconazole inhibits lanosterol 14α-demethylase.[2]

With EC50 values of 0.001 μM, 0.037 μM, and 0.024 μM, respectively, isavuconazonium sulfate (0.006 nM–50 μM) suppresses the trophoblast activity of three T4-genotype strains of Acanthamoeba (Ma, CDC:V240, and MEEI 0184). Furthermore, three tested strains, Ma, CDC:V240, and MEEI 0184, showed vesicle-extinguishing activity at (100–200 μM; 48 h), with mean minimum vesicle extinguishing concentrations (MCC) of 167.1 μM, 136.0 μM, and 187.5 μM, respectively[2].

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Isavuconazonium sulfate exhibits potent amebicidal activity against trophozoites of three T4 genotype Acanthamoeba strains (Ma, CDC:V240, MEEI 0184). The EC₅₀ values (mean) were: 0.001 μM against strain Ma, 0.037 μM against strain CDC:V240, and 0.024 μM against strain MEEI 0184. These potencies are in the low nanomolar range and, for strain Ma, were 1700- to 5000-fold more potent than standard care agents chlorhexidine and PHMB. Isavuconazonium sulfate also displays cysticidal activity against cysts of the same strains. The average minimum cysticidal concentrations (MCCs) were: 167.1 ± 23.6 μM against strain Ma, 136.0 ± 11.4 μM against strain CDC:V240, and 187.5 ± 5.0 μM against strain MEEI 0184. The combination of isavuconazonium sulfate with polyhexamethylene biguanide (PHMB) against cysts of strain Ma was evaluated; no obvious synergistic or antagonistic cysticidal effect was observed. [2]

Isavuconazonium sulfate (215 mg/kg; p.o. ; three times daily for four days) exhibits anti-R.delemar virus activity in mucormycosis-infected ICR mice[4].

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In a neutropenic murine model of mucormycosis induced by intratracheal infection with Rhizopus delmar, treatment with isavuconazonium sulfate (215 mg/kg, three times daily) starting 8 hours post-infection significantly improved survival compared to placebo (70% vs. 10% survival at day 21).
Isavuconazole was as effective as high-dose liposomal amphotericin B (LAmB) in improving survival and reducing fungal burden in lungs and brains of infected mice.
Treatment with isavuconazonium sulfate resulted in approximately a 1-log decrease in fungal burden in lungs and brains compared to placebo-treated mice.

Amebicidal Activity Assay: Trophozoites of Acanthamoeba T4 strains were cultured in peptone yeast glucose (PYG) medium. A stock solution of 10 mM isavuconazonium sulfate in DMSO was serially diluted two-fold. Aliquots (0.5 μL) of these dilutions were added to wells of a 96-well plate. Subsequently, 5×10³ trophozoites in 99.5 μL of PYG medium were added to each well, resulting in final test concentrations ranging from 50 μM to 5.96 pM. Negative control wells received 0.5 μL DMSO (0.5% v/v). Positive control wells received 0.5 μL of chlorhexidine (50 μM final). Plates were incubated at 28°C with 5% CO₂ for 48 hours. Cell viability was then measured using a luminescent cell viability assay reagent (CellTiter-Glo), which was added to each well, followed by shaking and luminescence reading. EC₅₀ values were calculated from triplicate experiments using data analysis software. [2]
Cysticidal Activity Assay: Cysts were generated by inducing encystment of trophozoites in a defined encystation medium for 48 hours in a 96-well plate. After cyst formation, 0.5 μL of isavuconazonium sulfate solution was added to achieve final concentrations ranging from 200 μM to 100 μM in 10 μM increments. Negative control wells received 0.5% (v/v) DMSO, and positive control wells received 461.85 μM PHMB. Following a 48-hour treatment, wells were washed with PBS and then incubated in PYG growth medium for 7 days, with media changes on days 3 and 5. Cysts were imaged at 200× magnification on day 7. Cysticidal activity was defined as the absence of excystation (no trophozoites observed) by day 7. [2]
Combination Assay (Cysts): A checkerboard dilution scheme was used. Serial two-fold dilutions of isavuconazonium sulfate (from 65.7 mM to 512 μM) and PHMB (from 64.7 mM to 504 μM) were prepared. Aliquots (0.25 μL each) of the drug dilutions were combined in wells to generate a matrix of concentration combinations, with final concentrations ranging from 164.14 to 1.28 μM for isavuconazonium sulfate and 161.15 to 1.26 μM for PHMB. Cysts were treated for 48 hours, washed, and then incubated in PYG medium for 7 days with imaging. Excystation was manually scored. [2]

Animal Model: Neutropenic male ICR mouse model of intratracheal infection[4]
Dosage: 215 mg/kg
Administration: Oral gavage (p.o.); Three times a day for 4 days.
Result: increased the survival rate of R. delemar-infected neutropenic mice.
decreased amount of fungi in the mice's brains and lungs.

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Male ICR mice (23–25 g) were used in the study. Neutropenia was induced by intraperitoneal injection of cyclophosphamide (200 mg/kg) and subcutaneous injection of cortisone acetate (500 mg/kg) on days -2 and 3 relative to infection.
Mice were intratracheally infected with 2.5 × 10⁵ spores of Rhizopus delmar 99-880 under sedation with ketamine and xylazine.
Isavuconazonium sulfate was prepared fresh daily in irrigation water and administered orally at doses of 80, 110, or 215 mg/kg three times daily, starting 8 hours post-infection and continuing through day 4.
Liposomal amphotericin B (LAmB) was dissolved in sterile irrigation water, diluted in 5% dextrose water, and administered once daily via tail vein injection at 15 mg/kg.
Placebo groups received irrigation water or 5% dextrose water.

In mice, after oral administration of isoxaconazole sulfate at doses of 10, 40, 160, and 640 mg/kg, peak serum concentrations of isoxaconazole ranged from 0.51 to 25.4 μg/ml, with elimination half-lives ranging from 1 to 5 hours. In contrast, in humans, the half-life exceeds 50 hours after a single dose. It is estimated that after three daily administrations of a higher dose of 215 mg/kg to mice, peak serum concentrations exceeded 12.5 μg/ml, with a half-life exceeding 3.1 hours.

[1]. Isavuconazonium sulfate: a new agent for the treatment of invasive aspergillosis and invasive mucormycosis[J]. Expert review of clinical pharmacology, 2016, 9(7): 887-897.

[2]. Evaluation of Amebicidal and Cysticidal Activities of Antifungal Drug Isavuconazonium Sulfate against Acanthamoeba T4 Strains. Pharmaceuticals (Basel). 2021 Dec 11;14(12):1294.

[3]. Isavuconazonium sulfate: a novel antifungal agent[J]. Current Fungal Infection Reports, 2015, 9: 302-313.

[4]. Isavuconazole therapy protects immunosuppressed mice from mucormycosis[J]. Antimicrobial agents and chemotherapy, 2014, 58(4): 2450-2453.

[5]. In Vitro Activity of Isavuconazole against Rasamsonia Species.Antimicrob Agents Chemother.2016 Oct 21;60(11):6890-6891.

Isavuconazonium sulfate is a nitrogen-containing heterocyclic sulfate and a prodrug of the antifungal drug ixaconazole, used to treat invasive aspergillosis and invasive mucormycosis. It has multiple functions, including as a prodrug, an inhibitor of ergosterol biosynthesis, an EC 1.14.13.70 (sterol 14α-demethylase) inhibitor, and an orphan drug. It is a nitrogen-containing heterocyclic sulfate, a triazole antifungal drug, and a serotonin antifungal drug. It contains an ixaconazole group. Isavuconazonium sulfate is the sulfate ester form of ixaconazole, a prodrug of the triazole antifungal drug ixaconazole, with broad-spectrum antifungal activity. After administration, ixaconazole sulfate is hydrolyzed by plasma esterases to produce the active ingredient, ixaconazole. Isavuconazonium binds to and inhibits the activity of fungal cytochrome P450 family enzyme lanosterol 14α-demethylase (CYP51). CYP51 catalyzes the demethylation of lanosterol to ergosterol, an essential component of fungal cell membranes. Inhibition of CYP51 leads to decreased fungal ergosterol production and disrupts fungal cell membrane synthesis, thereby reducing cell membrane integrity, increasing cell membrane permeability, and promoting the loss of essential intracellular components. This results in fungal cell lysis and death.
See also: Isavuconazonium (containing the active ingredient).

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Drug Indications
Treatment of invasive aspergillosis, treatment of mucormycosis
Treatment of Candida infections

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Isavuconazonium sulfate is an FDA-approved prodrug for the treatment of invasive aspergillosis and mucormycosis, available orally or intravenously. This study explores its potential for the treatment of Acanthamoeba keratitis (AK). The active metabolite, ixaconazole, has previously been shown to have amoeboid and cysticergic activity. This study showed that the prodrug isoxaconazole sulfate itself has potent amoeboid activity (low nanomolar EC₅₀) and cystic activity (high micromolar MCC) against a variety of T4 genotype Acanthamoeba strains. This is significant because it is unclear whether the prodrug, when used topically to treat Acanthamoeba keratitis (AK), can be metabolized into its active form in the human eye. The results indicate that isoxaconazole sulfate retains its biological activity against Acanthamoeba and may be a promising candidate drug for the topical treatment of AK, potentially avoiding in vivo metabolic activation. The study also found that the combination of isoxaconazole sulfate and polyhexamethylene biguanide (PHMB) did not show synergistic or antagonistic effects on cysts. [2]

C35H36F2N8O9S2

814.83500

814.201

C, 51.59; H, 4.45; F, 4.66; N, 13.75; O, 17.67; S, 7.87

946075-13-4

338990-84-4 (chloride);497235-79-7 (chloride HCl);742049-41-8 (cation);946075-13-4 (sulfate);

72196309

White to off-white solid powder

5.06

3

17

15

56

1290

2

S(O)([O-])(=O)=O.[C@@](C1C=C(F)C=CC=1F)(O)(CN1N=C[N+](C(C)OC(=O)N(C2N=CC=CC=2COC(=O)CNC)C)=C1)[C@H](C1SC=C(C2C=CC(C#N)=CC=2)N=1)C

LWXUIUUOMSMZKJ-KLFWAVJMSA-M

InChI=1S/C35H35F2N8O5S.H2O4S/c1-22(33-42-30(18-51-33)25-9-7-24(15-38)8-10-25)35(48,28-14-27(36)11-12-29(28)37)19-45-21-44(20-41-45)23(2)50-34(47)43(4)32-26(6-5-13-40-32)17-49-31(46)16-39-3;1-5(2,3)4/h5-14,18,20-23,39,48H,16-17,19H2,1-4H3;(H2,1,2,3,4)/q+1;/p-1/t22-,23?,35+;/m0./s1

1-((2R,3R)-3-(4-(4-cyanophenyl)thiazol-2-yl)-2-(2,5-difluorophenyl)-2-hydroxybutyl)-4-(1-((methyl(3-(((methylglycyl)oxy)methyl)pyridin-2-yl)carbamoyl)oxy)ethyl)-1H-1,2,4-triazol-4-ium hydrogen sulfate

BAL8557;BAL 8557; Isavuconazonium sulfate; BAL-8557; Cresemba.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 100 mg/mL ( 122.72 mM )
Water : 0.5~100 mg/mL (~0.61 mM )
Ethanol : 100 mg/mL

Solubility in Formulation 1: ≥ 2.08 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 10% DMSO+40% PEG300+5% Tween-80+45% Saline: ≥ 2.08 mg/mL (2.55 mM)

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Solubility in Formulation 5: 100 mg/mL (122.72 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)