A ketogenic diet enhances fluconazole efficacy in murine models of systemic fungal infection

Invasive fungal infections are a significant public health concern, with mortality rates ranging from 20% to 85% despite current treatments. Therefore, we examined whether a ketogenic diet could serve as a successful treatment intervention in murine models of Cryptococcus neoformans and Candida albicans infection in combination with fluconazole-a low-cost, readily available antifungal therapy. The ketogenic diet is a high-fat, low-carbohydrate diet that promotes fatty acid oxidation as an alternative to glycolysis through the production of ketone bodies. In this series of experiments, mice fed a ketogenic diet prior to infection with C. neoformans and treated with fluconazole had a significant decrease in fungal burden in both the brain (mean 2.66 ± 0.289 log10 reduction) and lung (mean 1.72 ± 0.399 log10 reduction) compared to fluconazole treatment on a conventional diet. During C. albicans infection, kidney fungal burden of mice in the keto-fluconazole combination group was significantly decreased compared to fluconazole alone (2.37 ± 0.770 log10-reduction). Along with higher concentrations of fluconazole in the plasma and brain tissue, fluconazole efficacy was maximized at a significantly lower concentration on a keto diet compared to a conventional diet, indicating a dramatic effect on fluconazole pharmacodynamics. Our findings indicate that a ketogenic diet potentiates the effect of fluconazole at multiple body sites during both C. neoformans and C. albicans infection and could have practical and promising treatment implications.IMPORTANCEInvasive fungal infections cause over 2.5 million deaths per year around the world. Treatments for fungal infections are limited, and there is a significant need to develop strategies to enhance antifungal efficacy, combat antifungal resistance, and mitigate treatment side effects. We determined that a high-fat, low-carbohydrate ketogenic diet significantly potentiated the therapeutic effect of fluconazole, which resulted in a substantial decrease in tissue fungal burden of both C. neoformans and C. albicans in experimental animal models. We believe this work is the first of its kind to demonstrate that diet can dramatically influence the treatment of fungal infections. These results highlight a novel strategy of antifungal drug enhancement and emphasize the need for future investigation into dietary effects on antifungal drug activity.

Pharmacodynamics of ATI-2307 in a rabbit model of cryptococcal meningoencephalitis

Cryptococcal meningoencephalitis (CM) is a devastating fungal disease with high morbidity and mortality. The current regimen that is standard-of-care involves a combination of three different drugs administered for up to one year. There is a critical need for new therapies due to both toxicity and inadequate fungicidal activity of the currently available antifungal drugs. ATI-2307 is a novel aryl amidine that disrupts the mitochondrial membrane potential and inhibits the respiratory chain complexes of fungi-it thus represents a new mechanism for direct antifungal action. Furthermore, ATI-2307 selectively targets fungal mitochondria via a fungal-specific transporter that is not present in mammalian cells. It has very potent in vitro anticryptococcal activity. In this study, the efficacy of ATI-2307 was tested in a rabbit model of CM. ATI-2307 demonstrated significant fungicidal activity at dosages between 1 and 2 mg/kg/d, and these results were superior to fluconazole and similar to amphotericin B treatment. When ATI-2307 was combined with fluconazole, the antifungal effect was greater than either therapy alone. While ATI-2307 has potent anticryptococcal activity in the subarachnoid space, its ability to reduce yeasts in the brain parenchyma was relatively less over the same study period. This new drug, with its unique mechanism of fungicidal action and ability to positively interact with an azole, has demonstrated sufficient anticryptococcal potential in this experimental setting to be further evaluated in clinical studies.

Susceptibility to Cryptococcus neoformans Infection with Bruton's Tyrosine Kinase Inhibition

Patients receiving the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib have an increased likelihood of fungal infections. The objectives of this study were to determine if Cryptococcus neoformans infection severity was isolate dependent with BTK inhibition and whether blocking BTK impacted infection severity in a mouse model. We compared four clinical isolates from patients on ibrutinib to virulent (H99) and avirulent (A1-35-8) reference strains. BTK knockout (KO) and wild-type (WT) C57 mice and WT CD1 mice were infected by intranasal (i.n.), oropharyngeal aspiration (OPA), and intravenous (i.v.) routes. Infection severity was assessed by survival and fungal burden (CFU per gram of tissue). Ibrutinib (25 mg/kg) or vehicle was administered daily through intraperitoneal injections. In the BTK KO model, no isolate-dependent effect on fungal burden was observed, and infection severity was not significantly different from that of the WT with i.n., OPA, and i.v. routes. Ibrutinib treatment did not impact infection severity. However, when the four clinical isolates were compared to H99, two of these isolates were less virulent, with significantly longer survival and reduced rates of brain infection. In conclusion, C. neoformans infection severity in the BTK KO model does not appear to be isolate dependent. BTK KO and ibrutinib treatment did not result in significantly different infection severities. However, based on repeated clinical observations of increased susceptibility to fungal infections with BTK inhibitor therapy, further work is needed to optimize a mouse model with BTK inhibition to better understand the role that this pathway plays in susceptibility to C. neoformans infection.

Efficacy of APX2039 in a Rabbit Model of Cryptococcal Meningitis

Cryptococcal Meningitis (CM) is uniformly fatal if not treated, and treatment options are limited. We previously reported on the activity of APX2096, the prodrug of the novel Gwt1 inhibitor APX2039, in a mouse model of CM. Here, we investigated the efficacy of APX2039 in mouse and rabbit models of CM. In the mouse model, the controls had a mean lung fungal burden of 5.95 log10 CFU/g, whereas those in the fluconazole-, amphotericin B-, and APX2039-treated mice were 3.56, 4.59, and 1.50 log10 CFU/g, respectively. In the brain, the control mean fungal burden was 7.97 log10 CFU/g, while the burdens were 4.64, 7.16, and 1.44 log10 CFU/g for treatment with fluconazole, amphotericin B, and APX2039, respectively. In the rabbit model of CM, the oral administration of APX2039 at 50 mg/kg of body weight twice a day (BID) resulted in a rapid decrease in the cerebrospinal fluid (CSF) fungal burden, and the burden was below the limit of detection by day 10 postinfection. The effective fungicidal activity (EFA) was -0.66 log10 CFU/mL/day, decreasing from an average of 4.75 log10 CFU/mL to 0 CFU/mL, over 8 days of therapy, comparing favorably with good clinical outcomes in humans associated with reductions of the CSF fungal burden of -0.4 log10 CFU/mL/day, and, remarkably, 2-fold the EFA of amphotericin B deoxycholate in this model (-0.33 log10 CFU/mL/day). A total drug exposure of the area under the concentration-time curve from 0 to 24 h (AUC0-24) of 25 to 50 mg · h/L of APX2039 resulted in near-maximal antifungal activity. These data support the further preclinical and clinical evaluation of APX2039 as a new oral fungicidal monotherapy for the treatment of CM. IMPORTANCE Cryptococcal meningitis (CM) is a fungal disease with significant global morbidity and mortality. The gepix Gwt1 inhibitors are a new class of antifungal drugs. Here, we demonstrated the efficacy of APX2039, the second member of the gepix class, in rabbit and mouse models of cryptococcal meningitis. We also analyzed the drug levels in the blood and cerebrospinal fluid in the highly predictive rabbit model and built a mathematical model to describe the behavior of the drug with respect to the elimination of the fungal pathogen. We demonstrated that the oral administration of APX2039 resulted in a rapid decrease in the CSF fungal burden, with an effective fungicidal activity of -0.66 log10 CFU/mL/day, comparing favorably with good clinical outcomes in humans associated with reductions of -0.4 log10 CFU/mL/day. The drug APX2039 had good penetration of the central nervous system and is an excellent candidate for future clinical testing in humans for the treatment of CM.

605. Efficacy and pharmacokinetics-pharmacodynamics of ATI-2307 in a rabbit model of cryptococcal meningoencephalitis

Background

Cryptococcal meningitis (CM) is a fungal disease with significant global morbidity and mortality. There are multiple new therapies being developed to improve the current regimens involving amphotericin B, flucytosine, and fluconazole. ATI-2307 is a novel arylamidine which inhibits mitochondrial function in yeasts. We tested ATI-2307 in a rabbit model of CM and evaluated its efficacy, pharmacokinetics, and pharmacodynamics (PK-PD).

Methods

Immune suppressed rabbits were infected with Cryptococcus neoformans. Starting two days after the infection, they were treated with ATI-2307 (1, 2, or 3 mg/kg), amphotericin B (1 mg/kg), fluconazole (80 mg/kg), a combination of ATI-2307 (1 mg/kg) and fluconazole (80 mg/kg), or they were untreated. ATI-2307 was given daily subcutaneously. Fungal burden and drug levels were quantified in the CSF during the infection and in the brain tissue at study termination, day 4, 10, or 14 post infection. Drug pharmacokinetics in the blood were examined on day 8 post infection. Drug pharmacokinetics in the CSF and brain tissue were examined at day 4 post infection.

Results

Daily dosing with ATI-2307 reduced the yeast burden in both the cerebrospinal fluid (CSF) and brain tissue compared to controls. Furthermore, when combined with fluconazole, ATI-2307 reduced the CSF fungal burden below the limit of detection. In fact, we observed a large reduction in fungal burden relative to untreated controls with only three doses, which was sustained for 1 week after the cessation of dosing. The kinetics of ATI-2307 indicated that the drug has a long gamma phase in both blood and CSF. In addition, our analysis of the drug levels in the brain tissue indicated that it dramatically accumulated in the meninges, which may then serve as a site of sustained release.

Efficacy of ATI-2307 on CSF Fungal Burden and Distribution of ATI-2307 in Brain Tissue

ATI-2307 was dosed daily starting at day 2 post infection through the study endpoint, day 10 or 14 post infection, with the exception of the 2 mg/kg, 3 dose group, which only received doses on days 2, 3, and 4 post infection.

Conclusion

Taken together, these data provide evidence for ATI-2307 as a promising therapy for CM and it may require fewer doses than existing treatments and provide additive anticryptococcal activity with azole treatment.

Disclosures

Charles D. Giamberardino, Jr., MR, Affimed NV: Stocks/Bonds|Appili Therapeutics: Grant/Research Support|Interventional Analgesix Inc: Grant/Research Support|Minnetronix: Grant/Research Support|Pfizer: Grant/Research Support|Quoin Pharmaceuticals: Stocks/Bonds|Sfunga: Grant/Research Support Jennifer L. Tenor, PhD, Appili: Grant/Research Support|Pfizer: Grant/Research Support Dena Toffaletti, PhD, Appili Therapeutics: Grant/Research Support|Pfizzer: Grant/Research Support Don Cilla, Pharm.D., M.B.A., Appili Therapeutics: Employee|Appili Therapeutics: Stocks/Bonds William Hope, OBE (FRACP, FRCPA, PhD), Antabio: Grant/Research Support|Appili Therapeutics: Advisor/Consultant|BioVersys: Grant/Research Support|Bugworks: Grant/Research Support|Centauri: Advisor/Consultant|F2G: Advisor/Consultant|F2G: Grant/Research Support|NAEJA-RGM Pharmaceuticals Inc: Advisor/Consultant|NAEJA-RGM Pharmaceuticals Inc: Grant/Research Support|National Institute of Health Research (NIHR).: Co-lead for Infectious Diseases|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Phico Therapeutics: Grant/Research Support|Specialist Advisory Committee for GARDP: Advisor/Consultant|Spero Therapeutics: Advisor/Consultant|Spero Therapeutics: Grant/Research Support|The Global Antibiotic Research and Development Partnership (GARDP): Grant/Research Support|VenatoRx: Advisor/Consultant John R. Perfect, MD, Appili Therapeutics: Advisor/Consultant|Appili Therapeutics: Grant/Research Support|Astellas: Advisor/Consultant|Astellas: Grant/Research Support|Matinas: Advisor/Consultant|Merck: Advisor/Consultant|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Scynexis: Advisor/Consultant.

717. Susceptibility to Cryptococcosis in Bruton's Tyrosine Kinase Knockout Model

Background

Patients receiving the Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib have an increased likelihood of systemic and central nervous system (CNS) fungal infections. Previous work has shown that BTK knockout (KO) mice have more severe Aspergillus infection compared to wild-type (WT) mice. We sought to determine: 1) if blocking BTK impacted Cryptococcus infection; 2) if the effect was strain-dependent; and 3) if the blood-brain barrier was impaired in BTK KO mice.

Methods

BTK KO C57 breeding pairs were obtained from Dr. Lionakis (NIH) and expanded in the Duke Breeding Core. We collected 4 clinical C. neoformans isolates from patients who developed cryptococcosis on ibrutinib and used virulent and avirulent control strains (H99 and A1-35-8, respectively). The following doses were used for infection: 1) 5x104 yeast for intranasal (IN); 2) 5x104 for oropharyngeal aspiration (OPA); and 3) 0.1 mL of 5x105 CFU/mL for tail vein injection. Mice were sacrificed on day 7 (IN infection, 6 infection strains; N=35 WT, 80 KO) and day 14 post-infection (OPA infection H99 only; N=15 WT, 20 KO). Lung and brain tissues were collected for yeast census. For tail vein injection, mice were sacrificed 48 hours post-infection (H99 only; N=10 WT, 8 KO). Yeast census was measured by colony forming units (CFUs) per gram of tissue weight. Survival experiments through day 28 were performed for OPA infection with H99 (N=12 WT, 17 KO) and analyzed by Kaplan Meier Curve.

Results

We observed no difference in infection severity as measured by lung and brain yeast census at days 7 and 14 post-infection or difference in survival between BTK KO and WT mice (Figure 1). We also did not observe a distinct pattern based on Cryptococcus strain to suggest that infection severity was strain-dependent (Figure 1A-B). For tail vein infection, there was no difference in brain yeast census at 48 hours post-infection (Figure 1F).

Conclusion

Our results in mice suggest that Ibrutinib target BTK is not a major contributing factor for controlling Cryptococcus, and that human susceptibility to cryptococcosis and CNS infection may be due to an off-target effect of ibrutinib. Future work will focus on pharmacologic inhibition of BTK with ibrutinib to determine if the off-target effects of the drug increase risk for cryptococcosis.

Disclosures

Julia A. Messina, MD, MHS, MS, Uptodate (Other Financial or Material Support) Julia A. Messina, MD, MHS, MS, Uptodate (Individual(s) Involved: Self): Author, Other Financial or Material Support John R. Perfect, MD, Astellas Pharma, Inc. (Consultant, Grant/Research Support, Other Financial or Material Support, Honorarium)Basilea (Consultant, Grant/Research Support)Enzon (Consultant, Grant/Research Support)F2G (Consultant, Grant/Research Support)Merck (Consultant, Research Grant or Support)MethylGene (Consultant, Grant/Research Support)Pfizer, Inc. (Consultant, Grant/Research Support)Schering-Plough Corp. (Consultant, Grant/Research Support)

168. Efficacy of the Novel gwt1 Inhibitor APX2039 in a Rabbit Model of cryptococcus Meningitis

Background

Cryptococcal meningitis (CM), caused primarily by Cryptococcus neoformans, is uniformly fatal if not treated. Treatment options are limited especially in resource-poor geographical regions, and mortality rates remain high despite current therapies. New oral treatment options are needed that demonstrate rapid reductions in CFU in CSF and brain tissue.

APX2039 is a novel inhibitor of the fungal Gwt1 enzyme, which catalyzes an early step in glycosylphosphatidyl inositol (GPI) anchor biosynthesis. It is highly active against both C. neoformans and C. gattii and has previously demonstrated significant efficacy in a mouse delayed-treatment model of CM.

CSF Fungal Burden in Rabbits

Methods

Male New Zealand White rabbits were inoculated with C. neoformans H99 (1.4 ×10⁶ CFU) directly into the cisterna magna. Rabbits were immunosuppressed with cortisone acetate at 7.5 mg/kg (i.m.), starting on Day -1 relative to inoculation and then administered drug daily throughout the 14-day experimental period. Treatment was initiated on Day 2 postinfection and continued through Day 14 consisting of: 50 mg/kg APX2039 PO (BID), 80 mg/kg fluconazole (FLU) PO (QD), c) 1 mg/kg amphotericin B deoxycholate (AMB) IV (QD); and vehicle control. CSF was removed via an intracisternal tap on Days 2, 7, 10 and 14 post-infection and CFU/ml was assessed. Animals were sacrificed on Day 14 and CFU/g brain tissue was assessed.

Results

APX2039 demonstrated rapid reduction in CFU in both CSF and brain tissue. The range in CFU values in rabbit CSF is shown (Figure). Reductions in CFU were statistically different from the control group for all treatment groups. APX2039 was also different from both FLU and AMB and resulted in sterilization in CSF by Day 10. Brain harvested on Day 14 demonstrated a reduction in CFU/g tissue vs control of 1.8 log₁₀ and 3.4 log₁₀ for FLU and AMB, respectively, while a > 6 log₁₀ reduction (tissue sterilization) was observed for APX2039.

Conclusion

APX2039 demonstrated potent efficacy in a rabbit model of CM. The more rapid clearance in CSF than either AMB or FLU, as well as > 6 log₁₀ reduction in brain CFU highlights the unique properties of this drug, warranting further investigation of this molecule for the treatment of CM.

Disclosures

Karen J. Shaw, PhD, Amplyx (Consultant)Forge Therapeutics (Consultant) Charles D. Giamberardino, Jr., MR, Box (Shareholder) John R. Perfect, MD, amplyx (Grant/Research Support)astellas (Grant/Research Support)astellas (Grant/Research Support)

Novel Treatment of Cryptococcal Meningitis via Neurapheresis Therapy

Cryptococcal meningitis (CM) has emerged as the most common life-threatening fungal meningitis worldwide. Current management involves a sequential, longitudinal regimen of antifungals; despite a significant improvement in survival compared with uniform mortality without treatment, this drug paradigm has not led to a consistent cure. Neurapheresis therapy, extracorporeal filtration of yeasts from cerebrospinal fluid (CSF) in infected hosts, is presented here as a novel, one-time therapy for CM. In vitro filtration of CSF through this platform yielded a 5-log reduction in concentration of the yeast and a 1-log reduction in its polysaccharide antigen over 24 hours. Additionally, an analogous closed-loop system achieved 97% clearance of yeasts from the subarachnoid space in a rabbit model over 4-6 hours. This is the first publication demonstrating the direct ability to rapidly clear, both in vitro and in vivo, the otherwise slowly removed fungal pathogen that directly contributes to the morbidity and mortality seen in CM.

Increased Nitric Oxide Production Prevents Airway Hyperresponsiveness in Caveolin-1 Deficient Mice Following Endotoxin Exposure

BACKGROUND

Caveolin-1, the hallmark protein of caveolae, is highly expressed within the lung in the epithelium, endothelium, and in immune cells. In addition to its classical roles in cholesterol metabolism and endocytosis, caveolin-1 has also been shown to be important in inflammatory signaling pathways. In particular, caveolin-1 is known to associate with the nitric oxide synthase enzymes, downregulating their activity. Endotoxins, which are are composed mainly of lipopolysaccharide (LPS), are found ubiquitously in the environment and can lead to the development of airway inflammation and increased airway hyperresponsiveness (AHR).

METHODS

We compared the acute responses of wild-type and caveolin-1 deficient mice after LPS aerosol, a well-accepted mode of endotoxin exposure, to investigate the role of caveolin-1 in the development of environmental lung injury.

RESULTS

Although the caveolin-1 deficient mice had greater lung inflammatory indices compared to wild-type mice, they exhibited reduced AHR following LPS exposure. The uncoupling of inflammation and AHR led us to investigate the role of caveolin-1 in the production of nitric oxide, which is known to act as a bronchodilator. The absence of caveolin-1 resulted in increased nitrite levels in the lavage fluid in both sham and LPS treated mice. Additionally, inducible nitric oxide synthase expression was increased in the lung tissue of caveolin-1 deficient mice following LPS exposure and administration of the potent and specific inhibitor 1400W increased AHR to levels comparable to wild-type mice.

CONCLUSIONS

We attribute the relative airway hyporesponsiveness in the caveolin-1 deficient mice after LPS exposure to the specific role of caveolin-1 in mediating nitric oxide production.