VT-1161 Protects Immunosuppressed Mice from Rhizopus arrhizus var. arrhizus Infection

Abstract

We studied the efficacy of the investigational drug VT-1161 against mucormycosis. VT-1161 had more potent in vitro activity against Rhizopus arrhizus var. arrhizus than against R. arrhizus var. delemar. VT-1161 treatment demonstrated dose-dependent plasma drug levels with prolonged survival time and lowered tissue fungal burden in immunosuppressed mice infected with R. arrhizus var. arrhizus and was as effective as high-dose liposomal amphotericin B treatment. These results support further development of VT-1161 against mucormycosis. Mucormycoses are infections afflicting the immunocompromised host and are occurring with increasing frequency (1-3). Risk factors for mucormycosis include a compromised immune status due to hematologic malignancies, neutropenia, steroid treatment, hyperglycemia, ketoacidosis and other forms of acidosis, deferoxamine therapy, and trauma (4-6). Despite disfiguring surgical debridement and adjunctive antifungal therapy, the overall mortality of mucormycosis remains at ϳ50% and can approach 100% in certain patient populations (2, 7-11). Clearly, new strategies to prevent and treat mucormycosis are urgently needed.VT-1161 is a novel, fungal-specific 14␣-lanosterol demethylase (CYP51) inhibitor with potent activity against yeasts and dermatophytes (12). VT-1161 uses a 1-tetrazole to bind the heme iron within CYP51, which is critical in establishing greater selectivity for fungal CYP51 versus off-target human cytochrome P 450 (CYP) (13). We investigated the activity of VT-1161 against fungi that cause mucormycosis (Mucorales) in vitro and in vivo. Because Rhizopus species are the most common Mucorales isolated from patients with mucormycosis (8,14,15), these studies focused on R. arrhizus var. arrhizus (also known as R. oryzae) and R. arrhizus var. delemar (also known as R. delemar) (16).The MIC (defined as the lowest concentration that causes 100% growth inhibition relative to the drug-free growth control) of VT-1161 was determined against seven clinical isolates of R. arrhizus var. arrhizus (lactic acid producers) and five clinical isolates of R. arrhizus var. delemar (fumaric acid producers) using the Clinical Laboratory and Standards Institute (CLSI) M38-A2 method (17). The VT-1161 median MICs were 0.5 g/ml (range, 0.25 to 2 g/ml) and Ͼ32 g/ml (range, 8 to Ͼ32 g/ml) against R. arrhizus var. arrhizus and R. arrhizus var. delemar isolates, respectively (Table 1).To evaluate the efficacy of VT-1161 in treating pulmonary mucormycosis, immunosuppressed mice were intratracheally infected with 2.5 ϫ 10 5 spores of R. arrhizus var. arrhizus 99-892 (a lung isolate with a VT-1161 MIC of 1.0 g/ml) after being sedated with ketamine and xylazine (18). Male ICR mice (23 to 25 g; Taconic Farms, Germantown, NY) were given irradiated feed and sterile water containing 50 g/ml enrofloxacin (Baytril; Bayer) ad libitum to control for bacterial infection. Neutropenia was induced by cyclophosphamide (200 mg/kg intraperitoneal) and cortisone acetate (500 mg/kg subcutaneous) on day Ϫ2 and ϩ3 relative to infect...

Prophylactic Treatment with VT-1161 Protects Immunosuppressed Mice from Rhizopus arrhizus var. arrhizus Infection

“…1. Consistent with historical data (14,15), 90% of placebo-treated mice died within 2 weeks of infection. Prophylaxis with VT-1161 but not POS protected mice from R. arrhizus var.…”

“…In vitro testing has demonstrated that VT-1161 has intrinsic antifungal activity in the range of 0.12 to 1 g/ml against some molds, particularly against the order Mucorales (e.g., Rhizopus arrhizus var. arrhizus [14] (14). Our objectives in the present study were to measure the in vivo activity of VT-1161 prophylaxis or continuous therapy of murine mucormycosis caused by R. arrhizus var.…”

“…arrhizus and treated with POS on days ϩ1 through ϩ7 (delayed therapy) (15,16). All treatments were given by oral gavage, with VT-1161 administered once daily at 15 mg/kg (14), POS at 30 mg/kg twice daily (15), and 0.5% CMC vehicle once daily.…”

“…Immunosuppressed mice were intratracheally infected with 2.5 ϫ 10 5 spores of R. arrhizus var. arrhizus 99-892 (a lung isolate with a VT-1161 MIC of 0.5 g/ml [14] and a POS MIC of 0.39 g/ml [15,16]) after sedation with isoflurane gas. The primary endpoint for efficacy was the length of time for infected mice to become moribund.…”

The antifungal pipeline: a reality check

“…Following proprietary manipulation of this part of the molecule, compounds have now been developed that have substantially reduced interactions with cytochrome P450 and thus fewer potential drug– drug interactions. This platform has yielded several new compounds: VT-1161 (REFS 104,105), which is in phase II clinical trials for onychomycosis 106 and vaginal candidiasis (NCT02267356 and NCT02267382), and a very potent anti-cryptococcal compound, VT-1129, which has outstanding efficacy in vitro and in animal models 107 . Finally, in their portfolio is VT-1598, which is a potent azole, with activity against endemic mycosis (see the Business Wire press release ) and cryptococcosis.…”