The binding and cytochrome P45051 (CYP51) inhibition properties of a novel antifungal compound, VT-1161, against purified recombinant Candida albicans CYP51 (ERG11) and Homo sapiens CYP51 were ...compared with those of clotrimazole, fluconazole, itraconazole, and voriconazole. VT-1161 produced a type II binding spectrum with Candida albicans CYP51, characteristic of heme iron coordination. The binding affinity of VT-1161 for Candida albicans CYP51 was high (dissociation constant Kd, ≤ 39 nM) and similar to that of the pharmaceutical azole antifungals (Kd, ≤ 50 nM). In stark contrast, VT-1161 at concentrations up to 86 μM did not perturb the spectrum of recombinant human CYP51, whereas all the pharmaceutical azoles bound to human CYP51. In reconstitution assays, VT-1161 inhibited Candida albicans CYP51 activity in a tight-binding fashion with a potency similar to that of the pharmaceutical azoles but failed to inhibit the human enzyme at the highest concentration tested (50 μM). In addition, VT-1161 (MIC = 0.002 μg ml(-1)) had a more pronounced fungal sterol disruption profile (increased levels of methylated sterols and decreased levels of ergosterol) than the known CYP51 inhibitor voriconazole (MIC = 0.004 μg ml(-1)). Furthermore, VT-1161 weakly inhibited human CYP2C9, CYP2C19, and CYP3A4, suggesting a low drug-drug interaction potential. In summary, VT-1161 potently inhibited Candida albicans CYP51 and culture growth but did not inhibit human CYP51, demonstrating a >2,000-fold selectivity. This degree of potency and selectivity strongly supports the potential utility of VT-1161 in the treatment of Candida infections.
Vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC) remain major health problems for women. VT-1161, a novel fungal CYP51 inhibitor which has potent antifungal activity against ...fluconazole-sensitive Candida albicans, retained its in vitro potency (MIC50 of ≤0.015 and MIC90 of 0.12 μg/ml) against 10 clinical isolates from VVC or RVVC patients resistant to fluconazole (MIC50 of 8 and MIC90 of 64 μg/ml). VT-1161 pharmacokinetics in mice displayed a high volume of distribution (1.4 liters/kg), high oral absorption (73%), and a long half-life (>48 h) and showed rapid penetration into vaginal tissue. In a murine model of vaginal candidiasis using fluconazole-sensitive yeast, oral doses as low as 4 mg/kg VT-1161 significantly reduced the fungal burden 1 and 4 days posttreatment (P < 0.0001). Similar VT-1161 efficacy was measured when an isolate highly resistant to fluconazole (MIC of 64 μg/ml) but fully sensitive in vitro to VT-1161 was used. When an isolate partially sensitive to VT-1161 (MIC of 0.12 μg/ml) and moderately resistant to fluconazole (MIC of 8 μg/ml) was used, VT-1161 remained efficacious, whereas fluconazole was efficacious on day 1 but did not sustain efficacy 4 days posttreatment. Both agents were inactive in treating an infection with an isolate that demonstrated weaker potency (MICs of 2 and 64 μg/ml for VT-1161 and fluconazole, respectively). Finally, the plasma concentrations of free VT-1161 were predictive of efficacy when in excess of the in vitro MIC values. These data support the clinical development of VT-1161 as a potentially more efficacious treatment for VVC and RVVC.
The
activities of fungal CYP51 inhibitors VT-1161 and VT-1129 were determined for
(
= 34) and
(
= 50).
isolates were screened for FKS gene mutations. All isolates were resistant clinically and/or
to ...at least one standard antifungal compound. VT-1161 and VT-1129 MICs for all isolates were at least 5-fold below achievable human plasma levels for VT-1161. VT-1161 and VT-1129 are promising for the treatment of resistant
and
infections.
Current therapies used to treat dermatophytoses such as onychomycosis are effective but display room for improvement in efficacy, safety, and convenience of dosing. We report here that the ...investigational agent VT-1161 displays potent in vitro antifungal activity against dermatophytes, with MIC values in the range of ≤0.016 to 0.5 μg/ml. In pharmacokinetic studies supporting testing in a guinea pig model of dermatophytosis, VT-1161 plasma concentrations following single oral doses were dose proportional and persisted at or above the MIC values for at least 48 h, indicating potential in vivo efficacy with once-daily and possibly once-weekly dosing. Subsequently, in a guinea pig dermatophytosis model utilizing Trichophyton mentagrophytes and at oral doses of 5, 10, or 25 mg/kg of body weight once daily or 70 mg/kg once weekly, VT-1161 was statistically superior to untreated controls in fungal burden reduction (P < 0.001) and improvement in clinical scores (P < 0.001). The efficacy profile of VT-1161 was equivalent to those for doses and regimens of itraconazole and terbinafine except that VT-1161 was superior to itraconazole when each drug was dosed once weekly (P < 0.05). VT-1161 was distributed into skin and hair, with plasma and tissue concentrations in all treatment and regimen groups ranging from 0.8 to 40 μg/ml (or μg/g), at or above the MIC against the isolate used in the model (0.5 μg/ml). These data strongly support the clinical development of VT-1161 for the oral treatment of onychomycosis using either once-daily or once-weekly dosing regimens.
Annual global deaths from cryptococcal meningitis (CM) are estimated at 180 000 and mortality is as high as 30%, even with optimal therapy. VT-1598 is a novel fungal CYP51 inhibitor with potent ...intrinsic antifungal activity against Cryptococcus. We report here VT-1598's in vivo antifungal activity in a murine model of CM.
Single-dose plasma and brain pharmacokinetics in mice and MIC for Cryptococcus neoformans H99 were determined prior to efficacy studies. Short-course monotherapy and combination doses were explored with the endpoint of brain fungal burden. A survival study was also conducted using monotherapy treatment with fungal burden measured after a 6 day drug washout.
Oral doses of VT-1598 had good plasma and brain exposure and resulted in significant (P < 0.0001) and dose-dependent reductions in brain fungal burden, reaching a 6 log10 reduction. Unlike either positive drug control (fluconazole or liposomal amphotericin B), both mid and high doses of VT-1598 reduced fungal burden to below levels measured at the start of treatment. When VT-1598 was dosed in the survival study, no VT-1598-treated animal succumbed to the infection. Whereas fluconazole showed a 2.5 log10 increase in fungal burden after the 6 day washout, the VT-1598 mid- and high-dose animals showed almost no regrowth (<0.5 log10). In a separate fungal burden study using suboptimal doses of VT-1598 and liposomal amphotericin B to probe for combination effects, each combination had a positive effect relative to corresponding monotherapies.
These pre-clinical in vivo data strongly support clinical investigation of VT-1598 as a novel therapy for this lethal infection.
Aspergillus spp. infections remain a global concern, with ∼30% attributable mortality of invasive aspergillosis (IA). VT-1598 is a novel fungal CYP51 inhibitor designed for exquisite selectivity ...versus human CYP enzymes to achieve a maximal therapeutic index and therefore maximal antifungal efficacy. Previously, its broad-spectrum in vitro antifungal activity was reported. We report here the pharmacokinetics (PK) and pharmacodynamics (PD) of VT-1598 in neutropenic mouse models of IA. The plasma area-under-the-curve (AUC) of VT-1598 increased nearly linearly between 5 and 40 mg/kg after 5 days of QD administration (155 and 1033 μg*h/ml, respectively), with a further increase with 40 mg/kg BID dosing (1354 μg*h/ml). When A. fumigatus isolates with in vitro susceptibilities of 0.25 and 1.0 μg/ml were used in a disseminated IA model, VT-1598 treatment produced no decrease in kidney fungal burden at QD 10 mg/kg, intermediate decreases at QD 20 mg/kg and maximum or near maximum decreases at 40 mg/kg QD and BID. The PK/PD relationships of AUCfree/MIC for 1-log killing for the two strains were 5.1 and 1.6 h, respectively, similar to values reported for approved CYP51 inhibitors. In a survival study where animals were observed for 12 days after the last treatment, survival was 100% at the doses tested (20 and 40 mg/kg QD), and fungal burden remained suppressed even though drug wash-out was complete. Similar dose-dependent reductions in lung fungal burden were observed in a pulmonary model of IA. These data strongly support further exploration of VT-1598 for the treatment of this lethal mold infection.
Abstract
Background
Aldosterone is an important mediator of hypertension, particularly resistant hypertension, heart failure, and chronic kidney disease. PB6440 is a potent inhibitor of aldosterone ...synthase (CYP11B2) with high selectivity over the closely related enzyme CYP11B1. In previous studies in cynomolgus monkeys, PB6440 exhibited excellent oral bioavailability and a marked suppression of aldosterone synthesis at doses as low as 1 mg/kg/day. Importantly, no effect was observed on cortisol production nor significant changes noted in plasma concentrations of the steroid precursors 11-deoxycortisol or deoxycorticosterone (DOC), which are dependent on CYP11B1 activity. The purpose of the current study was to assess the safety and pharmacodynamics of higher doses of PB6440 in the cynomolgus monkey in order to determine a therapeutic index prior to initiation of studies in humans.
Methods
Male and female cynomolgus monkeys (2/sex/dose group) were administered 0, 10, 30 or 100 mg/kg PB6440 once-daily for 14 days by oral gavage. Assessment of safety was based on mortality, clinical observations, body weights, and clinical and anatomic pathology. Blood samples were also collected for pharmacodynamic analysis, including aldosterone, cortisol, 11-deoxycortisol, DOC, and ACTH.
Results
PB6440 was well tolerated at all doses. There were no deaths and no reports of clinical observations at any dose level. Mild decreases in body weight were observed in PB6440-treated animals, which were likely due to the diuretic effects of the compound. PB6440 caused an increase in adrenal weights which was associated with hypertrophy of the adrenal zona fasciculata, a finding which has previously been observed with other aldosterone synthase inhibitors. PB6440 led to marked declines in basal aldosterone levels of −97%, −97% and −98% from baseline at 10, 30 and 100 mg/kg/day, respectively, at 24-hours following the final dose. Despite these clear declines in circulating aldosterone levels, no meaningful changes in cortisol, 11-deoxycortisol, DOC, or ACTH levels were observed, supporting lack of CYP11B1 inhibition. PB6440 led to expected decreases in plasma sodium (up to 7 nmol/L at the high dose). No effect on plasma potassium levels were observed at any dose level.
Conclusions
PB6440 was well tolerated in the cynomolgus monkey at doses that are much higher than needed for potent aldosterone suppression based on previous studies. At the highest dose level tested (100 mg/kg), which led to a 98% reduction in basal aldosterone levels, no evidence of significant CYP11B1 inhibition was observed. The absence of an increase in plasma potassium in the presence of a plasma sodium decline merits further study. Thus, PB6440 is a highly selective novel aldosterone synthase inhibitor for the potential treatment of hypertension, heart failure, and chronic kidney disease in humans.
Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): PhaseBio Pharmaceuticals Inc.
While the orally-active azoles such as voriconazole and itraconazole are effective antifungal agents, they potently inhibit a broad range of off-target human cytochrome P450 enzymes (CYPs) leading to ...various safety issues (e.g., drug-drug interactions, liver toxicity). Herein, we describe rationally-designed, broad-spectrum antifungal agents that are more selective for the target fungal enzyme, CYP51, than related human CYP enzymes such as CYP3A4. Using proprietary methodology, the triazole metal-binding group found in current clinical agents was replaced with novel, less avid metal-binding groups in concert with potency-enhancing molecular scaffold modifications. This process produced a unique series of fungal CYP51-selective inhibitors that included the oral antifungal 7d (VT-1161), now in Phase 2 clinical trials. This series exhibits excellent potency against key yeast and dermatophyte strains. The chemical methodology described is potentially applicable to the design of new and more effective metalloenzyme inhibitor treatments for a broad array of diseases.
Abstract
Background
Acute vulvovaginal candidiasis (VVC) is common among women, but current azole antifungal treatments are often associated with safety and resistance issues. VT-1161 (oteseconazole) ...is an oral agent with increased selectivity for fungal CYP51. In this phase 2 clinical study, we evaluated the efficacy and safety of VT-1161 vs fluconazole in participants with moderate to severe acute VVC.
Methods
Participants presenting with an acute episode of VVC (n = 55) were randomized to receive VT-1161 300 mg once daily (q.d.) for 3 days, 600 mg q.d. for 3 days, or 600 mg twice daily (b.i.d.) for 3 days or to receive a single dose of fluconazole 150 mg (FDA-approved dose to treat acute VVC). Participants were followed for 6 months. The primary outcome was the proportion of participants with therapeutic (clinical and mycological) cure at day 28.
Results
A larger proportion of participants in the per-protocol population experienced therapeutic cure in the VT-1161 300 mg q.d. (75.0%), VT-1161 600 mg q.d. (85.7%), and VT-1161 600 mg b.i.d. (78.6%) groups vs the fluconazole group (62.5%); differences were not statistically significant. At 3 and 6 months, no participants in the VT-1161 groups vs 28.5% and 46.1% in the fluconazole group, respectively, had evidence of mycological recurrence. No serious adverse events or treatment-emergent adverse events leading to discontinuation were reported.
Conclusions
The majority of participants across all treatment groups achieved therapeutic cure at day 28. VT-1161 was well tolerated at all dose levels through 6 months of follow-up.
Clinical Trials Registration
NCT01891331.
Lanosterol demethylase is an enzyme that is essential for fungal growth and catalyzes an early step in the biosynthetic pathway of ergosterol, which is a sterol that is required for fungal cell ...membrane formation and integrity. Lanosterol demethylase is the molecular target of the class of drugs referred to as “azole antifungals.” VT-1161 is a novel, oral, selective inhibitor of fungal lanosterol demethylase and is being developed for the treatment of recurrent vulvovaginal candidiasis.
We evaluated the efficacy and safety of 4 dosing regimens of oral VT-1161 compared with placebo in women with recurrent vulvovaginal candidiasis, which was defined as at least 3 symptomatic episodes of acute vulvovaginal candidiasis within a 12-month period.
Two hundred fifteen women with a documented history of recurrent vulvovaginal candidiasis and who, at screening, were experiencing an episode of acute vulvovaginal candidiasis (acute vulvovaginal candidiasis; composite vulvovaginal signs and symptoms score of ≥3 and a positive potassium hydroxide test for yeast) were enrolled. After treatment of the acute infection with fluconazole, subjects were assigned randomly to 1 of 5 treatment regimens: (1) VT-1161 150 mg once daily for 7 days, then 150 mg once weekly for 11 weeks, followed by a once-weekly dose of placebo for 12 weeks; (2) VT-1161 300 mg once daily for 7 days, then 300 mg once weekly for 11 weeks, followed by a once-weekly dose of placebo for 12 weeks; (3) VT-1161 150 mg once daily for 7 days, then 150 mg once weekly for 23 weeks; (4) VT-1161 300 mg once daily for 7 days, then 300 mg once weekly for 23 weeks; or (5) a matching placebo regimen for 24 weeks. The primary efficacy outcome was the proportion of subjects with ≥1 culture-verified acute vulvovaginal candidiasis episodes through week 48.
In the intent-to-treat population, the proportion of subjects with ≥1 acute vulvovaginal candidiasis episodes ranged from 0–7% across the 4 VT-1161 arms vs 52% in the placebo arm, with all arms achieving statistical significance vs placebo. VT-1161 was well-tolerated with a favorable safety profile, and the incidence of adverse events was lower in all VT-1161 arms compared with placebo. In addition, no patient in any VT-1161 arm discontinued the study early because of an adverse event or laboratory abnormality. There was also no evidence of an adverse effect of VT-1161 on liver function or electrocardiogram recordings.
In this study, VT-1161 was shown to be efficacious and safe in the treatment of patients with recurrent vulvovaginal candidiasis. These data strongly support further clinical investigation of VT-1161 for the treatment of recurrent vulvovaginal candidiasis.
PDF
