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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., In a phase 2 randomized clinical study, VT-1161, a novel antifungal agent, was shown to be safe and efficacious in women with acute vaginal candidiasis.

[Image: see text] Excess aldosterone production and signaling are primary contributors to numerous cardiovascular disorders including primary aldosteronism and resistant hypertension. Recently, inhibition of aldosterone synthesis via the enzyme aldosterone synthase (CYP11B2) has been pursued to ameliorate the negative effects of elevated aldosterone. Herein, we report the development of aldosterone synthase inhibitors using a pyrimidine-based metal binding group leading to the highly selective CYP11B2 inhibitor 22. Superior selectivity combined with robust pharmacokinetics afforded highly selective in vivo aldosterone suppression in a monkey model of adrenal steroidogenesis, demonstrating the potential for selective aldosterone lowering in humans with pyrimidine 22.

While the orally-active azoles such as fluconazole and posaconazole 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, and reproductive toxicities). Recently we described the rationally-designed, antifungal agent VT-1161 that is more selective for fungal CYP51 than related human CYP enzymes such as CYP3A4. Herein, we describe the use of a homology model of Aspergillus fumigatus to design and optimize a novel series of highly selective, broad spectrum fungal CYP51 inhibitors. This series includes the oral antifungal VT-1598 that exhibits excellent potency against yeast, dermatophyte, and mold fungal pathogens.

With some advances in modern medicine (such as cancer chemotherapy, broad exposure to antibiotics, and immunosuppression), the incidence of opportunistic fungal pathogens such as Candida albicans has increased. Cases of drug resistance among these pathogens have become more frequent, requiring the development of new drugs and a better understanding of the targeted enzymes. Sterol 14α-demethylase (CYP51) is a cytochrome P450 enzyme required for biosynthesis of sterols in eukaryotic cells and is the major target of clinical drugs for managing fungal pathogens, but some of the CYP51 key features important for rational drug design have remained obscure. We report the catalytic properties, ligand-binding profiles, and inhibition of enzymatic activity of C. albicans CYP51 by clinical antifungal drugs that are used systemically (fluconazole, voriconazole, ketoconazole, itraconazole, and posaconazole) and topically (miconazole and clotrimazole) and by a tetrazole-based drug candidate, VT-1161 (oteseconazole: (R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol). Among the compounds tested, the first-line drug fluconazole was the weakest inhibitor, whereas posaconazole and VT-1161 were the strongest CYP51 inhibitors. We determined the X-ray structures of C. albicans CYP51 complexes with posaconazole and VT-1161, providing a molecular mechanism for the potencies of these drugs, including the activity of VT-1161 against Candida krusei and Candida glabrata, pathogens that are intrinsically resistant to fluconazole. Our comparative structural analysis outlines phylum-specific CYP51 features that could direct future rational development of more efficient broad-spectrum antifungals.

VT-1161 and VT-1598 are promising investigational tetrazole antifungals that have shown in vitro and in vivo activity against Candida and other fungi. Candida glabrata is a problematic opportunistic pathogen that is associated with high mortality in invasive infection, as well as both intrinsic and rapidly acquired antifungal resistance. The MICs of VT-1161 and VT-1598 were determined by CLSI methodology to evaluate their in vitro activities against clinical C. glabrata isolates and strains containing individual deletions of the zinc cluster transcription factor genes PDR1 and UPC2A as well as the efflux transporter genes CDR1, PDH1, and SNQ2. Overall, both tetrazoles demonstrated relative activities comparable to those of the tested triazole antifungals against clinical C. glabrata isolates (MIC range, 0.25 to 2 mg/liter and 0.5 to 2 μg/ml for VT-1161 and VT-1598, respectively). Deletion of the PDR1 gene in fluconazole-resistant matched clinical isolate SM3 abolished the decreased susceptibility phenotype completely for both VT-1161 and VT-1598, similarly to the triazoles. UPC2A deletion also increased susceptibility to both triazoles and tetrazoles but to a lesser extent than PDR1 deletion. Of the three major transporter genes regulated by Pdr1, CDR1 deletion resulted in the largest MIC reductions for all agents tested, while PDH1 and SNQ2 deletion individually impacted MICs very little. Overall, both VT-1161 and VT-1598 have comparable activities to those of the available triazoles, and decreased susceptibility to these tetrazoles in C. glabrata is driven by many of the same known resistance mechanisms.

The fungal Cyp51-specific inhibitors VT-1161 and VT-1598 have emerged as promising new therapies to combat fungal infections, including Candida spp. To evaluate their in vitro activities compared to other azoles, MICs were determined by Clinical and Laboratory Standards Institute (CLSI) method for VT-1161, VT-1598, fluconazole, voriconazole, itraconazole, and posaconazole against 68 C. albicans clinical isolates well characterized for azole resistance mechanisms and mutant strains representing individual azole resistance mechanisms. VT-1161 and VT-1598 demonstrated potent activity (geometric mean MICs ≤0.15 μg/ml) against predominantly fluconazole-resistant (≥8 μg/ml) isolates. However, five of 68 isolates exhibited MICs greater than six dilutions (>2 μg/ml) to both tetrazoles compared to fluconazole-susceptible isolates. Four of these isolates likewise exhibited high MICs beyond the upper limit of the assay for all triazoles tested. A premature stop codon in ERG3 likely explained the high-level resistance in one isolate. VT-1598 was effective against strains with hyperactive Tac1, Mrr1, and Upc2 transcription factors and against most ERG11 mutant strains. VT-1161 MICs were elevated compared to the control strain SC5314 for hyperactive Tac1 strains and two strains with Erg11 substitutions (Y132F and Y132F&K143R) but showed activity against hyperactive Mrr1 and Upc2 strains. While mutations affecting Erg3 activity appear to greatly reduce susceptibility to VT-1161 and VT-1598, the elevated MICs of both tetrazoles for four isolates could not be explained by known azole resistance mechanisms, suggesting the presence of undescribed resistance mechanisms to triazole- and tetrazole-based sterol demethylase inhibitors.

Primary aldosteronism (PA) is a common form of secondary hypertension driven by the autonomous production of aldosterone. Often described as low-renin hypertension, PA is a major public health concern given its prevalence and associated cardiovascular and renal pathology. Compared to patients with essential hypertension, patients with PA are at greater risk for stroke, coronary artery disease, atrial fibrillation, and heart failure. Aldosterone excess is also linked to vascular inflammation, fibrosis and oxidative stress. Aldosterone is produced in the adrenal glands by the enzyme CYP11B2 (aldosterone synthase). CYP11B2 belongs to the cytochrome P450 family of enzymes that also control cortisol (CYP11B1) and sex steroid synthesis (e.g. CYP17, CYP19). Thus, to safely suppress aldosterone synthesis in states of excess, a selective CYP11B2 inhibitor is required. SE-6440 is a novel CYP11B2 inhibitor; it is >200-fold selective over the closely related CYP11B1 enzyme as well as related adrenal and liver cytochrome P450 enzymes. Herein we describe the pharmacology of SE-6440 in non-human primate models of steroidogenesis using two different physiological inducers of aldosterone synthesis (Angiotensin II and ACTH). In monkeys, an i.v. bolus of Angiotensin II stimulates aldosterone synthesis and transiently elevates plasma aldosterone levels. Single oral doses of SE-6440 at 1 and 0.2 mg/kg suppressed aldosterone production in a dose-related manner to 3% and 26% that of vehicle-treated animals, respectively, without effect on cortisol synthesis. To determine if this selective inhibitory effect on aldosterone was durable, we dosed monkeys for 14-days with SE-6440 at 0.6 and 0.12 mg/kg orally once daily. Prior to SE-6440 treatment, animals received an i.v. bolus of ACTH to stimulate adrenal steroidogenesis. This ACTH stimulation test mimics that used clinically to diagnose adrenal insufficiency. Following ACTH administration, plasma aldosterone and cortisol pathway steroids were then measured for 8 hours. Each animal was used as its own control when ACTH was similarly administered on day 7 and day 14 of treatment with SE-6440. SE-6440 reduced plasma aldosterone levels, relative to pre-treatment levels, in a dose-related manner. The 0.6 mg/kg dose significantly inhibited aldosterone synthesis and yielded plasma aldosterone levels 13% and 15% that of control on days 7 and 14, respectively, while the 0.12 mg/kg daily dose reduced plasma aldosterone levels to 46% and 49% that of control on days 7 and 14, respectively. In both dose groups, there was no inhibition of CYP11B1 enzyme activity, based on the plasma cortisol, deoxycortisol, and DOC concentrations. These data demonstrate that, regardless of the stimulus, SE-6440 selectively inhibits aldosterone formation without affecting cortisol synthesis and that this inhibition is durable when administered orally once daily for 14 days.

Candida auris is an emerging pathogen associated with significant mortality and often multidrug resistance. VT-1598, a tetrazole-based fungal CYP51-specific inhibitor, was evaluated in vitro and in vivo against C. auris. Susceptibility testing was performed against 100 clinical isolates of C. auris by broth microdilution. Neutropenic mice were infected intravenously with C. auris, and treatment began 24 h postinoculation with a vehicle control, oral VT-1598 (5, 15, and 50 mg/kg of body weight once daily), oral fluconazole (20 mg/kg once daily), or intraperitoneal caspofungin (10 mg/kg once daily), which continued for 7 days. Fungal burden was assessed in the kidneys and brains on day 8 in the fungal burden arm and on the days the mice succumbed to infection or on day 21 in the survival arm. VT-1598 plasma trough concentrations were also assessed on day 8. VT-1598 demonstrated in vitro activity against C. auris, with a mode MIC of 0.25 μg/ml and MICs ranging from 0.03 to 8 μg/ml. Treatment with VT-1598 resulted in significant and dose-dependent improvements in survival (median survival, 15 and >21 days for VT-1598 at 15 and 50 mg/kg, respectively) and reductions in kidney and brain fungal burden (reductions of 1.88 to 3.61 log10 CFU/g) compared to the control (5 days). The reductions in fungal burden correlated with plasma trough concentrations. Treatment with caspofungin, but not fluconazole, also resulted in significant improvements in survival and reductions in fungal burden compared to those with the control. These results suggest that VT-1598 may be a future option for the treatment of invasive infections caused by C. auris.

TPS5090 Background: PRL-02 is a long-acting IM formulation of a lipophilic abiraterone prodrug being developed for the treatment of patients with metastatic castration-sensitive (mCSPC) and metastatic castration-resistant prostate cancer (mCRPC). In nonclinical models, PRL-02 has a longer effective half-life and duration of action compared to oral abiraterone acetate (AA), due to slow release of the prodrug into circulation. PRL-02 is expected to provide greater abiraterone bioavailability and less variability in pharmacokinetics than oral AA. Based upon results in non-human primate models, PRL-02 should provide efficacy (e.g., testosterone [T] suppression) comparable to oral AA, but with lower abiraterone peak plasma concentrations and overall exposures, potentially leading to a superior therapeutic index and safety profile. The current trial is a phase 1/2a, open-label, dose escalation and subsequent dose expansion study of PRL-02 in men with metastatic prostate cancer. Study Objectives: The primary objective of this study is to determine a recommended phase 2 dose (RP2D) of PRL-02 that provides adequate T suppression up to 84 days. The secondary objectives of this study include the evaluation of safety and tolerability, the pharmacokinetic profile following IM administration and the pharmacodynamic effects of PRL-02. Methods: The phase 1 portion (Dose Escalation) is a standard 3+3 design intended to identify a RP2D that adequately suppresses T up to 84 days. The phase 2a portion (Dose Expansion) will confirm the safety, tolerability and pharmacodynamic effects of the RP2D. Main inclusion criteria are orchiectomy or ongoing GnRH analogue therapy for at least 3 months and a screening T level 2 ng/dL. Prior treatment with abiraterone (or any other CYP17 inhibitor) and current treatment with enzalutamide or any other AR blocking agents are excluded. Patients will undergo scheduled periodic assessments of T levels. Patients may remain on study unless their T is >1 ng/dL on two sequential determinations starting on Day 28 through Day 77 of the first dosing cycle. In phase 1, three patients will initially be enrolled at each dose. The starting dose is 180 mg (i.e., 1.0 mL of PRL-02) and dose escalation will proceed with a modified Fibonacci sequence. If none of the patients in a cohort experience a dose-limiting toxicity (DLT), the dose will be escalated in the next cohort of 3 patients. A DLT is defined as a drug-related Grade 3 or higher toxicity on the Common Terminology Criteria for Adverse Events v5.0, or meets drug-induced liver injury criteria, occurring during the first 28 days following the first dose. In phase 2a, 12 mCSPC and 12 mCRPC patients will be enrolled to receive up to 4 cycles of PRL-02 at the RP2D. The results of this phase 1/2a study will be presented at a future ASCO conference. Clinical trial information: NCT04729114.

The in vitro activities of the novel fungal Cyp51 inhibitor VT-1129 were evaluated against a large panel of Cryptococcus neoformans and Cryptococcus gattii isolates. VT-1129 demonstrated potent activities against both Cryptococcus species as demonstrated by low MIC 50 and MIC 90 values. For C. gattii , the in vitro potency was maintained against all genotypes. In addition, significantly lower geometric mean MICs were observed for VT-1129 than for fluconazole against C. neoformans , including isolates with reduced fluconazole susceptibility.

78 Background: Oral abiraterone acetate (AA) is a standard of care for castration-resistant (CRPC) and castration-sensitive prostate cancer (CSPC). Due to poor oral bioavailability, the recommended AA dose is 1,000 mg (4 x 250mg) once-daily on an empty stomach. The daily oral regimen produces high peak plasma concentrations that may be associated with safety issues (e.g., hepatotoxicity) and low trough concentrations that may be associated with inadequate CYP17 inhibition. AD is one of a series of novel abiraterone prodrugs that were designed to provide a controlled release of abiraterone and long-acting CYP17 inhibition with IM delivery. Following successful preclinical pilot studies, AD was further developed into a clinically acceptable formulation (PRL-02) and its PK/PD characteristics were evaluated and compared to oral AA in a castrate monkey pharmacology model in support of future clinical development. Methods: Sexually mature male cynomolgus monkeys underwent chemical castration using Lupron depot. Plasma samples were analyzed for prodrug, abiraterone and steroid concentrations following a single oral AA dose (5, 15 or 45 mg/kg) and a single IM AD injection (10, 30 or 100 mg/kg) (n=3/dose group). The combined activity of IM AD plus glucocorticoid replacement (single 0.5 mg/kg IM dexamethasone (DEX) dose or weekly doses of 1.29 mg/kg IM methylprednisolone acetate (MPA)) was also evaluated. AD, abiraterone and adrenal steroid levels were evaluated by LC-MS/MS. Results: Chemical castration resulted in a plasma testosterone (T) decrease of 72% from intact. T was further reduced to sub-castrate levels by both AA and AD (98.6% and 99.7% maximum decrease from castrate baseline, respectively). All dose levels of AD were highly effective in reducing plasma T yet led to abiraterone plasma concentrations (Cmax, AUC, Cmin) that were much less than those associated with steady-state clinical levels from oral AA. Sustained T suppression was observed following all single AD IM doses for 14 weeks, the last timepoint tested.The addition of a glucocorticoid replacement (DEX or MPA) starting at week 9 further reduced T in all AD groups. Conclusions: Single-dose IM AD suppressed T to the same or greater extent than single-dose oral AA in castrate monkeys, while providing much lower abiraterone exposures than the oral acetate prodrug. As such, IM AD may offer an improved risk-benefit profile due to the consistently lower abiraterone levels. The durable, profound T reductions provided by all AD doses are consistent with a 3-month clinical regimen that can be given in conjunction with Lupron. IM AD may thus offer patients with CSPC and CRPC a more convenient, safe and effective alternative than daily oral AA.

VT-1129 is a novel fungal enzyme-specific Cyp51 inhibitor with potent cryptococcal activity. Because of its long half-life (>6 days in mice) and our desire to quickly reach potent efficacy, we evaluated a VT-1129 loading dose-maintenance dose strategy against cryptococcal meningitis. VT-1129 plasma and brain pharmacokinetics were first studied in healthy mice, and these data were used to model loading dose-maintenance dose regimens to generate different steady-state concentrations. Mice were inoculated intracranially with Cryptococcus neoformans, and oral treatment began 1 day later. Treatment consisted of placebo or one of three VT-1129 loading dose-maintenance dose regimens, i.e., loading dose of 1, 3, or 30 mg/kg on day 1, followed by once-daily maintenance doses of 0.15, 0.5, or 5 mg/kg, respectively. In the fungal burden arm, therapy continued for 14 days and brains were collected on day 15 for fungal burden assessments. In the survival arm, treatment continued for 10 days, after which mice were monitored without therapy until day 30. VT-1129 plasma and brain concentrations were also measured. All VT-1129 doses significantly improved survival and reduced fungal burdens, compared to placebo. VT-1129 plasma and brain levels correlated with fungal burden reductions (R(2) = 0.72 and R(2) = 0.67, respectively), with a plasma concentration of 1 μg/ml yielding a reduction of ∼5 log(10) CFU/g. With the highest loading dose-maintenance dose regimen, fungal burdens were undetectable in one-half of the mice in the fungal burden arm and in one-fourth of the mice in the survival arm, 20 days after the final dose. These data support a loading dose-maintenance dose strategy for quickly reaching highly efficacious VT-1129 concentrations for treating cryptococcal meningitis.

Candida auris is an emerging pathogen associated with significant mortality and often multidrug resistance. VT-1598, a tetrazole-based fungal CYP51-specific inhibitor, was evaluated in vitro and in vivo against C. auris. Susceptibility testing was performed against 100 clinical isolates of C. auris by broth microdilution. Neutropenic mice were infected intravenously with C. auris, and treatment began 24 h postinoculation with a vehicle control, oral VT-1598 (5, 15, and 50 mg/kg of body weight once daily), oral fluconazole (20 mg/kg once daily), or intraperitoneal caspofungin (10 mg/kg once daily), which continued for 7 days. Fungal burden was assessed in the kidneys and brains on day 8 in the fungal burden arm and on the days the mice succumbed to infection or on day 21 in the survival arm. VT-1598 plasma trough concentrations were also assessed on day 8. VT-1598 demonstrated in vitro activity against C. auris, with a mode MIC of 0.25 μg/ml and MICs ranging from 0.03 to 8 μg/ml. Treatment with VT-1598 resulted in significant and dose-dependent improvements in survival (median survival, 15 and >21 days for VT-1598 at 15 and 50 mg/kg, respectively) and reductions in kidney and brain fungal burden (reductions of 1.88 to 3.61 log(10) CFU/g) compared to the control (5 days). The reductions in fungal burden correlated with plasma trough concentrations. Treatment with caspofungin, but not fluconazole, also resulted in significant improvements in survival and reductions in fungal burden compared to those with the control. These results suggest that VT-1598 may be a future option for the treatment of invasive infections caused by C. auris.

Cryptococcal meningitis is a significant cause of morbidity and mortality in immunocompromised patients. VT-1129 is a novel fungus-specific Cyp51 inhibitor with potent in vitro activity against Cryptococcus species. Our objective was to evaluate the in vivo efficacy of VT-1129 against cryptococcal meningitis. Mice were inoculated intracranially with Cryptococcus neoformans. Oral treatment with VT-1129, fluconazole, or placebo began 1 day later and continued for either 7 or 14 days, and brains and plasma were collected on day 8 or 15, 1 day after therapy ended, and the fungal burden was assessed. In the survival study, treatment continued until day 10 or day 28, after which mice were monitored off therapy until day 30 or day 60, respectively, to assess survival. The fungal burden was also assessed in the survival arm. VT-1129 plasma and brain concentrations were also measured. VT-1129 reached a significant maximal survival benefit (100%) at a dose of 20 mg/kg of body weight once daily. VT-1129 at doses of ≥0.3 mg/kg/day and each dose of fluconazole significantly reduced the brain tissue fungal burden compared to that in the control after both 7 and 14 days of dosing. The fungal burden was also undetectable in most mice treated with a dose of ≥3 mg/kg/day, even ≥20 days after dosing had stopped, in the survival arm. In contrast, rebounds in fungal burden were observed with fluconazole. These results are consistent with the VT-1129 concentrations, which remained elevated long after dosing had stopped. These data demonstrate the potential utility of VT-1129 to have a marked impact in the treatment of cryptococcal meningitis.

Background Chronic mucocutaneous candidiasis (CMC) treatment often induces drug resistance, posing long-term challenges. A novel broad-spectrum fungal CYP51 inhibitor, VT-1598, specifically targets fungal CYP51, but not human CYP enzymes. Objectives To determine the efficacy of VT-1598 in the treatment of oral Candida infection caused by fluconazole-susceptible and -resistant clinical isolates. Methods The MICs of VT-1598 and fluconazole for 28 Candida isolates recovered from patients with inherited CMC were determined using CLSI M27-A3 and M27-S4 guidelines. Plasma and tongue VT-1598 or fluconazole concentrations were measured in mice following oral administration to determine tissue distribution. Tongue fungal load was determined in IL-17 signalling-deficient Act1-/- mice following sublingual Candida albicans infection and oral treatment with fluconazole or VT-1598. Results Among the 28 Candida isolates, 10 (36%) had fluconazole MICs of ≥4 mg/L, whereas VT-1598 demonstrated potent in vitro activity against all isolates (MIC90, 0.125 mg/L). After oral administration, VT-1598 levels in mouse plasma and tongue were significantly greater than those of fluconazole. In vivo, VT-1598 exhibited significant efficacy against fluconazole-susceptible and -resistant C. albicans, even at low drug doses. Furthermore, after a 10 day washout period, tongue fungal burdens in fluconazole-treated mice returned to vehicle control levels, whereas, in contrast, they were undetectable in mice treated with VT-1598. Conclusions VT-1598 effectively controls in vitro growth of mucosally derived Candida clinical isolates, including fluconazole-resistant strains. In vivo, VT-1598 eliminates C. albicans, even after a long washout period or at low doses. Therefore, VT-1598 is a promising drug candidate that may significantly improve treatment options for CMC patients.

Coccidioidal meningitis can cause significant morbidity, and lifelong antifungal therapy is often required. VT-1598 is a fungus-specific Cyp51 inhibitor that has potent in vitro activity against Coccidioides species. We evaluated the in vivo efficacy of VT-1598 in murine models of central nervous system coccidioidomycosis caused by C. posadasii and C. immitis . Infection was introduced via intracranial inoculation, and therapy began 48 h postinoculation. Oral treatments consisted of vehicle control, VT-1598, and positive controls of fluconazole in the C. immitis study and VT-1161 in the C. posadasii study. Treatment continued for 7 and 14 days in the fungal-burden and survival studies, respectively. Fungal burden was assessed in brain tissue collected 24 to 48 h posttreatment in the fungal-burden studies, on the days the mice succumbed to infection, or at prespecified endpoints in the survival studies. VT-1598 plasma concentrations were also measured in the C. posadasii study. VT-1598 resulted in significant improvements in survival in mice infected with either species. In addition, the fungal burden was significantly reduced in the fungal-burden studies. Plasma concentrations 48 h after dosing stopped remained above the VT-1598 MIC against the C. posadasii isolate, although levels were undetectable in the survival study after a 4-week washout. Whereas fungal burden remained suppressed after a 2-week washout in the C. immitis model, a higher fungal burden was observed in the survival arm of the C. posadasii model. This in vivo efficacy supports human studies to establish the utility of VT-1598 for the treatment of coccidioidomycosis.

Prior to characterization of antifungal inhibitors that target CYP51, Trichophyton rubrum CYP51 was expressed in Escherichia coli , purified, and characterized. T. rubrum CYP51 bound lanosterol, obtusifoliol, and eburicol with similar affinities (dissociation constant [ K d ] values, 22.7, 20.3, and 20.9 μM, respectively) but displayed substrate specificity, insofar as only eburicol was demethylated in CYP51 reconstitution assays (turnover number, 1.55 min −1 ; K m value, 2 μM). The investigational agent VT-1161 bound tightly to T. rubrum CYP51 ( K d = 242 nM) with an affinity similar to that of clotrimazole, fluconazole, ketoconazole, and voriconazole ( K d values, 179, 173, 312, and 304 nM, respectively) and with an affinity lower than that of itraconazole ( K d = 53 nM). Determinations of 50% inhibitory concentrations (IC 50 s) using 0.5 μM CYP51 showed that VT-1161 was a tight-binding inhibitor of T. rubrum CYP51 activity, yielding an IC 50 of 0.14 μM, whereas itraconazole, fluconazole, and ketoconazole had IC 50 s of 0.26, 0.4, and 0.6 μM, respectively. When the activity of VT-1161 was tested against 34 clinical isolates, VT-1161 was a potent inhibitor of T. rubrum growth, with MIC 50 , MIC 90 , and geometric mean MIC values of ≤0.03, 0.06, and 0.033 μg ml −1 , respectively. With its selectivity versus human CYP51 and drug-metabolizing cytochrome P450s having already been established, VT-1161 should prove to be safe and effective in combating T. rubrum infections in patients.

Background Candida albicans, the most common human fungal pathogen, causes chronic mucosal infections in patients with inborn errors of IL-17 immunity that rely heavily on chronic, often lifelong, azole antifungal agents for treatment. However, a rise in azole resistance has predicated a need for developing new antifungal drugs. Objectives To test the in vitro and in vivo efficacy of VT-1161 and VT-1129 in the treatment of oropharyngeal candidiasis with azole-susceptible or -resistant C. albicans strains. Methods MICs of VT-1161, VT-1129 and nine licensed antifungal drugs were determined for 31 Candida clinical isolates. The drug concentrations in mouse serum and tongues were measured following oral administration. IL-17-signalling-deficient Act1-/- mice were infected with fluconazole-susceptible or fluconazole-resistant C. albicans strains, and the amount of mucosal fungal burden was determined after fluconazole or VT-1161 treatment. Results Fourteen isolates (45%) were not fluconazole susceptible (MIC ≥4 mg/L). VT-1161 and VT-1129 showed significant in vitro activity against the majority of the 31 mucosal clinical isolates (MIC50 0.03 and 0.06 mg/L, respectively), including Candida glabrata (MIC50, 0.125 and 0.25 mg/L, respectively). After oral doses, VT-1161 and VT-1129 concentrations in mouse serum and tongues were well above their MIC50 values. VT-1161 was highly effective as treatment of both fluconazole-susceptible and -resistant oropharyngeal candidiasis in Act1-/- mice. Conclusions VT-1129 and VT-1161 exhibit significant in vitro activity against Candida strains, including fluconazole-resistant C. albicans and C. glabrata. VT-1161 administration in mice results in significant mucosal drug accumulation and eradicates infection caused by fluconazole-susceptible and -resistant Candida strains.

Background VT-1598 is a novel fungal CYP51 inhibitor with potent in vitro activity against yeast, mold, and endemic pathogenic fungi (Wiederhold, JAC, 2017). Its tetrazole-based rational drug design imparts much greater selectivity vs. human CYPs (Yates, BMCL, 2017), which could reduce human CYP-related side effects and DDIs. We report here VT-1598’s in vivo activity in an invasive aspergillosis (IA) model. Methods MIC was determined as outlined in CLSI M38-A2. Plasma PK was measured after 4 days of oral doses in neutropenic ICR mice without fungal inoculation. In vivo antifungal activity was determined in a tail-vein IA model in neutropenic mice inoculated with A. fumigatus (AF) ATCC 204305 (N = 10 per dose). Two separate studies were conducted, with oral VT-1598 treatment starting either 48 hours prior (prophylaxis) or 5 hours postinoculation (delayed), with 4 days of postinoculation dosing, and kidney fungal burden measured 1 day post last dose by both CFU and qPCR. Drug control was 10 mg/kg AmBisome i.v. Results The MIC for VT-1598 against AF 204305 was 0.25 μg/mL. The plasma PK of VT-1598 was linearly proportional between the 5 and 40 mg/kg once-daily doses, with AUCs of 155 and 1,033 μg h/mL for the two doses, respectively. VT-1598 was similarly effective in reducing fungal burden when given in delayed treatment compared with prophylaxis, and both studies demonstrated a full dose–response (i.e., no to full reduction of fungal burden). When comparing fungal burdens of each dose group to the fungal burden at the start of treatment, the dose of VT-1598 to achieve fungal stasis ranged from 20.5 to 25.9 mg/kg and to achieve a 1-log10 fungal kill ranged from 30.9 to 50.5 mg/kg. Using the previously measured mouse plasma binding (>99.9%), the free AUC /MIC values for stasis and 1-log10 kill ranged from 2.1–2.7 and 3.2–5.2, respectively. These values are within the range of 1–11 that have been reported for posaconazole and isavuconazole (Lepak, AAC, 2013). Conclusion VT-1598 had potent antifungal activity in a murine model of IA. The PK/PD relationship was the same as clinically used mold-active CYP51 agents, suggesting that it could have similar clinical efficacy. If correct, the tetrazole-based greater selectivity may significantly differentiate VT-1598 from current IA therapies. Disclosures E. P. Garvey, Viamet Pharmaceuticals, Inc.: Employee, Salary. A. Sharp, Evotec (UK) Ltd.: Employee, Salary. P. Warn, Evotec (UK) Ltd.: Employee, Salary. C. M. Yates, Viamet Pharmaceuticals, Inc.: Employee, Salary. R. J. Schotzinger, Viamet Pharmaceuticals, Inc.: Board Member and Employee, Salary.

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.

We compared prophylactic or continuous therapy with the investigational drug VT-1161 to that with posaconazole in treating murine mucormycosis due to Rhizopus arrhizus var. arrhizus . In the prophylaxis studies, only VT-1161 resulted in improved survival and lowered tissue fungal burden of immunosuppressed infected mice. In the continuous therapy, VT-1161 outperformed posaconazole in prolonging mouse survival time despite its comparable effect in lowering tissue fungal burden. These results support the further development of VT-1161 against mucormycosis.

With some advances in modern medicine (such as cancer chemotherapy, broad exposure to antibiotics, and immunosuppression), the incidence of opportunistic fungal pathogens such as Candida albicans has increased. Cases of drug resistance among these pathogens have become more frequent, requiring the development of new drugs and a better understanding of the targeted enzymes. Sterol 14α-demethylase (CYP51) is a cytochrome P450 enzyme required for biosynthesis of sterols in eukaryotic cells and is the major target of clinical drugs for managing fungal pathogens, but some of the CYP51 key features important for rational drug design have remained obscure. We report the catalytic properties, ligand-binding profiles, and inhibition of enzymatic activity of C. albicans CYP51 by clinical antifungal drugs that are used systemically (fluconazole, voriconazole, ketoconazole, itraconazole, and posaconazole) and topically (miconazole and clotrimazole) and by a tetrazole-based drug candidate, VT-1161 (oteseconazole: (R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol). Among the compounds tested, the first-line drug fluconazole was the weakest inhibitor, whereas posaconazole and VT-1161 were the strongest CYP51 inhibitors. We determined the X-ray structures of C. albicans CYP51 complexes with posaconazole and VT-1161, providing a molecular mechanism for the potencies of these drugs, including the activity of VT-1161 against Candida krusei and Candida glabrata, pathogens that are intrinsically resistant to fluconazole. Our comparative structural analysis outlines phylum-specific CYP51 features that could direct future rational development of more efficient broad-spectrum antifungals.

Coccidioidomycosis can be a chronic, systemic fungal infection requiring long-term to lifetime medication. Thus, there is a need for improved antifungal agents with greater efficacy and reduced toxicity. VT-1161 has a low affinity for mammalian cytochromes and potently inhibits fungal CYP51 with proven efficacy in murine models of central nervous system (CNS) and respiratory coccidioidomycosis. Dogs experience coccidioidomycosis similar to humans and are a useful preclinical model for naturally occurring disease. Twenty-four client-owned dogs diagnosed with respiratory coccidioidomycosis based on radiography, serology, clinical signs, and clinicopathologic abnormalities were treated with a loading dose of VT-1161 for 14 days, followed by 46 days of a lower maintenance dose. Twelve dogs received a high dose (29 mg/kg loading, 6 mg/kg maintenance) and 12 received a low dose (10 mg/kg loading, 1.6 mg/kg maintenance). Response to treatment was assessed by calculating the reduction in disease scores at exit compared to disease scores at enrollment. Overall, 20 of 24 (83%) dogs had ≥50% reduction in enrollment disease scores at exit ( P < 0.001), with no difference between the high- and low-dose groups ( P = 0.66). Time-weighted average plasma concentrations for the high- and low-dose groups were 39 ± 5 μg/ml and 19 ± 2 μg/ml, respectively. In this open-label study, VT-1161 was efficacious for the treatment of respiratory coccidioidomycosis in naturally infected dogs. Combined with previously reported murine data, this finding supports the further development of VT-1161 for the treatment of coccidioidomycosis in humans.

Although antifungal drug resistance in the human fungal pathogen Cryptococcus neoformans is relatively uncommon, fluconazole-resistant strains are problematic for preemptive treatment of cryptococcal antigenemia or during cryptococcal meningitis consolidation therapy. We analyzed activity of the experimental antifungal VT-1129 on 51 clinical Cryptococcus neoformans isolates previously screened for fluconazole resistance; with an emphasis on fluconazole dose-dependent (MIC 16-32 μg/ml) or resistant (MIC ≥ 64 μg/ml) isolates. Overall, the VT-1129 geometric mean MIC was 0.027 μg/ml. The VT-1129 MIC50 was 0.05 μg/ml and 0.25 μg/ml for dose-dependent (n = 27) and resistant isolates (n = 6), respectively. These data suggest VT-1129 shows potential for use against fluconazole-resistant Cryptococcus.

Despite recent advances, disease progression and treatment resistance in multiple myeloma (MM) remains a significant challenge. Current therapies include proteasome inhibitors, immunomodulatory agents, monoclonal antibodies and more recently histone deacetylase (HDAC) inhibitors. Many HDAC inhibitors have progressed into clinical development, however, there has been limited success with the approval of only three pan-HDAC inhibitors (SAHA, belinostat and panobinostat) and the class I selective inhibitor, romidepsin. A challenge to the development of HDAC inhibitors has been the management of toxicities, many of which are dose limiting. Some of these toxicities can be attributed to the use of the hydroxamate, a potent zinc binding group that has been associated with toxicity and poor pharmacokinetic (PK) properties. The very tight binding potency of the hydroxamate to zinc also leads to limited HDAC isoform selectivity and thus further predisposes to toxicity. HDAC6, a member of the class IIb HDAC family, is a target of high interest and has significant therapeutic potential in oncology, particularly MM. It has a unique protein structure and is predominantly located in the cytoplasm where it has multiple non-histone protein substrates including α-tubulin, HSP90, cortactin, and Foxp3. Here, we describe the identification of a highly selective, non-hydroxamate HDAC6 inhibitor with excellent PK properties capable of inhibiting MM growth in vivo. Extensive medicinal chemistry exploration and optimization led to the discovery of a zinc-binding group that was associated with excellent potency and selectivity for HDAC6. Additional optimization of the chemical scaffold led to the identification of SE-7552, a compound with an IC50 of 33nM against HDAC6 and greater than 850-fold selectivity versus all other known HDAC isozymes. SE-7552 demonstrated superior PK compared to hydroxamate-based HDAC inhibitors, with a maximum exposure of 597 ng/ml and a half-life of 7.2 hours after a single oral dose of 5 mg/kg in the mouse. To characterize inhibition of HDAC6 in vivo, acetylated α-tubulin (a biomarker for HDAC6 inhibition) was measured in the spleen of mice treated with SE-7552 or the hydroxamate-based HDAC6 inhibitor, ricolinostat. After a single oral dose of SE-7552 at 30 mg/kg, levels of acetylated α-tubulin were increased for over 24 hours, whereas ricolinostat at a 50 mg/kg IP dose showed increased levels for less than 8 hours. In the same study, SE-7552 had no effect on the acetylation of H3 (a biomarker for inhibition of Class I HDACs), whereas ricolinostat increased the levels of acetylated H3. Based on the positive in vitro and in vivo profile, SE-7552 was progressed into pre-clinical rodent models of MM. Since previously studied HDAC6 inhibitors were not able to significantly inhibit MM growth as monotherapy, SE-7552 was co-administered with either pomalidomide or bortezomib. In a subcutaneous MM model using human H929 MM cells, SE-7552 dosed orally at 10 mg/kg daily in combination with pomalidomide dosed at 1 mg/kg IP daily significantly delayed tumor growth in comparison to pomalidomide alone (p < 0.01), as well as enhanced the survival of the mice. Utilizing human MM.1S cells that can be quantified by luminescence, a disseminated model of MM was conducted in which SE-7552 dosed orally at 10 mg/kg daily in combination with bortezomib dosed at 1.5 mg/kg IP once a week significantly delayed tumor growth compared to bortezomib alone (p < 0.05). In summary, we have identified a non-hydroxamate HDAC6 inhibitor, SE-7552, with superior selectivity and pharmacokinetics compared to current HDAC6 inhibitors. SE-7552 demonstrated high levels of selectivity in an in vivo biomarker study and blocked MM growth in two pre-clinical models when co-administered with current MM therapies. Disclosures Holt: Selenity Therapeutics: Employment, Equity Ownership, Patents & Royalties: METALLOENZYME INHIBITOR COMPOUNDS, U.S. Patent Application No.: 15/917,555 (March 9, 2018). Garvey:Selenity Therapeutics: Employment, Equity Ownership. Becherer:Selenity Therapeutics: Employment, Equity Ownership. Hoekstra:Selenity Therapeutics: Employment, Equity Ownership, Patents & Royalties: METALLOENZYME INHIBITOR COMPOUNDS, U.S. Patent Application No.: 15/917,555 (March 9, 2018). Schotzinger:Mycovia Pharma: Membership on an entity's Board of Directors or advisory committees; Innocrin Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Selenity Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: METALLOENZYME INHIBITOR COMPOUNDS, U.S. Patent Application No.: 15/917,555 (March 9, 2018). Yates:Selenity Therapeutics: Employment, Equity Ownership, Patents & Royalties: METALLOENZYME INHIBITOR COMPOUNDS, U.S. Patent Application No.: 15/917,555 (March 9, 2018).

Background 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. Objective 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. Study Design 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. Results 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. Conclusion 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.

Cryptococcosis is a life-threatening disease often associated with HIV infection. Three Cryptococcus species CYP51 enzymes were purified and catalyzed the 14α-demethylation of lanosterol, eburicol, and obtusifoliol. The investigational agent VT-1129 bound tightly to all three CYP51 proteins (dissociation constant [ K d ] range, 14 to 25 nM) with affinities similar to those of fluconazole, voriconazole, itraconazole, clotrimazole, and ketoconazole ( K d range, 4 to 52 nM), whereas VT-1129 bound weakly to human CYP51 ( K d , 4.53 μM). VT-1129 was as effective as conventional triazole antifungal drugs at inhibiting cryptococcal CYP51 activity (50% inhibitory concentration [IC 50 ] range, 0.14 to 0.20 μM), while it only weakly inhibited human CYP51 activity (IC 50 , ∼600 μM). Furthermore, VT-1129 weakly inhibited human CYP2C9, CYP2C19, and CYP3A4, suggesting a low drug-drug interaction potential. Finally, the cellular mode of action for VT-1129 was confirmed to be CYP51 inhibition, resulting in the depletion of ergosterol and ergosta-7-enol and the accumulation of eburicol, obtusifolione, and lanosterol/obtusifoliol in the cell membranes.

A novel antifungal drug candidate, the 1-tetrazole-based agent VT-1161 [( R )-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1 H -tetrazol-1-yl)-1-{5-[4-(2,2,2-trifluoroethoxy)phenyl]pyridin-2-yl}propan-2-ol], which is currently in two phase 2b antifungal clinical trials, was found to be a tight-binding ligand (apparent dissociation constant [ K d ], 24 nM) and a potent inhibitor of cytochrome P450 sterol 14α-demethylase (CYP51) from the protozoan pathogen Trypanosoma cruzi . Moreover, VT-1161 revealed a high level of antiparasitic activity against amastigotes of the Tulahuen strain of T. cruzi in cellular experiments (50% effective concentration, 2.5 nM) and was active in vivo , causing >99.8% suppression of peak parasitemia in a mouse model of infection with the naturally drug-resistant Y strain of the parasite. The data strongly support the potential utility of VT-1161 in the treatment of Chagas disease. The structural characterization of T. cruzi CYP51 in complex with VT-1161 provides insights into the molecular basis for the compound's inhibitory potency and paves the way for the further rational development of this novel, tetrazole-based inhibitory chemotype both for antiprotozoan chemotherapy and for antifungal chemotherapy.

Coccidioidomycosis, or valley fever, is a growing health concern endemic to the southwestern United States. Safer, more effective, and more easily administered drugs are needed especially for severe, chronic, or unresponsive infections. The novel fungal CYP51 inhibitor VT-1161 demonstrated in vitro antifungal activity, with MIC 50 and MIC 90 values of 1 and 2 μg/ml, respectively, against 52 Coccidioides clinical isolates. In the initial animal study, oral doses of 10 and 50 mg/kg VT-1161 significantly reduced fungal burdens and increased survival time in a lethal respiratory model in comparison with treatment with a placebo ( P < 0.001). Oral doses of 25 and 50 mg/kg VT-1161 were similarly efficacious in the murine central nervous system (CNS) model compared to placebo treatment ( P < 0.001). All comparisons with the positive-control drug, fluconazole at 50 mg/kg per day, demonstrated either statistical equivalence or superiority of VT-1161. VT-1161 treatment also prevented dissemination of infection from the original inoculation site to a greater extent than fluconazole. Many of these in vivo results can be explained by the long half-life of VT-1161 leading to sustained high plasma levels. Thus, the efficacy and pharmacokinetics of VT-1161 are attractive characteristics for long-term treatment of this serious fungal infection.

The orally-active CYP17A1 inhibitor abiraterone acetate (AA) decreases adrenal and intratumoral androgen biosynthesis and is an effective agent for the treatment of prostate cancer. Abiraterone potently inhibits both reactions catalyzed by CYP17, the 17α-hydroxylase (hydroxylase) reaction as well as the 17,20-lyase (lyase) transformation. CYP17 hydroxylase inhibition prevents the synthesis of adrenal glucocorticoids and causes an accumulation of circulating mineralocorticoids. As a consequence of potent CYP17 hydroxylase inhibition (i.e., lack of lyase selectivity), AA must be co-administered with the cortisol replacement prednisone and patients may experience the effects of mineralocorticoid excess syndrome (MES). Herein, we describe rationally-designed, CYP17 lyase-selective inhibitors that could prove safer and more effective than abiraterone. Using proprietary methodology, the high-affinity pyridine or imidazole metal-binding group found in current clinical CYP17 inhibitors was replaced with novel, less avid, metal-binding groups in concert with potency-enhancing molecular scaffold modifications. This process produced a unique series of CYP17 lyase-selective inhibitors that included the oral agent 6 (VT-464), now in Phase 2 prostate cancer clinical trials. The chemical methodology described is potentially applicable to the design of new and more effective metalloenzyme inhibitor treatments for a broad array of diseases.

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.

Background Patients with chronic mucocutaneous candidiasis (CMC) often develop azole-resistant Candida infections, making treatment difficult due to lack of oral antifungal drug options. VT-1598 is a novel broad-spectrum fungal CYP51 inhibitor designed for exquisite selectivity for the fungal target versus human CYP enzymes to circumvent classic azole side effects like drug–drug interactions. We report the efficacy of VT-1598 in the treatment of oral Candida infection (including by azole-resistant strains). Methods The in vitro MIC values of 28 Candida species isolated from patients with CMC due to AIRE mutations were tested against VT-1598 and fluconazole (FLC), using CLSI broth microdilution M27-S4. Plasma VT-1598 levels were measured using LC–MS/MS with electrospray ionization. Tongue fungal load was determined in IL-17 deficient Act1- /- mice following sublingual C. albicans infection and once-daily oral treatment for 4 days with 25 mg/kg FLC or 3.2, 8, and 20 mg/kg VT-1598 starting 18 hours post-infection. Results Among 28 Candida isolates tested (22 C. albicans, three C. glabrata, and one each of C. utilis, C. dubiliensis, and C. krusei), 10 (36%) were not susceptible to FLC, based on CLSI breakpoints (>4 mg/ml). Remarkably, all 28 isolates were highly susceptible to VT-1598 (MIC50 and MIC90, 0.06 and 0.125 mg/ml, respectively). Oral administration of VT-1598 led to mean drug levels in mouse plasma (2.0, 3.0, and 11 mg/ml at the low, mid, and high doses, respectively) that were higher than the MIC values. In vivo, VT-1598 was significantly more effective, compared with FLC, against FLC-susceptible and -resistant C. albicans, and led to elimination of fungal growth even at the lowest tested dose (3.2 mg/kg). After a 10-day washout period from the last dose, mice treated with VT-1598 did not have mucosal fungal growth, while mice treated with FLC had tongue fungal loads similar to vehicle control. Conclusion VT-1598 shows in vitro activity against mucosally derived Candida, including FLC-resistant strains. In vivo, VT-1598 achieves high plasma concentrations and eliminates viable C. albicans, even at low doses and after an extended washout period. These data indicate that VT-1598 may be a significantly improved treatment option for patients with CMC. Disclosures C. M. Yates, Viamet Pharmaceuticals, Inc.: Employee, Salary. O. J. Cohen, Viamet Pharmaceuticals, Inc.: Employee, Salary. R. J. Schotzinger, Viamet Pharmaceuticals, Inc.: Employee, Salary. E. P. Garvey, Viamet Pharmaceuticals, Inc.: Employee, Salary. M. Lionakis, Viamet Pharmaceuticals: Research support (CRADA), Research support

Histochemical, immunocytochemical, and radioenzymatic techniques were used to examine the neurotransmitter-related properties of the innervation of thoracic hairy skin in rats during adulthood and postnatal development. In the adult, catecholamine-containing fibers were associated with blood vessels and piloerector muscles, and ran in nerve bundles throughout the dermis. The distribution of tyrosine hydroxylase (TH)-immunoreactive (IR) fibers was identical. Neuronal fibers displaying neuropeptide Y (NPY) immunoreactivity were seen in association with blood vessels. Double-labeling studies suggested that most, if not all, NPY-IR fibers were also TH-IR and likewise most, if not all, vessel-associated TH-IR fibers were also NPY-IR. Calcitonin gene-related peptide (CGRP)-IR fibers were observed near and penetrating into the epidermis, in close association with hair follicles and blood vessels, and in nerve bundles. A similar distribution of substance P (SP)-IR fibers was evident. In adult animals treated as neonates with the sympathetic neurotoxin 6-hydroxydopamine, a virtual absence of TH-IR and NPY-IR fibers was observed, whereas the distribution of CGRP-IR and SP-IR fibers appeared unaltered. During postnatal development, a generalized increase in the number, fluorescence intensity, and varicose morphology of neuronal fibers displaying catecholamine fluorescence, NPY-IR, CGRP-IR, and SP-IR was observed. By postnatal day 21, the distribution of the above fibers had reached essentially adult levels, although the density of epidermal-associated CGRP-IR and SP-IR fibers was significantly greater than in the adult. The following were not evident in thoracic hairy skin at any timepoint examined: choline acetyltransferase activity, acetylcholinesterase histochemical staining or immunoreactivity, fibers displaying immunoreactivity to vasoactive intestinal peptide, cholecystokinin, or leucine-enkephalin. The present study demonstrates that the thoracic hairy skin in developing and adult rats receives an abundant sympathetic catecholaminergic and sensory innervation, but not a cholinergic innervation.

263 Background: MDV3100 inhibits binding of androgens to AR and abiraterone is known to block androgen production through CYP17 inhibition; both are effective treatments for castration-resistant prostate cancer (CRPC, yet cross-resistance to both agents is problematic. The AR mutations F876L and T877A increase resistance to MDV3100 (M) or abiraterone (A), respectively. A regimen resistance is likely mediated through T877A activation by stimulatory progesterone (P4), pregnenolone (P5), or prednisone. The oral, non-steroidal L-inhibitor, VT-464, in phase 2 CRPC studies without prednisone coadministration, does not increase P4 or P5. Methods: The effects of VT-464, A, and M on AR transcription activity and cell proliferation were assessed and compared using reporter assays, and their oral effects in an M-resistant (F876L) human tumor mouse model were also assessed. Results: VT-464 competitively antagonized (Schild analysis) wild-type AR (IC50 =18 µM) and its potency was not decreased by AR overexpression (VCaP IC50=7.4μM). VT-464 fully antagonized AR T877A (IC50=0.52 μM) and inhibited LNCaP cell (AR T877A mutation) proliferation (IC50=0.70 μM) with potency similar to M. In contrast to M, VT-464 fully inhibited F876L (IC50=2.5 μM). VT-464 did not activate any AR forms up to the highest concentration tested (60 μM). In vivo, greater F876L tumor inhibition was observed with oral VT-464 compared to oral M or abiraterone acetate. Conclusions: VT-464 more potently antagonized mutated AR forms associated with A or M resistance than wild-type; AR antagonism contributed to xenograft activity and appears relevant to its clinical pharmacology. Due to its high L inhibition selectivity and potent mutant AR antagonist activity, VT-464 has a suitable profile for the treatment of early- or late-stage CRPC patients. VT-464 has advanced into phase 2 studies funded by Innocrin (NCT#02012920), the NCI (NCT02130700), and PCF in M- and A-resistant populations.

187 Background: VT-464 is an oral, non-steroidal inhibitor of CYP17-L and an antagonist of androgen receptor (AR) variants F876L and T877A which are associated with resistance to enzalutamide (ENZ) and abiraterone/prednisone (AA), respectively. INO-VT-464-CL-001 is a Phase (Ph) 1/2 study of VT-464 in treatment-naïve (TN) and treatment-failure (TF) patients with CRPC. Results are reported for Ph 1 (TN patients) and early results from Ph 2 patients. Methods: Phase 1: safety, tolerability, PK and initial efficacy (PSA and steroid concentrations) in M0 and M1 TN patients in escalated dose-cohorts from 50 to 600 mg bid in 28-day continuous dosing cycles. Phase 2: preliminary efficacy in M0 and M1 TN and TF (post-AA, -ENZ, and/or CHEMO) patients at 450 mg bid. Results: In Ph 1, 26 TN patients received VT-464 at 50 mg bid (n=1), 100 mg bid (n=1), 200 mg bid (n=4), 300 mg bid (n=8), 450 mg bid (n=9) and 600 mg bid (n=3) with 2 patients currently on study (15 and 29 months). Another 10 TN patients received VT-464 in Ph 2 at 450 mg bid. Most Ph 1 adverse events (AEs) were grade 1 or 2 and not considered drug related. There were 18 grade 3 AEs and 1 grade 5 AE considered not related to study drug, plus 4 grade 3 AEs (vasovagal/syncope) considered at least possibly related. For a single oral 450 mg dose, t½ was 6.8±0.8h (mean±SEM), Cmax was 8.6±1.2uM and Tmax was 3.4±0.7h. 19 of 26 Ph 1 and Ph 2 TN patients who received from 300 to 600 mg bid had PSA responses (6 PSA30%, 2 PSA50% and 1 PSA90% response). Preliminary PSA responses in Ph 2 TF patients included a PSA90% response in a prior-ENZ pre-chemo patient and a PSA50% response in a prior-ENZ and -chemo patient. No mineralocorticoid excess syndrome (MES) or changes in ACTH response or LFTs were observed. Plasma testosterone concentrations were reduced to near or below the limit of quantification in most patients at ≥ 450 mg bid, with normal progesterone and cortisol concentrations. No supplemental steroids were used. Conclusions: Clinical results at the doses evaluated support VT-464 CYP17 L-selectivity. The PSA50% and PSA90% responses in 2 of 7 prior Xtandi patients, combined with a lack of MES despite no supplemental steroids, warrants further investigation in the ongoing Ph 2 study, particularly in prior ENZ and AA patients. Clinical trial information: NCT02012920.

158 Background: CRPC typically responds to anti-androgen therapy but resistance is common. CYP17 inhibitors that block lyase (L) and not hydroxylase (H), do not require prednisone, and may delay tumor resistance are needed. VT-464 is an oral, non-steroidal inhibitor of CYP17 L in clinical development for CRPC. The present studies characterized: 1) the kinetic mechanism of VT-464 inhibition of h-CYP17 L and H, and 2) VT-464 effects compared to abiraterone acetate (AA) in CRPC models. Methods: CYP17 Enzyme Assays: r-h-CYP17 inhibition studies were conducted using substrates pregnenolone (for H) or 17-a-hydroxypregnenolone (for L). Product rates (17-a-hydroxypregnenolone (H) and DHEA (L)) were assessed by LC/MS/MS. Data were fit to inhibition models using SigmaPlot 11.2. In vitro CRPC studies: VT-464 and AA effects on AR transcription (luciferase) and PSA and NKX3.1 gene expression (QRT-PCR) were compared in C4-2B cells. Mouse xenograft model: Effects of oral VT-464 or AA on tumor growth and tumoral steroids (T, DHT, P) were compared in the MDA-PCa-133 castrate mouse model. Results: VT-464 was a reversible uncompetitive inhibitor of CYP17 L (Ki = 84 nM, K’i=200 nM) and a competitive inhibitor of H (Ki = 620 nM). VT-464 CYP17 L/H selectivity was 7.4 at low [S] but selectivity increased with increasing [S]. VT-464 L/H selectivity was 60-x greater than AA. In C4-2B cells VT-464 and AA inhibited AR transactivation but VT-464 suppressed PSA and NKX3.1 more potently than AA. In the xenograft model, VT-464 decreased tumor volume as effectively as AA. VT-464 more potently decreased T and DHT, while AA increased P. Conclusions: VT-464 demonstrated much greater CYP17 L selectivity than AA and equivalent or superior activity in several CRPC models. Less tumor resistance may arise from treatment with the CYP17 lyase-selective inhibitor VT-464 than with AA, since it more effectively blocked androgen biosynthesis, did not cause an accumulation of progesterone, and should not require co-administration of prednisone.

Cytochrome P450 17α-hydroxylase /17,20-lyase (CYP17) is a validated treatment target for metastatic castrate-resistant prostate cancer (mCRPC). Abiraterone acetate (AA; Zytiga) inhibits 17α-hydroxylase and 17,20-lyase reactions catalyzed by CYP17 and thus reduces androgen biosynthesis. However, co-administration of prednisone is required to suppress the mineralocorticoid excess from 17α-hydroxylase inhibitions. VT-464, a non-steroidal small molecule inhibits androgen production without mineralocorticoid excess or cortisol depletion by selective inhibition of CYP17 17,20-lyase. We determined the impact of VT-464 on tumor growth of a mCRPC xenograft, MDA-PCa-133, in vivo, and on androgen signaling in C4-2B prostate cancer cells in vitro. The MDA-PCa-133 xenograft is derived from a clinical CRPC bone metastasis. Subcutaneous MDA-PCa-133 tumor expresses PSA, full-length androgen receptor (AR) and AR-V7 isoform. We determined the effect of VT464 and AA on MDA-PCa-133 growing in tumor-bearing castrated male mice: randomization into three groups; oral treatment with vehicle only, VT-464, (100 mg/kg bid), or AA (100 mg/kg bid) for 25 days. Both VT-464 and AA reduced tumor volume (>two fold compared to vehicle; p We determined the effects of VT-464 on AR-dependent luciferase reporter activity and expression of AR signaling genes, PSA and NKX3.1, in cultured C4-2B prostate cancer cells with or without VT-464 or AA treatment. VT-464 or AA highly reduced AR-dependent reporter activity and specific expression of PSA and NKX3.1. AR-dependent signaling in the presence of VT-464 or AA was restored however by 10 nM DHT, consistent with VT-464- or AA-mediated depletion of androgen in C4-2B cells. The AR-dependent reporter activity was also measured following overexpression of full-length AR or AR-V7 isoform in C4-2B cells. Full-length AR-dependent reporter activity was (>80%) inhibited; AR-V7-dependent reporter activity was inhibited by 50% by 1 μM VT-464 or AA. We conclude that VT-464 inhibited AR signaling as effectively as AA in C4-2B prostate cancer cells. The findings suggest that AR signaling in cells, which express high levels of AR isoform (AR-V7) are more resistant to androgen biosynthesis inhibitors than those with wild type AR. Preliminary observations suggest C4-2B cells with AR-V7 are less sensitive to AA than VT- 464. Ongoing clinical and co-clinical studies will determine if the observed differences in steroid profile and relative efficacy of VT-464 compared to AA are clinically and biologically meaningful. Citation Format: Sankar N. Maity, Guanglin Wu, Jing-fang Lu, Joel R. Eisner, Stephen W. Rafferty, Robert J. Schotzinger, William R. Moore, Christopher J. Logothetis, John C. Araujo, Eleni Efstathiou. Efficacy of VT-464, a novel selective inhibitor of cytochrome P450 17,20-lyase, in castrate-resistant prostate cancer models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4772. doi:10.1158/1538-7445.AM2013-4772

198 Background: CYP17 is a single protein with two distinct enzyme activities, 17 α-hydroxylase (hydroxylase) and 17,20-lyase (lyase). Reduction of extragonadal androgen production through CYP17 inhibition is a validated CRPC treatment paradigm. While treatment with the recently-approved CYP17 inhibitor, abiraterone acetate (AA), increases overall survival in post-docetaxel CRPC patients (de Bono et al, N Engl J Med 2011; 364:1995–2005), it is also associated with cortisol (F) suppression and increased steroid concentrations up-stream of CYP17 hydroxylase. The clinical candidate VT-464 is an oral, non-steroidal, lyase-selective CYP17 inhibitor. The study objectives were to compare VT-464 to abiraterone in regards to in vitro selectivity and to compare VT-464 to AA in regards to in vivo primate endocrine response. Methods: Human CYP17 hydroxylase and lyase IC50 values were determined for VT-464 and abiraterone in vitro. Plasma progesterone (P), F, and testosterone (T) responses were measured 0-24 hours after single subcutaneous doses of AA (12.5 mg/kg), VT-464 (6.25 and 12.5 mg/kg), or vehicle in adult, castrate, male rhesus monkeys. Results: Human lyase and hydroxylase IC50 values were 69nM and 670nM for VT-464 and 15nM and 2.5nM for abiraterone, respectively. AA and both dose levels of VT-464 produced a similar overall reduction in plasma T, compared to vehicle (p ≤ 0.009). AA treatment resulted in an elevated plasma P (peak increase >9,000%; p ≤ 0.05), compared to both VT-464 treatments and vehicle. F was not affected by either VT-464 dose, whereas AA resulted in F suppression (p ≤ 0.005) compared to vehicle. Conclusions: VT-464 was 10-fold more selective for human CYP17 lyase vs. hydroxylase inhibition. This selectivity was associated with androgen suppression, but not increases of up-stream steroids or F suppression in male monkeys. In contrast, abiraterone was 6-fold more selective for hydroxylase vs. lyase inhibition resulting in associations with increased up-stream steroids and F suppression in AA-treated male monkeys, consistent with clinical observations in CRPC. VT-464 may thus provide a more lyase-selective alternative to AA for extra-gonadal androgen suppression in CRPC.

4671 Background: With the FDA approval of abiraterone acetate, inhibition of CYP17 (17α hydroxylase/C17, 20-lyase) is now a validated approach to the treatment of castration-resistant prostate cancer. VT-464 is a novel, selective CYP17-lyase inhibitor with decreased activity against CYP17 hydroxylase (less mineralcocorticoid and glucocorticoid effects). The study objectives were to observe the effects of VT-464 in a prostate cancer xenograft model and to compare its activity to abiraterone acetate and surgical castration. Methods: SCID mice were implanted subcutaneously with LNCaP cells. When tumors reached 100 mm3, mice were randomized to receive vehicle (0.5% CMC in saline, 5 mL/kg), VT-464 at 15, 50, or 100 mg/kg p.o. b.i.d. A second cohort of LNCaP tumor-bearing mice received vehicle, surgical castration, or VT-464, or abiraterone acetate at 100 mg/kg p.o. b.i.d. for 28 days. Terminal blood and tumor concentrations were analyzed on day 28, four hours after the last dose. Results: In the first LNCaP xenograft cohort, percent growth inhibition (± S.E.) of 9.6 (±15.6), 38.5 (±12.4), and 73.9 (±13.2) was observed on day 21 of treatment for VT-464 doses of 15, 50, and 100 mg/kg, respectively. Growth reduction at 100 mg/kg was statistically significant compared to vehicle control from day 7 to 28. VT-464 was well tolerated with insignificant weight loss at all doses. In the second cohort, VT-464-treated (100 mg/kg) mice had significantly reduced tumor volumes on day 28 compared to control and abiraterone acetate (p

64 Background: With the recent FDA approval of abiraterone acetate, CYP17 (17α hydroxylase/C17, 20-lyase) has become a proven target for the treatment of castration- resistant prostate cancer. Inhibition of CYP17-lyase causes a decrease in circulating androgens, severely hampering activation of the androgen receptor signaling pathway that prostate cancer relies on for proliferation. However, inhibition of CYP17-hydroxylase, a second enzymatic activity of CYP17, leads to an increase in upstream steroids that can cause mineralocorticoid excess syndrome as well as a decrease in cortisol production. VT-464 is a novel, selective CYP17 lyase inhibitor with decreased activity against CYP17 hydroxylase. The study objectives were to observe the effects of VT-464 in a prostate cancer xenograft model and to compare its activity to abiraterone acetate and surgical castration. Methods: SCID mice were implanted subcutaneously with LNCaP cells. When tumors reached 100mm3, mice were randomized to receive vehicle (0.5% CMC in saline, 5ml/kg), or VT-464 at 15, 50, or 100mg/kg p.o. bid. A second cohort of LNCaP tumor-bearing mice received vehicle, surgical castration, or VT-464 or abiraterone acetate at 100mg/kg p.o. bid for 28 days. Results: In the LNCaP xenograft model, percent growth inhibition (± S.E.) of 9.6 (±15.6), 38.5(±12.4), and 73.9 (±13.2) was observed on day 21 of treatment for the VT-464 doses of 15, 50, and 100 mg/kg, respectively. VT-464 -treated (100mg/kg) mice had a significantly reduced tumor volume ratio (V/V0) on day 28 compared to control and abiraterone acetate (p Conclusions: VT-464 exhibited dose-dependent growth inhibition with significantly reduced tumor growth at the highest dose compared to abiraterone acetate. The reduction in tumor growth in VT-464-treated animals was similar to that of castrate animals. These preclinical results show promising activity of VT-464 in the treatment of prostate cancer.

While the majority of sympathetic neurons are noradrenergic, a minority population are cholinergic. At least one population of cholinergic sympathetic neurons arises during development by a target-dependent conversion from an initial noradrenergic phenotype. Evidence for retrograde specification has been obtained from transplantation studies in which sympathetic neurons that normally express a noradrenergic phenotype throughout life were induced to innervate sweat glands, a target normally innervated by cholinergic sympathetic neurons. This was accomplished by transplanting footpad skin containing sweat gland primordia from early postnatal donor rats to the hairy skin region of host rats. The sympathetic neurons innervating the novel target decreased their expression of noradrenergic traits and developed choline acetyltransferase (ChAT) activity. In addition, many sweat gland-associated fibers acquired acetylcholinesterase (AChE) staining and VIP immunoreactivity. These studies indicate that sympathetic neurons in vivo alter their neurotransmitter phenotype in response to novel environmental signals and that sweat glands play a critical role in the cholinergic and peptidergic differentiation of the sympathetic neurons that innervate them. The sweat gland-derived cholinergic differentiation factor is distinct from leukemia inhibitory factor and ciliary neurotrophic factor, two well-characterized cytokines that alter the neurotransmitter properties of cultured sympathetic neurons in a similar fashion. Recent studies indicate that anterograde signalling is also important for the establishment of functional synapses in this system. We have found that the production of cholinergic differentiation activity by sweat glands requires sympathetic innervation, and the acquisition and maintenance of secretory competence by sweat glands depends upon functional cholinergic innervation.

The sweat glands, a target of cholinergic sympathetic neurons, were replaced with parotid gland, a target of noradrenergic sympathetic neurons, in neonatal rats. This transplantation paradigm allowed sympathetic neurons that would normally innervate the sweat glands and develop a cholinergic phenotype to innervate the parotid gland instead. The innervation of the transplanted parotid gland did not develop a cholinergic phenotype, as assessed by choline acetyltransferase activity and acetylcholinesterase immunoreactivity, but continued to express intense catecholamine fluorescence. In addition, immunoreactivity for vasoactive intestinal peptide, normally expressed by the sympathetic innervation of the sweat glands but not the parotid, was observed in only a small percentage of the parotid-associated fibers. These results suggest that cellular interactions between neurons and their targets play an important role in the differentiation of mature neurotransmitter and neuropeptide phenotypes in vivo.

Mammalian sympathetic neurons in vivo may express either a noradrenergic or cholinergic phenotype. In view of the opposing effect of noradrenaline and acetv Icholine on most autonomic target organs, the target-appropriate expression of neurotransmitter is critical. We have examined the maturation of the sympathetic innervation of rat sweat glands to define the developmental mechanisms regulating neurotransmitter choice in vivo1–5. Eccrine sweat glands and their sympathetic innervation develop together post-natally in the rat. Early postnatal innervation expresses only noradrenergic properties, but as the glands and their innervation mature, noradrenergic properties decrease dramatically and cholinergic features appear in the same population of neurons. To investigate the role of the sweat gland in this change we have used a transplantation paradigm which allows sweat glands to be innervated by sympathetic neurons that would normally innervate noradrenergic target organs and remain noradrenergic throughout life. We observe that the sympathetic neurons that innervate the novel cholinergic target alter their neurotransmitter properties and develop a cholinergic phenotype. These results indicate that target organs are able to induce appropriate neurotransmitter traits in the neurons that innervate them.