Impact of the Major Candida glabrata Triazole Resistance Determinants on the Activity of the Novel Investigational Tetrazoles VT-1598 and VT-1161.

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.

Development of Highly Selective Pyrimidine-Based Aldosterone Synthase (CYP11B2) Inhibitors.

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.

In Vitro Activities of the Novel Investigational Tetrazoles VT-1161 and VT-1598 Compared to the Triazole Antifungals against Azole-Resistant Strains and Clinical Isolates of Candida albicans.

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.

In Vivo Efficacy of VT-1129 against Experimental Cryptococcal Meningitis with the Use of a Loading Dose-Maintenance Dose Administration Strategy.

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 (R2 = 0.72 and R2 = 0.67, respectively), with a plasma concentration of 1 µg/ml yielding a reduction of ∼5 log10 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.

The Fungal Cyp51 Inhibitor VT-1129 Is Efficacious in an Experimental Model of Cryptococcal Meningitis.

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.

VT-1161 protects mice against oropharyngeal candidiasis caused by fluconazole-susceptible and -resistant Candida albicans.

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.

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

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.

Design and optimization of highly-selective, broad spectrum fungal CYP51 inhibitors.

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.

Crystal Structure of the New Investigational Drug Candidate VT-1598 in Complex with Aspergillus fumigatus Sterol 14α-Demethylase Provides Insights into Its Broad-Spectrum Antifungal Activity.

Within the past few decades, the incidence and complexity of human fungal infections have increased, and therefore, the need for safer and more efficient, broad-spectrum antifungal agents is high. In the study described here, we characterized the new tetrazole-based drug candidate VT-1598 as an inhibitor of sterol 14α-demethylase (CYP51B) from the filamentous fungus Aspergillus fumigatus VT-1598 displayed a high affinity of binding to the enzyme in solution (dissociation constant, 13 ± 1 nM) and in the reconstituted enzymatic reaction was revealed to have an inhibitory potency stronger than the potencies of all other simultaneously tested antifungal drugs, including fluconazole, voriconazole, ketoconazole, and posaconazole. The X-ray structure of the VT-1598/A. fumigatus CYP51 complex was determined and depicts the distinctive binding mode of the inhibitor in the enzyme active site, suggesting the molecular basis of the improved drug potency and broad-spectrum antifungal activity. These data show the formation of an optimized hydrogen bond between the phenoxymethyl oxygen of VT-1598 and the imidazole ring nitrogen of His374, the CYP51 residue that is highly conserved across fungal pathogens and fungus specific. Comparative structural analysis of A. fumigatus CYP51/voriconazole and Candida albicans CYP51/VT-1161 complexes supports the role of H bonding in fungal CYP51/inhibitor complexes and emphasizes the importance of an optimal distance between this interaction and the inhibitor-heme iron interaction. Cellular experiments using two A. fumigatus strains (strains 32820 and 1022) displayed a direct correlation between the effects of the drugs on CYP51B activity and fungal growth inhibition, indicating the noteworthy anti-A. fumigatus potency of VT-1598 and confirming its promise as a broad-spectrum antifungal agent.

The Tetrazole VT-1161 Is a Potent Inhibitor of Trichophyton rubrum through Its Inhibition of T. rubrum CYP51.

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 [Kd ] 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; Km value, 2 µM). The investigational agent VT-1161 bound tightly to T. rubrum CYP51 (Kd = 242 nM) with an affinity similar to that of clotrimazole, fluconazole, ketoconazole, and voriconazole (Kd values, 179, 173, 312, and 304 nM, respectively) and with an affinity lower than that of itraconazole (Kd = 53 nM). Determinations of 50% inhibitory concentrations (IC50s) using 0.5 µM CYP51 showed that VT-1161 was a tight-binding inhibitor of T. rubrum CYP51 activity, yielding an IC50 of 0.14 µM, whereas itraconazole, fluconazole, and ketoconazole had IC50s 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 MIC50, MIC90, 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.

Structural analyses of Candida albicans sterol 14α-demethylase complexed with azole drugs address the molecular basis of azole-mediated inhibition of fungal sterol biosynthesis.

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.

Efficacy of the Investigational Antifungal VT-1161 in Treating Naturally Occurring Coccidioidomycosis in Dogs.

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.

Activity of VT-1129 against Cryptococcus neoformans clinical isolates with high fluconazole MICs.

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.

The Investigational Drug VT-1129 Is a Highly Potent Inhibitor of Cryptococcus Species CYP51 but Only Weakly Inhibits the Human Enzyme.

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 [Kd] range, 14 to 25 nM) with affinities similar to those of fluconazole, voriconazole, itraconazole, clotrimazole, and ketoconazole (Kd range, 4 to 52 nM), whereas VT-1129 bound weakly to human CYP51 (Kd, 4.53 µM). VT-1129 was as effective as conventional triazole antifungal drugs at inhibiting cryptococcal CYP51 activity (50% inhibitory concentration [IC50] range, 0.14 to 0.20 µM), while it only weakly inhibited human CYP51 activity (IC50, ∼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.

The Investigational Fungal Cyp51 Inhibitor VT-1129 Demonstrates Potent In Vitro Activity against Cryptococcus neoformans and Cryptococcus gattii.

Thein vitroactivities of the novel fungal Cyp51 inhibitor VT-1129 were evaluated against a large panel ofCryptococcus neoformansandCryptococcus gattiiisolates. VT-1129 demonstrated potent activities against bothCryptococcusspecies as demonstrated by low MIC50and MIC90values. ForC. gattii, thein vitropotency was maintained against all genotypes. In addition, significantly lower geometric mean MICs were observed for VT-1129 than for fluconazole againstC. neoformans, including isolates with reduced fluconazole susceptibility.

Clinical Candidate VT-1161's Antiparasitic Effect In Vitro, Activity in a Murine Model of Chagas Disease, and Structural Characterization in Complex with the Target Enzyme CYP51 from Trypanosoma cruzi.

A novel antifungal drug candidate, the 1-tetrazole-based agent VT-1161 [(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], which is currently in two phase 2b antifungal clinical trials, was found to be a tight-binding ligand (apparent dissociation constant [Kd], 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.

Evaluation of VT-1161 for Treatment of Coccidioidomycosis in Murine Infection Models.

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 MIC50 and MIC90 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.

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

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.

Design and optimization of highly-selective fungal CYP51 inhibitors.

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.

Highly-selective 4-(1,2,3-triazole)-based P450c17a 17,20-lyase inhibitors.

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.