Phase 2 Study of Seviteronel (INO-464) in Patients With Metastatic Castration-Resistant Prostate Cancer After Enzalutamide Treatment.

BACKGROUND: Seviteronel was being developed by Innocrin Pharmaceuticals as a selective cytochrome P450c17a (CYP17) 17,20-lyase (lyase) inhibitor and androgen receptor antagonist with activity against prostate cancer cells in vitro and in vivo. This open-label phase 2 clinical study evaluated the tolerability and efficacy of seviteronel in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with enzalutamide. PATIENTS AND METHODS: Patients with mCRPC whose disease previously progressed while receiving enzalutamide therapy were divided into 2 cohorts on the basis of prior exposure to docetaxel. Seviteronel was administered without routine oral steroids either twice daily with dose titration (450 mg) or once daily without dose titration (600 or 750 mg). The primary objective was to determine the rate of significant prostate-specific antigen response (ie, decline of ≥ 50%) after 12 weeks of seviteronel therapy. RESULTS: Seventeen patients, with a median (range) age of 71 (60-92) years, were enrolled, with 8 patients having received prior docetaxel. Patients received a median of 2 cycles of treatment, with most patients discontinuing treatment because of toxicity related to the study drug. The most common adverse events included concentration impairment, fatigue, tremor, and nausea. Despite changes in dosing, the study was closed prematurely because of the high magnitude of toxicity. One (6%) of 17 patients experienced a significant decline in prostate-specific antigen. CONCLUSION: Seviteronel was not generally well tolerated nor associated with significant clinical responses in patients with mCRPC who had previously received enzalutamide. Further investigation of single-agent seviteronel in this patient population is not warranted; however, studies investigating seviteronel with low-dose dexamethasone are ongoing in patients with androgen receptor-positive tumors.

Androgen receptor antagonism drives cytochrome P450 17A1 inhibitor efficacy in prostate cancer.

The clinical utility of inhibiting cytochrome P450 17A1 (CYP17), a cytochrome p450 enzyme that is required for the production of androgens, has been exemplified by the approval of abiraterone for the treatment of castration-resistant prostate cancer (CRPC). Recently, however, it has been reported that CYP17 inhibitors can interact directly with the androgen receptor (AR). A phase I study recently reported that seviteronel, a CYP17 lyase-selective inhibitor, ædemonstrated a sustained reduction in prostate-specific antigen in a patient with CRPC, and another study showed seviteronel's direct effects on AR function. This suggested that seviteronel may have therapeutically relevant activities in addition to its ability to inhibit androgen production. Here, we have demonstrated that CYP17 inhibitors, with the exception of orteronel, can function as competitive AR antagonists. Conformational profiling revealed that the CYP17 inhibitor-bound AR adopted a conformation that resembled the unliganded AR (apo-AR), precluding nuclear localization and DNA binding. Further, we observed that seviteronel and abiraterone inhibited the growth of tumor xenografts expressing the clinically relevant mutation AR-F876L and that this activity could be attributed entirely to competitive AR antagonism. The results of this study suggest that the ability of CYP17 inhibitors to directly antagonize the AR may contribute to their clinical efficacy in CRPC.

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.

Synthesis and pharmacological evaluation of N-(3-(1H-indol-4-yl)-5-(2-methoxyisonicotinoyl)phenyl)methanesulfonamide (LP-261), a potent antimitotic agent.

The synthesis and optimization of a series of orally bioavailable 1-(1H-indol-4-yl)-3,5-disubstituted benzene analogues as antimitotic agents are described. A functionalized dibromobenzene intermediate was used as a key scaffold, which when modified by sequential Suzuki coupling and Buchwald-Hartwig amination provided a flexible entry to 1,3,5-trisubstituted phenyl compounds. A 1H-indol-4-yl moiety at the 1-position was determined to be a critical feature for optimal potency. The compounds have been shown to induce cell cycle arrest at the G2/M phase and demonstrate efficacy in both cell viability and cell proliferation assays. The primary site of action for these agents is revealed by their colchicine competitive inhibition of tubulin polymerization, and a computational model has been developed for the association of these compounds to tubulin. An optimized lead LP-261 significantly inhibits growth of a human non-small-cell lung tumor (NCI-H522) in a mouse xenograft model.

Early prosthetic complications after unipolar hemiarthroplasty.

BACKGROUND: In Australia, the most frequently used hemiarthroplasty prosthesis for the management of displaced intracapsular femoral neck fractures is the Uncemented Austin Moore (UAM). Despite concerns regarding poor functional outcomes and increased early revision rates associated with the UAM prosthesis, apprehension regarding the systemic side-effects of polymethylmethacrylate cement implantation in the elderly patient continues to influence prosthesis selection. This study examines the incidence of early prosthesis related complications after UAM and Cemented Thompson (CT) hemiarthroplasty procedures for the management of femoral neck fractures. METHODS: A multicentre retrospective review of charts and radiographs was conducted in 1118 unipolar hemiarthroplasty implantations to determine early complications associated with the CT and UAM prostheses over a 6-year period in five Queensland public hospitals. RESULTS: Intraoperative periprosthetic fractures were sustained in 11.8% of UAM and 1.8% of CT implantations (P < 0.0001). Intraoperative periprosthetic fractures were associated with an increased requirement for reoperation within 1 month of the index procedure (P = 0.05). No statistical difference in the incidence of intraoperative periprosthetic fractures could be observed between the hospitals participating, regardless of the proportional use of each prosthesis. Early dislocation rates were similar for the UAM and CT prostheses. The intraoperative mortality rate attributable to the use of polymethylmethacrylate cement during hip hemiarthroplasty was 1/738 (0.14%). CONCLUSIONS: The results of this study support the use of the CT prosthesis for the management of femoral neck fractures to reduce the high incidence of intraoperative periprosthetic fractures and associated requirements for early reoperation experienced with the UAM.

Maximizing discovery efficiency with a computationally driven fragment approach.

A reliable and accurate method for the computational design of novel drug candidates has been a passionate pursuit of the pharmaceutical industry. Such technology would dramatically improve the efficiency of drug discovery by quickly and inexpensively providing potent molecules that can be further prioritized for synthesis based on characteristics such as patentability, specific protein-ligand interactions, ease of chemical synthesis, protein selectivity and pharmacological considerations. Described herein is the progress made at Locus Pharmaceuticals Inc toward achieving this ideal with a fragment-driven, computationally directed approach to small-molecule discovery. Specific lead identification examples from Locus Pharmaceuticals discovery programs demonstrate the efficiency and cost-effectiveness realized by such an approach.

Synthesis of 21,21-difluoro-3 beta-hydroxy-20-methylpregna-5,20-diene and 5,16,20-triene as potential inhibitors of steroid C17(20) lyase.

Novel 21,21-difluorovinyl steroids, designed as difluorinated C20(21) enol mimics of pregnenolone, were targeted as potential mechanism-based inhibitors of C17(20) lyase, a crucial enzyme in the biosynthesis of testosterone. Addition of (difluoromethyl)diphenylphosphine oxide reagent to 17-acetyl steroids was the approach chosen for the construction of these compounds. Of particular interest were the abnormal Wittig products which formed during attempted preparation of the triene 9. The target difluoroolefin 3 was found to be a moderately potent, time-dependent inhibitor of the enzyme.