No abstract

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.

Summary The pharmacological activity of different nuclear receptor (NR) ligands is reflected by their impact on receptor structure. Thus, we asked whether differential presentation of protein-protein interaction surfaces on the androgen receptor (AR), a surrogate assay of receptor conformation, could be used in a prospective manner to define the pharmacological activity of bound ligands. To this end, we identified over 150 proteins/polypeptides whose ability to interact with AR is influenced in a differential manner by ligand binding. The most discriminatory of these protein-AR interactions were used to develop a robust compound-profiling tool that enabled the separation of ligands into functionally distinguishable classes. Importantly, the ligands within each class exhibited similar pharmacological activities, a result that highlights the relationship between receptor structure and activity and provides direction for the discovery of novel AR modulators.

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.

No abstract

An efficient synthesis of 2-{4-[({4-{[4-(4-methoxyphenyl)piperazin-1-yl]methyl}-2-[4-(trifluoromethyl)phenyl]-1,3-thiazol-5-yl}methyl)thio]phenoxy}-2-methylpropanoic acid (1), a potent PPARpan agonist, is described. The seven-step synthesis, which afforded 1 in 30% overall yield, includes a highly regioselective carbon-sulfur bond formation via coupling of a bishydroxymethylthiazole (3) with 4-hydroxythiophenol, displacement of the remaining alcohol through a three-step telescoped sequence involving an efficient cleavage of an aryl mesylate, and an efficient and practical method of introducing an isobutyric acid fragment.

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<0.05, p<0.01, respectively). Reduction in tumor volumes were similar between VT-464-treated (100 mg/kg) and castrate animals. Plasma and tumor analyses revealed much greater plasma and tumor exposure of VT-464 compared to abiraterone acetate. Conclusions: VT-464 exhibited dose-dependent growth inhibition with significantly reduced tumor volumes at the highest dose compared to abiraterone acetate. The activity 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.

Regioselective and Stereoselective Reductive Cleavage of 1,7-Dioxaspiro(5.5)undecane Alcohols.-The regioselectivity of the Lewis-acid promoted reduction of the 6,6-spiroketal alcohols is controlled by the pendant hydroxyl groups. The appended groups allow bidentate coordination of the Lewis acid to selectively activate one C-O bond of the anomeric center toward reductive cleavage.