SAR studies of 6-(arylamino)-4,4-disubstituted-1-methyl-1,4-dihydro-benzo[d][1,3]oxazin-2-ones as progesterone receptor antagonists

We previously disclosed that 6-aryl benzoxazin-2-ones were PR modulators. In a continuation of this work we examined the SAR of new 6-arylamino benzoxazinones and found the targets 1-25, with an extra amino linker between the pendent 6-aryl groups and benzoxazinone or benzoxazine-2-thione core, were PR antagonists. A series of compounds with substituents at the 1- and 4-positions as well as different 6-aryl groups were prepared and tested in the T47D cell alkaline phosphatase assay. Interestingly, the SAR unveiled from the 6-arylamino benzoxazinones was quite different from those of their parent compounds. For example, in contrast to the 6-aryl benzoxazinones, methyl substitution at the 1-position significantly increased the potency of 6-arylamino benzoxazinones. Several 6-arylamino benzoxazinones (e.g., 12, IC(50)=5.0 nM) had low nanomolar in vitro potency as PR antagonists in the T47D cell alkaline phosphatase assay.     

Potent nonsteroidal progesterone receptor agonists: synthesis and SAR study of 6-aryl benzoxazines

Novel 6-aryl benzoxazines were prepared and examined as progesterone receptor (PR) modulators. In contrast to the structurally related 6-aryl dihydroquinoline PR antagonists, the 6-aryl benzoxazines were potent PR agonists. Compounds 4e, 5b, and 6a with the 2,4,4-trimethyl-1,4-dihydro-2H-benzo[d][1,3]oxazine core were the most potent PR agonists in the series with sub-nanomolar activities (EC(50) 0.20-0.35nM). Compound 6a was more potent than progesterone (P4) in the in vivo decidualization assay in an ovariectomized female rat model by subcutaneous administration with an ED(50) of 1.5mg/kg (vs 5.62mg/kg for P4).     

5-(3-Cyclopentyl-2-thioxo-2,3-dihydro-1H-benzimidazol-5-yl)-1-methyl-1H-pyrrole-2-carbonitrile: A novel, highly potent, selective, and orally active non-steroidal progesterone receptor agonist

We have recently discovered 5-(3-cyclopentyl-2-thioxo-2,3-dihydro-1H-benzimidazol-5-yl)-1-methyl-1H-pyrrole-2-carbonitrile (14) as a potent, selective, and orally active non-steroidal progesterone receptor (PR) agonist. Compound 14 and its analog 13 possessed sub-nanomolar in vitro potency (EC(50) 0.1-0.5nM) in the T47D alkaline phosphatase assay, similar to that of the steroidal PR agonist medroxyprogesterone acetate (MPA). In contrast to MPA, 14 was highly selective (>500-fold) for the PR over both glucocorticoid and androgen receptors. In the rat uterine decidualization and complement component C3 models, 14 had oral ED(50) values of 0.02 and 0.003mg/kg, respectively, and was from 6- to 20-fold more potent than MPA. In the monkey ovulation inhibition model, compound 14 was also highly efficacious and potent with an oral ED(100) of 0.03mg/kg.     

7-aryl 1,5-dihydro-benzo[e][1,4]oxazepin-2-ones and analogs as non-steroidal progesterone receptor antagonists

Novel 7-aryl benzo[1,4]oxazepin-2-ones were synthesized and evaluated as non-steroidal progesterone receptor (PR) modulators. The structure activity relationship of 7-aryl benzo[1,4]oxazepinones was examined using the T47D cell alkaline phosphatase assay. A number of 7-aryl benzo[1,4]oxazepinones such as 10j and 10v demonstrated good in vitro potency (IC(50) of 10-30 nM) and selectivity (over 100-fold) at PR over other steroidal receptors such as glucocorticoid and androgen receptors (GR and AR). Several 7-aryl benzo[1,4]oxazepinones were active in the rat uterine decidualization model. In this in vivo model, compounds 10j and 10u were active at 3 mg/kg when dosed orally.     

In vitro characterization of trimegestone: a new potent and selective progestin

Trimegestone (TMG) is a novel 19-norpregnane progestin under development for hormone replacement therapy and oral contraception. The objective of the current study was to characterize the potency and steroid receptor selectivity of TMG in several in vitro assays and to compare its activity to that of medroxyprogesterone acetate (MPA). TMG and MPA had a similar competitive binding affinity for human and rabbit progesterone receptor (PR). However, TMG had a significantly higher affinity for rat PR (IC(50) = 3.3 nM) than MPA (IC(50) = 53.3 nM). In T47D cells, both compounds increased alkaline phosphatase activity and cell proliferation with comparable potencies (EC(50s) of 0.1 nM and of 0.02 nM, respectively). To further characterize the progestational activity and steroid receptor selectivity, we established an immortalized human endometrial stromal cell line (HESC-T). This cell line lacks endogenous estrogen receptor (ER) and PR but does have functional glucocorticoid receptors (GR). When ER is transiently expressed in the cells, 17beta-estradiol (E(2)) induces PR, allowing the study of PR-regulated genes. In HESC-T cells expressing exogenous ER, and therefore PR, both TMG and MPA increased HRE-tk-luciferase activity tenfold with an EC(50) of 0.2 nM. In HESC-T cells without exogenous ER, and therefore no PR, TMG did not induce HRE-tk-luciferase activity, whereas MPA induced the reporter activity with an EC(50) of about 10 nM. This MPA-induced reporter activity is believed to be mediated through GR. The steroid receptor selectivity of TMG was further evaluated using the HRE-tk-luciferase assay in the human lung carcinoma cell line A549, which contains GR but no PR. In these cells TMG had no effect on luciferase activity, whereas MPA increased the reporter activity in a dose-dependent manner with an EC(50) of approximately 30 nM. Furthermore, HRE-tk-luciferase assay in mouse fibroblast cell line L929, which expresses androgen receptor (AR) but no PR, showed that TMG had weak antiandrogenic activity whereas MPA had androgenic activity. In summary, data from several in vitro assays demonstrate that TMG is a potent progestin with a better receptor selectivity profile than MPA.     

Progestins, progesterone receptor modulators, and progesterone antagonists change VEGF release of endometrial cells in culture

The influences of the synthetic progestin, medroxyprogesterone acetate (MPA), the progesterone receptor modulator J867, and the antagonist ZK137316 were studied in vitro on isolated endometrial epithelial cells, as well as endometrial fibroblasts. We evaluated the expression of estrogen receptor alpha (ER) and the progesterone receptor (PR) by RT-PCR. ER and PR were strongly expressed in the fibroblasts and epithelial cells under treatment with 10(-8) M 17beta-estradiol (E(2)). Treatment with 10(-6) M J867 or ZK137316 upregulated the PR expression as did E(2), in contrast to treatment with 10(-6) M MPA, which caused a downregulation of PR in epithelial cells, but not in fibroblasts. In addition, the vascular endothelial growth factor (VEGF) release into the cell culture medium was analyzed by a VEGF-ELISA. VEGF which plays an important role in angiogenesis, is regulated by steroid hormones as well as hypoxia. E(2) stimulates VEGF release into the medium in both cell types. MPA reduces VEGF release significantly in the fibroblast cell culture, but increases it in the epithelial cell culture. ZK137316, in the presence or absence of E(2), reduces VEGF release in fibroblast cell culture. J867 increases the VEGF production in fibroblasts only in the presence of E(2). Both compounds show no significant effects, compared to E(2), in epithelial cell culture. The different results for the epithelial cells and fibroblasts indicate that the pharmacological effects of PR modulators (PRMs) and progesterone antagonists (PAs) may be cell specific and depend on the presence or absence of partial progestagenic agonistic activities. This observation opens up new perspectives for various clinical applications.     

SAR studies of 6-aryl-1,3-dihydrobenzimidazol-2-ones as progesterone receptor antagonists

We have previously reported that the aryl substituted benzimidazolones, benzoxazinones, and oxindoles (e.g., 1-3) are progesterone receptor (PR) antagonists and have recently disclosed that the nature of 5- and 6-aryl moieties played a critical role in PR functional activity in the oxindole and benzoxazinone templates. For example, replacing the phenyl group of PR antagonists 2 and 3 with a 5'-cyanopyrrol-2'-yl moiety switched their functional activity to PR agonist activity (2a and 3a). These findings prompted us to examine if there is a similar effect of the 6-aryl moieties on the PR functional activity for the benzimidazolone template. Numerous analogs, such as 5, showed potent PR antagonist activity with about a 10-fold increase in potency as compared to those reported earlier in the same series. More interestingly, pyrrole-containing benzimidazolones 24-27 remained as PR antagonists in contrast to the PR agonist activity switch for oxindole and benzoxazinone scaffolds when a 5'-cyanopyrrol-2'-yl group was installed as a pendant aryl group.     

The influence of exogenous steroid hormones on steroid receptors, uterine histological structure and the bacterial flora of the normal bitch.

Oestrogen (ER) and progesterone (PR) receptors have been shown to vary in both concentration and distribution during the oestrous cycle of the bitch, influenced by the normal changes in endogenous reproductive hormones. The influence of exogenous steroid hormones on steroid receptors and the histological structure of the uterus was studied in two groups of parous Beagle bitches. Group A (n = 6) were treated with progesterone (P4) in oil i.m. (3 mg/kg) in late metoestrus on the day that peripheral plasma P4 concentrations were first identified as <10 ng/ml, and subsequently once weekly on three other occasions. Group B (n = 6) were treated with a single i.m. injection of MPA (50 mg, 4.2-5.6 mg/kg) following the same protocol. Full-thickness uterine wall biopsies were obtained from the mid part of one horn 2-7 days after the last (fourth) injection of P4 or MPA. During the subsequent oestrus, when peripheral plasma P4 concentrations were between 8 and 10 ng/ml, each bitch in both groups (n = 12) received a single injection of oestradiol benzoate (ODB) in oil i.m. (7.5 mg, 0.63-0.84 mg/kg). All bitches had an ovariohysterectomy 7 days later. Full-thickness uterine wall samples were obtained from the mid part of the intact horn and other parts of the uterus. Swabs were taken from the uterine lumen for bacteriological examination; all were sterile. Tissue samples were sectioned and examined for evidence of lesions, and stained for ER and PR receptors using an immunocytochemical method. The immunoreactivity was scored semiquantitatively, incorporating both the intensity and distribution of specific staining of the receptors using a simplified histoscore (H-score). At the time of ovariohysterectomy, fluid had accumulated in the isolated section of the uterine horn distal to the point of biopsy; the volume was greater in the MPA-treated bitches. There was also evidence in some sections of histological changes in the endometrium. Variations in the expression of both ER and PR were seen between bitches, which may have been due to some not being in mid-metoestrus at the time of treatment. In general, ER scores were low after P4 and MPA treatment, but following ODB there was a significant (P<0.05) increase in ER expression in all parts of the endometrium. PR scores were zero in the glandular epithelium of all 12 bitches after P4, MPA and ODB treatment, whereas in the other parts of the endometrium they were generally moderate to high. Following treatment with ODB, PR generally increased in the three regions of the endometrium where PR were present. The study shows that ER and PR distribution and expression in the endometrium of bitches can be modified by P4, MPA and ODB, with evidence of individual variation.     

Synthesis and progesterone receptor antagonist activities of 6-aryl benzimidazolones and benzothiazolones

Novel 6-aryl benzimidazolones and benzothiazolones were prepared and examined as bioisosteres of the recently reported 6-aryl dihydroquinolines (1) for progesterone receptor (PR) antagonist activities. PR antagonist activities increased when compounds 9c-f possessed a more lipophilic group at position-1 and pendent aryl moiety para to NH moiety. Furthermore, conversion of carbonyl moiety of 9e,f to the thio-carbonyl led to benzoimidazolethiones 15a,b with significantly improved potency and binding affinity.     

Occurrence, regulation, and significance of progesterone receptors in human meningioma

The abundant expression of progesterone receptors (PR) in human meningiomas is well established. It is unknown, however, how PR expression is regulated, especially since estrogen receptors (ER) are virtually absent in these tumors. At the mRNA level, ER splice variants occur in meningioma but these appear not to be involved in the apparently autonomous PR expression. In an earlier study, because other ER-inducible proteins were either not expressed at all (pS2) or were expressed at a very low level compared to their expression in breast cancer (Cathepsin-D), the authors have postulated that the autonomous PR expression in meningioma is PR promoter-related rather than ER-related and have studied PR expression in cultured meningioma cells. PR levels appeared to decrease rapidly in vitro in monolayer as well as in three dimensional spheroid cultures. Culture conditions thus are not yet sufficient for the quantitative evaluation of PR expression. To evaluate whether PR deterioration is associated with cell turnover (meningiomas grow much faster in vitro than in vivo), the relationship between expression of the apoptotic proteins Bcl-2 and Bax and PR expression was investigated. Bcl-2 expression was found to be highest in meningioma with low PR levels, and in breast cancer tissue with high PR levels. Bax expression was not related to PR expression in any of the two tissues. Given the potential benefit of antiprogestin treatment and the occurrence in meningiomas of a protein capable of binding to the estrogen-responsive element, the expression of PR in meningioma remains a fascinating phenomenon which requires further investigation.     

Antitumor effects of combination toremifene and medroxyprogesterone acetate (MPA) in vitro and in vivo

The estrogen (ER) and progesterone (PgR) receptor levels in various gynecological tumors were measured. The same tumors were exposed in vitro to toremifene, MPA or their combination and the growth of the tumors was followed by measuring the adenosine triphosphate (ATP) within the cells by a simple bioluminescence assay. Altogether 34 clinical samples were studied. DMBA-induced mammary tumors bearing rats were treated in vivo with toremifene, MPA and their combination. About half of the ovarian cancers and 6 out of the 7 adenocarcinomas of uteri contained ER. The ovarian tumors were PgR rich in 25% and adenocarcinomas of uteri in 6 out of the 7 cases. When compared to control toremifene (concentration 1 mumol/l) was able to decrease the number of living cells to 50% or less in 9/34 samples, MPA (concentration 10 mumol/l) in 17/34 samples, and the combination in 25/34 samples. In five cases the antitumor effect of the combination was synergistic. In two cases signs of weak antagonism were seen. In vivo the antitumor effect of toremifene and MPA was clearly synergistic against DMBA-induced cancers. The effect was dose-dependent and at sufficiently high doses it was possible to eradicate the tumors and cure the animals.     

The effects of sequential treatment with ethynyloestradiol and medroxyprogesterone acetate on oestrogen and progestogen receptors in breast cancer

As part of a clinical study designed to modulate oestrogen and progestogen receptor (ER and PR) binding site concentrations prior to chemotherapy ER and PR levels have been estimated immediately before treatment, after ethynyloestradiol (EE, 10 micrograms/day, 1 week) and after medroxyprogesterone acetate (MPA, 500 mg/day i.m., 2 weeks) in tumour tissue from 14 women with advanced breast cancer. There was no consistent change after EE treatment. MPA tended to decrease ER and PR levels, though some increases were also seen. Responses (10 complete and 3 partial remissions) to sequential cyclical hormono-chemotherapy were not related to ER or PR levels prior to chemotherapy.     

Synthesis, anti-inflammatory, analgesic and antioxidant activities of some tetrasubstituted thiophenes

Sets of tetrasubstituted thiophene esters 4a-4g, 5a-5f and 6a-6e were synthesized by reaction of 1-(alpha-Carbomethoxy-beta-aminothiocrotonoyl)-aryl/aroyl amines (3) with 3-(bromoacetyl)coumarin, 1,4-dibromodiacetyl and chloroacetone respectively. The compound 3 were synthesized by nucleophilic addition of aryl/aroylisothiocyanate and enamine (2). The synthesized targeted compounds (4a-4g, 5a-5f and 6a-6e) were evaluated for their in vivo anti-inflammatory activity in carrageenin-induced rat hind paw oedema model at three graded doses employed at 10, 20 and 40 mg/kg body weight using mefanamic acid, ibuprofen and in vivo analgesic activity in acetic acid induced writhing response model at 10 mg/kg dose using ibuprofen as standard drug. The compounds 4a-4f, 5c, 5f, 6c and 6e were evaluated for their in vitro antioxidant nitric oxide radical scavenging assay at the concentrations of 5, 10, 15, 20, 25, 30 and 35 microg/mL using ascorbic acid as standard drug. Among all the targeted compounds 4c showed maximum anti-inflammatory activity of 71% protection at 10 mg/kg and 77% protection at 20 mg/kg to inflamed paw and analgesic activity of 56% inhibition and also maximum in vitro nitric oxide radical scavenging activity having IC(50) value 31.59 microg/mL.     

The human Vps29 retromer component is a metallo-phosphoesterase for a cation-independent mannose 6-phosphate receptor substrate peptide

The retromer complex is involved in the retrograde transport of the CI-M6PR (cation-independent mannose 6-phosphate receptor) from endosomes to the Golgi. It is a hetero-trimeric complex composed of Vps26 (vacuolar sorting protein 26), Vps29 and Vps35 proteins, which are conserved in eukaryote evolution. Recently, elucidation of the crystal structure of Vps29 revealed that Vps29 contains a metallo-phosphoesterase fold [Wang, Guo, Liang, Fan, Zhu, Zang, Zhu, Li, Teng, Niu et al. (2005) J. Biol. Chem. 280, 22962-22967; Collins, Skinner, Watson, Seaman and Owen (2005) Nat. Struct. Mol. Biol. 12, 594-602]. We demonstrate that recombinant hVps29 (human Vps29) displays in vitro phosphatase activity towards a serine-phosphorylated peptide, containing the acidic-cluster dileucine motif of the cytoplasmatic tail of the CI-M6PR. Efficient dephosphorylation required the additional presence of recombinant hVps26 and hVps35 proteins, which interact with hVps29. Phosphatase activity of hVps29 was greatly decreased by alanine substitutions of active-site residues that are predicted to co-ordinate metal ions. Using inductively coupled plasma MS, we demonstrate that recombinant hVps29 binds zinc. Moreover, hVps29-dependent phosphatase activity is greatly reduced by non-specific and zinc-specific metal ion chelators, which can be completely restored by addition of excess ZnCl2. The binuclear Zn2+ centre and phosphate group were modelled into the hVps29 catalytic site and pKa calculations provided further insight into the molecular mechanisms of Vps29 phosphatase activity. We conclude that the retromer complex displays Vps29-dependent in vitro phosphatase activity towards a serinephosphorylated acidic-cluster dileucine motif that is involved in endosomal trafficking of the CI-M6PR. The potential significance of these findings with respect to regulation of transport of cycling trans-Golgi network proteins is discussed.     

Identification of a phosphorylation site in the hinge region of the human progesterone receptor and additional amino-terminal phosphorylation sites

We have previously reported the identification of seven in vivo phosphorylation sites in the amino-terminal region of the human progesterone receptor (PR). From our previous in vivo studies, it was evident that several phosphopeptides remained unidentified. In particular, we wished to determine whether human PR contains a phosphorylation site in the hinge region, as do other steroid receptors including chicken PR, human androgen receptor, and mouse estrogen receptor. Previously, problematic trypsin cleavage sites hampered our ability to detect phosphorylation sites in large incomplete tryptic peptides. Using a combination of mass spectrometry and in vitro phosphorylation, we have identified six previously unidentified phosphorylation sites in human PR. Using nanoelectrospray ionization mass spectrometry, we have identified two new in vivo phosphorylation sites, Ser(20) and Ser(676), in baculovirus-expressed human PR. Ser(676) is analogous to the hinge site identified in other steroid receptors. Additionally, precursor ion scans identified another phosphopeptide that contains Ser(130)-Pro(131), a likely candidate for phosphorylation. In vitro phosphorylation of PR with Cdk2 has revealed five additional in vitro Cdk2 phosphorylation sites: Ser(25), Ser(213), Thr(430), Ser(554), and Ser(676). At least two of these, Ser(213) and Ser(676), are authentic in vivo sites. We confirmed the presence of the Cdk2-phosphorylated peptide containing Ser(213) in PR from in vivo labeled T47D cells, indicating that this is an in vivo site. Our combined studies indicate that most, if not all, of the Ser-Pro motifs in human PR are sites for phosphorylation. Taken together, these data indicate that the phosphorylation of PR is highly complex, with at least 14 phosphorylation sites.     

Regulation of cell growth of a progestin-dependent murine mammary carcinoma in vitro: progesterone receptor involvement in serum or growth factor-induced cell proliferation

Primary cultures of the medroxyprogesterone acetate-induced mouse mammary tumor line C4-HD are stimulated by medroxyprogesterone acetate (MPA) or progesterone. Serum obtained from ovariectomized, MPA-treated animals (OVX-MPA) exerts a stimulatory effect that is significantly higher than that induced by serum obtained from OVX mice with the exogenous addition of MPA, suggesting the involvement of MPA-induced serum factors potentiating the proliferative effect of MPA. The object of this paper is to further explore the stimulatory effect of mouse serum and to investigate the role of aFGF and bFGF on cell proliferation. The role of PR as possible mediators was tested using two different antiprogestins and antisense oligodeoxynucleotides of PR A isoform. Serum was obtained from OVX untreated or MPA-treated mice and was charcoalized and/or heat-inactivated. The effect of MPA or mifepristone at 10 nM concentrations was tested. Charcoalization and heat inactivation exerted a stimulatory effect (P<0.01) when OVX-serum was used. This effect was potentiated by MPA. Charcoalized OVX-MPA serum induced a significant inhibition of cell proliferation that was restored by the exogenous addition of MPA or by heat inactivation. Mifepristone induced an inhibition of ³H-thymidine uptake when OVX-MPA serum was used. These results suggest that serum factors activated by different manipulations may replace the stimulatory effect of MPA. When charcoalized fetal calf serum (chFCS) was used, a higher proliferative activity was obtained using higher serum concentrations. Mifepristone and onapristone 10 nM also inhibited this effect. aFGF and bFGF 100 ng/ml were both able to stimulate ³H-thymidine uptake. MPA exerted an additive effect. Mifepristone 10 nM inhibited bFGF and MPA+bFGF induced cell proliferation. Antisense oligodeoxynucleotides of PR (ASPR) were used to further confirm the participation of PR in the proliferative pathway of these cells. They inhibited serum and bFGF-induced cell proliferation in a specific dose-dependent manner. Our results suggest that PR play a central role in proliferation and suggest the existence of a cross-talk between steroid and growth factor signaling pathways.     

Effect of polymer structure on micelles formed between siRNA and cationic block copolymer comprising thiols and amidines

Small interfering RNA (siRNA) has great therapeutic potential for the suppression of proteins associated with disease, but delivery methods are needed for improved efficacy. Here, we investigated the properties of micellar siRNA delivery vehicles prepared with poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) comprising lysine amines modified to contain amidine and thiol functionality. Lysine modification was achieved using 2-iminothiolane (2-IT) [yielding PEG-b-PLL(N2IM-IM)] or dimethyl 3,3'-dithiobispropionimidate (DTBP) [yielding PEG-b-PLL(MPA)], with modifications aimed to impart disulfide cross-linking ability without compromising cationic charge. These two lysine modification reagents resulted in vastly different chemistry contained in the reacted block copolymer, which affected micelle formation behavior and stability along with in vitro and in vivo performance. Amidines formed with 2-IT were unstable and rearranged into a noncharged ring structure lacking free thiol functionality, whereas amidines generated with DTBP were stable. Micelles formed with siRNA and PEG-b-PLL(N2IM-IM) at higher molar ratios of polymer/siRNA, while PEG-b-PLL(MPA) produced micelles only near stoichiometric molar ratios. In vitro gene silencing was highest for PEG-b-PLL(MPA)/siRNA micelles, which were also more sensitive to disruption under disulfide-reducing conditions. Blood circulation was most improved for PEG-b-PLL(N2IM-IM)/siRNA micelles, with a circulation half-life 3× longer than naked siRNA. Both micelle formulations are promising for siRNA delivery applications in vitro and in vivo.