Preclinical therapeutic efficacy of a novel blood-brain barrier-penetrant dual PI3K/mTOR inhibitor with preferential response in PI3K/PTEN mutant glioma.

Glioblastoma (GBM) is an ideal candidate disease for signal transduction targeted therapy because the majority of these tumors harbor genetic alterations that result in aberrant activation of growth factor signaling pathways. Loss of heterozygosity of chromosome 10, mutations in the tumor suppressor gene PTEN, and PI3K mutations are molecular hallmarks of GBM and indicate poor prognostic outcomes in many cancers. Consequently, inhibiting the PI3K pathway may provide therapeutic benefit in these cancers. PI3K inhibitors generally block proliferation rather than induce apoptosis. To restore the sensitivity of GBM to apoptosis induction, targeted agents have been combined with conventional therapy. However, the molecular heterogeneity and infiltrative nature of GBM make it resistant to traditional single agent therapy. Our objectives were to test a dual PI3K/mTOR inhibitor that may cross the blood-brain barrier (BBB) and provide the rationale for using this inhibitor in combination regimens to chemotherapy-induced synergism in GBM. Here we report the preclinical potential of a novel, orally bioavailable PI3K/mTOR dual inhibitor, DS7423 (hereafter DS), in in-vitro and in-vivo studies. DS was tested in mice, and DS plasma and brain concentrations were determined. DS crossed the BBB and led to potent suppression of PI3K pathway biomarkers in the brain. The physiologically relevant concentration of DS was tested in 9 glioma cell lines and 22 glioma-initiating cell (GIC) lines. DS inhibited the growth of glioma tumor cell lines and GICs at mean 50% inhibitory concentration values of less than 250 nmol/L. We found that PI3K mutations and PTEN alterations were associated with cellular response to DS treatment; with preferential inhibition of cell growth in PI3KCA-mutant and PTEN altered cell lines. DS showed efficacy and survival benefit in the U87 and GSC11 orthotopic models of GBM. Furthermore, administration of DS enhanced the antitumor efficacy of temozolomide against GBM in U87 glioma models, which shows that PI3K/mTOR inhibitors may enhance alkylating agent-mediated cytotoxicity, providing a novel regimen for the treatment of GBM. Our present findings establish that DS can specifically be used in patients who have PI3K pathway activation and/or loss of PTEN function. Further studies are warranted to determine the potential of DS for glioma treatment.

Synthesis and Structure-Activity Relationships of 2-Aminoacetamide Derivatives as Peroxisome Proliferator-Activated Receptor α/γ Dual Agonists.

We describe the design, syntheses, and structure-activity relationships of novel zwitterionic compounds as nonthiazolidinedion-based peroxisome proliferator-activated receptor (PPAR) α/γ dual agonists. In our previous report, we obtained compound 1 showing potent PPARα/γ dual agonistic activities, together with a sufficient glucose-lowering effect in db/db mice. However, this compound possessed an issue, i.e., the 1,3,4-oxadiazole ring was not stable in acidic conditions. Thus, we carried out further optimization to improve the stability while maintaining the other favorable profile features including potent PPARα/γ dual agonistic activity. We addressed the issue by changing the oxadiazole ring to a bioisostere amide group. These amide derivatives were stable in acidic conditions and decreased plasma glucose and plasma triglyceride levels significantly without marked weight gain.

A novel, potent, and orally active VLA-4 antagonist with good aqueous solubility: trans-4-[1-[[2-(5-Fluoro-2-methylphenylamino)-7-fluoro-6-benzoxazolyl]acetyl]-(5S)-[methoxy(methyl)amino]methyl-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid.

We have carried out the optimization of substituents at the C-3 or the C-5 position on the pyrrolidine ring of VLA-4 antagonist 3 with 2-(phenylamino)-7-fluorobenzoxazolyl moiety for the purpose of improving in vivo efficacy while maintaining good aqueous solubility. As a result, we successfully increased in vitro activity in the presence of 3% human serum albumin and achieved an exquisite lipophilic and hydrophilic balance of compounds suitable for oral administrative regimen. The modification resulted in the identification of zwitterionic compound 7n with (5S)-[methoxy(methyl)amino]methylpyrrolidine, which significantly alleviated bronchial hyper-responsiveness to acetylcholine chloride at 12.5mg/kg, p.o. in a murine asthma model and showed favorable aqueous solubility (JP1, 89 µg/mL; JP2, 462 µg/mL). Furthermore, this compound showed good oral bioavailability (F=54%) in monkeys.

A concise synthesis of a very late antigen-4 antagonist trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxyamide)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid via reductive etherification.

This contribution describes a concise synthesis to ethyl trans-[(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylate (2b) as a key intermediate of very late antigen-4 (VLA-4) antagonist trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxyamide)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid (1). The synthesis employs a reductive etherification as a key reaction using (2S,4S)-1-benzyloxycarbonyl-4-methoxypyrrolidine-2-carboxyaldehyde (12) and trans-4-triethylsilyloxycyclohexanecarboxilic acid ethyl ester (13b). This synthesis provides 2b in 6 steps with 38% overall yield from commercially available starting material.

Identification of trans-4-[1-[[7-fluoro-2-(1-methyl-3-indolyl)-6-benzoxazolyl]acetyl]-(4S)-fluoro-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid as a potent, orally active VLA-4 antagonist.

For the purpose of obtaining orally potent VLA-4 inhibitors, we have carried out structural modification of the (N'-phenylureido)phenyl group in compound 1, where the group was found to be attributed to poor pharmacokinetic profile in our previous research. Through modification, we have identified several compounds with both potent in vitro activity and improved oral exposure. In particular, compound 7e with 7-fluoro-2-(1-methyl-1H-indol-3-yl)-1,3-benzoxazolyl group as a novel replacement of the (N'-phenylureido)phenyl group significantly inhibited eosinophil infiltration into bronchoalveolar lavage fluid at 15mg/kg in an Ascaris-antigen-induced murine bronchial inflammatory model, and its efficacy was comparable to that of the anti-mouse α(4) antibody (R1-2).

Discovery of trans-4-[1-[[2,5-Dichloro-4-(1-methyl-3-indolylcarboxamido)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid: an orally active, selective very late antigen-4 antagonist.

We have focused on optimization of the inadequate pharmacokinetic profile of trans-4-substituted cyclohexanecarboxylic acid 5, which is commonly observed in many small molecule very late antigen-4 (VLA-4) antagonists. We modified the lipophilic moiety in 5 and found that reducing the polar surface area of this moiety results in improvement of the PK profile. Consequently, our efforts have led to the discovery of trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxamido)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid (14e) with potent activity (IC(50) = 5.4 nM) and significantly improved bioavailability in rats, dogs, and monkeys (100%, 91%, 68%), which demonstrated excellent oral efficacy in murine and guinea pig models of asthma. Based on its overall profile, compound 14e was progressed into clinical trails. In a single ascending-dose phase I clinical study, compound 14e exhibited favorable oral exposure as expected and had no serious adverse events.

A novel and potent VLA-4 antagonist based on trans-4-substituted cyclohexanecarboxylic acid.

During the course of our study, it was revealed that the poor pharmacokinetic properties of a series of benzoic acid derivatives such as 1 should be attributed to the diphenylurea moiety. Thus, we replaced the diphenylurea moiety in 1 with a 2-(2-methylphenylamino)benzoxazole moiety which mimics the diphenylurea structure. However, this modification resulted in a significant decrease (3, IC(50)=19 nM) in VLA-4 inhibitory activity compared to 1 (IC(50)=1.6 nM). To address this discrepancy, we worked on optimization of the carboxylic acid moiety in compound 3. As a result, our efforts have led to the discovery of trans-4-substituted cyclohexanecarboxylic acid derivative 11b (IC(50)=2.8 nM) as a novel and potent VLA-4 antagonist. In addition, compound 11b exhibited favorable pharmacokinetic properties (CL=3.3 ml/min/kg, F=51%) in rats.

Identification of 4-[1-[3-chloro-4-[N'-(5-fluoro-2-methylphenyl)ureido]phenylacetyl]-(4S)-fluoro-(2S)-pyrrolidinylmethoxy]benzoic acid as a potent, orally active VLA-4 antagonist.

Optimization of benzoic acid derivatives by introducing substituents into the diphenyl urea moiety led to the identification of compound 20l as a potent VLA-4 antagonist. Compound 20l inhibited eosinophil infiltration into bronchial alveolar lavage fluid in a murine asthma model by oral dosing and its efficacy was comparable to anti-mouse alpha4 antibody (R1-2). Furthermore, this compound significantly blocked bronchial hyper-responsiveness in the model.