Tianbao Lu

Benzodiazepinedione inhibitors of the Hdm2:p53 complex suppress human tumor cell proliferation in vitro and sensitize tumors to doxorubicin in vivo.

The activity and stability of the p53 tumor suppressor are regulated by the human homologue of the mouse double minute 2 (Hdm2) oncoprotein. It has been hypothesized that small molecules disrupting the Hdm2:p53 complex would allow for the activation of p53 and result in growth suppression. We have identified small-molecule inhibitors of the Hdm2:p53 interaction using our proprietary ThermoFluor microcalorimetry technology. Medicinal chemistry and structure-based drug design led to the development of an optimized series of benzodiazepinediones, including TDP521252 and TDP665759. Activities were dependent on the expression of wild-type (wt) p53 and Hdm2 as determined by lack of potency in mutant or null p53-expressing cell lines or cells engineered to no longer express Hdm2 and wt p53. TDP521252 and TDP665759 inhibited the proliferation of wt p53-expressing cell lines with average IC50s of 14 and 0.7 μmol/L, respectively. These results correlated with the direct cellular dissociation of Hdm2 from wt p53 observed within 15 minutes in JAR choriocarcinoma cells. Additional activities of these inhibitors in vitro include stabilization of p53 protein levels, up-regulation of p53 target genes in a DNA damage–independent manner, and induction of apoptosis in HepG2 cells. Administration of TDP665759 to mice led to an increase in p21waf1/cip1 levels in liver samples. Finally, TDP665759 synergizes with doxorubicin both in culture and in an A375 xenograft model to decrease tumor growth. Taken together, these data support the potential utility of small-molecule inhibitors of the Hdm2:p53 interaction for the treatment of wt p53-expressing tumors. [Mol Cancer Ther 2006;5(1):160–9]

Substituted 1,4-benzodiazepine-2,5-diones as α-helix mimetic antagonists of the HDM2-p53 protein-protein interaction

Small molecule antagonists of protein–protein interactions represent a particular challenge for pharmaceutical discovery. One approach to finding molecules that can disrupt these interactions is to seek mimics of common protein structure motifs. We present an analysis of how molecules based on the 1,4‐benzodiazepine‐2,5‐dione scaffold serve to mimic the side‐chains presented by the hydrophobic face of two turns of an α‐helix derived from the tumor suppressor protein p53, and thus antagonize the HDM2‐p53 protein–protein binding interaction.

Synthesis of a novel series of tetra-substituted furan[3,2-b]pyrroles

Furan[3,2-b]pyrroles are important isosteres for the indole scaffold in which the benzene ring is replaced by the furan ring. A series of novel tetra-substituted furan[3,2-b]pyrroles was synthesized from a simple furaldehyde. The divergent synthesis allows for substitution on multiple positions on the scaffold, creating the potential for the formation of large libraries.

Oxyguanidines: application to non-peptidic phenyl-based thrombin inhibitors.

Although thrombin has been extensively researched with many examples of potent and selective inhibitors, the key characteristics of oral bioavailability and long half-life have been elusive. We report here a novel series non-peptidic phenyl-based, highly potent, highly selective and orally bioavailable thrombin inhibitors using oxyguanidines as guanidine-mimetics.

In vitro evaluation and crystallographic analysis of a new class of selective, non-amide-based thrombin inhibitors

We describe the in vitro evaluation and crystallographic analysis of a new class of potent and selective, non-amino acid-based, small-molecule thrombin inhibitors, exemplified by 14. This class of achiral inhibitors lacks an amide-based backbone, exhibits nM inhibition of thrombin, and is selective for thrombin. Compound 14 does not interact with the active-site catalytic apparatus and is anchored to the enzyme via a single network of hydrogen bonds to Asp189 of the S1 pocket.

Discovery and clinical evaluation of 1-{N-[2-(amidinoaminooxy)ethyl]amino}carbonylmethyl-6-methyl-3-[2,2-difluoro-2-phenylethylamino]pyrazinone (RWJ-671818), a thrombin inhibitor with an oxyguanidine P1 motif.

We have identified RWJ-671818 (8) as a novel, low molecular weight, orally active inhibitor of human alpha-thrombin (K(i) = 1.3 nM) that is potentially useful for the acute and chronic treatment of venous and arterial thrombosis. In a rat deep venous thrombosis model used to assess antithrombotic efficacy, oral administration of 8 at 30 and 50 mg/kg reduced thrombus weight by 87 and 94%, respectively. In an anesthetized rat antithrombotic model, where electrical stimulation of the carotid artery created a thrombus, 8 prolonged occlusion time 2- and 3-fold at 0.1 and 1.0 mg/kg, i.v., respectively, and more than doubled activated clotting time and activated partial thromboplastin time at the higher dose. This compound had excellent oral bioavailability of 100% in dogs with an estimated half-life of approximately 3 h. On the basis of its noteworthy preclinical data, 8 was advanced into human clinical trials and successfully progressed through phase 1 studies.

Orally efficacious thrombin inhibitors with cyanofluorophenylacetamide as the P2 motif

2-Cyano-6-fluorophenylacetamide was explored as a novel P2 scaffold in the design of thrombin inhibitors. Optimization around this structural motif culminated in 14, which is a potent thrombin inhibitor (K(i)=1.2nM) that exhibits robust efficacy in canine anticoagulation and thrombosis models upon oral administration.

Exploration of Potential Prodrugs of RWJ-445167, an Oxyguanidine-based Dual Inhibitor of Thrombin and Factor Xa

Compound 2 (RWJ‐445167; 3DP‐10017), a dual inhibitor of thrombin and factor Xa, was advanced into human clinical studies. However, its oral bioavailability in humans proved to be below acceptable limits. To address this issue, we explored a prodrug approach involving numerous guanidine derivatives. Prodrug candidates of classes A (carbamate derivatives), B (imidate derivatives), and C (alkyl and acyl derivatives), compounds 3–6, were synthesized and evaluated for anticoagulant activity at 2h after oral administration to rats. In comparison to the parent drug (2), little worthwhile improvement was observed for the prodrug candidates.

Synthesis of a novel series of 10-oxa-3-aza-tricyclo[5.2.1.01,5]dec-8-en-4-ones through an intramolecular Diels–Alder reaction

Abstract The synthesis of a novel series of 10-oxa-3-aza-tricyclo[5.2.1.0 1,5 ]dec-8-en-4-ones through the use of the intramolecular Diels–Alder reaction is presented. The use of this reaction allows for the synthesis of functionalized polycyclic systems in a stereocontrolled manner.

Non-peptidic phenyl-Based thrombin inhibitors: exploring structural requirements of the S1 specificity pocket with amidines

We expand the structural requirements and structure-activity relationship of a novel class of non-peptidic aryl-based thrombin inhibitors through exploration of the S1 specificity pocket of thrombin using flexible and constrained amidines. The most active compound of this class is 11 with Ki = 69 nM, which is ca. 15-fold less potent than constrained guanidine 5.