Factor VIIa inhibitors: A prodrug strategy to improve oral bioavailability

Aminoisoquinoline benzamides, FLT3 and Src-family kinase inhibitors, potently inhibit proliferation of acute myeloid leukemia cell lines

AIM

Mutated or overexpressed FLT3 drives about 30% of reported acute myeloid leukemia (AML). Currently, FLT3 inhibitors have shown durable clinical responses but a complete remission of AML with FLT3 inhibitors remains elusive due to mutation-driven resistance mechanisms. The development of FLT3 inhibitors that also target other downstream oncogenic kinases may combat the resistance mechanism.

RESULTS

4-substituted aminoisoquinoline benzamides potently inhibit Src-family kinases and FLT3, including secondary mutations, such as FLT3D835. Modifications of aminoisoquinoline benzamide to aminoquinoline or aminoquinazoline abrogated FLT3 and Src-family kinase binding.

CONCLUSION

The lead aminoisoquinolines potently inhibited FLT3-driven AML cell lines, MV4-11 and MOLM-14. These aminoisoquinoline benzamides represent new kinase scaffolds with high potential to be translated into anticancer agents.

Design and Synthesis of Novel Meta-Linked Phenylglycine Macrocyclic FVIIa Inhibitors

Two novel series of meta-linked phenylglycine-based macrocyclic FVIIa inhibitors have been designed to improve the rodent metabolic stability and PK observed with the precursor para-linked phenylglycine macrocycles. Through iterative structure-based design and optimization, the TF/FVIIa K_i was improved to subnanomolar levels with good clotting activity, metabolic stability, and permeability.

Structure-Based Design of Macrocyclic Coagulation Factor VIIa Inhibitors

On the basis of a crystal structure of a phenylpyrrolidine lead and subsequent molecular modeling results, we designed and synthesized a novel series of macrocyclic FVIIa inhibitors. The optimal 16-membered macrocycle was 60-fold more potent than an acyclic analog. Further potency optimization by incorporation of P1' alkyl sulfone and P2 methyl groups provided a macrocycle with TF/FVIIa Ki = 1.6 nM, excellent selectivity against a panel of seven serine proteases, and FVII-deficient prothrombin time EC2x = 1.2 μM. Discovery of this potent, selective macrocyclic scaffold opens new possibilities for the development of orally bioavailable FVIIa inhibitors.

Tissue factor-fVIIa inhibition: update on an unfinished quest for a novel oral antithrombotic

The tissue factor-coagulation factor VIIa complex (TF-fVIIa) is a well-validated biological target and has been the focus of extensive research directed toward the discovery of novel oral antithrombotics. This review briefly summarizes the key antithrombotic target validation data and provides an update on recent advances in small molecule TF-fVIIa inhibitors.

Qualitative structure-metabolism relationships in the hydrolysis of carbamates

The aims of this review were 1) to compile a large number of reliable literature data on the metabolic hydrolysis of medicinal carbamates and 2) to extract from such data a qualitative relation between molecular structure and lability to metabolic hydrolysis. The compounds were classified according to the nature of their substituents (R³OCONR¹R²), and a metabolic lability score was calculated for each class. A trend emerged, such that the metabolic lability of carbamates decreased (i.e., their metabolic stability increased), in the following series: Aryl-OCO-NHAlkyl >> Alkyl-OCO-NHAlkyl ~ Alkyl-OCO-N(Alkyl)₂ ≥ Alkyl-OCO-N(endocyclic) ≥ Aryl-OCO-N(Alkyl)₂ ~ Aryl-OCO-N(endocyclic) ≥ Alkyl-OCO-NHAryl ~ Alkyl-OCO-NHAcyl >> Alkyl-OCO-NH₂ > Cyclic carbamates. This trend should prove useful in the design of carbamates as drugs or prodrugs.

Synthesis and antiprotozoal activity of N-alkoxy analogues of the trypanocidal lead compound 4,4'-bis(imidazolinylamino)diphenylamine with improved human blood-brain barrier permeability

To improve the blood-brain barrier permeability of the trypanocidal lead compound 4,4'-bis(imidazolinylamino)diphenylamine (1), five N-alkoxy analogues were synthesized from bis(4-isothiocyanatophenyl)amine and N-alkoxy-N-(2-aminoethyl)-2-nitrobenzenesulfonamides following successive chemical reactions in just one reactor ("one-pot procedure"). This involved: (a) formation of a thiourea intermediate, (b) removal of the amine protecting groups, and (c) intramolecular cyclization. The blood-brain barrier permeability of the compounds determined in vitro by transport assays through the hCMEC/D3 human cell line, a well-known and characterized human cellular blood-brain barrier model, showed that the N-hydroxy analogue 16 had enhanced blood-brain barrier permeability compared with the unsubstituted lead compound. Moreover, this compound displayed low micromolar IC(50) against Trypanosoma brucei rhodesiense and Plasmodium falciparum and moderate activity by intraperitoneal administration in the STIB900 murine model of acute sleeping sickness.

Pd/C-mediated synthesis of indoles in water

We describe the utility of a Pd/C-Cu mediated method in the synthesis of 2,5-disubstituted indoles in water via a coupling-cyclization strategy. Further application of this methodology has been demonstrated in the preparation of a target indole derivative via a 7-step process the key step being the Pd/C-mediated coupling reaction.

Advancement in antithrombotics for stroke prevention in atrial fibrillation

The focus of this review is the evolving field of antithrombotic drug therapy for stroke prevention in patients with atrial fibrillation (AF). The current standard of therapy includes warfarin, acenocoumarol and phenprocoumon which have proven efficacy by reducing stroke by 68% against placebo. However, a narrow therapeutic index, wide variation in metabolism, and numerous food and drug interactions have limited their clinical application to only 50% of the indicated population. Newer agents such as direct thrombin inhibitors, factor Xa inhibitors, factor IX inhibitors, tissue factor inhibitors and a novel vitamin K antagonist are being developed to overcome the limitations of current agents. The direct thrombin inhibitor dabigatran is farthest along in development. Further clinical trial testing, and eventual incorporation into clinical practice will depend on safety, efficacy and cost. Development of a novel vitamin K antagonist with better INR control will challenge the newer mechanistic agents in their quest to replace the existing vitamin K antagonists. Till then, the large unfilled gap to replace conventional agents remains open. This review will assess all these agents, and compare their mechanism of action, stage of development and pharmacologic profile.

Design, synthesis, and biological evaluation of pyrazinones containing novel P1 needles as inhibitors of TF/VIIa

Herein is described the design, synthesis, and enzymatic activity of a series of substituted pyrazinones as inhibitors of the TF/VIIa complex. These inhibitors were designed to explore replacement and variation of the P1 amidine described previously [J. Med. Chem.2003, 46, 4050]. The P1 needle replacements were selected based upon their reduced basicity compared to the parent phenyl amidine (pKa approximately 12). A contributing factor towards the oral bioavailability of a compound is the ionization state of the compound in the intestinal tract. The desired outcome of the study was to identify an orally bioavailable TF-VIIa inhibitor.

Inhibitors of Factor VIIa/tissue factor

The formation of the proteolytic complex composed of the serine protease Factor VIIa and the cell-associated glycoprotein tissue factor (FVIIa/TF) initiates a cascade of amplified zymogen activation reactions leading to thrombus formation. The critical role of the coagulation cascade in pathological thrombosis has been the basis for significant efforts to design selective inhibitors of the protease components as new anticoagulant alternatives for the treatment of thrombotic diseases. However, for the new generation of anticoagulant drugs in development that primarily target protease complexes distal from FVIIa/TF, the differential between efficacy and safety as defined by bleeding is unresolved. Targeting the FVIIa/TF complex has several theoretical advantages that exploit the amplified nature of the coagulation cascade. However, progress on the development of clinical-stage FVIIa/TF-based anticoagulants has not been as successful to date. This review summarizes recent efforts in the discovery of synthetic inhibitors of FVIIa/TF.

Carbamate prodrugs of N-alkylfuramidines

The synthesis and evaluation of 2,5-bis[4-(N-ethoxycarbonyl-N'-isopropyl)amidinophenyl]furan, 2,5-bis[4-(N-2,2,2-trichloroethoxycarbonyl-N'-isopropyl)amidinophenyl]furan and 2,5-bis[4-(N-cyclopentyl-N'-2,2,2-trichloroethoxycarbonyl)amidinophenyl]furan as prodrugs of bis-N-alkylamidines are reported. The results show that the bis-2,2,2-trichloroethyl carbamates function effectively in a rat model for Pneumocystis pneumonia.

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 2 h after oral administration to rats. In comparison to the parent drug (2), little worthwhile improvement was observed for the prodrug candidates.

Efforts toward oral bioavailability in factor VIIa inhibitors

Efforts toward developing orally bioavailable factor VIIa inhibitors starting from parenteral lead compound 1 are described. SAR resulted in improved physicochemical properties, leading to enhanced oral absorption in rat.

Potent 4-amino-5-azaindole factor VIIa inhibitors

The 4-amino-5-azaindole as an amidino-benzimidazole replacement is described. A series of potent and selective analogs were discovered and showed desirable ex vivo efficacy as measured by PT.

Novel 5-azaindole factor VIIa inhibitors

The discovery and development of 5-azaindole factor VIIa inhibitors will be described.