Hitoshi Murai

Selection of diverse and clinically relevant integrase inhibitor-resistant human immunodeficiency virus type 1 mutants

Resistance passage studies were conducted with five INIs (integrase inhibitors) that have been tested in clinical trials to date: a new naphthyridinone-type INI S/GSK-364735, raltegravir, elvitegravir, L-870,810 and S-1360. In establishing the passage system and starting from concentrations several fold above the EC(50) value, resistance mutations against S-1360 and related diketoacid-type compounds could be isolated from infected MT-2 cell cultures from day 14 to 28. Q148R and F121Y were the two main pathways of resistance to S/GSK-364735. Q148R/K and N155H, which were found in patients failing raltegravir treatment in Phase IIb studies, were observed during passage with raltegravir with this method. The fold resistance of 40 mutant molecular clones versus wild type virus was compared with these five INIs. The overall resistance pattern of S/GSK-364735 was similar to that of raltegravir and other INIs. However, different fold resistances of particular mutations were noted among different INIs, reflecting a potential to develop INIs with distinctly different resistant profiles.

Carbamoyl pyridone HIV-1 integrase inhibitors 3. A diastereomeric approach to chiral nonracemic tricyclic ring systems and the discovery of dolutegravir (S/GSK1349572) and (S/GSK1265744).

We report herein the discovery of the human immunodeficiency virus type-1 (HIV-1) integrase inhibitors dolutegravir (S/GSK1349572) (3) and S/GSK1265744 (4). These drugs stem from a series of carbamoyl pyridone analogues designed using a two-metal chelation model of the integrase catalytic active site. Structure-activity studies evolved a tricyclic series of carbamoyl pyridines that demonstrated properties indicative of once-daily dosing and superior potency against resistant viral strains. An inherent hemiaminal ring fusion stereocenter within the tricyclic carbamoyl pyridone scaffold led to a critical substrate controlled diastereoselective synthetic strategy whereby chiral information from small readily available amino alcohols was employed to control relative and absolute stereochemistry of the final drug candidates. Modest to extremely high levels of stereochemical control were observed depending on ring size and position of the stereocenter. This approach resulted in the discovery of 3 and 4, which are currently in clinical development.

Carbamoyl pyridone HIV-1 integrase inhibitors. 2. Bi- and tricyclic derivatives result in superior antiviral and pharmacokinetic profiles.

This work is a continuation of our initial discovery of a potent monocyclic carbamoyl pyridone human immunodeficiency virus type-1 (HIV-1) integrase inhibitor that displayed favorable antiviral and pharmacokinetic properties. We report herein a series of bicyclic carbamoyl pyridone analogues to address conformational issues from our initial SAR studies. This modification of the core unit succeeded to deliver low nanomolar potency in standard antiviral assays. An additional hydroxyl substituent on the bicyclic scaffold provides remarkable improvement of antiviral efficacies against clinically relevant resistant viruses. These findings led to additional cyclic tethering of the naked hydroxyl group resulting in tricyclic carbamoyl pyridone inhibitors to address remaining issues and deliver potential clinical candidates. The tricyclic carbamoyl pyridone derivatives described herein served as the immediate leads in molecules to the next generation integrase inhibitor dolutegravir which is currently in late stage clinical evaluation.

Synthesis and antiviral activity of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV integrase inhibitors.

The medicinal chemistry and structure-activity relationships for a novel series of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV-integrase inhibitors are disclosed. Substituent effects were evaluated at the N-1, C-3, and 7-benzyl positions of the naphthyridinone ring system. Low nanomolar IC(50) values were achieved in an HIV-integrase strand transfer assay with both carboxylic ester and carboxamide groups at C-3. More importantly, several carboxamide congeners showed potent antiviral activity in cellular assays. A 7-benzyl substituent was found to be critical for potent enzyme inhibition, and an N-(2-methoxyethyl)carboxamide moiety at C-3 significantly reduced plasma protein binding effects in vitro. Pharmacokinetic data in rats for one carboxamide analogue demonstrated oral bioavailability and reasonable in vivo clearance.

Carbamoyl Pyridone HIV-1 Integrase Inhibitors. 1. Molecular Design and Establishment of an Advanced Two-Metal Binding Pharmacophore

Our group has focused on expanding the scope of a two-metal binding pharmacophore concept to explore HIV-1 integrase inhibitors through medicinal chemistry efforts to design novel scaffolds which allow for improvement of pharmacokinetic (PK) and resistance profiles. A novel chelating scaffold was rationally designed to effectively coordinate two magnesium cofactors and to extend an aromatic group into an optimal hydrophobic pharmacophore space. The new chemotype, consisting of a carbamoyl pyridone core unit, shows high inhibitory potency in both enzymatic and antiviral assay formats with low nM IC₅₀ and encouraging potency shift effects in the presence of relevant serum proteins. The new inhibitor design displayed a remarkable PK profile suggestive of once daily dosing without the need for a PK booster as demonstrated by robust drug concentrations at 24 h after oral dosing in rats, dogs, and cynomolgus monkeys.

Diaminopyridine-Based Potent and Selective Mps1 Kinase Inhibitors Binding to an Unusual Flipped-Peptide Conformation

Monopolar spindle 1 (Mps1) is an attractive cancer drug target due to the important role that it plays in centrosome duplication, the spindle assembly checkpoint, and the maintenance of chromosomal stability. A design based on JNK inhibitors with an aminopyridine scaffold and subsequent modifications identified diaminopyridine 9 with an IC50 of 37 nM. The X-ray structure of 9 revealed that the Cys604 carbonyl group of the hinge region flips to form a hydrogen bond with the aniline NH group in 9. Further optimization of 9 led to 12 with improved cellular activity, suitable pharmacokinetic profiles, and good in vivo efficacy in the mouse A549 xenograft model. Moreover, 12 displayed excellent selectivity over 95 kinases, indicating the contribution of its unusual flipped-peptide conformation to its selectivity.

Indazole-based potent and cell-active Mps1 kinase inhibitors: rational design from pan-kinase inhibitor anthrapyrazolone (SP600125)

Monopolar spindle 1 (Mps1) is essential for centrosome duplication, the spindle assembly check point, and the maintenance of chromosomal instability. Mps1 is highly expressed in cancer cells, and its expression levels correlate with the histological grades of cancers. Thus, selective Mps1 inhibitors offer an attractive opportunity for the development of novel cancer therapies. To design novel Mps1 inhibitors, we utilized the pan-kinase inhibitor anthrapyrazolone (4, SP600125) and its crystal structure bound to JNK1. Our design efforts led to the identification of indazole-based lead 6 with an Mps1 IC50 value of 498 nM. Optimization of the 3- and 6-positions on the indazole core of 6 resulted in 23c with improved Mps1 activity (IC50 = 3.06 nM). Finally, application of structure-based design using the X-ray structure of 23d bound to Mps1 culminated in the discovery of 32a and 32b with improved potency for cellular Mps1 and A549 lung cancer cells. Moreover, 32a and 32b exhibited reasonable selectivities over 120 and 166 kinases, respectively.

A unique hinge binder of extremely selective aminopyridine-based Mps1 (TTK) kinase inhibitors with cellular activity

Mps1, also known as TTK, is a dual-specificity kinase that regulates the spindle assembly check point. Increased expression levels of Mps1 are observed in cancer cells, and the expression levels correlate well with tumor grade. Such evidence points to selective inhibition of Mps1 as an attractive strategy for cancer therapeutics. Starting from an aminopyridine-based lead 3a that binds to a flipped-peptide conformation at the hinge region in Mps1, elaboration of the aminopyridine scaffold at the 2- and 6-positions led to the discovery of 19c that exhibited no significant inhibition for 287 kinases as well as improved cellular Mps1 and antiproliferative activities in A549 lung carcinoma cells (cellular Mps1 IC₅₀=5.3 nM, A549 IC₅₀=26 nM). A clear correlation between cellular Mps1 and antiproliferative IC₅₀ values indicated that the antiproliferative activity observed in A549 cells would be responsible for the cellular inhibition of Mps1. The X-ray structure of 19c in complex with Mps1 revealed that this compound retains the ability to bind to the peptide flip conformation. Finally, comparative analysis of the X-ray structures of 19c, a deamino analogue 33, and a known Mps1 inhibitor bound to Mps1 provided insights into the unique binding mode at the hinge region.