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TTK is an essential spindle assembly checkpoint enzyme in many organisms. It plays a central role in tumor cell proliferation and is aberrantly overexpressed in a wide range of tumor types. We recently reported on a series of potent and selective TTK inhibitors with strong antiproliferative activity in triple negative breast cancer (TNBC) cell lines (8: TTK IC50 = 3.0 nM; CAL-51 IC50 = 84.0 nM). Inspired by previously described potent tricyclic TTK inhibitor 6 (TTK IC50 = 0.9 nM), we embarked on a structure-enabled design and optimization campaign to identify an improved series with excellent potency, TTK selectivity, solubility, CYP inhibition profile, and in vivo efficacy in a TNBC xenograft model. These efforts culminated in the discovery of 25 (TTK IC50 = 3.0 nM; CAL-51 IC50 = 16.0 nM), which showed significant single-agent efficacy when dosed iv in a TNBC xenograft model without body weight loss.

Triple negative breast cancer (TNBC) is an aggressive disease with high relapse rates and few treatment options. Outlined in previous publications, we identified a series of potent, dual TTK/CLK2 inhibitors with strong efficacy in TNBC xenograft models. Pharmacokinetic properties and kinome selectivity were optimized, resulting in the identification of a new series of potent, selective, and orally bioavailable TTK inhibitors. We describe here the structure-activity relationship of the 2,4-disubstituted-7 H-pyrrolo[2,3- d]pyrimidine series, leading to significant single agent efficacy in a TNBC xenograft model without body weight loss. The design effort evolving an iv-dosed TTK/CLK2 inhibitor to an orally bioavailable TTK inhibitor is described.

We report here the synthesis and structure-activity relationship (SAR) of a novel series of triazole containing mammalian target of rapamycin (mTOR) kinase inhibitors. SAR studies examining the potency, selectivity, and PK parameters for a series of triazole containing 4,6- or 1,7-disubstituted-3,4-dihydropyrazino[2,3-b]pyrazine-2(1H)-ones resulted in the identification of triazole containing mTOR kinase inhibitors with improved PK properties. Potent compounds from this series were found to block both mTORC1(pS6) and mTORC2(pAktS473) signaling in PC-3 cancer cells, in vitro and in vivo. When assessed in efficacy models, analogs exhibited dose-dependent efficacy in tumor xenograft models. This work resulted in the selection of CC-115 for clinical development.

We report here the synthesis and structure-activity relationship (SAR) of a novel series of mammalian target of rapamycin (mTOR) kinase inhibitors. A series of 4,6- or 1,7-disubstituted-3,4-dihydropyrazino[2,3-b]pyrazine-2(1H)-ones were optimized for in vivo efficacy. These efforts resulted in the identification of compounds with excellent mTOR kinase inhibitory potency, with exquisite kinase selectivity over the related lipid kinase PI3K. The improved PK properties of this series allowed for exploration of in vivo efficacy and ultimately the selection of CC-223 for clinical development.

Heterocyclic dopamine surrogates of types 5 and 7 were synthesized and investigated for their dopaminergic properties. The enantiomerically pure biphenylcarboxamide (S)-5a displayed an outstanding K(i) of 27 pM at the agonist-labeled D(3) receptor and significant selectivity over the D(2) subtype. Measurement of [(35)S]GTPγS incorporation in the presence of a coexpressed PTX-insensitive G(α0-1) subunit indicated highly efficient G-protein coupling. Comparison of ligand efficacy data from cAMP accumulation and [(3)H]thymidine incorporation experiments revealed that ligand biased signaling is exerted by the test compound (S)-5a. Starting from the D(3) crystal structure, a combination of homology modeling and site directed mutagenesis gave valuable insights into the binding mode and the intermolecular origins of stereospecific receptor recognition. According to these data, the superior affinity of the eutomer 5a is caused by the favorable binding energy that results from interaction between the ligand's central ammonium unit and the aspartate residue in position 3.32 of the receptor.

Taking advantage of a 3D-QSAR based pharmacophore hypothesis, synthesis and biological evaluation of dopaminergic 5-aminotetrahydropyrazolo[1,5-a]pyridines are described. The data displayed substantial and selective D3 receptor affinity for the heterocyclic test compound (+/-)-1 when the enantiomer (S)-1 turned out to be responsible for the D3 binding (K(i) (high) = 4.0 nM). (S)-1 exhibited binding affinity and ligand efficacy comparable to those of our previously described D3 agonist FAUC 54, when subtype selectivity could be significantly improved. The results indicate that the sp(2) nitrogens of the pyrazole and thiazole rings of the dopaminergics (S)-1 and pramipexole, respectively, are pharmacophoric elements of major importance. To provide putative explanations for the high affinity of (S)-1, computational studies were performed employing an active state D3 model.

Employing 1,3-dipolar cycloaddition for the synthesis of the 7a-azaindole nucleus, analogues of melatonin have been synthesized and tested against human and amphibian melatonin receptors. Introducing a phenyl substituent in position 2 of the heterocyclic moiety significantly increased binding affinity to both the MT1 and MT2 receptors. Shifting the methoxy group from position 5 to 2 of the 7a-azaindole ring led to a substantial reduction of MT1 binding when MT2 recognition was maintained. We theoretically investigated the hypothesis whether the 2-methoxy function of the azamelatonin analogue 27 is able to mimic the 5-methoxy group of the neurohormone by directing its 2-methoxy function toward the methoxy binding site. DFT calculations and experimental binding differences of analogue compounds indicate that the energy gained by forming the methoxy-specific hydrogen-bond interaction should exceed the energy required for adopting an alternative conformation.

A robust understanding of the mechanoelectric response of organic semiconductors is crucial for the development of materials for flexible electronics. In particular, the prospect of using external mechanical strain to induce a controlled modulation in the charge mobility of the material is appealing. Here we develop an accurate computational protocol for the prediction of the mechanical strain dependence of charge mobility. Ab initio molecular dynamics simulations with a van der Waals density functional are carried out to quantify the off-diagonal electronic disorder in the system as a function of strain by the explicit calculation of the thermal distributions of electronic coupling matrix elements. The approach is applied to a representative molecular organic semiconductor, single-crystal rubrene. We find that charge mobility along the high-mobility direction a⃗ increases with compressive strain, as one might expect. However, the increase is larger when compressive strain is applied in the perpendicular direction than in the parallel direction with respect to a⃗, in agreement with experimental reports. We show that this seemingly counterintuitive result is a consequence of a significantly greater suppression of electronic coupling fluctuations in the range of 50–150 cm–1, when strain is applied in the perpendicular direction. Thus our study highlights the importance of considering off-diagonal electron–phonon coupling in understanding the mechanoelectric response of organic semiconducting crystals. The computational approach developed here is well suited for the accurate prediction of strain–charge mobility relations and should provide a useful tool for the emerging field of molecular strain engineering.