Inhibition of the MDM2-p53 interaction has been shown to produce an antitumor effect, especially in MDM2 amplified tumors. The isoindolinone scaffold has proved to be versatile for the discovery of MDM2-p53 antagonists. Optimization of previously reported inhibitors, for example, NU8231 (7) and NU8165 (49), was guided by MDM2 NMR titrations, which indicated key areas of the binding interaction to be explored. Variation of the 2-N-benzyl and 3-alkoxy substituents resulted in the identification of 3-(4-chlorophenyl)-3-((1-(hydroxymethyl)cyclopropyl)methoxy)-2-(4-nitrobenzyl)isoindolin-1-one (74) as a potent MDM2-p53 inhibitor (IC(50) = 0.23 ± 0.01 μM). Resolution of the enantiomers of 74 showed that potent MDM2-p53 activity primarily resided with the (+)-R-enantiomer (74a; IC(50) = 0.17 ± 0.02 μM). The cellular activity of key compounds has been examined in cell lines with defined p53 and MDM2 status. Compound 74a activates p53, MDM2, and p21 transcription in MDM2 amplified cells and shows moderate selectivity for wild-type p53 cell lines in growth inhibition assays.

CDK2 inhibitory structure-activity relationships have been explored for a range of 5-substituted O(4)-alkylpyrimidines. Variation of the 5-substituent in the 2,6-diaminopyrimidine series confirmed the 5-nitroso substituent as optimal, and showed that 5-formyl and 5-acetyl substituents were also tolerated at this position. A series of O(4)-alkyl-N(2)-aryl-5-substituted-6-aminopyrimidines revealed interesting structure-activity relationships. In the 5-nitroso series, the optimum O(4)-alkyl substituents were cyclohexylmethyl or sec-butyl, combined with a 2-sulfanilyl group. By contrast, in the N(2)-arylsulfonamido-5-formyl series, the cyclohexylmethyl compound showed relatively poor activity compared with the sec-butyl derivative (22j, (R)-4-(4-amino-6-sec-butoxy-5-formylpyrimidin-2-ylamino)benzenesulfonamide; CDK2 IC(50) = 0.8 nM). Similarly, in the N(2)-arylsulfonamido-5-(hydroxyiminomethyl) series the O(4)-sec-butyl substituent conferred greater potency than the cyclohexylmethyl (23c, (rac)-4-(4-amino-6-sec-butoxy-5-(hydroxyiminomethyl)pyrimidin-2-ylamino)benzenesulfonamide; CDK2 IC(50) = 7.4 nM). The 5-formyl derivatives show selectivity for CDK2 over other CDK family members, and are growth inhibitory in tumour cells (e.g. 22j, GI(50) = 0.57 microM).

Inhibition of murine double minute 2 (MDM2)-p53 protein−protein interaction with small molecules has been shown to reactivate p53 and inhibit tumor growth. Here, we describe rational, structure-guided, design of novel isoindolinone-based MDM2 inhibitors. MDM2 X-ray crystallography, quantum mechanics ligand-based design, and metabolite identification all contributed toward the discovery of potent in vitro and in vivo inhibitors of the MDM2-p53 interaction with representative compounds inducing cytostasis in an SJSA-1 osteosarcoma xenograft model following once-daily oral administration.

Substitution at the 7-position of the chromen-4-one pharmacophore of 8-(dibenzo[b,d]thiophen-4-yl)-2-morpholino-4H-chromen-4-one NU7441, a potent and selective DNA-dependent protein kinase (DNA-PK) inhibitor, with allyl, n-propyl or methyl enabled the resolution by chiral HPLC of atropisomers. Biological evaluation against DNA-PK of each pair of atropisomers showed a marked difference in potency, with biological activity residing exclusively in the laevorotatory enantiomer.