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Abstract Although mutated Ras protein is well recognized as an important drug target, direct targeting Ras has proven to be a daunting task. Recent studies demonstrated that Ras protein needs PDEδ to relocate to plasma membrane to execute its signaling transduction function, which provides a new avenue for modulating the Ras protein. To find small molecules antagonizing the interactions between PDEδ and Ras, here we presented a successful application of fragment-based drug discovery of PDEδ inhibitors. Under the guidance of crystal structures, we are able to quickly optimize the initial fragment into highly potent inhibitors, with more than 2000-fold improvement in binding activity, which further adds to the arsenal towards the inhibition of Ras signaling in cancer therapy. Graphical abstract Image 1 Highlights • Fragment-based approach was used to discover a new chemotype targeting PDEδ-Ras interaction. • Scaffold modification was undertaken on the basis of co-crystal structure and resulted in an optimizable hit. • Two rounds of optimization quickly improved the binding activity by more than 1000 fold. • Biological study indicates the PDEδ-Ras inhibitor could affect the downstream Ras signaling. [ABSTRACT FROM AUTHOR]

Approximately 20% of multiple myeloma (MM) are caused by a chromosomal translocation t (4; 14) that leads to the overexpression of the nuclear receptor binding SET domain-protein 2 (NSD2) histone methyltransferase. NSD2 catalyzes the methylation of lysine 36 on histone H3 (H3K36me2) and is associated with transcriptionally active regions. Using high-throughput screening (HTS) with biological analyses, a series of 5-aminonaphthalene derivatives were designed and synthesized as novel NSD2 inhibitors. Among all the prepared compounds, 9c displayed a good NSD2 inhibitory activity (IC 50 = 2.7 μM) and selectivity against both SET-domain-containing and non-SET-domain-containing methyltransferases. Preliminary research indicates the inhibition mechanism of compound 9c by significantly suppressed the methylation of H3K36me2. Compound 9c specifically inhibits the proliferation of the human B cell precursor leukemia cell line RS4:11 and the human myeloma cell line KMS11 by inducing cell cycle arrest and apoptosis with little cytotoxicity. It has been reported that the anti-cancer effect of compound 9c is partly achieved by completely suppressing the transcriptional activation of NSD2-targeted genes. When administered intraperitoneally at 25 mg/kg, compound 9c suppressed the tumor growth of RS4:11 xenografts in vivo and no body weight loss was detected in the tested SCID mice. [Display omitted] • 5-aminonaphthalene derivatives were designed, synthesized and evaluated, the SAR of these compounds was demonstrated. • Compound 9c exhibited a good NSD2 inhibitory activity and inhibited the proliferation of leukemia cell line. • The anti-cancer effect of 9c is partly achieved by suppressing the transcriptional activation of NSD2-targeted genes. • When administered intraperitoneally at 25 mg/kg, compound 9c suppressed the tumor growth of RS4:11 xenografts in vivo. [ABSTRACT FROM AUTHOR]