KRAS is the most frequently mutated driver of pancreatic, colorectal, and non-small cell lung cancers. Direct KRAS blockade has proven challenging and inhibition of a key downstream effector pathway, the RAF-MEK-ERK cascade, has shown limited success due to activation of feedback networks that keep the pathway in check. We hypothesized that inhibiting SOS1, a KRAS activator and important feedback node, represents an effective approach to treat KRAS-driven cancers. We report the discovery of a highly potent, selective and orally bioavailable small-molecule SOS1 inhibitor, BI-3406, that binds to the catalytic domain of SOS1 thereby preventing the interaction with KRAS. BI-3406 reduces formation of GTPloaded RAS and limits cellular proliferation of a broad range of KRAS-driven cancers.Importantly, BI-3406 attenuates feedback reactivation induced by MEK inhibitors and thereby enhances sensitivity of KRAS-dependent cancers to MEK inhibition. Combined SOS1 and MEK inhibition represents a novel and effective therapeutic concept to address KRAS-driven tumors. SignificanceTo date, there are no effective targeted pan-KRAS therapies. In-depth characterization of BI-3406 activity and identification of MEK inhibitors as effective combination partners provide an attractive therapeutic concept for the majority of KRAS mutant cancers, including those fueled by the most prevalent mutant KRAS oncoproteins G12D, G12V, G12C and G13D.Research.
Scaffold modification based on Wang's pioneering MDM2-p53 inhibitors led to novel, chemically stable spiro-oxindole compounds bearing a spiro[3H-indole-3,2'-pyrrolidin]-2(1H)-one scaffold that are not prone to epimerization as observed for the initial spiro[3H-indole-3,3'-pyrrolidin]-2(1H)-one scaffold. Further structure-based optimization inspired by natural product architectures led to a complex fused ring system ideally suited to bind to the MDM2 protein and to interrupt its protein-protein interaction (PPI) with TP53. The compounds are highly selective and show in vivo efficacy in a SJSA-1 xenograft model even when given as a single dose as demonstrated for 4-[(3S,3'S,3'aS,5'R,6'aS)-6-chloro-3'-(3-chloro-2-fluorophenyl)-1'-(cyclopropylmethyl)-2-oxo-1,2,3',3'a,4',5',6',6'a-octahydro-1'H-spiro[indole-3,2'-pyrrolo[3,2-b]pyrrole]-5'-yl]benzoic acid (BI-0252).
BACKGROUND AND PURPOSE Subunit‐specific modulators of γ‐aminobutyric acid (GABA) type A (GABAA) receptors can help to assess the physiological function of receptors with different subunit composition and also provide the basis for the development of new drugs. Valerenic acid (VA) was recently identified as a β2/3 subunit‐specific modulator of GABAA receptors with anxiolytic potential. The aim of the present study was to generate VA derivatives as novel GABAA receptor modulators and to gain insight into the structure–activity relation of this molecule. EXPERIMENTAL APPROACH The carboxyl group of VA was substituted by an uncharged amide or amides with different chain length. Modulation of GABAA receptors composed of different subunit compositions by the VA derivatives was studied in Xenopus oocytes by means of the two‐microelectrode voltage‐clamp technique. Half‐maximal stimulation of GABA‐induced chloride currents (IGABA) through GABAA receptors (EC50) and efficacies (maximal stimulation of IGABA) were estimated. Anxiolytic activity of the VA derivatives was studied in mice, applying the elevated plus maze test. KEY RESULTS Valerenic acid amide (VA‐A) displayed the highest efficacy (more than twofold greater IGABA enhancement than VA) and highest potency (EC50= 13.7 ± 2.3 µM) on α1β3 receptors. Higher efficacy and potency of VA‐A were also observed on α1β2γ2s and α3β3γ2s receptors. Anxiolytic effects were most pronounced for VA‐A. CONCLUSIONS AND IMPLICATIONS Valerenic acid derivatives with higher efficacy and affinity can be generated. Greater in vitro action of the amide derivative correlated with a more pronounced anxiolytic effect in vivo. The data give further confidence in targeting β3 subunit containing GABAA receptors for development of anxiolytics.
KRAS, the most common oncogenic driver in human cancers, is controlled and signals primarily through protein−protein interactions (PPIs). The interaction between KRAS and SOS1, crucial for the activation of KRAS, is a typical, challenging PPI with a large contact surface area and high affinity. Here, we report that the addition of only one atom placed between Y884 SOS1 and A73 KRAS is sufficient to convert SOS1 activators into SOS1 inhibitors. We also disclose the discovery of BI-3406. Combination with the upstream EGFR inhibitor afatinib shows in vivo efficacy against KRAS G13D mutant colorectal tumor cells, demonstrating the utility of BI-3406 to probe SOS1 biology. These findings challenge the dogma that large molecules are required to disrupt challenging PPIs. Instead, a "foot in the door" approach, whereby single atoms or small functional groups placed between key PPI interactions, can lead to potent inhibitors even for challenging PPIs such as SOS1-KRAS.
The first total synthesis of (+)-lycoflexine (1), a constituent of Lycopodium clavatum var. inflexum , has been accomplished in eight steps with 13% overall yield. Our synthesis covers four one-pot reactions, including a tandem Sakurai/aldol sequence, a novel hydroboration/oxidation procedure, a deprotection/transannular Mannich reaction, and as a highlight, a tandem catalysis cascade combining an enynene ring-closing metathesis and a selective hydrogenation.
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