A Novel Class of Ribosome Modulating Agents Exploits Cancer Ribosome Heterogeneity to Selectively Target the CMS2 Subtype of Colorectal Cancer.

Ribosomes in cancer cells accumulate numerous patient-specific structural and functional modifications that facilitate tumor progression by modifying protein translation. We have taken a unique synthetic chemistry approach to generate novel macrolides, Ribosome modulating agents (RMA), that are proposed to act distal to catalytic sites and exploit cancer ribosome heterogeneity. The RMA ZKN-157 shows two levels of selectivity: (i) selective translation inhibition of a subset of proteins enriched for components of the ribosome and protein translation machinery that are upregulated by MYC; and (ii) selective inhibition of proliferation of a subset of colorectal cancer cell lines. Mechanistically, the selective ribosome targeting in sensitive cells triggered cell-cycle arrest and apoptosis. Consequently, in colorectal cancer, sensitivity to ZKN-157 in cell lines and patient-derived organoids was restricted to the consensus molecular subtype 2 (CMS2) subtype that is distinguished by high MYC and WNT pathway activity. ZKN-157 showed efficacy as single agent and, the potency and efficacy of ZKN-157 synergized with clinically approved DNA-intercalating agents which have previously been shown to inhibit ribogenesis as well. ZKN-157 thus represents a new class of ribosome modulators that display cancer selectivity through specific ribosome inhibition in the CMS2 subtype of colorectal cancer potentially targeting MYC-driven addiction to high protein translation. Significance: This study demonstrates that ribosome heterogeneity in cancer can be exploited to develop selective ribogenesis inhibitors. The colorectal cancer CMS2 subtype, with a high unmet need for therapeutics, shows vulnerability to our novel selective ribosome modulator. The mechanism suggests that other cancer subtypes with high MYC activation could also be targeted.

Minimization of drug-drug interaction risk and candidate selection in a natural product-based class of gamma-secretase modulators.

Early lead compounds in this gamma secretase modulator series were found to potently inhibit CYP3A4 and other human CYP isoforms increasing their risk of causing drug-drug-interactions (DDIs). Using structure-activity relationships and CYP3A4 structural information, analogs were developed that minimized this DDI potential. Three of these new analogs were further characterized by rat PK, rat PK/PD and rat exploratory toxicity studies resulting in selection of SPI-1865 (14) as a preclinical development candidate.

Efficacy of SPI-1865, a novel gamma-secretase modulator, in multiple rodent models.

INTRODUCTION: Modulation of the gamma-secretase enzyme, which reduces the production of the amyloidogenic Aß42 peptide while sparing the production of other Aß species, is a promising therapeutic approach for the treatment of Alzheimer's disease. Satori has identified a unique class of small molecule gamma-secretase modulators (GSMs) capable of decreasing Aß42 levels in cellular and rodent model systems. The compound class exhibits potency in the nM range in vitro and is selective for lowering Aß42 and Aß38 while sparing Aß40 and total Aß levels. In vivo, a compound from the series, SPI-1865, demonstrates similar pharmacology in wild-type CD1 mice, Tg2576 mice and Sprague Dawley rats. METHODS: Animals were orally administered either a single dose of SPI-1865 or dosed for multiple days. Aß levels were measured using a sensitive plate-based ELISA system (MSD) and brain and plasma exposure of drug were assessed by LC/MS/MS. RESULTS: In wild-type mice using either dosing regimen, brain Aß42 and Aß38 levels were decreased upon treatment with SPI-1865 and little to no statistically meaningful effect on Aß40 was observed, reflecting the changes observed in vitro. In rats, brain Aß levels were examined and similar to the mouse studies, brain Aß42 and Aß38 were lowered. Comparable changes were also observed in the Tg2576 mice, where Aß levels were measured in brain as well as plasma and CSF. CONCLUSIONS: Taken together, these data indicate that SPI-1865 is orally bioavailable, brain penetrant, and effective at lowering Aß42 in a dose responsive manner. With this unique profile, the class of compounds represented by SPI-1865 may be a promising new therapy for Alzheimer's disease.

Discovery of a novel pharmacological and structural class of gamma secretase modulators derived from the extract of Actaea racemosa.

A screen of a library of synthetic drugs and natural product extracts identified a botanical extract that modulates the processing of amyloid precursor protein (APP) in cultured cells to produce a lowered ratio of amyloid-beta peptide (1-42) (Aß42) relative to Aß40. This profile is of interest as a potential treatment for Alzheimer's disease. The extract, from the black cohosh plant (Actaea racemosa), was subjected to bioassay guided fractionation to isolate active components. Using a combination of normal-phase and reverse-phase chromatography, a novel triterpene monoglycoside, 1, was isolated. This compound was found to have an IC(50) of 100 nM for selectively reducing the production of amyloidogenic Aß42 while having a much smaller effect on the production of Aß40 (IC(50) 6.3 µM) in cultured cells overexpressing APP. Using IP-MS methods, this compound was found to modulate the pool of total Aß produced by reducing the proportion of Aß42 while increasing the relative amounts of shorter and less amyloidogenic Aß37 and Aß39. Concentrations of 1 sufficient to lower levels of Aß42 substantially (up to 10 µM) did not significantly affect the processing of Notch or other aspects of APP processing. When 1 (10 µg) was administered to CD-1 normal mice intracerebroventricularly, the level of Aß42 in brain was reduced. Assays for off-target pharmacology and the absence of overt signs of toxicity in mice dosed with compound 1 suggest a comparatively selective pharmacology for this triterpenoid. Compound 1 represents a new lead for the development of potential treatments for Alzheimer's disease via modulation of gamma-secretase.

Optimization of a natural product-based class of γ-secretase modulators.

A series of triterpene-based γ-secretase modulators is optimized. An acetate present at the C24 position of the natural product was replaced with either carbamates or ethers to provide compounds with better metabolic stability. With one of those pharmacophores in place at C24, morpholines or carbamates were installed at the C3 position to refine the physicochemical properties of the analogues. This strategy gave compounds with low clearance and good distribution into the central nervous system (CNS) of CD-1 mice. Two of these compounds, 100 and 120, were tested for a pharmacodynamic effect in the strain and lowered brain Aß42 levels.

Modulation of gamma-secretase for the treatment of Alzheimer's disease.

The Amyloid Hypothesis states that the cascade of events associated with Alzheimer's disease (AD)-formation of amyloid plaques, neurofibrillary tangles, synaptic loss, neurodegeneration, and cognitive decline-are triggered by Aß peptide dysregulation (Kakuda et al., 2006, Sato et al., 2003, Qi-Takahara et al., 2005). Since γ-secretase is critical for Aß production, many in the biopharmaceutical community focused on γ-secretase as a target for therapeutic approaches for Alzheimer's disease. However, pharmacological approaches to control γ-secretase activity are challenging because the enzyme has multiple, physiologically critical protein substrates. To lower amyloidogenic Aß peptides without affecting other γ-secretase substrates, the epsilon (ε) cleavage that is essential for the activity of many substrates must be preserved. Small molecule modulators of γ-secretase activity have been discovered that spare the ε cleavage of APP and other substrates while decreasing the production of Aß(42). Multiple chemical classes of γ-secretase modulators have been identified which differ in the pattern of Aß peptides produced. Ideally, modulators will allow the ε cleavage of all substrates while shifting APP cleavage from Aß(42) and other highly amyloidogenic Aß peptides to shorter and less neurotoxic forms of the peptides without altering the total Aß pool. Here, we compare chemically distinct modulators for effects on APP processing and in vivo activity.

Initial Optimization of a New Series of γ-Secretase Modulators Derived from a Triterpene Glycoside.

The discovery of a new series of γ-secretase modulators is disclosed. Starting from a triterpene glycoside γ-secretase modulator that gave a very low brain-to-plasma ratio, initial SAR and optimization involved replacement of a pendant sugar with a series of morpholines. This modification led to two compounds with significantly improved central nervous system (CNS) exposure.

A benzannulation strategy for the synthesis of phenols and heteroaromatic compounds based on the reaction of (trialkylsilyl)vinylketenes with lithium ynolates.

(Trialkylsilyl)vinylketenes react with lithium ynolates to generate 3-(oxido)dienylketenes which undergo rapid 6π-electrocyclization. The ultimate products of this benzannulation are highly substituted resorcinol monosilyl ethers which are formed via a [1,3] carbon to oxygen silyl group shift. Further transformations of the benzannulation products are described providing efficient access to ortho-benzoquinones and benzofuran, benzoxepine, and benzoxocine ring systems.

Reactions of (trialkylsilyl)vinylketenes with lithium ynolates: a new benzannulation strategy.

(Trialkylsilyl)vinylketenes react with lithium ynolates to produce highly substituted phenols in a new benzannulation strategy that proceeds via the 6pi electrocyclization of an intermediate 3-(oxido)dienylketene. [reaction: see text]