Cell Chemical Biology

Molecular glues are an intriguing therapeutic modality that harness small-molecules to induce interactions between proteins that typically do not interact, thus enabling the creation of novel protein functions not naturally encoded in biology. While molecular glues such as thalidomide and rapamycin have catalyzed drug discovery efforts, such molecules are rare and have often been discovered fortuitously, thus limiting their potential as a general strategy for therapeutic intervention of disease. Historically, natural products have proven to be important sources of molecular glues and we postulated that natural products bearing multiple electrophilic sites may be an unexplored source of such molecules, potentially through multi-covalent attachment. Using activity-based protein profiling (ABPP)-based chemoproteomic platforms, we show that members of the manumycin family of polyketides, which bear multiple potentially reactive sites, target C374 of the putative E3 ligase UBR7 in breast cancer cells to impair breast cancer pathogenicity through engaging in molecular glue interactions with the neo-substrate tumor-suppressor TP53, leading to the activation of p53 transcriptional activity and cell death. Our results reveal a previously undiscovered anti-cancer mechanism of this natural product family and highlight the potential for combining chemoproteomics and multi-covalent natural products for the discovery and characterization of new molecular glues.

Realising the promise of new medicines that operate through a targeted molecular glue-induced degradation mechanism requires systematic tools that can uncover the relevant principles of neomorphic protein-protein interactions. Whilst some monovalent glue degraders have been found through serendipity, the rules for small molecule attributes and the pairs or complexes of proteins that are amenable to drug-induced proximity control remain poorly articulated. Here we introduce a new approach to address this by using programmed libraries of intramolecularly edited proteins to expand protein surface landscapes and trigger new druggable interactions. We show that effector proteins, such as the E3 ligase Cereblon, can be engineered to provoke neomorphic activity by inducing the degradation of new client proteins and that these de novo interactions provide a blueprint from which new small molecule degraders can be built. As a demonstration of the approach, we use the platform to identify new non-IMiD molecular glue degraders of the oncology target GSPT1. SUMMARYO_LIMolecular glues are a highly important and promising new form of therapeutic agent, but rationalising their discovery has so far been impossible C_LIO_LIGlueSEEKER screening enables prospective monovalent drug discovery by using high-throughput deep mutational scanning to re-engineer the function of effector proteins like E3 ligases C_LIO_LIWe used this approach to enable the computational discovery of small molecule glues which degrade the oncology target GSPT1 and show how the technology can be used across new targets C_LI

Polo-like kinase 4 (PLK4) is a serine/threonine-protein kinase that plays a pivotal role in centriole biogenesis and, as such, represents a master regulator of centriole duplication. Due to its importance in cancer development and progression, PLK4 represents an attractive target for the development of novel therapeutics. Herein, we present a series of molecular degraders of PLK4, based on the highly selective PLK4 inhibitor centrinone, with the aim of targeting PLK4 for degradation via the ubiquitin-proteasome system. While all synthesized degraders retained low nanomolar binding affinities to the kinase domain of PLK4, large differences were found with respect to their ability to change cellular PLK4 levels. We uncover a complex pharmacological profile of the most potent degraders, D6 and D10, consisting of concomitant lowering of PLK4 levels through degradation, and enhancing PLK4 levels through inhibition of its autoregulation - dependent on its localization at the centrioles.

Targeted protein degradation (TPD) of neo-substrates with proteolysis targeting chimeras (PROTACs) or molecular glues has emerged as a key modality in exploring new biology as well as designing new drug candidates where catalytic inhibition is neither efficacious nor an option. TPD is mediated through harnessing E3 ligases and redirecting them to ubiquitinate de novo target proteins for subsequent proteasomal degradation. Until recently, E3 ligase chemical matter available for mediating TPD has been limited to a relatively low number of ligases, considering that over 600 E3 ligases are encoded by the human genome. In addition, the most utilized ligase for TPD approaches, CRBN, has been observed to be downregulated in settings of acquired resistance to immunomodulatory inhibitory drugs (IMiDs). IMiDs are molecular glues that target IKZF transcription factors to CRBN for degradation. Resistance is potentially accelerated by non-essentiality of CRBN for cell viability. Here we investigated if the essential E3 ligase receptor DCAF1 can be harnessed for TPD utilizing a potent, non-covalent DCAF1 binder. We show that this binder, selective for the CRL4DCAF1 E3 ligase complex, can be functionalized into an efficient DCAF1-BRD9 PROTAC. Chemical and genetic rescue experiments confirm specific degradation via the CRL4DCAF1 E3 ligase. We further highlight the versatility of DCAF1 for TPD by developing a DCAF1-dasatininb PROTAC targeting multiple cytosolic and membrane bound tyrosine kinases. We expand these findings towards Brutons tyrosine kinase (BTK) selective PROTACs and through extensive optimization and characterization efforts share key observations that led to a potent and selective DCAF1-BTK PROTAC (DBt-10). Finally, with this PROTAC DBt-10, we show rescue of BTK degradation in a BTK-dependent, CRBN-degradation-resistant cell line and provide a rationale for E3 ligase swap to overcome CRBN mediated resistance.

Chromosomal translocations leading to the fusion of tropomyosin receptor kinases (TRK) with diverse partner proteins have been identified as oncogenic drivers in many adult and pediatric cancers. While first-generation TRK kinase inhibitors, such as entrectinib and larotrectinib, have shown positive responses in TRK fusion-positive cancers, resistance mutations against these inhibitors in the kinase domain limit their efficacy. Second-generation inhibitors are in clinical evaluation, highlighting a need for novel therapeutic modalities to achieve durable suppression of the oncogenic activity of TRK fusions. Here, we developed heterobifunctional small molecule degraders (PROTACs) to achieve targeted degradation of TRK fusions. By conjugating entrectinib to thalidomide, we identified JWJ-01-378 as a potent and selective CRBN-recruiting degrader of the TPM3-TRKA fusion. JWJ-01-378 induced TPM3-TRKA degradation through the ubiquitin-proteasome system and proteomics analysis confirmed the acute selectivity of JWJ-01-378 for achieving TPM3-TRKA degradation with minimal off-target effects. While JWJ-01-378 was also able to degrade wild-type TRK, it was unable to degrade TRK inhibitor resistant mutants and ALK fusions. Importantly, TPM3-TRKA degradation by JWJ-01-378 suppressed downstream signaling and reduced cancer cell viability, with improved responses compared to heterobifunctional control compounds that cannot degrade TPM3-TRKA. Together, our study expands the toolbox of compounds for evaluating targeted degradation of TRK fusions in cancer. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/660465v1_ufig13.gif" ALT="Figure 13"> View larger version (19K): org.highwire.dtl.DTLVardef@6c78f7org.highwire.dtl.DTLVardef@179dcdeorg.highwire.dtl.DTLVardef@1939988org.highwire.dtl.DTLVardef@144c718_HPS_FORMAT_FIGEXP M_FIG C_FIG JWJ-01-378 recruits cereblon (CRBN) to induce potent and selective degradation of oncogenic TRK fusions, leading to a collapse in downstream signaling and loss of cancer cell viability. Graphical abstract was created using Biorender.com.

Targeted protein degradation (TPD) represents a potent chemical biology paradigm that leverages the cellular degradation machinery to pharmacologically eliminate specific proteins of interest. Although multiple E3 ligases have been discovered to facilitate TPD, there exists a compelling requirement to diversify the pool of E3 ligases available for such applications. This expansion will broaden the scope of potential protein targets, accommodating those with varying subcellular localizations and expression patterns. In this study, we describe a CRISPR-based transcriptional activation screen focused on human E3 ligases, with the goal of identifying E3 ligases that can facilitate heterobifunctional compound-mediated target degradation. This approach allows us to address the limitations associated with investigating candidate degrader molecules in specific cell lines that either lack or have low levels of the desired E3 ligases. Through this approach, we identified a candidate proteolysis-targeting chimera (PROTAC), 22-SLF, that induces the degradation of FKBP12 when the FBXO22 gene transcription is activated. 22-SLF induced the degradation of endogenous FKBP12 in a FBXO22-dependent manner across multiple cancer cell lines. Subsequent mechanistic investigations revealed that 22-SLF interacts with C227 and/or C228 in FBXO22 to achieve the target degradation. Finally, we demonstrated the versatility of FBXO22-based PROTACs by effectively degrading another endogenous protein BRD4. This study uncovers FBXO22 as an E3 ligase capable of supporting ligand-induced protein degradation through electrophilic PROTACs. The platform we have developed can readily be applied to elucidate protein degradation pathways by identifying E3 ligases that facilitate either small molecule-induced or endogenous protein degradation.

Glycosylation depends on tightly regulated pools of nucleotide-sugars (NS), yet the mechanisms controlling mammalian NS homeostasis and their downstream effects on glycoprotein biosynthesis remain poorly understood. UDP-galactose 4'-epimerase (GALE) catalyzes the reversible interconversion of UDP-galactose/UDP-glucose and UDP-N-acetylgalactosamine/UDP-N-acetylglucosamine, making it a central regulator of glycan precursor pools and an excellent model enzyme for studying NS metabolism. Here, we report the discovery of a cell-active small molecule inhibitor of human GALE through a high-throughput chemical screening strategy. Using a coupled luminescence-based assay, we identified the FDA-approved drug disulfiram as a GALE inhibitor. Biochemical analyses demonstrated that disulfiram directly inhibits GALE through covalent modification of cysteine residues, including C153, likely via its reactive metabolite diethyldithiocarbamate. In cultured human cells, disulfiram treatment phenocopied genetic GALE deletion, reducing terminally sialylated glycans, mucin-type O-glycans, and properly glycosylated mucin-domain glycoproteins. These effects were rescued by galactose supplementation, consistent with a mechanism of on-target GALE inhibition. Similar phenotypes were observed in human lung adenocarcinoma cells, supporting a broader role for GALE in regulating glycosylation and mucin biosynthesis across tissue types. Together, these studies establish a platform for the discovery of pharmacological GALE inhibitors as new research tools, identify disulfiram as a cell-active chemical probe for studying NS regulation, and suggest that targeting GALE might modulate mucin hypersecretion in muco-obstructive diseases and mucinous cancers.

Ewing sarcoma (EWS) is a pediatric malignancy driven by the EWSR1-FLI1 fusion protein formed by the chromosomal translocation t(11;22). The small molecule TK216 was developed as a first-in-class direct EWSR1-FLI1 inhibitor and is in phase II clinical trials in combination with vincristine for EWS patients. However, TK216 exhibits anti-cancer activity against cancer cell lines and xenografts that do not express EWSR1-FLI1, and the mechanism underlying cytotoxicity remains unresolved. We apply a forward genetics screening platform utilizing engineered hypermutation in EWS cell lines and identify recurrent mutations in TUBA1B, encoding -tubulin, that prove sufficient to drive resistance to TK216. Using reconstituted microtubule (MT) polymerization in vitro and cell-based chemical probe competition assays, we demonstrate that TK216 acts as an MT destabilizing agent. This work defines the mechanism of cytotoxicity of TK216, explains the synergy observed with vincristine, and calls for a reexamination of ongoing clinical trials with TK216.

14-3-3 proteins have the unique ability to bind and sequester a multitude of diverse phosphorylated signaling proteins and transcription factors. Many previous studies have shown that 14-3-3 interactions with specific phosphorylated substrate proteins can be enhanced through small-molecule natural product or fully synthetic molecular glue interactions. However, enhancing 14-3-3 interactions with both therapeutically intractable transcription factor substrates as well as potential neo-substrates to sequester and inhibit their function has remained elusive. One of the 14-3-3 proteins, 14-3-3{sigma} or SFN, has a cysteine C38 at the substrate binding interface near sites where previous 14-3-3 molecular glues have been found to bind. In this study, we screened a fully synthetic cysteine-reactive covalent ligand library to identify molecular glues that enhance interaction of 14-3-3{sigma} with not only druggable transcription factors such as estrogen receptor (ER), but also challenging oncogenic transcription factors such as YAP and TAZ that are part of the Hippo transducer pathway. We identified a hit EN171 that covalently targets 14-3-3 to enhance 14-3-3 interactions with ER, YAP, and TAZ leading to impaired estrogen receptor and Hippo pathway transcriptional activity. We further demonstrate that EN171 could not only be used as a molecular glue to enhance native protein interactions, but also could be used as a covalent 14-3-3 recruiter in heterobifunctional molecules to sequester nuclear neo-substrates such as BRD4 into the cytosol. Overall, our study reveals a covalent ligand that acts as a novel 14-3-3 molecular glue for challenging transcription factors such as YAP and TAZ and also demonstrates that these glues can be potentially utilized in heterobifunctional molecules to sequester nuclear neo-substrates out of the nucleus and into the cytosol to enable targeted protein localization.

The increasing incidence of antibiotic-resistant Mycobacterium tuberculosis infections is a global health threat necessitating the development of new antibiotics. Serine hydrolases (SHs) are a promising class of targets because of their importance for the synthesis of the mycobacterial cell envelope. We screened a library of small molecules containing serine-reactive electrophiles and identified narrow spectrum inhibitors of M. tuberculous growth. Using these lead molecules, we performed competitive activity-based protein profiling and identified multiple SH targets, including enzymes with uncharacterized functions. Lipidomic analyses of compound-treated cultures revealed an accumulation of free lipids and a substantial decrease in lipooligosaccharides, linking SH inhibition to defects in cell envelope biogenesis. Mutant analysis revealed a path to resistance via the synthesis of mycocerates, but not through mutations to target enzymes. Our results suggest that simultaneous inhibition of multiple SH enzymes is likely to be an effective therapeutic strategy for the treatment of M. tuberculosis infections.

Proteolysis Targeting Chimeras (PROTACs) are heterobifunctional molecules that bring a ubiquitin E3 ligase into proximity of a target protein to polyubiquitinate and degrade the target. PROTACs act catalytically, offering distinct advantages over conventional inhibitors and are the subject of intense study. The development of PROTACs involves extensive optimization of the chemical moiety linking two different protein-binding chemotypes, often requiring the synthesis, purification and testing of hundreds of PROTAC candidates. We used this approach to rapidly explore the landscape of targeted degradation of four different targets in parallel, combining and comparing a recently reported FBXO22-recruiting chemical warhead with warheads for the commonly used CRBN and VHL E3 ligases. Using a limited number of compounds (175 compounds in total) we observed no FBXO22-dependent degradation of these four targets. However, our libraries generated potent FBXO22 homo-PROTACs inducing self-degradation, as well as CRBN- and VHL-mediated degraders of FBXO22.

Targeted protein degradation (TPD) is a powerful strategy for controlling protein abundance. Here, we establish FBXO31 as a TPD-competent E3 ligase by exploiting its recognition of C-terminal amide-bearing degrons. Using an amidated Ala-Phe motif as a chemical recruiter, multiple small-molecule binders can be transformed into FBXO31-dependent degraders that induce rapid and potent target degradation. Mechanistic studies confirm FBXO31-mediated ternary complex formation and identify key residues in FBXO31 required for recruiter engagement and target degradation. We further show that an FBXO31-based multi-kinase degrader exhibits a distinct and broader degradation profile than a CRBN-based degrader, highlighting a potentially expanded degradable target space beyond CRBN.

Selective inhibition of mRNA translation is a promising strategy for modulating the activity of disease-associated genes, yet achieving both high potency and specificity remains challenging. Rocaglamide A (RocA), a molecular glue, inhibits translation by clamping eIF4A onto polypurine motifs found in many transcripts, thereby limiting RocAs specificity. Here, we developed RocASO, a chemical conjugate that links RocA to an antisense oligonucleotide (ASO) capable of base-pairing with defined mRNA sequences, thus directing RocAs clamping mechanism to chosen targets and enhancing overall potency and specificity. We show that RocASOs are compatible with various types of ASO modalities, including gapmers that induce the degradation of target RNAs. RocASOs were designed to effectively knock down endogenous genes (PTGES3, HSPA1B) and SARS-CoV-2 viral RNA, the latter conferring potent antiviral activity in cells. These findings establish RocASO as a versatile platform for programmable translational inhibition with therapeutic potential.

Targeted protein degradation has arisen as a powerful therapeutic modality for eliminating proteins. Thus far, most heterobifunctional Proteolysis Targeting Chimeras (PROTACs) have utilized recruiters against substrate receptors of Cullin RING E3 ubiquitin ligases, such as cereblon and VHL. However, previous studies have surprisingly uncovered molecular glue degraders that exploit a CUL4A adaptor protein DDB1 to degrade neosubstrate proteins. Here, we sought to investigate whether DDB1 recruiters can be discovered that can be exploited for PROTAC applications. We utilized activity-based protein profiling and cysteine chemoproteomic screening to identify a covalent recruiter that targets C173 on DDB1 and exploited this recruiter to develop PROTACs against BRD4 and androgen receptor (AR). We demonstrated that the BRD4 PROTAC results in selective degradation of the short BRD4 isoform over the long isoform in a proteasome, NEDDylation, and DDB1-dependent manner. We also demonstrated degradation of AR with the AR PROTAC in prostate cancer cells. Our study demonstrated that covalent chemoproteomic approaches can be used to discover recruiters against Cullin RING adapter proteins and that these recruiters can be used for PROTAC applications to degrade neo-substrates.

While specific cell signaling pathway inhibitors have yielded great success in oncology, directly triggering cancer cell death is one of the great drug discovery challenges facing biomedical research in the era of precision oncology. Attempts to eradicate cancer cells expressing unique target proteins, such as antibody-drug conjugates (ADCs), T-cell engaging therapies, and radiopharmaceuticals have been successful in the clinic, but they are limited by the number of targets given the inability to target intracellular proteins. More recently, heterobifunctional small molecules such as Proteolysis Targeting Chimera (PROTACs) have paved the way for protein proximity inducing therapeutic modalities. Here, we describe a proof-of-concept study using novel heterobifunctional small molecules called Regulated Induced Proximity Targeting Chimeras or RIPTACs, which elicit a stable ternary complex between a target protein selectively expressed in cancer tissue and a pan-expressed protein essential for cell survival. The resulting cooperative protein:protein interaction (PPI) abrogates the function of the essential protein, thus leading to cell death selectively in cells expressing the target protein. This approach not only opens new target space by leveraging differentially expressed intracellular proteins but also has the advantage of not requiring the target to be a driver of disease. Thus, RIPTACs can address non-target mechanisms of resistance given that cell killing is driven by inactivation of the essential protein. Using the HaloTag7-FKBP model system as a target protein, we describe RIPTACs that incorporate a covalent or non-covalent target ligand connected via a linker to effector ligands such as JQ1 (BRD4), BI2536 (PLK1), or multi-CDK inhibitors such as TMX3013 or dinaciclib. We show that these RIPTACs exhibit positive co-operativity, accumulate selectively in cells expressing HaloTag7-FKBP, form stable target:RIPTAC:effector trimers in cells, and induce an anti-proliferative response in target-expressing cells. We propose that RIPTACs are a novel heterobifunctional therapeutic modality to treat cancers that are known to selectively express a specific intracellular protein.

Endocrine resistance in breast cancer treatment is a major clinical hurdle, causing an urgent need for alternative treatment modalities. The suppressive protein-protein interaction (PPI) between Estrogen Receptor alpha (ER) and the adaptor protein 14-3-3 offers such a strategy. Here, we report the biological impact of small-molecule molecular glues of this ER/14-3-3 PPI by using both fusicoccin-derived semi-synthetic natural products and fully synthetic covalent drug-like molecules. We show that the ER/14-3-3 PPI is stabilized by both the natural- and synthetic glues, resulting in a suppression of ER transcriptional activity and a blockade of breast cancer cell proliferation, both in cell lines and in organoids derived from endocrine therapy resistant breast cancer patients. Importantly, the molecular glues effectively blocked ER action even in case of constitutively active clinical ER mutations, providing the foundations for developing alternative classes of ER targeting compounds to improve treatment of patients with endocrine-therapy resistant breast cancer. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/591105v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@173545corg.highwire.dtl.DTLVardef@a78ab7org.highwire.dtl.DTLVardef@183f4b6org.highwire.dtl.DTLVardef@371606_HPS_FORMAT_FIGEXP M_FIG C_FIG

In aging and disease, cellular NAD+ is depleted by catabolism to nicotinamide (NAM) and NAD+ supple-mentation is being pursued to enhance human healthspan and lifespan. Activation of nicoti namide phosphoribosyl -transferase (NAMPT), the rate-limiting step in NAD+ biosynthesis, has potential to increase salvage of NAM. Novel NAMPT positive allosteric modulators (N-PAMs) were discovered in addition to demonstration of NAMPT activati on by biogenic phenols. The mechanism of activation was revealed through synthesis of novel chemical probes, new NAMPT co-crystal structures, and enzyme kinetics. Binding to a rear channel in NAMPT regulates NAM binding and turnover, with biochemical observations being replicated by NAD+ measurements in human cells. The mechanism of action of N-PAMs identifies, for the first time, the role of the rear channel in regulation of NAMPT turnover coupled to feedback inhibition by NAM. N-PAM inhibition of low affinity, non-productive NAM binding via the rear channel, causes a right-shif t in KI(NAM) that accompanies an increase in enzyme activity. Conversion of an N-PAM to a high-affinity l igand blocks both high and low affinity NAM binding, ablating enzyme activity. In the presence of an N-PAM, NAMPT boosts NAD+ biosynthesis at higher NAM concentrations, in addition to relieving inhibition by NAD+. Since cellular stress often leads to enhanced catabolism of NAD+ to NAM, this mechanism is relevant to supporting cellular N AD+ levels in aging and disease. The tight regulation of cellular NAMPT is differentially regulated by N-PAMs and other activators, indicating that different classes of pharmacological activators may be engineered for cell and tissue selectivity.

Cyclin-dependent kinase 9 (CDK9) coordinates signaling events that regulate RNA polymerase II (Pol II) pause-release states. It is an important co-factor for transcription factors, such as MYC, that drive aberrant cell proliferation when their expression is deregulated. CDK9 modulation offers an approach for attenuating dysregulation in such transcriptional programs. As a result, numerous drug development campaigns to inhibit CDK9 kinase activity have been pursued. More recently, targeted degradation has emerged as an attractive approach. However, comprehensive evaluation of degradation versus inhibition is still critically needed to assess the biological contexts in which degradation might offer superior therapeutic benefits. We validated that CDK9 inhibition triggers a compensatory mechanism that dampens its effect on MYC expression and found that this feedback mechanism was absent when the kinase is degraded. Importantly, CDK9 degradation is more effective than its inhibition for disrupting MYC transcriptional regulatory circuitry likely through the abrogation of both enzymatic and scaffolding functions of CDK9. Highlights- KI-CDK9d-32 is a highly potent and selective CDK9 degrader. - KI-CDK9d-32 leads to rapid downregulation of MYC protein and mRNA transcripts levels. - KI-CDK9d-32 represses canonical MYC pathways and leads to a destabilization of nucleolar homeostasis. - Multidrug resistance ABCB1 gene emerged as the strongest resistance marker for the CDK9 PROTAC degrader.

The geroscience hypothesis states that a therapy that prevents the underlying aging process should prevent multiple aging related diseases. The mTOR (mechanistic target of rapamycin)/insulin and NAD+ (nicotinamide adenine dinucleotide) pathways are two of the most validated aging pathways. Yet, its largely unclear how they might talk to each other in aging. In genome-wide CRISPRa screening with a novel class of N-O-Methyl-propanamide-containing compounds we named BIOIO-1001, we identified lipid metabolism centering on SIRT3 as a point of intersection of the mTOR/insulin and NAD+ pathways. In vivo testing indicated that BIOIO-1001 reduced high fat, high sugar diet-induced metabolic derangements, inflammation, and fibrosis, each being characteristic of non-alcoholic steatohepatitis (NASH). An unbiased screen of patient datasets suggested a potential link between the anti-inflammatory and anti-fibrotic effects of BIOIO-1001 in NASH models to those in amyotrophic lateral sclerosis (ALS). Directed experiments subsequently determined that BIOIO-1001 was protective in both sporadic and familial ALS models. Both NASH and ALS have no treatments and suffer from a lack of convenient biomarkers to monitor therapeutic efficacy. A potential strength in considering BIOIO-1001 as a therapy is that the blood biomarker that it modulates, namely plasma triglycerides, can be conveniently used to screen patients for responders. More conceptually, to our knowledge BIOIO-1001 is a first therapy that fits the geroscience hypothesis by acting on multiple core aging pathways and that can alleviate multiple conditions after they have set in. Brief SummaryThese studies characterize a novel gerotherapy, BIOIO-1001, that identifies lipid metabolism as an intersection of the mTOR and NAD+ pathways.

Elevated expression of components of the translation initiation complex (eIF4F) is frequent in cancer and results in enhanced synthesis of oncogenic proteins. Given its essentiality in normal tissues, targeting eIF4F is challenging. Here, combining chemical and in silico screens, we identified a small molecule (M19 and its analog M19-6) that targets the MA3 domain of the eIF4F subunit eIF4G1, interferes with eIF4F assembly and alleviates melanoma resistance to BRAF and MEK inhibitors. Ribosome profiling revealed that the M19-6 selectively perturbs the melanoma translatome, limiting synthesis of factors that promote cell proliferation and neoplastic growth. Screens in melanoma models revealed that M19-6 synergizes with autophagy or HDAC inhibitors in cell culture and potentiates anti-neoplastic and anti-metastatic effects of doxorubicin in vivo. Overall, we describe a novel eIF4F complex inhibitor that offers a new therapeutic modality to target clinically challenging melanomas and could provide a molecular basis for combination with currently employed therapies.