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Inhibition of hydroxy acid oxidase 1 (HAO1) is a strategy to mitigate the accumulation of toxic oxalate that results from reduced activity of alanine-glyoxylate aminotransferase (AGXT) in primary hyperoxaluria 1 (PH1) patients. DNA-Encoded Chemical Library (DECL) screening provided two novel chemical series of potent HAO1 inhibitors, represented by compounds 3-6. Compound 5 was further optimized via various structure-activity relationship (SAR) exploration methods to 29, a compound with improved potency and absorption, distribution, metabolism, and excretion (ADME)/pharmacokinetic (PK) properties. Since carboxylic acid-containing compounds are often poorly permeable and have potential active glucuronide metabolites, we undertook a brief, initial exploration of acid replacements with the aim of identifying non-acid-containing HAO1 inhibitors. Structure-based drug design initiated with Compound 5 led to the identification of a nonacid inhibitor of HAO1, 31, which has weaker potency and increased permeability.

Bispecific degraders (PROTACs) of ERα are expected to be advantageous over current inhibitors of ERα signaling (aromatase inhibitors/SERMs/SERDs) used to treat ER+ breast cancer. Information from DNA-encoded chemical library (DECL) screening provides a method to identify novel PROTAC binding features as the linker positioning, and binding elements are determined directly from the screen. After screening ∼120 billion DNA-encoded molecules with ERα WT and 3 gain-of-function (GOF) mutants, with and without estradiol to identify features that enrich ERα competitively, the off-DNA synthesized small molecule exemplar 7 exhibited nanomolar ERα binding, antagonism, and degradation. Click chemistry synthesis on an alkyne E3 ligase engagers panel and an azide variant of 7 rapidly generated bispecific nanomolar degraders of ERα, with PROTACs 18 and 21 inhibiting ER+ MCF7 tumor growth in a mouse xenograft model of breast cancer. This study validates this approach toward identifying novel bispecific degrader leads from DECL screening with minimal optimization.

Mer is a member of the TAM (Tyro3, Axl, Mer) kinase family that has been associated with cancer progression, metastasis, and drug resistance. Their essential function in immune homeostasis has prompted an interest in their role as modulators of antitumor immune response in the tumor microenvironment. Here we illustrate the outcomes of an extensive lead-generation campaign for identification of Mer inhibitors, focusing on the results from concurrent, orthogonal high-throughput screening approaches. Data mining, HT (high-throughput), and DECL (DNA-encoded chemical library) screens offered means to evaluate large numbers of compounds. We discuss campaign strategy and screening outcomes, and exemplify series resulting from prioritization of hits that were identified. Concurrent execution of HT and DECL screening successfully yielded a large number of potent, selective, and novel starting points, covering a range of selectivity profiles across the TAM family members and modes of kinase binding, and offered excellent start points for lead development.

The activity of the secreted phosphodiesterase autotaxin produces the inflammatory signaling molecule LPA and has been associated with a number of human diseases including idiopathic pulmonary fibrosis (IPF). We screened a single DNA-encoded chemical library (DECL) of 225 million compounds and identified a series of potent inhibitors. Optimization of this series led to the discovery of compound 1 (X-165), a highly potent, selective, and bioavailable small molecule. Cocrystallization of compound 1 with human autotaxin demonstrated that it has a novel binding mode occupying both the hydrophobic pocket and a channel near the autotaxin active site. Compound 1 inhibited the production of LPA in human and mouse plasma at nanomolar levels and showed efficacy in a mouse model of human lung fibrosis. After successfully completing IND-enabling studies, compound 1 was approved by the FDA for a Phase I clinical trial. These results demonstrate that DECL hits can be readily optimized into clinical candidates.

The discovery of ligands via affinity-mediated selection of DNA-encoded chemical libraries is driven by the quality and concentration of the protein target. G-protein-coupled receptors (GPCRs) and other membrane-bound targets can be difficult to isolate in their functional state and at high concentrations, and therefore have been challenging for affinity-mediated selection. Here, we report a successful selection campaign against protease-activated receptor 2 (PAR2). Using a thermo-stabilized mutant of PAR2, we conducted affinity selection using our >100-billion-compound DNA-encoded library. We observed a number of putative ligands enriched upon selection, and subsequent cellular profiling revealed these ligands to comprise both agonists and antagonists. The agonist series shared structural similarity with known agonists. The antagonists were shown to bind in a novel allosteric binding site on the PAR2 protein. This report serves to demonstrate that cell-free affinity selection against GPCRs can be achieved with mutant stabilized protein targets.

Libraries of DNA-Encoded small molecules created using combinatorial chemistry and synthetic oligonucleotides are being applied to drug discovery projects across the pharmaceutical industry. The majority of reported projects describe the discovery of reversible, i.e. non-covalent, target modulators. We synthesized multiple DNA-encoded chemical libraries terminated in electrophiles and then used them to discover covalent irreversible inhibitors and report the successful discovery of acrylamide- and epoxide-terminated Bruton's Tyrosine Kinase (BTK) inhibitors. We also demonstrate their selectivity, potency and covalent cysteine engagement using a range of techniques including X-ray crystallography, thermal transition shift assay, reporter displacement assay and intact protein complex mass spectrometry. The epoxide BTK inhibitors described here are the first ever reported to utilize this electrophile for this target.

We have identified and characterized novel potent inhibitors of Bruton's tyrosine kinase (BTK) from a single DNA-encoded library of over 110 million compounds by using multiple parallel selection conditions, including variation in target concentration and addition of known binders to provide competition information. Distinct binding profiles were observed by comparing enrichments of library building block combinations under these conditions; one enriched only at high concentrations of BTK and was competitive with ATP, and another enriched at both high and low concentrations of BTK and was not competitive with ATP. A compound representing the latter profile showed low nanomolar potency in biochemical and cellular BTK assays. Results from kinetic mechanism of action studies were consistent with the selection profiles. Analysis of the co-crystal structure of the most potent compound demonstrated a novel binding mode that revealed a new pocket in BTK. Our results demonstrate that profile-based selection strategies using DNA-encoded libraries form the basis of a new methodology to rapidly identify small molecule inhibitors with novel binding modes to clinically relevant targets.

Inspired by the many reported successful applications of DNA-encoded chemical libraries in drug discovery projects with protein targets, we decided to apply this platform to nucleic acid targets. We used a 120-billion-compound set of 33 distinct DNA-encoded chemical libraries and affinity-mediated selection to discover binders to a panel of DNA targets. Here, we report the successful discovery of small molecules that specifically interacted with DNA G-quartets, which are stable structural motifs found in G-rich regions of genomic DNA, including in the promoter regions of oncogenes. For this study, we chose the G-quartet sequence found in the c-myc promoter as a primary target. Compounds enriched using affinity-mediated selection against this target demonstrated high-affinity binding and high specificity over DNA sequences not containing G-quartet motifs. These compounds demonstrated a moderate ability to discriminate between different G-quartet motifs and also demonstrated activity in a cell-based assay, suggesting direct target engagement in the cell. DNA-encoded chemical libraries and affinity-mediated selection are uniquely suited to discover binders to targets that have no inherent activity outside of a cellular context, and they may also be of utility in other nucleic acid structural motifs.

ATAD2 (ANCCA) is an epigenetic regulator and transcriptional cofactor, whose overexpression has been linked to the progress of various cancer types. Here, we report a DNA-encoded library screen leading to the discovery of BAY-850, a potent and isoform selective inhibitor that specifically induces ATAD2 bromodomain dimerization and prevents interactions with acetylated histones in vitro, as well as with chromatin in cells. These features qualify BAY-850 as a chemical probe to explore ATAD2 biology.

DNA-encoded chemistry enables rapid and inexpensive syntheses and screening of vast chemical libraries, and is generating substantial interest and investment in the pharmaceutical industry. Here, Goodnow and colleagues provide an overview of the steps involved in the generation of DNA-encoded libraries, highlighting key applications and future directions for this technology. DNA-encoded chemical library technologies are increasingly being adopted in drug discovery for hit and lead generation. DNA-encoded chemistry enables the exploration of chemical spaces four to five orders of magnitude more deeply than is achievable by traditional high-throughput screening methods. Operation of this technology requires developing a range of capabilities including aqueous synthetic chemistry, building block acquisition, oligonucleotide conjugation, large-scale molecular biological transformations, selection methodologies, PCR, sequencing, sequence data analysis and the analysis of large chemistry spaces. This Review provides an overview of the development and applications of DNA-encoded chemistry, highlighting the challenges and future directions for the use of this technology.

Aptamers, a promising new class of therapeutics, are single-stranded oligonucleotides generated via an in vitro selection process that bind to and inhibit the activity of target proteins in a manner similar to therapeutic antibodies. In order to enhance the drug-like character of aptamers, oligonucleotide libraries containing modified nucleotides are increasingly being used for selection. Principally, the choice of modifications aims to increase aptamer potency by enhancing nuclease-resistance, or increasing target affinity by providing more target recognition functionality or generating more stable aptamer structures.

The generation of DNA-encoded chemical libraries requires the unimolecular association of multiple encoding oligonucleotides with encoded chemical entities during combinatorial synthesis processes. This has traditionally been achieved using enzymatic ligation. We discuss a range of chemical ligation methods that provide alternatives to enzymatic ligation. These chemical ligation methods include the generation of modified internucleotide linkages that support polymerase translocation and other modified linkages that while not supporting the translocation of polymerases can also be used to generate individual cDNA molecules containing encoded chemical information specifying individual library members. We also describe which of these approaches have been successfully utilized for the preparation of DNA-encoded chemical libraries and those that were subsequently used for the discovery of inhibitors.

The first therapeutic aptamer was approved for human use in 2004, and a range of chemical substitutions that improve the drug-like properties of aptamers has recently been shown to increase the utility of this modality. Currently there are both anticoagulant and antithrombotic aptamers in the clinic, and additionally there are a number of earlier stage projects in which a variety of cardiovascular targets are inhibited by specific aptamers and for which a wide range of therapeutic applications has been suggested.

Aptamers are short oligonucleotides that fold into well-defined three-dimensional architectures thereby enabling specific binding to molecular targets such as proteins. To be successful as a novel therapeutic modality, it is important for aptamers to not only bind their targets with high specificity and affinity, but also to exhibit favorable properties with respect to in vivo stability, cost-effective synthesis, and tolerability (i.e., safety). We describe methods for generating aptamers comprising 2 - deoxy purines and 2 -O-methyl pyrimidines (dRmY) that broadly satisfy many of these additional constraints. Conditions under which dRmY transcripts can be efficiently synthesized using mutant T7 RNA polymerases have been identified and used to generate large libraries from which dRmY aptamers to multiple target proteins, including interleukin (IL)-23 and thrombin, have been successfully discovered using the SELEX process. dRmY aptamers are shown to be highly nuclease-resistant, long-lived in vivo, efficiently synthesized, and capable of binding protein targets in a manner that inhibits their biologic activity with K(D) values in the low nM range. We believe that dRmY aptamers have considerable potential as a new class of therapeutic aptamers.

Aptamers (protein binding oligonucleotides) have potential as a new class of targeted therapeutics. For applications requiring chronic systemic administration, aptamers must achieve high-affinity target binding while simultaneously retaining high in vivo stability, tolerability, and ease of chemical synthesis. To this end, we describe a method for generating aptamers composed entirely of 2'-O-methyl nucleotides (mRmY). We present conditions under which 2'-O-methyl transcripts can be generated directly and use these conditions to select a fully 2'-O-methyl aptamer from a library of 3 x 10(15) unique 2'-O-methyl transcripts. This aptamer, ARC245, is 23 nucleotides in length, binds to vascular endothelial growth factor (VEGF) with a Kd of 2 nM, and inhibits VEGF activity in cellular assays. Notably, ARC245 is so stable that degradation cannot be detected after 96 hr in plasma at 37 degrees C or after autoclaving at 125 degrees C. We believe ARC245 has considerable potential as an antiangiogenesis therapeutic.