Incorporating Synthetic Accessibility in Drug Design: Predicting Reaction Yields of Suzuki Cross-Couplings by Leveraging AbbVie's 15-Year Parallel Library Data Set.

Despite the increased use of computational tools to supplement medicinal chemists' expertise and intuition in drug design, predicting synthetic yields in medicinal chemistry endeavors remains an unsolved challenge. Existing design workflows could profoundly benefit from reaction yield prediction, as precious material waste could be reduced, and a greater number of relevant compounds could be delivered to advance the design, make, test, analyze (DMTA) cycle. In this work, we detail the evaluation of AbbVie's medicinal chemistry library data set to build machine learning models for the prediction of Suzuki coupling reaction yields. The combination of density functional theory (DFT)-derived features and Morgan fingerprints was identified to perform better than one-hot encoded baseline modeling, furnishing encouraging results. Overall, we observe modest generalization to unseen reactant structures within the 15-year retrospective library data set. Additionally, we compare predictions made by the model to those made by expert medicinal chemists, finding that the model can often predict both reaction success and reaction yields with greater accuracy. Finally, we demonstrate the application of this approach to suggest structurally and electronically similar building blocks to replace those predicted or observed to be unsuccessful prior to or after synthesis, respectively. The yield prediction model was used to select similar monomers predicted to have higher yields, resulting in greater synthesis efficiency of relevant drug-like molecules.

The Chosen Few: Parallel Library Reaction Methodologies for Drug Discovery.

Parallel library synthesis is an important tool for drug discovery because it enables the synthesis of closely related analogues in parallel via robust and general synthetic transformations. In this perspective, we analyzed the synthetic methodologies used in >5000 parallel libraries representing 15 prevalent synthetic transformations. The library data set contains complex substrates and diverse arrays of building blocks used over the last 14 years at AbbVie. The library synthetic methodologies that have demonstrated robustness and generality with proven success are described along with their substrate scopes. The evolution of the synthetic methodologies for library synthesis over the past decade is discussed. We also highlight that the combination of parallel library synthesis with high-throughput experimentation will continue to facilitate the discovery of library-amenable synthetic methodologies in drug discovery.

Rearrangement of 3-Hydroxyazetidines into 2-Oxazolines.

A novel rearrangement sequence of 3-hydroxyazetidines via a Ritter initiated cascade provides highly substituted 2-oxazolines in high yields. The reaction conditions and substrate scope of the transformation have been studied demonstrating the generality of the process. The derived products can also be functionalized in order to undergo further intramolecular cyclization leading to a new class of macrocycle. The final cyclization step was shown to be a transformation amenable to continuous flow processing allowing for a dramatic reduction in the reaction time and simple scale-up.

High-Throughput Reaction Screening with Nanomoles of Solid Reagents Coated on Glass Beads.

Technologies that enable rapid screening of diverse reaction conditions are of critical importance to methodology development and reaction optimization, especially when molecules of high complexity and scarcity are involved. The lack of a general solid dispensing method for chemical reagents on micro- and nanomole scale prevents the full utilization of reaction screening technologies. We herein report the development of a technology in which glass beads coated with solid chemical reagents (ChemBeads) enable the delivery of nanomole quantities of solid chemical reagents efficiently. By exploring the concept of preferred screening sets, the flexibility and generality of this technology for high-throughput reaction screening was validated.

Suzuki-Miyaura cross-coupling of unprotected ortho-bromoanilines with benzyl, alkyl, aryl, alkenyl and heteroaromatic boronic esters.

A Suzuki-Miyaura cross-coupling reaction was developed on unprotected ortho-bromoanilines. This operationally simple reaction was developed for the diversification of glucocorticoid receptor modulators (GRMs), showed compatibility to various boronic esters featuring unique functionalities, and was demonstrated on a gram scale.

Di(2-picolyl)amines as Modular and Robust Ligands for Nickel-Catalyzed C(sp2)-C(sp3) Cross-Electrophile Coupling.

Ni-catalyzed aryl-alkyl coupling reactions are reliant on using a limited set of commercially available bidentate nitrogenous ligands to enable the reaction, because noncommercial analogues usually entail challenging syntheses. In this work, di(2-picolyl)amines (DPAs) are explored as an alternative modular ligand class for the nickel-catalyzed aryl-alkyl cross-electrophile coupling. Novel DPA ligands were synthesized directly from inexpensive amine and pyridine building blocks in a single step. This facile synthetic route enabled the parallel synthesis of DPA ligands with varied steric and electronic properties. From this collection of ligands, a few robust ligands for C(sp2)-C(sp3) cross-electrophile coupling were identified and tested in the cross-coupling of a range of diverse molecules, including model examples for late-stage functionalization.

Development of Orally Efficacious Allosteric Inhibitors of TNFα via Fragment-Based Drug Design.

Tumor necrosis factor α (TNFα) is a soluble cytokine that is directly involved in systemic inflammation through the regulation of the intracellular NF-κB and MAPK signaling pathways. The development of biologic drugs that inhibit TNFα has led to improved clinical outcomes for patients with rheumatoid arthritis and other chronic autoimmune diseases; however, TNFα has proven to be difficult to drug with small molecules. Herein, we present a two-phase, fragment-based drug discovery (FBDD) effort in which we first identified isoquinoline fragments that disrupt TNFα ligand-receptor binding through an allosteric desymmetrization mechanism as observed in high-resolution crystal structures. The second phase of discovery focused on the de novo design and optimization of fragments with improved binding efficiency and drug-like properties. The 3-indolinone-based lead presented here displays oral, in vivo efficacy in a mouse glucose-6-phosphate isomerase (GPI)-induced paw swelling model comparable to that seen with a TNFα antibody.

Expanding the Medicinal Chemist Toolbox: Comparing Seven C(sp2)-C(sp3) Cross-Coupling Methods by Library Synthesis.

Despite recent advances in the field of C(sp2)-C(sp3) cross-couplings and the accompanying increase in publications, it can be hard to determine which method is appropriate for a given reaction when using the highly functionalized intermediates prevalent in medicinal chemistry. Thus a study was done comparing the ability of seven methods to directly install a diverse set of alkyl groups on "drug-like" aryl structures via parallel library synthesis. Each method showed substrates that it excelled at coupling compared with the other methods. When analyzing the reactions run across all of the methods, a reaction success rate of 50% was achieved. Whereas this is promising, there are still gaps in the scope of direct C(sp2)-C(sp3) coupling methods, like tertiary group installation. The results reported herein should be used to inform future syntheses, assess reaction scope, and encourage medicinal chemists to expand their synthetic toolbox.

Emerging Trends in Flow Chemistry and Applications to the Pharmaceutical Industry.

The field of flow chemistry has garnered considerable attention over the past 2 decades. This Perspective highlights many recent advances in the field of flow chemistry and discusses applications to the pharmaceutical industry, from discovery to manufacturing. From a synthetic perspective, a number of new enabling technologies are providing more rationale to run reactions in flow over batch techniques. Additionally, highly automated flow synthesis platforms have been developed with broad applicability across the pharmaceutical industry, ranging from advancing medicinal chemistry programs to self-optimizing synthetic routes. A combination of simplified and automated systems is discussed, demonstrating how flow chemistry solutions can be tailored to fit the specific needs of a project.

High-Temperature Boc Deprotection in Flow and Its Application in Multistep Reaction Sequences.

A simplified Boc deprotection using a high-temperature flow reactor is described. The system afforded the qualitative yield of a wide variety of deprotected substrates within minutes using acetonitrile as the solvent and without the use of acidic conditions or additional workups. Highly efficient, multistep reaction sequences in flow are also demonstrated wherein no extraction or isolation was required between steps.

Tissue-Factor Targeted Peptide Amphiphile Nanofibers as an Injectable Therapy To Control Hemorrhage.

Noncompressible torso hemorrhage is a leading cause of mortality in civilian and battlefield trauma. We sought to develop an i.v.-injectable, tissue factor (TF)-targeted nanotherapy to stop hemorrhage. Tissue factor was chosen as a target because it is only exposed to the intravascular space upon vessel disruption. Peptide amphiphile (PA) monomers that self-assemble into nanofibers were chosen as the delivery vehicle. Three TF-binding sequences were identified (EGR, RLM, and RTL), covalently incorporated into the PA backbone, and shown to self-assemble into nanofibers by cryo-transmission electron microscopy. Both the RLM and RTL peptides bound recombinant TF in vitro. All three TF-targeted nanofibers bound to the site of punch biopsy-induced liver hemorrhage in vivo, but only RTL nanofibers reduced blood loss versus sham (53% reduction, p < 0.05). Increasing the targeting ligand density of RTL nanofibers yielded qualitatively better binding to the site of injury and greater reductions in blood loss in vivo (p < 0.05). In fact, 100% RTL nanofiber reduced overall blood loss by 60% versus sham (p < 0.05). Evaluation of the biocompatibility of the RTL nanofiber revealed that it did not induce RBC hemolysis, did not induce neutrophil or macrophage inflammation at the site of liver injury, and 70% remained intact in plasma after 30 min. In summary, these studies demonstrate successful binding of peptides to TF in vitro and successful homing of a TF-targeted PA nanofiber to the site of hemorrhage with an associated decrease in blood loss in vivo. Thus, this therapeutic may potentially treat noncompressible hemorrhage.