RESUMO
Current therapies for chronic pain can have insufficient efficacy and lead to side effects, necessitating research of novel targets against pain. Although originally identified as an oncogene, Tropomyosin-related kinase A (TrkA) is linked to pain and elevated levels of NGF (the ligand for TrkA) are associated with chronic pain. Antibodies that block TrkA interaction with its ligand, NGF, are in clinical trials for pain relief. Here, we describe the identification of TrkA-specific inhibitors and the structural basis for their selectivity over other Trk family kinases. The X-ray structures reveal a binding site outside the kinase active site that uses residues from the kinase domain and the juxtamembrane region. Three modes of binding with the juxtamembrane region are characterized through a series of ligand-bound complexes. The structures indicate a critical pharmacophore on the compounds that leads to the distinct binding modes. The mode of interaction can allow TrkA selectivity over TrkB and TrkC or promiscuous, pan-Trk inhibition. This finding highlights the difficulty in characterizing the structure-activity relationship of a chemical series in the absence of structural information because of substantial differences in the interacting residues. These structures illustrate the flexibility of binding to sequences outside of-but adjacent to-the kinase domain of TrkA. This knowledge allows development of compounds with specificity for TrkA or the family of Trk proteins.
Assuntos
Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Receptor trkA/antagonistas & inibidores , Receptor trkA/química , Sequência de Aminoácidos , Sítios de Ligação , Cristalografia por Raios X , Avaliação Pré-Clínica de Medicamentos , Humanos , Cinética , Glicoproteínas de Membrana/antagonistas & inibidores , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Modelos Moleculares , Conformação Proteica , Inibidores de Proteínas Quinases/síntese química , Receptor trkA/genética , Receptor trkB/antagonistas & inibidores , Receptor trkB/química , Receptor trkB/genética , Receptor trkC/antagonistas & inibidores , Receptor trkC/química , Receptor trkC/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/efeitos dos fármacos , Proteínas Recombinantes/genética , Relação Estrutura-Atividade , Ressonância de Plasmônio de SuperfícieRESUMO
Fragment-based approaches have added to the arsenal of tools used to identify novel developable leads for drug discovery with high ligand efficiencies. A variety of label-free technologies have been developed and used throughout the industry for fragment screening. Using surface plasmon resonance (SPR) as a fragment screening platform is a relatively new approach. The miniaturization and automation of this technology has led to an associated problem: the large volume of raw data often makes it challenging to analyze and integrate the results of SPR data into the workflow of project teams engaged in the discovery process in a timely fashion. As such, several sets of equations were derived and implemented on Merck's intranet to score single sensorgrams to distinguish stable binders from weak or anomalous binders. This set of equations was optimized and validated on simulated data to both capture "fragment-like" behavior from SPR experiments and filter out much of the anomalous behavior commonly observed. It has subsequently been applied successfully to several in-house discovery programs.