Transport substrates and modulators of the human multidrug resistance (MDR1) P-glycoprotein (Pgp) are generally lipophilic cationic compounds, many with substituted aryl moieties. We sought to synthesize aromatic technetium-isonitrile complexes to enable functional detection in vivo of Pgp expression in tissues. A series of substituted aromatic isonitrile analogs were synthesized from their corresponding amines by reaction with dichlorocarbene under phase transfer-catalyzed conditions, and the non-carrier-added hexakis(areneisonitrile)Tc-99m(I) complexes were produced by reaction with pertechnetate in the presence of sodium dithionite. Cellular accumulation in vitro, whole body biodistribution, and the imaging properties of these lipophilic, monocationic organometallic complexes were determined in Chinese hamster lung fibroblasts expressing MDR Pgp, in normal rats, and in rabbits, respectively. For this initial series, verapamil (50 microM), the classical Pgp modulator, significantly enhanced cellular accumulation or displaced binding of Tc complexes of 1b, 1d, 1h, 2a, 2d, 3a, and 3b, indicative of targeted interactions with Pgp. Most complexes, despite their modestly high lipophilicity, were excluded by the blood/brain barrier, and several complexes displayed simultaneously high hepatobiliary and renal excretion in vivo, consistent with the physiological expression pattern of Pgp in these tissues. Selected Tc- and Re-areneisonitrile complexes of this class have potential applicability to the functional imaging and modulation, respectively, of MDR Pgp in human tissues.

Ulotaront (SEP-363856) is a trace-amine associated receptor 1 (TAAR1) agonist with 5-HT1A receptor agonist activity in Phase 3 clinical development, with FDA Breakthrough Therapy Designation, for the treatment of schizophrenia. TAAR1 is a G-protein-coupled receptor (GPCR) that is expressed in cortical, limbic, and midbrain monoaminergic regions. It is activated by endogenous trace amines, and is believed to play an important role in modulating dopaminergic, serotonergic, and glutamatergic circuitry. TAAR1 agonism data are reported herein for ulotaront and its analogues in comparison to endogenous TAAR1 agonists. In addition, a human TAAR1 homology model was built around ulotaront to identify key interactions and attempt to better understand the scaffold-specific TAAR1 agonism structure–activity relationships.

Target selection is a critical step in the majority of modern drug discovery programs. The viability of a drug target depends on two components: biological relevance and chemical tractability. The concept of druggability was introduced to describe the second component, and it is defined as the ability of a target to bind a drug-like molecule with a therapeutically useful level of affinity. To investigate the rules that govern druggability, we developed an algorithm to isolate and characterize the binding pockets of protein targets. Using this algorithm, we performed a comparative analysis between the relevant pockets of 60 targets of approved drugs and a diverse set of 440 ligand-binding pockets. As a result, we defined a preferred property space for druggable pockets based on five key properties (volume, depth, enclosure, percentage of charged residues and hydrophobicity), and we represented it with a set of simple rules. These rules may be applicable in the future to evaluate the chemical tractability of prospective targets.

Conditions for the synthesis of synthetic peptide combinatorial libraries (SPCLs) from mixtures of amino acids were explored. In a one-pot synthesis, the effect of the starting concentrations of amino acids on the resulting library composition was studied, and the optimum balance of amino acids was determined. Protein sequencing, MALDI-TOF, and amino acid analysis were used for the evaluation of the libraries, and their relative merits-are discussed. The effects of continuous-flow automated synthesis instrumentation in conjunction with polyethylene glycol-polystyrene (PEG-PS) graft supports and various cleavage cocktails on the successful synthesis of SPCLs were examined.