The characterization of drug-target interactions and elucidation of specific functional-energetic correlations are important prerequisites for the development of efficient therapeutic agents. Our strategy to identify prospective lead compounds has focused on designing and synthesizing linear analogs of aurintricarboxylic acid (ATA). The latter comprises a heterogeneous polymeric mixture of structurally related triphenylmethane derivatives known to exhibit a host of biological properties including antiviral activity. The synthetic analogs are analyzed for their ability to interact with human serum albumin (HSA), yeast ribosomes, and the RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. The resultant data are critical determinants for evaluating drug bioavailability, transport, and effective inhibition of host and viral targets. Promising lead compounds are selected on the basis of their binding energetics, which have been characterized and correlated with functional activities as assessed by inhibition of RNA replication and protein synthesis. Stoichiometric data derived from calorimetric binding isotherms suggest an average molecular weight of ∼2,000 for the predominant ATA species which corresponds to a polymer length of 4–5 monomers. Significantly, our results reveal that ATA activity is mimicked by linear compounds of defined molecular weight with a dichlorohexamer salicylic-acid derivative exhibiting the highest potency. These findings are instrumental for optimizing the design of structurally defined ATA analogs that fulfill the requirements of an antiviral drug with respect to bioavailability, homogeneity, and potency. We are currently exploring the impact of fatty acid occupancy on ATA binding affinity within HSA subdomains to assess the overall degree of cooperativity and crosstalk as manifest in structural and energetic properties of HSA-ligand complexes. These multiparametric investigations are designed to identify novel compounds that expand our existing arsenal of therapeutic regimens given the urgent need for effective antiviral treatment strategies.
Minetti et al. (Sun,) studied this question.