Background: In this study, we report a novel series of proline- and pipecolic acid-based small molecules designed as allosteric inhibitors of the NS2B/NS3 serine proteases from dengue and Zika viruses, key targets in antiviral drug discovery. Results: Enzymatic studies revealed that S-proline derivatives bearing electron-withdrawing substituents on the aromatic ring, particularly that with a trifluoromethyl group in meta position (i.e., compound 3, IC₅₀ = 5.0 µM), were the most potent against DENV NS2B/NS3, while nitro-substituted inhibitors were mostly effective only against the ZIKV protease. R-configured pipecolic acid-based derivatives were the only ones active against DENV NS2B/NS3, even if the mid-micromolar range; however, they demonstrated improved cellular efficacy since inhibitors 24 and 27 exhibiting strong activity in a DENV2 protease reporter gene assay (EC₅₀ = 5.2 and 5.1 µM, respectively). All compounds showed no cytotoxicity (CC₅₀ > 100 µM) and were selective for the viral protease over off-target serine proteases. Structure-based approaches were exploited to map the druggable allosteric site close to Asn152. Conclusions: Our findings led us to identify proline and pipecolic acid-based inhibitors as promising leads for the development of selective flaviviral NS2B/NS3 allosteric inhibitors.

QT interval prolongation is associated with an increased risk of torsades de pointes (TdP), a potentially life-threatening ventricular arrhythmia, making assessment of cardiac repolarization a critical component of drug development. This work demonstrates how integrated in silico methodologies can be used to predict and quantitatively characterize QT liability across the drug discovery and development continuum. A proof-of concept translational workflow combining molecular structure analysis, in vitro pharmacology, animal data, and clinical exposure-response modeling was evaluated using the retrospective case examples verapamil and dofetilide. Molecular structure- and pharmacology-based assessments predicted hERG channel interaction and potential QT risk for both compounds. While initial in silico analyses suggested a high QT liability for verapamil and dofetilide, mechanistic electrophysiological modeling differentiated their effects. For verapamil, concurrent calcium channel inhibition offset hERG-mediated effects, resulting in predicted reductions in action potential duration and no clinically relevant QT prolongation. In contrast, dofetilide produced concentration-dependent increases in action potential duration, consistent with its known proarrhythmic potential. Translation of nonclinical findings to humans accurately predicted the absence of clinically meaningful QT effects for verapamil and identified QT prolongation exceeding the regulatory 10 ms threshold for dofetilide at therapeutic concentrations. Drug exposure and pharmacokinetic properties could be anticipated based solely on molecular structure. This conceptual workflow demonstrates how integrated quantitative in silico approaches can support earlier identification, characterization, and communication of QT risk, enabling informed decision-making and improved development efficiency from bench to bedside.