Compelling target biology is often treated as the beginning of a translational trajectory, yet mechanistic plausibility does not establish that a therapeutic perturbation reaches the relevant tissue, engages its target under biologically realistic conditions, produces an interpretable pharmacodynamic response, or acts in patients whose disease state remains dependent on that mechanism. This Translational Perspective argues that these evidence layers should be treated as distinct but connected tests rather than interchangeable indicators of progress. Target engagement without adequate site-of-action exposure may be pharmacologically uninformative; a responsive biomarker may lack decision utility if its context of use is undefined; and biomarker-guided selection may fail when disease biology, treatment history, or patient heterogeneity alters the mechanism–response relationship. We therefore develop a proposed mechanism-to-medicine architecture in which translational confidence depends on conditional convergence across target validity, engagement, tissue exposure, pharmacodynamic evidence, biomarker qualification, and clinical context. Discordance is treated as diagnostic information that should trigger reassessment rather than be averaged away. The framework is explicitly non-numeric and does not claim prospective validation. Its purpose is to clarify what has actually been tested, what remains inferential, and when apparently promising programmes require additional evidence rather than stronger mechanistic storytelling.
IJPRAS
