No classical molecular target

The phrase "No classical molecular target" refers to situations in pharmacology and drug development where the molecular entity responsible for a drug’s action is not a recognized biomolecule such as a protein, enzyme, receptor, ion channel, or transporter. It is often a placeholder or category in databases to denote that either no molecular target has been identified for a drug, or the drug’s effects arise through mechanisms not attributable to canonical targets. Approximately 7% of approved drugs are reported to have no known primary target, and up to 18% lack a well-defined mechanism of action. However, advances in chemoinformatics and molecular biology have shown that most drugs likely do act via definable molecular partners, making the list of drugs with genuinely "no classical molecular target" quite small, and usually indicating incomplete knowledge rather than a true absence of molecular targeting. This entry should be handled as a flag for missing, uncertain, or insufficiently characterized information, not as a molecular entity itself.

Other names

unknown targetmechanism not well definednon-classical targetnon-specific action

Other (mechanism of action not via well-defined molecular recognition; examples include drugs with poorly understood actions, broad cytotoxic agents, or those acting through physical interactions rather than ligand-receptor binding)