Unknown or multiple putative molecular targets

The classification 'Unknown or multiple putative molecular targets' is a designation used in pharmacological databases such as ChEMBL and DrugBank to categorize therapeutic agents whose specific molecular mechanism of action (MoA) has not been definitively characterized or involves a complex, multi-target profile [1, 2]. This is particularly common for drugs discovered through phenotypic screening, where compounds are selected based on their ability to induce a desired biological effect in a cell or organism rather than their affinity for a pre-selected protein [3]. While these agents can be highly effective, the lack of a singular defined target poses significant hurdles for biotech analysts, including difficulties in lead optimization and the inability to develop target-based safety assays [3, 4]. Furthermore, the absence of a clear MoA makes it challenging to identify predictive biomarkers for patient stratification or to monitor efficacy at the molecular level [3]. In many instances, these drugs exhibit polypharmacology, interacting with a broad network of receptors, enzymes, or ion channels that collectively produce the therapeutic response [1]. As analytical techniques like activity-based protein profiling (ABPP) and functional genomics evolve, many drugs in this category are eventually reclassified under specific canonical targets [3]. Consequently, this entry serves as a placeholder for compounds where the biological complexity exceeds current mechanistic understanding [2, 4].

Other names

Unknown targetUnspecified molecular targetMultiple putative targetsNon-specific mechanismPhenotypic target

The mechanism of action is either unknown, poorly defined, or involves complex polypharmacology across multiple biological pathways [1, 3].