Targeting Endolysosomal Two-Pore Channel 2 (TPC2) as a Host-Directed Antiviral Strategy Against RNA and DNA Viruses of Global Health Concern

The rapid emergence and re-emergence of viral pathogens continues to challenge global health systems and underscores the limitations of conventional direct-acting antivirals (DAAs), which are typically virus-specific and vulnerable to resistance driven by rapid mutation. In response, host-directed antiviral therapies (HDTs) have emerged as a promising strategy. By targeting conserved host cellular pathways required for numerous viral life-cycles, they offer the potential to inhibit diverse viruses. Several viruses listed as priority pathogens by the World Health Organization exploit host endolysosomal trafficking pathways and autophagic processes to facilitate entry, intracellular transport, and replication. Within this system, two-pore channels (TPCs) are important regulators of calcium-dependent trafficking events. TPC2 represents a particularly compelling host target for antiviral intervention due to its localization within late endosomes and lysosomes, critical sites for viral fusion and genome release. Inhibition of TPC2 has been shown to disrupt endolysosomal acidification, trafficking events, and autophagy-related pathways required by multiple RNA and DNA viruses. However, the specific stages of the viral life cycle affected by TPC2 disruption remain incompletely defined, limiting its translational potential and the rational design of combination therapies. Several small molecules have been identified that inhibit TPC2 activity, including the natural alkaloid Tetrandrine, which has previously been investigated in cancer biology for its anti-proliferative and pro-apoptotic properties. However, Tetrandrine exhibits limited selectivity and suboptimal potency, with relatively high inhibitory concentrations and a modest selectivity index, indicating potential off-target effects and toxicity. These limitations highlight a critical need to develop more selective and potent TPC2 inhibitors to fully realize the therapeutic potential of this pathway. We therefore hypothesize that targeting of TPC2 represents a viable host-directed antiviral strategy capable of broadly inhibiting viruses that depend on endolysosomal trafficking pathways. Two research questions guide this investigation: (1) Does targeting endolysosomal TPC2 represent a viable host-directed strategy for broad-spectrum inhibition of WHO priority viruses? and (2) Can pharmacological modulation of TPC2 using existing small-molecule inhibitors serve as a viable antiviral approach across diverse viral systems? Addressing these questions will validate TPC2 as a conserved host factor and clarify its role in viral infection. Importantly, this work establishes a foundation for the development of next-generation TPC2 inhibitors with improved selectivity and potency. In the longer term, such compounds may be used in combination with existing DAAs to enhance antiviral efficacy, reduce toxicity, and limit resistance. Overall, this research advances the growing field of host-directed antiviral strategies by identifying and refining a therapeutically actionable host pathway with broad-spectrum potential.