Degradation-controlled synchronization of HIF-2α and MEK inhibition using self-sealed porous silicon nanoparticles to reprogram tumor immunogenicity

Biomaterial-mediated control of drug release kinetics enables modulation of intracellular signaling dynamics beyond simple payload delivery. Here, we build on a biodegradable, magnesium silicate self-sealed porous silicon nanoparticle (PSiNP) platform to achieve temporally coordinated dual inhibition of hypoxia-inducible factor-2α (HIF-2α) and mitogen-activated protein kinase (MEK) defined as overlapping, prolonged intracellular exposure of both agents through co-administration of two independently loaded PSiNP populations, rather than identical release rates from a single shared carrier. Combination therapies targeting these pathways are often limited by asynchronous drug decay and adaptive signaling recovery. In contrast, degradation-governed release from PSiNPs sustained the availability of belzutifan and trametinib in aqueous physiological medium for >10 days supporting prolonged intracellular drug exposure when combined with the established cellular internalization of this carrier system. The sustained-release behavior of the PSiNP platform is expected to prolong the biological activity of belzutifan and trametinib relative to free-drug administration, thereby supporting sustained functional inhibition of HIF-2α- and MAPK/ERK-associated pathways. In MCPyV-negative Merkel cell carcinoma models, synchronized dual inhibition enhanced cytotoxicity relative to free drug combinations and was accompanied by immunogenic remodeling, including increased calreticulin exposure and reduced PD-L1 expression. Independent release kinetics of each payload were preserved during co-delivery, supporting the robustness of the dual system. These findings identify degradation-controlled temporal coordination of pathway inhibition as a critical determinant of tumor cell fate and establish release synchronization as a key design parameter for biomaterial-enabled combination therapies. STATEMENT OF SIGNIFICANCE: Combination therapies using small-molecule inhibitors are often limited by rapid drug degradation and asynchronous intracellular target suppression, reducing the durability of therapeutic responses. In this study, we developed a biodegradable self-sealed porous silicon nanoparticle platform that enables degradation-controlled temporal synchronization of HIF-2α and MEK inhibition through sustained intracellular drug availability. By independently loading belzutifan and trametinib into separate porous silicon nanoparticle populations, the system preserves drug-specific release behavior while maintaining overlapping multi-day pathway suppression. Sustained dual inhibition enhanced cytotoxicity and promoted immunogenic remodeling in MCPyV-negative Merkel cell carcinoma models, including increased calreticulin exposure and reduced PD-L1 expression. These findings identify release synchronization as a critical biomaterial design parameter for combination cancer therapy.