Cell-Penetrating Polypeptide Sequences for Selective Macromolecule Delivery

The patent applies local quality by incorporating a cell-penetrating peptide domain (CPP) as a specific functional module within a larger chimeric protein structure. The CPP domain (such as TAT, penetratin, or dKALA sequences) is fused to therapeutic domains and targeting domains, allowing the CPP to specifically mediate cellular uptake while other domains provide tissue-specific targeting and therapeutic function. This modular approach enables the CPP to perform its membrane-penetration function locally without causing systemic toxicity, as the therapeutic effect is localized to cells that express the specific surface markers recognized by the targeting domain.

The patent uses chimeric proteins as intermediaries that combine multiple functional domains: a CPP domain for cellular penetration, a targeting domain for tissue-specific recognition, and a therapeutic domain for the actual therapeutic effect. This intermediary structure allows the therapeutic agent to be delivered specifically to target cells through a multi-step process: the targeting domain binds to cell surface markers on target cells, the CPP domain facilitates membrane penetration, and the therapeutic domain exerts the therapeutic effect intracellularly. This intermediary approach resolves the contradiction by ensuring that CPP-mediated transport occurs only at sites where the targeting domain has bound, thereby eliminating off-target effects.

The patent employs composite materials by constructing chimeric proteins that integrate the CPP domain with stabilizing structural elements and protective domains. The chimeric protein structure combines the CPP sequence (which provides membrane penetration capability) with therapeutic domains and often includes stabilizing elements such as signal peptides, linkers, and protective protein structures that enhance resistance to proteolytic degradation. This composite structure maintains the CPP's drug delivery capability while the overall protein architecture and protective domains improve stability during production, storage, and in vivo circulation.

The patent applies beforehand cushioning by incorporating stable protein structures and protective domains into the chimeric protein design that preemptively protect the CPP domain from protease degradation. The chimeric protein structure includes stabilizing elements and protective domains that are designed to shield the CPP sequence from proteolytic enzymes in the production environment and during storage. This prior protection ensures that the CPP remains intact and functional throughout the drug manufacturing process and storage period, preventing premature degradation that would compromise drug delivery capability.

The patent applies local quality by using the CPP domain as a localized functional element within a larger chimeric protein that provides spatial and cellular specificity. The CPP domain is responsible for cellular uptake, but its activity is localized to cells that express the specific surface markers recognized by the targeting domain. This localization means that even at low concentrations, the therapeutic effect is concentrated in target cells rather than distributed systemically, thereby maintaining therapeutic efficacy while minimizing general toxicities. The targeting domain ensures that the CPP-therapeutic conjugate only binds to and enters target cells, not healthy cells.

The patent uses the targeting domain as an intermediary that mediates between the CPP domain and the therapeutic domain, providing cell-specific recognition before CPP-mediated internalization occurs. The chimeric protein structure positions the targeting domain to first bind to cell surface markers on target cells, which then facilitates the action of the CPP domain for membrane penetration. This intermediary targeting step ensures that CPP activity is restricted to target cells only, allowing therapeutic effects to be achieved at low concentrations without causing general toxicities in non-target tissues. The targeting domain acts as a gatekeeper that directs CPP-mediated delivery exclusively to the intended cell type.