Extracellular and membrane-targeted protein degradation (emTPD): Mechanisms, design frameworks, and therapeutic opportunities
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PUBLIC SUMMARY
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Extracellular and membrane proteins are key disease targets but remain hard to remove.
This review summarizes emTPD, which routes targets to lysosomes by receptors, E3s, or programs.
We identify endolysosomal routing as key to predictable, tissue-selective, and durable degradation.
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ABSTRACT
Over the past five years, the field of extracellular and membrane-targeted protein degradation (emTPD) has reoriented target proteins toward endolysosomal degradation, providing an alternative to traditional inhibitors. Here, we classify current emTPD strategies according to the primary fate-determining module that commits cargo to degradation: (1) Receptor hijacking, in which endogenous receptors drive uptake and lysosomal routing; (2) Surface E3 ligase recruitment, in which ubiquitin serves as the internalization and sorting signal; (3) Receptor-independent or programmable routing mechanisms, which do not rely on canonical lysosomal shuttle receptors but instead encode degradative fate through alternative endocytic, sorting, or autophagy-linked cues. We synthesize shared mechanistic principles—membrane ternary-complex biophysics, endocytic flux, and condition-triggered dissociation—into a unified design framework that guides molecular engineering, tissue selectivity, and rational combination strategies. Major translational challenges include PK/PD modeling, tissue penetration, immunogenicity and safety window. With the emergence of early clinical evaluations (e.g., BHV-1400 entering early clinical evaluation), emTPD is gradually shifting towards clinical validation. In the future, the combination of artificial intelligence-driven design and pathway engineering will expand its therapeutic applications across tumors, autoimmune diseases, neurodegenerative disorders, and metabolic diseases. -
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REFERENCES
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Zhang K., Qiu F., Lyu A., et al. (2026). Extracellular and membrane-targeted protein degradation (emTPD): Mechanisms, design frameworks, and therapeutic opportunities. The Innovation Drug Discovery 1:100024. https://doi.org/10.59717/j.xinn-drugdisc.2026.100024
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Zhang K., Qiu F., Lyu A., et al. (2026). Extracellular and membrane-targeted protein degradation (emTPD): Mechanisms, design frameworks, and therapeutic opportunities. The Innovation Drug Discovery 1:100024. https://doi.org/10.59717/j.xinn-drugdisc.2026.100024
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Figure 1.
Mechanism classification of emTPD platforms
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Figure 2.
MTC is the central control point that determines emTPD efficiency
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Figure 3.
Receptor-hijacking strategies in emTPD
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Figure 4.
Cell-surface E3 recruitment and programmable/non-canonical routing modalities
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Figure 5.
Rational design framework for emTPD
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Figure 6.
Translational priorities for the future development of emTPD
