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Profacgen's LYTAC development services deliver lysosome-targeting chimeras for selective degradation of extracellular and membrane-associated proteins, expanding the druggable target space beyond intracellular substrates accessible to conventional PROTACs.
While PROTACs and related modalities effectively eliminate intracellular proteins, they cannot address secreted cytokines, growth factors, or membrane receptors that drive disease pathology. The lysosome-targeting chimera (LYTAC) platform bridges this gap by hijacking the endogenous endosomal-lysosomal pathway: bispecific conjugates recruit cell-surface lysosome-shuttling receptors to internalize and degrade extracellular targets.
Profacgen provides comprehensive LYTAC development, from glycopolypeptide ligand design and antibody selection to conjugation chemistry and functional validation. Our platform supports CI-M6PR and ASGPR-based systems, enabling targeted clearance of membrane receptors, immune checkpoints, and secreted proteins for oncology, immunology, and neurodegenerative research.
What Is LYTAC?
Lysosome-targeting chimeras (LYTACs) are bispecific conjugates that redirect extracellular and membrane-associated proteins to the lysosome for degradation. The platform encompasses three core elements:
Lysosome-targeting chimeras: LYTACs are heterobifunctional molecules comprising a target-binding moiety (antibody or small molecule) conjugated to a glycopolypeptide ligand for a cell-surface lysosome-shuttling receptor. Unlike PROTACs, which exploit the intracellular ubiquitin-proteasome system, LYTACs harness the endosomal-lysosomal pathway for protein clearance
Extracellular proteins: LYTACs target secreted proteins—cytokines, growth factors, and signaling ligands—that are inaccessible to intracellular degradation modalities. By binding the extracellular domain and engaging lysosomal receptors, LYTACs induce receptor-mediated endocytosis and subsequent lysosomal proteolysis
Membrane proteins: LYTACs enable degradation of transmembrane receptors, immune checkpoints, and adhesion proteins without requiring cell-permeable ligands or genetic manipulation. The extracellular binding orientation circumvents the need for intracellular target engagement
Mechanism of LYTAC-Mediated Degradation
LYTAC-mediated degradation proceeds through a sequential endosomal-lysosomal pathway:
Target Protein Engagement
The antibody or small-molecule warhead of the LYTAC binds to the extracellular domain of a membrane protein or to a secreted protein in the extracellular milieu, conferring target specificity.
LYTAC Binding
The glycopolypeptide ligand moiety—typically mannose-6-phosphate (M6P) or M6Pn multimers—simultaneously engages a cell-surface lysosome-targeting receptor (LTR), such as the cation-independent mannose-6-phosphate receptor (CI-M6PR) or asialoglycoprotein receptor (ASGPR).
Lysosomal Receptor Recruitment and Endocytosis
Receptor engagement triggers clathrin-mediated endocytosis. The LYTAC-target-receptor complex is engulfed by the plasma membrane, forming a transport vesicle that traffics through the endosomal compartment toward the lysosome.
Lysosomal Degradation
Within the acidic lysosomal environment, the receptor releases its cargo, and the target protein is subjected to proteolytic degradation by lysosomal hydrolases. The receptor recycles to the cell surface for subsequent rounds of target internalization.
Figure 1. The concept of LYTACs. (A) A glycopolypeptide ligand for CI-M6PR is conjugated to an antibody to traffic secreted and membrane-associated proteins to lysosomes. (B) Synthesis of M6Pn glycopolypeptide ligands for CI-M6PR. (C) Assay for the internalization of cargo by biotin-based LYTACs. (Banik et al., 2020)
Our LYTAC Development Services
Profacgen offers end-to-end LYTAC development tailored to your target protein and therapeutic objectives:
Ligand Design
Rational design of glycopolypeptide ligands optimized for lysosomal receptor affinity and endosomal trafficking.
M6P and M6Pn multimer synthesis with controlled valency and spacing for enhanced CI-M6PR avidity
GalNAc ligand design for ASGPR-targeted LYTACs in hepatocyte applications
Linker optimization: PEG, alkyl, or cleavable linkers to balance plasma stability and lysosomal release
Receptor Selection
Strategic matching of lysosomal receptors to target tissue and cellular context.
CI-M6PR profiling: ubiquitous expression assessment and receptor density quantification in target cell types
ASGPR selection: liver-specific targeting for secreted protein clearance and hepatocyte membrane protein degradation
Receptor recycling kinetics and endosomal routing analysis to maximize degradation efficiency
Conjugation Strategies
Chemical and enzymatic conjugation of target-binding warheads to glycopolypeptide ligands.
Antibody-glycan conjugation: site-specific modification via cysteine engineering, glycoengineering, or enzymatic transfer
LYTAC technology enables therapeutic and research applications previously inaccessible to intracellular degradation modalities:
Membrane Protein Degradation: Targeted elimination of receptor tyrosine kinases (EGFR), immune checkpoints (PD-L1), and G-protein-coupled receptors. LYTACs have demonstrated effective EGFR degradation via CI-M6PR engagement and PD-L1 clearance using anti-PD-L1 antibodies conjugated to M6Pn ligands
Secreted Protein Clearance: Removal of pathogenic cytokines, growth factors, and signaling ligands from the extracellular space. ASGPR-based LYTACs enable liver-specific clearance of circulating proteins, offering a therapeutic avenue for inflammatory and metabolic disorders
Oncology Research: Degradation of oncogenic membrane receptors and tumor microenvironment factors. LYTAC-mediated elimination of EGFR and PD-L1 has shown promise in preclinical models, offering orthogonal strategies to antibody-mediated inhibition or blockade
Advantages of LYTAC
Extracellular Target Access: Degrades membrane and secreted proteins that are inaccessible to intracellular PROTACs, including cytokines, growth factors, and cell-surface receptors.
Universal Ligand Platform: M6P and M6Pn glycopolypeptide ligands are target-agnostic; only the antibody or small-molecule warhead requires customization for each new target.
Receptor-Mediated Specificity: Endogenous lysosomal receptor trafficking ensures selective delivery to the degradative compartment, minimizing off-target effects on intracellular proteins.
Catalytic Mechanism: Lysosomal receptors recycle after cargo release, enabling substoichiometric LYTAC concentrations to achieve sustained target degradation.
Tissue-Specific Targeting: ASGPR-restricted LYTACs enable liver-selective degradation, while CI-M6PR-based systems offer broad tissue applicability.
Why Choose Profacgen
Dual-Receptor Expertise: Profacgen develops both CI-M6PR and ASGPR-based LYTAC systems, enabling selection of the optimal receptor based on target localization and tissue specificity requirements.
Integrated Chemistry Platform: In-house glycopolypeptide synthesis, antibody engineering, and conjugation chemistry support rapid LYTAC prototype generation and optimization.
Comprehensive Validation: End-to-end functional assessment including internalization kinetics, lysosomal colocalization, degradation efficiency, and off-target profiling ensures robust data packages.
Target Class Breadth: Proven experience across receptor tyrosine kinases, immune checkpoints, secreted cytokines, and adhesion proteins.
Regulatory Support: Structured documentation and analytical packages suitable for IND-enabling studies and intellectual property filings.
Scenario 1: EGFR Membrane Receptor Degradation by CI-M6PR LYTAC
Program Context:
An oncology program required elimination of EGFR to overcome resistance to tyrosine kinase inhibitors. Genetic knockdown was insufficient for rapid phenotype assessment, and conventional PROTACs could not access the extracellular domain.
Objective:
To design a CI-M6PR-targeting LYTAC using an anti-EGFR antibody conjugated to M6Pn glycopolypeptide, demonstrate receptor-mediated internalization and lysosomal degradation, and assess phenotypic consequences in EGFR-driven cancer cell lines.
Approach:
Profacgen synthesized an M6P3 glycopolypeptide ligand and conjugated it to a clinically validated anti-EGFR antibody via site-specific cysteine engineering. The conjugate was validated for CI-M6PR binding by surface plasmon resonance and for EGFR engagement by flow cytometry. Internalization was confirmed by confocal microscopy showing colocalization with LysoTracker Red within 4 hours. Degradation efficiency was quantified by Western blot and flow cytometry.
Outcome:
The LYTAC achieved >80% EGFR degradation at 100 nM with DC50 of 35 nM. Degradation was blocked by chloroquine (lysosomal inhibitor) and by excess free M6P (receptor competition), confirming pathway specificity. Cell proliferation and downstream signaling (p-ERK, p-AKT) were significantly suppressed. The data supported progression to in vivo efficacy studies.
Scenario 2: PD-L1 Immune Checkpoint Clearance for Immunotherapy Enhancement
Program Context:
A cancer immunotherapy program sought to enhance T-cell activation by eliminating PD-L1 from tumor cells and antigen-presenting cells. Antibody blockade provided transient inhibition; degradation was hypothesized to achieve more durable immune activation.
Objective:
To develop a PD-L1-targeting LYTAC using an anti-PD-L1 antibody (atezolizumab variant) conjugated to M6Pn, validate lysosomal degradation in tumor cell lines and patient-derived xenograft models, and assess immune cell activation markers.
Approach:
Profacgen conjugated an atezolizumab-derived Fab fragment to a tetrameric M6P ligand via enzymatic glycoengineering. The LYTAC was validated for PD-L1 binding and CI-M6PR engagement by ELISA and SPR. Degradation was assessed in PD-L1-high cell lines by Western blot and flow cytometry. T-cell activation was measured by IFN-γ release and CD25 upregulation in co-culture assays.
Outcome:
The LYTAC induced >75% PD-L1 degradation within 8 hours, with sustained suppression over 48 hours. T-cell activation markers increased 3-fold compared to isotype control and 2-fold compared to antibody blockade alone. The study demonstrated that LYTAC-mediated PD-L1 degradation offers superior immune activation compared to transient receptor blockade.
Q: What is the difference between LYTAC and PROTAC?
A: PROTACs recruit intracellular E3 ubiquitin ligases to induce proteasomal degradation of cytosolic and nuclear proteins. LYTACs recruit cell-surface lysosomal receptors to redirect extracellular and membrane-associated proteins to the lysosome. PROTACs require cell-permeable ligands and target intracellular domains; LYTACs bind extracellular domains and are uniquely suited for membrane receptors, secreted proteins, and cytokines.
Q: Which lysosomal receptors does LYTAC utilize?
A: The primary receptors are the cation-independent mannose-6-phosphate receptor (CI-M6PR) and the asialoglycoprotein receptor (ASGPR). CI-M6PR is ubiquitously expressed and mediates broad tissue targeting. ASGPR is liver-specific and enables hepatocyte-selective degradation. Both receptors cycle between the plasma membrane and endosomal compartments, facilitating repeated rounds of target internalization.
Q: What types of proteins can LYTAC degrade?
A: LYTACs can degrade membrane proteins (receptor tyrosine kinases, immune checkpoints, GPCRs), secreted proteins (cytokines, growth factors, antibodies), and extracellular matrix components. They are particularly effective for targets with accessible extracellular domains. Intracellular proteins are not accessible to LYTACs unless they traffic to the cell surface or are secreted.
Q: How does LYTAC compare to antibody-mediated inhibition?
A: Antibody blockade transiently inhibits protein function by occupying binding sites or preventing receptor-ligand interactions. LYTAC eliminates the protein entirely, removing both catalytic and scaffolding functions. Degradation can overcome receptor shedding, compensatory upregulation, and incomplete pathway suppression. However, LYTAC development is more complex than antibody production, requiring conjugation chemistry and receptor optimization.
Q: What sample requirements are needed for LYTAC development?
A: For ligand design, no biological sample is required. For conjugation, the target-binding antibody or small molecule must be provided or synthesized. For functional validation, target-expressing cell lines are needed. Profacgen can assist with antibody sourcing, cell line generation, and target expression profiling. Degradation assessment requires cell culture facilities and access to lysosomal inhibitors for pathway confirmation.
Q: Can LYTAC be used for in vivo applications?
A: Yes, with appropriate pharmacokinetic optimization. LYTACs face challenges including plasma stability, immunogenicity, and rapid clearance. Profacgen addresses these through PEGylation, Fc fusion strategies, and glycan engineering. ASGPR-based LYTACs offer liver-specific targeting with reduced systemic exposure. In vivo validation requires receptor expression profiling in target tissues and pharmacodynamic biomarker assessment.
Figure 1. The concept of LYTACs. (A) A glycopolypeptide ligand for CI-M6PR is conjugated to an antibody to traffic secreted and membrane-associated proteins to lysosomes. (B) Synthesis of M6Pn glycopolypeptide ligands for CI-M6PR. (C) Assay for the internalization of cargo by biotin-based LYTACs. (Banik et al., 2020)