Feldan Shuttle Technology

Innovative protein delivery system for regenerative medicine

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FELDAN SHUTTLE: a disruptive platform for delivery of transcription factors and genome editing tools in clinical applications

To be active, genome editing effector complexes and transcription factors need to reach the DNA of cells contained in the nucleus. Recombinant proteins added to the medium do not cross the cell membrane and thus need to be transported from the extracellular medium to the cytoplasm and the cell nucleus. Because no efficient system delivering unmodified proteins is available, scientists must rely on the transfection of DNA or RNA strands and their subsequent translation into proteins by the cellular machinery.

The Feldan Shuttle platform delivers proteins directly inside cells; once delivered these proteins dislodge from the carrier and are free to modulate gene expression, modify cell physiology or induce genetic modifications. The Feldan Shuttle is 100% protein-based and is rapidly degraded in the cell, leaving no toxic residues. It is capable of delivering proteins in multiple cell types without altering cell viability. The Shuttle is a virus-free, DNA- and RNA-free technology, thereby eliminating potential mutagenic risks. With such important advantages when compared to concurrent delivery methods, the Feldan Shuttle platform is becoming the centrepiece of novel cell therapies by accelerating the transition of medical discoveries into clinical applications.


The ease of use of the Shuttle platform is complemented by a rigorous optimization know-how by Feldan Therapeutics that allows the delivery of diverse types of proteins into hard-to-transfect cells.


Feldan Shuttle can mediate protein delivery in various cell types with high efficienty. Such high delivery efficiency is not obtained at the cost of cell viability.

THP1 and HeLa cells GFP protein delivery - Feldan Shuttle

Because the Shuttle is dislodged from the cargo upon cellular uptake, the shuttled protein can than localize in its target organelle. Subcellular targeting of an engineered GFP (GFP-NLS) to the nucleus is quick and complete.

Hela - Protein delivery - Feldan Shuttle
Click here for a video 3D visualization of the GFP-NLS inside nuclei

Time course - nuclear import - final

Feldan Shuttle is flexible enough to deliver proteins into primary cells and Pluripotent Stem Cells (PSCs). Images shown here illustrate the delivery of model GFP protein in mesenchymal stem cells (MSCs) and PSCs. Delivering relevant proteins into clinically relevant cell types is the basis of our clinical therapeutic pipeline.

MSCs and PSCs - GFP - final 3

The shuttling of an undisclosed transcription factor depicted herein demonstrates the capacity of the Feldan Shuttle to deliver a functionally active protein in the nucleus. Indeed, this transcription factor was detected in the cell nucleus and shown to have had a deep and controlled impact on genes reported to be under its regulation. This proof of concept opens new avenues for the control of gene expression and will become a valuable element in the design of novel cell therapies.

Transcription factor - delivery by Feldan Shuttle - final 2


In addition to transcription factors, the Feldan Shuttle delivers other proteins with therapeutic potential such as nucleases. Active CRISPR/Cas9 complexes were shuttled inside cell nuclei and have shown their gene editing activity on the genome of those cells. This very important achievement proves the potential of Feldan Shuttle to translate genome editing technology in therapeutic applications. In that context, Feldan Shuttle’s biggest strength resides in the fact that it is a highly efficient non-viral delivery technology and therefore lessens the regulatory and experimental burdens currently associated with other delivery methods.

Cas9 - immunofluorescence - final Cas9 - genome edition - final 2
  • Chemical-, virus-, DNA- and RNA-free
  • 100% protein based shuttle, thus enabling its complete degradation by cells prior to patient transplantation
  • Improved dose control during reprogramming and differentiation processes (comparatively to gene transcription and/or virus infection)
  • Fewer regulatory constraints and lower cost of production when compared to production and homologation of viruses for clinical trials
  • Delivery of unmodified protein
  • No covalent link shuttle/cargo
  • Simple experimental protocol
  • Efficient in the presence of serum
The application field of this platform is wide, and most notably includes:
  • Improvement of cell expansion
  • Genome editing
  • Reprogramming to generate Induced Pluripotent Stem Cells (iPSCs)
  • Transdifferentiation (differentiation into a specific cell type)