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Autor/a
Roig Martínez, Albert
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Abstract
Glioblastoma multiforme (GBM) is the most malignant primary brain tumor and is currently incurable. One of the main obstacles to its treatment is the restricted transport of drugs across the blood-brain barrier (BBB). This TFG focuses on the development of peptides capable of overcoming BBB and is part of a European project that aims to generate a gene nanotherapy focused on the treatment of GBM.
Peptides fall between the realm of small organic molecule-based drugs and biotherapeutic agents, allowing them to combine the best of both worlds. Like proteins, peptides have high affinity and selectivity and, like small molecules, are synthetically accessible, easy to derive, and often have low immunogenicity. However, the main obstacle to a broader application lies in their susceptibility to degradation by proteases.In the first part of this work, we review the main strategies to confer high metabolic resistance to peptides and the relevance of introducing these modifications in its ability to reach the biological target of interest. Although there is a wide range of peptide modification strategies available, most of the research carried out has focused on introducing D amino acids or restricting conformational flexibility through cyclisation. On the other hand, although conjugation to a bulky filler can provide some steric shielding protection, increasing the peptide's resistance to proteases substantially increases its efficiency.In the second part of this work, we have applied the cyclization strategy to a peptide related to the transferrin receptor (Y1), with the aim of increasing its resistance to proteases and its affinity for the receptor. We have designed a library with the linear, cyclic and bicyclic versions of this peptide preserving the predicted secondary structure. Linear versions were successfully synthesized by solid phase peptide synthesis, as assessed by MALDI-TOF and UPLC-UV. In relation to the cyclisation with a trifunctional scaffold (TBMB), the approach both in resin and in solution gave rise to the formation of the desired cyclic peptides. We found that the N-terminal glycine and the Fmoc protecting group played an important role in the efficiency of cyclization. Finally, an attempt was made to conjugate the carboxyfluorescein peptides to facilitate the study of their interaction with cells. Although the conjugation reaction was only achieved on a small scale and requires optimization, coupling of Cf to the N-terminus of the linear peptide (more accessible) and subsequent cyclization turned out to be the most promising strategy.
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