How Big Is Too Big for Cell Permeability?

Area of Science:

• Drug Discovery
• Medicinal Chemistry
• Molecular Biology

Background:

• Designing cell-permeable ligands for intracellular targets, especially those with difficult binding sites like protein-protein interactions, presents a significant challenge in drug discovery.
• Current drug discovery efforts often face limitations with larger molecules due to membrane permeability issues.

Purpose of the Study:

• To explore the largely untapped chemical space between 500 and 1000 Da for the development of novel cell-permeable ligands.
• To identify opportunities for drug discovery beyond the apparent molecular weight cutoff for membrane permeability.

Main Methods:

• Analysis of existing peptide libraries, focusing on cyclic peptides.
• Investigating the relationship between molecular weight and membrane permeability.
• Computational and experimental screening of compounds within the 500-1000 Da range.

Main Results:

• Cyclic peptide libraries exhibit a significant decrease in membrane permeability for molecules exceeding 1000 Da.
• This 1000 Da threshold appears to be a general upper limit for membrane permeability in druglike compounds.
• The chemical space between 500 and 1000 Da remains largely unexplored for drug discovery.

Conclusions:

• The 500-1000 Da molecular weight range represents a promising, yet underexplored, frontier for designing cell-permeable ligands.
• Overcoming the size limitation for membrane permeability in this range could unlock new therapeutic strategies for intracellular targets.
• Venture into this chemical space offers vast opportunities for innovative drug discovery.