Peptidomimetic macrocycles

A method of preparing a polypeptide with optimized cellular efficacy in human whole blood, the method comprising:

• (a) providing a parent polypeptide comprising a cross-linker connecting a first amino acid and a second amino acid of the parent polypeptide, and wherein the parent polypeptide penetrates cell membranes by an energy-dependent process and binds to an intracellular target;
• (b) producing a modified polypeptide having the same sequence as the parent polypeptide sequence except that at least one acidic side chain in the modified polypeptide is replaced with a neutral side chain;
• wherein the acidic side chain in the parent polypeptide is adjacent to a large hydrophobic side chain and is not essential for target binding, and wherein the modified polypeptide comprises a cross-linker connecting a first amino acid and a second amino acid of the modified polypeptide;
• (c) measuring an in vitro efficacy of the modified polypeptide in a whole cell assay wherein activity of the modified polypeptide is mediated by binding of the modified polypeptide to the intracellular target, in the presence and absence of human serum;
• (d) calculating an apparent affinity (Kd*) of the modified polypeptide to human serum proteins and an EC50 of the modified polypeptide;
• and
• (e) selecting the modified polypeptide as an optimized polypeptide if the modified polypeptide has a higher Kd* and an equal or lower EC50 than the parent polypeptide.