Alzheimer Peptide with successful phase I trial

Priavoid, a company based in Jülich (Germany), has successfully completed a Phase I project with peptides consisting of D-amino acids instead of the natural occuring L-configuration.
What are the differences between proteins, peptides and amino acids and and how did these molecules originally come about?

Proteins - Peptides - Amino acids: What is a Peptide?

What is a peptide and how is it formed in nature respective a living cell? What are the applications of peptides in diagnostic and medicine?
Peptides show an ever increasing interest in specific therapeutics or for coating surfaces