Merck & Co has signed a collaboration with Ra Pharmaceuticals to develop a new class of compounds called cyclomimetics.

Under the agreement, Ra's proprietary Extreme Diversity platform will be used to generate candidates for protein targets in multiple therapeutic areas. Cyclomimetics are peptide-like molecules characterised by their cyclic structure and backbone and side-chain modifications "that provide unique, beneficial properties not found in natural peptides", said Ra.

The result, the Cambridge, Massachusetts-based biotech says, "is a highly specific and stable molecule with improved cell permeability and the potential for greatly increased bioavailability". Ra claims its platform is unique in that it combines in vitro display technology, a completely defined translation system and a wide variety of non-natural amino acids.

Unlike certain other display technologies, in vitro display does not require the use of a bacterial or yeast host, and it can produce libraries of 10 to 100 trillion members. Also, the technology has the potential to address protein-protein interactions and other previously undruggable targets, Ra adds.

Cashwise, Merck will pay up to $200 million in payments, including up-front and research funding, as well as discovery, development, regulatory and commercialisation milestones. Richard Tillyer, head of drug discovery and preclinical sciences at Merck Research Laboratories, said the agreement with Ra "underscores our strategy of collaborating with scientists who have developed innovative new technologies with the potential to complement and enhance our original research and product portfolio".