Expansion Therapeutics officially launched with the close of a $55.3 million Series A financing. The round was co-led by 5AM Ventures, Kleiner Perkins, Novartis Venture Fund,and Sanofi Ventures. RA Capital Management and Alexandria Venture Investments participated.

Expansion will focus on discovering and developing drugs based on targeting RNA. Initial efforts will be on expansion repeat disorders. There are about 30 expansion repeat disorders, which are marked by what can be described as a genomic stutter, where a series of three nucleotides repeats itself a number of times. Well-known triplet repeat disorders include fragile X syndrome, Huntington’s disease and spinocerebellar ataxias. The company’s initial focus will be on myotonic dystrophy type 1 (DM1).

"Expansion repeat disorders, in particular DM1 represent an attractive first application of our technology as it is well established that toxic RNA drives disease," said the company’s president and chief executive officer, Kevin Forrest, in a statement. "Furthermore, our small molecule approach has the potential to address both peripheral and central symptoms that are debilitating for patients."

DM1 affects 1 in 8,000 people, or about 40,000 in the U.S. It is the most common cause of adult onset muscular dystrophy. It is caused by a toxic expansion in RNA. This can lead to multi-systemic symptoms that include defects in the muscles, heart, lungs, gastrointestinal tract, endocrine system and central nervous system.

"In a short period of time Expansion has assembled a leading team, the key scientific founder in Matt Disney of The Scripps Research Institute Florida, and a capital efficient plan to advance the emerging field of RNA targeted small molecule medicines," said Scott Rocklage, managing partner of 5AM Ventures and founding investor and chairman of the board of directors of Expansion, in a statement. "We look forward to continuing to work with the company to develop medicines for patients with few treatment options."

Along with the Series A, the company’s co-founder, Kevin Forrest, was appointed president and chief executive officer. Forrest was previously the founding chief operating officer and chief financial officer for Cidara Therapeutics. Before that he was a principal at 5AM Ventures.

The company’s board of directors will include: Scott Rocklage, Matthew Disney, Kevin Forrest, Jason Hafler of Sanofi Ventures, Yujiro Hata of Ideaya Biosciences, Campbell Murray of Novartis Venture Fund, Beth Seidenberg of Kleiner Perkins, and Andrew Levin of RA Capital Management.

Expansion Therapeutics was incubated within 5AM Ventures’ 4:59 Initiative, followed by seed funding by 5AM and Sanofi Ventures. Its key technology platform was developed in Disney’s laboratory at The Scripps Research Institute.

Expansion’s scientific advisory board includes: Robert Batey, University of Colorado, Boulder; Dale Boger, The Scripps Research Institute; Ronald Breaker, the Howard Hughes Medical Institute and Yale University; MG Finn, of the Georgia Institute of Technology; David Mathews of the University of Rochester; Michael Zuker, of the Rensselaer Polytechnic Institute.

"I am gratified that our efforts over the past dozen years have culminated in this important opportunity," Disney said in a statement. "It is clear that disease-related RNA is now an addressable target with small molecule medicines and we are now on the verge of developing treatments for patients with the most urgent medical needs. We will work tirelessly to fulfill this promise."