San Diego’s aTyr Pharma says today it has closed on $59 million in a Series D financing to advance its development of a new class of protein-based drugs for treating rare immune diseases.
The $59 million deal includes $49 million in venture funding raised in recent months from an unnamed “global public investment fund” and aTyr’s existing venture investors—Alta Partners, Cardinal Partners, Domain Associates, and Polaris Partners. Silicon Valley Bank provided an additional $10 million in debt financing.
The Series D deal is bigger than the $47 million in total venture capital funding that aTyr raised through three previous rounds, aTyr CEO John Mendlein told me in a recent telephone interview (and brings total funding to $108 million since aTyr was founded eight years ago). The latest round is intended to enable aTyr to bring its first therapeutic program into the clinic and to continue to build out the company’s pipeline of additional therapies, Mendlein said.
The funding should enable aTyr, (pronounced A-tire), to stage multiple human proof-of-concept trials of drugs derived from a new class of natural proteins called “physiocrines” that represent a promising new area of biology. Research led by Dr. Paul Schimmel of The Scripps Research Institute and others showed that physiocrines are naturally occurring proteins (derived from tRNA synthetases) that regulate immune response and help maintain homeostasis, or equilibrium. Schimmel is a scientific founder of aTyr, and continues to serve on the company’s board.
“These new proteins are associated with an ancient gene family previously associated with protein synthesis,” Mendlein said. “We’ve discovered new pathways in modulating the immune system that were previously unknown.” Instead of blocking or inhibiting target molecules, however, Mendlein said physiocrines act sort of like a carburetor, by revving up or throttling back an immune response rather than turning it off completely.
The company maintains that physiocrines offer potential therapeutic advantages to existing anti-inflammatory drugs through improved selectivity, efficacy, and reduced side effects.
Since Mendlein stepped in as aTyr’s CEO at the end of 2011 (he retained his executive chairman title), the company has narrowed its
