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Synthorx Files for IPO to Advance Enhanced Cytokine Drugs

Xconomy San Diego — 

Synthetic biology company Synthorx is laying plans for an initial public offering to raise money to advance its suite of enhanced cytokine drugs.

The San Diego-based company says it wants to use the proceeds to put its lead product candidate, an investigational cancer therapy that’s based on the drug interleukin-2 (IL-2), through dose escalation and expansion trials, and to develop products based on the same compound to treat autoimmune disorders.

It has now set a preliminary $100 million IPO target in documents filed with securities regulators Tuesday. The company has applied for a listing on the Nasdaq exchange under the stock symbol “THOR.”

The company’s technology—which it licensed from The Scripps Research Institute in 2014—is facilitating its development of enhanced versions of proteins called cytokines, which regulate immune and inflammatory responses.

Synthorx says its platform, through which the company has shown it can force E. coli bacteria to produce a variety of synthetic amino acids by inserting into the bacteria a new DNA base pair, is allowing it to develop improved versions of cytokine drugs.

About six months ago, the company raised a Series C round totaling $63 million.

That financing round was led by New York private equity firm OrbiMed. Medicxi and Osage University Partners also participated, as did founding investors Avalon Ventures and Correlation Ventures and earlier investor RA Capital Management.

Avalon (and its affiliated entities) is the company’s largest stockholder, owning nearly one-third of its shares. Boston’s RA Capital (and affiliated entities) and OrbiMed are the next two largest shareholders, with about 28 percent and 22 percent, respectively. Correlation, with about 6 percent, rounds out the four entities that have more than 5 percent of Synthorx’s stock.

Synthorx said in the prospectus that it plans to study its version of IL-2, dubbed THOR-707, as a treatment for solid tumor cancers on its own and in combination with an immune checkpoint inhibitor.

It also said it intends to develop a separate IL-2 program to treat chronic autoimmune disorders, and that it is in the process of selecting a lead product candidate that will allow it to overcome the current limitation to using IL-2 for such conditions—its short half-life. Synthorx said it plans to file for permission to start clinical trials in 2020, and initially intends to target chronic graft versus host disease (GVHD), atopic dermatitis, and Crohn’s disease.

It has also identified other cytokines it intends to develop.

Synthorx is based in La Jolla at COI (for Community of Innovation) Pharmaceuticals, an incubator that provides shared facilities and management for Avalon portfolio companies.

Jay Lichter, an Avalon partner and CEO of COI, served as Synthorx’s interim CEO for a short time in 2017. Today the biotech is led by president and CEO Laura Shawver, who has been the company’s chief executive for about a year.

In August, the company appointed Joseph Leveque as its chief medical officer. Leveque was previously at Redwood City, CA-based cancer drug developer Armo Biosciences, which was acquired this year by Eli Lilly (NYSE: LLY) for $1.6 billion.