Moderna Therapeutics Inc., the Cambridge biotech that has stockpiled more than $1 billion to develop a new class of therapies, is back in fund-raising mode.
The five-year-old company disclosed in a recent regulatory filing that it is seeking $600 million in fresh equity and has so far sold shares valued at $451.4 million to unspecified investors.
Moderna, launched by the local venture capital firm Flagship Ventures, has attracted widespread interest in the biopharma world by pioneering a technology called messenger RNA that can carry protein replacement drugs inside cell membranes, where they can help fight cancers and other genetic disorders. The company is also developing an approach that could enable it to rapidly deliver dozens of new treatments for a broad range of diseases.
Unlike biotech startups that have tapped the public markets through initial public offerings of stock, Moderna has remained a private company. It has amassed its cash from blue-chip venture capital and private equity firms and a series of research partnerships with established drug makers that have purchased equity in the company.
With nearly 400 employees working at two locations in Kendall Square, the company is scouting for a site in the Boston suburbs to build a drug manufacturing plant. It has 11 drugs under development and two in clinical trials, according to a midyear report issued last month.
Moderna representatives said they weren’t ready to discuss the new funding round.
But part of the company’s new financing appears to have come from the Anglo-Swedish pharmaceutical giant AstraZeneca PLC, which disclosed this month that it had added $140 million to its investment in Moderna, boosting its stake to 9 percent. The two companies are working together on drugs to treat cancer along with cardiovascular, metabolic, and renal diseases, using Moderna’s messenger RNA technology.
Moderna first gained attention early in 2015, when it secured $450 million in financing — one of the largest private biotech investments ever — from a consortium that included institutional giants Viking Global Investors, Invus, RA Capital Management, and Wellington Management Co.
Since then, it has signed research alliances with Merck & Co. on personalized cancer vaccines, Alexion Pharmaceuticals Inc. on drugs for rare liver diseases, and AstraZeneca.
Last month, Moderna announced it was teaming up with Boston-based Vertex Pharmaceuticals Inc. to develop treatments for cystic fibrosis. That collaboration, which could be worth up to $315 million to Moderna, also gave Vertex a $20 million equity stake in the Cambridge company.
“We’re playing a very long game,” Moderna’s chief executive, Stephane Bancel, said last month. “Our goal is to bring the best medicines to patients, and we always like to start with a partner who can bring expertise to a new area we’re looking at. It’s about whatever organ system we can get messenger RNA into.”
Prior to the Vertex deal and the expansion of AstraZeneca’s investment, Moderna said it had taken in about $237 million from its strategic partners. The company has yet to disclose the percentage stake each partner has taken in Moderna.
Robert Weisman can be reached at firstname.lastname@example.org. Follow him on Twitter @GlobeRobW.