Juno Therapeutics, the Seattle biotechnology startup unveiled in December by leading cancer scientists here and in New York, has announced another $134 million in financing, bringing its total funding to $300 million in less than a year.

The new funding comes from 10 public mutual funds and health-care-related funds, as well as all the major previous investors.

“The real goal behind this round — beyond it being a financing event — is to forge long-term relationships with investors,” Hans Bishop, CEO of Juno, said in an interview. “They are not just investing in clinical development, but in scientific questions that we really believe will allow us to make better products in the future.”

Juno is working to develop curative immunotherapy treatments for a variety of high-risk cancers. Its approach is to bolster a patient’s cancer-fighting immune responses by taking T-cells, which fight infections and cancers in the body, out of his or her body and reprogramming them to include receptors to help recognize and kill cancer cells.

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With the additional funding, Bishop says the company will continue advancing its product pipelines.

Three different clinical trials for blood cancers are currently running, and Bishop said he hopes to start the first trials with solid organ tumors next year. The company will also continue to invest in basic research and manufacturing technologies that will allow it to make its products.

The company, with offices in South Lake Union, was formed in partnership with Fred Hutchinson Cancer Research Center, New York’s Memorial Sloan-Kettering Cancer Center, and Seattle Children’s Research institute. It isn’t saying how large a work force it has built with its fat bankroll.

Juno’s initial $120 million startup financing in the fourth quarter of last year was the nation’s largest early-stage venture deal for that quarter, according to a MoneyTree report released in January by PricewaterhouseCoopers and the National Venture Capital Association. Prior to the current round, investors included ARCH Venture Partners, the Alaska Permanent Fund, Bezos Expeditions and Venrock.

The 2013 deal also accounted for nearly 25 percent of all the venture funding received by Washington companies for the quarter. According to MoneyTree reports for the first and second quarters of this year, the company raked in an additional nearly $55 million. Juno reports its total Series A funding as $176 million.

“Those kinds of raisings are fairly unprecedented … You don’t see companies raise $300 million in under a year,” said Chris Rivera, president and CEO of the Washington Biotechnology and Biomedical Association.

Biotech companies can burn through tens of millions of dollars quickly as they recruit scientists and conduct long, costly testing of products that are years away from potential revenues.

The rule of thumb, said Rivera, is that “When you have the opportunity to raise funding, you should do it.”

Jeff Grabow, the U.S. venture-capital leader at Ernst & Young, a global-accounting and consulting firm, agreed. He also has a name for funding rounds exceeding $50 million — mega rounds.

He calls the current trend in large venture-capital deals a “mega round phenomenon.” He said many mega rounds are associated with tech companies because they are easy to fund upfront, but need more money to scale up later.

Biotechnology companies like Juno, on the other hand, require a lot of capital at all levels for product development and to get a drug to market, he said.

With the resurgence of biotech companies, the market is receptive, he said.

“There is great opportunity to invest in companies like this,” he said. “We haven’t solved a lot of the problems that afflict man — there is still a lot of work to be done on cancer and other debilitating diseases.”

The latest $134 million deal comes five months after Juno brought in Steve Harr as CFO and head of corporate development. He previously spent 12 years at Morgan Stanley and is credited with managing more than $20 billion in financing deals.

Coral Garnick: 206-464-2422 or cgarnick@seattletimes.com. On Twitter @coralgarnick