After Japanese regulators turned away the partners’ submission for a new cell-culture flu vaccine, Astellas has pulled the plug on a collaboration with UMN Pharma.

UMN said it’s "regrettable" the companies can no longer work together to push the vaccine, Protein Sciences’ Flublok, to the market in Japan. The pharmas first linked up back in 2010.

The shot had previously met its endpoints in a phase 3 trial, according to a release from UMN, and development partner Astellas submitted a marketing application to Japanese health authorities in May 2014. The Pharmaceuticals and Medical Devices Agency considered the risks and benefits, and notified Astellas that it would not further conduct its review; Astellas moved to withdraw the app.

UMN Pharma "strongly disagrees" with the PMDA’s assessment, saying it believes the agency "ignored or did not understand" the "compelling evidence of superior safety and efficacy … that should have resulted in licensure."

UMN has a license to Protein Sciences’ Flublok in Japan, China, Korea, Hong Kong, S.A.R., China, Taiwan, China and Singapore, according to a recent release. A joint venture partially owned by UMN is set to manufacture the shot for the U.S. under a deal reached early last year.

In the U.S., Protein Sciences has big ambitions for its flu vaccine technology. As CEO Manon Cox recently told FiercePharma, the company believes it’ll be the "product of choice in time." The company is hoping to "take over" a flu vaccine market dominated by pharma giants Sanofi and GlaxoSmithKline.

Indeed, as the market evolves, smaller companies are poised to carve out a "sizable" share, according to GlobalData analysts. The firm recently said that biotechs such as Protein Sciences, Mitsubishi Tanabe and Novavax will be able to claim at least one-quarter of total flu vaccine sales with new cell manufacturing technology.

After canceling the UMN deal, Astellas will write off the investment with a 4 billion yen impairment charge—nearly $35 million—in its upcoming financial statements. When the separation is complete, the technology will transfer back to UMN.

From there, UMN said it’ll decide whether to reapply for licensing in Japan "after assessing the feasibility including costs and time."