TOKYO – Japan's Chugai Pharmaceutical Co. Ltd. said it plans to "vigorously challenge" patent infringement claims made by U.S.-based biopharma Baxalta, which has filed suit in regards to the investigational monoclonal antibody emicizumab, in a move that could put in danger the Japanese company's pipeline and development plans.

Baxalta, now a subsidiary of Shire plc, filed a lawsuit in the U.S. District Court for the District of Delaware requesting an injunction to prevent Chugai from manufacturing, using, offering or selling emicizumab in the U.S. or importing the drug to the U.S. According to the complaint, a patent titled "Factor IX/Factor IXa Activating Antibodies and Antibody Derivatives," was issued to Baxter Aktiengesellschaft on April 25, 2006. That was later assigned to Baxalta Inc. and Baxalta GmbH in March 2016 and "is fully maintained and is valid and enforceable."

The complaint lists Chugai and Genentech Inc. as the defendants. Chugai is the originator of emicizumab and is conducting joint global clinical trials with Genentech, the company responsible for clinical development and marketing in the U.S., as well as with Genentech parent company Roche Holding AG.

Baxalta filed a similar lawsuit against Chugai in Tokyo last year.

"Baxalta alleged that emicizumab is infringing one of its patents [patent number 4313531] and thus it filed for an injunction against the manufacture, usage, transfer, exportation, and offer of any transfer regarding emicizumab, and requested cessation," Koki Harada, media relations manager at Chugai Pharmaceutical, told BioWorld Asia. "The lawsuit is currently pending at the Tokyo District Court. Chugai is vigorously pursuing defense with confidence that emicizumab does not infringe the patent."

Baxalta declined to comment on both lawsuits.

Emicizumab is a bispecific monoclonal antibody that potentially provides the co-factor function of factor Vlll in people with hemophilia A, who either lack or have impaired coagulation function of factor Vlll. Chugai and its partners are conducting four global phase III studies, HAVEN 1 through HAVEN 4. In 2016, the drug received orphan drug designation by the Japanese Ministry of Health, Labour and Welfare (MHLW). That designation, based on criteria such as the small number of eligible patients in Japan and significant medical value, allows for priority review status. Emicizumab was also granted breakthrough therapy designation by the U.S. FDA in 2015.

If Baxalta win the case, there could be substantial damage to Chugai's product pipeline and agreements with other companies.

Chugai also has a license agreement for emicizumab with JW Pharmaceutical Corp., inked on May 10, granting the latter the exclusive marketing rights for the drug in Korea. Chugai is entitled to up-front and milestone payments, as well as royalties.

"Hemophilia patients bear an enormous burden, and emicizumab is attractive because of its effectiveness and usability. The expectation [for emicizumab] comes from the expectation that it is superior to existing treatments," Fumiyoshi Sakai, senior pharmaceutical analyst at Credit Suisse Securities (Japan), told BioWorld Asia.

"As far as the lawsuit is concerned, the situation where Baxalta wins the lawsuit and Chugai and Roche cannot put this drug on sale is difficult to imagine," he said. "It would be a different story if emicizumab were a dangerous drug, but being unable to put this drug on sale because of patent reasons despite the effectiveness of the drug is a moral hazard, and so what often happens is that Roche and Chugai will pay some sort of royalty and settlement fee in order to put this on the market, and this is likely to happen."

Baxalta anticipates Chugai and other associated companies to start selling emicizumab in the fourth quarter of this year, pending FDA approval.

Headquartered in Tokyo, Chugai is a subsidiary drug manufacturer of F. Hoffmann-La Roche AG, which owns 62 percent of the company as of June 2014.

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