By Sam Nussey
TOKYO (Reuters) - Britain's AstraZeneca PLC (L:AZN) offered to buy peer Daiichi Sankyo Co Ltd (T:4568) last year, a business magazine reported on Thursday, sending the Japanese drugmaker's share price soaring as much as 13 percent and triggering a trade suspension.
Daiichi Sankyo, which has a market value of about $16 billion (12.42 billion pounds), declined the offer, the online version of Nikkei Business reported citing unidentified sources.
AstraZeneca and Daiichi Sankyo declined to comment when contacted by Reuters.
AstraZeneca may have targeted Daiichi Sankyo for its expertise in antibody drug conjugates, a new kind of "armed antibody" that can carry a cancer-killing payload to tumour cells, the magazine reported.
The two firms have a long-standing relationship which includes a 2015 agreement to jointly commercialise constipation drug Movantik in the United States, and a 2010 deal to supply and promote blockbuster heartburn treatment Nexium in Japan.
Last month, AstraZeneca's prospects in cancer drugs suffered a setback when an immunotherapy treatment failed to help patients in a closely watched trial.
That led to speculation of AstraZeneca itself becoming a takeover target.
The drugmaker has been banking on cancer treatment to help revive its fortunes following a wave of patent expirations on its biggest products, but a decline in cash flow could impact its ability to make any major acquisitions.
It has "limited flexibility around the balance sheet", Goldman Sachs (NYSE:GS) analysts said in a report this week, given a need for ongoing investment and commitments to prior acquisitions, including Acerta, for which it has further payment obligations.
At Daiichi Sankyo, the Japanese drugmaker earlier this year said it would spend 15 billion yen ($136 million) to raise production of antibody drug conjugates.
On Wednesday it announced a tie-up to test a combination of its antibody drug conjugate DS-8201 with immuno-oncology drug Opdivo from Bristol-Myers Squibb Co (N:BMY).
Daiichi Sankyo's share price was up 5 percent when trading was suspended. AstraZeneca was little changed in early London trade.
(This version of the story has been refiled to correct spelling of Daiichi in paragraphs 10, 12)