Japan’s top drugmakers have predicted a drop in profits this year as patent protection over several major products slip, putting strong pressure on a weak drug pipeline.

Takeda Pharmaceutical has unveiled a three-year business plan, under which it expects an operating income of ¥290bn in the year to March 2013, nearly a third less than the year that just ended.

Rival Daiichi has also forecasted a drop of 18% in its profits to ¥85bn, while Astellas confirmed that its January to March recurring profit slumped 75%. It has forecasted a 19% drop to ¥155bn in the year to next March.

Losing patent protection over major drugs is seen to be a major factor, with Takeda set to loose protection over its bestselling diabetes treatment, Actos, in the US in January, unless a patent violation lawsuit filed by the company is successful.

Daiichi has also suffered after low sales of its flagship blood-thinner Effient but expects some growth after late-stage trials of its oral blood clot preventer Edoxaban.

Weakening sales have also prompted a major shift towards overseas by companies such as Astellas, which is carrying out a $3.5bn bid for US cancer specialist OSI.

Takeda has also made similar forays, such as the purchase of US biotech firm Millennium Pharmaceuticals for around $9bn in 2008.