Under the agreement, Simcere has the right to manufacture and sell zanamivir in China, Indonesia, Thailand, Vietnam and all least developing countries (LDCs).
Of the more than 240 cases reported in which humans have been infected with H5N1 influenza virus, more than half have occurred in Asia-Pacific nations or in the LDCs, so GSK has committed over $2bn (€1.57bn) to expand capacity for manufacturing flu vaccine and Relenza.
GSK's competitor, Roche, has already put in place a number of arrangements with developing countries for the manufacture and use of the Tamiflu, ranging from licensing to sub-contract manufacturing agreements with more than 16 partners in ten different countries.
For example, the Swiss drug giant has granted sub-licenses to Shanghai Pharmaceutical Group and to HEC Group for the production of Tamiflu for pandemic use in China, as well as to India's Hetero Drugs to make the medicine for India and developing countries.
Roche has also reached an agreement with Aspen for providing Tamiflu for pandemic use to further help to address the needs of governments and other not-for-profit organizations in Africa.
On the other hand, GSK announced several months ago that it was seeking partners for Relenza but this is the first deal it has managed to strike, as Relenza is less popular because it is administered via an inhaler and is not a pill like Tamiflu.
"GSK is doing everything we can to prepare for a global influenza pandemic, including expanding production of Relenza and developing a pandemic vaccine," said David Stout, president of the company's pharmaceutical operations.
"This agreement with Simcere is intended to expand available supplies of zanamivir in areas of the world that may be on the front line of a possible influenza pandemic."
Relenza was developed by GSK under licence from drug firm Biota, which, under the sub-licence, will be entitled to receive royalties on sales by Simcere.
"When GSK requested Biota's approval for this agreement with Simcere, it was readily given in recognition of the critical public health need," said Biota CEO Peter Cook.
"We hope to see GSK further increase supply to ensure that the world is able to gain better access to zanamivir, one of the world's only two effective antiviral drugs in the event of an avian flu pandemic."
Indeed the sub-licensing of drugs needed in the developing world is becoming increasingly popular with drugmakers that seek to improve their image in the western world.
Under pressure to respond to the spread of HIV, last month Gilead signed non-exclusive licence agreements with eight Indian generic companies for the manufacture of Viread (tenofovir disoproxil fumarate), its popular antiretroviral.
Roche has also said it will provide three African companies free of charge with the technical expertise to manufacture a generic version of its HIV protease inhibitor Fortovase (saquinavir).