AstraZeneca will license experimental drugs for obesity and weight-related conditions from CSPC Pharmaceutical Group and collaborate on additional projects, paying $1.2 billion upfront and up to $17.3 billion more if development and sales milestones are met, the Chinese drugmaker said on Friday.

The deal is the latest tie-up between the two pharmaceutical giants, following collaboration in areas such as artificial intelligence. It expands AstraZeneca's investment in the growing obesity market led by Western rivals.

The British-Swedish drugmaker has also licensed an experimental weight-loss pill from China's EccoGene.

CSPC shares were down about 12% in Hong Kong following the announcement.

"This reflects the classic 'buy the rumour, sell the news' phenomenon," said Tony Ren, head of Asia healthcare research at Macquarie Capital, adding that investors seemed to be offloading the stock after its 26% surge since January 2.

The newly licensed drug candidates from CSPC include SYH2082, a "clinical-ready" product, and three other pre-clinical products in its injectable weight-management portfolio, the company said in a filing to the Hong Kong Stock Exchange.

The agreement covers the development, manufacturing and commercialisation of the candidates. AstraZeneca has been granted a global licence, excluding Taiwan, Hong Kong, Macau, and mainland China.

AstraZeneca will also collaborate on four additional new programmes with CSPC, using CSPC's proprietary platforms for sustained-release delivery technology and AI-driven peptide drug discovery.

A spokesperson for AstraZeneca said in a statement the new CSPC Pharmaceutical deal was in addition to a previous $15 billion investment in China that it announced on Thursday.