AstraZeneca has bumped up its stake in US biotech Moderna, which is pioneering the development of a new class of drugs made of messenger RNA, to nine percent.

The UK-listed group said it is investing a further $140 million to increase its equity interest in the company, adding to its previous stake garnered through a collaboration agreement signed back in March 2013.

The parties initially hooked up to develop medicines for cardiovascular, metabolic and renal diseases, as well as oncology, and subsequently signed another agreement in January this year solely focused on the development of cancer therapies.

The companies coupling AstraZeneca group MedImmune's protein engineering and cancer biology expertise with Moderna's technology platform in the hope of developing new mRNA-based therapies.

These enable the body to produce therapeutic protein in vivo, and thus potentially offer a new treatment approach for a wide range of diseases.