Sanofi-Aventis says it has completed its $20.1 billion offer for Genzyme Corp, now that 84.6% of the latter's outstanding shares of common stock have been tendered.

The French drugmaker notes that it holds approximately 77% of the shares on a fully-diluted basis, giving it control of Genzyme. Remaining stockholders have until Thursday to tender their shares and they will receive the same amount, $74.00 in cash, for each share held.

Sanofi chief executive Chris Viehbacher said the addition of Genzyme represents an important milestone in the firm's "sustainable growth strategy by adding a meaningful new growth platform and expanding our footprint in biotechnology". He added that “already, we are making progress on the tremendous opportunities that are possible by bringing these two companies together through the integration process, which is progressing well and remains on track".

Genzyme's outgoing boss Henri Termeer noted that "the process we have started with Sanofi has confirmed the enormous opportunities that exist by combining our two companies". He went on to say that "this moment is a catalyst for change within both organizations" and Genzyme will remain a vibrant business.

Genzyme cancer pact with Algeta

Meantime Genzyme has signed a deal with Norwegian cancer specialist Algeta which will team one of the former's "novel and proprietary tumour-targeting antibody" with the Oslo-based group's Thorium platform "to attach the alpha-emitting payload thorium-227".

Both companies will contribute resources towards the collaboration, which is expected to last for up to a year initially. Algeta's chief technology officer Thomas Ramdahl said the firm has "has previously demonstrated the promise of our alpha-emitter thorium-227 as a payload and we now look forward to applying our Thorium platform to this novel antibody.”

Algeta noted that Thorium-227 is an element that emits high-energy alpha particles which are potent at killing tumour cells and have a highly localised effect. It says that "current top-selling cancer drugs are based on 'naked' monoclonal antibodies, but it is clear that next-generation products will require cancer-killing payloads to maximise the effectiveness of therapy".