Cephalon is continuing its acquisition spree and intends to pay $163 million for the shares is does not already own in Australian haematology specialist ChemGenex Pharmaceuticals.

The US firm has converted notes it held in ChemGenex into shares, giving it a 27.6% stake and is now offering A$0.70 cash for each share it does not already hold and A$0.02 for each ChemGenex option. The share offer represents a 59% premium to the Melbourne-headquartered firm stock's last traded price and values the company (shares and options) at A$225 million (around $231 million).

Buying ChemGenex gives Cephalon full access to Omapro (omacetaxine) for the treatment of chronic myeloid leukaemia. It recently completed Phase III clinical trials and a New Drug Application is expected to be filed with the US Food and Drug Administration in the second half of 2011.

Cephalon chief executive Kevin Buchi said the deal allows ChemGenex shareholders "to realise cash proceeds at a significant premium to recent trading levels and adds an interesting late-stage opportunity to our portfolio". The Australian firm has accepted Cephalon's bid and will recommend it to shareholders "in the absence of a superior offer".

The news comes less than a week after Cephalon agreed to buy cancer specialist Gemin X Pharmaceuticals for $225 million in cash, plus up to $300 million more in milestones.