The third week of December was a busy one for AstraZeneca.

Just days after the British-Swedish drugmaker confirmed talks with privately owned biotech Acerta Pharma about an acquisition, the two companies declared “fait accompli” on Dec. 17. Simultaneously, AstraZeneca announced the completion of its purchase of ZS Pharma, plans for which were unveiled in November.

A day earlier, AstraZeneca had unveiled an agreement to buy Japanese pharmaceutical producer Takeda’s core respiratory business. This includes the expansion of rights to roflumilast (sold as Daliresp in the US and Daxas in other countries), the only approved oral PDE4 inhibitor for the treatment of chronic obstructive pulmonary disease (COPD).

In the most closely watched deal, the recently acquisitive drugmaker said it had agreed to pay $4 billion to acquire 55% of the issued share capital of Acerta, which has operations in the Netherlands and California.

Acerta is currently developing acalabrutinib, an experimental blood cancer drug also known as ACP-196, for the treatment of various malignancies, including leukemias and lymphomas. Results from recent Phase I/II trials are said to have shown the drug to be extremely effective.

The acquisition price will consist of an upfront consideration of $2.5 billion and a further unconditional consideration of $1.5 billion – to be paid either on receipt of the first regulatory approval of acalabrutinib for any indication or at the end of 2018, whichever is earlier.

Additionally, the agreement provides options for AstraZeneca to buy the remaining 45% stake for$ 3 billion. The terms are conditional on the drug being approved for sale in the US and Europe and certain other conditions.

Commenting on the Acerta deal, AstraZeneca CEO Pascal Soriot said the company is boosting a key area in its comprehensive oncology portfolio with a late-stage, potential best-in-class medicine that could transform treatment for patients across a range of blood cancers.