New-York-based biopharmaceutical company Pfizer Inc. is close to purchasing Swiss biotechnology company Therachon for $840 million.

The transaction will enable Pfizer to gain a clinical product, known as TA-46, to treat patients with Achondroplasia, further boosting Pfizer's pipeline.

So far, Pfizer has paid an upfront payment of $370 million to acquire Therachon, with the remaining $470 million to be paid as milestones are met.

Before the transaction closes, Therachon will spin out its GLP-2 analog Apraglutide into a separate company, under which Pfizer will hold an investment on with its venture capital arm.