Sanofi (SNY 1.16%) announced a fresh acquisition on Monday morning. The sprawling pharmaceutical company said it has agreed to purchase biotech Principia Biopharma (PRNB) for $100 per share in an all-cash transaction. This equates to a total outlay of roughly $3.68 billion.

Principia specializes in the development of drugs to treat autoimmune disorders, a very active product category in the pharmaceutical industry just now. The company currently has three pipeline treatments; two of these are currently undergoing phase 3 clinical testing. One, Rilzabrutinib, targets pemphigus, a rare disease that can result in the development of blisters on the skin and on mucous membranes.

Numerous pills and vials atop $100 bills.

Image source: Getty Images.

Sanofi and Principia are already business partners. In 2017, Sanofi was granted an exclusive global license to develop one of its pipeline drugs, BTK inhibitor '168, for the treatment of certain lesions arising from multiple sclerosis. Like Rilzabrutinib, BTK inhibitor '168 is currently in a phase 3 trial.

"This acquisition advances our ongoing R&D transformation to accelerate development of the most promising medicines that will address significant patient needs," according to Sanofi CEO Paul Hudson. 

This is Sanofi's second major acquisition with Hudson at the helm. Last December, the company struck a deal to acquire clinical-stage immuno-oncology specialist Synthorx in a transaction valued at $2.5 billion.

The Sanofi/Principia deal, which the acquirer said will be funded from cash on hand, is subject to approval from the relevant regulatory bodies. Sanofi expects it to close in the fourth quarter of this year.

Investors seem to approve of the new acquisition. Sanofi closed just over 2% higher on Monday, well outpacing the gains of the broader stock market.