Sanofi SA will acquire Principia Biopharma Inc. in a $3.68 billion deal that brings Sanofi three clinical-stage BTK inhibitors and simplifies a partnership that began three years ago.

Paris-based Sanofi plans to acquire all outstanding Principia common stock shares for $100 each at a $3.36 billion enterprise value. The transaction was unanimously approved by both boards.

Guggenheim Partners analysts wrote Monday that they believe the acquisition price is a fair one.

Sanofi will get SAR-442168 (PRN-2246), which is at the heart of the deal. John Reed, Sanofi’s executive vice president and global head of R&D, told investors in a call Monday morning that the acquisition means Sanofi will enjoy “full economics” of the program rather than “shared economics.” It also, Reed said, opens up the possibility of looking into other CNS diseases the company is not currently studying.

Bill Sibold, Sanofi’s executive vice president, told investors Monday morning that the deal strengthens the company’s core area of neurological disorders and allows it to focus more on specialty care. He also said the company has been interested in transactions like this one, which are valued at roughly €2 billion to €5 billion (US$2.38 billion to US$5.94 billion).

The Sanofi-Principia partnership began in 2017, via a deal that gave Sanofi an exclusive, worldwide license to develop and commercialize SAR-442168 in multiple sclerosis and other CNS disease. SAR-442168 began a phase IIb trial in patients with multiple sclerosis. Data showed SAR-442168 reduced Gd-enhancing T1 hyperintense lesions by 85% compared to placebo.

In late June, Principia enrolled its first patient in the clinical trial comparing SAR-442168 to Sanofi’s Aubagio (teriflunomide) and assessing annualized adjudicated relapse rate. The enrollment entitled Principia to a $50 million milestone payment from Sanofi.

Sanofi will also be getting an oral BTK inhibitor, rilzabrutinib, now in a phase III for patients with moderate to severe pemphigus, a rare autoimmune disease that causes blistering of the skin and mucous membranes. It is also set for a phase III study to begin later in 2020 in immune thrombocytopenia, which causes a high risk for bleeding events. Rilzabrutinib is also in a phase II for IgG4-related diseases involving chronic inflammation, immune cell infiltration and organ fibrosis.

Principia also brings Sanofi PRN-473, a topical BTK inhibitor, which is being developed for immune-mediated diseases.

South San Francisco-based Principia’s stock (NASDAQ:PRNB) jumped more than 9% in early trading Monday.