Principia's Bruton tyrosine kinase (BTK) inhibitors will boost Sanofi's efforts to build a portfolio of the next generation of treatments for autoimmune diseases, according to the firm. BTK is present in signaling pathways of key innate and adaptative cell types of the immune system. Blocking these proteins can disrupt signaling and stop inflammation and tissue destruction.

The roster includes:

• BTK inhibitor '168, which is in a phase IIb study in patients with multiple sclerosis.
• Rilzabrutinib, which is in a phase III program for patients with moderate to severe pemphigus.
• Prn473 Topical, which is in phase I trials for immune diseases that manifest in the skin.

The programs are designed on Principia's Tailored Covalency platform, which creates reversible covalent and irreversible covalent small molecule inhibitors that are more selective with less off-target effects.

The deal has been approved by both companies' board of directors and is expected to close in the fourth quarter of this year, the two firms said.