Bicyclic Ligand-Biased Agonists of S1P 1 : Exploring Side Chain Modifications to Modulate the PK, PD, and Safety Profiles.

Sphingosine-1-phosphate (S1P) binds to a family of sphingosine-1-phosphate G-protein-coupled receptors (S1P _1-5 ). The interaction of S1P with these S1P receptors has a fundamental role in many physiological processes in the vascular and immune systems. Agonist-induced functional antagonism of S1P ₁ has been shown to result in lymphopenia. As a result, agonists of this type hold promise as therapeutics for autoimmune disorders. The previously disclosed differentiated S1P ₁ modulator BMS-986104 ( 1 ) exhibited improved preclinical cardiovascular and pulmonary safety profiles as compared to earlier full agonists of S1P ₁ ; however, it demonstrated a long pharmacokinetic half-life ( T _1/2 18 days) in the clinic and limited formation of the desired active phosphate metabolite. Optimization of this series through incorporation of olefins, ethers, thioethers, and glycols into the alkyl side chain afforded an opportunity to reduce the projected human T _1/2 and improve the formation of the active phosphate metabolite while maintaining efficacy as well as the improved safety profile. These efforts led to the discovery of 12 and 24 , each of which are highly potent, biased agonists of S1P ₁ . These compounds not only exhibited shorter in vivo T _1/2 in multiple species but are also projected to have significantly shorter T _1/2 values in humans when compared to our first clinical candidate. In models of arthritis, treatment with 12 and 24 demonstrated robust efficacy.