During nearly a decade of research dedicated to the study of sphingosine signaling pathways, we identified sphingosine-1-phosphate lyase (S1PL) as a drug target for the treatment of autoimmune disorders. S1PL catalyzes the irreversible decomposition of sphingosine-1-phosphate (S1P) by a retro-aldol fragmentation that yields hexadecanaldehyde and phosphoethanolamine. Genetic models demonstrated that mice expressing reduced S1PL activity had decreased numbers of circulating lymphocytes due to altered lymphocyte trafficking, which prevented disease development in multiple models of autoimmune disease. Mechanistic studies of lymphoid tissue following oral administration of 2-acetyl-4(5)-(1(R),2(S),3(R),4-tetrahydroxybutyl)-imidazole (THI) 3 showed a clear relationship between reduced lyase activity, elevated S1P levels, and lower levels of circulating lymphocytes. Our internal medicinal chemistry efforts discovered potent analogues of 3 bearing heterocycles as chemical equivalents of the pendant carbonyl present in the parent structure. Reduction of S1PL activity by oral administration of these analogues recapitulated the phenotype of mice with genetically reduced S1PL expression.

Sphingosine 1-phosphate lyase (S1PL) has been characterized as a novel target for the treatment of autoimmune disorders using genetic and pharmacological methods. Medicinal chemistry efforts targeting S1PL by direct in vivo evaluation of synthetic analogues of 2-acetyl-4(5)-(1(R),2(S),3(R),4-tetrahydroxybutyl)-imidazole (THI, 1) led to the discovery of 2 (LX2931) and 4 (LX2932). The immunological phenotypes observed in S1PL deficient mice were recapitulated by oral administration of 2 or 4. Oral dosing of 2 or 4 yielded a dose-dependent decrease in circulating lymphocyte numbers in multiple species and showed a therapeutic effect in rodent models of rheumatoid arthritis (RA). Phase I clinical trials indicated that 2, the first clinically studied inhibitor of S1PL, produced a dose-dependent and reversible reduction of circulating lymphocytes and was well tolerated at dose levels of up to 180 mg daily. Phase II evaluation of 2 in patients with active rheumatoid arthritis is currently underway.

Enantioselective syntheses of the alkaloids (−)-aurantioclavine, (+)-amurensinine, (−)-lobeline, and (−)-and (+)-sedamine are described. The syntheses demonstrate the effectiveness of the Pd-catalyzed asymmetric oxidation of secondary alcohols in diverse contexts and the ability of this methodology to set the absolute configuration of multiple stereocenters in a single operation. The utility of an aryne C-C insertion reaction in accessing complex polycyclic frameworks is also described.

SHP2 is a nonreceptor protein tyrosine phosphatase within the mitogen-activated protein kinase (MAPK) pathway controlling cell growth, differentiation, and oncogenic transformation. SHP2 also participates in the programed cell death pathway (PD-1/PD-L1) governing immune surveillance. Small-molecule inhibition of SHP2 has been widely investigated, including in our previous reports describing SHP099 (2), which binds to a tunnel-like allosteric binding site. To broaden our approach to allosteric inhibition of SHP2, we conducted additional hit finding, evaluation, and structure-based scaffold morphing. These studies, reported here in the first of two papers, led to the identification of multiple 5,6-fused bicyclic scaffolds that bind to the same allosteric tunnel as 2. We demonstrate the structural diversity permitted by the tunnel pharmacophore and culminated in the identification of pyrazolopyrimidinones (e.g., SHP389, 1) that modulate MAPK signaling in vivo. These studies also served as the basis for further scaffold morphing and optimization, detailed in the following manuscript.

Protein tyrosine phosphatase SHP2 is an oncoprotein associated with cancer as well as a potential immune modulator because of its role in the programmed cell death PD-L1/PD-1 pathway. In the preceding manuscript, we described the optimization of a fused, bicyclic screening hit for potency, selectivity, and physicochemical properties in order to further expand the chemical diversity of allosteric SHP2 inhibitors. In this manuscript, we describe the further expansion of our approach, morphing the fused, bicyclic system into a novel monocyclic pyrimidinone scaffold through our understanding of SAR and use of structure-based design. These studies led to the identification of SHP394 (1), an orally efficacious inhibitor of SHP2, with high lipophilic efficiency, improved potency, and enhanced pharmacokinetic properties. We also report other pyrimidinone analogues with favorable pharmacokinetic and potency profiles. Overall, this work improves upon our previously described allosteric inhibitors and exemplifies and extends the range of permissible chemical templates that inhibit SHP2 via the allosteric mechanism.