Parsaclisib Is a Next-Generation Phosphoinositide 3-Kinase Inhibitor with Reduced Hepatotoxicity and Potent Antitumor and Immunomodulatory Activities in Models of B-Cell Malignancy.

The clinical use of first-generation phosphoinositide 3-kinase (PI3K) inhibitors in B-cell malignancies is hampered by hepatotoxicity, requiring dose reduction, treatment interruption, and/or discontinuation of therapy. In addition, potential molecular mechanisms by which resistance to this class of drugs occurs have not been investigated. Parsaclisib (INCB050465) is a potent and selective next-generation PI3K inhibitor that differs in structure from first-generation PI3K inhibitors and has shown encouraging anti-B-cell tumor activity and reduced hepatotoxicity in phase 1/2 clinical studies.

INCB050465 (Parsaclisib), a Novel Next-Generation Inhibitor of Phosphoinositide 3-Kinase Delta (PI3Kδ).

A medicinal chemistry effort focused on identifying a structurally diverse candidate for phosphoinositide 3-kinase delta (PI3Kδ) led to the discovery of clinical candidate INCB050465 (, parsaclisib). The unique structure of contains a pyrazolopyrimidine hinge-binder in place of a purine motif that is present in other PI3Kδ inhibitors, such as idelalisib (), duvelisib (), and INCB040093 (, dezapelisib). Parsaclisib () is a potent and highly selective inhibitor of PI3Kδ with drug-like ADME properties that exhibited an excellent in vivo profile as demonstrated through pharmacokinetic studies in rats, dogs, and monkeys and through pharmacodynamic and efficacy studies in a mouse Pfeiffer xenograft model.

INCB24360 (Epacadostat), a Highly Potent and Selective Indoleamine-2,3-dioxygenase 1 (IDO1) Inhibitor for Immuno-oncology.

A data-centric medicinal chemistry approach led to the invention of a potent and selective IDO1 inhibitor , INCB24360 (epacadostat). The molecular structure of INCB24360 contains several previously unknown or underutilized functional groups in drug substances, including a hydroxyamidine, furazan, bromide, and sulfamide. These moieties taken together in a single structure afford a compound that falls outside of "drug-like" space.

Discovery of potent competitive inhibitors of indoleamine 2,3-dioxygenase with in vivo pharmacodynamic activity and efficacy in a mouse melanoma model.

A hydroxyamidine chemotype has been discovered as a key pharmacophore in novel inhibitors of indoleamine 2,3-dioxygenase (IDO). Optimization led to the identification of 5l, which is a potent (HeLa IC(50) = 19 nM) competitive inhibitor of IDO. Testing of 5l in mice demonstrated pharmacodynamic inhibition of IDO, as measured by decreased kynurenine levels (>50%) in plasma and dose dependent efficacy in mice bearing GM-CSF-secreting B16 melanoma tumors.

Structural insights into the design of nonpeptidic isothiazolidinone-containing inhibitors of protein-tyrosine phosphatase 1B.

Structural analyses of the protein-tyrosine phosphatase 1B (PTP1B) active site and inhibitor complexes have aided in optimization of a peptide inhibitor containing the novel (S)-isothiazolidinone (IZD) phosphonate mimetic. Potency and permeability were simultaneously improved by replacing the polar peptidic backbone of the inhibitor with nonpeptidic moieties. The C-terminal primary amide was replaced with a benzimidazole ring, which hydrogen bonds to the carboxylate of Asp(48), and the N terminus of the peptide was replaced with an aryl sulfonamide, which hydrogen bonds to Asp(48) and the backbone NH of Arg(47) via a water molecule.

Structural basis for inhibition of protein-tyrosine phosphatase 1B by isothiazolidinone heterocyclic phosphonate mimetics.

Crystal structures of protein-tyrosine phosphatase 1B in complex with compounds bearing a novel isothiazolidinone (IZD) heterocyclic phosphonate mimetic reveal that the heterocycle is highly complementary to the catalytic pocket of the protein. The heterocycle participates in an extensive network of hydrogen bonds with the backbone of the phosphate-binding loop, Phe(182) of the flap, and the side chain of Arg(221). When substituted with a phenol, the small inhibitor induces the closed conformation of the protein and displaces all waters in the catalytic pocket.

Isothiazolidinone heterocycles as inhibitors of protein tyrosine phosphatases: synthesis and structure-activity relationships of a peptide scaffold.

The structure-based design and discovery of the isothiazolidinone (IZD) heterocycle as a mimic of phosphotyrosine (pTyr) has led to the identification of novel IZD-containing inhibitors of protein tyrosine phosphatase 1B (PTP1B). The structure-activity relationships (SARs) of peptidic IZD-containing inhibitors of PTP1B are described along with a novel synthesis of the aryl-IZD fragments via a Suzuki coupling. The SAR revealed the saturated IZD heterocycle (42) is the most potent heterocyclic pTyr mimetic compared to the unsaturated IZD (25), the thiadiazolidinone (TDZ) (38), and the regioisomeric unsaturated IZD (31).

Structure-based design and discovery of protein tyrosine phosphatase inhibitors incorporating novel isothiazolidinone heterocyclic phosphotyrosine mimetics.

Structure-based design led to the discovery of novel (S)-isothiazolidinone ((S)-IZD) heterocyclic phosphotyrosine (pTyr) mimetics that when incorporated into dipeptides are exceptionally potent, competitive, and reversible inhibitors of protein tyrosine phosphatase 1B (PTP1B). The crystal structure of PTP1B in complex with our most potent inhibitor 12 revealed that the (S)-IZD heterocycle interacts extensively with the phosphate binding loop precisely as designed in silico. Our data provide strong evidence that the (S)-IZD is the most potent pTyr mimetic reported to date.

Design and synthesis of bicyclic pyrimidinone-based HCV NS3 protease inhibitors.

A series of bicyclic pyrimidinone-based HCV NS3 protease inhibitors was synthesized via selective C8 position functionalization. Substituted phenylamides and phenylureas were preferred in the S2 binding pocket.