VCP (also known as p97 or Cdc48p in yeast) is an AAA(+) ATPase regulating endoplasmic reticulum-associated degradation. After high-throughput screening, we developed compounds that inhibit VCP via different mechanisms, including covalent modification of an active site cysteine and a new allosteric mechanism. Using photoaffinity labeling, structural analysis and mutagenesis, we mapped the binding site of allosteric inhibitors to a region spanning the D1 and D2 domains of adjacent protomers encompassing elements important for nucleotide-state sensing and ATP hydrolysis. These compounds induced an increased affinity for nucleotides. Interference with nucleotide turnover in individual subunits and distortion of interprotomer communication cooperated to impair VCP enzymatic activity. Chemical expansion of this allosteric class identified NMS-873, the most potent and specific VCP inhibitor described to date, which activated the unfolded protein response, interfered with autophagy and induced cancer cell death. The consistent pattern of cancer cell killing by covalent and allosteric inhibitors provided critical validation of VCP as a cancer target.

Prodigiosins (Ps) represent a family of naturally occurring red pigments characterized by a common pyrrolylpyrromethene skeleton. Some members of this family have been shown to possess interesting immunosuppressive properties exerted with a novel mechanism of action, different from that of currently used drugs. In fact, Ps inhibit phosphorylation and activation of JAK-3, a cytoplasmic tyrosine kinase associated with a cell surface receptor component called common gamma-chain, which is exclusive of all IL-2 cytokine family receptors. Blocking common gamma-chain transduction activity results in a potent and specific immunosuppressive activity. With respect to the interesting and unexploited immunomodulating properties of this family of compounds we initiated a medicinal chemistry program aimed at finding novel prodigiosin derivatives with improved immunosuppressive activity and lower toxicity. Utilizing an unprecedented and flexible way of assembling the prodigiosin frame, a number of new derivatives have been prepared and tested leading to the choice of 4-benzyloxy-5-[(5-undecyl-2H-pyrrol-2-ylidene)methyl]-2, 2'-bi-1H-pyrrole (PNU-156804, 16) as a lead immunosuppressant.

A group of potential alkylating agents have been synthesized that are structurally related to the oligopeptide antiviral antibiotic distamycin. All derivatives form complexes with native calf-thymus DNA but compounds 2, 3, and 6 give rise to covalent adducts. Cytostatic activity against both human and murine tumor cell lines in vitro is displayed by the new compounds. Compounds 3 and 4 are active on melphalan-resistant L1210 leukemia in mice.

Valosine containing protein (VCP), also known as p97, is a member of AAA ATPase family that is involved in several biological processes and plays a central role in the ubiquitin-mediated degradation of misfolded proteins. VCP is an ubiquitously expressed, highly abundant protein and has been found overexpressed in many tumor types, sometimes associated with poor prognosis. In this respect, VCP has recently received a great deal of attention as a potential new target for cancer therapy. In this paper, the discovery and structure-activity relationships of alkylsulfanyl-1,2,4-triazoles, a new class of potent, allosteric VCP inhibitors, are described. Medicinal chemistry manipulation of compound 1, identified via HTS, led to the discovery of potent and selective inhibitors with submicromolar activity in cells and clear mechanism of action at consistent doses. This represents a first step toward a new class of potential anticancer agents.

The discovery of a novel class of inhibitors of cyclin dependent kinases (CDKs) is described. Starting from compound 1, showing good potency as inhibitor of CDKs but being poorly selective against a panel of serine-threonine and tyrosine kinases, new analogues were synthesized. Enhancement in selectivity, antiproliferative activity against A2780 human ovarian carcinoma cells, and optimization of the physical properties and pharmacokinetic profile led to the identification of highly potent and orally available compounds. Compound 28 (PHA-848125), which in the preclinical xenograft A2780 human ovarian carcinoma model showed good efficacy and was well tolerated upon repeated daily treatments, was identified as a drug candidate for further development. Compound 28 is currently undergoing phase I and phase II clinical trials.