Comparative Oncology Assessment of a Novel Inhibitor of Valosin-Containing Protein in Tumor-Bearing Dogs.

Pet dogs with naturally occurring cancers play an important role in studies of cancer biology and drug development. We assessed tolerability, efficacy, and pharmacokinetic/pharmacodynamic relationships with a first-in-class small molecule inhibitor of valosin-containing protein (VCP/p97), CB-5339, administered to 24 tumor-bearing pet dogs. Tumor types assessed included solid malignancies, lymphomas, and multiple myeloma. Through a stepwise dose and schedule escalation schema, we determined the maximum tolerated dose to be 7.5 mg/kg when administered orally on a 4 days on, 3 days off schedule per week for 3 consecutive weeks. Adverse events were minimal and mainly related to the gastrointestinal system. Pharmacokinetic/pharmacodynamic data suggest a relationship between exposure and modulation of targets related to induction of the unfolded protein response, but not to tolerability of the agent. An efficacy signal was detected in 33% (2/6) of dogs with multiple myeloma, consistent with a mechanism of action relating to induction of proteotoxic stress in a tumor type with abundant protein production. Clinical trials of CB-5339 in humans with acute myelogenous leukemia and multiple myeloma are ongoing.

Sulforaphane is Synergistic with CB-5083 and Inhibits Colony Formation of CB-5083-Resistant HCT116 Cells.

Human p97 is a potential drug target in oncology. Mutation-driven drug resistance is an obstacle to the long-term efficacy of targeted therapy. We found that the ATPase activity for one of the CB-5083-resistant p97 mutants was reduced, which also attenuated the degradation of K48 ubiquitinated proteins in cells. To understand how p97 mutant cells with significantly reduced ATPase activity can still grow, we discovered reduced levels of CHOP and NF-κB activation in the p97 mutant cells and these cellular changes can potentially protect HCT116 cells from death due to lowered p97 activity. In addition, the NF-kB inhibitor Sulforaphane reduces proliferation of CB-5083 resistant cells and acts synergistically with CB-5083 to block proliferation of the parental HCT116 cells. The combination of Sulforaphane and CB-5083 may be a useful treatment strategy to combat CB-5083 resistance.

2.3 Å resolution cryo-EM structure of human p97 and mechanism of allosteric inhibition.

p97 is a hexameric AAA+ adenosine triphosphatase (ATPase) that is an attractive target for cancer drug development. We report cryo-electron microscopy (cryo-EM) structures for adenosine diphosphate (ADP)-bound, full-length, hexameric wild-type p97 in the presence and absence of an allosteric inhibitor at resolutions of 2.3 and 2.4 angstroms, respectively. We also report cryo-EM structures (at resolutions of ~3.3, 3.2, and 3.3 angstroms, respectively) for three distinct, coexisting functional states of p97 with occupancies of zero, one, or two molecules of adenosine 5'-O-(3-thiotriphosphate) (ATPγS) per protomer. A large corkscrew-like change in molecular architecture, coupled with upward displacement of the N-terminal domain, is observed only when ATPγS is bound to both the D1 and D2 domains of the protomer. These cryo-EM structures establish the sequence of nucleotide-driven structural changes in p97 at atomic resolution. They also enable elucidation of the binding mode of an allosteric small-molecule inhibitor to p97 and illustrate how inhibitor binding at the interface between the D1 and D2 domains prevents propagation of the conformational changes necessary for p97 function.

Structure based drug design of crizotinib (PF-02341066), a potent and selective dual inhibitor of mesenchymal-epithelial transition factor (c-MET) kinase and anaplastic lymphoma kinase (ALK).

Because of the critical roles of aberrant signaling in cancer, both c-MET and ALK receptor tyrosine kinases are attractive oncology targets for therapeutic intervention. The cocrystal structure of 3 (PHA-665752), bound to c-MET kinase domain, revealed a novel ATP site environment, which served as the target to guide parallel, multiattribute drug design. A novel 2-amino-5-aryl-3-benzyloxypyridine series was created to more effectively make the key interactions achieved with 3. In the novel series, the 2-aminopyridine core allowed a 3-benzyloxy group to reach into the same pocket as the 2,6-dichlorophenyl group of 3 via a more direct vector and thus with a better ligand efficiency (LE). Further optimization of the lead series generated the clinical candidate crizotinib (PF-02341066), which demonstrated potent in vitro and in vivo c-MET kinase and ALK inhibition, effective tumor growth inhibition, and good pharmaceutical properties.

Structure-based design of novel human Pin1 inhibitors (I).

Pin1 is a member of the cis-trans peptidyl-prolyl isomerase family with potential anti-cancer therapeutic value. Here we report structure-based de novo design and optimization of novel Pin1 inhibitors. Without a viable lead from internal screenings, we designed a series of novel Pin1 inhibitors by interrogating and exploring a protein crystal structure of Pin1. The ligand efficiency of the initial concept molecule was optimized with integrated SBDD and parallel chemistry approaches, resulting in a more attractive lead series.

Phase 0 clinical trials: conceptions and misconceptions.

Phase 0 clinical trials, developed in response to the United States Food and Drug Administration (FDA)'s recent exploratory Investigational New Drug (IND) guidance, are intended to expedite the clinical evaluation of new molecular entities. The exploratory IND supports the performance of first-in-human testing of new investigational agents at subtherapeutic doses based on reduced manufacturing and toxicologic requirements, allowing the demonstration of drug-target effects and assessment of pharmacokinetic-pharmacodynamic relationships in humans earlier in clinical development. The objectives of a phase 0 cancer clinical trial are to establish at the very earliest opportunity-before large numbers of patients have been accrued and exposed to potential drug-associated toxicity-whether an agent is modulating its target in a tumor, and consequently whether further clinical development is warranted. We review here the fundamental requirements of clinical studies conducted under an exploratory IND and address some common misconceptions regarding oncologic phase 0 trials.

Structure activity relationships of quinoline-containing c-Met inhibitors.

A series of quinoline-containing c-Met inhibitors were prepared and studied. Chemistry was developed to introduce a pyridyl moiety onto the 2-aryl ring present in a lead molecule which mitigated the potential for quinone formation relative to the original compound. The study also assessed the importance of an acylthiourea moiety present in the lead structure for effective binding to the c-Met protein ATP site.

Cytoreductive antitumor activity of PF-2341066, a novel inhibitor of anaplastic lymphoma kinase and c-Met, in experimental models of anaplastic large-cell lymphoma.

A t(2;5) chromosomal translocation resulting in expression of an oncogenic kinase fusion protein known as nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) has been implicated in the pathogenesis of anaplastic large-cell lymphoma (ALCL). PF-2341066 was recently identified as a p.o. bioavailable, small-molecule inhibitor of the catalytic activity of c-Met kinase and the NPM-ALK fusion protein. PF-2341066 also potently inhibited NPM-ALK phosphorylation in Karpas299 or SU-DHL-1 ALCL cells (mean IC(50) value, 24 nmol/L). In biochemical and cellular screens, PF-2341066 was shown to be selective for c-Met and ALK at pharmacologically relevant concentrations across a panel of >120 diverse kinases. PF-2341066 potently inhibited cell proliferation, which was associated with G(1)-S-phase cell cycle arrest and induction of apoptosis in ALK-positive ALCL cells (IC(50) values, approximately 30 nmol/L) but not ALK-negative lymphoma cells. The induction of apoptosis was confirmed using terminal deoxyribonucleotide transferase-mediated nick-end labeling and Annexin V staining (IC(50) values, 25-50 nmol/L). P.o. administration of PF-2341066 to severe combined immunodeficient-Beige mice bearing Karpas299 ALCL tumor xenografts resulted in dose-dependent antitumor efficacy with complete regression of all tumors at the 100 mg/kg/d dose within 15 days of initial compound administration. A strong correlation was observed between antitumor response and inhibition of NPM-ALK phosphorylation and induction of apoptosis in tumor tissue. In addition, inhibition of key NPM-ALK signaling mediators, including phospholipase C-gamma, signal transducers and activators of transcription 3, extracellular signal-regulated kinases, and Akt by PF-2341066 were observed at concentrations or dose levels, which correlated with inhibition of NPM-ALK phosphorylation and function. Collectively, these data illustrate the potential clinical utility of inhibitors of NPM-ALK in treatment of patients with ALK-positive ALCL.

Identification and characterization of a novel and functional murine Pin1 isoform.

Pin1, a phosphorylation-dependent peptidyl-prolyl cis/trans isomerase (PPIase), regulates the activity of a number of cell cycle regulators, transcription factors, and microtubule-associated tau. Aberrant expression of Pin1 is implicated in carcinogenesis and neurodegenerative diseases. Yet, there are discrepancies regarding its biological significance in different organisms. Pin1 was essential in HeLa cells, while Pin1-deficient mice showed no lethal phenotypes. We here identified a novel murine Pin1 isoform (mPin1L) consisting of the WW domain and the PPIase domain. Murine Pin1L shares 92% sequence identity with the wild-type Pin1 and shows wide tissue distribution with highest levels in mouse testis. The recombinant mPin1L is enzymatically active, but is approximately three times less efficient than Pin1 in catalyzing the cis/trans isomerization. These data suggest that mPin1L may serve as a surrogate for Pin1. The finding provides insights into phenotypic consequences for Pin1-null mice and may facilitate future biological study and pharmacological development in mice.

An orally available small-molecule inhibitor of c-Met, PF-2341066, exhibits cytoreductive antitumor efficacy through antiproliferative and antiangiogenic mechanisms.

The c-Met receptor tyrosine kinase and its ligand, hepatocyte growth factor (HGF), have been implicated in the progression of several human cancers and are attractive therapeutic targets. PF-2341066 was identified as a potent, orally bioavailable, ATP-competitive small-molecule inhibitor of the catalytic activity of c-Met kinase. PF-2341066 was selective for c-Met (and anaplastic lymphoma kinase) compared with a panel of >120 diverse tyrosine and serine-threonine kinases. PF-2341066 potently inhibited c-Met phosphorylation and c-Met-dependent proliferation, migration, or invasion of human tumor cells in vitro (IC(50) values, 5-20 nmol/L). In addition, PF-2341066 potently inhibited HGF-stimulated endothelial cell survival or invasion and serum-stimulated tubulogenesis in vitro, suggesting that this agent also exhibits antiangiogenic properties. PF-2341066 showed efficacy at well-tolerated doses, including marked cytoreductive antitumor activity, in several tumor models that expressed activated c-Met. The antitumor efficacy of PF-2341066 was dose dependent and showed a strong correlation to inhibition of c-Met phosphorylation in vivo. Near-maximal inhibition of c-Met activity for the full dosing interval was necessary to maximize the efficacy of PF-2341066. Additional mechanism-of-action studies showed dose-dependent inhibition of c-Met-dependent signal transduction, tumor cell proliferation (Ki67), induction of apoptosis (caspase-3), and reduction of microvessel density (CD31). These results indicated that the antitumor activity of PF-2341066 may be mediated by direct effects on tumor cell growth or survival as well as antiangiogenic mechanisms. Collectively, these results show the therapeutic potential of targeting c-Met with selective small-molecule inhibitors for the treatment of human cancers.