William F. Westlin

Discovery of a Mutant-Selective Covalent Inhibitor of EGFR that Overcomes T790M-Mediated Resistance in NSCLC

UNLABELLED Patients with non-small cell lung cancer (NSCLC) with activating EGF receptor (EGFR) mutations initially respond to first-generation reversible EGFR tyrosine kinase inhibitors. However, clinical efficacy is limited by acquired resistance, frequently driven by the EGFR(T790M) mutation. CO-1686 is a novel, irreversible, and orally delivered kinase inhibitor that specifically targets the mutant forms of EGFR, including T790M, while exhibiting minimal activity toward the wild-type (WT) receptor. Oral administration of CO-1686 as single agent induces tumor regression in EGFR-mutated NSCLC tumor xenograft and transgenic models. Minimal activity of CO-1686 against the WT EGFR receptor was observed. In NSCLC cells with acquired resistance to CO-1686 in vitro, there was no evidence of additional mutations or amplification of the EGFR gene, but resistant cells exhibited signs of epithelial-mesenchymal transition and demonstrated increased sensitivity to AKT inhibitors. These results suggest that CO-1686 may offer a novel therapeutic option for patients with mutant EGFR NSCLC. SIGNIFICANCE We report the preclinical development of a novel covalent inhibitor, CO-1686, that irreversibly and selectively inhibits mutant EGFR, in particular the T790M drug-resistance mutation, in NSCLC models. CO-1686 is the fi rst drug of its class in clinical development for the treatment of T790M-positive NSCLC, potentially offering potent inhibition of mutant EGFR while avoiding the on-target toxicity observed with inhibition of the WT EGFR.

Inhibition of Btk with CC-292 Provides Early Pharmacodynamic Assessment of Activity in Mice and Humans

Targeted therapies that suppress B cell receptor (BCR) signaling have emerged as promising agents in autoimmune disease and B cell malignancies. Bruton’s tyrosine kinase (Btk) plays a crucial role in B cell development and activation through the BCR signaling pathway and represents a new target for diseases characterized by inappropriate B cell activity. N-(3-(5-fluoro-2-(4-(2-methoxyethoxy)phenylamino)pyrimidin-4-ylamino)phenyl)acrylamide (CC-292) is a highly selective, covalent Btk inhibitor and a sensitive and quantitative assay that measures CC-292-Btk engagement has been developed. This translational pharmacodynamic assay has accompanied CC-292 through each step of drug discovery and development. These studies demonstrate the quantity of Btk bound by CC-292 correlates with the efficacy of CC-292 in vitro and in the collagen-induced arthritis model of autoimmune disease. Recently, CC-292 has entered human clinical trials with a trial design that has provided rapid insight into safety, pharmacokinetics, and pharmacodynamics. This first-in-human healthy volunteer trial has demonstrated that a single oral dose of 2 mg/kg CC-292 consistently engaged all circulating Btk protein and provides the basis for rational dose selection in future clinical trials. This targeted covalent drug design approach has enabled the discovery and early clinical development of CC-292 and has provided support for Btk as a valuable drug target for B-cell mediated disorders.

Methionine aminopeptidases type I and type II are essential to control cell proliferation.

The dependence of cell growth on methionine aminopeptidase (MetAP) function in bacteria and yeast is firmly established. Here we report experimental evidence that the control of cell proliferation in mammalian cells is directly linked and strictly dependent on the activity of both MetAP‐1 and MetAP‐2. The targeted downregulation of either methionine aminopeptidase MetAP‐1 or MetAP‐2 protein expression by small interfering RNA (siRNA) significantly inhibited the proliferation of human umbilical vein endothelial cells (HUVEC) (70%–80%), while A549 human lung carcinoma cell proliferation was less inhibited (20%–30%). The cellular levels of MetAP‐2 enzyme were measured after MetAP‐2 siRNA treatment and found to decrease over time from 4 to 96 h, while rapid and complete depletion of MetAP‐2 enzyme activity was observed after 4 h treatment with two pharmacological inhibitors of MetAP‐2, PPI‐2458 and fumagillin. When HUVEC and A549 cells were treated simultaneously with MetAP‐2 siRNA and PPI‐2458, or fumagillin, which irreversibly inhibit MetAP‐2 enzyme activity, no additive effect on maximum growth inhibition was observed. This strongly suggests that MetAP‐2 is the single critical cellular enzyme affected by either MetAP‐2 targeting approach. Most strikingly, despite their significantly different sensitivity to growth inhibition after targeting of either MetAP‐1 or MetAP‐2, HUVEC, and A549 cells, which were made functionally deficient in both MetAP‐1 and MetAP‐2 were completely or almost completely inhibited in their growth, respectively. This closely resembled the observed growth inhibition in genetically double‐deficient map1map2 yeast strains. These results suggest that MetAP‐1 and MetAP‐2 have essential functions in the control of mammalian cell proliferation and that MetAP‐dependent growth control is evolutionarily highly conserved.

In vitro and In vivo Characterization of Irreversible Mutant-Selective EGFR Inhibitors that are Wild-type Sparing

Patients with non–small cell lung carcinoma (NSCLC) with activating mutations in epidermal growth factor receptor (EGFR) initially respond well to the EGFR inhibitors erlotinib and gefitinib. However, all patients relapse because of the emergence of drug-resistant mutations, with T790M mutations accounting for approximately 60% of all resistance. Second-generation irreversible EGFR inhibitors are effective against T790M mutations in vitro, but retain affinity for wild-type EGFR (EGFRWT). These inhibitors have not provided compelling clinical benefit in T790M-positive patients, apparently because of dose-limiting toxicities associated with inhibition of EGFRWT. Thus, there is an urgent clinical need for therapeutics that overcome T790M drug resistance while sparing EGFRWT. Here, we describe a lead optimization program that led to the discovery of four potent irreversible 2,4-diaminopyrimidine compounds that are EGFR mutant (EGFRmut) selective and have been designed to have low affinity for EGFRWT. Pharmacokinetic and pharmacodynamic studies in H1975 tumor–bearing mice showed that exposure was dose proportional resulting in dose-dependent EGFR modulation. Importantly, evaluation of normal lung tissue from the same animals showed no inhibition of EGFRWT. Of all the compounds tested, compound 3 displayed the best efficacy in EGFRL858R/T790M-driven tumors. Compound 3, now renamed CO-1686, is currently in a phase I/II clinical trial in patients with EGFRmut-advanced NSCLC that have received prior EGFR-directed therapy. Mol Cancer Ther; 13(6); 1468–79. ©2014 AACR.

A Novel Methionine Aminopeptidase-2 Inhibitor, PPI-2458, Inhibits Non–Hodgkin's Lymphoma Cell Proliferation In vitro and In vivo

Purpose: Fumagillin and related compounds have potent antiproliferative activity through inhibition of methionine aminopeptidase-2 (MetAP-2). It has recently been reported that MetAP-2 is highly expressed in germinal center B cells and germinal center–derived non–Hodgkins lymphomas (NHL), suggesting an important role for MetAP-2 in proliferating B cells. Therefore, we determined the importance of MetAP-2 in normal and transformed germinal center B cells by evaluating the effects of MetAP-2 inhibition on the form and function of germinal centers and germinal center–derived NHL cells. Experimental Design: To examine the activity of PPI-2458 on germinal center morphology, spleen sections from cynomolgus monkeys treated with oral PPI-2458 were analyzed. Antiproliferative activity of PPI-2458 was assessed on germinal center–derived NHL lines in culture. A MetAP-2 pharmacodynamic assay was used to determine cellular MetAP-2 inhibition following PPI-2458 treatment. Finally, inhibition of MetAP-2 and proliferation by PPI-2458 was examined in the human SR NHL line in culture and in implanted xenografts. Results: Oral PPI-2458 caused a reduction in germinal center size and number in lymphoid tissues from treated animals. PPI-2458 potently inhibited growth (GI50 = 0.2-1.9 nmol/L) of several NHL lines in a manner that correlated with MetAP-2 inhibition. Moreover, orally administered PPI-2458 significantly inhibited SR tumor growth, which correlated with inhibition of tumor MetAP-2 (>85% at 100 mg/kg) in mice. Conclusions: These results show the potent antiproliferative activity of PPI-2458 on NHL lines in vitro and oral antitumor activity in vivo and suggest the therapeutic potential of PPI-2458 as a novel agent for treatment of NHL should be evaluated in the clinical setting.

Superiority of a novel EGFR targeted covalent inhibitor over its reversible counterpart in overcoming drug resistance

Recently, the importance of targeted covalent inhibitors in addressing potency, selectivity and drug resistance has become of great interest, especially in the area of non-small cell lung cancer (NSCLC). Although several covalent EGFR TKIs that are advancing in NSCLC clinical development are active against mutations which are refractory to the reversible TKI drugs Tarceva and Iressa, limited chemical diversity has been explored; all of the irreversible and reversible clinical compounds share the same quinazoline scaffold. We describe the design of a novel pyrimidine-based irreversible inhibitor of EGFR (CNX17) which is active against both the WT EGFR as well as the resistance mutation L858R/T790M in biochemical assays. The inhibitor is also a potent inhibitor of EGFR signaling, including the L858R/T790M resistance mutation in cells (H1975 cell line, EC50 441 nM). Importantly, it also potently inhibits proliferation in both HCC827 (EGFRΔ746–750 EC50 < 5 nM) and H1975 (EC50 134 nM). This novel chemical scaffold may be an important addition to the armamentarium in overcoming drug resistance to current EGFR therapies.

Synthesis and evaluation of arylalkoxy- and biarylalkoxy-phenylamide and phenylimidazoles as potent and selective sphingosine-1-phosphate receptor subtype-1 agonists.

In pursuit of potent and selective sphingosine-1-phosphate receptor agonists, we have utilized previously reported phenylamide and phenylimidazole scaffolds to explore extensive side-chain modifications to generate new molecular entities. A number of designed molecules demonstrate good selectivity and excellent in vitro and in vivo potency in both mouse and rat models. Oral administration of the lead molecule 11c (PPI-4667) demonstrated potent and dose-responsive lymphopenia.

Metabolites of PPI-2458, a Selective, Irreversible Inhibitor of Methionine Aminopeptidase-2: Structure Determination and In Vivo Activity

The natural product fumagillin exhibits potent antiproliferative and antiangiogenic properties. The semisynthetic analog PPI-2458, [(3R,4S,5S,6R)-5-methoxy-4-[(2R,3R)-2-methyl-3-(3-methylbut-2-enyl)oxiran-2-yl]-1-oxaspiro[2.5]octan-6-yl] N-[(2R)-1-amino-3-methyl-1-oxobutan-2-yl]carbamate, demonstrates rapid inactivation of its molecular target, methionine aminopeptidase-2 (MetAP2), and good efficacy in several rodent models of cancer and inflammation with oral dosing despite low apparent oral bioavailability. To probe the basis of its in vivo efficacy, the metabolism of PPI-2458 was studied in detail. Reaction phenotyping identified CYP3A4/5 as the major source of metabolism in humans. Six metabolites were isolated from liver microsomes and characterized by mass spectrometry and nuclear resonance spectroscopy, and their structures were confirmed by chemical synthesis. The synthetic metabolites showed correlated inhibition of MetAP2 enzymatic activity and vascular endothelial cell growth. In an ex vivo experiment, MetAP2 inhibition in white blood cells, thymus, and lymph nodes in rats after single dosing with PPI-2458 and the isolated metabolites was found to correlate with the in vitro activity of the individual species. In a phase 1 clinical study, PPI-2458 was administered to patients with non-Hodgkin lymphoma. At 15 mg administered orally every other day, MetAP2 in whole blood was 80% inactivated for up to 48 hours, although the exposure of the parent compound was only ∼10% that of the summed cytochrome P450 metabolites. Taken together, the data confirm the participation of active metabolites in the in vivo efficacy of PPI-2458. The structures define a metabolic pathway for PPI-2458 that is distinct from that of TNP-470 ([(3R,4S,5S,6R)-5-methoxy-4-[(2R,3R)-2-methyl-3-(3-methylbut-2-enyl)oxiran-2-yl]-1-oxaspiro[2.5]octan-6-yl] N-(2-chloroacetyl)carbamate). The high level of MetAP2 inhibition achieved in vivo supports the value of fumagillin-derived therapeutics for angiogenic diseases.