Phase I study of PF-04691502, a small-molecule, oral, dual inhibitor of PI3K and mTOR, in patients with advanced cancer.

PURPOSE: To determine the maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, and preliminary evidence of antitumor activity of the PI3K/mTOR inhibitor PF-04691502, administered orally once daily. METHODS: Escalating doses of PF-04691502 were administered to 23 patients with advanced solid tumors in sequential cohorts across the following dose levels: 2 mg, 4 mg, 8 mg, and 11 mg. 14 additional patients were enrolled in an expansion cohort at the MTD to ensure at least five matched pre- and post-treatment biopsies for biomarkers of PI3K activity. RESULTS: The MTD of PF-04691502 was 8 mg orally once daily. There were three dose-limiting toxicities: one grade 3 fatigue at 8 mg, one grade 3 rash at 11 mg, and one intolerable grade 2 fatigue at 11 mg. Among 37 patients enrolled, treatment-related adverse events included fatigue, decreased appetite, nausea, hyperglycemia, rash, and vomiting. Across all dose levels, average steady-state plasma PF-04691502 concentrations approximated or exceeded the target concentration of 16.2 ng/mL required for ≥75 % tumor growth inhibition in preclinical models. PF-04691502 resulted in increased mean fasting serum glucose, insulin, and c-peptide levels, and produced partial blockade of PI3K signalling in five paired tumor biopsies, as demonstrated by reductions in phosphorylated Akt, FKHR/FKHRL1, and STAT3. No objective anti-tumor responses were observed. CONCLUSIONS: Daily oral administration of PF-04691502 was tolerable at 8 mg orally once daily, with a safety profile similar to other PI3K/mTOR inhibitors. PF-04691502 demonstrated PI3K pathway inhibition by changing glucose homeostasis, and by decreasing phosphorylation of downstream molecules in tumor tissue.

A Phase I, Randomized, Multi-Dose Study to Evaluate the Enteric Selectivity and Safety of JAK Inhibitor, Lorpucitinib, in Healthy Participants.

Janus kinase (JAK) signaling has been implicated in human inflammatory diseases, including psoriasis, rheumatoid arthritis, and inflammatory bowel disease. Lorpucitinib (JNJ-64251330) is an oral, small molecule, pan-JAK inhibitor. Unlike systemic JAK antagonists, lorpucitinib was found to have enteric (gut)-selective properties, providing possible applications in diseases of the human gastrointestinal tract. Here, lorpucitinib was evaluated in a phase I, two-part, dosing study (NCT04552197) to assess pharmacokinetics, pharmacodynamic biomarkers, and safety in healthy participants. In part 1, 24 participants were randomized to 1 of 4 treatment arms receiving either lorpucitinib (30 mg daily, 30 mg every 12 hours (q12h), or 75 mg q12h) or tofacitinib (5 mg q12h) for 5 days. Part 2 was a food-effect study in which 12 participants received a single 75-mg dose of lorpucitinib under either fasting or fed conditions. In part 1, plasma and gut tissue concentrations of lorpucitinib showed approximately dose-proportional increases. At all doses, lorpucitinib concentrations were significantly higher (392- to 1928-fold) in the gut mucosal biopsies vs. the corresponding plasma samples, demonstrating high enteric selectivity and significantly exceeding both the tissue concentrations (> 200-fold) and tissue/plasma ratios observed with tofacitinib. JAK inhibition in biopsies was confirmed via reduction in pSTAT-3 levels. In part 2, lorpucitinib plasma concentrations were detectable but at low levels, with no statistical differences in PK parameters between the fed and fasted groups. Lorpucitinib was safe and well-tolerated, and the data may be useful in designing studies to evaluate lorpucitinib in patients with JAK/STAT-driven gastrointestinal diseases.

Discovery and synthesis of novel 4-aminopyrrolopyrimidine Tie-2 kinase inhibitors for the treatment of solid tumors.

The synthesis and biological evaluation of novel Tie-2 kinase inhibitors are presented. Based on the pyrrolopyrimidine chemotype, several new series are described, including the benzimidazole series by linking a benzimidazole to the C5-position of the 4-amino-pyrrolopyrimidine core and the ketophenyl series synthesized by incorporating a ketophenyl group to the C5-position. Medicinal chemistry efforts led to potent Tie-2 inhibitors. Compound 15, a ketophenyl pyrrolopyrimidine urea analog with improved physicochemical properties, demonstrated favorable in vitro attributes as well as dose responsive and robust oral tumor growth inhibition in animal models.

Synthesis and structure based optimization of novel Akt inhibitors.

Based on a high throughput screening hit, pyrrolopyrimidine inhibitors of the Akt kinase are explored. X-ray co-crystal structures of two lead series results in the understanding of key binding interactions, the design of new lead series, and enhanced potency. The syntheses of these series and their biological activities are described. Spiroindoline 13j is found to have an Akt1 kinase IC(50) of 2.4+/-0.6 nM, Akt cell potency of 50+/-19 nM, and provides 68% inhibition of tumor growth in a mouse xenograft model (50 mg/kg, qd, po).

The Hedgehog signaling pathway as a target for anticancer drug discovery.

The Hedgehog (Hh) signaling pathway directs the development of multiple tissues during embryonic development, and contributes to tissue homeostasis in adults. Deficient Hh signaling results in defective embryogenesis; conversely, excessive Hh signaling is associated with an inherited cancer predisposition syndrome (Gorlin Syndrome), and a growing list of sporadic human cancers. It is now clear that multiple components of "The Hh Pathway" can be altered in tumors. The Hhs are morphogens that signal through effectors that are largely unprecedented in drug discovery, with many key concepts derived from studies in Drosophila melanogaster. However, studies in tumor cell lines have recently identified targets that can be exploited for the discovery of human Hh antagonists, with additional targets likely to emerge as the human pathway is further defined. Here, we review basic aspects of Hh signal transduction, with an emphasis on molecular targets for drug discovery. The use of first-generation Hh antagonists such as cyclopamine will also be discussed; such agents remain invaluable in ongoing efforts to validate drug discovery assays and survey tumor lines for Hh dependence. The various types and frequencies of Hh signaling defects in different human tumors will also be reviewed, as will the status of medicinal chemistry efforts to discover novel Hh antagonists. In section VI, we review assays from the literature that could be utilized to discover new Hh antagonists for the treatment of cancer.

First-in-Human Study of PF-05212384 (PKI-587), a Small-Molecule, Intravenous, Dual Inhibitor of PI3K and mTOR in Patients with Advanced Cancer.

PURPOSE: To evaluate safety (primary endpoint), tolerability, pharmacokinetics, pharmacodynamic profile, and preliminary activity of the intravenous, pan-class I isoform PI3K/mTOR inhibitor PF-05212384 in patients with advanced solid tumors. EXPERIMENTAL DESIGN: Part 1 of this open-label phase I study was designed to estimate the maximum-tolerated dose (MTD) in patients with nonselected solid tumors, using a modified continual reassessment method to guide dose escalation. Objectives of part 2 were MTD confirmation and assessment of preliminary activity in patients with selected tumor types and PI3K pathway dysregulation. RESULTS: Seventy-seven of the 78 enrolled patients received treatment. The MTD for PF-05212384, administered intravenously once weekly, was estimated to be 154 mg. The most common treatment-related adverse events (AE) were mucosal inflammation/stomatitis (58.4%), nausea (42.9%), hyperglycemia (26%), decreased appetite (24.7%), fatigue (24.7%), and vomiting (24.7%). The majority of patients treated at the MTD experienced only grade 1 treatment-related AEs. Grade 3 treatment-related AEs occurred in 23.8% of patients at the MTD. No treatment-related grade 4-5 AEs were reported at any dose level. Antitumor activity was noted in this heavily pretreated patient population, with two partial responses (PR) and an unconfirmed PR. Eight patients had long-lasting stable disease (>6 months). Pharmacokinetic analyses showed a biphasic concentration-time profile for PF-05212384 (half-life, 30-37 hours after multiple dosing). PF-05212384 inhibited downstream effectors of the PI3K pathway in paired tumor biopsies. CONCLUSIONS: These findings demonstrate the manageable safety profile and antitumor activity of the PI3K/mTOR inhibitor PF-05212384, supporting further clinical development for patients with advanced solid malignancies.

Discovery of PF-04449913, a Potent and Orally Bioavailable Inhibitor of Smoothened.

Inhibitors of the Hedgehog signaling pathway have generated a great deal of interest in the oncology area due to the mounting evidence of their potential to provide promising therapeutic options for patients. Herein, we describe the discovery strategy to overcome the issues inherent in lead structure 1 that resulted in the identification of Smoothened inhibitor 1-((2R,4R)-2-(1H-benzo[d]imidazol-2-yl)-1-methylpiperidin-4-yl)-3-(4-cyanophenyl)urea (PF-04449913, 26), which has been advanced to human clinical studies.

Biochemical and pharmacological characterization of human c-Met neutralizing monoclonal antibody CE-355621.

The c-Met proto-oncogene is a multifunctional receptor tyrosine kinase that is stimulated by its ligand, hepatocyte growth factor (HGF), to induce cell growth, motility and morphogenesis. Dysregulation of c-Met function, through mutational activation or overexpression, has been observed in many types of cancer and is thought to contribute to tumor growth and metastasis by affecting mitogenesis, invasion, and angiogenesis. We identified human monoclonal antibodies that bind to the extracellular domain of c-Met and inhibit tumor growth by interfering with ligand-dependent c-Met activation. We identified antibodies representing four independent epitope classes that inhibited both ligand binding and ligand-dependent activation of c-Met in A549 cells. In cells, the antibodies antagonized c-Met function by blocking receptor activation and by subsequently inducing downregulation of the receptor, translating to phenotypic effects in soft agar growth and tubular morphogenesis assays. Further characterization of the antibodies in vivo revealed significant inhibition of c-Met activity (≥ 80% lasting for 72-96 h) in excised tumors corresponded to tumor growth inhibition in multiple xenograft tumor models. Several of the antibodies identified inhibited the growth of tumors engineered to overexpress human HGF and human c-Met (S114 NIH 3T3) when grown subcutaneously in athymic mice. Furthermore, lead candidate antibody CE-355621 inhibited the growth of U87MG human glioblastoma and GTL-16 gastric xenografts by up to 98%. The findings support published pre-clinical and clinical data indicating that targeting c-Met with human monoclonal antibodies is a promising therapeutic approach for the treatment of cancer.

Design of selective, ATP-competitive inhibitors of Akt.

This paper describes the design and synthesis of novel, ATP-competitive Akt inhibitors from an elaborated 3-aminopyrrolidine scaffold. Key findings include the discovery of an initial lead that was modestly selective and medicinal chemistry optimization of that lead to provide more selective analogues. Analysis of the data suggested that highly lipophilic analogues would likely suffer from poor overall properties. Central to the discussion is the concept of optimization of lipophilic efficiency and the ability to balance overall druglike propeties with the careful control of lipophilicity in the lead series. Discovery of the nonracemic amide series and subsequent modification produced an advanced analogue that performed well in advanced preclinical assays, including xenograft tumor growth inhibition studies, and this analogue was nominated for clinical development.