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 26), which has been advanced to human clinical studies.

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 non-selected 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 (AEs) 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.

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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.

fms genes encoding either wild-type or constitutively activated colony-stimulating factor 1 receptors (CSF-1R) were introduced by retroviral infection into long-term mouse lymphoid cultures. Four early pre-B-cell lines transformed by the feline v-fms oncogene underwent spontaneous and irreversible differentiation to macrophages when transferred from RPMI 1640 to Iscove modified Dulbecco medium. Expression of wild-type human CSF-1R in early pre-B cells conferred no proliferative advantage unless human CSF-1 was added to the culture medium. A clonal, factor-dependent early pre-B-cell line (D1F9), selected for continuous growth on NIH 3T3 cell feeder layers producing human CSF-1, could be maintained in RPMI 1640 medium containing interleukin-7 (IL-7) but also differentiated to macrophages when grown in Iscove modified Dulbecco medium containing human CSF-1. The macrophages retained parental immunoglobulin gene rearrangements and proviral insertions, lost B-cell antigens, expressed butyrate esterase and MAC-1, were actively phagocytic, and no longer survived in IL-7. Unlike factor-independent v-fms transformants, the irreversible commitment of D1F9 cells to differentiate in the macrophage lineage could be suppressed by IL-7, depended on human (but not mouse) CSF-1, and was inhibited by an antibody to human CSF-1R. Signals mediated by transduced CSF-1R can therefore play a deterministic role in cell differentiation.