Donald J. Ogilvie

AZD2171: A Highly Potent, Orally Bioavailable, Vascular Endothelial Growth Factor Receptor-2 Tyrosine Kinase Inhibitor for the Treatment of Cancer

Inhibition of vascular endothelial growth factor-A (VEGF) signaling is a promising therapeutic approach that aims to stabilize the progression of solid malignancies by abrogating tumor-induced angiogenesis. This may be accomplished by inhibiting the kinase activity of VEGF receptor-2 (KDR), which has a key role in mediating VEGF-induced responses. The novel indole-ether quinazoline AZD2171 is a highly potent (IC50 < 1 nmol/L) ATP-competitive inhibitor of recombinant KDR tyrosine kinase in vitro. Concordant with this activity, in human umbilical vein endothelial cells, AZD2171 inhibited VEGF-stimulated proliferation and KDR phosphorylation with IC50 values of 0.4 and 0.5 nmol/L, respectively. In a fibroblast/endothelial cell coculture model of vessel sprouting, AZD2171 also reduced vessel area, length, and branching at subnanomolar concentrations. Once-daily oral administration of AZD2171 ablated experimental (VEGF-induced) angiogenesis in vivo and inhibited endochondral ossification in bone or corpora luteal development in ovary; physiologic processes that are highly dependent upon neovascularization. The growth of established human tumor xenografts (colon, lung, prostate, breast, and ovary) in athymic mice was inhibited dose-dependently by AZD2171, with chronic administration of 1.5 mg per kg per day producing statistically significant inhibition in all models. A histologic analysis of Calu-6 lung tumors treated with AZD2171 revealed a reduction in microvessel density within 52 hours that became progressively greater with the duration of treatment. These changes are indicative of vascular regression within tumors. Collectively, the data obtained with AZD2171 are consistent with potent inhibition of VEGF signaling, angiogenesis, neovascular survival, and tumor growth. AZD2171 is being developed clinically as a once-daily oral therapy for the treatment of cancer.

Preclinical Pharmacology of AZD5363, an Inhibitor of AKT: Pharmacodynamics, Antitumor Activity, and Correlation of Monotherapy Activity with Genetic Background

AKT is a key node in the most frequently deregulated signaling network in human cancer. AZD5363, a novel pyrrolopyrimidine-derived compound, inhibited all AKT isoforms with a potency of 10 nmol/L or less and inhibited phosphorylation of AKT substrates in cells with a potency of approximately 0.3 to 0.8 μmol/L. AZD5363 monotherapy inhibited the proliferation of 41 of 182 solid and hematologic tumor cell lines with a potency of 3 μmol/L or less. Cell lines derived from breast cancers showed the highest frequency of sensitivity. There was a significant relationship between the presence of PIK3CA and/or PTEN mutations and sensitivity to AZD5363 and between RAS mutations and resistance. Oral dosing of AZD5363 to nude mice caused dose- and time-dependent reduction of PRAS40, GSK3β, and S6 phosphorylation in BT474c xenografts (PRAS40 phosphorylation EC50 ∼ 0.1 μmol/L total plasma exposure), reversible increases in blood glucose concentrations, and dose-dependent decreases in 2[18F]fluoro-2-deoxy-d-glucose (18F-FDG) uptake in U87-MG xenografts. Chronic oral dosing of AZD5363 caused dose-dependent growth inhibition of xenografts derived from various tumor types, including HER2+ breast cancer models that are resistant to trastuzumab. AZD5363 also significantly enhanced the antitumor activity of docetaxel, lapatinib, and trastuzumab in breast cancer xenografts. It is concluded that AZD5363 is a potent inhibitor of AKT with pharmacodynamic activity in vivo, has potential to treat a range of solid and hematologic tumors as monotherapy or a combinatorial agent, and has potential for personalized medicine based on the genetic status of PIK3CA, PTEN, and RAS. AZD5363 is currently in phase I clinical trials. Mol Cancer Ther; 11(4); 873–87. ©2012 AACR.

AZD8931, an Equipotent, Reversible Inhibitor of Signaling by Epidermal Growth Factor Receptor, ERBB2 (HER2), and ERBB3: A Unique Agent for Simultaneous ERBB Receptor Blockade in Cancer

Purpose: To test the hypothesis that simultaneous, equipotent inhibition of epidermal growth factor receptor (EGFR; erbB1), erbB2 (human epidermal growth factor receptor 2), and erbB3 receptor signaling, using the novel small-molecule inhibitor AZD8931, will deliver broad antitumor activity in vitro and in vivo. Experimental Design: A range of assays was used to model erbB family receptor signaling in homodimers and heterodimers, including in vitro evaluation of erbB kinase activity, erbB receptor phosphorylation, proliferation in cells, and in vivo testing in a human tumor xenograft panel, with ex vivo evaluation of erbB phosphorylation and downstream biomarkers. Gefitinib and lapatinib were used to compare the pharmacological profile of AZD8931 with other erbB family inhibitors. Results: In vitro, AZD8931 showed equipotent, reversible inhibition of EGFR (IC50, 4 nmol/L), erbB2 (IC50, 3 nmol/L), and erbB3 (IC50, 4 nmol/L) phosphorylation in cells. In proliferation assays, AZD8931 was significantly more potent than gefitinib or lapatinib in specific squamous cell carcinoma of the head and neck and non–small cell lung carcinoma cell lines. In vivo, AZD8931 inhibited xenograft growth in a range of models while significantly affecting EGFR, erbB2, and erbB3 phosphorylation and downstream signaling pathways, apoptosis, and proliferation. Conclusions: AZD8931 has a unique pharmacologic profile providing equipotent inhibition of EGFR, erbB2, and erbB3 signaling and showing greater antitumor activity than agents with a narrower spectrum of erbB receptor inhibition in specific preclinical models. AZD8931 provides the opportunity to investigate whether simultaneous inhibition of erbB receptor signaling could be of utility in the clinic, particularly in the majority of solid tumors that do not overexpress erbB2. Clin Cancer Res; 16(4); 1159–69

Inhibition of Vascular Endothelial Growth Factor-A Signaling Induces Hypertension: Examining the Effect of Cediranib (Recentin; AZD2171) Treatment on Blood Pressure in Rat and the Use of Concomitant Antihypertensive Therapy

Purpose: Inhibition of vascular endothelial growth factor-A (VEGF) signaling is a key therapeutic approach in oncology given the role of VEGF in angiogenesis and vascular permeability in solid tumors. Clinical trials examining VEGF signaling inhibitors commonly report hypertension. We examined the effect of cediranib, a highly potent VEGF signaling inhibitor, on the blood pressure of rats and the ability of standard antihypertensive agents to modulate the consequences of VEGF signaling inhibition. Experimental Design: The ability of cediranib to induce hypertensive changes and the effect of giving antihypertensive therapy were investigated in conscious, unrestrained telemetered rats. Two antihypertensive agents were studied: captopril, an angiotensin-converting enzyme inhibitor, and nifedipine, a dihydropyridine calcium channel blocker. The antitumor activity of cediranib, alone and in combination with nifedipine, was also evaluated in a LoVo human colorectal tumor xenograft model in nude rats. All treatments were given orally. Results: Administration of 0.1 to 1.5 mg/kg/d of cediranib for 4 consecutive days induced a relatively mild hypertensive effect, elevating diastolic blood pressure by 10 to 14 mmHg. Dosing 3 mg/kg/d cediranib for 4 days induced a marked hypertension of 35 to 50 mmHg. Captopril (30 mg/kg, qd) was effective at lowering a 10 mmHg increase in blood pressure but not a 35 to 50 mmHg increase. However, the latter was rapidly reversed by administration of nifedipine (10 mg/kg, bd). Coadministration of nifedipine did not negatively affect the antitumor activity of cediranib (1.5 mg/kg/d). Conclusions: Hypertension is a direct consequence of inhibiting VEGF signaling but can be controlled with appropriately selected, standard antihypertensive medication.

Assessing the Activity of Cediranib, a VEGFR-2/-3 tyrosine kinase inhibitor, against VEGFR-1 and members of the structurally related PDGFR-family

Cediranib is a potent inhibitor of the VEGF receptor (VEGFR)-2 and VEGFR-3 tyrosine kinases. This study assessed the activity of cediranib against the VEGFR-1 tyrosine kinase and the platelet-derived growth factor receptor (PDGFR)-associated kinases c-Kit, PDGFR-α, and PDGFR-β. Cediranib inhibited VEGF-A–stimulated VEGFR-1 activation in AG1-G1-Flt1 cells (IC50 = 1.2 nmol/L). VEGF-A induced greatest phosphorylation of VEGFR-1 at tyrosine residues Y1048 and Y1053; this was reversed by cediranib. Potency against VEGFR-1 was comparable with that previously observed versus VEGFR-2 and VEGFR-3. Cediranib also showed significant activity against wild-type c-Kit in cellular phosphorylation assays (IC50 = 1–3 nmol/L) and in a stem cell factor–induced proliferation assay (IC50 = 13 nmol/L). Furthermore, phosphorylation of wild-type c-Kit in NCI-H526 tumor xenografts was reduced markedly following oral administration of cediranib (≥1.5 mg/kg/d) to tumor-bearing nude mice. The activity of cediranib against PDGFR-β and PDGFR-α was studied in tumor cell lines, vascular smooth muscle cells (VSMC), and a fibroblast line using PDGF-AA and PDGF-BB ligands. Both receptor phosphorylation (IC50 = 12–32 nmol/L) and PDGF-BB–stimulated cellular proliferation (IC50 = 32 nmol/L in human VSMCs; 64 nmol/L in osteosarcoma cells) were inhibited. In vivo, ligand-induced PDGFR-β phosphorylation in murine lung tissue was inhibited by 55% following treatment with cediranib at 6 mg/kg but not at 3 mg/kg or less. In contrast, in C6 rat glial tumor xenografts in mice, ligand-induced phosphorylation of both PDGFR-α and PDGFR-β was reduced by 46% to 61% with 0.75 mg/kg cediranib. Additional selectivity was showed versus Flt-3, CSF-1R, EGFR, FGFR1, and FGFR4. Collectively, these data indicate that cediranib is a potent pan-VEGFR kinase inhibitor with similar activity against c-Kit but is significantly less potent than PDGFR-α and PDGFR-β. Mol Cancer Ther; 10(5); 861–73. ©2011 AACR.

Discovery of 4-Amino-N-[(1S)-1-(4-chlorophenyl)-3-hydroxypropyl]-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamide (AZD5363), an Orally Bioavailable, Potent Inhibitor of Akt Kinases.

Wide-ranging exploration of analogues of an ATP-competitive pyrrolopyrimidine inhibitor of Akt led to the discovery of clinical candidate AZD5363, which showed increased potency, reduced hERG affinity, and higher selectivity against the closely related AGC kinase ROCK. This compound demonstrated good preclinical drug metabolism and pharmacokinetics (DMPK) properties and, after oral dosing, showed pharmacodynamic knockdown of phosphorylation of Akt and downstream biomarkers in vivo, and inhibition of tumor growth in a breast cancer xenograft model.

Development and evaluation of selective, reversible LSD1 inhibitors derived from fragments

Two series of aminothiazoles have been developed as reversible inhibitors of lysine specific demethylase 1 (LSD1) through the expansion of a hit derived from a high concentration biochemical fragment based screen of 2466 compounds. The potency of the initial fragment hit was increased 32-fold through synthesis, with one series of compounds showing clear structure–activity relationships and inhibitory activities in the range of 7 to 187 μM in a biochemical assay. This series also showed selectivity against the related FAD-dependent enzyme mono-amine oxidase A (MAO-A). Although a wide range of irreversible inhibitors of LSD1 have been reported with activities in the low nanomolar range, this work represents one of the first reported examples of a reversible small molecule inhibitor of LSD1 with clear SAR and selectivity against MAO-A, and could provide a platform for the development of more potent reversible inhibitors. Herein, we also report the use of a recently developed cell-based assay for profiling LSD1 inhibitors, and present results on our own compounds as well as a selection of recently described reversible LSD1 inhibitors.

Toxoflavins and Deazaflavins as the First Reported Selective Small Molecule Inhibitors of Tyrosyl-DNA Phosphodiesterase II

The recently discovered enzyme tyrosyl-DNA phosphodiesterase 2 (TDP2) has been implicated in the topoisomerase-mediated repair of DNA damage. In the clinical setting, it has been hypothesized that TDP2 may mediate drug resistance to topoisomerase II (topo II) inhibition by etoposide. Therefore, selective pharmacological inhibition of TDP2 is proposed as a novel approach to overcome intrinsic or acquired resistance to topo II-targeted drug therapy. Following a high-throughput screening (HTS) campaign, toxoflavins and deazaflavins were identified as the first reported sub-micromolar and selective inhibitors of this enzyme. Toxoflavin derivatives appeared to exhibit a clear structure-activity relationship (SAR) for TDP2 enzymatic inhibition. However, we observed a key redox liability of this series, and this, alongside early in vitro drug metabolism and pharmacokinetics (DMPK) issues, precluded further exploration. The deazaflavins were developed from a singleton HTS hit. This series showed distinct SAR and did not display redox activity; however low cell permeability proved to be a challenge.

Novel Steroid Inhibitors of Glucose 6-Phosphate Dehydrogenase

Novel derivatives of the steroid DHEA 1, a known uncompetitive inhibitor of G6PD, were designed, synthesized, and tested for their ability to inhibit this dehydrogenase enzyme. Several compounds with approximately 10-fold improved potency in an enzyme assay were identified, and this improved activity translated to efficacy in a cellular assay. The SAR for steroid inhibition of G6PD has been substantially developed; the 3β-alcohol can be replaced with 3β-H-bond donors such as sulfamide, sulfonamide, urea, and carbamate. Improved potency was achieved by replacing the androstane nucleus with a pregnane nucleus, provided a ketone at C-20 is present. For pregnan-20-ones incorporation of a 21-hydroxyl group is often beneficial. The novel compounds generally have good physicochemical properties and satisfactory in vitro DMPK parameters. These derivatives may be useful for examining the role of G6PD inhibition in cells and will assist the future design of more potent steroid inhibitors with potential therapeutic utility.

Discovery of AZD8931, an Equipotent, Reversible Inhibitor of Signaling by EGFR, HER2, and HER3 Receptors.

Deregulation of HER family signaling promotes proliferation and tumor cell survival and has been described in many human cancers. Simultaneous, equipotent inhibition of EGFR-, HER2-, and HER3-mediated signaling may be of clinical utility in cancer settings where the selective EGFR or HER2 therapeutic agents are ineffective or only modestly active. We describe the discovery of AZD8931 (2), an equipotent, reversible inhibitor of EGFR-, HER2-, and HER3-mediated signaling and the structure-activity relationships within this series. Docking studies based on a model of the HER2 kinase domain helped rationalize the increased HER2 activity seen with the methyl acetamide side chain present in AZD8931. AZD8931 exhibited good pharmacokinetics in preclinical species and showed superior activity in the LoVo tumor growth efficacy model compared to close analogues. AZD8931 is currently being evaluated in human clinical trials for the treatment of cancer.