Dorothea Rudolph

BI 6727, A Polo-like Kinase Inhibitor with Improved Pharmacokinetic Profile and Broad Antitumor Activity

Purpose: Antimitotic chemotherapy remains a cornerstone of multimodality treatment for locally advanced and metastatic cancers. To identify novel mitosis-specific agents with higher selectivity than approved tubulin-binding agents (taxanes, Vinca alkaloids), we have generated inhibitors of Polo-like kinase 1, a target that functions predominantly in mitosis. Experimental Design: The first compound in this series, suitable for i.v. administration, has entered clinical development. To fully explore the potential of Polo-like kinase 1 inhibition in oncology, we have profiled additional compounds and now describe a novel clinical candidate. Results: BI 6727 is a highly potent (enzyme IC50 = 0.87 nmol/L, EC50 = 11-37 nmol/L on a panel of cancer cell lines) and selective dihydropteridinone with distinct properties. First, BI 6727 has a pharmacokinetic profile favoring sustained exposure of tumor tissues with a high volume of distribution and a long terminal half-life in mice (Vss = 7.6 L/kg, t1/2 = 46 h) and rats (Vss = 22 L/kg, t1/2 = 54 h). Second, BI 6727 has physicochemical and pharmacokinetic properties that allow in vivo testing of i.v. as well as oral formulations, adding flexibility to dosing schedules. Finally, BI 6727 shows marked antitumor activity in multiple cancer models, including a model of taxane-resistant colorectal cancer. With oral and i.v. routes of administration, the total weekly dose of BI 6727 is most relevant for efficacy, supporting the use of a variety of well-tolerated dosing schedules. Conclusion: These findings warrant further investigation of BI 6727 as a tailored antimitotic agent; clinical studies have been initiated.

Efficacy and mechanism of action of volasertib, a potent and selective inhibitor of Polo-like kinases, in preclinical models of acute myeloid leukemia

Polo-like kinase 1 (Plk1), a member of the Polo-like kinase family of serine/threonine kinases, is a key regulator of multiple steps in mitosis. Here we report on the pharmacological profile of volasertib, a potent and selective Plk inhibitor, in multiple preclinical models of acute myeloid leukemia (AML) including established cell lines, bone marrow samples from AML patients in short-term culture, and subcutaneous as well as disseminated in vivo models in immune-deficient mice. Our results indicate that volasertib is highly efficacious as a single agent and in combination with established and emerging AML drugs, including the antimetabolite cytarabine, hypomethylating agents (decitabine, azacitidine), and quizartinib, a signal transduction inhibitor targeting FLT3. Collectively, these preclinical data support the use of volasertib as a new therapeutic approach for the treatment of AML patients, and provide a foundation for combination approaches that may further improve and prolong clinical responses.

Pharmacological Profile of BI 847325, an Orally Bioavailable, ATP-Competitive Inhibitor of MEK and Aurora Kinases.

Although the MAPK pathway is frequently deregulated in cancer, inhibitors targeting RAF or MEK have so far shown clinical activity only in BRAF- and NRAS-mutant melanoma. Improvements in efficacy may be possible by combining inhibition of mitogenic signal transduction with inhibition of cell-cycle progression. We have studied the preclinical pharmacology of BI 847325, an ATP-competitive dual inhibitor of MEK and Aurora kinases. Potent inhibition of MEK1/2 and Aurora A/B kinases by BI 847325 was demonstrated in enzymatic and cellular assays. Equipotent effects were observed in BRAF-mutant cells, whereas in KRAS-mutant cells, MEK inhibition required higher concentrations than Aurora kinase inhibition. Daily oral administration of BI 847325 at 10 mg/kg showed efficacy in both BRAF- and KRAS-mutant xenograft models. Biomarker analysis suggested that this effect was primarily due to inhibition of MEK in BRAF-mutant models but of Aurora kinase in KRAS-mutant models. Inhibition of both MEK and Aurora kinase in KRAS-mutant tumors was observed when BI 847325 was administered once weekly at 70 mg/kg. Our studies indicate that BI 847325 is effective in in vitro and in vivo models of cancers with BRAF and KRAS mutation. These preclinical data are discussed in the light of the results of a recently completed clinical phase I trial assessing safety, tolerability, pharmacokinetics, and efficacy of BI 847325 in patients with cancer. Mol Cancer Ther; 15(10); 2388–98. ©2016 AACR.

Abstract 1919: Pharmacological characterization of BI 847325, a dual inhibitor of MEK and Aurora kinases

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The RAS-dependent MAP kinase signaling pathway plays an important role in the regulation of cell proliferation and survival. RAS genes are frequently mutated in human cancer; however, it has not been possible to date to design direct inhibitors of RAS proteins. Inhibitors of the downstream kinase MEK are active against a subset of KRAS-mutant cancers in preclinical studies, but have shown limited success to date in clinical trials. We have identified a compound that potently inhibits MEK as well as Aurora kinases, a family of serine/threonine kinases involved in the regulation of mitosis. In enzymatic assays, BI 847325 inhibited the activity of Aurora A, B and C with IC50 values of 3, 25 and 15 nM, respectively; IC50 values of 25 and 4 nM were determined for MEK1 and MEK2, respectively. To determine whether the enzyme profile translates into cellular activity we used Western blot and FACE-ELISA assays of phospho-histone H3 (pHH3) and phospho-ERK (pERK) levels in cells treated with BI 847325 and observed EC50 values of 44 nM (NCI-H460 cells, KRAS and PI3Kα mutant) and 37 nM (A375 cells, BRAF mutant), respectively. In vitro profiling in a panel of 240 cell lines with diverse tissue origin and genetic background demonstrated that BI 847325 is a potent inhibitor of cell proliferation (gm GI50 = 28 nM) and induces cell death in a subset of cell lines. In vitro potency significantly correlated with mutations in RAS or BRAF. For comparison, a significant correlation of mutation status and sensitivity was also observed for a selective MEK inhibitor, AZD6244, but not for a selective Aurora inhibitor, BI 811283. In vivo efficacy was studied in nude mouse xenograft models of NSCLC (Calu-6, mutant KRAS) and cutaneous melanoma (A375, mutant BRAF). A daily oral dose of 10 mg/kg resulted in complete inhibition of tumor growth in the Calu-6 model (TGI = 102%, regression in 4/7 animals) and the A375 model (TGI = 116%, regression in 7/7 animals). Inhibition of Aurora B and MEK was monitored ex vivo by determining the phosphorylation state of histone H3 and ERK1/2 in tumor tissue. Immunohistochemical analyses confirmed a significant reduction of both pERK and pHH3 levels in the A375 tumors of treated animals compared to controls. To further profile the mode of action of the compound, the efficacy of BI 847325 in the MIAPaCa2-pancreatic adenocarcinoma model (mutant KRAS) was directly compared with that of the MEK inhibitor GSK 1120212. BI 847325 effectively induced tumor regression (TGI on day 22 = 126%) that was maintained in all animals on day 43. In contrast, treatment with GSK 112021 resulted in initial tumor regression, followed by re-growth after 3-4 weeks (TGI on day 22 = 129%; regrowth on day 43 in 5/7 animals). Inhibition of Aurora kinase in addition to MEK blockade thus may prevent/delay onset of resistance. Additional xenograft models with diverse genetic background are currently under investigation. Clinical development of BI 847325 has been initiated. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1919. doi:1538-7445.AM2012-1919