Anderson Clark

Inhibiting Aurora kinases reduces tumor growth and suppresses tumor recurrence after chemotherapy in patient-derived triple-negative breast cancer xenografts

Triple-negative breast cancers (TNBC) have an aggressive phenotype with a relatively high rate of recurrence and poor overall survival. To date, there is no approved targeted therapy for TNBCs. Aurora kinases act as regulators of mammalian cell division. They are important for cell-cycle progression and are frequently overexpressed or mutated in human tumors, including breast cancer. In this study, we investigated the therapeutic potential of targeting Aurora kinases in preclinical models of human breast cancers using a pan-inhibitor of Aurora kinases, AS703569. In vitro, AS703569 was tested in 15 human breast cancer cell lines. TNBC cell lines were more sensitive to AS703569 than were other types of breast cancer cells. Inhibition of proliferation was associated with cell-cycle arrest, aneuploidy, and apoptosis. In vivo, AS703569 administered alone significantly inhibited tumor growth in seven of 11 patient-derived breast cancer xenografts. Treatment with AS703569 was associated with a decrease of phospho-histone H3 expression. Finally, AS703569 combined to doxorubicin–cyclophosphamide significantly inhibited in vivo tumor recurrence, suggesting that Aurora kinase inhibitors could be used both in monotherapy and in combination settings. In conclusion, these data indicate that targeting Aurora kinases could represent a new effective approach for TNBC treatment. Mol Cancer Ther; 11(12); 2693–703. ©2012 AACR.

SAR and evaluation of novel 5H-benzo[c][1,8]naphthyridin-6-one analogs as Aurora kinase inhibitors

Several potent Aurora kinase inhibitors derived from 5H-benzo[c][1,8]naphthyridin-6-one scaffold were identified. A crystal structure of Aurora kinase A in complex with an initial hit revealed a binding mode of the inhibitor within the ATP binding site and provided insight for structure-guided compound optimization. Subsequent SAR campaign provided a potent and selective pan Aurora inhibitor, which demonstrated potent target modulation and antiproliferative effects in the pancreatic cell line, MIAPaCa-2. Furthermore, this compound inhibited phosphorylation of histone H3 (pHH3) in mouse bone morrow upon oral administration, which is consistent with inhibition of Aurora kinase B activity.

Abstract LB-456: Evaluation of brain pharmacokinetics as a potential differentiation factor for the MEK inhibitors, MSC2015103 and pimasertib

MSC2015103 is an orally bio-available, selective, and highly potent small molecule inhibitor of MEK1/2. As a follower to the front-runner MEK inhibitor, pimasertib (MSC1936369/AS703026), a prime objective for the program is to differentiate the two compounds. Results from previous pharmacokinetic (PK) studies of MSC2015103 and pimasertib in mice had shown that both compounds could effectively cross the blood-brain barrier, but that MSC2015103 was retained in the brain longer than pimasertib. This was further confirmed in a study examining the whole-body distribution of radio-labeled compounds in mice. It is unclear whether the differential brain PK characteristics of the two agents will be clinically significant. To begin to address this, a series of pre-clinical studies were performed. Exposure levels and concurrent target modulation in normal murine brain tissue were examined over time following administration of multiple doses of MSC2015103 and pimasertib. Notable differences in the magnitude and temporal dynamics of exposure were observed; while concentrations of pimasertib in the brain peaked ∼1 hour post-administration (with a correlative decrease in phospho-ERK of ∼90%) with a relatively rapid clearance out of the tissue, concentrations of MSC2015103 increased in the brain over time and remained relatively elevated until 24 hours post-administration (the last time point) with only marginal target modulation observed. As more dramatic inhibition of pERK has previously been observed in subcutaneous tumors in mice in the presence of the same exposure of MSC2015103, murine brain orthotopic models of glioblastoma were employed to compare the relative target modulation of MSC2015103 and pimasertib in tumor tissue within the brain compartment, as well as their potential anti-tumor effects. Data from these orthotopic studies demonstrated similar high levels of phospho-ERK inhibition for both MSC2015103 and pimasertib in glioblastoma tumor tissue, which correlated with similar anti-tumor activity in the U87 model. The PK of MSC2015103 varied considerably from pimasertib, with a higher exposure (AUC1-24h) ratio of brain tumor-to-normal brain with MSC2015103 as compared with pimasertib. In line with the PK findings, MSC2015103 inhibited phospho-ERK in brain tumors but with relatively less target modulation in normal brain tissue, whereas pimasertib showed similar inhibition of phospho-ERK in both tissues. Collectively, these findings suggest a potential improvement in the safety/therapeutic index in the brain for MSC2015103. This may translate into other tissues, such as the eye, which has a similar blood barrier, and may be important in light of ocular toxicities observed in clinical trials with other MEK inhibitors. 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 LB-456. doi:1538-7445.AM2012-LB-456

Abstract 139: M2698, a novel dual inhibitor of p70S6K and Akt: preclinical efficacy in gastric cancer

M2698 is a selective, ATP-competitive dual inhibitor of p70S6K and Akt1/3 that is being evaluated in a phase I clinical trial in cancer patients. The dual nature of M2698 may result in improved clinical efficacy by blocking the increased AKT activity in a compensatory feedback loop induced by PI3K/AKT/mTOR (PAM) pathway inhibition. In previous preclinical studies, M2698 was shown to have potent anti-proliferative activity in vitro, and inhibit tumor growth in some xenograft models in vivo. The current study examined the effects of M2698 on cell proliferation in a panel of 13 gastric cancer cell lines, as gastric cancers often harbor mutations in PAM pathway genes that deregulate this signalling pathway. Cells were treated with M2698 at a range of concentrations and proliferation was evaluated at least twice using the WST-8 cell proliferation assay kit (Dojindo Molecular Technologies, Inc. Japan). Two cell lines, HGC-27 and IM95m, were particularly sensitive to M2698 (50% growth inhibition concentration [GI50] 84 and 160 nM, respectively). The GI50 values for all other cell lines were >10-fold higher. Although HGC-27 and IM95m each carry a PIK3CA hotspot point mutation, the presence of an activating PI3K pathway mutation was not the sole determinant of sensitivity, as a third PIK3CA mutant cell line, MKN1, was far less sensitive to M2698 (GI50 9.0 uM). Western blot analysis of pharmacodynamic biomarkers showed that M2698 (1 uM) blocked the PAM pathway in both sensitive and resistant cell lines, inhibiting phospho[p]‐S6 and p‐PRAS40, despite increased p‐Akt. Some biomarkers from the PAM pathway and other signaling pathways appeared to be associated with sensitivity to M2698, but these candidate biomarkers need to be validated in a larger panel of cell lines. Treatment of HGC-27-tumor-bearing mice with M2698 (10, 20, 30 mg/kg/day) for 14 days resulted in significant tumor growth inhibition (80.2-98.6%) at Day 29 compared to treatment with vehicle (p Citation Format: Shota Fukuoka, Takashi Kojima, Yoshikatsu Koga, Mayumi Yamauchi, Masahiro Yasunaga, Yasuhiro Matsumura, Toshihiko Doi, Takayuki Yoshino, Toshio Kuronita, Anderson Clark, Brian Elenbaas, Atsuhi Ohtsu. M2698, a novel dual inhibitor of p70S6K and Akt: preclinical efficacy in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 139. doi:10.1158/1538-7445.AM2017-139

Abstract 4516: Evaluation of p70S6K/Akt inhibitor MSC2363318A in patient derived xenograft (PDX) models of breast cancer

The PI3K pathway is involved in the regulation of cell growth, proliferation, metabolism and other functions. Aberrant signaling (PTEN loss of function, PIK3CA mutation, Akt amplification, etc.) from the PI3K pathway is observed in >50% of all tumors. Clinical evidence suggests that inhibiting the PI3K pathway is beneficial for the treatment of solid tumors and tumors of the hematopoietic system. Inhibition of mTOR via rapalogs has been shown to block a negative feedback loop, thereby leading to the activation of Akt. The activation of this Akt feedback loop has been suggested to potentially compromise the clinical efficacy of selective mTORC1 inhibitors such as temsirolimus and everolimus. Dual p70S6K/Akt inhibition may promote improved pathway inhibition and also block the negative consequences of Akt activation through the negative feedback loop. MSC2363318A is a highly selective, potent, adenosine triphosphate (ATP) competitive inhibitor of p70S6K, Akt1, and Akt3. In a cellular context, inhibition of p70S6K leads to potent inhibition of ribosomal protein S6 phosphorylation, while inhibition of Akt activity blocks the negative effects of a compensatory feedback loop. In addition, MSC2363318A exhibits potent anti-proliferative activity against many solid tumor cell lines in vitro, especially those with PI3K pathway genomic alterations. Further, MSC2363318A can also cross the blood-brain barrier (via pre-clinical studies in mice, rat, and dog), a unique characteristic that would allow for treating not only malignancies that are driven by PI3K pathway genomic alterations, but also indications with a high incidence of CNS metastases and primary malignancies of the central nervous system. Patient Derived Xenograft (PDX) models from breast cancers with a high prevalence of PI3K pathway genomic alterations; including, triple negative breast cancer and Her2+ breast cancer were evaluated. In addition, combinations with standard of care agents were then evaluated in these breast cancer PDX models. Results from these studies were correlated with PI3K pathway genomic modifications, and will be used to guide subsequent clinical studies. Citation Format: Bayard R. Huck, H Tian, Sakeena Syed, Jing Lin, Jianguo Ma, Anderson Clark, Remiguisz Kaleta, Andreas Machl, Erik Wilker, Marc Lecomte. Evaluation of p70S6K/Akt inhibitor MSC2363318A in patient derived xenograft (PDX) models of breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4516. doi:10.1158/1538-7445.AM2014-4516

Abstract LB-208: Hijacking the PI3K/mTor and KRas/MEK/ERK signaling pathways with a therapeutic assault results in robust antitumor activity in PI3K/KRas and KRas mutant tumors

The PI3K/AKT/mTOR and Ras/Raf/MEK/ERK are interlinked growth and survival signaling pathways both involving regulation by Ras and often constitutively activated in human tumors as a result of frequent mutations in p1 10α, Ras and BRaf. Here, we have assessed the antitumor activity of the oral, potent and selective allosteric inhibitor of MEK1/2, MSC1936369 (formerly known as AS703026), in combination with SAR245408 (pan-PI3K formerly named XL147) or SAR245409 (dual panPI3K/mTOR formerly named XL765) in cellular in vitro and in vivo xenograft settings. In vitro, the anti-proliferative effects of MSC1936369 in combination with SAR245409 were evaluated in a panel of 81 tumor cell lines (17 indications). Potent combination effects were seen in colorectal, pancreatic, breast and NSCL cancers when compared to each agent alone. Across indications, tumor cells harboring mutations in KRas, p1 10α, BRaf and both p1 10α and KRas were identified as those more sensitive to the combination. In vivo, suboptimal therapeutic doses of MSC1936369, SAR245408 and SAR245409 were tested PO daily as single agents and in combination in human tumor xenograft models: MiaPaCa-2 pancreatic carcinoma (KRas mut), HCT116 colorectal adenocarcinoma (KRas/PIKC3A mut). In animals bearing MiaPaCa-2 xenografts, tumor growth inhibition was observed in all of the treatment groups, to varying degrees, compared to vehicle (p Overall, the combination treatment of the MEK inhibitor MSC1936369 and the dual panPI3K/mTOR inhibitor SAR245409 showed enhanced tumor inhibition both in a large battery of tumor-derived cell lines as well as in xenograft models of human cancer (KRas mut and dual PI3K/KRas mut). In addition, combination therapy with the panPI3K inhibitor SAR245408 demonstrated a robust gain of antitumor activity, particularly in the dual PI3K/KRas mutant tumors. The available preclinical pharmacological data support the use of these combinations in clinical settings. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-208. doi:10.1158/1538-7445.AM2011-LB-208