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The mesenchymal–epithelial transition factor (MET) proto-oncogene encodes the MET receptor tyrosine kinase. MET aberrations drive tumorigenesis in several cancer types through a variety of molecular mechanisms including MET mutations, gene amplification, rearrangement, and overexpression. Therefore, MET is a therapeutic target and the selective type Ib MET inhibitor, tepotinib, was designed to potently inhibit MET kinase activity. In vitro, tepotinib inhibits MET in a concentration-dependent manner irrespective of the mode of MET activation, and in vivo, tepotinib exhibits marked, dose-dependent antitumor activity in MET-dependent tumor models of various cancer indications. Tepotinib penetrates the blood–brain barrier and demonstrates strong anti-tumor activity in subcutaneous and orthotopic brain metastasis models, in-line with clinical activity observed in patients. MET amplification is an established mechanism of resistance to EGFR tyrosine kinase inhibitors (TKIs) and preclinical studies show that tepotinib in combination with EGFR TKIs can overcome this resistance. Tepotinib is currently approved for the treatment of adult patients with advanced or metastatic non-small cell lung cancer harboring METex14 skipping alterations. This review focuses on the pharmacology of tepotinib in preclinical cancer models harboring MET alterations, and demonstrates that strong adherence to the principles of the Pharmacological Audit Trail may result in a successful discovery and development of a precision medicine.

Central nervous system-penetrant therapies with intracranial efficacy against non-small cell lung cancer (NSCLC) brain metastases are urgently needed. We report preclinical studies investigating brain penetration and intracranial activity of the MET inhibitor tepotinib. After intravenous infusion of tepotinib in Wistar rats (n = 3), mean (±standard deviation) total tepotinib concentration was 2.87-fold higher in brain (505 ± 22 ng/g) than plasma (177 ± 20 ng/mL). In equilibrium dialysis experiments performed in triplicate, mean tepotinib unbound fraction was 0.35% at 0.3 and 3.0 µM tepotinib in rat brain tissue, and 4.0% at 0.3 and 1.0 µM tepotinib in rat plasma. The calculated unbound brain-to-plasma ratio was 0.25, indicating brain penetration sufficient for intracranial target inhibition. Of 20 screened subcutaneous patient-derived xenograft (PDX) models from lung cancer brain metastases (n = 1), two NSCLC brain metastases models (LU5349 and LU5406) were sensitive to the suboptimal dose of tepotinib of 30 mg/kg/qd (tumor volume change [%TV]: -12% and -88%, respectively). Molecular profiling (nCounter®; NanoString) revealed high-level MET amplification in both tumors (mean MET gene copy number: 11.2 and 24.2, respectively). Tepotinib sensitivity was confirmed for both subcutaneous models at a clinically relevant dose (125 mg/kg/qd; n = 5). LU5349 and LU5406 were orthotopically implanted into brains of mice and monitored by magnetic resonance imaging (MRI). Tepotinib 125 mg/kg/qd induced pronounced tumor regression, including complete or near-complete regressions, compared with vehicle in both orthotopic models (n = 10; median %TV: LU5349, -84%; LU5406, -63%). Intracranial antitumor activity of tepotinib did not appear to correlate with blood-brain barrier leakiness assessed in T1-weighted gadolinium contrast-enhanced MRI.

Background Patients with advanced non-small cell lung cancer (NSCLC) harboring oncogenic MET alterations, such as MET exon 14 skipping or MET amplification (MET amp), benefit from MET tyrosine kinase inhibitor (TKI) treatment. Brain metastases are common in patients with advanced NSCLC. In preclinical studies in rats, tepotinib had relatively high binding to brain tissue (fu br=0.4%, fu pl=4%) and free tepotinib concentrations in brain were 25% of the concentrations found in plasma (Kp u,u=0.25). In this study we investigated the efficacy of the MET TKIs tepotinib, capmatinib, savolitinib and crizotinib in mice implanted orthotopically with MET-dependent tumor explants derived from human NSCLC brain metastases. Methods The antitumor activity of tepotinib (30 mg/kg qd) was investigated in a screen of 21 subcutaneous lung cancer patient-derived xenograft (PDX) models of brain metastases grown in NOD-SCID mice (n=1/model). 20 of these tumors were retrospectively analyzed for cancer-specific mutations, gene copy number (GCN) and gene expression by Nanostring. 2 responding models, both found to harbor MET amp, were tested again subcutaneously in NOD-SCID mice treated with vehicle or tepotinib (125 mg/kg qd; n=5). Both models were orthotopically implanted into brains of NOD-SCID mice and tumor growth was monitored by MRI. Established tumors were treated with MET TKIs (n=10) tepotinib (125 mg/kg qd), capmatinib (30 mg/kg bid), savolitinib (60 mg/kg qd) or crizotinib (50 mg/kg qd). Results 2 of 21 subcutaneous PDX tumors (LU5406 and LU5349) regressed in response to tepotinib treatment. When implanted subcutaneously again into mice, both models regressed completely upon treatment with tepotinib. Molecular profiles revealed that these were the only tumors of the 20 models investigated by Nanostring that had MET amp (high-level increase in MET GCN of >10). Both models grew orthotopically when implanted into brains of mice. Contrast-weighted MRI indicated regions with intact and disrupted blood–brain barrier (BBB) in all implanted tumors. Tumor regression of orthotopic LU5406 tumors was observed with all MET TKIs (% median tumor volume changes [%TV]: tepotinib, –63%; capmatinib, –24%; savolitinib, –38%; crizotinib, –27%). In the orthotopic LU5349 tumors, treatment with crizotinib or savolitinib led to growth inhibition (%TV: +88% and –13%, respectively), whereas tepotinib and capmatinib induced tumor regression (%TV: –84% and –63%, respectively). Conclusions The heterogenous pattern of regions with intact and disrupted BBB in the orthotopic brain metastases models is thought to mirror the clinical situation. Tepotinib was efficacious in the two MET-driven orthotopic brain metastases PDX tumors characterized by pronounced tumor regression and may be relevant to patients with brain metastases. Relationships between efficacy and BBB leakiness will be discussed. Citation Format: Manja Friese-Hamim, Anderson Clark, Lindsey Crowley, Christof Reusch, Olga Bogatyrova, Claudia Wilm, Hong Zhang, Timothy Crandall, Jing Lin, Jianguo Ma, David Bachner, Jürgen Schmidt, Martin Schaefer, Christopher Stroh. Anti-tumor activity of tepotinib in orthotopic models of lung cancer patient-derived brain metastases with MET amplification [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3407.

Small Cell Lung Cancer (SCLC) is characterized by rapid tumor growth and currently, there are few therapeutic options or predictive biomarkers. Patient derived xenograft (PDX) models are capable of recapitulating solid tumor growth including the intra-tumor heterogeneity (ITH) observed in the original patient tumor. The present study aimed to correlate surface marker profiles of SCLC PDX models with previously observed drug responses to M2698, a potent, selective inhibitor of p70S6K and AKT 1/3, and investigate ITH through gene expression profiling of tumor cell subpopulations. Drug response data had been established in a preclinical screen of 45 PDX models of SCLC, in which two mice were implanted subcutaneously with tumors from each model; one mouse was treated with vehicle while the other was treated with M2698 25 mg/kg QD po until the tumor in the vehicle-treated mouse reached ~1200 mm3. Tumor control (stasis or regression) was seen in 12 (27%) of the models. We showed previously that cell surface marker profiles of PDX tumor tissue demonstrated high intra-model reproducibility for many surface markers and uniquely associate with each model. Also, distinctly heterogeneous markers were identified that allowed FACS sorting of tumor cell subpopulations with similarly distinct gene expression profiles. To build on these data, a subset of models that were the most and the least sensitive to M2698 (n=7) in the above described screen were selected for implantation into a new set of mice. Tumors were profiled once they reached ~800 mm3. We evaluated 80+ markers commonly used to identify tumor initiating cells (e.g. CD44, CD90, CD133, CD166, CD184), EMT or aggressiveness (e.g. CD166, EphB2, CD324, CD325), poor outcome in SCLC (CD49b, CD221, claudin3) or drug targets (e.g. CD184, EGFR, Her2) to establish extensive marker profiles. Our data reveal that surface marker profiles in these models allow a meaningful subclassification of SCLC PDX tissue. Correlation of these profiles with efficacy of M2698 (above) suggest that surface markers may have predictive value. Our results prequalify a number of these markers for validation. Furthermore, several models harbor cell subpopulations identifiable by various surface markers. Along with their distinct gene expression profiles this suggests an equilibrium between functionally different compartments within a lesion. In one case, the ratio of two populations shifted concurrently with growth differences, raising the possibility of a dynamic relationship between this equilibrium and the growth stage. Overall, our workflow may provide tools for sample characterization, quality control and elucidation of cellular response markers to varying selective pressures, such as drug challenges. Citation Format: Warren Porter, Eileen Snowden, Friedrich Hahn, Mitchell Ferguson, Frances Tong, William S. Dillmore, Anderson Clark, Hong Zhang, Rainer Blaesius. Surface protein marker and single cell gene expression profiling of individual tumor cells dissociated from small cell lung cancer pdx mouse models can be correlated with in vivo sensitivity to the p70S6K/AKT1/3 inhibitor M2698 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4710.

M2698 is a potent and selective, ATP-competitive dual inhibitor of p70S6K and AKT1/3 that is being evaluated in a phase I clinical trial in cancer patients. Dual pathway inhibition by M2698 may result in improved clinical efficacy by inhibiting downstream pS6 and blocking the increased AKT activity that results from a compensatory feedback loop induced by PI3K/AKT/mTOR (PAM) pathway inhibition. In earlier studies, combination efficacy was observed with M2698 and trastuzumab in HER2+ breast cancer patient derived xenograft (PDX) models, including complete tumor regressions (Huck, BR. et.al. 105th AACR; 2014: Abstract 4516). To explore the potential combination effects in gastric cancer (GC), we evaluated the effect in in vitro and in vivo GC models. Ten human GC cell lines, which included two HER2+ lines, were treated with M2698 and trastuzumab over various concentrations and cellular proliferation was examined with a WST-8 assay. Combination effects were evaluated by Bliss independence scores and highest single agent (HSA) models. The OE-19 HER2+ cell line had the greatest Bliss and HSA sum values, whereas these measures in the other HER2+ cell line, NCI-N87, were among the lowest in the set of 10 lines, indicating that the combination is synergistic in some HER2+ GC cell lines, such as OE-19. The effects of this combination on downstream markers were analysed by Western blotting. Expression of pS6 was reduced in OE-19 cells by treatment with M2698, but pAKT and pERK were both increased. Upregulated pAKT is a known compensatory feedback mechanism that is inhibited by the dual nature of M2698. Upregulated pERK is a candidate resistance marker for PI3K pathway inhibition. However, the combination of trastuzumab with M2698 blocked this increase in pERK, suggesting that dual inhibition of the MAPK and PAM pathways may contribute to the synergistic anti-proliferative effects. The combination was then tested in the OE-19 xenograft model in vivo and significantly inhibited tumor growth compared to vehicle treatment and monotherapies (p0.05). In an in vivo pharmacodynamic study, the combination of M2698 and trastuzumab inhibited pS6 and pERK showing effective PI3K and MAPK pathway inhibition by the combination. The agents were also tested alone and in combination (n=3/treatment group) in 27 PDX models of GC in mice (ChemPartner, Shanghai, China). The tumor control rate (tumor stasis or regression) was 11% (3/27) of models treated with M2698, 15% (4/27) with trastuzumab treatment and 22% (6/27) with the combination. The PDX models are currently being evaluated for HER2 status to determine the correlation with the efficacy of the treatments. Based on the data from the OE-19 model, pERK is a candidate marker of combination efficacy which can be further explored in additional GC models. Citation Format: Shota Fukuoka, Takashi Kojima, Yoshikatsu Koga, Mayumi Yamauchi, Masahiro Yasunaga, Yasuhiro Matsumura, Kohei Shitara, Toshihiko Doi, Takayuki Yoshino, Toshio Kuronita, Anderson Clark, Brian Elenbaas, Hong Zhang, Atsushi Ohtsu. Preclinical efficacy of the p70S6K/AKT dual inhibitor M2698 in combination with trastuzumab in models of gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2935.

Small Cell Lung Cancer (SCLC) is characterized by rapid tumor growth and currently, there are few therapeutic options. As part of the development of M2698, a potent, selective inhibitor of p70S6K and AKT 1/3, the compound was tested in a preclinical screen of 45 patient derived xenograft (PDX) models of SCLC. In this screen, two mice were implanted subcutaneously with tumors for each model; one mouse was treated with vehicle while the other was treated with M2698 25 mg/kg QD po and tumors were measured 2x/week until the tumor in the vehicle-treated mouse reached ~1200 mm3. Tumor control (tumor stasis or regression) was seen in 12 (27%) of the models. From these data, a subset of models that were the most and the least sensitive to M2698 (n=7) were selected for implantation into a new set of mice. Tumors were profiled once they reached ~800 mm3 for tumor cell surface markers potentially correlating with sensitivity to M2698 seen in the previous study. PDX model systems are capable of recapitulating the intra-tumor heterogeneity (ITH) observed in the original patient tumor. The relationship between ITH and drug response/acquired drug resistance has been clearly demonstrated. Thus, a more detailed examination of this complexity in PDX tissue enables one to elucidate the underlying mechanisms in a reproducible, biologically relevant system. We have previously shown that cell surface marker profiles of PDX derived tumor tissue demonstrate high intra-model reproducibility whereas each model has a unique profile. In addition, some markers have a distinct heterogeneity. Gene expression profiling of tumor cell subpopulations identified by some of these specific markers suggest different biological roles for these subpopulations with relevance to their drug responses. Here we show surface marker and gene expression profiles of multiple PDX models for SCLC. We have evaluated 50+ markers commonly used to identify tumor initiating cells (e.g. CD44, CD90, CD133, CD166, CD184), EMT or aggressiveness (e.g. CD166, EphB2, CD324, CD325) or drug targets (e.g. CD184, EGFR, Her2) to establish extensive marker profiles. Our data reveal that surface marker profiles in SCLC PDX models are consistent among tumors from mice bearing the same model, show major differences from other PDX (e.g. breast) cancer types and heterogeneity exists for several markers of interest. By correlating gene expression and surface marker profiles in the current preclinical study, we aim to illuminate the interactions of major cell subpopulations within SCLC PDX tumor tissue and also investigate potential markers of sensitivity to growth inhibition by treatment with M2698. Overall, our workflow of deep phenotyping may provide tools for sample characterization, quality control and possibly study of cellular response to varying selective pressures such as drug challenges. Citation Format: Friedrich Hahn, Warren Porter, Eileen Snowden, Mitchell Ferguson, Frances Tong, William S. Dillmore, Anderson Clark, Hong Zhang, Rainer Blaesius. Surface marker and gene expression profiling of tumors from PDX models of small cell lung cancer with varying sensitivity to growth inhibition by the p70S6K/AKT1/3 inhibitor M2698 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2197.

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

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.

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

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 p70S6K 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 kinase-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, a unique characteristic that would allow for treating not only primary 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. Oral treatment of mice with MSC2363318A resulted in significant inhibition of tumor growth in several subcutaneous human cancer xenograft models representing breast, pancreatic, glioblastoma and ovarian cancers. Of note, a breast cancer model possessing a PTEN loss of function showed tumor regression upon treatment with MSC2363318A. In addition, MSC2363318A exhibited increased exposure in tumors as compared to plasma, resulting in sustained inhibition of S6K phosphorylation for up to 24 hours. Key preclinical activities are being completed and first in human clinical studies are scheduled to be initiated in 2013. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A162. Citation Format: Bayard R. Huck, Andreas Machl, Erik Wilker, Hui Tian, Sakeena Syed, Jing Lin, Jianguo Ma, Anderson Clark, Roseann Waterhouse, Remiguisz Kaleta, Alina Micu, Lynne Soughley, Long Li, Karin Groll, Sonja Kroesser, Frank Beier, Ursula Hering, Marc Lecomte, Katrin Wichert, Mauro D'Antonio, Paolo Di Eugenio. Identification of brain penetrant p70S6K/Akt inhibitor MSC2363318A. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A162.

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