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Mechanistic target of rapamycin (mTOR), a key player in cell proliferation, growth and survival, is overactivated in tumors and neurological disorders.[1] Rapalogs have recently been explored to alleviate epileptic seizures in Tuberous Sclerosis Complex (TSC).[2] Herein, we combined pharmacophore features of PQR620[3], the first-in-class brain penetrant ATP-competitive mTOR kinase inhibitor showing efficacy in a TSC mouse model, and PQR617[4], a potent, highly selective mTOR inhibitor. An extensive chemical exploration of the morpholine ring led to the discovery of PQR626, a highly potent, selective, brain penetrant inhibitor of mTORC1/2 kinase. In male Sprague Dawley rats and female C57BL/6J mice, PQR626 displayed an excellent brain penetration compared to everolimus, which possessed a limited ability to cross the blood-brain-barrier (brain/plasma levels ~ 1.4:1 vs 1:92). An additional pharmacokinetic comparative study with everolimus and AZD2014 confirmed the superiority of PQR626 [brain/plasma levels: ~ 1:25 (AZD2014), ~ 1:61 (everolimus), ~ 1.8:1 (PQR626)]. PQR626 showed very good tolerability in mice (MTD 100-150 mg/kg). Efficacy studies, using mice with conditional inactivation of the Tsc1 gene primarily in glia (Tsc1GFAPCKO mice), were performed in a dose-range finding study. PQR626 (50 mg/kg, BID - twice a day) showed a significant effect on survival and significantly prevented/decreased mortality as compared to the vehicle. On the basis of its favorable pharmacological parameters, excellent brain penetration, safety profile and efficacy in Tsc1GFAPCKO mice, PQR626 qualifies as a novel mTOR inhibitor with potential application in the treatment of epilepsy and neurological disorders. [1] Wymann M. P. and Schneiter R. Nat. Rev. Mol. Cell Biol. 2008, 9, 162-176. [2] Krueger D. A. et. al. Neurology 2016, 87, 2408-2415. [3] Rageot D. et. al. J Med Chem. 2018, 61 (22), 10084-10105. [4] Borsari C. et. al. J Med Chem. 2019, 62 (18), 8609-8630. Citation Format: Chiara Borsari, Erhan Keles, Denise Rageot, Anna Melone, Thomas Bohnacker, Lucinda Kate Batchelor, Martina De Pascale, Paul Hebeisen, Petra Hillmann, Doriano Fabbro, Matthias Wymann. Discovery and preclinical characterization of PQR626: A potent, orally available, and brain-penetrant mTOR inhibitor for the treatment of tuberous sclerosis complex [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 665.

The PI3K/AKT/mTOR signaling pathway plays a fundamental role in cell proliferation, growth and survival and aberrant activation of this signaling pathway has been shown to drive the progression of malignant tumors.[1] Drugs targeting the pathway at multiple points, such as dual PI3K/mTOR inhibitors appear to have the broadest activity profile to address cancer therapeutic strategies and are currently being explored in numerous clinical studies. Recently, we presented PQR309, a novel, brain-penetrant pan-PI3K/mTOR inhibitor, which entered phase II clinical trials in 2016.[2] Here, we report the lead optimization of PQR530, a potent and brain-penetrant follow-up compound as pan-PI3K/mTORC1/2 inhibitor. The development of a follow-up compound concentrated on the improvement of both, the potency and the selectivity for all targeted kinases, namely the class IA PI3K isoforms as well as mTOR. We present a detailed ligand-based structure-activity relationship study which was obtained by systematic modifications of the hinge region as well as the affinity binding substituents. This study led to the identification of PQR530, a dual pan-PI3K/mTORC1/2 inhibitor showing excellent activities in cellular assays as well as in PI3Kα and mTOR enzymatic binding assays. In A2058 melanoma cells PQR530 inhibited protein kinase B (PKB, pSer473) and ribosomal protein S6 (pS6, pSer235/236) phosphorylation with IC50 values of 0.07 µM. PQR530 showed excellent selectivity over a wide panel of kinases, as well as excellent selectivity versus unrelated receptor enzymes and ion channels. Moreover, PQR530 displayed potency in a panel of 44 cancer cell lines (NTRC OncolinesTM) to prevent cancer cell growth (mean value for GI50 of 426 nM). Oral application of PQR530 to mice resulted in a dose-proportional PK and demonstrated good oral bioavailability and excellent brain penetration.[3] An optimized, robust synthetic route allowed rapid access to multi-gram quantities of PQR530 for pre-clinical development in only 4 steps. In conclusion, PQR530 inhibits all PI3K isoforms and the mammalian target of rapamycin (mTOR) complexes C1/2 potently and selectively, and shows anti-tumor effects in vitro and in vivo. [1] M. P. Wymann, M. Zvelebil, M. Laffargue (2003). Phosphoinositide 3-kinase signalling – which way to target? Trends Pharmacol Sci.; 24, 366-376. [2] V. Cmiljanovic et. al. “PQR309: Structure-Based Design, Synthesis and Biological Evaluation of a Novel, Selective, Dual Pan-PI3K/mTOR Inhibitor” presented at AACR Annual Meeting 2015, April 18-22, Philadelphia, Pennsylvania, USA. [3] P. Hillmann et al. “Pharmacological Characterization of the Selective, Orally Bioavailable, Potent Dual PI3K/mTORC1/2 Inhibitor PQR530” abstract submitted for AACR Annual Meeting 2017, April 1-5, Washington, D. C., USA. Citation Format: Denise Rageot, Florent Beaufils, Anna Melone, Alexander M. Sele, Thomas Bohnacker, Marc Lang, Jürgen Mestan, Petra Hillmann, Paul Hebeisen, Doriano Fabbro, Matthias P. Wymann. Discovery and biological evaluation of PQR530, a highly potent dual pan-PI3K/mTORC1/2 inhibitor [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 140. doi:10.1158/1538-7445.AM2017-140

Class I phosphoinositide 3-kinases (PI3Ks) are lipid kinases, produce PtdIns(3,4,5)P3 and trigger intracellular signaling pathways that are vital to cell growth, proliferation, survival and migration. Constitutive activation of PI3K is frequently observed in many tumor types, which defines PI3K as a valuable drug target in oncology.1 Numerous PI3K inhibitors in clinical development contain a morpholine moiety that mediates hinge region binding in the ATP pocket of PI3K by a hydrogen bond with the active site valine backbone nitrogen (Val851 in PI3Kα)2. We present here novel pyrimidinopyrrolo-oxazines related to the clinically advanced, pyridinylmorpholine and triazinylmorpholine derived pan-PI3K/mTOR inhibitors BKM120 and PQR309. The novel fused tricyclic core of these compounds contains two morpholine moieties of which one is conformationally restricted by the introduction of a methylene bridge that links the pyrimidine core with one of the two morpholine moieties. This modification leads to the generation of two regioisomers, each existing as a set of enantiomers. We investigated the influence of this conformational restriction on PI3K inhibitory activity and analyzed the distinct selectivity profiles and potencies of the respective stereo- and regio-isomers. The design and preparation of specific compounds in combination with biological assays (phosphorylation of PKB and S6, binding affinity to p110α), structure-activity relationship (SAR) and molecular modelling studies allowed us to understand the binding mode of these compounds and acquire valuable information that potentially lead to the development of derivatives with a distinct selectivity profile (e.g. PI3K versus mTOR). A selection of compounds demonstrated inhibition of protein kinase B (pSer473) and ribosomal protein S6 (pSer235/236) phosphorylation with IC50 values in the nanomolar range and high inhibitory potency of all PI3K isoforms (Ki(p110α) > 40 nM). Single p.o. administration of our lead compound to SD rats resulted in good oral bioavailability as well as excellent brain penetration. Furthermore, mechanism of action-based increases in glucose levels and insulin levels have been observed. In conclusion, we present here the development, optimization, preparation and biological evaluation of a novel class of potent, orally available and brain-penetrant pan-PI3K inhibitors that represent an innovative extension to known pyrimidinomorpholine derived PI3K inhibitors. Moreover, our results add to the understanding of how introducing specific structural and conformational modifications can lead to the development of optimized, selective PI3K and mTOR inhibitors. [1] Thorpe, L. M.; Yuzugullu, H.; Zhao, J. J. Nat. Rev. Cancer 2015, 15, 7-24. [2] Andrs, M.; Korabecny, J.; Jun, D.; Hodny, Z.; Bartek, J.; Kuca, K. J. Med. Chem. 2015, 58, 41-71. Citation Format: Alexander M. Sele, Denise Rageot, Florent Beaufils, Anna Melone, Thomas Bohnacker, Eileen Jackson, Jean-Baptiste Langlois, Paul Hebeisen, Doriano Fabbro, Matthias P. Wymann. Tricyclic fused pyrimidinopyrrolo-oxazines reveal conformational preferences of morpholine for PI3K hinge region binding [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 153. doi:10.1158/1538-7445.AM2017-153

Introduction: The phosphatidylinositol 3-kinase (PI3K) signaling pathway plays a fundamental role in many cellular processes like growth, survival, proliferation, differentiation and motility. In cancers several mutations have been identified that lead to constitutive activation of PI3K. PQR530 is a novel, ATP site directed inhibitor of all PI3K isoforms and the mammalian target of rapamycin (mTOR) complexes C1/2 that is currently in pre-clinical development. PQR530 potently binds to its targets, inhibits cell proliferation and shows excellent selectivity versus related and unrelated kinases [1]. Results: PQR530 inhibits PI3K signaling in stimulated MCF7 cells as detected by PathScan analysis. Excellent tolerability has been found for PQR530 during GLP toxicological testing in rats and dogs. Increase in insulin and blood glucose, a treatable class effect of PI3K inhibitors, has been observed after PQR530 administration to mice. Investigation of mutagenicity and hERG binding resulted in a clean profile. PQR530 exhibited dose-proportional pharmacokinetics (PK) in male C57BL/6J mice. A maximum concentration (Cmax) in plasma and brain was reached after 30 minutes (7.8 μg/ml and 112.6 μg/ml, respectively) indicating that efficacious concentrations were reached in both tissues. The calculated half-life (t1/2) for plasma and brain was approximately 5 hours. PQR530 potently inhibited PI3K signaling in vivo for several hours after administration of a single oral dose of 50 mg/kg. Tumor growth was significantly decreased in SUDHL-6 lymphoma, RIVA lymphoma and OVCAR-3 ovarian cancer mouse xenografts using daily, oral administration. Conclusion: PQR530 is a potent, ATP competitive pan-PI3K and mTORC1/2 inhibitor. The physico-chemical properties of PQR530 result in good oral bioavailability and excellent brain penetration. PQR530 is well tolerated and efficiently inhibits tumor growth in xenograft models. Preclinical data allow for further development of the compound. [1] Rageot D, et al., Discovery and biological evaluation of PQR530, a highly potent dual pan-PI3K/mTORC1/2 inhibitor, abstract submitted for AACR Annual Meeting 2017, April 1-5, Washington, D. C., USA. Citation Format: Petra Hillmann, Denise Rageot, Florent Beaufils, Anna Melone, Alexander Sele, Robert A. Ettlin, Jürgen Mestan, Vladimir Cmiljanovic, Marc Lang, Elisabeth Singer, Carolin Walter, Hoa HP Nguyen, Paul Hebeisen, Matthias P. Wymann, Doriano Fabbro. Pharmacological characterization of the selective, orally bioavailable, potent dual PI3K/mTORC1/2 inhibitor PQR530 [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 159. doi:10.1158/1538-7445.AM2017-159

Introduction: The mammalian target of rapamycin (mTOR) signaling pathway is an integrating factor in cell physiology that influences many processes like growth, metabolism and proliferation. mTOR signaling is constitutively activated in many cancers. Rapamycin is an allosteric inhibitor of mTOR that targets a subset of mTOR functions via inhibition of the mTORC1 complex. An ATP site-directed mTORC1/2 inhibitor that fully blocks all mTOR functions is desirable as cancer therapeutic. PQR620 is a novel, ATP site directed inhibitor of mTOR that is currently in pre-clinical development. PQR620 potently binds to its target (Kd = 6 nM) and shows excellent selectivity versus related and unrelated kinases [1]. Results: PQR620 inhibits mTOR signaling in stimulated MCF7 cells as detected by PathScan analysis. Excellent tolerability has been observed in mice (MTD = 150 mg/kg). A 14 day GLP toxicological study in rats showed very good tolerability (MTD = 30 mg/kg). Only minor toxicities such as dose-related changes in body weight and blood count were observed. PQR620 was administered to male C57BL/6J mice for a pharmacokinetic (PK) and pharmacodynamics (PD) evaluation. After oral application PQR620 exhibited dose-proportional PK, a maximum concentration (Cmax) in plasma and brain was reached after 30 minutes (4.8 μg/ml and 7.7 μg/ml, respectively). In muscle, Cmax (7.6 μg/ml) was reached after 2 hours. The calculated half-life (t1/2) for plasma and brain was approximately 5 hours. After 8 hours, the total exposure (expressed as AUC0-tz (area under the curve)) was 20.5 μg*h/ml in plasma, while it was approximately 30% higher in both, brain and thigh muscle (30.6 and 32.3 μg*h/ml, respectively). PQR620 potently inhibited mTOR signaling in vivo after administration of a single oral dose of 50 mg/kg. Importantly, no effect on plasma insulin levels was observed. In an OVCAR-3, ovarian carcinoma mouse xenograft, PQR620 effectively attenuated tumor growth using daily, oral dosing. Conclusion: PQR620 potently inhibits mTORC1/2 in vitro and in vivo. The physico-chemical properties of PQR620 result in good oral bioavailability and excellent brain penetration. PQR620 is well tolerated and efficiently inhibits tumor growth in xenograft models. Preclinical data allow for further development of the compound. [1] Beaufils F, Rageot D, et al., Structure-Activity Relationship Studies, Synthesis and Biological Evaluation of PQR620, a Highly Potent and Selective mTORC1/2 Inhibitor, AACR annual meeting 2016 Citation Format: Florent Beaufils, Denise Rageot, Anna Melone, Alexander Sele, Marc Lang, Juergen Mestan, Robert A. Ettlin, Petra Hillmann, Vladimir Cmiljanovic, Carolin Walter, Elisabeth Singer, Hoa HP Nguyen, Paul Hebeisen, Doriano Fabbro, Matthias P. Wymann. Pharmacological characterization of the selective, orally bioavailable, potent mTORC1/2 inhibitor PQR620. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 393A.

Introduction Acid reducing agents (ARAs) - such as proton pump inhibitors, H2-antagonists or antacids - are commonly prescribed medications to reduce stomach acidity in cancer patients. Increased gastric pH can significantly impair the dissolution of agents that exhibit pH-dependent solubility, thus possibly reducing their absorption and influence their pharmacokinetics (PK). PQR309 is a novel oral balanced dual pan-PI3K and mTOR inhibitor currently in clinical development for treatment of solid tumors and hematological malignancies. PQR309 is a weak base and exhibits pH-dependent solubility. Therefore, the assessment of the potential for drug-drug interactions with ARAs is essential to avoid treatment failure in cancer patients. Methods GastroPlusTM v.9.0 (Simulations Plus, Inc.) was used to build a physiologically-based absorption and pharmacokinetic (PBPK) model of PQR309. A baseline model was built with the physicochemical properties of the compound and pre-clinical PK data after iv and po administration. The model was then extended using PK data from cancer patients. Volume of distribution and renal clearance were calculated using the Lukacova and fup*GFR methods, respectively. Hepatic clearance was estimated from in vitro clearance obtained in hepatocytes and the intestinal absorption was calculated by the Advanced Compartmental Absorption and Transit (ACATTM) Model. Results The parameter sensitivity analysis showed that at fasted stomach pH of ∼1.5, PQR309 is fully dissolved and rapidly absorbed in the upper part of gastrointestinal tract leading to a distinct maximum plasma concentration (Cmax) and a predicted bioavailability of almost 100%. At a stomach pH of 4.0 dissolution is delayed and the absorption shifted towards distal parts of the gastrointestinal tract. The predicted bioavailability is still estimated to be good (> 75%), but the observed plasma concentration time profile is much shallower and the expected Cmax considerably reduced. Conclusions Our model predicts that concomitant administration of ARAs can impact PQR309 absorption and change its pharmacokinetic profile. The clinical relevance of this potential drug-drug interaction is unknown. In currently ongoing clinical studies co-medication of PQR309 with ARAs should be avoided until further clinical investigations confirm the model predictions and mitigation strategies are explored. Citation Format: Karin Jorga, Eva Huehn, Grace Fraczkiewicz, Debora Schmitz, Doriano Fabbro, Sasa Dimitrijevic. Concomitant administration of acid reducing agents can impact the pharmacokinetics of the balanced pan-PI3K and mTOR inhibitor PQR309. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 382.

Mammalian target of rapamycin (mTOR) signaling pathway plays a fundamental role in cell proliferation, differentiation, growth and survival.[1] As a consequence, various tumors and central nervous system (CNS) disorders share aberrant activation of the mTOR pathway. Drugs targeting the mTOR pathway represent therefore a valuable path to address multiple therapeutic areas.[1-2] Here, we report the lead optimization of PQR620, a novel potent and selective brain penetrant inhibitor of mTORC1/2. The development of selective mTOR inhibitors is particularly challenging due to extensively conserved amino acid residues in the ATP binding pocket within the PI3K and PI3K-related protein kinase family. Here, we present a detailed ligand-based structure activity relationship study allowing selective targeting of mTOR kinase activity without the interference of other PI3K family members. Systematic variation of the hinge region and affinity binding motifs led to the identification of PQR620, a morpholino-triazinyl derivative, as potent and selective mTOR inhibitor. Substitution of the morpholine binding to the hinge region and introduction of a 2-aminopyridine, substituted with a difluoromethyl group, induced a >1000-fold selectivity towards mTOR over PI3Kα in enzymatic binding assays. In A2058 melanoma cells PQR620 demonstrated inhibition of protein kinase B (pSer473) and ribosomal protein S6 (pSer235/236) phosphorylation with IC50 values of 0.2 μM and 0.1 μM, respectively. The physico-chemical properties of PQR620 result in good oral bioavailability and excellent brain penetration. PQR620 showed excellent selectivity over a wide panel of kinases, as well as excellent selectivity versus unrelated receptor enzymes and ion channels. Moreover, PQR620 demonstrated its potency to prevent cancer cell growth in an NTRC 44 cancer cell line panel, resulting in a 10log(IC50) of 2.86 (nM). Further pharmacological properties and in vivo efficacy of PQR620 are presented in detail in Ref. [3]. The preparation of PQR620 was optimized towards a robust synthetic route involving only 4 steps, allowing for a rapid access to quantities required for pre-clinical testing. In conclusion, PQR620 inhibits mTOR potently and selectively, and shows anti-tumor effects in vitro and in vivo. PQR620 is currently in pre-clinical development. [1] M. Laplante, D. Sabatini, Cell 2012, 149, 274-293. [2] Z. Z. Chong, Y. C. Shang, L. Zhang, S. Wang, K. Maiese, Oxid. Med. Cell. Longev. 2010, 3, 374–391. [3] F. Beaufils, D. Rageot, A. Melone, A. M. Sele, M. Lang, J. Mestan, R. A. Ettlin, P. Hillmann, V. Cmiljanovic, C. Walter, E. Singer, H. P. Nguyen, P. Hebeisen, D. Fabbro, M. P. Wymann, “Pharmacological characterization of the selective, orally bioavailable, potent mTORC1/2 inhibitor PQR620” presented at AACR Annual Meeting 2016, April 16-20, New Orleans, Louisiana, USA. Citation Format: Florent Beaufils, Denise Rageot, Anna Melone, Marc Lang, Jürgen Mestan, Vladimir Cmiljanovic, Petra Hillmann, Paul Hebeisen, Doriano Fabbro, Matthias P. Wymann. Structure-activity relationship studies, synthesis, and biological evaluation of PQR620, a highly potent and selective mTORC1/2 inhibitor. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1336.

Introduction The PI3K-delta idelalisib is among the most promising novel agents for lymphomas, but certain patients present a primary resistant disease or relapse after an initial response. Here, we studied the dual PI3K/MTOR inhibitor PQR309 in lymphoma cell lines that were resistant to idelalisib. Methods IC50 values were calculated with the MTT assay (72h) for 40 lymphoma cell lines. Gene expression profiling was done with Illumina HumanHT12 Expression BeadChips, data mining with Limma, GSEA and LINCSCLOUD. Results PQR309 and idelalisib showed only a partially overlapping pattern of activity (R = 0.6). While no cell line was sensitive to idelalisib and not to PQR309, 10 cell lines were sensitive to both compounds and 7 were sensitive only to PQR309. Idelalisib median IC50 was 28 nM (95%CI; 13-147) in the PQR309/idelalisib group and 13.4 μM (7.2-16.7 μM) in the PQR309-only (P 0.0006). PQR309 median IC50 was 113 nM (33-166 nM) in PQR309/idelalisib sensitive and 193 nM (111-372 nM) in the PQR309-only sensitive cells (P 0.03). No differences between the two groups were observed in terms of histology, diffuse large B cell lymphoma cell of origin, MYC deregulation, TP53 inactivation, BCL6 or BCL2 translocations. The gene expression signature of the PQR309/idelalisib sensitive cell lines was enriched of genes involved in IFN signaling, IL6/Jak/Stat3 signaling, oxidative phosphorylation, PI3K/MTOR signaling, chemokines signaling and proteasome (GSEA FDR Conclusions. The dual PI3K/MTOR inhibitor PQR309 was active in a subset of mature B cell lymphoma cell lines bearing a primary resistance to the PI3K-delta inhibitor idelalisib and specific gene expression features. Expression of SOX4 and CD24 appear worth of validation on clinical specimens derived from prospectively treated patients. Citation Format: Tarantelli Chiara, Eugenio Gaudio, Ivo Kwee, Alberto Arribas, Andrea Rinaldi, Elena Bernasconi, Luciano Cascione, Petra Hillmann, Anastasios Stathis, Laura Carrassa, Massimo Broggini, Georg Stussi, Doriano Fabbro, Emanuele Zucca, Vladimir Cmiljanovic, Francesco Bertoni. The dual PI3K/MTOR inhibitor PQR309 is active in mature B cell lymphoma cell lines bearing resistance to the PI3K-delta inhibitor idelalisib and specific gene expression features. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 380.

Introduction PQR309 is a novel oral balanced dual pan-PI3K and mTOR inhibitor currently in clinical development for the treatment of solid tumors and hematological malignancies. Eighty mg PQR309 given once daily (q.d.) has been established as the MTD in patients with advanced solid cancers. This dose and regimen was associated with plasma concentrations that were pharmacologically active in pre-clinical experiments. However, there is emerging evidence that continuous inhibition of PI3K/mTOR may not be needed to achieve the full effect of PQR309 on tumor growth inhibition and therefore further intermittent dosing regimens will be explored. Methods In vivo xenograft studies in nude male rats bearing PC3-derived tumors were conducted with continuous and intermittent dosing schedules to estimate effective plasma concentrations. Pharmacokinetic (PK) data from cancer patients were used to establish a 2-compartment PK model with first order absorption. The model was applied to simulate PK profiles after various intermittent dosing schedules including 2 daily administrations followed by a 5 day wash-out period in a 7 day cycle (2 days ON/5 days OFF) and a regimen with administrations on days 1 and 4 in a 7 day cycle (eg MON/THUR). Results A maximum plasma concentration (Cmax) of 800-1200ng/mL PQR309 and an impulse interval of 72 hours or less was associated with maximum effect in the rat xenograft model. In rats PQR309 is rapidly eliminated from plasma but in humans the compound has an elimination half-life of about 40 hours and accumulates upon multiple dosing. The applied model predicts that PQR309 administration given 2 days ON/5 days OFF will build up drug exposure to reach levels that strongly inhibit the targeted signalling pathways. During the 5 day wash-out period, PQR309 levels will decrease significantly, thereby reducing the probability of adverse events. For the alternative dosing regimen MON/THUR, the model predicts a sharp Cmax lasting for a few hours followed by a decrease in drug levels over the following 3 or 4 days, thus minimizing accumulation and drug exposure that could lead to adverse events. Conclusions Both intermittent regimens are expected to strongly inhibit the targeted signalling pathways with high transient concentrations around Cmax followed by wash-out periods for healthy tissue recovery to optimize the benefit/risk of the compound. These regimens are currently being explored in clinical studies. Citation Format: Karin Jorga, Debora Schmitz, Natasa Cmiljanovic, Doriano Fabbro, Sasa Dimitrijevic. Exploring intermittent dosing schedules for the Pan PI3K/mTor inhibitor PQR309. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 378.

RET/PTC rearrangements are one of the genetic hallmarks of papillary thyroid carcinomas. RET/PTC oncoproteins lack extracellular or transmembrane domains, and activation takes place through constitutive dimerization mediated through coiled-coil motifs in the NH2 terminus of the chimeric protein. Based on the observation that the epidermal growth factor receptor (EGFR) kinase inhibitor PKI166 decreased RET/PTC kinase autophosphorylation and activation of downstream effectors in thyroid cells, despite lacking activity on the purified RET kinase, we proceeded to examine possible functional interactions between RET/PTC and EGFR. Conditional activation of RET/PTC oncoproteins in thyroid PCCL3 cells markedly induced expression and phosphorylation of EGFR, which was mediated in part through mitogen-activated protein kinase signaling. RET and EGFR were found to coimmunoprecipitate. The ability of RET to form a complex with EGFR was not dependent on recruitment of Shc or on their respective kinase activities. Ligand-induced activation of EGFR resulted in phosphorylation of a kinase-dead RET, an effect that was entirely blocked by PKI166. These effects were biologically relevant, as the EGFR kinase inhibitors PKI166, gefitinib, and AEE788 inhibited cell growth induced by various constitutively active mutants of RET in thyroid cancer cells as well as NIH3T3 cells. These data indicate that EGFR contributes to RET kinase activation, signaling, and growth stimulation and may therefore be an attractive therapeutic target in RET-induced neoplasms. [Cancer Res 2008;68(11):4183–91]

Phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR) signaling is key to the control of many physiological and pathophysiological processes, and promotes cancer and inflammatory disease. Therefore, targeting of PI3K and/or mTOR pathways is currently explored in numerous clinical studies. PQR309 is a novel, brain penetrant, potent and selective pan-PI3K/mTOR inhibitor with PK properties suitable for once a day oral dosing in humans. Structure activity relationship studies for PI3K and mTOR interactions are presented, including X-Ray analysis of PI3Kgamma co-crystal structures, modeling of PI3Kalpha and mTOR structures, and chemical derivatization. This led to the identification of PQR309 as a potent pan-PI3K and moderate mTOR inhibitor. PQR309 displays excellent selectivity versus PI3K-related lipid kinases (PIKKs) and protein kinases (KINOMEscan), as well as excellent selectivity versus unrelated targets (Cerep expresSProfile). PQR309 features excellent cell permeability, and was characterized as a BCS class II compound due to its limited water solubility (40 μM). Moreover, PQR309 is not a substrate for P-glycoprotein 1 (P-gp). In A2058 melanoma cells PQR309 demonstrated inhibition of protein kinase B (PKB/Akt; pS473) and ribosomal protein S6 (S6, pSer235/236) phosphorylation with IC50 values of 0.13 μM and 0.58 μM, respectively. In IGF-stimulated MCF7 breast cancer cells, PQR309 at 1 μM inhibited phosphorylation of downstream substrates of PI3K including PKB/Akt, S6, p70S6 kinase, GSK3 and Bad by 60-95%. PQR309 inhibited proliferation of all 58 cell lines of the NCI60 panel (GI50 from 50 to 3300 nM), of the NTRC Oncoline panel (44 cell lines, GI50 from 100-6700 nM) and of a lymphoma cell line panel (40 lymphoma cell lines, GI50 from 25-1740 nM). A concise 4-step synthetic process utilizing a novel protective group strategy provides a robust and scalable supply of PQR309 for clinical trials. In summary, PQR309 is a novel, potent, dual pan-PI3K/mTOR inhibitor with a balanced PI3K vs. mTOR profile, and displays excellent physico-chemical and pharmacological properties. The safety profile of PQR309 is currently addressed in Phase I clinical studies. Citation Format: Vladimir Cmiljanovic, Natasa Cmiljanovic, Romina Marone, Florent Beaufils, Xuxiao Zhang, Marketa Zvelebil, Paul Hebeisen, Marc Lang, Juergen Mestan, Anna Melone, Thomas Bohnacker, Eugenio Gaudio, Chiara Tarantelli, Francesco Bertoni, Reto Ritschard, Vincent Pretre, Andreas Wicki, Doriano Fabbro, Petra Hillmann, Roger Williams, Bernd Giese, Matthias P. Wymann. PQR309: Structure-based design, synthesis and biological evaluation of a novel, selective, dual pan-PI3K/mTOR inhibitor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2664. doi:10.1158/1538-7445.AM2015-2664

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is frequently activated in tumors and promotes oncogenic cell transformation, proliferation and tumor growth. PQR309, a novel dual inhibitor of PI3K and mTOR, is currently in Phase I clinical development in cancer patients. PQR309 binds potently and specifically to the ATP binding pocket of all PI3K class I isoforms and mTORC1/2, attenuates PI3K signaling and inhibits tumor cell growth. The preclinical pharmacological and toxicological characterization of PQR309 is presented here. Methods: PQR309 pharmacokinetics/-dynamics (PK/PD) were investigated in rats and mice. Tissue samples from plasma, brain and liver were analyzed by LC/MS detecting PQR309 distribution as well as blood insulin and glucose. Toxicological studies were performed in rats and dogs. Effects on neurological, hematopoietic, respiratory, lymphoid, reproductive and cardiovascular system as well as general health were monitored. The metabolic fate of PQR309 was analyzed in rat, dog and human hepatocytes. Results: PQR309 PK studies in rats, mice and dogs revealed dose-proportional PK, both PO and IV, with a half-life of 5-8 hours in plasma, brain and liver, allowing for once a day oral application. As on-target effect, increase of blood insulin and glucose could be observed within hours after oral dosage in rats, which makes both molecules suitable as PD markers. In in vivo PC-3 rat tumor xenograft models, PQR309 effectively inhibited PI3K signaling in tumors and reduced tumor growth at 10 mg/kg oral dosing. Preclinical toxicity testing showed no signs of cardiotoxicity (including lack of hERG binding), phototoxicity (3T3 NRU test) or mutagenicity (AMES test) for PQR309. No marked effect on CYP450 activity was observed making PQR309 a good combination partner in cancer therapy. As for other PI3K inhibitors, PQR309 leads at elevated doses to a fully reversible loss of body weight and appetite in rats and dogs. No further significant adverse events were observed when testing PQR309 for 28 days in these species. Conclusions: PQR309 potently inhibits class I PI3K isoforms and mTORC1/2 and shows anti-tumor effects in vitro and in vivo. The physico-chemical properties of PQR309 result in good oral bioavailability and equal distribution between plasma and brain. Pre-clinical data led to initiation of a Phase I clinical study of PQR309 in solid tumors. Citation Format: Vladimir Cmiljanovic, Robert A. Ettlin, Florent Beaufils, Walter Dieterle, Petra Hillmann, Juergen Mestan, Anna Melone, Thomas Bohnacker, Marc Lang, Natasa Cmiljanovic, Bernd Giese, Paul Hebeisen, Matthias P. Wymann, Doriano Fabbro. PQR309: A potent, brain-penetrant, dual pan-PI3K/mTOR inhibitor with excellent oral bioavailability and tolerability. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4514. doi:10.1158/1538-7445.AM2015-4514

Due to its central role in growth, proliferation, survival and migration, phosphoinositide 3-kinase (PI3K) is considered as an important drug target in oncology (1). BKM120 is one of the clinically most advanced PI3K inhibitors (PI3Ki), and is currently listed in more than 80 clinical studies aimed at attenuating tumour progression. As an off-target effect, BKM120 was reported to disrupt microtubules (MT) at concentrations around 1 μM (2). Here, we elucidate in detail the structural factors defining PI3K- and tubulin-binding of BKM120, and present a pure PI3K inhibitor (PQR309) and a potent MT disruptor (MTD147) differing from BKM120 by only 1 Dalton. Separation of PI3Ki and MT disruption activities of BKM120 allowed profiling of BKM120 against PQR309 and MTD147: cellular growth profiles of PQR309 clustered with other PI3Ki such as GDC0941/GDC0980, while BKM120 matched MTD147. Both yielded a G2/M cell cycle arrest with typical histone3 phosphorylation. Accumulation of G2/M arrested cells was already evident at concentrations yielding 50% growth inhibition. Interestingly, BKM120 concentrations for 50% cell growth inhibition (with evident G2/M arrest) ranged below or within its reported AUC0-24 levels at day 8 in patient plasma (3,4). This result implies that the two activities of BKM120 cannot be separated, thus complicating the understanding of drug action and impacting on the rational of combination therapies at relevant drug doses. Using X-ray crystallography we found that BKM120 binds to the colchicine pocket on β-tubulin. This study further highlights the importance of the pyrimidine core orientation for tight tubulin binding. Interestingly, activities of regio-isomers of the pyrimidine core are inversed for PI3Ki and tubulin association, and modulate binding by a factor of >30x. Finally, a combination of biochemical, cellular and structural data suggests an inverted orientation of BKM120 in the catalytic cleft of PI3K as previously proposed (6). In summary, the dissection of BKM120 functions allows reassessment of its dominant activity, to increase drug safety, and to flexibly control PI3K and/or MT targeting in combination therapy. 1. M. P. Wymann, R. Schneiter, Nat Rev Mol Cell Biol 9, 162 (2008).; 2. S. M. Brachmann et al., Mol Cancer Ther 11, 1747 (2012). 3. J. C. Bendell et al., J Clin Oncol 30, 282 (2012). 4. C. Saura et al., Clin Cancer Res 20, 1935 (2014). 5. A. E. Prota et al., Science 339, 587 (2013). 6. S. M. Maira et al., Mol Cancer Ther 11, 317 (2012). Citation Format: Thomas Bohnacker, Florent Beaufils, Andrea E. Prota, John E. Burke, Anna Melone, Alison J. Inglis, Ludovico Fusco, Vladimir Cmiljanovic, Natasa Cmiljanovic, Denise Rageot, Katja Bargsten, Gonzalo Saez-Calvo, Olivier Pertz, Amol B. Aher, Anna Akhmanova, Fernando J. Diaz, Doriano Fabbro, Marketa Zvelebil, Roger L. Williams, Michel O. Steinmetz, Matthias P. Wymann. BKM120-mediated G2 arrest: Structural and functional segregation of off-target action and PI3K inhibition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 671. doi:10.1158/1538-7445.AM2015-671

PQR309 is a novel oral PI3K/mTOR inhibitor, being now evaluated as single agent in a phase I study for solid tumors patients (NCT01940133). Here, we present the activity of the compound in lymphoma pre-clinical models, also integrating response data with genomic features. Methods. IC50s were calculated with the MTT assay at 72h on 40 cell lines [27 diffuse large B-cell lymphoma (DLBCL), 10 mantle cell lymphoma (MCL), 3 splenic marginal zone lymphoma (SMZL)] treated with increasing doses of PQR309, a second dual PI3K/mTOR inhibitor (GDC0980) and the PI3Kdelta inhibitor Idelalisib. Gene expression profiling (GEP) was performed with Illumina HumanHT-12 Expression BeadChips. Results. PQR309 had potent anti-proliferative activity in most of the cell lines. Median IC50 were 166 nM in DLBCL (95%CI 128-343 nM), 235 in MCL (155-381), 214 in SMZL (188-304). Activated B-cell like (ABC) and germinal center B-cell like (GCB) DLBCL subtypes were equally sensitive. PQR309 and GDC0980 presented a highly correlated pattern of anti-proliferative activity (R = 0.9). Idelalisib appeared significantly less active, with a pattern of sensitive cell lines less correlated with PQR309 (R = 0.6) or GDC0980 (R = 0.6). Apoptosis after PQR309 (500 nM, 72h) was limited to 1/7 of cell lines. GEP was performed on 8 DLBCL cell lines (4 GCB, 4 ABC) after treatment with DMSO or PQR309 (1 mcM) for 4, 8 and 12h. PQR309 affected, in a time-dependent manner, relevant biologic pathways in both subtypes. Down-regulated transcripts were enriched of MYC targets, genes involved in NFKB/MYD88/BCR/IFN signaling, apoptosis, DNA damage and proteasome. Transcripts up-regulated were enriched of genes involved in cell cycle and senescence, up-regulated after MYD88 silencing, down-regulated by PI3K, involved in packaging of telomere, in autophagosome, up-regulated by inhibitors of HDAC, BET Bromodomain and JAK2. CXCR4, PIM1, PIM2, YPEL5 (up-regulated), LYAR, CCDC86, DDX21, HSPA8, STIP1, and PAK1IP1 (down-regulated) were among the genes changing after PQR309 treatment in more than one time-point or DLBCL cell-type. To identify markers of resistance we looked for transcripts differently regulated between cell lines with higher or lower sensitivity to PQR309 and we also compared baseline GEP between very sensitive (IC50 400 nM). Transcripts more expressed in sensitive cells were significantly enriched of genes involved in BCR pathway/signaling, kinases regulation, and immune system. Transcripts associated with less sensitive cells were enriched of members of proteasome pathway, oxidative phosphorylation, translation initiation. PQR309 (1 mcM) was able to inhibit IgM-stimulation induced p-AKT(Ser 473) in 3/3 DLBCL and 3/3 MCL cells. Conclusions. PQR309 showed strong anti-proliferative activity in lymphomas and GEP identified affected biologic pathways and features possibly associated with response to the molecule. Citation Format: Chiara Tarantelli, Eugenio Gaudio, Ivo Kwee, Andrea Rinaldi, Elena Bernasconi, Luciano Cascione, Petra Hillmann, Anastasios Stathis, Laura Carrassa, Massimo Broggini, Georg Stussi, Doriano Fabbro, Florent Beaufils, Anna Melone, Thomas Bohnacker, Matthias P. Wymann, Andreas Wicki, Emanuele Zucca, Vladimir Cmiljanovic, Francesco Bertoni. Pre-clinical activity and mechanism of action of the novel dual PI3K/mTOR inhibitor PQR309 in B-cell lymphomas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2652. doi:10.1158/1538-7445.AM2015-2652

Mutations in the receptor tyrosine kinase FLT3 occur frequently in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Small molecules that selectively inhibit FLT3 kinase activity induce apoptosis in blasts from AML patients with FLT3 mutations and prolong survival in animal models of FLT3-induced myeloproliferative disease. A spectrum of structurally different small molecules with activity against FLT3 have been described, and their efficacy for treatment of AML and ALL is now being investigated in clinical trials. Here, we describe the results of an in vitro screen designed to identify mutations in the ATP-binding pocket of FLT3 that confer resistance to tyrosine kinase inhibitors. Mutations at four different positions (Ala-627, Asn-676, Phe-691, and Gly-697) were identified that confer varying degrees of resistance to PKC412, SU5614, or K-252a. FLT3 proteins mutated at Ala-627, Asn-676, or Phe-691 remained sensitive to higher concentrations of the inhibitors, but the G697R mutation conferred high-level resistance to each of these inhibitors as well as to six additional experimental inhibitors. These data provide insights into potential mechanisms of acquired resistance of FLT3 to small molecule inhibitors and indicate that the G697R mutation may be a clinically problematic resistance mutation that warrants proactive screening for additional inhibitors.

Aberrant epidermal growth factor receptor (EGFR) and ErbB2 expression are associated with advanced disease and poor patient prognosis in many tumor types (breast, lung, ovarian, prostate, glioma, gastric, and squamous carcinoma of head and neck). In addition, a constitutively active EGFR type III deletion mutant has been identified in non-small cell lung cancer, glioblastomas, and breast tumors. Hence, members of the EGFR family are viewed as promising therapeutic targets in the fight against cancer. In a similar vein, vascular endothelial growth factor (VEGF) receptor kinases are also promising targets in terms of an antiangiogenic treatment strategy. AEE788, obtained by optimization of the 7H-pyrrolo[2,3-d]pyrimidine lead scaffold, is a potent combined inhibitor of both epidermal growth factor (EGF) and VEGF receptor tyrosine kinase family members on the isolated enzyme level and in cellular systems. At the enzyme level, AEE788 inhibited EGFR and VEGF receptor tyrosine kinases in the nm range (IC(50)s: EGFR 2 nm, ErbB2 6 nm, KDR 77 nm, and Flt-1 59 nm). In cells, growth factor-induced EGFR and ErbB2 phosphorylation was also efficiently inhibited (IC(50)s: 11 and 220 nm, respectively). AEE788 demonstrated antiproliferative activity against a range of EGFR and ErbB2-overexpressing cell lines (including EGFRvIII-dependent lines) and inhibited the proliferation of epidermal growth factor- and VEGF-stimulated human umbilical vein endothelial cells. These properties, combined with a favorable pharmacokinetic profile, were associated with a potent antitumor activity in a number of animal models of cancer, including tumors that overexpress EGFR and or ErbB2. Oral administration of AEE788 to tumor-bearing mice resulted in high and persistent compound levels in tumor tissue. Moreover, AEE788 efficiently inhibited growth factor-induced EGFR and ErbB2 phosphorylation in tumors for72 h, a phenomenon correlating with the antitumor efficacy of intermittent treatment schedules. Strikingly, AEE788 also inhibited VEGF-induced angiogenesis in a murine implant model. Antiangiogenic activity was also apparent by measurement of tumor vascular permeability and interstitial leakage space using dynamic contrast enhanced magnetic resonance imaging methodology. Taken together, these data indicate that AEE788 has potential as an anticancer agent targeting deregulated tumor cell proliferation as well as angiogenic parameters. Consequently, AEE788 is currently in Phase I clinical trials in oncology.

PI3Ks are lipid kinases that control signaling pathways involved in cell proliferation, motility, cell death and cell invasion. Class I PI3K contains four isoforms, p110α, p110α, p110α and p110α which carry out non redundant signaling functions. The ≤ and ≤ isoforms are ubiquitously expressed, whereas the ≤ and ≤ isoforms are expressed primarily in lymphocytes and engaged in the regulation of immune responses. A gain of function in PI3K signaling is common to many types of human cancer, specifically mutations in PIK3CA which are found in more than 30% of various solid tumor types, including, breast, endometrium, bladder, colorectal cancers as well as lung cancers. As these mutations constitutively activate the lipid kinase activity of the protein, the cancer-specific mutants of p110α appear to be ideal therapeutic targets for anticancer drug development. p110α isoform specific low molecular weight inhibitors could be efficacious against tumors harboring p110alpha mutations and provide an improved safety profile compared to current pan-PI3K modulators. The 2-aminothiazole scaffold proved to be an excellent starting point for the development of potent PI3K inhibitors. Depending on the substitution pattern good PI3Kalpha selectivity can be achieved. Systematic modification of key residues and further optimization of the drug-like and PK properties have led to the identification of NVP-BYL719, a potent and selective PI3Kalpha inhibitor with a promising biological activity. SAR leading to the discovery of NVP-BYL719 and the structural basis for the PI3Kalpha selectivity will be discussed. 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 1922. doi:1538-7445.AM2012-1922