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PDF file - 500KB, Supplemental Figure 1. Upregulation of hMOB3 in GBM and characterization of hMOB3 antibody and shRNAs.

PDF file - 323KB, Supplemental Figure 2. hMOB3 specifically interacts with MST1.

PDF file - 280KB, Supplemental Figure 3. hMOB3 negatively regulates MST1 apoptotic cleavage.

New therapeutic targets are needed that circumvent inherent therapeutic resistance of glioblastoma multiforme (GBM). Here, we report such a candidate target in the uncharacterized adaptor protein hMOB3, which we show is upregulated in GBM. In a search for its biochemical function, we found that hMOB3 specifically interacts with MST1 kinase in response to apoptotic stimuli and cell–cell contact. Moreover, hMOB3 negatively regulated apoptotic signaling by MST1 in GBM cells by inhibiting the MST1 cleavage-based activation process. Physical interaction between hMOB3 and MST1 was essential for this process. In vivo investigations established that hMOB3 sustains GBM cell growth at high cell density and promotes tumorigenesis. Our results suggest hMOB3 as a candidate therapeutic target for the treatment of malignant gliomas. Cancer Res; 74(14); 3779–89. ©2014 AACR.

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Background PI3K/mTOR inhibition leads to apoptosis of NOTCH1-mutant head and neck squamous cell carcinoma (HNSCC) cells. We tested the efficacy of the PI3K/mTOR inhibitor bimiralisib in patients with NOTCH1-mutant HNSCC. Methods Patients with recurrent/metastatic NOTCH1-mutant HNSCC who had progressed during chemotherapy and immunotherapy received bimiralisib until unacceptable toxicity or progression. To assess whether NOTCH1 mutations can be detected in blood, we measured circulating tumor DNA (ctDNA). To assess activated NOTCH1 protein levels, we quantitated cleaved NOTCH1 (cl-NOTCH) by immunohistochemistry. Results Eight patients were treated, and 6 were evaluable for response. The objective response rate was 17%. For all 8 patients, median progression-free and overall survival was 5 and 7 months, respectively. Bimiralisib was well tolerated, with expected hyperglycemia. Pharmacokinetic values were consistent with published studies. NOTCH1 mutations were detected in 83.3% of ctDNA. Staining for tumor cl-NOTCH1 was negative. The trial closed early due to sponsor insolvency. Conclusion Although the trial was small, outcomes with bimiralisib were better than the historical standard of care; Results will need to be confirmed in a larger trial. The lack of cl-NOTCH1 was consistent with loss-of-function mutations and validated our mutation function algorithm. The ability to detect NOTCH1 mutations in blood will help future studies. (ClinicalTrials.gov Identifier: NCT03740100).

Bimiralisib is an orally bioavailable pan-phosphatidylinositol 3-kinase and mammalian target of rapamycin inhibitor which has shown activity against lymphoma in preclinical models. This phase I/II study evaluated the response rate to bimiralisib at 2 continuous dose levels (60 mg and 80 mg) in patients with relapsed/refractory lymphoma. Fifty patients were enrolled and started treatment. The most common histologies were diffuse large B-cell lymphoma (n = 17), follicular lymphoma (n = 9), T-cell lymphoma (n = 8), and others (mostly indolent). Patients had been treated with a median of 5 prior lines of treatment and 44% were considered refractory to their last treatment. Mean duration of treatment (and standard deviations) with 60 mg once daily (o.d.) was 1.3 ± 1.2 months, and with 80 mg o.d. 3.7 ± 3.9 months. On an intention to treat analysis, the overall response rate was 14% with 10% achieving a partial response and 4% a complete response. Thirty-six percent of patients were reported as having stable disease. No dose-limiting toxicities were observed during the phase I portion of the study. Overall, 70% of patients had a grade 3 treatment emergent adverse events (TEAE) and 34% had a grade 4 TEAE; 28% of patients discontinued treatment due to toxicity. The most frequent TEAEs grade ≥3 was hyperglycemia (24%), neutropenia (20%), thrombocytopenia (22%), and diarrhea (12%). Per protocol, hyperglycemia required treatment with oral antihyperglycemic agents in 28% and with insulin in 14%. At 60 mg or 80 mg continuous dosing, bimiralisib showed modest efficacy with significant toxicity in heavily pretreated patients with various histological subtypes of lymphoma.

TPS6590 Background: Effective targeted therapies are needed for HNSCC that is lethal despite recent advances with immunotherapy. A major challenge to personalize treatment is that most genomic alterations are in tumor suppressors, including NOTCH1 that is mutated in ~20% of HNSCC. We recently published that HNSCC cell lines harboring NOTCH1 LOF mutations undergo cell death in vivo and in vitro following PI3K inhibition, in contrast to PIK3CA mutant cell lines that merely undergo cell cycle arrest when exposed to the same drugs. Based on these results we initiated a novel genomic biomarker-driven phase II clinical trial treating NOTCH1 mutant HNSCC pts with the dual PI3K/mTOR inhibitor bimiralisib (PQR309). Methods: The primary objective is to determine the objective response rate (ORR) of recurrent/metastatic HNSCC harboring NOTCH1 LOF mutations to bimiralisib. Pts who have already received standard platinum chemotherapy and immunotherapy will receive bimiralisib orally twice per wk unless progression or intolerable toxicity occurs. Tumors will be evaluated using RECIST q 6 wks. A Simon’s optimal two-stage design is used. To have 80% power to detect an ORR of 30%, (one-sided α = 0.05, β = 0.20) 10 pts will be enrolled in the first stage. If ≤1 pts respond, the trial will be closed for futility. If ≥2 pts have an OR, the study will enroll an additional 19 pts in the second stage. The null hypothesis (ORR ≤ 10%) will be rejected if ≥ 6 in 29 pts have an OR. Seven pts have enrolled. The algorithm for determining NOTCH1 mutation function is based on the patterns of mutations in HNSCC vs. leukemia where mutations are activating. It may be difficult to determine whether NOTCH1 mutations are homo- or heterozygous due to normal cell contamination. Therefore, levels of activated NOTCH1 in pretreatment tumors may be assessed by IHC with an antibody against activated NOTCH1 (NICD). In parallel with the trial, to further confirm NOTCH1 LOF, we can use site-directed mutagenesis to re-create NOTCH1 mutations from trial pts that will then be introduced into NOTCH1-null cell lines to assay for NICD and growth inhibition with culture on NOTCH1 ligand. All pts will have serial collection of blood for pharmacokinetics and for ctDNA to examine clonal evolution associated with acquired resistance. Samples with high NOTCH1 mutation ctDNA VAF will be analyzed by WES and compared with pretreatment tissue. In the second stage, IHC and WES may be performed on pre- and post- treatment (day 15 and progression) tissue to examine pharmacodynamics and mechanisms of resistance. Clinical trial information: NCT03740100 .

Background: Bimiralisib is a balanced dual panPI3K/mTOR inhibitor, which demonstrated anti-cancer activity in a number of preclinical models. Pharmacokinetic (PK) data suggested that intermittent targeting of the PI3K/mTOR pathway could be preferable to continuous daily dosing. Preclinical models in squamous cell head and neck cancer (SCCHN) demonstrated that NOTCH1 Loss of Function (LoF) mutations were associated with efficacy of bimiralisib and other PI3K inhibitors. Methods: We conducted a first-in-human dose-escalation study (3+3 design) to identify the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), dose-limiting toxicities (DLT) and overall safety (CTCAE v4) of bimiralisib administered either as a continuous (80 mg – 120 mg daily) or one of two intermittent schedules (schedule A: twice weekly 80 mg – 200 mg on Day 1 and 2, or schedule B: twice weekly 80mg – 200 mg on Day 1 and 4) until disease progression or unacceptable adverse events (AEs). Eligible patients had histologically confirmed solid cancers refractory to standard therapies, ECOG 12 weeks, adequate bone marrow, liver, and renal functions, HgbA1c 6 months was observed in five pts (23.8%) in continuous schedule, 12 (48%) in intermittent schedule A, and 13 (54.2%) in intermittent schedule B. Results on patients, who consented to the serial circulating tumor DNA collection will be presented. Conclusions: Bimiralisib was well tolerated and RP2D of 140 mg given orally twice weekly on Days 1 and 2 was selected for further studies. In agreement with our preclinical models, there was an encouraging activity in a SCCHN patient with NOTCH1 LoF mutation and this observation is now being validated in a proof-of-concept phase 2 study (NCT03740100). Citation Format: Filip Janku, Faye M. Johnson, Mateusz Opyrchal, Afshin Dowlati, Cinta Hierro, Martin Forester, Sarah P. Blagden, Andreas Wicki, Debora Schmitz, Alex A. Adjei. Oral dual PI3K/mTOR inhibitor bimiralisib demonstrates tolerability and a signal of activity in head and neck squamous cell cancer with NOTCH1 loss-of-function mutation [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B109. doi:10.1158/1535-7163.TARG-19-B109

Summary Background Phosphorylation of the transcriptional coactivator YAP1 is a key event in defining Hippo signaling outputs. Previous studies demonstrated that phosphorylation of YAP1 at serine 127 (S127) sequesters YAP1 in the cytoplasm and consequently inhibits YAP1 transcriptional activity. Mammalian tissue-culture experiments suggest that downstream of MST1/2 signaling, LATS1/2 function as YAP1-S127 kinases. However, studies of Mst1/2 knockout mouse models revealed that the identity of the physiological YAP1-S127 kinase(s) in certain tissues, such as the intestine, remains unknown. Results We show that mammalian NDR1/2 kinases phosphorylate YAP1 on S127 and thereby negatively regulate YAP1 activity in tissue-cultured cells. By studying NDR1/2-deficient mice, we demonstrate the in vivo relevance of NDR1/2-mediated regulation of YAP1. Specifically, upon loss of NDR1/2 in the intestinal epithelium, endogenous S127 phosphorylation is decreased whereas total YAP1 levels are increased. Significantly, ablation of NDR1/2 from the intestinal epithelium renders mice exquisitely sensitive to chemically induced colon carcinogenesis. Analysis of human colon cancer samples further revealed that NDR2 and YAP1 protein expression are inversely correlated in the majority of samples with high YAP1 expression. Collectively, we report NDR1/2 as physiological YAP1-S127 kinases that might function as tumor suppressors upstream of YAP1 in human colorectal cancer. Conclusions We establish mammalian NDR1/2 as bona fide kinases that target YAP1 on S127 in vitro and in vivo. Our findings therefore have important implications for a broad range of research efforts aimed at decoding and eventually manipulating YAP1 biology in cancer settings, regenerative medicine, and possibly also noncancer human diseases., Graphical Abstract, Highlights • Mammalian NDR kinases phosphorylate YAP1 on serine 127 • Phosphorylation of YAP1 by NDR kinases regulates YAP1 activity in vivo • NDR kinases function as tumor suppressors in the intestinal epithelium • Ndr knockout mice represent the first animal model of a direct S127 kinase, Phosphorylation of the Hippo pathway effector YAP1 contributes to tissue homeostasis. However, the identity of the YAP1 kinase in the intestine remains unknown. Here, Zhang et al. report NDR as a physiological YAP1 kinase, restricting YAP1’s activity in the intestine and hence establishing the first mouse model of a direct YAP1-S127 kinase.

The serine and threonine kinase MST1 is the mammalian homolog of Hippo. MST1 is a critical mediator of the migration, adhesion, and survival of T cells; however, these functions of MST1 are independent of signaling by its typical effectors, the kinase LATS and the transcriptional coactivator YAP. The kinase NDR1, a member of the same family of kinases as LATS, functions as a tumor suppressor by preventing T cell lymphomagenesis, which suggests that it may play a role in T cell homeostasis. We generated and characterized mice with a T cell-specific double knockout of Ndr1 and Ndr2 (Ndr DKO). Compared with control mice, Ndr DKO mice exhibited a substantial reduction in the number of naive T cells in their secondary lymphoid organs. Mature single-positive thymocytes accumulated in the thymus in Ndr DKO mice. We also found that NDRs acted downstream of MST1 to mediate the egress of mature thymocytes from the thymus, as well as the interstitial migration of naive T cells within popliteal lymph nodes. Together, our findings indicate that the kinases NDR1 and NDR2 function as downstream effectors of MST1 to mediate thymocyte egress and T cell migration.

Summary Background Human MST/hSAV/LATS/hMOB tumor suppressor cascades are regulators of cell death and proliferation; however, little is known about other functions of MST/hMOB signaling. Mob1p, one of two MOB proteins in yeast, appears to play a role in spindle pole body duplication (the equivalent of mammalian centrosome duplication). We therefore investigated the role of human MOB proteins in centrosome duplication. We also addressed the regulation of human centrosome duplication by mammalian serine/threonine Ste20-like (MST) kinases, considering that MOB proteins can function together with Ste20-like kinases in eukaryotes. Results By studying the six human MOB proteins and five MST kinases, we found that MST1/hMOB1 signaling controls centrosome duplication. Overexpression of hMOB1 caused centrosome overduplication, whereas RNAi depletion of hMOB1 or MST1 impaired centriole duplication. Significantly, we delineated an hMOB1/MST1/NDR1 signaling pathway regulating centrosome duplication. More specifically, analysis of shRNA-resistant hMOB1 and NDR1 mutants revealed that a functional NDR/hMOB1 complex is critical for MST1 to phosphorylate NDR on the hydrophobic motif that in turn is required for human centrosome duplication. Furthermore, shRNA-resistant MST1 variants revealed that MST1 kinase activity is crucial for centrosome duplication whereas MST1 binding to the hSAV and RASSF1A tumor suppressor proteins is dispensable. Finally, by studying the PLK4/HsSAS-6/CP110 centriole assembly machinery, we also observed that normal daughter centriole formation depends on intact MST1/hMOB1/NDR signaling, although HsSAS-6 centriolar localization is not affected. Conclusions Our observations propose a novel pathway in control of human centriole duplication after recruitment of HsSAS-6 to centrioles.

SummaryHuman NDR1 and 2 (NDR1/2) are serine-threonine protein kinases in a subgroup of the AGC kinase family [1]. The mechanisms of physiological NDR1/2 activation and their function remain largely unknown. Here we report that Fas and TNF-α receptor stimulation activates human NDR1/2 by promoting phosphorylation at the hydrophobic motif (Thr444/442). Moreover, NDR1/2 are essential for Fas receptor-induced apoptosis as shown by the fact that NDR knockdown significantly reduced cell death whereas overexpression of the NDR1 kinase further potentiated apoptosis. Activation of NDR1/2 by death receptor stimulation is mediated by the tumor suppressor RASSF1A. Furthermore, RASSF1A-induced apoptosis largely depends on the presence of NDR1/2. Fas receptor stimulation promoted direct phosphorylation and activation of NDR1/2 by the mammalian STE20-like kinase 1 (MST1), a downstream effector of RASSF1A. Concurrently, the NDR1/2 coactivator MOB1 induced MST1-NDR-MOB1 complex formation, which is crucial for MST1-induced NDR1/2 phosphorylation upon induction of apoptosis. Our findings identify NDR1/2 as novel proapoptotic kinases and key members of the RASSF1A/MST1 signaling cascade.

Activation of immune cells has to be tightly controlled to prevent detrimental hyperactivation. In this regulatory process molecules of the C-type lectin-like family play a central role. Here we describe a new member of this family, CLEC12B. The extracellular domain of CLEC12B shows considerable homology to the activating natural killer cell receptor NKG2D, but unlike NKG2D, CLEC12B contains an immunoreceptor tyrosine-based inhibition motif in its intracellular domain. Despite the homology, CLEC12B does not appear to bind NKG2D ligands and therefore does not represent the inhibitory counterpart of NKG2D. However, CLEC12B has the ability to counteract NKG2D-mediated signaling, and we show that this function is dependent on the immunoreceptor tyrosine-based inhibition motif and the recruitment of the phosphatases SHP-1 and SHP-2. Using monoclonal anti-CLEC12B antibodies we found de novo expression of this receptor on in vitro generated human macrophages and on the human myelo-monocytic cell line U937 upon phorbol 12-myristate 13-acetate treatment, suggesting that this receptor plays a role in myeloid cell function.

New therapeutic targets are needed that circumvent inherent therapeutic resistance of glioblastoma multiforme (GBM). Here, we report such a candidate target in the uncharacterized adaptor protein hMOB3, which we show is upregulated in GBM. In a search for its biochemical function, we found that hMOB3 specifically interacts with MST1 kinase in response to apoptotic stimuli and cell–cell contact. Moreover, hMOB3 negatively regulated apoptotic signaling by MST1 in GBM cells by inhibiting the MST1 cleavage-based activation process. Physical interaction between hMOB3 and MST1 was essential for this process. In vivo investigations established that hMOB3 sustains GBM cell growth at high cell density and promotes tumorigenesis. Our results suggest hMOB3 as a candidate therapeutic target for the treatment of malignant gliomas. Cancer Res; 74(14); 3779–89. ©2014 AACR.

Background:PQR309 is an oral balanced, pan-PI3K, mTORC1 and mTORC2 inhibitor. It is in clinical development for the treatment of solid tumors and hematologic malignancies. 1st generation mTOR inhibitors inhibit the activity of mTOR within the TORC1 complex only with activation of TORC2 proposed as a putative resistance mechanism. PI3 kinase inhibition may reduce subsequent AKT activation which can bypass some effects of mTOR inhibition. Potent antiproliferative activity of PQR309 was previously demonstrated in lymphoma cell lines in vitro and in vivo. Maximum tolerated dose (MTD) of PQR309 in solid tumours was established at 80 mg using a continuous once daily dosing schedule (OD). Methods:We performeda modified 3+3 DE of PQR309, open label phase 1 trial with expansion, to evaluate safety, pharmacokinetics (PK) and efficacy. Patients with relapsed or refractory lymphoma (any sub-type, ECOG PS of 0-1) were treated in two sequential cohorts with escalating doses of PQR309 administered on an OD dosing schedule to assess the MTD of PQR309. The starting dose of PQR309 was 60mg OD. The dose limiting toxicity (DLT) period was the first cycle of treatment, 21 days (d). PK samples were obtained at predefined time points. Clinical efficacy was evaluated according to revised Cheson criteria. In the expansion phase, patients will be treated at the MTD as defined in the DE phase of the study. Results: 15 patients were enrolled between August 2015 and March 2016 and treated with 60mg (n=8) or 80mg (n=7) of PQR309. Demographics: 5F:10M; median age 60 (range: 34-75), median number of prior systemic treatments 5 (range: 1-8). Lymphoma indications are shown in Table 1. Mean duration on therapy was 39 days (range: 3-160). One patient with follicular lymphoma remains on treatment. Grade (G)3/4 drug-related AE were seen in 3 patients treated with 60mg: 1 G4 rhabdomyolysis, 1 G4 neutropenia, 1 G3 hyperglycemia and one patient who developed G3 anorexia and G4 sepsis. Four patients treated with 80mg developed G3/4 drug-related AEs: two patients developed G3 hyperglycemia, one patient developed G3 fatigue and G3 pneumonitis. No DLT was observed. Preliminary PK showed rapid absorption (Tmax 1-2h), dose proportionality for Cmax and AUC and an estimated T1/2 of around 50 hours, consistent with PQR309 studies in solid tumours that evaluated dose levels from 10 to 150 mg PQR309. Responses observed in each patient are shown in the table below. 4 patients were non-evaluable, 3 due to disease progression requiring cessation of study drug and one requiring steroid doses exceeding protocol defined criteria, all within the 21 day DLT assessment period. Conclusion:The MTD and recommended PQR309 dose for the expansion of the study was 80mg OD, in agreement with earlier dose-finding studies in solid tumours. Adverse event patterns were consistent with those seen in studies involing solid tumours. Hyperglycemia, a predicted on-target effect of PI3K/mTOR inhibition, was observed in the majority of patients, providing evidence of pharmacodynamic effects of PQR309. PK was dose-proportional. Encouraging clinical activity including a CR was observed. The study expansion is ongoing. Disclosures Collins: Takeda: Consultancy, Honoraria, Speakers Bureau. Eyre:GSK: Honoraria; Celgene: Other: Travel, Accomodation; Gilead: Honoraria, Other: Travel, Accomodation, Speakers Bureau; Takeda: Honoraria, Other: Travel, Speakers Bureau. Ivanova:PIQUR: Employment. Schmitz:PIQUR: Employment. Dimitrijevic:PIQUR: Employment. Dreyling:Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau.

A major approach in the field of mammalian cell biology is the manipulation of the expression of genes of interest in selected cell lines, with the aim to reveal one or several of the gene's function(s) using transient/stable overexpression or knockdown of the gene of interest. Unfortunately, for various cell biological investigations this approach is unsuitable when manipulations of gene expression result in cell growth/proliferation defects or unwanted cell differentiation. Therefore, researchers have adapted the Tetracycline repressor protein (TetR), taken from the E. coli tetracycline resistance operon(1), to generate very efficient and tight regulatory systems to express cDNAs in mammalian cells(2,3). In short, TetR has been modified to either (1) block initiation of transcription by binding to the Tet-operator (TO) in the promoter region upon addition of tetracycline (termed Tet-off system) or (2) bind to the TO in the absence of tetracycline (termed Tet-on system) (Figure 1). Given the inconvenience that the Tet-off system requires the continuous presence of tetracycline (which has a half-life of about 24 hr in tissue cell culture medium) the Tet-on system has been more extensively optimized, resulting in the development of very tight and efficient vector systems for cDNA expression as used here. Shortly after establishment of RNA interference (RNAi) for gene knockdown in mammalian cells(4), vectors expressing short-hairpin RNAs (shRNAs) were described that function very similar to siRNAs(5-11). However, these shRNA-mediated knockdown approaches have the same limitation as conventional knockout strategies, since stable depletion is not feasible when gene targets are essential for cellular survival. To overcome this limitation, van de Wetering et al.(12) modified the shRNA expression vector pSUPER(5) by inserting a TO in the promoter region, which enabled them to generate stable cell lines with tetracycline-inducible depletion of their target genes of interest. Here, we describe a method to efficiently generate stable human Tet-on cell lines that reliably drive either inducible overexpression or depletion of the gene of interest. Using this method, we have successfully generated Tet-on cell lines which significantly facilitated the analysis of the MST/hMOB/NDR cascade in centrosome(13,14) and apoptosis signaling(15,16). In this report, we describe our vectors of choice, in addition to describing the two consecutive manipulation steps that are necessary to efficiently generate human Tet-on cell lines (Figure 2). Moreover, besides outlining a protocol for the generation of human Tet-on cell lines, we will discuss critical aspects regarding the technical procedures and the characterization of Tet-on cells.

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.

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.

2560Background: PQR is an oral pan-PI3K, mTORC1/mTORC2 inhibitor in clinical development. Methods: A Phase I trial of PQR to evaluate safety, PK and PD in pts with advanced solid tumors was performed, using the standard “3+3” design. Pts with ECOG PS of 0-1 were treated with escalating doses of PQR administered on a once daily continuous dosing schedule (qd). The dose limiting toxicity (DLT) period was the first 21 days of treatment. PK samples were obtained at predefined time points. Blood samples for the evaluation of glucose, insulin and c-peptide as PD markers were obtained at multiple time points. Results: 16 pts (11F:5M) were enrolled as of November 30 2015 and treated at 3 doses of PQR (80, 100 and 120 mg) qd. Median duration of therapy was 50 days (range 7 – 255). Adverse events (AEs) in ≥ 50% pts included fatigue, hyperglycemia, rash, nausea, vomiting, diarrhea and weight loss. Drug related grade 3 AEs seen in more than 1 pt were fatigue, hyperglycemia, rash and elevated transaminases. DLT’s were...

e14101Background: PQR309 is an orally bioavailable, pan-PI3K, mTORC1 and mTORC2 inhibitor, in clinical development for the therapy of solid tumors and hematologic malignancies. The aim of this work...

MOB proteins are integral components of signaling pathways controlling important cellular processes, such as mitotic exit, centrosome duplication, apoptosis, and cell proliferation in eukaryotes. The human MOB protein family consists of six distinct members (human MOB1A [hMOB1A], -1B, -2, -3A, -3B, and -3C), with hMOB1A/B the best studied due to their putative tumor-suppressive functions through the regulation of NDR/LATS kinases. The roles of the other MOB proteins are less well defined. Accordingly, we characterized all six human MOB proteins in the context of NDR/LATS binding and their abilities to activate NDR/LATS kinases. hMOB3A/B/C proteins neither bind nor activate any of the four human NDR/LATS kinases. We found that both hMOB2 and hMOB1A bound to the N-terminal region of NDR1. However, our data suggest that the binding modes differ significantly. Our work revealed that hMOB2 competes with hMOB1A for NDR binding. hMOB2, in contrast to hMOB1A/B, is bound to unphosphorylated NDR. Moreover, RNA interference (RNAi) depletion of hMOB2 resulted in increased NDR kinase activity. Consistent with these findings, hMOB2 overexpression interfered with the functional roles of NDR in death receptor signaling and centrosome overduplication. In summary, our data indicate that hMOB2 is a negative regulator of human NDR kinases in biochemical and biological settings.

Defective apoptosis contributes to the development of various human malignancies. The kinases nuclear Dbf2-related 1 (NDR1) and NDR2 mediate apoptosis downstream of the tumor suppressor proteins RASSF1A (Ras association domain family member 1A) and MST1 (mammalian Ste20-like kinase 1). To further analyze the role of NDR1 in apoptosis, we generated NDR1-deficient mice. Although NDR1 is activated by both intrinsic and extrinsic proapoptotic stimuli, which indicates a role for NDR1 in regulating apoptosis, NDR1-deficient T cells underwent apoptosis in a manner similar to that of wild-type cells in response to different proapoptotic stimuli. Analysis of the abundances of NDR1 and NDR2 proteins revealed that loss of NDR1 was functionally compensated for by an increase in the abundance of NDR2 protein. Despite this compensation, NDR1(-/-) and NDR1(+/-) mice were more prone to the development of T cell lymphomas than were wild-type mice. Tumor development in mice and humans was accompanied by a decrease in the overall amounts of NDR proteins in T cell lymphoma samples. Thus, reduction in the abundance of NDR1 triggered a decrease in the total amount of both isoforms. Together, our data suggest that a reduction in the abundances of the NDR proteins results in defective responses to proapoptotic stimuli, thereby facilitating the development of tumors.

Members of the NDR (nuclear Dbf2-related) protein-kinase family are essential components of pathways that control important cellular processes, such as morphological changes, mitotic exit, cytokinesis, cell proliferation and apoptosis. Recent progress has shed light on the mechanisms that underlie the regulation and function of the NDR family members. Combined data from yeast, worms, flies, mice and human cells now highlight the conserved and important roles of the different NDR kinases in distinct cellular processes.