The activity of a PI3K δ-sparing inhibitor, MEN1611, in non-small cell lung cancer cells with constitutive activation of the PI3K/AKT/mTOR pathway

Background

Lung cancer remains the leading cause of cancer-related death worldwide. Targeted therapies with tyrosine kinase inhibitors (TKIs) result in improvement in survival for non-small cell lung cancer (NSCLC) with activating mutations of the epidermal growth factor receptor (EGFR). Unfortunately, most patients who initially respond to EGFR-TKI ultimately develop resistance to therapy, resulting in cancer progression and relapse. Combination therapy is today a common strategy for the treatment of tumors to increase the success rate, improve the outcome and survival of patients, and avoid the selection of resistant cancer cells through the activation of compensatory pathways. In NSCLC, the phosphoinositide-3-kinase/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway has been heavily implicated in both tumorigenesis and the progression of disease.

Objectives

In this study, we investigated the efficacy of a PI3K δ-sparing inhibitor, MEN1611, in models of NSCLC sensitive and resistant to EGFR inhibitors (erlotinib and gefitinib) with a wild-type PIK3CA gene.

Methods

We performed functional, biochemical, and immunohistochemistry studies.

Results

We demonstrated good efficacy of MEN1611 in NSCLC devoid of PIK3CA gene mutations but with constitutive activation of the PI3K/AKT pathway and its synergistic effect with gefitinib both in vitro and in vivo.

Conclusions

Overall, this preclinical study indicates that the inhibitor could be a candidate for the treatment of NSCLC with an erlotinib/gefitinib-resistant phenotype and constitutive activation of the PI3K/AKT pathway, a phenotype mimicked by our model system.

Modeling the novel SERD elacestrant in cultured fulvestrant-refractory HR-positive breast circulating tumor cells

PURPOSE

Metastatic hormone receptor-positive (HR+) breast cancer initially responds to serial courses of endocrine therapy, but ultimately becomes refractory. Elacestrant, a new generation FDA-approved oral selective estrogen receptor degrader (SERD) and antagonist, has demonstrated efficacy in a subset of women with advanced HR+breast cancer, but there are few patient-derived models to characterize its effect in advanced cancers with diverse treatment histories and acquired mutations.

METHODS

We analyzed clinical outcomes with elacestrant, compared with endocrine therapy, among women who had previously been treated with a fulvestrant-containing regimen from the recent phase 3 EMERALD Study. We further modeled sensitivity to elacestrant, compared with the currently approved SERD, fulvestrant in patient-derived xenograft (PDX) models and cultured circulating tumor cells (CTCs).

RESULTS

Analysis of the subset of breast cancer patients enrolled in the EMERALD study who had previously received a fulvestrant-containing regimen indicates that they had better progression-free survival with elacestrant than with standard-of-care endocrine therapy, a finding that was independent estrogen receptor (ESR1) gene mutations. We modeled elacestrant responsiveness using patient-derived xenograft (PDX) models and in ex vivo cultured CTCs derived from patients with HR+breast cancer extensively treated with multiple endocrine therapies, including fulvestrant. Both CTCs and PDX models are refractory to fulvestrant but sensitive to elacestrant, independent of mutations in ESR1 and Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) genes.

CONCLUSION

Elacestrant retains efficacy in breast cancer cells that have acquired resistance to currently available ER targeting therapies. Elacestrant may be an option for patients with HR+/HER2- breast cancer whose disease progressed on fulvestrant in the metastatic setting.

TRANSLATIONAL RELEVANCE

Serial endocrine therapy is the mainstay of management for metastatic HR+breast cancer, but acquisition of drug resistance highlights the need for better therapies. Elacestrant is a recently FDA-approved novel oral selective estrogen receptor degrader (SERD), with demonstrated efficacy in the EMERALD phase 3 clinical trial of refractory HR+breast cancer. Subgroup analysis of the EMERALD clinical trial identifies clinical benefit with elacestrant in patients who had received prior fulvestrant independent of the mutational status of the ESR1 gene, supporting its potential utility in treating refractory HR+breast cancer. Here, we use pre-clinical models, including ex vivo cultures of circulating tumor cells and patient-derived xenografts, to demonstrate the efficacy of elacestrant in breast cancer cells with acquired resistance to fulvestrant.

Abstract 2849: The oral SERD Elacestrant in combination with the PI3K inhibitor MEN1611 inhibits tumor growth in ER+/HER2- breast cancer in vitro and in PDX models

In estrogen receptor (ER)+/HER2-breast cancer(BC), the addition of CDK4/6 inhibitors (CDK4/6i) to endocrine therapies (ET) leads to a significant increase in progression-free survival. Nevertheless, clinical resistance emerges. The upregulation of the PI3K/AKT/mTOR signaling pathway is one of the multiple acquired mechanisms of resistance to the CDK4/6i and ET combination. Thus, the extensive crosstalk between the PI3K/AKT/mTOR and ER pathways underlines the importance of targeting both pathways to overcome drug resistance in ER+/HER2- BC. Here we have evaluated the antitumor activity of Elacestrant, the oral selective estrogen receptor degrader (SERD) and antagonist, in combination with the σ-sparing PI3K inhibitor MEN1611, in vitro and in vivo in different clinically relevant BC Patient-Derived Xenograft (PDX) models, resistant to CDK4/6i and to ET, harboring mutations in PIK3CA and/or ESR1 genes. In cell-based proliferation assays, the combination of Elacestrant and MEN1611 showed a synergistic effect in inhibiting the growth of ER+ BC cell lines. In vivo data in MCF7- and patient-derived xenograft models showed compelling antitumor activity using the combination at tolerable and clinically relevant doses, compared to the single agents. In the PDX HBxC-3, wild-type for PIK3CA and ESR1 genes, the Tumor Volume-Inhibition (TVI) was 56.2%, 48.7% and 71.7% for MEN1611, Elacestrant and the combination group, respectively. In this model, the combination showed improved anti-tumor activity in comparison to the single agent treatments. In the PDX models HBxC-19 and CTG-2308, wild-type for ESR1 gene, but harboring a PIK3CA mutation, the TVI of the combination was 94.6% and 61.4%, respectively. In the latter model the combination was significantly superior to the single agents. In the PDX model CTG-1260, with PIK3CA and ESR1 mutations, MEN1611 and Elacestrant single agent treatment showed tumor growth inhibition with TVIs of 63.2% and 52.3%, while the combination showed a significant TVI of 86.9%. Overall, in all the tested in vivo models the combination of Elacestrant and MEN1611 was superior in comparison to the single agents by overcoming resistance to ER inhibition potentially driven by PI3K pathway activation in PIK3CA mutated tumors. The current data support the use of Elacestrant, the first oral SERD with positive phase III results in the EMERALD trial (Bidard et al.; JCO 2022), in combination with the PI3K inhibitor MEN1611, in ER+/HER2- mBC patients harboring PIK3CA mutations and who progressed to CDK4/6i plus ET.

Citation Format: Giuseppe Merlino, Alessio Fiascarelli, Simone Talucci, Patrizia Tunici, Mario Bigioni, Alessandro Bressan, Monica Binaschi. The oral SERD Elacestrant in combination with the PI3K inhibitor MEN1611 inhibits tumor growth in ER+/HER2- breast cancer in vitro and in PDX models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2849.

Antitumor activity of the PI3K δ-sparing inhibitor MEN1611 in PIK3CA mutated, trastuzumab-resistant HER2 + breast cancer

PURPOSE

Dysregulation of the PI3K pathway is one of the most common events in breast cancer. Here we investigate the activity of the PI3K inhibitor MEN1611 at both molecular and phenotypic levels by dissecting and comparing its profile and efficacy in HER2 + breast cancer models with other PI3K inhibitors.

METHODS

Models with different genetic backgrounds were used to investigate the pharmacological profile of MEN1611 against other PI3K inhibitors. In vitro studies evaluated cell viability, PI3K signaling, and cell death upon treatment with MEN1611. In vivo efficacy of the compound was investigated in cell line- and patient-derived xenografts models.

RESULTS

Consistent with its biochemical selectivity, MEN1611 demonstrated lower cytotoxic activity in a p110δ-driven cellular model when compared to taselisib, and higher cytotoxic activity in the p110β-driven cellular model when compared to alpelisib. Moreover, MEN1611 selectively decreased the p110α protein levels in PIK3CA mutated breast cancer cells in a concentration- and proteasome-dependent manner. In vivo, MEN1611 monotherapy showed significant and durable antitumor activity in several trastuzumab-resistant PIK3CA-mutant HER2 + PDX models. The combination of trastuzumab and MEN1611 significantly improved the efficacy compared to single agent treatment.

CONCLUSIONS

The profile of MEN1611 and its antitumoral activity suggest an improved profile as compared to pan-inhibitors, which are limited by a less than ideal safety profile, and isoform selective molecules, which may potentially promote development of resistance mechanisms. The compelling antitumor activity in combination with trastuzumab in HER2 + trastuzumab-resistant, PIK3CA mutated breast cancer models is at the basis of the ongoing B-Precise clinical trial (NCT03767335).

Abstract 1376: Dosing frequency/PD/efficacy relationship of MEN1611 in HER2 amplified, PIK3CA mutated, and refractory to Trastuzumab xenograft model of breast cancer

The PI3K-AKT-mTOR pathway is one of the most dysregulated pathways in human cancers, with PIK3CA, the gene encoding the p110α catalytic isoform of PI3K, representing the most frequently mutated gene of this network. In breast tumors, PIK3CA mutations occur in about 20% to 40% of HER2-positive and HER2-negative respectively. The lack of driver oncogenic function, hypothesized for PIK3CA mutations, paralleled by the poor clinical benefit showed by monotherapy with PI3K inhibitors in solid tumors, suggests the use of rational combinations with optimized dosing to improve PI3K inhibitor efficacy. Here we investigate the activity of the PI3K α/β selective and δ-sparing inhibitor MEN1611 in once-daily (QD) at 3.2 mg/kg versus twice-daily (BID) dosing at 1.6 mg/kg, both as a single agent and in combination with trastuzumab, to examine the correlation between drug regimen, target effect, and tumor response. The in vivo studies were investigated with the HER2 amplified, PIK3CA mutated (p.C420R), and trastuzumab-resistant JIMT-1 breast cancer cell line. To compare the effect of QD versus BID MEN1611 treatment, we evaluated the magnitude of PI3K signaling at the tumor site, by measuring the levels of pAKT and pS6 at different time points, at the beginning and the end of treatment. Anti-tumor activity was evaluated in terms of tumor volume inhibition (TVI) and by the modified response evaluation criteria in solid tumors (mRECIST). In monotherapy, although QD dosing produced a slightly longer pathway inhibition (10 vs 8 hours) than the BID, the maximum magnitude achieved was comparable. The analysis of anti-tumor efficacy, showed non-significant differences between the two schedules in terms of tumor volume inhibition (52% versus 45% for the QD and the BID respectively), confirming the PD data. In combo, BID administration was able to keep the pathway efficiently downregulated, counteracting a rebound effect observed at the 24 hour time point in the QD group of animals. Moreover, efficacy evaluation showed significant tumor-regression activity in the BID group of animals compared to the QD (79% versus 43% respectively). Although further studies are needed to evaluate time-dependent drug exposure in tumor and plasma samples, these preliminary findings support the BID clinical schedule of MEN1611 in the B-PRECISE-01 clinical trial (NCT03767335).

Citation Format: Alessio Fiascarelli, Giuseppe Merlino, Stefania Capano, Alessandro Bressan, Mario Bigioni, Andrea Pellacani, Monica Binaschi, Massimiliano Salerno. Dosing frequency/PD/efficacy relationship of MEN1611 in HER2 amplified, PIK3CA mutated, and refractory to Trastuzumab xenograft model of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1376.

Abstract 1170: MEN1112/OBT357, a first-in-class humanized de-fucosylated monoclonal antibody targeting CD157 positive cells in acute myeloid leukemia and myelodysplastic syndrome

Bst1/CD157 is a GPI-anchored transmembrane protein encoded by a member of the CD38 NADase/ADP-ribosyl cyclase gene family, which is expressed on some blood cells of the myeloid lineage, such as monocytes and neutrophils. The antigen is found to be highly expressed, at diagnosis and relapse, in primary samples derived from Acute Myeloid Leukemia (AML) patients, showing the brightest expression in monocyte-oriented blasts. Moreover, CD157 is expressed in high and low-risk Myelodysplastic Syndrome (MDS) patients. MEN1112/OBT357, is a humanized de-fucosylated monoclonal antibody, in clinical development (clinicaltrials.gov identifier: NCT02353143), that is characterized by high affinity and specificity against CD157, inducing potent in vitro Antibody-Dependent Cell-mediated Cytotoxicity (ADCC). The de-fucosylation improved the binding of MEN1112/OBT357 to both high and low-affinity alleles of FcγRIIIa/CD16a, allowing stronger recognition by NK cells. Since no Complement-Dependent Cytotoxicity (CDC) activity was detected, the MEN1112/OBT357 mechanism of action should mainly rely on immune effector cells. Indeed, in an in vitro reporter assay, MEN1112/OBT357 significantly triggered ADCC activity against AML target cell lines with different expression of CD157. Since the ex vivo sensitivity assay is considered a pharmacologically and clinically relevant model to evaluate the preclinical efficacy of therapeutic antibodies in AML (1), MEN1112/OBT357 activity was tested in 38 AML primary samples, demonstrating promising efficacy in an autologous setting, both in peripheral blood and bone marrow samples, in comparison to healthy donor blood samples and independently from FcγRIIIa polymorphisms. A similar activity was also observed in CD157 positive MDS primary samples. Since Myeloid-Derived Suppressor Cells (MDSCs) have been described to be increased in the bone marrow of both AML and MDS patients and their presence to be associated with resistance to chemotherapy (2, 3), we investigated CD157 expression in MDSCs, demonstrating a high expression of the antigen in the bone marrow and peripheral blood of AML patients. Importantly, we confirmed in ex vivo experiments, the depletion of these immunosuppressive cells by MEN1112/OBT357. Overall, our data demonstrate that MEN1112/OBT357 is a novel antibody with potent ex vivo activity against blast cells in AML and MDS patients, suggesting a potential contribution of MEN1112/OBT357 in altering the immunosuppressive environment in the bone marrow niche. References 1. Swords RT et al. Leukemia Research 2018 2. Sun H. et al. Int J Hematology 2015 3. Kittang A.O. et al. Oncoimmunology 2016

Citation Format: Corrado Carrisi, Daniela Bellarosa, Diego Bisignano, Adriano Venditti, Francesco Buccisano, Giuseppe Sconocchia, Andrea Coppola, Anna Aureli, Alessio Fiascarelli, Alessandro Bressan, Simone Baldini, Andrea Pellacani, Monica Binaschi. MEN1112/OBT357, a first-in-class humanized de-fucosylated monoclonal antibody targeting CD157 positive cells in acute myeloid leukemia and myelodysplastic syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1170.

Abstract PS18-26: Men1611 promotes immune activating myeloid cell polarization

MEN1611 is a PI3K inhibitor currently in clinical development targeting the p110 α, β and γ isoforms, while sparing the δ subunit. In preclinical models, MEN1611 has demonstrated a long lasting antitumor activity when combined with trastuzumab in HER2+/PiK3CA mutated breast cancer. Aim of this work is to characterize the effects of MEN1611 on the PI3Kγ isoform, highly expressed in tumor-associated macrophages (TAMs), in order to understand whether the anti-tumor activity of MEN1611 might be also mediated by the inflammatory microenvironment. Previous evidences have shown that selective targeting of PI3Kγ by IPI-549 can reshape the inflammatory cells infiltrating tumors towards a less immunosuppressive phenotype and promote cytotoxic T cell-mediated tumor regression. In order to evaluate the effect of MEN1611 on TAMs, we established an in vitro model by differentiating murine and human macrophages from bone marrow-derived monocytes or buffy coats-isolated monocytes respectively. Pro-inflammatory M1 macrophages have been differentiated by treatment with Lipopolysaccharide (LPS) and interferon γ (IFNγ), while pro-tumoral M2 macrophages by interleukin 4 (IL-4) stimulation. The cells, thus obtained, have been incubated with MEN1611 or IPI-549 (positive control) and the effects on their phenotype, gene and protein expression, evaluated through confocal microscopy, RNASeq and flow cytometry respectively. A syngeneic xenograft model of breast cancer based on 4T1 cells has been also established in order to investigate in vivo the activity of MEN1611 on the inflammatory environment (TAMs and T cells). In vitro data showed MEN1611 and IPI-549 ability to repolarize murine and human macrophages towards a pro-inflammatory phenotype. Confocal analysis revealed a shape remodeling from an elongated M2-like towards a round M1-like; gene and protein expression analysis revealed a significant increase of immuno-stimulating factors mRNA and M1 chemokines and cytokines secretion, respectively. A modulation of the inflammatory infiltrate was also observed in vivo where RNASeq and flow cytometry analysis on dissociated treated tumors highlighted an increase of pro-inflammatory markers. The in-silico ingenuity pathway analysis (IPA) performed on genes modulated by MEN1611 revealed the enhancement of some processes related to an immune activating switch, such as the recruitment of myeloid cells or the cytotoxicity of lymphocytes and natural killer cells. In conclusion, we demonstrated in a cellular context that MEN1611 activity on PI3Kγ isoform is responsible for macrophages reprogramming from an immune-suppressive to an immune-activating phenotype. Moreover, we observed that in 4T1 murine breast cancer model, tumor regression induced by MEN1611 was also sustained by a modulation of the inflammatory microenvironment, characterized by an increased recruitment and cytotoxicity of T cells.

Citation Format: Stefania Capano, Alessandro Paoli, Alessio Fiascarelli, Andrea Massimiliano Tomirotti, Mario Bigioni, Alessandro Bressan, Daniela Bellarosa, Massimiliano Salerno, Monica Binaschi. Men1611 promotes immune activating myeloid cell polarization [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-26.

Targeting CD205 with the antibody drug conjugate MEN1309/OBT076 is an active new therapeutic strategy in lymphoma models

Antibody drug conjugates represent an important class of anti-cancer drugs in both solid tumors and hematological cancers. Here, we report preclinical data on the anti-tumor activity of the first-in-class antibody drug conjugate MEN1309/OBT076 targeting CD205. The study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination and validation experiments on in vivo models. CD205 was first shown frequently expressed in lymphomas, leukemias and multiple myeloma by immunohistochemistry on tissue microarrays. Anti-tumor activity of MEN1309/OBT076 as single agent was then shown across 42 B-cell lymphoma cell lines with a median IC50 of 200 pM and induction of apoptosis in 25/42 (59.5%) of the cases. The activity appeared highly correlated with its target expression. After in vivo validation as the single agent, the antibody drug conjugate synergized with the BCL2 inhibitor venetoclax, and the anti-CD20 monoclonal antibody rituximab. The first-in-class antibody drug targeting CD205, MEN1309/OBT076, demonstrated strong pre-clinical anti-tumor activity in lymphoma, warranting further investigations as a single agent and in combination.

CD157: From Myeloid Cell Differentiation Marker to Therapeutic Target in Acute Myeloid Leukemia

Human CD157/BST-1 and CD38 are dual receptor-enzymes derived by gene duplication that belong to the ADP ribosyl cyclase gene family. First identified over 30 years ago as Mo5 myeloid differentiation antigen and 10 years later as Bone Marrow Stromal Cell Antigen 1 (BST-1), CD157 proved not to be restricted to the myeloid compartment and to have a diversified functional repertoire ranging from immunity to cancer and metabolism. Despite being a NAD⁺-metabolizing ectoenzyme anchored to the cell surface through a glycosylphosphatidylinositol moiety, the functional significance of human CD157 as an enzyme remains unclear, while its receptor role emerged from its discovery and has been clearly delineated with the identification of its high affinity binding to fibronectin. The aim of this review is to provide an overview of the immunoregulatory functions of human CD157/BST-1 in physiological and pathological conditions. We then focus on CD157 expression in hematological tumors highlighting its emerging role in the interaction between acute myeloid leukemia and extracellular matrix proteins and its potential utility for monoclonal antibody targeted therapy in this disease.

MEN1309/OBT076, a First-In-Class Antibody-Drug Conjugate Targeting CD205 in Solid Tumors

CD205 is a type I transmembrane glycoprotein and is a member of the C-type lectin receptor family. Analysis by mass spectrometry revealed that CD205 was robustly expressed and highly prevalent in a variety of solid malignancies from different histotypes. IHC confirmed the increased expression of CD205 in pancreatic, bladder, and triple-negative breast cancer (TNBC) compared with that in the corresponding normal tissues. Using immunofluorescence microscopy, rapid internalization of the CD205 antigen was observed. These results supported the development of MEN1309/OBT076, a fully humanized CD205-targeting mAb conjugated to DM4, a potent maytansinoid derivate, via a cleavable N-succinimidyl-4-(2-pyridyldithio) butanoate linker. MEN1309/OBT076 was characterized in vitro for target binding affinity, mechanism of action, and cytotoxic activity against a panel of cancer cell lines. MEN1309/OBT076 displayed selective and potent cytotoxic effects against tumor cells exhibiting strong and low to moderate CD205 expression. In vivo, MEN1309/OBT076 showed potent antitumor activity resulting in durable responses and complete tumor regressions in many TNBC, pancreatic, and bladder cancer cell line-derived and patient-derived xenograft models, independent of antigen expression levels. Finally, the pharmacokinetics and pharmacodynamic profile of MEN1309/OBT076 was characterized in pancreatic tumor-bearing mice, demonstrating that the serum level of antibody-drug conjugate (ADC) achieved through dosing was consistent with the kinetics of its antitumor activity. Overall, our data demonstrate that MEN1309/OBT076 is a novel and selective ADC with potent activity against CD205-positive tumors. These data supported the clinical development of MEN1309/OBT076, and further evaluation of this ADC is currently ongoing in the first-in-human SHUTTLE clinical trial.

CD205, a target antigen for a novel ADC: Evaluation of antigen expression on TNBC, pancreatic adenocarcinoma and bladder urothelial carcinoma

e14726

Background: CD205 is a type I transmembrane surface protein belonging to the mannose receptor family with propensity for antigen uptake/internalization. CD205 is expressed in different cancer histotypes and seems to have a role in migration and invasion. For these features CD205 is an ideal candidate to be exploited as an ADC target. MEN1309/OBT076 (herein as MEN1309) is a humanized IgG1 antibody against CD205, conjugated through a cleavable linker to DM4. It has shown impressive anti-tumor activity when tested in high/low CD205 expressing xenografts for solid tumours and NHL. MEN1309 is under assessment in Phase I trials in EU (NCT03403725) and as OBT076 in USA. Methods: A retrospective evaluation of CD205 expression in 103 triple negative breast carcinomas (TNBC), 50 pancreatic adenocarcinomas (PAC) and 100 bladder urothelial carcinomas (UC) was performed at INT in Milan, Italy. Immunohistochemistry was performed on one FFPE representative sample per case, using a commercial anti-CD205 antibody. A semiquantitative score was applied to measure CD205 expression. Absence of staining tumor cells was scored as negative. Positivity was scored based on the percentages of neoplastic cells (NCs), with intensity of cytoplasmic staining ranging from 1 (weak) to 3 (strong). Membrane staining in NCs, immunoreactivity of the intratumoral/peritumoral inflammatory component and of normal tissue were scored as absent or present. Results: TNBC: 85% were positive, 70% in > 5% of NCs; 14% showed 2+/3+ staining intensity in > 50% of NCs. 57% of cases showed a membrane positivity. PAC: 100% were positive in > 5% of NCs; 50% showed 2+/3+ staining intensity in > 50% of NCs. 98% of cases showed a membrane positivity. UC: 67% were positive, 60% in > 5% of NCs; 10% showed 2+/3+ staining intensity in > 50% of NCs. 29% of cases showed a membrane positivity. Inflammatory component and normal tissue were positive in almost all cases. Conclusions: CD205 is heterogeneously expressed in the majority of TNBC and UC and in all PAC cases. The results of this study support the clinical investigation of MEN1309 in these tumor types.

B-PRECISE-01 Study: A phase Ib trial of MEN1611, a PI3K Inhibitor, combined with trastuzumab ± fulvestrant for the treatment of HER2-positive advanced or metastatic breast cancer

TPS1101

Background: MEN1611 is a potent, selective class I inhibitor of PI3K, a key enzyme in the transduction of various extracellular growth factor signals essential for cell survival and apoptosis. The discovery in human cancers of frequent PIK3CA mutations, that have been linked to a worse outcome in advanced HER2-positive breast cancer, makes PI3K an attractive therapeutic target. Preclinical and clinical evidences support the development of MEN1611 in combination with other agents in the context of solid tumors. Methods: B-PRECISE-01 is an open-label, multicenter, phase Ib dose escalation study in patients with PIK3CA mutant tumors, HER2-positive advanced or metastatic breast cancer which has progressed after at least 2 lines of anti-HER2 based therapy. PIK3CA mutations are assessed centrally by real-time PCR assay in DNA derived from archived tumor samples. MEN1611 will be administered orally BID for continuous 28-day cycles until disease progression, in combination with weekly IV infusions of trastuzumab. In addition, HR-positive postmenopausal patients will also be treated with fulvestrant. After the completion of the dose escalation phase (Step 1), the study will continue in an expansion cohort (Step 2) testing the Recommended Phase 2 dose (RP2D) in a total of 15 patients in each of the treatment groups. The primary study objective is to assess combination safety and select RP2D. Secondary objectives include assessment of pharmacokinetics and pharmacodynamics, preliminary clinical activity of MEN1611 in combination with trastuzumab +/- fulvestrant, and correlation with PIK3CA mutations and other relevant cancer genes mutational status. Adverse events will be graded according to NCI CTCAE v4.03. Responses will be evaluated according to RECIST v1.1. Study variables will be presented by dose-cohort and overall using appropriate descriptive statistics. The enrollment began in July 2018 at European sites and US sites will shortly participate; up to date the first dose cohort level has been achieved. Clinical trial information: NCT03767335.

CLI24-001: First-in-human study of SEL24/MEN1703, an oral dual PIM/FLT3 kinase inhibitor, in patients with acute myeloid leukemia

TPS7062

Background: FLT3-ITD is one of the most common genetic lesions in acute myeloid leukemia (AML). PIM kinases are oncogenic FLT3-ITD targets expressed in AML cells and increased PIM kinase expression is found in relapse samples from AML patients treated with FLT3 inhibitors. In addition, inhibition of PIM kinases restores sensitivity to FLT3 inhibitors and dual FLT3/PIM inhibition eradicates FLT3-ITD+ cells including primary AML cells. SEL24/MEN1703, a potent PIM/FLT3 dual inhibitor, demonstrates a significantly broader spectrum of activity in AML cell lines and primary AML blasts, irrespective of FLT3 status, compared to monotherapy with either FLT3 or PIM inhibitors such as quizartinib or AZD1208. Methods: CLI24-001 is a First in Human, open label, non-randomized, multi-center, Phase I/II dose-escalation and cohort expansion study of SEL24/MEN1703 in AML patients (excluding APL) not suitable for chemotherapy. SEL24/MEN1703 is given orally, QD, for 14 days in a 21-day cycle with cycles repeated until disease progression or unacceptable toxicity. Dose escalation follows a 3+3 design to identify the recommended phase 2 dose (RP2D). In the phase 2 part/cohort expansion, subjects will receive SEL24/MEN1703 at the RP2D, to further investigate the safety profile and signs of antileukemic activity. In both study parts, patients are eligible regardless of mutational status and/or prior exposure to FLT3 inhibitors; prior treatment with PIM inhibitors is not allowed. Main inclusion criteria comprise a white blood count (WBC) of ≤30 x 109/L (hydroxyurea/leukoapheresis permitted to lower WBC). Key secondary objectives include pharmacokinetics (PK) and single agent efficacy. The study is enrolling at 5 US sites and will be extended, both in US and EU, in the cohort expansion part. This is the first trial testing a dual PIM/FLT3 inhibitor with the potential to be active in AML regardless of FLT3 status andwith a potential to overcome FLT3 inhibitor resistance. (Sci Adv. 2015;1:e1500221; Oncotarget. 2018 Mar 30;9(24):16917-16931) Clinical trial information: NCT03008187.

Abstract 2160: MEN1611, a novel α-selective PI3K inhibitor in solid tumors

The PI3K pathway regulates various cellular processes such as proliferation, growth, apoptosis and cytoskeletal rearrangement. This pathway is frequently de-regulated and considered an oncogenic driver in human cancer. In most solid tumors, the activation of the PI3K pathway is induced by mutations of the catalytic subunit PI3Kα, present in approximately 20% to 50% of breast cancer, 14% of colorectal cancer and in 5-10% of NSCLC. Besides being an actionable target, the PI3K pathway is implicated in de novo and acquired treatment resistant in various tumor types treated with targeted therapy. As a matter of fact, the most interesting antitumor activity with PI3K inhibitors has been observed in combination. Here, we present MEN1611 (previously PA799), a PI3-kinase inhibitor with a peculiar biochemical profile targeting with high inhibition potency the mutated forms of PI3Kα and PI3Kγ. In the current study we demonstrate the anticancer activity and the pharmacodynamic effects of MEN1611 as monotherapy or in combination with targeted therapies in both xenograft and PDX models of breast cancer and in colorectal cancer and in NSCLC models, all with defined genetic profiles. MEN1611, at a clinically relevant dose, showed good antitumor activity in combination with targeted therapy agents against breast cancer, colorectal cancer and NSCLC models bearing PI3Kα mutations. A reduced activity was instead observed when the tumor models were wild type for PI3Kα or had low levels of PTEN. The antitumor activity of MEN611 was supported by its pharmacodynamic activity. In all the models, both AKT and S6 phosphorylation, markers of PI3K inhibition, were significantly inhibited upon treatment. In agreement with the biochemical profile of the drug, in PTEN null xenograft models where the tumor driver is the PI3K β-isoform, we observed lower effects in term of antitumor activity and of molecular inhibition of the pathway. Last, MEN1611 induction of hyperglycemia and insulin release was studied in the tumor models at clinical relevant dose as a marker of class-effect toxicity. MEN1611 showed significant antitumor activity in combination with other targeted therapies in breast, colon and NSCL cancer PI3Kα mutant models. Our results support the evidence that MEN611 is a PI3Kα specific inhibitor and provided the basis for the planned phase IB/II.

Citation Format: Giuseppe Merlino, Alessio Fiascarelli, Mario Bigioni, Alessandro Bressan, Clelia Irrissuto, Andrea Pellacani, Maurizio Scaltriti, Monica Binaschi. MEN1611, a novel α-selective PI3K inhibitor in solid tumors [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 2160.

Abstract 2145: The role of MEN1611, a class I PI3-kinases (PI3Ks) inhibitor, in reprogramming the pro-tumoral inflammatory environment

MEN1611 (previously PA799) is a specific PI3Ks inhibitor with peculiar biochemical profile: it targets at the highest potency the mutated PI3Kα isoforms and the PI3Kγ isoform. PI3Kγ isoform is abundantly expressed in myeloid cells but not in cancer cells and promotes myeloid cell trafficking during inflammation and cancer. Previous studies have shown that selective inactivation of macrophage PI3Kγ is able to promote an immunostimulatory transcriptional program that restores CD8+ T cell activation and cytotoxicity. Based on these evidences, we sought to investigate whether the anti-tumoral activity of MEN1611, that has been demonstrated especially in tumors harboring PI3Kα mutations, should be mediated also by inflammatory cells. To this aim we have set up an in vitro model in order to study macrophages polarization: in the presence of colony stimulating factor, mouse bone marrow-derived monocytes were directed into M0 macrophages differentiation, followed by M1 (by lipopolysaccharides and interferon γ) or M2 stimulation (by interleukin 4). Potential changes in macrophage phenotype induced by MEN1611 were measured by quantitative RT-qPCR and mouse cytokine antibody array. Moreover in order to evaluate in vivo the immune modulatory capacity of MEN1611 two syngeneic tumor models were established: 4T1 breast tumor model and CT26.wt colorectal tumor model. M1 or M2 polarized macrophages displayed different cell morphologies: M2 cells exhibited an higher degree of elongation compared with M1 or unstimulated M0 cells. Their activation status was tracked and confirmed by gene expression analysis, enzymatic assays (iNOS and arginase activity) and cytokine array. MEN1611 treatment was able to revert M2 cell morphology towards an M1-like round cell shape. Analysis of gene expression in MEN1611-treated macrophages showed a significant increase of immunostimulating factors mRNAs, such as IL-1b, IL-12b and iNOS, in M2 macrophages. MEN1611 also enhanced the secretion of pro-inflammatory cytokines both in M1 and M2 macrophages. In syngeneic mouse models, immune cell subsets were characterized via flow cytometry: both 4T1 and CT26.wt tumors had a similar baseline relative amount of M1 and M2 macrophages and were characterized by CD4+ and CD8+ T cells infiltrates. The impact of MEN1611 treatment on macrophages and T lymphocytes subsets infiltrating tumors is currently studied. In conclusion, we have demonstrated the ability of MEN1611 to modulate macrophage polarization towards an immune-activating phenotype at clinically relevant doses. These findings might suggest the involvement of PI3Kγ as part of MEN1611 mechanism of action.

Citation Format: Stefania Capano, Alessio Fiascarelli, Andrea M Tomirotti, Mario Bigioni, Alessandro Bressan, Daniela Bellarosa, Andrea Pellacani, Monica Binaschi. The role of MEN1611, a class I PI3-kinases (PI3Ks) inhibitor, in reprogramming the pro-tumoral inflammatory environment [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 2145.

Abstract B188: DNA topoisomerase-mediated transcription-replication conflicts cause DNA damage by a transient increase of R loops and proteasome activity

DNA topoisomerases have an important function in preventing replication/transcription (R/T) conflicts caused by RNA polymerases elongating in the opposite (or same) direction of advancing replication fork. Published data demonstrated that such persistent R/T conflicts can be rescued by overexpression of RNase H1, which specifically degrades the RNA of DNA:RNA hybrids present in R-loop structures. R loops are a common non-B DNA structure of cellular genomes that mainly occur during transcription. R loops can lead to genome instability; however, they also play a role in important cellular functions. Here, we have determined the dynamics of cellular R loops generated by chemical poisoning of DNA topoisomerases (TOP1 and TOP2) and the role of the proteasome in DNA damage induction by performing detailed kinetics analyses of cellular R loops by immunofluorescence microscopy. Treatment of HeLa and U2OS cells with clinically used topoisomerase inhibitors (camptothecin, LMP-776, MJ-III-65, doxorubicin, sabarubicin) triggers an immediate increase of nucleoplasmic R loops from 2 to 10-20 minutes of treatment, followed by a dramatic reduction of R-loop levels at 1 hour. Concomitantly with the reduction of R-loop structures, DNA damage was detected as phosphorylation of histone H2AX, a marker of DNA double-stranded breaks (DSB). Pretreating cells with MG132 (a proteasome inhibitor) stabilized the presence of R loops at longer treatment times and concomitantly reduced DSB formation, suggesting that the degradation of poisoned topoisomerases is necessary to trigger the pathway resulting in DSB formation. Overexpression of RNaseH1 in U2OS cells abolishes the transient increase of R loops and the induction of DNA damage. Topoisomerase poisoning is able to effectively kill the studied human cancer cells. However, overexpression of RNaseH1 or MG132 markedly reduced cell killing induced by R/T conflicts generated by topoisomerase inhibitors. The results are overall consistent with a necessary function of nuclear proteasome in generating a free DNA break from abortive topoisomerase cleavage complexes that will eventually lead to DSBs.

Citation Format: Jessica Marinello, Maria Delcuratolo, Yves Pommier, Monica Binaschi, Andrea Pellacani, Giovanni Capranico. DNA topoisomerase-mediated transcription-replication conflicts cause DNA damage by a transient increase of R loops and proteasome activity [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B188.

Abstract 2630: MEN1309, a novel antibody drug conjugate (ADC) targeting Ly75 antigen, induces complete responses in several xenografts of solid tumors

The cell surface antigen Lymphocyte antigen 75 (LY75, CD205, DEC-205) is over-expressed in several tumor histotypes. It is a type I C-type lectin receptor (CLR), normally expressed on various APC subsets, characterized by a cytoplasmic domain containing protein motifs crucial for endocytosis and internalization upon ligation. These features make the antigen ideal to be exploited as a target for a novel ADC. MEN1309 is a humanized IgG1 antibody directed against the cell surface antigen Ly75, conjugated through a cleavable linker to a potent maytansinoid microtubule disruptor, DM4. In this study, we evaluated the in vitro and in vivo (xenografts and PDX) efficacy of MEN1309 in different tumor histotypes. A PK/PD relationship was also investigated in tumor-bearing mice. IHC demonstrated high prevalence of Ly75 in human pancreatic, triple negative breast, and bladder cancers, as well as in diffuse large B-cell lymphoma. In vitro experiments showed that cytotoxic activity of MEN1309 was in nM/sub nM range against several lymphoma, pancreatic, bladder and triple-negative breast cancer (TNBC) cell lines. Moreover, MEN1309 exhibited high cell-killing ability against cells having either strong as well as low to moderate antigen expression. In vivo, MEN1309 at 2.5-5 mg/kg (schedule varying from single dose, q7dx3, or q21dx3) showed an impressive antitumor activity, resulting in complete and long lasting responses in most of the xenograft models representing lymphoma, TNBC, bladder and pancreatic cancers, expressing the antigen at high but also at low levels. No treatment related toxicity in terms of change of body weight and death events were detected. Moreover, the administration of (i) isotype control-DM4, (ii) the non-conjugate antibody IgG1 and (iii) the free toxin DM4 (at a dosage corresponding to the equimolar concentration linked at 10 mg/kg ADC) showed little to no therapeutic efficacy on tumor growth. In TNBC patient-derived xenograft (PDX) model (coming from a heavily pre-treated patient and expressing high level of the antigen Ly75), MEN1309 (5 mg/kg q21dx3) showed a complete tumor regression. Finally, in the pancreatic adenocarcinoma xenograft model HPAFII, the pharmacokinetics profile in serum of MEN1309 at 5 mg/kg was characterized and it was qualitatively correlated, using immunofluorescence, with the occurrence of phosphorylation of Serine 10 of H3 Histone in cancer cells, as a pharmacodynamic (PD) marker of DM4 activity on microtubules. Initial ADC exposure was noteworthy and was followed by a relatively fast decline. In parallel with the decay of the serum ADC concentrations there was a progressive increase in the number of positive cells showing the PD marker for mitotic arrest. Overall, our data suggest that MEN1309 is a selective and potent novel antitumoral ADC and it deserves to enter into aPhase I study for a variety of Ly75 positive tumor histotypes.

Citation Format: Mario Bigioni, Giuseppe Merlino, Cristina Bernadó Morales, Rossana Bugianesi, Attilio Crea, Rosanna Manno, Joaquin Arribas, Rachel Dusek, Nickolas Attanasio, Keith Wilson, Christian Rohlff, Monica Binaschi. MEN1309, a novel antibody drug conjugate (ADC) targeting Ly75 antigen, induces complete responses in several xenografts of solid tumors [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 2630. doi:10.1158/1538-7445.AM2017-2630

Abstract 3646: Characterization of the novel antibody drug conjugate MEN1309 and its target antigen Ly75

Ly75 (CD205, DEC-205) is a type I transmembrane glycoprotein and a C-type lectin receptor involved in antigen uptake and processing, mainly expressed by antigen presenting cells (APC). The short cytoplasmic tail contains motifs for amino acid-based endocytosis, making this receptor an ideal target antigen for an antibody drug conjugate (ADC)-based antitumoral therapy. MEN1309 is a novel fully humanized ADC which binds to Ly75 with high affinity as shown by ELISA and FACS analysis. The antibody is conjugated to a maytansinoid DM4, a potent tubulin inhibitor, through a cleavable linker.The ability of Ly75 to internalize the antibody after binding was determined using an immunoflourescence assay that showed a rapid, efficient, and near complete internalization over a one hour time course.The expression of Ly75 mRNA and protein was investigated in human cancer cell lines derived from different histotypes and revealed high expression in pancreas, bladder, triple negative breast cancer (TNBC) cells and in diffuse large B-cell lymphoma (DLBCL). Indeed, MEN1309 shows a powerful (pM range) in vitro cytotoxic activity on different cancer cell lines expressing Ly75, whereas it exerts a weaker effect on antigen-negative cells. Besides the mechanism of action (MoA) of MEN1309 as an ADC, the putative efficacy of the antibody to drive an ADCC response was investigated through in vitro binding and functional assays. In spite of a high binding affinity of MEN1309 to FcγRIIIa, no ADCC response was observed, suggesting that the high internalization rate of the antigen could hamper the triggering of NK responses.Moreover, in order to characterize the functional role of Ly75 in cancer cell lines, its expression was downregulated by siRNA demonstrating an inhibition of the proliferation rate in cells from different histotypes.Finally, we investigated if some cancer cell lines could show a higher expression of two intergenically spliced forms derived from Ly75 and DCL-1 genes recently reported in literature. We found that the intergenically spliced forms were expressed on average 30 fold less than CD205 mRNA in all the cancer cell lines analyzed, suggesting that these variants derive just from an intergenic readthrough without a specific transcriptional regulation.

Citation Format: Alessandro Bressan, Alessio Fiascarelli, Giuseppe Merlino, Corrado Carrisi, Daniela Bellarosa, Rachel Dusek, Rahel Awdew, Sudha Swaminathan, Arnima Bisht, To Uyen T. Do, San Lin Lou, Dee Aud, Jonathan Terrett, Keith Wilson, Christian Rohlff, Monica Binaschi. Characterization of the novel antibody drug conjugate MEN1309 and its target antigen Ly75 [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 3646. doi:10.1158/1538-7445.AM2017-3646

CD205, a target antigen for a novel antibody drug conjugate (ADC): Evaluation of antigen expression on non-Hodgkin lymphoma (NHL)

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Background: CD205 is a type I C-type lectin receptor normally expressed on various APC and some leukocyte sub-populations, characterized by a cytoplasmic domain containing protein motifs crucial for endocytosis and internalization. These features make CD205 ideal to be exploited as target of a novel ADC. MEN1309/OBT076 is a humanized IgG1 antibody against CD205, conjugated through a cleavable linker to a potent maytansinoid microtubule disruptor, DM4. Indeed, impressive results were obtained in high and low CD205 expressing xenografts for solid tumours and NHL. In vitro experimental model describing the by-stander effect of MEN1309 was implemented. Methods:A retrospective analysis to evaluate the CD205 expression on archival NHL biopsies was performed in the CRO-National Cancer Institute, Aviano IT. An immunohistochemistry (IHC) was performed on 1 slide per case, using a commercial antibody NCL-L-DEC205 (clone 11A10, Leica Biosystems). All slides were visually evaluated and a validated staining scoring system was applied, ranging from negative score 0 to strong immunostaining score 3+. Percentages (from 0 to 100%) of negative and positive tumor cells (scored as follows: 1-25% = score 1; 26-50% = score 2; 51-75% = score 3; 76-100% = score 4) were reported for each individual slide.Evaluation of correlations between CD205 expression and clinical characteristics is ongoing. Results: 100 cases of Diffuse Large B Cells Lymphomas (DLBCL) and 33 of Follicular Lymphomas (FL) were analysed. 60% of DLBCL cases were positive for CD205 and 39% had more than 25% of positive cells (score ≥2), while the 16% showed 2+/3+ staining intensity. 79% of FL cases were CD205 positive and 66% had more than 25% of positive cells, while the 27% showed 2+/3+ staining intensity. Conclusions: CD205 is heterogeneously expressed in the majority of DLBCL and FL cases. Data on the correlation between CD205 expression and clinical features will be discussed.MEN1309 has shown anti-tumour activity in vitro and in vivo even in low antigen expressing tumours. Hence CD205 expression among NHL, even if heterogeneous, makes, both DLBCL and FL, promising settings in which to explore MEN1309 activity in an upcoming FIH trial.

Proteomic screening identifies calreticulin as a miR-27a direct target repressing MHC class I cell surface exposure in colorectal cancer

Impairment of the immune response and aberrant expression of microRNAs are emerging hallmarks of tumour initiation/progression, in addition to driver gene mutations and epigenetic modifications. We performed a preliminary survey of independent adenoma and colorectal cancer (CRC) miRnoma data sets and, among the most dysregulated miRNAs, we selected miR-27a and disclosed that it is already upregulated in adenoma and further increases during the evolution to adenocarcinoma. To identify novel genes and pathways regulated by this miRNA, we employed a differential 2DE-DIGE proteome analysis. We showed that miR-27a modulates a group of proteins involved in MHC class I cell surface exposure and, mechanistically, demonstrated that calreticulin is a miR-27a direct target responsible for most downstream effects in epistasis experiments. In vitro miR-27a affected cell proliferation and angiogenesis; mouse xenografts of human CRC cell lines expressing different miR-27a levels confirmed the protein variations and recapitulated the cell growth and apoptosis effects. In vivo miR-27a inversely correlated with MHC class I molecules and calreticulin expression, CD8⁺ T cells infiltration and cytotoxic activity (LAMP-1 exposure and perforin release). Tumours with high miR-27a, low calreticulin and CD8⁺ T cells' infiltration were associated with distant metastasis and poor prognosis. Our data demonstrate that miR-27a acts as an oncomiRNA, represses MHC class I expression through calreticulin downregulation and affects tumour progression. These results may pave the way for better diagnosis, patient stratification and novel therapeutic approaches.

OC125, M11 and OV197 epitopes are not uniformly distributed in the tandem-repeat region of CA125 and require the entire SEA domain

The human cancer antigen 125 (CA125) is over-expressed in epithelial ovarian cancer cells and it plays a role in the pathogenesis of ovarian cancer. This protein presents a repeat region containing up to sixty tandem repeat units. The anti-CA125 monoclonal antibodies have been previously classified into three groups: two major families, the OC125-like antibodies and M11-like antibodies, and a third group, the OV197-like antibodies. A model in which a single repeat unit contains all the epitopes for these antibodies has been also proposed, even if their exact position is still undetermined. In the present work, the affinities of the monoclonal antibodies, representative of the three families, have been investigated for different CA125-recombinant repeats through Western blot analysis. Different patterns of antibody recognition for the recombinant repeats show that CA125 epitopes are not uniformly distributed in the tandem repeat region of the protein. The minimal region for the recognition of these antibodies has been also individuated in the SEA domain through the subcloning of deleted sequences of the highly recognized repeat-25 (R-25), their expression as recombinant fragments in E. coli and Western blot analysis. Obtained data have been further confirmed by ELISA using the entire R-25 as coating antigen.

Effect of metformin on recurrence-free survival and overall survival in diabetic patients affected by advanced ovarian cancer

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Background: Metformin, has recently shown some anti-cancer activities in ovarian cancer, both in vitro and in vivo. Methods: Analysis of Recurrence Free Survival (RFS) and Overall Survival (OS) was performed in patients (pts) with diabetes (D) treated with metformin (DMet+) or not (DMet-) enrolled in the MIMOSA trial, a randomized double-blind placebo-controlled international trial of Abagovomab maintenance therapy in 888 pts with advanced ovarian cancer. In the MIMOSA trial, no differences in the RFS and OS were observed between Abagovomab (n = 593) and Placebo arm (n = 295); hence, the present RFS and OS analysis (DMet+ vs DMet-) was run regardless of treatment allocation. A Cox proportional hazards model was used for adjusting the analysis for the predefined prognostic factors: Figo stage (III, IV), tumor size after debulking (residual tumor <1 cm, >1cm); CA125 serum level after 3th cycle (<35U/ml, >35U/ml). In addition, comparison of RFS and OS was done between DMet+and the overall MIMOSA population not exposed to metformin (ALLMet-), and between the overall diabetic pts (ALLD+) and non-diabetic pts (ALLD-). Results: In the ALL population (n = 888), 42 pts were affected by diabetes (ALLD+) divided to DMet+ (n = 27) and DMet- (n = 15), without difference in the prognostic factors distribution. When analysis was done in ALLD+, RFS median time was not reached in the DMet+ group whereas it was 328 days [CI: 30-660] in DMet- group with HR favoring DMet+=0.419 [CI:0.175-1.002]; p = 0.05. Median OS time was also not reached in the DMet+ group whereas it was 786 days [CI:262-NE] in DMet- group with HR=0.295 [CI:0.109-0.803]; p = 0.02. Interestingly HR for RFS time was still in favour of DMet+ group when compared to the ALLMet- (n=861) with HR=0.575 (CI=0.324-1.022); p = 0.06. When ALLD+ were compared with ALLD-(n = 846), no significant differences was detected in RFS and OS time. Conclusions: The present results are the first prospectively analyzed data demonstrating a favourable impact of metformin treatment on RFS and OS in pts affected by advanced ovarian cancer. Clinical trial information: NCT00418574.

SAHA/Vorinostat induces the expression of the CD137 receptor/ligand system and enhances apoptosis mediated by soluble CD137 receptor in a human breast cancer cell line

HDAC inhibitors (HDACis) represent a class of anticancer agents including suberoylanilide hydroxamic acid (SAHA, Vorinostat), which has shown a strong antitumor effect, both in vitro and in vivo. Induction of apoptotic genes is an important pathway of SAHA cytotoxic mechanism of action and it has been largely described that SAHA induces sensitization of cell death receptor-resistant breast cancer cells to apoptosis. In this study, we investigated the activation of some apoptotic genes which could be responsible for the in vivo antitumor potency of SAHA in a model of human breast cancer. We found that the apoptotic gene pattern induced by SAHA in the MDA-MB-231 cell line involves the upregulation of some molecules belonging to the TNF superfamily. In particular, we demonstrated that the upregulation of the CD137 receptor/ligand system correlates with a synergistic cytotoxic effect when MDA-MB-231 cells are treated with the combination of SAHA and soluble CD137 receptor. To our knowledge, this is the first study to indicate that this member of the TNF superfamily, CD137, is modulated by SAHA treatment in breast cancer cells, suggesting that the combination of SAHA with this TNF-related receptor could be a new therapeutic approach for the treatment of tumors.

Synthesis and biological evaluation of rebeccamycin analogues modified at the imide moiety

Glycosylated indolocarbazoles related to the antibiotic rebeccamycin represent an important class of antitumour drugs. In the course of our structure-activity relationship studies, new rebeccamycin analogues modified at the imide moiety were synthesised. The antiproliferative activity of the compounds was evaluated on three human cancer cell lines, A2780 (ovarian cancer), H460 (lung cancer), and GLC4 (small-cell lung cancer). The in vitro cytotoxicity of compounds 2 and 4, characterised respectively by a 1,3-dioxolan and (1,3-dioxolan-4-yl)methylene groups linked to the imide moiety, was higher than the reference compound, edotecarin. The effect of compound 2 in inducing tumour regression in the A2780 xenograft model was also investigated.

Maintenance therapy in ovarian cancer: Molecular basis and therapeutic approach

Ovarian cancer has the highest mortality rate among gynaecological tumours despite the fact that the majority of patients with advanced disease achieve complete remission after first-line surgery and chemotherapy. Unfortunately, disease recurrence occurs in the majority of patients and second-line treatments are not curative. Clearly, the persistence of dormant and drug-resistant cells after front-line treatments results in the inability to cure the disease. The identification of cancer-initiating cells or cancer stem cells as key players in the development of recurrence has opened up a novel field of research aimed at identifying additional innovative therapeutic approaches. Strategies of maintenance therapy to extend the survival of patients have been studied, but to date no overall survival benefit has been detected. Currently, numerous clinical trials have just been completed or are ongoing involving patients achieving a complete clinical response after first-line chemotherapy in order to evaluate the efficacy of different therapeutic approaches in terms of disease-free survival and overall survival. At the 2010 ASCO meeting, the first positive results of a phase III clinical trial in this setting were presented: bevacizumab (15 mg/kg i.v. every 21 days) added to first-line chemotherapy and continued for an additional 15 cycles was found to prolong progression-free survival of 3.8 months in comparison to 6 cycles of chemotherapy alone or only 6 cycles of chemotherapy plus bevacizumab. In addition, positive results were announced for a second phase III trial testing bevacizumab in the same setting, but at half dose. The final assessment of the overall clinical benefit and the approval of bevacizumab in maintenance therapy by regulatory agencies is expected to be positive, as are the final results of abagovomab phase III trial MIMOSA, another antibody-based therapy tested as a maintenance treatment for advanced ovarian cancer patients. Encouraging preliminary results confirming the safety profile and the immunogenic activity of abagovomab were presented at the last ASCO meeting. The final results are expected to be released in the first half of 2011.

Induction of a less aggressive phenotype in human colon carcinoma HCT116 cells by chronic exposure to HDAC inhibitor SAHA

Histone deacetylase inhibitors (HDACis) are anticancer molecules that epigenetically modulate cell functions. Chronic exposure of HCT116 colon cancer cells to SAHA has been investigated for a better understanding of resistance mechanisms but, surprisingly, a less aggressive tumor phenotype both in vitro and in vivo was obtained after exposure to increasing concentrations of SAHA. Indeed, HCT116/SAHA cells when injected into nude mice showed a reduced engraftment and growth with respect to HCT116 cells. This difference was not observed inoculating the cells into NOD/SCID mice that, differently from nude mice, lack NK activity, thus suggesting the involvement of the native immune response in impairment of HCT116/SAHA cell growth. In agreement with this result, a growing induction of NKG2D ligand expression, MICA and MICB, that are molecular mediators of NK cell killing, was confirmed in HCT116/SAHA chronically exposed to SAHA. A reduced clonogenic efficiency was also observed in HCT116/SAHA with respect to HCT116 cells. Interestingly, even after chronic exposure to SAHA, HCT116/SAHA cells developed only a moderate resistance to SAHA both in vitro and in vivo and they acquired a collateral sensitivity to anthracyclines. These results are of note and probably rely on the fact that, having simultaneously many different targets, HDACis would require many different mutations to display high resistance index. Moreover, to understand the molecular basis of HCT116/SAHA cell phenotype a gene expression profile of cancer genes was evaluated in HCT116 incubated with SAHA for 24 h and in HCT116/SAHA cells to identify selectively regulated genes.

Antiproliferative and differentiating activities of a novel series of histone deacetylase inhibitors

Histone deacetylases are promising molecular targets for the development of antitumor agents. A novel series of histone deacetylase inhibitors of the hydroxamic acid type were synthesized for structure-activity studies. Thirteen tricyclic dibenzo-diazepine, -oxazepine, and -thiazepine analogues were studied and shown to induce variable degrees of histone H3/H4 and tubulin acetylation in a cellular model of myeloid leukemia sensitive to all-trans retinoic acid (ATRA). Multiparametric correlations between acetylation of the three substrates, tumor cell growth inhibition, and ATRA-dependent cytodifferentiation were performed, providing information on the chemical functionalities governing these activities. For two analogues, antitumor activity in the animal was demonstrated.

Antitumor activity of delimotecan against human metastatic melanoma: pharmacokinetics and molecular determinants

Delimotecan (MEN 4901/T-0128) is a new cytotoxic prodrug constituted by a camptothecin analog (T-2513) bound to carboxymethyl dextran through a triglycine linker. A significant antitumor activity of delimotecan against human metastatic melanoma xenograft model Me15392 is reported. Dacarbazine, the drug approved for the treatment of metastatic melanoma, was ineffective in this melanoma model. Pharmacokinetic studies, together with the expression analysis of mRNA for enzymes involved in delimotecan metabolism, showed that T-2513 and other cytotoxic metabolites of delimotecan (SN 38 and T-0055) are generated in greater quantities in the tumor tissue than in toxicity target tissues, such as liver, thus accounting for the antitumoral activity. Moreover, we demonstrated that human metastatic melanoma cells are able to phagocytose delimotecan and cleave it to release the cytotoxic moieties T-2513 in the tumoral environment. Further flow cytometric analysis showed a higher recruitment of macrophages in xenografted human metastatic melanoma, when compared with other human tumors. Thus, the antitumoral activity of delimotecan exerted on metastatic melanoma is due to several factors: (i) the ability of melanoma cells to phagocytose and metabolise delimotecan; (ii) the accumulation of delimotecan in tumoral mass; (iii) the recruitment of macrophage cells to the melanoma nodule and (iv) the expression in melanoma cells of a pattern of enzymes that converts delimotecan into cytotoxic metabolites. Based on these results, delimotecan might be exploited as a new anticancer agent for the therapy of metastatic melanoma because of its high efficacy and good selectivity, and therefore clinical trials for this indication are warranted.

Antitumour effect of combination treatment with Sabarubicin (MEN 10755) and cis-platin (DDP) in human lung tumour xenograft

PURPOSE

Sabarubicin (MEN 10755), a new disaccaride anthracycline, has shown greater efficacy than Doxorubicin in a large panel of preclinical models and now it is in phase II clinical trials. Its promising antitumour activity promoted considerable interest to combine Sabarubicin with other antitumour agents. Thus, the purpose of this study was to evaluate in vitro cytotoxic effects and in vivo antitumour activities produced by the combination of Sabarubicin and cisplatin (DDP).

METHODS

The antitumour effect of Sabarubicin and DDP association was investigated, in vitro and in vivo, in preclinical models of lung cancer i.e.: the non-small cell lung carcinoma (NSCLC) H460 and the small-cell lung carcinoma (SCLC) GLC4 in terms of synergism, additivity or antagonism in order to establish the best schedule for the combined treatment. Further, the correlation between antitumour activity and the pharmacokinetic parameters of the studied combination was also evaluated.

RESULTS

The drug combination in vitro was in general more cytotoxic than the single drug alone, indicating the presence of a synergistic effect in both tumour cell lines. Also, in the xenograft experiments a superior antitumoral effect was observed when Sabarubicin was combined with DDP. The antitumour efficacy of Sabarubicin (6 mg/kg q4d x 5) combined with DDP (6 mg/kg q4d x 3) greatly depended on the schedule of administration. In H460 tumour line, the sequential combination was more effective than the simultaneous administration of the two agents, although the antitumour efficacy was not dependent on the sequence of combination. On the other hand, a strong sequence-dependent effect was observed when Sabarubicin was combined with DDP in SCLC, GLC4. In particular, the highest value of LCK = 6.7 was obtained when administration of DDP followed by 24 h that of Sabarubicin. Pharmacokinetics of Sabarubicin in combination with DDP was evaluated at 6 mg/kg for both drugs with different sequential schedule. The experimental data showed no evidence for pharmacokinetics drug-drug interaction.

CONCLUSION

These preclinical results indicate the potential for a strong antitumour activity in lung tumours of the combination Sabarubicin and DDP. In particular, in SCLC the best response should be given by a sequence with administration of Sabarubicin followed 24 h later by that of DDP. Clinical trials based on these results are ongoing.

Sabarubicin (MEN10755)-induced apoptosis is independent from mtDNA in A2780 human ovarian tumor cells

BACKGROUND

The role of mitochondrial DNA (mtDNA) in anthracycline-induced apoptosis is controversial. Sabarubicin accumulates in the mitochondria of A2780 human ovarian tumor cells. The effects of this new anthracycline on the structure and the functionality of mtDNA, as well as on the apoptosis of mtDNA-depleted cells have been investigated.

MATERIALS AND METHODS

Sabarubicin-induced mtDNA cleavage was detected by Southern blotting and mitochondrial mRNA expression was analyzed by real-time PCR. Apoptosis was studied in mtDNA-depleted (theta0) and parental (theta+) A2780 cells detecting nuclear DNA fragmentation using ELISA and cytofluorimetrically using Annexin V/PI staining. Mitochondrial membrane potential was studied using the cyanine dye JC-1.

RESULTS

Sabarubicin induced mtDNA cleavage in the A2780 cells, but this damage did not affect mitochondrial mRNA expression. Apoptosis was induced by sabarubicin in theta0 as well as in theta+ cells.

CONCLUSION

The results showed that mtDNA did not influence anthracycline-induced apoptosis in A2780 cells.

Human and murine macrophages mediate activation of MEN 4901/T-0128: a new promising camptothecin analogue-polysaccharide conjugate

MEN 4901/T-0128 is a new cytotoxic prodrug constituted by the camptothecin analogue T-2513 bound to carboxymethyl dextran through a triglycine linker. MEN 4901/T-0128 was designed to target the active camptothecin at the tumour site. MEN 4901/T-0128 is weakly cytotoxic in vitro and thus T-2513 must be released from the conjugate to become active. Here, we demonstrated that human purified cathepsin B releases T-2513 from MEN 4901/T-0128 at pH values ranging from 3 to 5. pH dependency of this reaction suggests that cleavage of the linker should mainly occur in the lysosomes. As elevated cathepsin B activity has been described in macrophages, human tumour monocytic THP-1 cells differentiated into macrophage-like cells were used to study the cellular mechanisms responsible for MEN 4901/T-0128 antitumour activity. Here, we show that differentiated THP-1 internalizes MEN 4901/T-0128 efficiently in a time-dependent and concentration-dependent manner. After phagocytosis, THP-1 cells can cleave the prodrug and release T-2513 in the media. On the contrary, undifferentiated THP-1 cells or pancreatic ASPC-1 tumour cells, although expressing high levels of cathepsin B, are much less efficient in the release of cytotoxic moieties in the culture media. Moreover, normal murine macrophages, recovered from the peritoneal cavity or from the spleen, when activated (in vitro by 100 ng/ml phorbol 12-myristate-13-acetate and in vivo by 300 microl of 3% w/v thioglycollate solution), were able to release (after incubation with 10 microg/ml MEN 4901/T-0128) cytotoxic moieties in the culture supernatant, in an amount sufficient to kill human carcinoma A2780 cells. Thus, we suggest that tumour-associated macrophages may play a key role in the uptake of MEN 4901/T-0128, cleavage and local release of active moiety T-2513. This mechanism should support a tumour targeting of the cytotoxic moieties, allowing an improved antitumour efficacy/safety ratio for MEN 4901/T-0128.

NF-kappaB activation contributes to anthracycline resistance pathway in human ovarian carcinoma cell line A2780

The development of chemoresistance is a major obstacle for successful anticancer therapy. Understanding the molecular mechanisms leading to chemoresistance is a rational step to improve the therapeutic efficacy of cytotoxic drugs. Since anthracyclines play an important role in cancer chemotherapy, we have generated a human ovarian tumor cell line resistant to sabarubicin (MEN 10755), the newest anthracycline molecule in clinical development. Expression of the transporter protein MRP that affected sabarubicin uptake, and a reduced DNA topoisomerase II content in A2780/saba cells was observed. Since the poisoning of DNA topoisomerase II results in DNA damage, which is a critical signal for NF-kappaB activation, we explored if this transcription factor has a role in the chemoresistance to anthracyclines. We showed a reduced NF-kappaB activation in the resistant cell line. Moreover, qualitative changes in NF-kappaB dimer formation between the two cell lines were observed. In agreement with the hypothesis of a role of NF-kappaB in mediating drug resistance, we showed that the pharmacological inhibition of NF-kappaB activation attenuated drug resistance in A2780/saba cells whereas it had no effect in A2780 cells. Altogether, these findings show that anthracycline resistance in A2780 cell lines is due to the coexpression of several molecular mechanisms.

Sabarubicin- (MEN 10755) and paclitaxel show different kinetics in nuclear factor-kappaB (NF-kB) activation: effect of parthenolide on their cytotoxicity

BACKGROUND

Several antitumor drugs have been described to induce nuclear factor kappaB (NF-kappaB), but results about its role in regulating apoptotic cell death are quite controversial. In this paper, we studied NF-kappaB induced by the two anticancer agents Sabarubicin (MEN 10755) and paclitaxel (Taxol) and the effects of its pharmacological inhibition.

MATERIALS AND METHODS

In the human colon cancer cell line HCT-116, we investigated NF-kappaB activation induced by the two anticancer agents using electrophoretic mobility shift assay (EMSA), while drug-induced cytotoxicity was measured by trypan blue staining. Apoptosis was analyzed using a cell death detection enzyme-linked immunosorbent assay (ELISA) kit, flow cytometry and caspase-3 activation assay.

RESULTS

The combination with the NF-kappaB inhibitorparthenolide increased Sabarubicin- but not paclitaxel-induced cell death. EMSA experiments demonstrated that the two antitumor drugs induced NF-kappaB complexes with different kinetics but similar subunit composition. Moreover, Sabarubicin elicited NF-kappaB activation definitely earlier than DNA fragmentation, whereas with paclitaxel the kinetics of the two phenomena were similar.

Involvement of nitric oxide in both central and peripheral haemodynamic effect of d/l-nebivolol and its enantiomers in rats

The cardiovascular profile of the racemate D/L-nebivolol and its enantiomers administered by intravenous (i.v.) or by intracerebroventricular (i.c.v.) route was investigated in anaesthetized normotensive rats. D/L-Nebivolol (0.1-0.5 mg/kg) induced a dose-related reduction in blood pressure when administered by i.c.v. route. These hypotensive effects were more marked as compared to those achieved by peripheral administration of D/L-nebivolol (0.1-1 mg/kg i.v.). Both enantiomers contributed to the hypotensive effect of D/L-nebivolol by i.c.v. route, while the effects of the drug on blood pressure by i.v. route were due to the d-enantiomer. The bradycardic effect of the racemic form given i.v. was dose-related and, at the highest dose (1 mg/kg), was more pronounced as compared to i.c.v. route. D-Nebivolol was responsible for chronotropic effects by both the i.v. and i.c.v. route, although by i.c.v. route L-nebivolol also induced a reduction in heart rate. The nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) administered at 5 mg/kg i.v. bolus + 0.1 mg/kg/min infusion or at 2.5 mg/kg i.c.v. counteracted the effects of D/L-nebivolol (either 1 mg/kg i.v. or 0.5 mg/kg i.c.v.) on blood pressure, while it did not inhibit the cardiovascular changes induced by isoprenaline (300 ng/kg i.v.) or calcitonin gene-related peptide (CGRP; 400 ng/kg i.v.). In addition, i.c.v. effects of D/L-nebivolol on blood pressure and heart rate were not affected by pre-treatment with atropine (2 mg/kg i.v.). The present findings demonstrate that D/L-nebivolol produced haemodynamic changes following both peripheral and central administration; these latter findings are mainly due to its L-enantiomer and these effects involve the L-arginine/nitric oxide pathway.

Effects of Common Buffer Systems on Drug Activity: The Case of Clerocidin

Two widely used biological buffers [tris(hydroxymethyl)aminomethane (TRIS) and phosphate] covalently react with the topoisomerase II inhibitor clerocidin, affecting the drug's reactivity profile. Comprehensive analytical and structural analysis obtained by LC/MS, MS/MS, NMR, and IR techniques shows that these buffers form reversible and irreversible adducts through reactions with chemical groups, such as carbonyls, aldehydes, and epoxide. Analysis of the kinetic data on adducts formation suggests two parallel mechanisms for the inhibition of drug activity. The first involves modulation of the reactivity of the epoxide group obtained by elimination of the spiro system and relief of ring strain. This effect does not abolish epoxide reactivity and is more evident for the TRIS adduct, which can count on intramolecular stabilization of the form devoid of the spiro system. The second mechanism involves the slow nucleophilic attack to the epoxide ring, which results in permanent deactivation of the functional group responsible for topoisomerase II inhibition. This effect is predominant in phosphate buffer and is more evident for longer reaction times. These results provide a compelling reminder that the activity of chemically complex drugs in biological systems can be severely altered by buffer interactions, which may not be immediately predictable from the identity of the active group(s) and may require a more detailed knowledge of the subtle effects induced by vicinal groups.

MEN15658: a new promising anti-tumoral drug active on resistant tumor cells

We describe the identification of MEN15658, a molecule characterized by a promising cytotoxic effect against human tumor cell lines, including platinum- and anthracycline-resistant ovarian carcinoma. MEN15658 induces p53 accumulation, and activation of gadd-45, p21, c-fos and bcl-2 family genes in human ovarian carcinoma A2780 cell line. The compound causes a block in S phase of the cell cycle, inducing apoptotic cell death, thus suggesting an involvement of DNA damage in the MEN15658 effect on tumor cells. The anti-tumoral activity observed against the human ovarian carcinoma A2780 cell line xenotransplanted in nude mice makes this compound a new promising anti-tumoral drug.

CD137 and CD137 ligand constitutively coexpressed on human T and B leukemia cells signal proliferation and survival

CD137, a member of the tumor necrosis factor receptor family, provides expansion and survival signal to T cells. Its ligand, CD137L, in addition to its ability to costimulate T cells, signals back into antigen presenting cells promoting their activation and differentiation. Recently, CD137 has been proposed as a therapeutic target to improve and sustain anticancer immune response. Several activated T leukemia and B lymphoma cell lines expressed CD137 or CD137L, respectively, and soluble CD137L has been found in sera of leukemia patients. However, the functionality and role of these costimulatory molecules in hematologic malignancies are until now unknown. Interestingly, we observed constitutive CD137 and CD137L coexpression on both human T and B leukemia cell lines. The constitutive CD137 expression on unstimulated T or B leukemia cells presents some differences compared to CD137 expressed on PMA/ionomycin-activated T leukemia cells. Surprisingly, in spite of the low expression level, both tumor CD137 and CD137L molecules signaled in T and B leukemia cells inducing proliferation and prolonging survival. In addition, CD137/CD137L system ligation opposed the anticancer drug cytotoxic effects, reducing the apoptotic DNA fragmentation and stimulating proliferation of doxorubicin-escaped leukemia cells. Although the role of leukemia CD137/CD137L system in vivo is unknown, these data suggest that these costimulatory molecules might confer an advantage to hematologic tumors promoting survival, sustaining cellular growth and contributing to drug resistance.