Abstract 5859: HER2-targeted thorium-227 conjugate (HER2-TTC): Efficacy in preclinical models of trastuzumab and T-DM1 resistance

The human epidermal growth factor receptor 2 (HER2) is encoded by the proto-oncogene c-erbB-2 and initiates downstream signaling pathways leading to cell proliferation and tumorigenesis. HER2 is overexpressed in several cancer (Ca) types and is one of the most strongly validated targets for the treatment of breast and gastric cancer serving as both a prognostic and predictive biomarker. Several HER2-targeting antibodies as well as antibody-drug conjugates are either approved or are in clinical development. Prolonged treatment with monoclonal antibodies and antibody drug conjugates have resulted in development of resistance and so there is still an unmet medical need for drugs of new mechanism of action targeting this important receptor system. We describe herein the generation of a high energy, alpha-particle emitting HER2 targeted thorium-227 antibody-chelator conjugate. HER2-TTC consists of the humanized HER2 targeting IgG1 antibody (trastuzumab) covalently linked via an amide bond to a 3,2-hydroxypyridino-based chelator moiety, enabling efficient radiolabeling with the alpha particle emitting radionuclide thorium-227 (Th-227). HER2-TTC was prepared at high radiochemical yield and purity. When tested for binding to recombinant HER2, HER2-TTC was shown to retain comparable binding affinity to trastuzumab. In vitro cytotoxicity experiments were performed on 8 cell lines with different HER2 expression levels (from 7 000 - 500 000 mAbs bound/ cell as determined by FACS) of breast, ovarian, gastric and lung cancer origin. HER2-TTC demonstrated target mediated in vitro cytotoxicity in the pM-range. In vivo biodistribution and anti-tumor efficacy of HER2-TTC was evaluated in the dose range 100-500 kBq/kg at a protein dose of 0.14 mg/kg and i.v. injection in the s.c. KPL-4 breast and Calu-3 lung model previously described to be resistant to trastuzumab. The biodistribution study demonstrated specific tumor accumulation of HER2-TTC in both models with a maximum of 77 and 50 %ID/g 227Th at t = 168 h post dose (decay corrected to T0), respectively. Significant antitumor efficacy was shown for HER2-TTC in the JIMT-1 s.c. breast Ca xenograft model resistant to trastuzumab and T-DM1. The promising preclinical anti-tumor activity supports the development of the targeted alpha therapeutic HER2-TTC for the treatment of trastuzumab and T-DM1 resistant patients.

Citation Format: Jenny Karlsson, Urs B. Hagemann, Christoph Schatz, Derek Grant, Alexander Kristian, Christine Ellingsen, Dessislava Mihaylova, Solene Geraudie, Bård Indrevoll, Uta Wirnitzer, Roger M. Bjerke, Olav B. Ryan, Carl F. Nising, Dominik Mumberg, Alan Cuthbertson. HER2-targeted thorium-227 conjugate (HER2-TTC): Efficacy in preclinical models of trastuzumab and T-DM1 resistance [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 5859. doi:10.1158/1538-7445.AM2017-5859

Abstract 413: Validation of an antibody independent tool for patient selection: RNA in situ hybridization detects Met expression levels predictive for response to Met inhibition by Bay 853474

This study was performed in order to validate RNA in situ hybridization (RNA ISH) as tool for patient selection. Met expression was analyzed in a matched sample set of FFPE versus fresh frozen tumor samples comprising 20 cases of gastric cancer. Classical immunohistochemistry using the antibody SP44 and RNA ISH (RNAscope by ACD) were used to detect c-met expression in FFPE material. The results were confirmed by sandwich-immunoassays on Met and its phosphorylation on tyrosine 1349 (MSD) as well as mass spectrometry. The level of functional relevance was determined by testing a set of cell lines comprising some with genomic amplification of the met gene as well as some non-amplified lines showing different expression levels. Among gastric cancer cell lines only those with met amplification respond to treatment with the small molecule Met inhibitor Bay 853474. The cell line result generates a responder hypothesis that can be used to define a cutoff for clinical samples. 2 of the 20 investigated clinical samples were shown to have high level Met expression by RNA ISH and IHC that could be confirmed by sandwich-immunoassays also showing high level of functional activity by phosphotyrosine 1349. Met expression in these cases was also confirmed by mass spectrometry. Expression levels and functional activity in these 2 cases were in the range that predicts response to treatment as established with gastric cancer cell lines. Determination of predictive biomarkers by immunohistochemistry can be limited due to lack of high quality antibodies of sufficient specificity. Due to its high specificity, RNA in situ hybridization is a technique that can be used to confirm the findings obtained by immunohistochemistry and may potentially even replace immunohistochemistry it if no suitable antibodies are available or not specific enough e.g. to discriminate between closely related protein isoforms. We show the biological relevance of RNA in situ hybridization on FFPE samples by correlation with immunohistochemistry, ELISA based approaches and mass spectrometry. RNA ISH is shown to be specific and sensitive enough to identify cases of functionally relevant MET overexpression levels in gastric cancers and can be used to select patients for treatment.

Citation Format: Oliver von Ahsen, Thomas Krahn, Christoph Schatz. Validation of an antibody independent tool for patient selection: RNA in situ hybridization detects Met expression levels predictive for response to Met inhibition by Bay 853474. [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 413.

Abstract 1684: Preclinical anti-tumor efficacy of FGFR2-ADC BAY 1187982 in patient-derived gastric, breast and ovarian cancer models

Antibody-drug conjugates (ADC) represent a promising therapeutic approach for treatment of cancer. We have developed a novel ADC directed against fibroblast growth factor receptor 2 (FGFR2). FGFR2 is overexpressed in several cancer indications, such as gastric, breast, and ovarian cancer and thus represents a potential therapeutic target for treatment of FGFR2-positive cancer patients with ADC-based therapy.

FGFR2-ADC consists of a fully human anti-FGFR2-Ab (BAY 1179470) conjugated via a stable linker to a novel auristatin cytotoxic agent licensed from Seattle Genetics. FGFR2-ADC exhibits low nM to sub-nM potency in vitro in a panel of FGFR2-positive cancer cells lines (SNU-16, MFM-223, NCI-H716) while being inactive against FGFR2-low or -negative cell lines (MDA-MB-231, HEK-293, BaF/3) and highly selective versus a control ADC.

FGFR2-ADC is highly efficacious in monotherapy and results in tumor growth inhibition in the gastric cancer xenograft model SNU-16 and tumor regression in the breast cancer xenograft model MFM-223. FGFR2-ADC induces tumor stasis in the colorectal cancer xenograft model NCI-H716 and regrown tumors are sensitive to a second treatment cycle of FGFR2-ADC.

FGFR2-ADC shows high efficacy in vivo in monotherapy in patient-derived (PDX) FGFR2-positive murine xenograft models, e.g. in the ovarian cancer model OV30-0511A. FGFR2-ADC is also efficacious in the gastric cancer PDX model GC10-0608 and the breast cancer model MAXF857.

The toxophore metabolite of FGFR2-ADC was more than 30-fold enriched in tumors versus other organs (liver, spleen, kidneys) in NCI-H716 tumor-bearing mice.

Based on the preclinical efficacy, PK and tolerability data, evaluation of FGFR2-ADC in cancer patients appears warranted. A Phase I study is planned.

Citation Format: Anette Sommer, Charlotte Kopitz, Christoph Schatz, Ruprecht Zierz, Joachim Schuhmacher, Sabine Wittemer-Rump, Klaas Prins, Manuela Braun, Frank Reetz, Bertolt Kreft, Hung T. Huynh, Karl Ziegelbauer. Preclinical anti-tumor efficacy of FGFR2-ADC BAY 1187982 in patient-derived gastric, breast and ovarian cancer models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1684. doi:10.1158/1538-7445.AM2015-1684

Abstract 1683: Pharmacokinetic/pharmacodynamic (PK/PD) and toxicokinetic/toxicodynamic (TK/TD) modeling of preclinical data of FGFR2-ADC (BAY 1187982) to guide dosing in phase 1

BAY 1187982 is an antibody drug conjugate (ADC) directed against fibroblast growth factor receptor 2 (FGFR2). FGFR2 is overexpressed in several cancer indications, such as gastric, breast, and ovarian cancer. Anti-tumor efficacy of BAY 1187982 has been demonstrated in several FGFR2-positive cancer cell line as well as patient-derived xenograft models. Toxicology findings from repeated dose preclinical safety studies in monkeys indicated effects related to the liver, kidney, heart and coagulation system. To predict the therapeutic index of BAY 1187982 in humans and to support the design of the first-in-human (FIH) study with respect to selection of dose and regimen, preclinical efficacy and toxicity findings were quantified. All available preclinical PK, TK, tumor response and toxicity data from mouse models and monkey studies were used to create a model framework to describe the PK, TK, PK/PD and TK/TD relationship as functions of BAY 1187982 dose, regimen and time. Human PK parameters based on scaling from monkey were used to predict PK profiles in humans for a range of doses and schedules. These sets of predicted exposure models were combined with the PK/PD as well as the TK/TD model to assess the expected efficacy (according to RECIST criteria) and toxicity range in humans, respectively. The dosing schedule leading to the largest therapeutic index and the dose escalation schema for the FIH study were determined. The FIH study is currently under preparation.

Citation Format: Sabine Wittemer-Rump, Anette Sommer, Charlotte Kopitz, Hung Huynh, Christoph Schatz, Ruprecht Zierz, Manuela Braun, Kirstin Meyer, Dirk Laurent, Jörg Lippert, Klaas Prins. Pharmacokinetic/pharmacodynamic (PK/PD) and toxicokinetic/toxicodynamic (TK/TD) modeling of preclinical data of FGFR2-ADC (BAY 1187982) to guide dosing in phase 1. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1683. doi:10.1158/1538-7445.AM2015-1683

Abstract 4491: FGFR2-ADC potently and selectively inhibits growth of gastric and breast cancer xenograft models

Antibody-drug conjugates (ADCs) represent a promising therapeutic approach for treatment of cancer. We have developed a novel ADC directed against fibroblast growth factor receptor 2 (FGFR2). FGFR2 is overexpressed in several cancer indications, such as gastric cancer and breast cancer, thus representing an interesting therapeutic target for the treatment of FGFR2 positive cancer patients with an ADC-based therapy. The FGFR2-ADC consists of the fully human anti-FGFR2-mAb BAY 1179470 conjugated via a stable linker to a novel auristatin cytotoxic agent (technology licensed from Seattle Genetics). The FGFR2-mAb BAY 1179470, which is cross-reactive with human, mouse, rat and monkey, induces internalization of FGFR2. Quantitative data on FGFR2 antibody bound per cell (ABC) were determined with the QuantiBrite assay using BAY 1179470. FGFR2-ADC has a potency in the single digit nM to sub nM range in a panel of FGFR2-positive cells lines (e.g., SNU-16, KatoIII, SUM52-PE, MFM-223) and shows more than 100-fold selectivity versus FGFR2-negative cell lines. High levels of FGFR2 on cancer cells correlate with internalization efficacy and cytotoxic activity in vitro. FGFR2-ADC is highly efficacious in monotherapy and results in tumor growth inhibition in the gastric cancer xenograft model SNU-16 and tumor regression in the breast cancer xenograft model MFM-223. At doses efficacious in mice, FGFR2-ADC is well tolerated. The pre-clinical efficacy and tolerability data obtained for FGFR2-ADC suggest a therapeutic index and support clinical testing.

Citation Format: Anette Sommer, Carl F. Nising, Christoph Mahlert, Charlotte C. Kopitz, Hans-Georg Lerchen, Simone Greven, Beatrix Stelte-Ludwig, Joachim Schuhmacher, Ruprecht Zierz, Sabine Wittemer-Rump, Christoph Schatz, Frank Reetz, Heiner Apeler, Rolf Jautelat, Bertolt Kreft, Karl Ziegelbauer. FGFR2-ADC potently and selectively inhibits growth of gastric and breast cancer xenograft models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4491. doi:10.1158/1538-7445.AM2014-4491

Abstract 2629: PIK3CA mutation promotes tumor cell invasion and migration independently from AKT and mTOR kinase in cancer cells

Although the role of phosphoinositide-3 kinase (PI3K) in promoting tumorigenesis, tumor cell survival, proliferation and metabolism has been extensively evaluated, the mechanisms of other oncogenic processes mediated by PI3K have not been fully addressed. We report here a novel molecular mechanism by which PI3K mediates tumor cell invasion and migration using isogenic cell lines and highly selective PI3K pathway inhibitors. First of all, using a set of MCF10A-derived isogenic cell lines with PIK3CAH1047R, PTEN-deletion, or AKTE17K mutations, we found that activating the PIK3CA mutation, but not PTEN-deletion or AKT mutation, promoted tumor cell migration in a wound healing assay. Treatment of the PIK3CAH1047R isogenic cell line with a highly selective PI3K inhibitor (BAY 80-6946) effectively blocked tumor cell migration. Interestingly, neither allosteric AKT inhibitor nor mTOR kinase inhibitors were able to inhibit PIK3CA-stimulated cell migration although both AKT and mTOR kinase inhibitors potently inhibited AKT phosphorylation in these cells. In contrast, AKT inhibition enhanced the migration of PIK3CA mutant isogenic cells. This result revealed a novel AKT- and mTOR-independent mechanism by which activating PI3K mutation stimulates tumor cell migration. This conclusion was further confirmed in a panel of gastric cancer cell line in both wound healing and migration assays. Additional mechanistic experiments are being performed to examine downstream signaling events and will be presented. Taken together, these data suggest a role of PI3K in contributing to tumour metastasis independent of the canonical PI3K-AKT-mTOR axis and further validation of using AKT inhibitor for the treatment of metastatic PIK3CA mutant tumors to be conducted.

Citation Format: Bhaskar Bhattachara, Enrico Stasik, Sarah Low, Andrea Sturz, Christoph Schatz, Richie Soong, Ningshu Liu. PIK3CA mutation promotes tumor cell invasion and migration independently from AKT and mTOR kinase in cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2629. doi:10.1158/1538-7445.AM2013-2629

BAY 1000394, a novel cyclin-dependent kinase inhibitor, with potent antitumor activity in mono- and in combination treatment upon oral application

Deregulated activity of cyclin-dependent kinases (CDK) results in loss of cell-cycle checkpoint function and increased expression of antiapoptotic proteins, which has been directly linked to the molecular pathology of cancer. BAY 1000394 inhibits the activity of cell-cycle CDKs CDK1, CDK2, CDK3, CDK4, and of transcriptional CDKs CDK7 and CDK9 with IC(50) values in the range between 5 and 25 nmol/L. Cell proliferation was inhibited at low nanomolar concentration in a broad spectrum of human cancer cell lines. In cell-based assays, the inhibition of phosphorylation of the CDK substrates retinoblastoma protein, nucleophosmin, and RNA polymerase II was shown. Cell-cycle profiles were consistent with inhibition of CDK 1, 2, and 4 as shown in cell-cycle block and release experiments. The physicochemical and pharmacokinetic properties of BAY 1000394 facilitate rapid absorption and moderate oral bioavailability. The compound potently inhibits growth of various human tumor xenografts on athymic mice including models of chemotherapy resistance upon oral dosing. Furthermore, BAY 1000394 shows more than additive efficacy when combined with cisplatin and etoposide. These results suggest that BAY 1000394 is a potent pan-CDK inhibitor and a novel oral cytotoxic agent currently in phase I clinical trials.

Cancer therapy monitoring in xenografts by quantitative analysis of circulating tumor DNA

CONTEXT

Circulating tumor DNA (ctDNA) is a promising biomarker in cancer.

MATERIALS AND METHODS

We generated xenograft models of cancer and detected ctDNA in plasma by qRCR targeting human AluJ sequences.

RESULTS

Our assay reached single cell sensitivity in vitro and a correlation between ctDNA amount and tumor size was observed in vivo. Treatment with a mitogen activated protein kinase kinase (MEK)-inhibitor (BAY 869766) reduced ctDNA levels. Using this assay, we also confirmed that high levels of cell-free DNA are found in cancer patients compared to healthy individuals.

DISCUSSION AND CONCLUSION

We show that ctDNA may be useful biomarker for monitoring tumor growth and treatment response.

Abstract 1754: Identification of BAY 94-9343, a mesothelin antibody-drug conjugate (ADC): Characterization and anti-tumor activity in mesothelin-positive preclinical tumor models

Monoclonal antibodies have proven to be very effective in the treatment of various cancers, including solid tumors. For example, HERCEPTIN® and Erbitux® are successfully used to treat HER2-positive breast cancer and EGFR-positive colorectal cancer, respectively.

Conjugation of cytotoxic drugs to antibodies represents a promising approach to improve cancer therapy. Antibody-drug conjugates (ADCs) are able to deliver highly potent toxophores to tumors while at the same time reducing systemic toxicity. Promising efficacy and tolerability profiles of ADCs have been observed in clinical trials including Hodgkin lymphoma (brentuximab vedotin) and breast cancer (trastuzumab-DM1), thus, development of new ADCs targeting tumor- associated antigens has potential to identifiy novel cancer therapeutics.

Mesothelin, a glycoprotein expressed in mesothelial cells found in the membrane lining of the peritoneal and pleural cavities, is overexpressed in all mesotheliomas as well as many ovarian and pancreatic cancers. Due to its limited expression on normal tissues and higher expression in a number of tumor types, mesothelin represents an attractive ADC target.

BAY 94-9343 consists of a fully human anti-mesothelin IgG1 antibody conjugated to the potent tubulin-binding drug DM4 with an average of 3.2 drug molecules per antibody. The resulting ADC bound to human recombinant mesothelin with high affinity (Kd = 15nM) leading to antigen-dependent internalization and potent cytotoxicity (nanomolar range in vitro IC50) in tumor cells that express mesothelin either endogenously or exogenously, but not in mesothelin-negative cells. In vivo, BAY 94-9343 demonstrated dose-dependent, mesothelin-specific anti-tumor efficacy in subcutaneous and orthotopic xenograft models at doses between 2.5 and 10 mg/kg using a Q3Dx3 schedule. Endogenously expressing mesothelin tumor models included sc and orthotopic OVCAR3 (ovarian), sc BxPC-3 (pancreatic) and sc NCI-H226 (mesothelioma). Furthermore, in mesothelin-positive patient-derived preclinical tumor models of both platinum-resistant ovarian cancer and gemcitabine-resistant pancreatic cancer, BAY 94-9343 exhibited high anti-tumor efficacy leading to partial and complete tumor regressions with a 10mg/kg Q3Dx3 dosing schedule. This ADC was well tolerated in mice at 10mg/kg (Q3Dx3) without any evidence of body weight loss, compared to either cisplatin or gemcitabine treatments. In summary, BAY 94-9343 is a mesothelin-targeted ADC with promising preclinical anti-tumor activity for mesothelin-positive tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1754. doi:10.1158/1538-7445.AM2011-1754

Abstract P2-06-13: Pathway Profiling of Signal Transduction Proteins in Paired Tumor and Adjacent Normal Tissues Obtained from Breast Cancer Patients

Background: Targeted therapeutic strategies are currently limited to patients with hormone receptors and/or HER2 positive disease in breast cancer (BCA) treatment. However, patients often develop resistance to these therapies. The ability to functionally profile a whole spectrum of pathway proteins (and their variants) in tumor may provide valuable information about the potential mechanism for drug resistance and evidence for rational selection of suitable targeted therapies. Here we report a comprehensive profile of HER1, HER2, p95HER2, HER3, cMET, IGF1R, PI3K, Shc, AKT and other signal transduction pathway proteins in BCA tissues and their matched adjacent normal tissues (ANTs). Methods: A multiplexed Collaborative Proximity ImmunoAssay (COPIA), antibody-microarray platform requiring co-localization of 2 detector antibodies on captured biomarker proteins has been used for comprehensive pathway analysis. Channeling events between 2 detector enzymes (glucose oxidase & horse radish peroxidase) in proximity enabled the profiling of the target biomarkers with extreme sensitivity and specificity, and a direct comparison to electrochemiluminescence based immunoassay platform (MSD) was performed for pathway proteins in tumor vs. ANTs for their expression and activation in samples collected from 20 BCA patients. Results: Three dilutions of lysate (10ug, 1ug, 0.1ug) were analyzed for quantitative differential pathway modulation for COPIA.

- Substantially higher cytokeratin (CK) levels were found in 16/20 tumor samples when compared to paired-ANT; 3/20 samples showed high levels of CK in ANTs. Substantial levels of HER3 and IGF1R expression was detected in 9 and 5 tumor samples respectively.

- Over-expression of HER2 with high degree of activation was found in 2 patients. In one of the HER2-overexpressing patients, HER3 was also highly expressed and moderately phosphorylated. Co-expression of cMET and IGF1R was evident as well.

- A significant degree of HER2 phosphorylation was found in many patients with low level HER2 expression; this may be due to co-expression of high level of HER3 and other RTKs with trans-activational potential. Evidence of activated PI3K complex will be reported.

- In direct comparison to MSD, COPIA detected activated pathway proteins in samples that were not detectable with MSD. MSD was sensitive enough to detect the very extreme cases. COPIA appeared to be a more desirable method for detection of protein expression and activation for samples with limited availability. The distinct pathway modulation in each patient (detected by COPIA) will be reported.

Discussion: COPIA was used to detect the differential expression and phosphorylation of HER2, other RTKs and pathway proteins in 20 paired tumor and matched ANTs. As this platform requires magnitudes lower amounts of specimen, it can be used to profile tumors at different metastatic sites and could provide comprehensive metastatic profiles. The comprehensive functional pathway profiling of tumor specimen may provide insightful information for potential drug-resistant mechanisms and may guide appropriate selection of targeted drug-combinations or drug-sequencing.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-06-13.

Abstract 2577: In vitro and in vivo efficacy of the anti-MN immunoconjugate BAY 79-4620, MN-IC, in MN (CAIX) expressing preclinical tumor models

BAY 79-4620 is a novel immunoconjugate consisting of a fully human monoclonal antibody directed against MN (carbonic anhydrase IX; CAIX) conjugated with the auristatin derivative MMAE currently in Phase I testing. CAIX is overexpressed in a range of tumor types, such as gastric cancer, non-small cell lung cancer, pancreatic cancer or colorectal cancer. CAIX expression is regulated by HIF-1α, making this protein a marker associated with tumor hypoxia. Expression of this protein has been linked to higher aggressiveness of tumors and is predictive of poor prognosis in several cancers.

We report on the pharmacological profile of a novel immunoconjugate directed against MN (CAIX) conjugated with the auristatin derivative MMAE to a fully human anti-MN (CAIX) monoclonal antibody (BAY 79-4620). In vitro studies showed the specific binding and internalization of BAY 79-4620 into CAIX-expressing tumor cells. Intracellular release of the tubulin-inhibiting toxophore MMAE led to mitotic arrest and specific cell kill of tumor cells, with EC50s in the low nanomolar range in most CAIX-positive tumor cell lines tested. In CAIX-negative tumor cell lines, a cytotoxic effect of BAY 79-4620 was seen at only very high doses. Cytotoxicity of this immunoconjugate depends on both CAIX expression and sensitivity of tumor cells to tubulin inhibitors. In vivo activity of the CAIX targeted Mab-MMAE conjugate resulted in higher efficacy (minimum effective dose (MED) of 0.625mg/kg in the HeLa-MaTu model, Q4Dx3 dosing schedule) compared to the systemic administration of either free MMAE toxophore (MED not achieved) or unconjugated anti-CAIX antibody which lacked efficacy in all models tested. Tumor regressions (in 80% of the animals) were achieved at doses of immunoconjugate as low as 1.25mg/kg while higher doses up to 10 mg/kg resulted in complete tumor eradication (in 90% of the animals treated). Efficacy in the HT29 model tested was schedule independent when comparing single dose, Q7Dx2 and Q4Dx3 schedules. The in vivo mode of action of the immunoconjugate was confirmed by tubulin staining in the tumor sections. Treatment with the immunoconjugate was found to be less toxic than that with free MMAE. The maximum tolerated dose of BAY 79-4620 in mice was 60mg/kg, which in terms of toxophore delivered exceeds the LD50 of MMAE (1mg/kg).

In summary, these results demonstrate that targeted delivery of MMAE resulted in higher efficacy of BAY 79-4620 in tumor models with high CAIX expression. The immunoconjugate BAY 79-4620 currently in Phase I testing is a promising novel agent for the treatment of gastric, non-small cell lung, pancreatic, colorectal and other MN (CAIX)-positive tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2577.

Abstract 3883: Pharmacologic profile of the oral novel pan-CDK inhibitor BAY 1000394 in chemosensitive and chemorefractory tumor models

We report on the pharmacological profile of the novel pan-CDK inhibitor BAY 1000394. Loss of cell cycle control and increased resistance to apoptosis represent major hallmarks of cancer. Cyclin-dependent kinases (CDKs) belong to a family of serine/threonine kinases which associate with an activating cyclin regulatory subunit. Cell cycle CDKs 1, 2, 4 & 6 are required for the correct timing and order of the events of the cell division cycle, whereas non-cell cycle CDKs 7 and 9 have been shown to be involved in gene transcription via regulation of RNA polymerase II activity. Deregulated CDK activity results in loss of cell cycle checkpoint function and increased expression of anti-apoptotic proteins, which has been directly linked to the molecular pathology of cancer. BAY 1000394 is a nanomolar pan CDK inhibitor (IC50s: CDK1/CycB, 7 nM; CDK2/CycE, 9 nM; CDK4/CycD1, 11 nM; CDK9/CycT1, <10 nM). This inhibitor shows a broad spectrum profile of cell proliferation inhibition carried out in a panel of 26 human tumor cell lines with a mean IC50 of 16 nM (8-37 nM). The cellular activity of BAY 1000394 was independent of the presence of functional p53 or retinoblastoma (Rb) tumor suppressor proteins. BAY 1000394 induced disappearance of the hyperphosphorylated form of Rb protein in MCF7 and HCT116 tumor cells indicating intracellular inhibition of CDK2 and CDK4. Furthermore, the compound inhibited the phosphorylation of the mitotic CDK1 substrate protein nucleophosmin in HeLa cells. Cell cycle profiles of BAY 1000394 treated HeLa cells were consistent with inhibition of CDK 1, 2 and 4 as demonstrated in cell cycle block and release experiments. A robust decrease of viability of non-proliferating peripheral blood mononuclear cells isolated from a B-CLL patient (EC50: 15 nM) was observed and indicated inhibition of intracellular CDK9. Oral dosing of BAY 1000394 at various schedules (QD or BID x 2 and 5 days off) potently inhibited growth of human cervical HeLa-MaTu xenograft tumors in a dose-dependent manner. The MTD for BAY 1000394 was found to be 2.0 mg/kg on QD schedule and 2.5 mg/kg on a BID intermittent schedule. At these two doses and schedules tumor growth inhibition (TGI) of 104% and 106% was achieved in this model. A single oral dose of 2.0 mg/kg of BAY 1000394 resulted in complete suppression of the hyperphosphorylated form of Rb protein in HeLa-MaTu tumor tissue for at least 7 hrs. BAY 1000394 was also highly efficacious in a paclitaxel-refractory HeLa-MaTu-ADR Res xenograft model, and in a cisplatin-refractory A2780-Cis human ovarian xenograft model. Furthermore, the growth of human colorectal HCT116 tumors in nude rats treated on once daily (QD) or on intermittent (BID x 2 and 5 days off) schedules was strongly inhibited (TGI of 85 - 88%). In conclusion, BAY 1000394 is a highly potent oral pan-CDK inhibitor with a pharmacological profile suggesting activity in a broad range of histological tumor subtypes.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3883.

Recombinant vaccinia virus encoding human MUC1 and IL2 as immunotherapy in patients with breast cancer

Polymorphic epithelial mucin, encoded by the MUC1 gene, is present at the apical surface of glandular epithelial cells. It is over-expressed and aberrantly glycosylated in most breast tumors, resulting in an antigenically distinct molecule and a potential target for immunotherapy. This transmembrane protein, when produced by tumor cells, is often cleaved into the circulation, where it is detectable as a tumor marker (CA 15.3) by various antibodies, allowing for early detection of recurrences and evaluation of treatment efficacy. The objective of the current study was to examine the clinical and environmental safety and immunogenicity of a live recombinant vaccinia virus expressing the human MUC1 and IL2 genes (VV TG5058), referred to here as TG1031. The study was an open-label phase 1 and 2 trial in nine patients with advanced inoperable breast cancer recurrences to the chest wall. The patients were vaccinated intramuscularly with a single dose of TG1031; three patients were treated at each of three progressive dose levels ranging from 5x10(5) to 5x10(7) plaque-forming units. A boost injection at their original dose level was administered in patients responding immunologically, clinically, or both. Vaccination resulted in no significant clinical adverse effects, and there was no environmental contamination by live TG1031. All patients had been vaccinated as children, and patients treated at the highest dose level mounted a significant anti-vaccinia antibody response. None of the nine patients had a significant increase in MUC1-specific antibody titers after one single injection, whereas five patients had a detectable increase in vaccinia virus antibody titers. Peripheral blood mononuclear cells of one patient at the intermediate dose level showed a proliferative response to in vitro culture with vaccinia virus, with a stimulation index of 6. A second patient treated at the intermediate dose level had a stimulation index of 7 to MUC1 peptide and of 14 after a boost injection. This patient had a concomitant decrease in carcinoembryonic antigen serum levels and remained clinically stable for 10 weeks. Evidence of MUC1-specific cytotoxic T lymphocytes was detected in two patients. Immunohistochemical analysis revealed an increase in T memory cells (CD45RO) in tumor biopsies after vaccination. The absence of serious adverse events, together with the documentation of immune stimulations in vivo, warrant the further use of TG1031 in immunotherapy trials of breast cancer.

Gene therapy study of cytokine-transfected xenogeneic cells (Vero-interleukin-2) in patients with metastatic solid tumors

On the basis of compelling preclinical data in cats and dogs, we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human interleukin (IL)-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to computed tomography- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. The endpoints of the study were feasibility, toxicity, and the clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological, and molecular analyses were performed on biopsy specimens of tumors and blood samples before, during, and after treatment. Treatment was well tolerated, and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft-tissue sarcoma showed a reduction of >90% and >50% of the volume of two distant, noninjected metastases, lasting for 29+ and 26 months, respectively. Four other patients showed stabilization of their disease for 3-9 months; of these patients, one with melanoma developed marked vitiligo. We conclude that repeated injections of < or =5 x 10(7) Vero-IL-2 cells are feasible and safe in heavily pretreated patients with advanced solid tumors. An additional evaluation of an intratumoral application of Vero-IL-2 seems warranted.