Preclinical rationale for combining an EGFR antibody with cisplatin/gemcitabine for the treatment of NSCLC

BACKGROUND

Although the addition of epidermal growth factor receptor (EGFR) antibodies to various platinum-based chemotherapy regimens for non-small cell lung cancer (NSCLC) is being actively pursued in the clinic, rationale for the prioritization of specific regimens is lacking.

MATERIALS AND METHODS

We evaluated the antitumor effects of necitumumab, a recombinant human IgG1 antibody targeting EGFR, in combination with cisplatin plus gemcitabine, pemetrexed, or paclitaxel in a panel of 9 subcutaneous tumor models of NSCLC established in nu/nu athymic mice.

RESULTS

Necitumumab in combination with cisplatin/gemcitabine was particularly effective, although interestingly, the mechanisms underlying these benefits were model dependent. For example, increased tumor cell apoptosis contributed towards combination efficacy in the A549 model, in association with increased expression of hsa-miR-29b and reduced expression of antiapoptotic genes including DNA methyltransferase DNMT3B, commonly up-regulated in patients with NSCLC. Such inverse effects of combination therapy on DNMT3B and hsa-miR-29b expression were found in multiple models. Importantly, in the A549 model, hsa-miR-29b down-regulation of DMNT3b reduced promoter methylation of tumor suppressor genes such as Cell adhesion molecule 1 (CADM1), Ras associated (RalGDS/AF-6) domain family member 1 (RASSF1), and Fragile histidine triad gene (FHIT), increasing their expression.

CONCLUSION

These results offer a preclinical rationale for combining an EGFR antibody with cisplatin/gemcitabine for patients with NSCLC, and provide potential molecular biomarkers for tailoring therapy.

Abstract 5030: Necitumumab (IMC-11F8), a recombinant human anti EGFR antibody, increases the antitumor effects of cisplatin/paclitaxel in human NSCLC xenograft models

Epidermal growth factor receptor (EGFR) targeted antibodies may have a role in the treatment of non-small cell lung cancer (NSCLC), based on preclinical and clinical data. Here we have demonstrated a significant benefit of adding necitumumab, a recombinant human IgG1 antibody targeting EGFR, to cisplatin+paclitaxel administered at its maximum tolerated dose, in subcutaneous xenograft tumor models established in nu/nu athymic mice with A549 or NCI-H1650 NSCLC cell lines.

Necitumumab monotherapy or cisplatin+paclitaxel therapy inhibited xenograft tumor growth with a T/C% of 47 and 63, respectively in A549 tumor model. A similar anti tumor effect was seen in NCI-H1650 xenograft tumors treated with necitumumab monotherapy or cisplatin+paclitaxel therapy with a T/C% of 37 and 50, respectively. Furthermore, the combination of necitumumab with cisplatin+paclitaxel significantly inhibited tumor growth with a magnitude greater than any of the therapies alone in A549 xenograft tumors with a T/C% of 33 and in NCI-H1650 xenograft tumors with a T/C% of 18. Combination treatment resulted in partial regressions (3 out of 9 mice) in A549 and maximum tumor regressions (10 out of 12) in NCI-H1650. Chi-Squared test for all animals in the treatment groups showed p=0.02 in A549 and p=3.0E-08 in NCI-H1650 xenograft tumors.

In vitro analysis on A549 and NCI-H1650 cell lines treated with cisplatin+paclitaxel, with/without necitumumab (5 μg/ml) demonstrated that this combination benefit was associated with the increased apoptotic index in both models. Cell cycle arrest during combination therapy was also observed as an increase in the percentage of cells in G2/M phase in A549 and S or G2/M phase in NCI-H1650 cell lines. We are further utilizing SABiosciences PCR arrays to demonstrate combination benefit related gene function in apoptosis, cell cycle signaling pathways and drug specific biomarkers in both A549 and NCI-H1650 cell lines.

Thus our results demonstrate the potential utility of necitumumab for enhancing the efficacy of cytotoxic chemotherapy in both in A549 and NCI-H1650 cell lines and xenograft tumors models.

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 5030. doi:10.1158/1538-7445.AM2011-5030

Abstract 1187: The role of PI3K as a biomarker

The phosphatidylinositol 3-kinase (PI3K) signaling pathway has been implicated in tumorigenesis. Evidence over the past years suggests a pivotal role for the catalytic subunit, PIK3CA, in human cancers. Receptor tyrosine kinases (RTKs) on the cell surface are key regulators of PI3K activity, and RTK antagonists have demonstrated significant anticancer effects in animal models and in patients. However, among tumor harboring activating mutations of PIK3CA, the therapeutic value of RTK antagonists may be compromised. The mutation status of PIK3CA may, therefore, serve as a potential biomarker for both prognosis and response to RTK inhibitors.

Somatic mutations of the pik3ca gene occur primarily in three hot spots, E542K, E545K (exon 9) and H1047R (exon 20). These mutations are detected in a broad spectrum of cancer indications including breast, colorectal and lung. This study was designed to explore the nature of PIK3CA mutations among numerous human cancer cell lines, utilizing mostly cells with the capacity to form tumors in mice. Primers corresponding to exon 9 and 20 of human pik3ca gene were designed. Genomic DNA was harvested from over 200 lines, derived from different human cancer indications. The pik3ca locus was sequenced and its WT or mutation status was determined.

Of these cells, 8% presented mutations equally distributed between exon 9 and 20. The frequency of PIK3CA mutations was particularly high among colon cancer lines, with fewer incidences among lung, breast and ovarian cancer lines. Interestingly, 50% of the PIK3CA mutated lines presented a concurrent mutation of either KRAS or BRAF. The capacity of PIK3CA mutation-bearing cell lines to respond to RTK blockers was then evaluated, and the mechanism contributing to such phenomenon was further discussed.

These results stress PI3K diagnosis value and its potential role as a valid biomarker for patient susceptibility.

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 1187.

Prioritization of EGFR/IGF-IR/VEGFR2 combination targeted therapies utilizing cancer models

BACKGROUND

Rational strategies utilizing anticancer efficacy and biological principles are needed for the prioritization of specific combination targeted therapy approaches for clinical development, from among the many with experimental support.

MATERIALS AND METHODS

Antibodies targeting epidermal growth factor receptor (EGFR) (cetuximab), insulin-like growth factor-1 receptor (IGF-IR) (IMC-A12) or vascular endothelial growth factor receptor 2 (VEGFR2) (DC101), were dosed alone or in combination, in 11 human tumor xenograft models established in mice. Efficacy readouts included the tumor burden and incidence of metastasis, as well as tumor active hypoxia inducible factor-1 (HIF-1), human VEGF and blood vessel density.

RESULTS

Cetuximab and DC101 contributed potent and non-overlapping benefits to the combination approach. Moreover, DC101 prevented escape from IMC-A12 + cetuximab in a colorectal cancer model and cetuximab prevented escape from DC101 therapy in a pancreatic cancer model.

CONCLUSION

Targeting VEGFR2 + EGFR was prioritized over other treatment strategies utilizing EGFR, IGF-IR and VEGFR2 antibodies. The criteria that proved to be valuable were a non-overlapping spectrum of anticancer activity and the prevention of resistance to another therapy in the combination.

Tumors established with cell lines selected for oxaliplatin resistance respond to oxaliplatin if combined with cetuximab

PURPOSE

To establish whether cetuximab, a chimeric IgG1 antibody targeting epidermal growth factor receptor, has the potential to restore responsiveness to oxaliplatin in preclinical cancer models, as has been shown with irinotecan in irinotecan refractory metastatic colorectal cancer patients.

EXPERIMENTAL DESIGN

The effects of cetuximab and oxaliplatin, alone or in combination, were tested in vitro and in vivo using human colorectal cancer cell lines selected for oxaliplatin resistance, as well as parental control cell lines. Evaluations were made of subcutaneous xenograft tumor growth in nu/nu athymic mice, as well as activation of mitogen-activated protein kinase (extracellular signal-regulated kinase 1/2) and AKT, expression of DNA repair genes, density of apurinic/apyrimidinic DNA damage, and accumulation of platinum-DNA adducts in vitro.

RESULTS

Oxaliplatin + cetuximab efficacy in murine subcutaneous xenograft models was greater than that of monotherapies and independent of the responsiveness to oxaliplatin monotherapy. In vitro, cetuximab reduced expression of excision repair cross-complementation group 1 and XPF, which are key components of the nucleotide excision repair pathway involved in the excision of platinum-DNA adducts. In addition, cetuximab reduced expression of XRCC1, a component of the base excision repair pathway responsible for the repair of apurinic/apyrimidinic sites. Effects of cetuximab on DNA repair protein levels were downstream to effects on mitogen-activated protein kinase and AKT pathway activation. In line with effects on DNA repair protein expression, cetuximab increased the accumulation of platinum and apurinic/apyrimidinic sites on DNA during oxaliplatin treatment.

CONCLUSIONS

Cetuximab has the potential to salvage the benefits of oxaliplatin in oxaliplatin-resistant colorectal cancer patients by reducing DNA repair capacity.

An antibody directed against PDGF receptor beta enhances the antitumor and the anti-angiogenic activities of an anti-VEGF receptor 2 antibody

Platelet-derived growth factor (PDGF) and its receptors (PDGFR) play important roles in tumorigenesis through stimulating tumor growth and promoting angiogenesis via enhancing pericyte recruitment and vessel maturation. Here we produced a neutralizing antibody, 1B3, directed against mouse PDGFRbeta. 1B3 binds to PDGFRbeta with high affinity (9x10(-11)M) and blocks PDGF-BB from binding to the receptor with an IC(50) of approximately 1.2 nM. The antibody also blocks ligand-stimulated activation of PDGFRbeta and downstream signaling molecules, including Akt and MAPK p42/44, in tumor cells. In animal studies, 1B3 significantly enhanced the antitumor and the anti-angiogenic activities of DC101, an antibody directed against mouse vascular endothelial growth factor receptor 2, in a pancreatic (BxPC-3) and a non-small cell lung (NCI-H460) tumor xenograft models. Treatment with the combination of 1B3 and DC101 in BxPC-3 xenograft-bearing mice resulted in tumor regression in 58% of mice compared to that in 18% of mice treated with DC101 alone. Taken together, these results lend great support to use PDGFRbeta antagonists in combinations with other antitumor and/or anti-angiogenic agents in the treatment of a variety of cancers.

Synergistic antitumor effects of combined epidermal growth factor receptor and vascular endothelial growth factor receptor-2 targeted therapy

PURPOSE

Combination therapies that target the epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) pathways, are being actively tested for the treatment of cancer. In evaluating combination strategies, the ideal combination would be one in which the treatments interact in a way that is synergistic with regard to antitumor effects. Here, we have evaluated the interaction between anti-EGFR antibody Erbitux (cetuximab) and anti-VEGFR2 antibody, DC101, in preclinical models of pancreatic (BxPC-3) and colon (GEO) cancer.

EXPERIMENTAL DESIGN

Analysis of the interaction between cetuximab and DC101 in vivo used a novel method for establishing the upper 95% confidence limits for the combination index (CI) of isobologram analyses, where CI < 1 indicates synergy. Assessment of tumor cell proliferation, apoptosis, VEGF production, and hypoxia, as well as tumor vascularization, was performed to gain insights into the mechanistic basis for synergy between agents targeting different tumor compartments.

RESULTS

Monotherapy ED(50) values for tumor growth inhibition ranged from 1.8 to 2.3 mg/kg and 10.5 to 16.6 mg/kg for cetuximab and DC101, respectively. From the dose response of the combination treatment, it was determined that cetuximab and DC101 are synergistic in the BxPC-3 (CI = 0.1, P < 0.01) and GEO (CI = 0.1, P < 0.01) models. Overlapping effects on the tumor cell and vascular compartments form a basis for the interaction, with VEGF production and hypoxia-inducible factor 1alpha potentially acting as molecular links between EGFR and VEGFR2 inhibition.

CONCLUSIONS

Results show antitumor synergy for combined EGFR and VEGFR2 targeted therapy, supporting the significant therapeutic potential of this combination strategy.

N-(4-{[4-(1H-Benzoimidazol-2-yl)-arylamino]-methyl}-phenyl)-benzamide derivatives as small molecule heparanase inhibitors

A novel class of N-(4-{[4-(1H-benzoimidazol-2-yl)-arylamino]-methyl}-phenyl)-benzamides are described as inhibitors of the endo-beta-glucuronidase heparanase. Among them are N-(4-{[4-(1H-benzoimidazol-2-yl)-phenylamino]-methyl}-phenyl)-3-bromo-4-methoxy-benzamide (15h), and N-(4-{[5-(1H-benzoimidazol-2-yl)-pyridin-2-ylamino]-methyl}- phenyl)-3-bromo-4-methoxy-benzamide (23) which displayed good heparanase inhibitory activity (IC(50) 0.23-0.29 microM), with the latter showing oral exposure in mice.

Targeting the platelet-derived growth factor receptor alpha with a neutralizing human monoclonal antibody inhibits the growth of tumor xenografts: implications as a potential therapeutic target

Platelet-derived growth factor receptor alpha (PDGFRalpha) is a type III receptor tyrosine kinase that is expressed on a variety of tumor types. A neutralizing monoclonal antibody to human PDGFRalpha, which did not cross-react with the beta form of the receptor, was generated. The fully human antibody, termed 3G3, has a Kd of 40 pmol/L and blocks both PDGF-AA and PDGF-BB ligands from binding to PDGFRalpha. In addition to blocking ligand-induced cell mitogenesis and receptor autophosphorylation, 3G3 inhibited phosphorylation of the downstream signaling molecules Akt and mitogen-activated protein kinase. This inhibition was seen in both transfected and tumor cell lines expressing PDGFRalpha. The in vivo antitumor activity of 3G3 was tested in human glioblastoma (U118) and leiomyosarcoma (SKLMS-1) xenograft tumor models in athymic nude mice. Antibody 3G3 significantly inhibited the growth of U118 (P=0.0004) and SKLMS-1 (P <0.0001) tumors relative to control. These data suggest that 3G3 may be useful for the treatment of tumors that express PDGFRalpha.

Biological investigation and structure-activity relationship studies on azadirone from Azadirachta indica A. Juss

Azadirone 1, a limonoidal constituent of Azadirachta indica is found to possess potent cytotoxic activity against a panel of human cancer cell lines in our in vitro studies. In vitro screening of a number of semi-synthetic analogues of 1 revealed that the alpha,beta-unsaturated enone moiety or its equivalent conjugated system in A-ring, C-7 acetyloxy/chloroacetyloxy or keto group in B-ring and the furan moiety are responsible for the activity of 1 and its analogues. Compound 1 and two of the semi-synthetic analogues 10 and 13 were found to possess good in vivo antitumor activity in modified hollow fiber animal models.

Andrographolide, a potential cancer therapeutic agent isolated from Andrographis paniculata

Andrographis paniculata plant extract is known to possess a variety of pharmacological activities. Andrographolide, the major constituent of the extract is implicated towards its pharmacological activity. We studied the cellular processes and targets modulated by andrographolide treatment in human cancer and immune cells. Andrographolide treatment inhibited the in vitro proliferation of different tumor cell lines, representing various types of cancers. The compound exerts direct anticancer activity on cancer cells by cell-cycle arrest at G0/G1 phase through induction of cell-cycle inhibitory protein p27 and decreased expression of cyclin-dependent kinase 4 (CDK4). Immunostimulatory activity of andrographolide is evidenced by increased proliferation of lymphocytes and production of interleukin-2. Andrographolide also enhanced the tumor necrosis factor-alpha production and CD marker expression, resulting in increased cytotoxic activity of lymphocytes against cancer cells, which may contribute for its indirect anticancer activity. The in vivo anticancer activity of the compound is further substantiated against B16F0 melanoma syngenic and HT-29 xenograft models. These results suggest that andrographolide is an interesting pharmacophore with anticancer and immunomodulatory activities and hence has the potential for being developed as a cancer therapeutic agent.

Novel 6,7-diphenyl-2,3,8,8a-tetrahydro-1H-indolizin-5-one analogues as cytotoxic agents

A series of 6,7-diphenyl-2,3,8,8a-tetrahydro-1H-indolizin-5-one analogues were synthesized and evaluated for cytotoxic activity against eight human cancer cell lines. Compounds 18, 21, 28, 29, 30 and 31 showed cytotoxic activity with GI(50) values in the range of 2.1-8.1 microM concentration. Among these, compounds 21 and 28 exhibited good pharmacokinetic properties. These compounds were further evaluated for their in vivo efficacy in modified hollow fibre assay (HFA).

Novel indolo[2,1-b]quinazoline analogues as cytostatic agents: synthesis, biological evaluation and structure-activity relationship

In our endeavor to design and synthesize novel anticancer agents, a new series of indoloquinazoline compounds were prepared and tested initially for anticancer activity in vitro against a panel of human cancer cell lines. Most of these compounds exhibited cytotoxic activity in in vitro screens. Compounds were selected and further evaluated using a modified Hollow Fiber Assay for their preliminary in vivo activity against 12 cell lines implanted in the subcutaneous and intraperitoneal compartments in mice. The results indicate that these compounds may constitute a new class of anticancer agents.

Novel C-ring analogues of 20(S)-camptothecin. Part 3: synthesis and their in vitro cytotoxicity of A-, B- and C-ring analogues

Several 5-substituted alkoxy 20(S)-camptothecin analogues having A- and B-ring substituents were prepared via semi-synthesis. Most of these compounds were found to exhibit potent anti-cancer activity based on their in vitro cytotoxicity data obtained against human tumor cell lines.

9-Deoxopodophyllotoxin derivatives as anti-cancer agents

Several 9-deoxo-9-substituted podophyllotoxin derivatives were synthesised starting from naturally occuring podophyllotoxin and their anti-cancer activity was evaluated against in vitro human cancer cell line assay. It was observed that these compounds do possess good anti-cancer activity particularly against ovarian, renal and lung cancer cell lines.

Novel D-ring analogues of podophyllotoxin as potent anti-cancer agents

Several D-ring modified analogues of podophyllotoxin were prepared viz semi-synthesis starting from naturally occurring podophyllotoxin and determined their in vitro anti-cancer activity. Most of the analogues have shown good activity towards human cancer cell lines.