A CD25-biased interleukin-2 for autoimmune therapy engineered via a semi-synthetic organism.

BACKGROUND: Natural cytokines are poorly suited as therapeutics for systemic administration due to suboptimal pharmacological and pharmacokinetic (PK) properties. Recombinant human interleukin-2 (rhIL-2) has shown promise for treatment of autoimmune (AI) disorders yet exhibits short systemic half-life and opposing immune responses that negate an appropriate therapeutic index. METHODS: A semi-synthetic microbial technology platform was used to engineer a site-specifically pegylated form of rhIL-2 with enhanced PK, specificity for induction of immune-suppressive regulatory CD4 + T cells (Tregs), and reduced stimulation of off-target effector T and NK cells. A library of rhIL-2 molecules was constructed with single site-specific, biorthogonal chemistry-compatible non-canonical amino acids installed near the interface where IL-2 engages its cognate receptor ßγ (IL-2Rßγ) signaling complex. Biorthogonal site-specific pegylation and functional screening identified variants that retained engagement of the IL-2Rα chain with attenuated potency at the IL-2Rßγ complex. RESULTS: Phenotypic screening in mouse identifies SAR444336 (SAR'336; formerly known as THOR-809), rhIL-2 pegylated at H16, as a potential development candidate that specifically expands peripheral CD4+ Tregs with upregulation of markers that correlate with their suppressive function including FoxP3, ICOS and Helios, yet minimally expands CD8 + T or NK cells. In non-human primate, administration of SAR'336 also induces dose-dependent expansion of Tregs and upregulated suppressive markers without significant expansion of CD8 + T or NK cells. SAR'336 administration reduces inflammation in a delayed-type hypersensitivity mouse model, potently suppressing CD4+ and CD8 + T cell proliferation. CONCLUSION: SAR'336 is a specific Treg activator, supporting its further development for the treatment of AI diseases.

Interleukin-2 (IL-2) is a protein that functions as a master regulator of immune responses. A key function of IL-2 is the stimulation of immune-regulatory cells that suppress autoimmune disease, which occurs when the body's immune system mistakenly attacks healthy tissues. However, therapeutic use of IL-2 is limited by its short duration of action and incomplete selectivity for immune-suppressive cells over off-target immune-stimulatory cells. We employ a platform that we have previously developed, which is a bacterial organism with an expanded DNA code, to identify a new version of IL-2, SAR444336 (SAR'336), with an extended duration of activity and increased selectivity for immune-suppressive cells. In mice and monkeys, SAR'336 was a specific activator of immune suppression, with minimal effect on immune cells that stimulate autoimmunity. Our results support further development of SAR'336 for treatment of autoimmune disorders.

An engineered IL-2 reprogrammed for anti-tumor therapy using a semi-synthetic organism.

The implementation of applied engineering principles to create synthetic biological systems promises to revolutionize medicine, but application of fundamentally redesigned organisms has thus far not impacted practical drug development. Here we utilize an engineered microbial organism with a six-letter semi-synthetic DNA code to generate a library of site-specific, click chemistry compatible amino acid substitutions in the human cytokine IL-2. Targeted covalent modification of IL-2 variants with PEG polymers and screening identifies compounds with distinct IL-2 receptor specificities and improved pharmacological properties. One variant, termed THOR-707, selectively engages the IL-2 receptor beta/gamma complex without engagement of the IL-2 receptor alpha. In mice, administration of THOR-707 results in large-scale activation and amplification of CD8+ T cells and NK cells, without Treg expansion characteristic of IL-2. In syngeneic B16-F10 tumor-bearing mice, THOR-707 enhances drug accumulation in the tumor tissue, stimulates tumor-infiltrating CD8+ T and NK cells, and leads to a dose-dependent reduction of tumor growth. These results support further characterization of the immune modulatory, anti-tumor properties of THOR-707 and represent a fundamental advance in the application of synthetic biology to medicine, leveraging engineered semi-synthetic organisms as cellular factories to facilitate discovery and production of differentiated classes of chemically modified biologics.

Peginterferon Beta-1a Shows Antitumor Activity as a Single Agent and Enhances Efficacy of Standard of Care Cancer Therapeutics in Human Melanoma, Breast, Renal, and Colon Xenograft Models.

Because of its tumor-suppressive effect, interferon-based therapy has been used for the treatment of melanoma. However, limited data are available regarding the antitumor effects of pegylated interferons, either alone or in combination with approved anticancer drugs. We report that treatment of human WM-266-4 melanoma cells with peginterferon beta-1a induced apoptotic markers. Additionally, peginterferon beta-1a significantly inhibited the growth of human SK-MEL-1, A-375, and WM-266-4 melanoma xenografts established in immunocompromised mice. Peginterferon beta-1a regressed large, established WM-266-4 xenografts in nude mice. Treatment of SK-MEL-1 tumor-bearing mice with a combination of peginterferon beta-1a and the MEK inhibitor PD325901 ((R)-N-(2,3-dihydroxypropoxy)-3,4-difluoro-2-(2-fluoro-4-iodophenylamino)benzamide) significantly improved tumor growth inhibition compared with either agent alone. Examination of the antitumor activity of peginterferon beta-1a in combination with approved anticancer drugs in breast and renal carcinomas revealed improved antitumor activity in these preclinical xenograft models, as did the combination of peginterferon beta-1a and bevacizumab in a colon carcinoma xenograft model.

The Discovery and Preclinical Development of ASG-5ME, an Antibody-Drug Conjugate Targeting SLC44A4-Positive Epithelial Tumors Including Pancreatic and Prostate Cancer.

Here, we report the development of an antibody-drug conjugate, ASG-5ME, which targets the solute carrier receptor SLC44A4. SLC44A4 is a member of a family of putative choline transporters that we show to be markedly upregulated in a variety of epithelial tumors, most notably prostate and pancreatic cancer. SLC44A4 is normally expressed on the apical surface of secretory epithelial cells, but in cancer we show expression is not restricted to the luminal surface in advanced and undifferentiated tumors. ASG-5ME consists of a human IgG2 anti-SLC44A4 antibody conjugated through a cleavable linker to the microtubule-disrupting agent monomethylauristatin E. It has potent antitumor activity in both cell line - and patient-derived xenograft models of pancreatic and prostate cancers. Combination studies with ASG-5ME and nab-paclitaxel demonstrated combination effect in both pancreatic and prostate tumor models. Altogether, the data presented here suggest that ASG-5ME may have the potential to offer a new therapeutic option for the treatment of pancreatic and prostate cancers. Mol Cancer Ther; 15(11); 2679-87. ©2016 AACR.

Preclinical Evaluation of an Anti-Nectin-4 ImmunoPET Reagent in Tumor-Bearing Mice and Biodistribution Studies in Cynomolgus Monkeys.

PURPOSE: Nectin-4 is selectively overexpressed in a variety of cancers and is currently under clinical investigation as a therapeutic target. A monoclonal antibody against nectin-4 (AGS-22M6) was evaluated as an Immuno-positron emission tomography (ImmunoPET) reagent. Its ability to assay nectin-4 expression as well as detect nectin-4 positive tumors in the liver and bone was evaluated using mouse models. PROCEDURES: The biodistribution of [(89)Zr]AGS-22M6 was evaluated in mice bearing tumors with varying levels of nectin-4 expression. An isogenic breast cancer tumor line was used to model metastatic liver and bone disease in mice. The biodistribution of [(18)F]AGS-22M6 in cynomolgus monkeys was evaluated. RESULTS: A positive correlation was demonstrated between tumor nectin-4 expression and [(89)Zr]AGS-22M6 uptake. Tumors in the liver and bone were detected and differentiated based on nectin-4 expression. [(18)F]AGS-22M6 showed limited uptake in cynomolgus monkey tissues. CONCLUSIONS: [(89)Zr]AGS-22M6 is a promising ImmunoPET reagent that can assay nectin-4 expression in both primary and metastatic lesions.

Enfortumab Vedotin Antibody-Drug Conjugate Targeting Nectin-4 Is a Highly Potent Therapeutic Agent in Multiple Preclinical Cancer Models.

The identification of optimal target antigens on tumor cells is central to the advancement of new antibody-based cancer therapies. We performed suppression subtractive hybridization and identified nectin-4 (PVRL4), a type I transmembrane protein and member of a family of related immunoglobulin-like adhesion molecules, as a potential target in epithelial cancers. We conducted immunohistochemical analysis of 2,394 patient specimens from bladder, breast, lung, pancreatic, ovarian, head/neck, and esophageal tumors and found that 69% of all specimens stained positive for nectin-4. Moderate to strong staining was especially observed in 60% of bladder and 53% of breast tumor specimens, whereas the expression of nectin-4 in normal tissue was more limited. We generated a novel antibody-drug conjugate (ADC) enfortumab vedotin comprising the human anti-nectin-4 antibody conjugated to the highly potent microtubule-disrupting agent MMAE. Hybridoma (AGS-22M6E) and CHO (ASG-22CE) versions of enfortumab vedotin (also known as ASG-22ME) ADC were able to bind to cell surface-expressed nectin-4 with high affinity and induced cell death in vitro in a dose-dependent manner. Treatment of mouse xenograft models of human breast, bladder, pancreatic, and lung cancers with enfortumab vedotin significantly inhibited the growth of all four tumor types and resulted in tumor regression of breast and bladder xenografts. Overall, these findings validate nectin-4 as an attractive therapeutic target in multiple solid tumors and support further clinical development, investigation, and application of nectin-4-targeting ADCs. Cancer Res; 76(10); 3003-13. ©2016 AACR.

Development of ASG-15ME, a Novel Antibody-Drug Conjugate Targeting SLITRK6, a New Urothelial Cancer Biomarker.

SLITRK6 is a member of the SLITRK family of neuronal transmembrane proteins that was discovered as a bladder tumor antigen using suppressive subtractive hybridization. Extensive immunohistochemistry showed SLITRK6 to be expressed in multiple epithelial tumors, including bladder, lung, and breast cancer as well as in glioblastoma. To explore the possibility of using SLITRK6 as a target for an antibody-drug conjugate (ADC), we generated a panel of fully human mAbs specific for SLITRK6. ADCs showed potent in vitro and in vivo cytotoxic activity after conjugation to Monomethyl Auristatin E or Monomethyl Auristatin F. The most potent ADC, ASG-15ME, was selected as the development candidate and given the product name AGS15E. ASG-15ME is currently in phase I clinical trials for the treatment of metastatic urothelial cancer. This is the first report that SLITRK6 is a novel antigen in bladder cancer and also the first report of the development of ASG-15ME for the treatment of metastatic bladder cancer. Mol Cancer Ther; 15(6); 1301-10. ©2016 AACR.

AGS16F Is a Novel Antibody Drug Conjugate Directed against ENPP3 for the Treatment of Renal Cell Carcinoma.

PURPOSE: New cancer-specific antigens are required for the design of novel antibody-drug conjugates (ADC) that deliver tumor-specific and highly potent cytotoxic therapy. EXPERIMENTAL DESIGN: Suppression subtractive hybridization identified ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3 or CD203c) as a potential human cancer-specific antigen. Antibodies targeting the extracellular domain of human ENPP3 were produced and selected for specific binding to ENPP3. Expression of ENPP3 in normal and cancer tissue specimens was evaluated by immunohistochemistry (IHC). ADCs comprising anti-ENPP3 Ab conjugated with maleimidocaproyl monomethyl auristatin F via a noncleavable linker (mcMMAF) were selected for therapeutic potential using binding and internalization assays, cytotoxicity assays, and tumor growth inhibition in mouse xenograft models. Pharmacodynamic markers were evaluated by IHC in tissues and ELISA in blood. RESULTS: ENPP3 was highly expressed in clear cell renal cell carcinoma: 92.3% of samples were positive and 83.9% showed high expression. By contrast, expression was negligible in normal tissues examined, with the exception of the kidney. High expression was less frequent in papillary renal cell carcinoma and hepatocellular carcinoma samples. AGS16F, an anti-ENPP3 antibody-mcMMAF conjugate, inhibited tumor growth in three different renal cell carcinoma (RCC) xenograft models. AGS16F localized to tumors, formed the active metabolite Cys-mcMMAF, induced cell-cycle arrest and apoptosis, and increased blood levels of caspase-cleaved cytokeratin-18, a marker of epithelial cell death. CONCLUSIONS: AGS16F is a promising new therapeutic option for patients with RCC and is currently being evaluated in a phase I clinical trial.

AGS67E, an Anti-CD37 Monomethyl Auristatin E Antibody-Drug Conjugate as a Potential Therapeutic for B/T-Cell Malignancies and AML: A New Role for CD37 in AML.

CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody-drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent monomethyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34(+)CD38(-) leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML.

In vitro and in vivo evaluation of cysteine and site specific conjugated herceptin antibody-drug conjugates.

Antibody drug conjugates (ADCs) are monoclonal antibodies designed to deliver a cytotoxic drug selectively to antigen expressing cells. Several components of an ADC including the selection of the antibody, the linker, the cytotoxic drug payload and the site of attachment used to attach the drug to the antibody are critical to the activity and development of the ADC. The cytotoxic drugs or payloads used to make ADCs are typically conjugated to the antibody through cysteine or lysine residues. This results in ADCs that have a heterogeneous number of drugs per antibody. The number of drugs per antibody commonly referred to as the drug to antibody ratio (DAR), can vary between 0 and 8 drugs for a IgG1 antibody. Antibodies with 0 drugs are ineffective and compete with the ADC for binding to the antigen expressing cells. Antibodies with 8 drugs per antibody have reduced in vivo stability, which may contribute to non target related toxicities. In these studies we incorporated a non-natural amino acid, para acetyl phenylalanine, at two unique sites within an antibody against Her2/neu. We covalently attached a cytotoxic drug to these sites to form an ADC which contains two drugs per antibody. We report the results from the first direct preclinical comparison of a site specific non-natural amino acid anti-Her2 ADC and a cysteine conjugated anti-Her2 ADC. We report that the site specific non-natural amino acid anti-Her2 ADCs have superior in vitro serum stability and preclinical toxicology profile in rats as compared to the cysteine conjugated anti-Her2 ADCs. We also demonstrate that the site specific non-natural amino acid anti-Her2 ADCs maintain their in vitro potency and in vivo efficacy against Her2 expressing human tumor cell lines. Our data suggests that site specific non-natural amino acid ADCs may have a superior therapeutic window than cysteine conjugated ADCs.

Molecular characterization of patient-derived human pancreatic tumor xenograft models for preclinical and translational development of cancer therapeutics.

Preclinical evaluation of novel cancer agents requires models that accurately reflect the biology and molecular characteristics of human tumors. Molecular profiles of eight pancreatic ductal adenocarcinoma patient tumors were compared to corresponding passages of xenografts obtained by grafting tumor fragments into immunocompromised mice. Molecular characterization was performed by copy number analysis, gene expression and microRNA microarrays, mutation analysis, short tandem repeat (STR) profiling, and immunohistochemistry. Xenografts were found to be highly representative of their respective tumors, with a high degree of genetic stability observed by STR profiling and mutation analysis. Copy number variation (CNV) profiles of early and late xenograft passages were similar, with recurrent losses on chromosomes 1p, 3p, 4q, 6, 8p, 9, 10, 11q, 12p, 15q, 17, 18, 20p, and 21 and gains on 1q, 5p, 8q, 11q, 12q, 13q, 19q, and 20q. Pearson correlations of gene expression profiles of tumors and xenograft passages were above 0.88 for all models. Gene expression patterns between early and late passage xenografts were highly stable for each individual model. Changes observed in xenograft passages largely corresponded to human stromal compartment genes and inflammatory processes. While some differences exist between the primary tumors and corresponding xenografts, the molecular profiles remain stable after extensive passaging. Evidence for stability in molecular characteristics after several rounds of passaging lends confidence to clinical relevance and allows for expansion of models to generate the requisite number of animals required for cohorts used in drug screening and development studies.

The anti-Fn14 antibody BIIB036 inhibits tumor growth in xenografts and patient derived primary tumor models and enhances efficacy of chemotherapeutic agents in multiple xenograft models.

Agonistic antibodies targeting Fn14, the receptor for TWEAK, have demonstrated anti-tumor activity in xenograft models. Herein, we further explore the therapeutic potential of the humanized anti-Fn14 agonistic antibody, BIIB036, as a single agent and in combination with standard of care cancer therapeutics. Pharmacokinetic studies of BIIB036 in tumor-bearing mice revealed a half-life of approximately three days suggesting twice a week dosing would be necessary to maintain efficacy. However, in multiple xenograft models, BIIB036 treatment resulted in extended tumor growth inhibition up to 40-50 d following cessation of dosing, suggesting that frequent administration of BIIB036 may not be necessary to maintain prolonged anti-tumor activity. Subsequent xenograft studies revealed that maximal efficacy was achieved with BIIB036 dosing once every two weeks, by either intraperitoneal or subcutaneous administration. Xenograft tumors that were initially treated with BIBI036 and then re-grew up to 1000 mm³ following cessation of the first cycle of treatment remained sensitive to a second cycle of treatment. BIIB036 was also evaluated in patient derived primary colon tumor models, where efficacy compared favorably with a standard of care agent. Lastly, BIIB036 enhanced the efficacy of several standard of care chemotherapeutics, including paclitaxel in MDA-MBA-231 breast tumor xenografts, paclitaxel or carboplatin in HOP62 non-small cell lung xenografts, and 5-FU in NCI-N87 gastric xenografts, with no overlapping toxicities. These studies thus establish BIIB036 as a promising therapeutic agent with durable anti-tumor activity in human xenografts as well as patient derived primary tumor models, and enhanced activity and tolerability in combination with standard of care chemotherapeutics. Taken together, the data presented herein suggest that BIIB036 warrants evaluation in the clinic.

Development of an Fn14 agonistic antibody as an anti-tumor agent.

TWEAK, a TNF family ligand with pleiotropic cellular functions, was originally described as capable of inducing tumor cell death in vitro. TWEAK functions by binding its receptor, Fn14, which is up-regulated on many human solid tumors. Herein, we show that intratumoral administration of TWEAK, delivered either by an adenoviral vector or in an immunoglobulin Fc-fusion form, results in significant inhibition of tumor growth in a breast xenograft model. To exploit the TWEAK-Fn14 pathway as a therapeutic target in oncology, we developed an anti-Fn14 agonistic antibody, BIIB036. Studies described herein show that BIIB036 binds specifically to Fn14 but not other members of the TNF receptor family, induces Fn14 signaling, and promotes tumor cell apoptosis in vitro. In vivo, BIIB036 effectively inhibits growth of tumors in multiple xenograft models, including colon (WiDr), breast (MDA-MB-231), and gastric (NCI-N87) tumors, regardless of tumor cell growth inhibition response observed to BIIB036 in vitro. The anti-tumor activity in these cell lines is not TNF-dependent. Increasing the antigen-binding valency of BIB036 significantly enhances its anti-tumor effect, suggesting the contribution of higher order cross-linking of the Fn14 receptor. Full Fc effector function is required for maximal activity of BIIB036 in vivo, likely due to the cross-linking effect and/or ADCC mediated tumor killing activity. Taken together, the anti-tumor properties of BIIB036 validate Fn14 as a promising target in oncology and demonstrate its potential therapeutic utility in multiple solid tumor indications.

Discovery of a potent and highly selective PDK1 inhibitor via fragment-based drug discovery.

We report the use of a fragment-based lead discovery method, Tethering with extenders, to discover a pyridinone fragment that binds in an adaptive site of the protein PDK1. With subsequent medicinal chemistry, this led to the discovery of a potent and highly selective inhibitor of PDK1, which binds in the 'DFG-out' conformation.

A stable IgG-like bispecific antibody targeting the epidermal growth factor receptor and the type I insulin-like growth factor receptor demonstrates superior anti-tumor activity.

The epidermal growth factor receptor (EGFR) and the type I insulin-like growth factor receptor (IGF-1R) are two cell surface receptor tyrosine kinases known to cooperate to promote tumor progression and drug resistance. Combined blockade of EGFR and IGF-1R has shown improved anti-tumor activity in preclinical models. Here, we report the characterization of a stable IgG-like bispecific antibody (BsAb) dual-targeting EGFR and IGF-1R that was developed for cancer therapy. The BsAb molecule (EI-04), constructed with a stability-engineered single chain variable fragment (scFv) against IGF-1R attached to the carboxyl-terminus of an IgG against EGFR, displays favorable biophysical properties for biopharmaceutical development. Biochemically, EI-04 bound to human EGFR and IGF-1R with sub nanomolar affinity, co-engaged the two receptors simultaneously, and blocked the binding of their respective ligands with similar potency compared to the parental monoclonal antibodies (mAbs). In tumor cells, EI-04 effectively inhibited EGFR and IGF-1R phosphorylation, and concurrently blocked downstream AKT and ERK activation, resulting in greater inhibition of tumor cell growth and cell cycle progression than the single mAbs. EI-04, likely due to its tetravalent bispecific format, exhibited high avidity binding to BxPC3 tumor cells co-expressing EGFR and IGF-1R, and consequently improved potency at inhibiting IGF-driven cell growth over the mAb combination. Importantly, EI-04 demonstrated enhanced in vivo anti-tumor efficacy over the parental mAbs in two xenograft models, and even over the mAb combination in the BxPC3 model. Our data support the clinical investigation of EI-04 as a superior cancer therapeutic in treating EGFR and IGF-1R pathway responsive tumors.

Stable IgG-like bispecific antibodies directed toward the type I insulin-like growth factor receptor demonstrate enhanced ligand blockade and anti-tumor activity.

Bispecific antibodies (BsAbs) target multiple epitopes on the same molecular target or different targets. Although interest in BsAbs has persisted for decades, production of stable and active BsAbs has hindered their clinical evaluation. Here, we describe the production and characterization of tetravalent IgG-like BsAbs that combine the activities of allosteric and competitive inhibitors of the type-I insulin-like growth factor receptor (IGF-1R). The BsAbs, which were engineered for thermal stability, express well, demonstrate favorable biophysical properties, and recognize both epitopes on IGF-1R. Only one BsAb with a unique geometry, denoted BIIB4-5scFv, was capable of engaging all four of its binding arms simultaneously. All the BsAbs (especially BIIB4-5scFv) demonstrated enhanced ligand blocking over the single monoclonal antibodies (mAbs), particularly at high ligand concentrations. The pharmacokinetic profiles of two IgG-like BsAbs were tested in nude mice and shown to be comparable with that of the parental mAbs. The BsAbs, especially BIIB4-5scFv, demonstrated an improved ability to reduce the growth of multiple tumor cell lines and to inhibit ligand-induced IGF-1R signaling in tumor cells over the parental mAbs. BIIB4-5scFv also led to superior tumor growth inhibition over its parental mAbs in vivo. In summary, BsAbs that bridge multiple inhibitory mechanisms against a single target may generally represent a more effective strategy for intervention in oncology or other indications compared with traditional mAb therapy.

Combination of two insulin-like growth factor-I receptor inhibitory antibodies targeting distinct epitopes leads to an enhanced antitumor response.

The insulin-like growth factor-I receptor (IGF-IR) is a cell surface receptor tyrosine kinase that mediates cell survival signaling and supports tumor progression in multiple tumor types. We identified a spectrum of inhibitory IGF-IR antibodies with diverse binding epitopes and ligand-blocking properties. By binding distinct inhibitory epitopes, two of these antibodies, BIIB4 and BIIB5, block both IGF-I and IGF-II binding to IGF-IR using competitive and allosteric mechanisms, respectively. Here, we explored the inhibitory effects of combining BIIB4 and BIIB5. In biochemical assays, the combination of BIIB4 and BIIB5 improved both the potency and extent of IGF-I and IGF-II blockade compared with either antibody alone. In tumor cells, the combination of BIIB4 and BIIB5 accelerated IGF-IR downregulation and more efficiently inhibited IGF-IR activation as well as downstream signaling, particularly AKT phosphorylation. In several carcinoma cell lines, the antibody combination more effectively inhibited ligand-driven cell growth than either BIIB4 or BIIB5 alone. Notably, the enhanced tumor growth-inhibitory activity of the BIIB4 and BIIB5 combination was much more pronounced at high ligand concentrations, where the individual antibodies exhibited substantially reduced activity. Compared with single antibodies, the BIIB4 and BIIB5 combination also significantly further enhanced the antitumor activity of the epidermal growth factor receptor inhibitor erlotinib and the mTOR inhibitor rapamycin. Moreover, in osteosarcoma and hepatocellular carcinoma xenograft models, the BIIB4 and BIIB5 combination significantly reduced tumor growth to a greater degree than each single antibody. Taken together, our results suggest that targeting multiple distinct inhibitory epitopes on IGF-IR may be a more effective strategy of affecting the IGF-IR pathway in cancer.

Anti-tumor activity of stability-engineered IgG-like bispecific antibodies targeting TRAIL-R2 and LTbetaR.

Bispecific antibodies (BsAbs) represent an emerging class of biologics that achieve dual targeting with a single agent. Recombinant DNA technologies have facilitated a variety of creative bispecific designs with many promising therapeutic applications; however, practical methods for producing high quality BsAbs that have good product stability, long serum half-life, straightforward purification, and scalable production have largely been limiting. Here we describe a protein-engineering approach for producing stable, scalable tetravalent IgG-like BsAbs. The stability-engineered IgG-like BsAb was envisioned to target and crosslink two TNF family member receptors, TRAIL-R2 (TNF-Related Apoptosis Inducing Ligand Receptor-2) and LTbetaR (Lymphotoxin-beta Receptor), expressed on the surface of epithelial tumor cells with the goal of triggering an enhanced anti-tumor effect. Our IgG-like BsAbs consists of a stability-engineered anti-LTbetaR single chain Fv (scFv) genetically fused to either the N- or C-terminus of the heavy chain of a fulllength anti-TRAIL-R2 IgG1 monoclonal antibody. Both N- or C-terminal BsAbs were active in inhibiting tumor cell growth in vitro, and with some cell lines demonstrated enhanced activity relative to the combination of parental Abs. Pharmacokinetic studies in mice revealed long serum half-lives for the BsAbs. In murine tumor xenograft models, therapeutic treatment with the BsAbs resulted in reduction in tumor volume either comparable to or greater than the combination of parental antibodies, indicating that simultaneously targeting and cross-linking receptor pairs is an effective strategy for treating tumor cells. These studies support that stability-engineering is an enabling step for producing scalable IgG-like BsAbs with properties desirable for biopharmaceutical development.

Chemosensitization and radiosensitization of human lung and colon cancers by antimitotic agent, ABT-751, in athymic murine xenograft models of subcutaneous tumor growth.

PURPOSE: ABT-751 is an orally active antimitotic agent that is currently in Phase II clinical trials. This agent binds to the colchicine site on ss-tubulin and inhibits polymerization of microtubules. This disruption of microtubule dynamics leads to a block in the cell cycle at the G2/M phase, and promotes apoptosis. ABT-751, as a single agent, has antitumor activity against a series of xenograft models including non-small cell lung cancer (NSCLC) and colon cancer. The current studies were conducted to determine whether ABT-751 enhances antitumor activity of standard cytotoxic therapies currently in clinical use. METHODS: Efficacy of ABT-751, in combination with cisplatin, 5-FU, and radiation, was evaluated in the Calu-6 NSCLC, HT-29 colon, and HCT-116 colon carcinoma xenograft models, respectively. Tumor-bearing athymic mice were treated with ABT-751 orally once a day at 75 or 100 mg/kg/day on a 5-days-on, 5-days-off schedule for two cycles. RESULTS: Efficacy of ABT-751 at 100 mg/kg/day was tested in combination with cisplatin at its maximum tolerable dose (MTD) (10 mg/kg/day, i.p. x1) in Calu-6 tumor-bearing athymic mice. The percent treated/control (%T/C) tumor volume ratios on day 38 were 35, 37, and 6, and the percent tumor growth delay (%TGD) values were 71, 65, and 188 for cisplatin, ABT-751 and the combination groups, respectively. HT-29 colon tumors were used to test ABT-751 in combination with an MTD of 5-FU, 30 mg/kg/day, i.p., q.d. x5. The %T/C ratios on day 38 were 22, 28, and 5 and the %TGD values were 75, 75, and 150 for 5-FU, ABT-751, and the combination groups, respectively. Treatment of HCT-116 colon carcinoma tumors with ABT-751, concurrent with the radiation treatment, was able to both enhance radiation-induced tumor regression, and delay the time to recurrence and progression. Growth curves allowed calculation of enhancement of radiation-induced growth delay (defined as the additional time required for a treated tumor to reach four times its original size) of 2, 9, and 12 days, for ABT-751 alone, radiation alone, and the combination, respectively. CONCLUSION: Collectively, these studies demonstrate that ABT-751 enhanced efficacy of standard cytotoxic therapies in a variety of tumor xenograft models, and that enhancement was at least additive in all systems.

A highly potent and selective farnesyltransferase inhibitor ABT-100 in preclinical studies.

Ras mutation has been detected in approximately 20-30% of all human carcinomas, primarily in pancreatic, colorectal, lung and bladder carcinomas. The indirect inhibition of Ras activity by inhibiting farnesyltransferase (FTase) function is one therapeutic intervention to control tumor growth. Here we report the preclinical anti-tumor activity of our most advanced FTase inhibitor (FTI), ABT-100, and a direct comparison with the current clinical candidates. ABT-100 is a highly selective, potent and orally bioavailable FTI. It broadly inhibits the growth of solid tumors in preclinical animal models. Thus, ABT-100 is an attractive candidate for further clinical evaluation. In addition, our results provide plausible insights to explain the impressive potency and selectivity of ABT-100. Finally, we have demonstrated that ABT-100 significantly suppresses the expression of vascular endothelial growth factor (VEGF) mRNA and secretion of VEGF protein, as well as inhibiting angiogenesis in the animal model.