Monoclonal antibody therapy

Controlled release of an anthrax toxin-neutralizing antibody from hydrolytically degradable polyethylene glycol hydrogels

In this study, hydrophilic and hydrolytically degradable poly (ethylene glycol) (PEG) hydrogels were formed via Michael-type addition and employed for sustained delivery of a monoclonal antibody against the protective antigen of anthrax. Taking advantage of the PEG-induced precipitation of the antibody, burst release from the matrix was avoided. These hydrogels were able to release active antibodies in a controlled manner from 14 days to as long as 56 days in vitro by varying the polymer architectures and molecular weights of the precursors. Analysis of the secondary and tertiary structure and the in vitro activity of the released antibody showed that the encapsulation and release did not affect the protein conformation or functionality. The results suggest the promise for developing PEG-based carriers for sustained release of therapeutic antibodies against toxins in various applications.

Targeting the type 1 insulin-like growth factor receptor as a treatment for cancer

BACKGROUND

The type 1 insulin-like growth factor receptor (IGF1R) plays a critical role in transformation, invasion and apoptosis protection, and is an attractive cancer treatment target.

OBJECTIVE

To review IGF1R antibodies and kinase inhibitors that are in preclinical and clinical development, and to discuss questions that will influence the success of this approach in clinical practice.

METHODS

This review is drawn from published literature, meeting abstracts and online resources.

RESULTS/CONCLUSION

IGF1R blockade is generally well tolerated although it can induce hyperglycaemia. Single-agent activity has been documented in Ewing's sarcoma but not thus far in common solid tumours. Key issues include identification of factors that influence sensitivity to IGF1R blockade, and how most effectively to combine IGF1R inhibitors with other treatments.

Insulin-Like Growth Factor (IGF) family and prostate cancer

There is abundant in vitro, animal and epidemiologic evidence to suggest that the Insulin-Like Growth Factor (IGF) family is a multi-component network of molecules which is involved in the regulation of both physiological and pathological growth processes in prostate. The IGF family plays a key role in cellular metabolism, differentiation, proliferation, transformation and apoptosis, during normal development and malignant growth. This family also seem essential in prostate cancer bone metastases, angiogenesis and androgen-independent progression. Therapeutic alternatives in men with progressive prostate cancer after androgen ablation are very limited. More effective therapies are needed for these patients. Pharmacologic interventions targeting the IGF family are being devised. Such strategies include reduction of IGF-I levels (growth hormone-releasing hormone antagonists, somatostatin analogs), reduction of functional IGF-I receptor levels (antisense oligonucleotides, small interfering RNA), inhibition of IGF-IR and its signalling (monoclonal antibodies, small-molecule tyrosine kinase inhibitors) and Insulin-Like Growth Factor Binding Proteins.

Future directions of liposome- and immunoliposome-based cancer therapeutics

Nanoscale drug delivery systems including liposomes, polymers, and other nanoparticles provide potential solutions for improved cancer therapeutics. Of these drug delivery systems, liposome-based agents, particularly liposomal anthracyclines, have had the greatest impact in oncology to date. Current liposomal drugs evolved from a number of design strategies for improved biodistribution over free drugs. Reticuloendothelial system-targeted formulations significantly reduce systemic exposure to high peak levels of free drug, but do not facilitate targeting to tumors. Passive or physiologic targeting of drugs to tumors is achievable using long-circulating liposomes, including pure lipid systems as well as surface-modified formulations designed to resist recognition and uptake by reticuloendothelial system cells. The latter, represented by pegylated or STEALTH liposomes, circulate for days as stable constructs and slowly extravasate in neoangiogenic vessels in tumors, providing a degree of passive targeting to tumor tissue. Future liposome therapeutics are building on these validated designs as well as on pharmacologic insights into their mechanisms of delivery. For example, camptothecin analogues, anti-angiogenesis agents, and antisense oligonucleotides each represent rational candidates for delivery in highly stabilized and long-circulating liposomes. For such agents, pegylated liposome delivery offers improved chemical stability of encapsulated drug, enhanced accumulation in tumors, and prolonged drug exposure. True molecular targeting can be achieved using liposomes linked to ligands such as monoclonal antibody fragments directed against cancer-associated antigens. Immunoliposomes combine antibody-mediated tumor recognition with liposomal delivery and, when designed for target cell internalization, provide intracellular drug release. Recent advances in immunoliposome design include rapid selection of phage antibody-derived scFv for targeting, and methods for conjugation of ligands to existing US Food and Drug Administration-approved liposomal drugs such as pegylated liposomal doxorubicin (Doxil/Caelxy [PLD]). An immunoliposome consisting of novel anti-HER2 scFv F5 conjugated to PLD, currently in development, selectively binds to and internalizes in HER2-overexpressing tumor cells. The modular organization of immunoliposome technology enables a combinatorial approach in which a repertoire of monoclonal antibody fragments can be used in conjunction with a series of liposomal drugs to yield a new generation of molecularly targeted agents.

RNA and DNA aptamers in cytomics analysis

BACKGROUND

The systematic evolution of ligands by exponential enrichment (SELEX) technique is a combinatorial library approach in which DNA or RNA molecules (aptamers) are selected by their ability to bind their protein targets with high affinity and specificity, comparable to that of monoclonal antibodies. In contrast to antibodies conventionally selected in animals, aptamers are generated by an in vitro selection process, and can be directed against almost every target, including antigens like toxins or nonimmunogenic targets, against which conventional antibodies cannot be raised.

METHODS

Aptamers are ideal candidates for cytomics, as they can be attached to fluorescent reporters or nanoparticles in order to study biological function by fluorescence microscopy, by flow cytometry, or to quantify the concentration of their target in biological fluids or cells using ELISA, RIA, and Western blot assays.

RESULTS

We demonstrate the in vitro selection of anti-kinin B1 receptor aptamers that could be used to determine B1 receptor expression during inflammation processes. These aptamers specifically recognize their target in a Northern-Western blot assay, and bind to their target protein whenever they are exposed in the membrane.

CONCLUSIONS

Currently, aptamers are linked to fluorescent reporters. We discuss here the present status and future directions concerning the use of the SELEX technique in cytomics.

Integrin alpha(v)beta3 targeted therapy for Kaposi's sarcoma with an in vitro evolved antibody

Here, we define integrin alpha(v)beta3 as a molecular target for antibody therapy for Kaposi's sarcoma (KS). We previously reported, using a new phage display strategy based on designed combinatorial V gene libraries, the humanization of mouse monoclonal antibody LM609 directed to human integrin alpha(v)beta3. In the present study, we describe the in vitro affinity maturation of humanized LM609 by using a phage display strategy for the sequential and parallel optimization of three complementarity determining regions of the antibody molecule. The evolved Fab had an affinity of 150 pM and was converted into IgG1 by use of a new mammalian expression vector. The resulting whole antibody, designated JC-7U IgG1, was found to selectively target human KS in a nude mouse model and inhibit tumor growth at a therapeutically relevant dose. Because of its high affinity and its high degree of humanization, JC-7U IgG1 is an excellent drug candidate for therapeutic applications that involve integrin alpha(v)beta3 as the molecular target. Of particular interest is therapy for KS, breast cancer, melanoma, and other cancers in which integrin alpha(v)beta3 is expressed on both angiogenic endothelial cells and tumor cells, which would allow a dual antiangiogenic and antitumor strike with a single drug.

Fully humanized neutralizing antibodies to interleukin-8 (ABX-IL8) inhibit angiogenesis, tumor growth, and metastasis of human melanoma

Interleukin-8 (IL-8) has recently been shown to contribute to human melanoma progression by functioning as a mitogenic and angiogenic factor. In the present study, we investigated whether targeting IL-8 by a fully human anti-IL-8 antibody (ABX-IL8) could be a potential therapeutic strategy to control angiogenesis, growth, and metastasis of melanoma. The human melanoma cells A375SM (high IL-8 producer) and TXM-13 (intermediate IL-8 producer) were injected subcutaneously into nude mice, which were then treated with ABX-IL8 (1 mg/3 times weekly, i.p., for 3 weeks). Tumor growth of both melanomas in ABX-IL8-treated mice was significantly inhibited when compared with control IgG-treated animals. ABX-IL8 treatment also suppressed experimental metastasis when the melanoma cells were injected intravenously. IL-8 blockade by ABX-IL8 significantly inhibited the promoter activity and the collagenase activity of matrix metalloproteinase-2 in human melanoma cells, resulting in decreased invasion through reconstituted basement membrane in vitro. In vivo, ABX-IL8 treatment resulted in decreased expression of matrix metalloproteinase-2, and decreased vascularization (angiogenesis) of tumors concomitant with increased apoptosis of tumor cells. Moreover, in an in vitro vessel formation assay, ABX-IL8 directly interfered with the tubule formation by human umbilical vein endothelial cells. Taken together, these results point to the potential utility of ABX-IL8 as a modality to treat melanoma and other solid tumors either alone or in combination with conventional chemotherapy or other anti-tumor agents.