Abstract
Antibodies and antibody conjugates are currently one of the largest classes of new drug entities under development. These versatile molecules are being investigated for the treatment of many pathological conditions, such as cancer and infectious, inflammatory and autoimmune diseases. Antibodies can exert biological effects as naked antibodies by themselves, or can be used as delivery agents conjugated with various drugs (e.g., immunoconjugates) and as tools of multistep targeting. Site-specific delivery of therapeutic agents has been the ultimate goal of the pharmaceutical industry, as it has the potential to maximize drug efficiency while minimizing side effects. Antibodies have much potential for this objective. Thus, it is useful to summarize some of the main strategies currently being employed for the development of these diverse therapeutic molecules and to highlight the recent novelties in the field. These goals were the focus of the 15th International Conference on Human Antibodies and Hybridomas, held during 14–16 April 2010 in Porto, Portugal.
Since the first meeting in Orlando (FL, USA) in 1990, the International Conference on Human Antibodies and Hybridomas (HAH) was once again perfectly organized for the 15th time, in Porto (Portugal) by Mark C Glassy, General Chairman of this conference series (Nascent Biologics Inc. and Integrated Medical Sciences Association, CA, USA). The HAH 2010 conference secretariat and meetings management did an excellent job (as at all the previous meetings) under the guidance of the conference manager (Caroline Sumner; Hurtmore Commercial Centre, Goldaming, UK) and conference secretariat (John Herriot; Hurtmore Commercial Centre). The Scientific Advisory Committee has hallmarked the scientific value of these meetings, as a great number of top researchers and clinicians and numerous important representatives of well-known relevant companies were present. According to tradition, HAH meetings are organized every 1.5 years, alternating between the USA and Europe, so as to gather as many individuals in the field who are interested in the subject matter as possible. This conference is purposely not a large meeting and therefore has the advantages of being a smaller and more field-specific conference, with a familiar atmosphere and active discussion possibilities. However, the number of participants is steadily growing, and this year the number of conference attendees was one of the highest yet. Besides gathering the highlights of scientific information on antibodies with therapeutic and diagnostic potential, and relevant novelties, the participants can also enjoy the geographic and cultural wealth of the city where each conference is being held. Great cities in the USA (Orlando 1990, San Antonio 1993, Washington, DC 1996 and New York 2009), in Jamaica (2007), in Europe and the Middle East (Cambridge 1991, Amsterdam 1994, Jerusalem 1997, Edinburgh 1999, Prague 2000, Bern 2003, Dublin 2005, Milan 2008 and Porto 2010) as well as the Far East (Osaka 2004) have played host to the meetings. Another attraction of this conference series is that it brings together academic and industry members, which provides a good platform for supporting novelties, opens up collaboration possibilities and is important for all aspects of translational research. It can be concluded that never before were as many sponsors available as this year, so the 15th anniversary of the HAH conference was a real success in all respects.
Important selected key presentations at a glance
Monoclonal antibodies in the clinic, in the pipeline & in our dreams
J Donald Capra (Oklahoma Medical Research Foundation, OK, USA) gave a good overview of monoclonal antibodies (mAbs) currently on the market and in the pipeline, and the remarkable resurgence of antibody-based imaging technologies. He also focused on Fc functions and the molecular signature of pneumococcal infection. Novel results were revealed for the antiprostate stem cell antigen minibody, developed for PET imaging. Novel results regarding T-cell receptor mimics were also shown. Antipolysaccharide passive immunotherapeutics were emphasized as an important supplement to currently available antimicrobial therapies. As these antibodies are completely human in nature and have survived selection at all stages of B-cell development in healthy individuals, they both bind clearly relevant epitopes and are almost certain to produce safe pharmaceutical reagents.
Preclinical & clinical results of pritumumab in brain cancer
Mark Glassy introduced this human IgG1κ antibody, which was derived from regional lymph node B cells from a patient with cervical carcinoma. This antibody binds an altered tumor-associated vimentin, which is highly restricted to specific cancers. The first clinical applications were performed in brain cancers, with clinical reports also conducted on glioblastoma and anaplastic astrocytoma. The reasons why brain cancer was chosen as the clinical target were its high specificity to brain malignancies, rapid clinical end points and ease of BBB crossing. It has been manufactured according to Good Manufacturing Practice, and is characterized by a suitable recruitment and treatment schedule, as well as relatively good response rates for patients (25–30%). Phase III studies are ongoing with low-dose treatment, and pritumumab appears to be a safe and effective therapy in patients with malignant gliomas.
Combination therapies
Zdenka L Jonak (GlaxoSmithKline, PA, USA) summarized important aspects of the design of combination therapies, which seem to be superior to monotherapies owing to mixed mechanisms of action. MAbs for cytokines, enhanced antibody-dependent cytotoxic cells, natural killer cells, cytotoxic T lymphocytes or macrophage activity, suppressed antigen presentation and induction of memory cells are all involved. The various actions of IL-18, an immunmodulator that stimulates the immune system against cancer, were presented.
Therapeutic antibodies in inflammatory/autoimmune diseases
Alois B Lang (GeNeuro, Geneva, Switzerland) described a novel therapeutic approach for the treatment of multiple sclerosis (MS) without targeting molecular or cellular components of the immune system. The authors show that the MS-associated retrovirus particles originated from tissues and cells collected from MS patients. The therapeutic approach may block the inflammatory cascade initiated by Env using mAbs that neutralize the Env protein.
Role of CD44 & Rhamm (CD168) in cancer & autoimmune inflammation
David Naor (The Hebrew University, Jerusalem, Israel) explained the substantial involvement of CD44 in various pathological aspects of cancer and autoimmune inflammations. Anti-CD44 mAbs or gene vaccination with CD44 cDNAs markedly reduced pathological manifestations in animal models of cancer and autoimmunity. Cell-surface CD44 supports cell migration and transmits apoptotic signals to target cells. The authors found that joint inflammatory cells of patients with rheumatoid arthritis express a CD44 variant (CD44vRA) not expressed in normal cells of the same patient. It could be proved that when CD44 is genetically depleted in embryonic mice, receptor hyaluronic acid-mediated motility (CD168) replaces its activity in supporting cell migration and maintenance of collagen-induced arthritis (CIA). The authors discovered that injection of soluble receptor hyaluronic acid-mediated motility into NOD mice with Type 1 diabetes induced resistance to the disease.
Normal IGHV1–69-derived B-cell repertoire contains stereotypic patterns characteristic of unmutated chronic lymphocytic leukemia
Kathy N Potter (Southampton University, UK) announced that a snapshot of the naive B-cell repertoire reveals subsets of B cells that are closely related to those characteristic of chronic lymphocytic leukemia (CLL). They found that conserved patterns in the 51p1-encoded IgM of normal B cells might suggest a restricted sequence repertoire shaped by evolution to recognize common pathogens. Proliferative pressure on these cells is the likely route to the unmutated subset CLL.
The arsenal of innovations: a part of all
Epitope space as defined by proteomic similarity
Darja Kanduc (University of Bari, Italy) described results based on a robust set of experimental data analysis, suggesting that low levels of sequence similarity to the host proteome modulates the B-cell repertoire in the humoral immune response. A structured meta-analysis of the scientific literature further supported the authors‘ low similarity theory. The low level of sequence identity to the host proteome was a minimum common denominator unifying the heterogeneous assembly of epitopes experimentally validated, described and used all over the world. The low similarity theory may have important implications in science and medicine.
Tribody
Nico Mertens‘ (Biotecnol SA, Oeiras, Portugal) presentation provided an excellent overview of novel antibody-derived biopharmaceuticals. Tribodies were developed as bispecific antibodies that either targeted two different tumor antigens (trispecific) or one tumor antigen bivalently, while monovalent-targeting effector cell activators (e.g., CD3 on T cells) were produced and demonstrated activity. In addition, immunocytokines with IL-2 could be produced and were able to target the cytokine to specific cells. Tribodies are good scaffolds for constructing trivalent, bispecific and trispecific antibody derivatives or antibody–drug conjugates.
BiTE antibodies
Tobias Raum (Micromet Ag, Munich, Germany) described BiTE antibody technology, which is based on single-chain bispecific antibody molecules that bind to CD3 on cytotoxic T cells, and to other surface antigens on the target cell. The close contact leads to killing of the target cell. The first BiTE antibody, blinatumomab, was directed against CD19 in non-Hodgkin‘s lymphoma cancer cells, and it has been proven to have efficacy in a clinical Phase I trial.
Two-in-one antibodies
Germaine Fuh (Genentech Inc., CA, USA) introduced an engineering approach using phage display that led to the development of antibody-combining sites interacting with unrelated protein antigens. Crystallographic and mutagenic studies of the HER2/VEGF dual-specific Fab revealed an extensive overlap of the antibody surface areas contacting the two antigens. However, distinct sets of residues were engaged energetically with the two antigens. The high dual affinity was achieved and translated to dual action in vitro and in vivo.
Potential capacities of B lymphocytes in the tumor tissue
The original hypothesis-based investigations of Beatrix Kotlan (National Institute of Oncology, Budapest, Hungary) resulted in the development of human antibody fragments with a specific binding capacity for tumor-associated sialylated glycosphingolipid molecules. The GD3 ganglioside antibody-related theoretical and experimental ‘proof of principle‘ supports the specific tumor antigen recognition and binding capacity of tumor-infiltrating B lymphocytes. Although these findings explain some of the potential B-cell functions in breast carcinomas and melanomas, the main questions about the characteristics and potential capacities of B cells infiltrating tumors compared with B cells in lymph nodes and peripheral blood have not yet been answered.
Novel antibody functions from novel antibody structure
Jim W Larrick (Panorama Research Institute, CA, USA) presented the novel heterodimeric Fc fusion proteins (‘trophokines‘) designed and constructed to induce Met–Ron heterodimerization. These trophokines contain HGF–Fc and MSP–Fc fusion proteins, which form heterodimers. These newly designed molecules prevent target cell apoptosis and promote tissue regeneration. Improved plasma half-life, ease of manufacture and purification with other downstream developmental processes are also advantages of these proteins. These novel proteins are likely to provide therapeutic benefit to patients suffering from a wide range of pathological conditions, such as liver cirrhosis, liver fibrosis, renal failure, delayed wound healing and chemotherapy-induced liver or renal damage.
New human monoclonal antibody platform based on transgenic rats
Roland Buelow (Open Molecular Technology Inc., CA, USA) presented a discussion on the zinc-finger nuclease-mediated technique to generate immunoglobulin-knockout rats. Microinjection of zinc-finger nucleases specific for rat IgM, Vλ or Cκ into rat embryos leads to numerous animals carrying a disruption at the target loci. Immunoglobulin transgenes, encoding human κ or λ light chains, and a heavy chain were introduced into the rat genome using conventional embryo microinjection. Breeding of immunoglobulin-transgenic and -knockout animals is ongoing, and will result in the development of a new platform for generating human antibody therapeutics.
A new platform for nonantibody protein drugs was introduced by Manuel Baca (Medimmune Inc., MD, USA) as alternative scaffolds for next-generation protein drugs. Not only were some types of these molecules described, but so were the characteristics that support any therapeutic usage, such as high-affinity binding and specificity, and good tissue/tumor penetration.
Direct translation into the clinic
Cancer
Preclinical development of a novel therapeutic antibody to treat pancreas & colorectal cancer
Andrew Bristol (Neogenix Oncology Inc., NY, USA) explained that NPC-1C is a chimeric monoclonal antibody recognizing aberrantly glycosylated forms of MUC5AC expressed specifically by human pancreatic and colorectal tumor tissues and cell lines. No considerable cross-reaction was found with other tumor cell lines or normal human tissues. NPC-1C is safe and efficacious, and a Phase I clinical trial has been initiated.
Novel human anti-ErbB2 immunoreagents were introduced by Claudia De Lorenzo (Univerity of Napoli, Italy): human anti-ErbB2 scFv (erbicin) with either a human RNase or the Fc region of a human IgG1. The erbicin-derived immunoagents (EDIAs) target an ErbB2 epitope in breast cancer cells (different from herceptin). It was hypothesized that EDIAs could be effective for the treatment of some breast cancer patients who could not be cured with herceptin.
Antitumor properties of T-cell receptor mimic mAbs
In a lecture presented by John Weidanz (Receptor-Logic Inc., TX, USA), substantial explanation was given regarding the advantages of T-cell receptor mimics, the novel target discovery possibilities and its advantages (e.g., direct sampling and direct comparison of diseased vs healthy cells) and the flow chart of its production.
New cancer-specific targets defined by natural human mAbs
Nicole Schatz from the group of HP Vollmers (University of Wurtzburg, Germany) introduced their natural PAT SM6 IgM antibody that reacts only with cancer cells, internalizes when administered and causes apoptosis in stomach carcinoma cells. They compared its characteristics with another of their human antibodies, PAT-BA4, which also reacts with cancer cells. The PAT SM6 IgM antibody was shown to have antitumor effects as it was demonstrated to inhibit cell proliferation in MTT assay, had apoptosis-inducing capacity and inhibited cell adhesion and cell motility. Their work strongly supports the statement that natural IgM antibodies represent a huge reservoir of therapeutic antibodies.
Infectious diseases
Human mAbs against influenza viruses
Roberto Burioni (Universita Vita-Salute, San Raffaele, Milan, Italy) described two human mAbs (PN-SIA49 and PN-SIA-28), and concluded that broadly neutralizing antibodies are produced in the course of influenza infection. These molecules are good candidates for future in vitro prophylactic and therapeutic studies. They may be of great help for the identification of highly conserved epitopes to be used in new broad-range vaccine strategies.
Antibodies were generated by genetic immunization against hepatitis C virus (HCV) receptor proteins, according to the presentation by John Thompson (Genovac GmbH, Freiburg, Germany). Antibodies directed against one receptor have been shown to block entry of all six known HCV genotypes as well as infection of all HCV quasispecies from two chronic HCV sufferers. No toxicity of these antibodies was detected. Liver cells were protected from HCV infection when added prophylactically, and the viral load on liver cells already infected with the virus was reduced.
Prevention of group B Streptococcus disease by mAbs
Eszter Nagy (Intercell AG, Vienna, Austria) presented interesting findings regarding passive immunization and lethal challenge studies with multiple group B Streptococcus strains. They observed a protective effect of rabbit polyclonal and murine mAbs specific for four cell wall-anchored adhesins, FbsA, BibA, PilA and PilB, and a hypothetical protein, gbs0233. Fab fragments of the FbsA and BibA mAbs fully protected the animals, suggesting that blocking the function of these proteins was the major mode of action. These data are supportive of the development of immune prophylaxis with human mAbs for prematurely born neonates who receive low levels of antibodies by maternofetal transport and who do not have fully developed phagocytic and complement activity.
The breadth and potency of virus-neutralizing antibodies was the topic of the plenary lecture of Antonio Lanzavecchia (Institute for Bioresearch in Biomedicine, Bellinzona, Switzerland). He focused on the heterosubtypic response consistently observed in some individuals, the epitope variability of pandemic viruses, the specificity of heterosubtypic antibodies and the defined immunoglobulin heavy chain V gene usage.
Take-home messages
There was substantial information provided at the conference about the great novelties of human antibody research and the various potential for therapeutic usage in many disease-related aspects. With such broad and diverse topics of high caliber presented at the meeting, it is difficult to select which one is of most interest. I selected the conference highlights to help those not in attendance to obtain a better understanding of the researchers and clinicians who have participated at the HAH conferences. Based on the various presentations, innovative strategies that exploit the potential capacity and innate ability of antibodies to bind to an antigen of interest are promising. There is a challenge in the field for antibody conjugates to meet all of the desired criteria, namely specificity, safety and stability, among others, as well as being assembled in a perfect way to transport the therapeutic payload to the target diseased site.
The next conference, the 16th International Conference on Human Antibodies and Hybridomas, will take place on 2–4 November 2011 at the Novotel Cannes Mountfleury, Cannes, France.
Acknowledgements
The author is thankful to Mark Glassy, Chairman, and offial organizers Caroline Sumner and John Herriot for arranging this wonderful conference over the years.
Financial & competing interests disclosure
Beatrix Kotlan acknowledges the funding from the Fulbright Grant (No. 120610/2006) and has received an award from the Harry J Lloyd Charitable Trust Melanoma Foundation 2010, for research on TIL-B and human antibodies. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
No writing assistance was utilized in the production of this manuscript.