- Email: [email protected]
Therapeutic Antibody Technology 97
Immunotechnology 3 (1998) 303 – 307
Meeting report
Therapeutic Antibody Technology 97 James W. Larrick a,*, Jorge Gavilondo b a
Palo Alto Institute of Molecular Medicine, Mountain View, CA 94043, USA b Centro de Ingenieria Genetica y Biotechnologia, La Ha6ana, Cuba Received 10 October 1997; accepted 21 October 1997
Abstract Almost 200 antibody aficionados attended the Therapeutic Antibody Technology 97 meeting, held September 21–24, 1997 at the Holiday Inn, Union Square in the heart of San Francisco, CA. The meeting was sponsored by the Palo Alto Institute of Molecular Medicine and organized by James W. Larrick (PAIMM) and Dennis R. Burton (Scripps Research Institute). The meeting featured excellent discussions on many interesting talks and a number of poster presentations. It is likely that another meeting will be organized in 2 years, however in the meantime, an effort is underway to organize a ‘Virtual Antibody Society’ to be set up on the web server at Scripps Research Institute in La Jolla, CA (Questions and comments on this project can be sent to: [email protected] or [email protected]). Richard Lerner (Scripps) gave the keynote address on ‘Catalytic Antibodies’, describing recent work with Carlos Barbas on so-called reactive immunization to generate a high activity aldolase catalytic antibody. This antibody, soon to be described in an article in Science, is the first commercially available catalytic antibody. © 1998 Elsevier Science B.V.
1. Session 1. Antibody interaction with antigen Ian Wilson (Scripps) began the first morning with an elegant talk on conformational changes in antibody–antigen interactions. On the basis of evidence obtained from the structural studies of the interactions between antibody binding sites and progesterone-related compounds, influenza * Corresponding author.
virus derived peptides, the V3 domain of HIV-1 gp120 and others, Dr Wilson showed that position rearrangements occurred mainly in the H3 loop, leading to profound conformational alterations in its projection. Less important changes were noted in L1, L3 and H1, none in L2 and some local rotational effects in the H2 loop. Some rearrangements were also documented in the whole VL–VH 3-D structure. The talk emphasized the fact that, while there are no rules con-
1380-2933/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S 1 3 8 0 - 2 9 3 3 ( 9 7 ) 1 0 0 0 6 - 9
304
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
cerning the way the H3 loop structure, and that of other loops, will rearrange, conformational changes on the CDRs and the Fv probably play an important role in many antibody-antigen interactions. Dr Wilson also provided data indicating that there are also differences in structure between bound and free TCR, with major changes in the a3 and b3 loops. Peter Colman (CSIRO, Australia) followed with a dissertation about electrostatic and shape complementarity at antibody – antigen interfaces. After referring to the shock of having unrelated sequences fitting into pockets (binding sites) derived from other sequences, a situation described by him as ‘promiscuity in the interfaces’, he noted work from others that documented that changes outside the CDRs that could make for increased affinity and fit. Roy Mariuzza (Maryland) has performed interesting experiments looking at the binding surfaces of monoclonal D1.3 to its antigen (HEL) and to an anti-ID antibody. This interface is controlled by a single set of control residues with water molecules acting as ‘adaptors’. The same protein recognizes two different ligands that are energetically distinct but structurally similar. Neil Greenspan (Case Western) gave an interesting dissertation on affinity, complementarity, cooperativity and specificity in antibody recognition. Clemencia Pinilla (Torrey Pines) described recent work using combinatorial libraries to study immunorecognition and molecular mimicry. Jamie Scott (Simon Fraser University) presented her recent work with peptide libraries expressed on phage that bind human antibodies against HIV1 and their use in vaccines against AIDS. This may prove to be a novel means of identifying neutralizing antigens for HIV vaccines.
kappa locus on chromosome 2 has 40 functional light chain VL segments and five J segments. The lambda regions on chromosome 22 has 31 variable segments with four J segments. Sequence analysis indicates that much of the germline diversity occurs near the center of the antigen binding site and the process of somatic mutation spreads diversity to the periphery of the site. The Cambridge group has used this information to design and construct synthetic antibody libraries with an excellent repertoire. Along these lines, Achim Knappik (Morphosys) described successful efforts in Munich to construct synthetic libraries using codon mutagenesis and cassettes of each CDR. The development of the so-called Xenomouse (Aya Jacobovits, AbGenix) is a tour de force. These mice have a quite functional human antibody repertoire that permits generation of human monoclonal antibodies via conventional murine monoclonal somatic hybridization methodology. James Marks (UCSF) described his efforts to improve antibody affinity using chain shuffling and parsimonious mutagenesis. Each of these methods can improve affinity 6– 10-fold. Similar large scFv libraries containing diverse, high affinity antibodies were described by Alex Duncan (Cambridge Antibody Technology). In addition, he described the method of guided selection to focus the scFv phage on a target of interest. CAT will generate phage derived scFv antibodies gratis for those interested to provide interesting and important antigens. Carlos Barbas (Scripps) described work on the evolution of covalent antibody catalysts. His lab has identified an aldolase antibody with broad catalytic activity.
2. Session 2. The generation of human antibodies
3. Session 3. Novel approaches, related technology
Ian Tomlinson (Cambridge) summarized the present state of knowledge on the human antibody loci on chromosomes 2, 14 and 22. The heavy chain locus on chromosome 14 is comprised of 51 functional VH segments, 7 pseudogenes, 25 D segments and six J segments. The
Zelig Eshhar (Weizmann Institute) has pioneered the development of ‘T-bodies’. He has successfully generated chimeric T cell receptors with antibody-specificity to redirect genetically engineered lymphocytes for cancer therapy. Peter Hudson (CSIRO, Australia) described his
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
work on the design and expression of high-avidity diabodies and triabodies for cell targeting. Herren Wu (Ixsys) described efforts in this lab to affinity mature Vitaxin, a humanized antiavb3 antibody. Ton Logtenberg (University Hospital Utrecht) demonstrated the used of synthetic antibody phage display libraries combined with substractive techniques to identify differentially-expressed molecules on immune and cancer cells. Andreas Pluckthun (Univ. of Zurich) described an entirely novel means to generate and evolve proteins using ribosome display. This cell-free selection and evolution method permits a larger piece of sequence space to be searched than using antibody libraries. The technology will eventually be available from Morphosys (Munich). Hennie Hoogenboom (Maastricht, The Netherlands) also described the used of phage to obtain anti-tumor antibodies and antibodies to novel receptors. His laboratory has expressed cDNAs libraries and HLA molecules on phage. Both of these approaches have many interesting applications. Willem Stemmer (Maxygen) described the method he pioneered to engineer the activity of enzymes or antibodies. This method involves shuffling of bits of DNA encoding a family of proteins or a library into which diversity has been introduced, a method George Smith called ‘Sexual PCR’. The method has successfully been used to engineer more active enzymes, (e.g. cephalosporinase) or proteins with improved activity (e.g. green fluorescent protein, interferons, etc.).
4. Session 4. Antibodies or modified antibodies as effector molecules Sherie Morrison (UCLA) described several advances from her lab. She has developed the means of producing secretory IgA in myeloma cells and hopes to be able to make antibodies in chicken eggs via transgenic technology. Michael Pfreundschuh (University of Saarland, Germany) described work from his laboratory on the use of bispecific antibodies in lymphoma therapy. Perhaps the most amusing talk was given by Richard Junghans. As befits a Harvard Profes-
305
sor, he gave a historical account of the Brambell receptor (FcRB). Recent evidence with b2 microglobulin knockout mice has been used to unequivocally demonstrate that this receptor is the mediator of transmission of passive antibody immunity in neonates and participates in the protection from catabolism of IgG. Wayne Maracso (Harvard) has pioneered the development of intrabodies, antibodies expressed inside cells. This method appears quite promising as a form of anti-HIV gene therapy. Cell biologists have identified a number of protein signals that have been used advantageously to target the intrabodies. An intrabody targeting the tat protein of HIV will be in trials in the near future. Austin Gurney (Genentech) described how his laboratory has used antibodies in drug discovery. This group has used the technology to identify a ligand for the muscle specific kinase receptor (MuSK). Jorge V. Gavilondo (Centro de Ingenieria Genetica y Biotecnologia, Havana, Cuba), was the last speaker of the day. His talk on the subject of ‘Cuban Biotechnology and Antibody Research’ illustrated the several mouse monoclonal antibodies developed by Cuban groups and in clinical studies in that country. Special mention was made of antiEGF receptor and anti-mucin radiolabelled MAbs, that have successfully finished phase I trials for imaging in different human carcinomas. Data was also presented on the ongoing clinical trials where an anti-CD6 mouse MAb has been used systemically for the treatment of cutaneous T cell lymphoma and topically in patients with psoriasis. In the latter, the application of a MAb enriched gel induced a complete response in the majority of the individuals, without important side effects. Finally, Dr Gavilondo referred to the work being done in Cuba in the field of antibody engineering. Several mouse MAbs have been humanized using a binding site T-cell epitope identification and substitution procedure for which a patent has been recently awarded. Chimeric mouse–human anti-CD6 antibodies have been produced in the milk of transgenic mice and rabbits. Also, scFv antibody fragments have been expressed in bacteria and yeast for industrial applications (purification of recombinant vaccine antigens) and for radioimaging.
306
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
5. Session 5: Antibodies in the study, prophylaxis and therapy of disease Despite some spectacular failures of antibody therapy in the past (e.g. Centoxin, E5, etc.), antibody therapeutics account for over 1/3 of products in FDA approved clinical trials in the USA. A partial list of antibodies that have successfully completed phase III studies or have received market approval in the US and Europe was presented. These include OKT3 (anti-CD3), anti-CD20 (IDEC/Genentech), anti-17-1a (PanoRx – Glaxo/ Centocor), anti-RSV (Medimmune), GPIIa/IIIb (ReoPro–Centocor), human Mab for colo-rectal imaging (PerImmune), anti-small cell lung cancer for imaging (Verluma – NeoRx/Dupont), anti-IL-2 receptor (anti-Tac/Zenapax – Protein Design). Dennis Burton, Paul Parren (Scripps) and coworkers have generated anti-HIV-1 antibodies using phage display libraries prepared from longterm seropositive asymptomatic individuals. Most of the antibodies recognized ‘viral debris’, i.e. non-native forms of HIV envelope proteins. One antibody, B12, demonstrated binding to a native determinant on primary viral isolates. This antibody was protective at high concentrations (50 mg/kg =500 ug/ml serum concentrations) in the HuSCID–PBL model. Thus, high levels of a suitable antibody (100×the 90% neutralization titer) provided in vivo protection from infection, while there was little benefit when passive therapy was used for an established infection. These studies have obvious relevance to vaccine design. Cary Queen (Protein Design Labs) presented results of recent clinical trials of Zenapax, the humanized form of the Tac murine monoclonal antibody originally isolated in 1981. In two multicenter, double-blind, placebo controlled trials of cadaveric renal allograft transplantation, Zenapax demonstrated significant benefit (fewer rejection episodes, fewer grafts lost and less mortality) versus standard treatment of cyclosporin A/prednisone (used in Europe) or cyclosporin A/prednisone/azothioprine (used in USA). Remarkably, there was no toxicity and the humanized antibody was non-immunogenic. Other studies by the PDL group indicate that the humanized antibodies have prolonged half-lives in
patients and repeated injections (intravenously or subcutaneously) for over 250 days elicit no antihuman antibody response. Elegant studies of antibody-mediated neutralization of rhinovirus were presented by Tom Smith (Purdue University). X-ray crystallographic and cryo-electron microscopy studies demonstrated that neutralizing Fab17-IA does not induce conformational changes in the human rhinovirus 14. Instead, the antibody undergoes a large conformational change upon binding and penetrates deeply into the canyon bound by ICAM-1 the cellular receptor for HRV. John Reno (NeoRx) told of recent improvements in the pre-targeting approach for cancer radioimmunotherapy. Their anti-EPCAM antibody linked to strepavidin is being produced in corn by Monsant. After the initial infusion, excess antibody is removed using a poly-galactose –biotin reagent followed by radioactive yttrium-90, chelated to a methylated form of DOTA–biotin. This approach provides complete cures in mice with established xenograft tumors (breast, colon, lung) and dramatic results in several patients. Pre-targeting produces a much improved AUC ratio of tumor to blood with improved therapeutic index. Roberto Ceriani (Contra Costa Cancer Center) presented data on the development of an anti-mucin (MUC1) breast cancer antibody (BrE3). Yttrium-90 labeled antibody has demonstrated a \ 50% reduction in tumor tissue in 4/8 patients treated to date. Brian Dallaire (IDEC) reviewed the clinical development of IDEC-C2B8-Rituximab, a chimaeric anti-CD20 IgG1 kappa antibody for treatment of relapsed low-grade non-Hodgkin’s lymphoma. In a phase III trial, patients receiving 375 mg/m2 weekly for four infusions demonstrated an overall response rate over 50%. Rituximab also improved the efficacy of CHOP therapy. In all cases, the antibody was well tolerated with minimal adverse effects. Melvyn Little (German Cancer Center, Heidelberg) described improvement of an OKT3 bispecific diabody (CD3 & CD19) for leukemia therapy. Two substitutions markedly improved production: heavy chain E6– \ Q and Heavy chain C100– \ S. Anthony Williamson (Scripps) and co-workers have successfully generated anti-
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
prion antibodies. PrP null mice were immunized with prion rods or detergent solubilized PrP and conformational antibodies were rescued from combinatorial Fab libraries.
.
307
In summary, a diverse group of presentations provided a snapshot of this rapidly moving field. Antibody technology continues to mature with a bright future.
.
Meeting report
Therapeutic Antibody Technology 97 James W. Larrick a,*, Jorge Gavilondo b a
Palo Alto Institute of Molecular Medicine, Mountain View, CA 94043, USA b Centro de Ingenieria Genetica y Biotechnologia, La Ha6ana, Cuba Received 10 October 1997; accepted 21 October 1997
Abstract Almost 200 antibody aficionados attended the Therapeutic Antibody Technology 97 meeting, held September 21–24, 1997 at the Holiday Inn, Union Square in the heart of San Francisco, CA. The meeting was sponsored by the Palo Alto Institute of Molecular Medicine and organized by James W. Larrick (PAIMM) and Dennis R. Burton (Scripps Research Institute). The meeting featured excellent discussions on many interesting talks and a number of poster presentations. It is likely that another meeting will be organized in 2 years, however in the meantime, an effort is underway to organize a ‘Virtual Antibody Society’ to be set up on the web server at Scripps Research Institute in La Jolla, CA (Questions and comments on this project can be sent to: [email protected] or [email protected]). Richard Lerner (Scripps) gave the keynote address on ‘Catalytic Antibodies’, describing recent work with Carlos Barbas on so-called reactive immunization to generate a high activity aldolase catalytic antibody. This antibody, soon to be described in an article in Science, is the first commercially available catalytic antibody. © 1998 Elsevier Science B.V.
1. Session 1. Antibody interaction with antigen Ian Wilson (Scripps) began the first morning with an elegant talk on conformational changes in antibody–antigen interactions. On the basis of evidence obtained from the structural studies of the interactions between antibody binding sites and progesterone-related compounds, influenza * Corresponding author.
virus derived peptides, the V3 domain of HIV-1 gp120 and others, Dr Wilson showed that position rearrangements occurred mainly in the H3 loop, leading to profound conformational alterations in its projection. Less important changes were noted in L1, L3 and H1, none in L2 and some local rotational effects in the H2 loop. Some rearrangements were also documented in the whole VL–VH 3-D structure. The talk emphasized the fact that, while there are no rules con-
1380-2933/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S 1 3 8 0 - 2 9 3 3 ( 9 7 ) 1 0 0 0 6 - 9
304
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
cerning the way the H3 loop structure, and that of other loops, will rearrange, conformational changes on the CDRs and the Fv probably play an important role in many antibody-antigen interactions. Dr Wilson also provided data indicating that there are also differences in structure between bound and free TCR, with major changes in the a3 and b3 loops. Peter Colman (CSIRO, Australia) followed with a dissertation about electrostatic and shape complementarity at antibody – antigen interfaces. After referring to the shock of having unrelated sequences fitting into pockets (binding sites) derived from other sequences, a situation described by him as ‘promiscuity in the interfaces’, he noted work from others that documented that changes outside the CDRs that could make for increased affinity and fit. Roy Mariuzza (Maryland) has performed interesting experiments looking at the binding surfaces of monoclonal D1.3 to its antigen (HEL) and to an anti-ID antibody. This interface is controlled by a single set of control residues with water molecules acting as ‘adaptors’. The same protein recognizes two different ligands that are energetically distinct but structurally similar. Neil Greenspan (Case Western) gave an interesting dissertation on affinity, complementarity, cooperativity and specificity in antibody recognition. Clemencia Pinilla (Torrey Pines) described recent work using combinatorial libraries to study immunorecognition and molecular mimicry. Jamie Scott (Simon Fraser University) presented her recent work with peptide libraries expressed on phage that bind human antibodies against HIV1 and their use in vaccines against AIDS. This may prove to be a novel means of identifying neutralizing antigens for HIV vaccines.
kappa locus on chromosome 2 has 40 functional light chain VL segments and five J segments. The lambda regions on chromosome 22 has 31 variable segments with four J segments. Sequence analysis indicates that much of the germline diversity occurs near the center of the antigen binding site and the process of somatic mutation spreads diversity to the periphery of the site. The Cambridge group has used this information to design and construct synthetic antibody libraries with an excellent repertoire. Along these lines, Achim Knappik (Morphosys) described successful efforts in Munich to construct synthetic libraries using codon mutagenesis and cassettes of each CDR. The development of the so-called Xenomouse (Aya Jacobovits, AbGenix) is a tour de force. These mice have a quite functional human antibody repertoire that permits generation of human monoclonal antibodies via conventional murine monoclonal somatic hybridization methodology. James Marks (UCSF) described his efforts to improve antibody affinity using chain shuffling and parsimonious mutagenesis. Each of these methods can improve affinity 6– 10-fold. Similar large scFv libraries containing diverse, high affinity antibodies were described by Alex Duncan (Cambridge Antibody Technology). In addition, he described the method of guided selection to focus the scFv phage on a target of interest. CAT will generate phage derived scFv antibodies gratis for those interested to provide interesting and important antigens. Carlos Barbas (Scripps) described work on the evolution of covalent antibody catalysts. His lab has identified an aldolase antibody with broad catalytic activity.
2. Session 2. The generation of human antibodies
3. Session 3. Novel approaches, related technology
Ian Tomlinson (Cambridge) summarized the present state of knowledge on the human antibody loci on chromosomes 2, 14 and 22. The heavy chain locus on chromosome 14 is comprised of 51 functional VH segments, 7 pseudogenes, 25 D segments and six J segments. The
Zelig Eshhar (Weizmann Institute) has pioneered the development of ‘T-bodies’. He has successfully generated chimeric T cell receptors with antibody-specificity to redirect genetically engineered lymphocytes for cancer therapy. Peter Hudson (CSIRO, Australia) described his
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
work on the design and expression of high-avidity diabodies and triabodies for cell targeting. Herren Wu (Ixsys) described efforts in this lab to affinity mature Vitaxin, a humanized antiavb3 antibody. Ton Logtenberg (University Hospital Utrecht) demonstrated the used of synthetic antibody phage display libraries combined with substractive techniques to identify differentially-expressed molecules on immune and cancer cells. Andreas Pluckthun (Univ. of Zurich) described an entirely novel means to generate and evolve proteins using ribosome display. This cell-free selection and evolution method permits a larger piece of sequence space to be searched than using antibody libraries. The technology will eventually be available from Morphosys (Munich). Hennie Hoogenboom (Maastricht, The Netherlands) also described the used of phage to obtain anti-tumor antibodies and antibodies to novel receptors. His laboratory has expressed cDNAs libraries and HLA molecules on phage. Both of these approaches have many interesting applications. Willem Stemmer (Maxygen) described the method he pioneered to engineer the activity of enzymes or antibodies. This method involves shuffling of bits of DNA encoding a family of proteins or a library into which diversity has been introduced, a method George Smith called ‘Sexual PCR’. The method has successfully been used to engineer more active enzymes, (e.g. cephalosporinase) or proteins with improved activity (e.g. green fluorescent protein, interferons, etc.).
4. Session 4. Antibodies or modified antibodies as effector molecules Sherie Morrison (UCLA) described several advances from her lab. She has developed the means of producing secretory IgA in myeloma cells and hopes to be able to make antibodies in chicken eggs via transgenic technology. Michael Pfreundschuh (University of Saarland, Germany) described work from his laboratory on the use of bispecific antibodies in lymphoma therapy. Perhaps the most amusing talk was given by Richard Junghans. As befits a Harvard Profes-
305
sor, he gave a historical account of the Brambell receptor (FcRB). Recent evidence with b2 microglobulin knockout mice has been used to unequivocally demonstrate that this receptor is the mediator of transmission of passive antibody immunity in neonates and participates in the protection from catabolism of IgG. Wayne Maracso (Harvard) has pioneered the development of intrabodies, antibodies expressed inside cells. This method appears quite promising as a form of anti-HIV gene therapy. Cell biologists have identified a number of protein signals that have been used advantageously to target the intrabodies. An intrabody targeting the tat protein of HIV will be in trials in the near future. Austin Gurney (Genentech) described how his laboratory has used antibodies in drug discovery. This group has used the technology to identify a ligand for the muscle specific kinase receptor (MuSK). Jorge V. Gavilondo (Centro de Ingenieria Genetica y Biotecnologia, Havana, Cuba), was the last speaker of the day. His talk on the subject of ‘Cuban Biotechnology and Antibody Research’ illustrated the several mouse monoclonal antibodies developed by Cuban groups and in clinical studies in that country. Special mention was made of antiEGF receptor and anti-mucin radiolabelled MAbs, that have successfully finished phase I trials for imaging in different human carcinomas. Data was also presented on the ongoing clinical trials where an anti-CD6 mouse MAb has been used systemically for the treatment of cutaneous T cell lymphoma and topically in patients with psoriasis. In the latter, the application of a MAb enriched gel induced a complete response in the majority of the individuals, without important side effects. Finally, Dr Gavilondo referred to the work being done in Cuba in the field of antibody engineering. Several mouse MAbs have been humanized using a binding site T-cell epitope identification and substitution procedure for which a patent has been recently awarded. Chimeric mouse–human anti-CD6 antibodies have been produced in the milk of transgenic mice and rabbits. Also, scFv antibody fragments have been expressed in bacteria and yeast for industrial applications (purification of recombinant vaccine antigens) and for radioimaging.
306
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
5. Session 5: Antibodies in the study, prophylaxis and therapy of disease Despite some spectacular failures of antibody therapy in the past (e.g. Centoxin, E5, etc.), antibody therapeutics account for over 1/3 of products in FDA approved clinical trials in the USA. A partial list of antibodies that have successfully completed phase III studies or have received market approval in the US and Europe was presented. These include OKT3 (anti-CD3), anti-CD20 (IDEC/Genentech), anti-17-1a (PanoRx – Glaxo/ Centocor), anti-RSV (Medimmune), GPIIa/IIIb (ReoPro–Centocor), human Mab for colo-rectal imaging (PerImmune), anti-small cell lung cancer for imaging (Verluma – NeoRx/Dupont), anti-IL-2 receptor (anti-Tac/Zenapax – Protein Design). Dennis Burton, Paul Parren (Scripps) and coworkers have generated anti-HIV-1 antibodies using phage display libraries prepared from longterm seropositive asymptomatic individuals. Most of the antibodies recognized ‘viral debris’, i.e. non-native forms of HIV envelope proteins. One antibody, B12, demonstrated binding to a native determinant on primary viral isolates. This antibody was protective at high concentrations (50 mg/kg =500 ug/ml serum concentrations) in the HuSCID–PBL model. Thus, high levels of a suitable antibody (100×the 90% neutralization titer) provided in vivo protection from infection, while there was little benefit when passive therapy was used for an established infection. These studies have obvious relevance to vaccine design. Cary Queen (Protein Design Labs) presented results of recent clinical trials of Zenapax, the humanized form of the Tac murine monoclonal antibody originally isolated in 1981. In two multicenter, double-blind, placebo controlled trials of cadaveric renal allograft transplantation, Zenapax demonstrated significant benefit (fewer rejection episodes, fewer grafts lost and less mortality) versus standard treatment of cyclosporin A/prednisone (used in Europe) or cyclosporin A/prednisone/azothioprine (used in USA). Remarkably, there was no toxicity and the humanized antibody was non-immunogenic. Other studies by the PDL group indicate that the humanized antibodies have prolonged half-lives in
patients and repeated injections (intravenously or subcutaneously) for over 250 days elicit no antihuman antibody response. Elegant studies of antibody-mediated neutralization of rhinovirus were presented by Tom Smith (Purdue University). X-ray crystallographic and cryo-electron microscopy studies demonstrated that neutralizing Fab17-IA does not induce conformational changes in the human rhinovirus 14. Instead, the antibody undergoes a large conformational change upon binding and penetrates deeply into the canyon bound by ICAM-1 the cellular receptor for HRV. John Reno (NeoRx) told of recent improvements in the pre-targeting approach for cancer radioimmunotherapy. Their anti-EPCAM antibody linked to strepavidin is being produced in corn by Monsant. After the initial infusion, excess antibody is removed using a poly-galactose –biotin reagent followed by radioactive yttrium-90, chelated to a methylated form of DOTA–biotin. This approach provides complete cures in mice with established xenograft tumors (breast, colon, lung) and dramatic results in several patients. Pre-targeting produces a much improved AUC ratio of tumor to blood with improved therapeutic index. Roberto Ceriani (Contra Costa Cancer Center) presented data on the development of an anti-mucin (MUC1) breast cancer antibody (BrE3). Yttrium-90 labeled antibody has demonstrated a \ 50% reduction in tumor tissue in 4/8 patients treated to date. Brian Dallaire (IDEC) reviewed the clinical development of IDEC-C2B8-Rituximab, a chimaeric anti-CD20 IgG1 kappa antibody for treatment of relapsed low-grade non-Hodgkin’s lymphoma. In a phase III trial, patients receiving 375 mg/m2 weekly for four infusions demonstrated an overall response rate over 50%. Rituximab also improved the efficacy of CHOP therapy. In all cases, the antibody was well tolerated with minimal adverse effects. Melvyn Little (German Cancer Center, Heidelberg) described improvement of an OKT3 bispecific diabody (CD3 & CD19) for leukemia therapy. Two substitutions markedly improved production: heavy chain E6– \ Q and Heavy chain C100– \ S. Anthony Williamson (Scripps) and co-workers have successfully generated anti-
J.W. Larrick, J. Ga6ilondo / Immunotechnology 3 (1998) 303–307
prion antibodies. PrP null mice were immunized with prion rods or detergent solubilized PrP and conformational antibodies were rescued from combinatorial Fab libraries.
.
307
In summary, a diverse group of presentations provided a snapshot of this rapidly moving field. Antibody technology continues to mature with a bright future.
.