While we were busy dancing, other folks in California were working out how to generate human genes in cell factories. As it turned out, the idea that the power of DNA could be harnessed to produce medicine for human use was a pretty good one, and that’s how hundreds of biotech companies got started. First Cetus (Emeryville, 1971), then Genentech (South San Francisco, 1976), then Biogen (Geneva, 1978), and then Amgen (Thousand Oaks, 1980) started up – and there are now more than 1000 biotech companies in the United States, producing a wide range of recombinant proteins. I wasn’t there, but from what I hear, the biotech revolution was really something.
The immunogenicity problem. Things were going along great until the very same drugs that revolutionized medicine started causing problems in patients. That problem is now called “immunogenicity”. What does that mean? Well, It turned out that it wasn’t so simple to put proteins into human bodies, even if the proteins were very similar to, if not identical to human proteins [[i]]. To those of us working in vaccine research, the concept that proteins would induce immune responses was not a big surprise, but it was interesting to see that immunogenicity could even develop to fully human proteins, with disastrous results (see the story of Erythropoietin and aplastic anemia here).
What’s the source of the problem? Well, some would say that the problem relates to aggregation of the proteins, other say that it’s due to contamination, and still others focus on T cell epitopes as the drivers of immune response. Like anything in science, it’s probably due to a combination of all three. Like vaccines (which are also usually contain proteins), antibodies and other protein therapeutics induce anti-drug antibodies (ADA), which can become a significant limitation to the repeated use of the drug in the clinic [[ii], [iii]].
Immunogenicity. Through a process of “humanization” of monoclonal antibody drugs, the immunogenicity problem has been reduced, but it has not disappeared, and has now spawned an entire industry of its own, and “immunogenicity affinity groups” have developed in a whole range of industry organizations (think AAPS, and European Immunogenicity Platform, among others). In one relatively recent study, anti-drug antibodies developed in 54% of patients following treatment with Campath, a humanized anti-T cell antibody [[iv]]. Well-known antibodies such as infliximab also induce immune responses [[v]]. Thus, the process of humanization does not always lead to a solution for the problem of immunogenicity.
Prediction of immunogenicity is currently an active area of biotechnology research, and we’ve been participating in that area. Please see our information here, and if you wish, read our articles about predicting immunogenicity here: doi:10.1016/j.it.2007.07.011 , doi:10.1016/j.addr.2009.07.001. We use the EpiVax “ISPRI” immunogenicity screening toolkit, which was designed for rapid screening of antibody sequences for immunogenic potential. The best thing about that toolkit (a completely unique feature) is its ability to rank proteins for potential immunogenicity – one against another, or against well-known immunogens, and for its inclusion of an adjustment for Tregitopes, the natural Treg epitopes that are contained within most immunoglobulins. The ISPRI website identified those automatically whenever a protein is uploaded into the ISPRI Database. We’re really proud of the tools that we’ve built for immunogenicity screening over the past few years, and we continue to refine them as we learn new things about immunogenicity predictions in every project we take on.
Deimmunization. One approach to immunogenicity has been applied with success is to identify T cell epitopes, the drivers of immunogenicity, and to remove them. We have mapped and modified proteins in order to reduce HLA binding in the context of (1) botulinum neurotoxin type A, (2) a different bacterial toxin and (3) a monoclonal antibody (names omitted for reasons of commercial confidentiality). Epitope modification has also been applied to other proteins in studies performed by researchers at BioVation [[vi]], Epimmune [[vii]], Genencor [[viii]], EpiVax [[ix]] and others, using a range of different approaches [[x]].
The immunomodulation revolution. The good news is that there are some natural means of controlling anti-drug responses, by adapting natural tolerogenic responses (natural tolerance) and of inducing tolerance (adaptive tolerance) [[xi]]. A few years ago, we found the body’s natural “off switch”, which are peptide sequences that induce Tregs to respond [[xii]] and may lead to adaptive tolerance: Tregitopes. To make a long story short, we believe that the next revolution in biotechnology is to learn how to make the body adapt to the proteins we put in it, so that it no longer reacts (the protein is deimmunized) or it adapts (the protein is tolerogenic). Time to stop dancing and start listening: Tolerance is the new solution to the immunogenicity problem.
T cells come in two flavors. We now know that naïve T cells can differentiate into regulatory or effector phenotypes, and that regulatory T cells control inflammation, turning off the immune response when it is not needed. EpiVax has identified a set of natural, human regulatory T cell epitopes (“Tregitopes”) that trigger ‘natural’ Treg cells. In short – the Tregitopes turn on natural Tregs, which then cause a shift to tolerance, leading to suppression of immune response in an antigen-specific manner. Validation of the Tregitope discovery has taken place in collaborating laboratories at Harvard Medical School, Childrens’ Hospital of Philadelphia, and University of Maryland. More about Tregitopes can be found on our pipeline page. They are a hot topic – discovery of Tregitopes was celebrated by AAPS in the annual “Innovation Award” (http://tinyurl.com/EpiVax-AAPS-Award), in recognition of the importance of the Tregitope discovery for Biotechnology as a whole.
The immunomodulation revolution. Thus we have proposed a relatively novel approach to reducing the immunogenicity of protein therapeutics. Rather than modify immunogenic T-cell epitopes, we are now adding natural, human, regulatory T-cell epitopes to the antibody sequences to induce immuno-suppression. Preliminary studies have shown that the addition of Tregitopes dampens immune responses to pro-inflammatory antigens, and that adaptively tolerant (and antigen-specific) Tregs are induced by delivery of Tregitopes, demonstrating that we are well positioned to pull together the concepts of immune regulation and sequence modification to develop tolerogenic proteins.
What’s old is new. Yes, bellbottoms, platform shoes, headbands, incense are back. Even protesting the war is back. But something new is going on in protein therapeutics. It’s time to pay attention to a new revolution – the revolution of immunomodulation. As it turns out, the body has ways to suppress immunogenicity (regulatory T cells), and we found a way to harness Tregs. The Tregitope “off switch” appears to be a pretty good trick. I wasn’t present at the first revolution, but I’m planning on participating in this one, and I believe that this particular dance, between immunogenicity and tolerance, will be one that will lead to much better medicines for human use.
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[iii] Isaacs JD, Manna VK, Rapson N, Bulpitt KJ, Hazleman BL, Matteson EL, St Clair EW, Schnitzer TJ, Johnston JM. CAMPATH-1H in rheumatoid arthritis–an intravenous dose-ranging study. Br J Rheumatol. 1996 Mar;35(3):231-40.
[iv] Matteson EL, Yocum DE, St Clair EW, Achkar AA, Thakor MS, Jacobs MR, Hays AE, Heitman CK, Johnston JM. Treatment of active refractory rheumatoid arthritis with humanized monoclonal antibody CAMPATH-1H administered by daily subcutaneous injection. Arthritis Rheum. 1995 Sep;38(9):1187-93.
[v]. Baert, F, Norman, M., et al. Influence of Immunogenicity on the Long-Term Efficacy of Infliximab in Crohn’s Disease, Engl J Med 2003; 348:601-608February 13, 2003. http://www.nejm.org/doi/full/10.1056/NEJMoa020888?keytype2=tf_ipsecsha&ijkey=9e4c4c8845b3977c2afd1f320b31735460716acd.
[vi]. Hellendoorn K, Jones T, Watkins J, Baker M, Hamilton A and Carr F, Limiting the risk of immunogenicity by identification and removal of T-cell epitopes (DeImmunisation™), Association for Immunotherapy of Cancer: Cancer Immunotherapy – 2nd Annual Meeting Mainz, Germany. 6–7 May 2004 Cancer Cell International 2004, 4(Suppl 1):S20
[vii]. Tangri S, Mothe BR, Eisenbraun J, Sidney J, Southwood S, Briggs K, Zinckgraf J, Bilsel P, Newman M, Chesnut R, Licalsi C, Sette A. Rationally engineered therapeutic proteins with reduced immunogenicity. J Immunol. 2005 Mar 15;174(6):3187-96.
[viii]. Yeung VP, Chang J, Miller J, Barnett C, Stickler M, Harding FA. Elimination of an immunodominant CD4+ T cell epitope in human IFN-beta does not result in an in vivo response directed at the subdominant epitope. J Immunol. 2004 Jun 1;172(11):6658-65.
[ix]. De Groot AS, Knopf PM, Martin W. De-immunization of therapeutic proteins by T cell epitope modification. Mire-Sluis, A. Ed. State of the Art Analytical Methods for the Characterization of Biological Products and Assessment of Comparabilitiy. Dev. Biol. Basel, Karger, 2005. vol 122. pp 137-160.
[x]. Warmerdam PA, Plaisance S, Vanderlick K, Vandervoort P, Brepoels K, Collen D, De Maeyer M. Elimination of a human T-cell region in staphylokinase by T-cell screening and computer modeling. Thromb Haemost. 2002 Apr;87(4):666-73.
[xi]. Bluestone JA, and Abbas AK., Natural versus adaptive regulatory T cells. Nat Rev Immunol. 2003;3:253-257.
[xii] De Groot A.S., L. Moise, J.A. McMurry, Erik Wambre, Laurence Van Overvelt, Philippe
Moingeon, W. Scott, W. Martin, Activation of Natural Regulatory T cells by IgG Fc-derived Peptide “Tregitopes”. Blood, 2008,112: 3303. http://tinyurl.com/ASDeGroot-Blood-2008
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