{"id":7177,"date":"2026-05-13T09:05:57","date_gmt":"2026-05-13T15:05:57","guid":{"rendered":"https:\/\/allphasepharma.com\/dir\/?p=7177"},"modified":"2026-05-13T09:08:11","modified_gmt":"2026-05-13T15:08:11","slug":"off-target-antibodies","status":"publish","type":"post","link":"https:\/\/allphasepharma.com\/dir\/2026\/05\/13\/7177\/off-target-antibodies\/","title":{"rendered":"OFF-TARGET ANTIBODIES"},"content":{"rendered":"\n
\"\"<\/a><\/figure>\n\n\n\n

Quick: What do you associate with the abbreviation \u2018TCR\u2019?  Does your immunology-trained mind automatically default to \u2018T-cell receptor\u2019?  Or is your first guess \u2018Tissue Cross Reactivity?  Our neural networks can deal with ambivalence and will make the right associations, eventually.  Language is imprecise by design and allows for wobble.<\/p>\n\n\n\n

Things become really confusing when authors refer to \u201cTCR cross-reactivity\u201d. Again, neural networks to the rescue \u2013 we implicitly understand what\u2019s meant.<\/p>\n\n\n\n

This blog is about TCR = tissue cross reactivity. The term relates to the fact that antibodies sometimes lack precision targeting a certain receptor.  In some cases, there is a variable amount of give, a certain degeneracy, a bit of promiscuity.  A lack of singularity, if you will.<\/p>\n\n\n\n

\"\"<\/a><\/figure>\n\n\n\n

Figure 1: From: Trier N.  Ref. [1]<\/a><\/p>\n\n\n\n

A recent article by Dai et al. makes for interesting reading.[2]<\/a>  It describes a rapid technique to characterize the binding of a large number of mAbs in clinical development or approved  <\/del>(N=174, to be exact) to over 6,000 (!) extracellular proteins.  They found cross-reactivity (or off-target binding) with 28% of them. <\/p>\n\n\n\n

Author Aaron Ring and the Adimab team are immunology experts with deep understanding of mAb technology.  They know all about mAb specificity and\/or lack thereof, often called polyreactivity or polyspecificity.  This observed high frequency of off-target engagement came probably as a surprise; the article concludes with the recommendation to test for target promiscuity early in drug development.<\/p>\n\n\n\n

Immunology is the science of the body\u2019s ability to distinguish self from non-self, the recognition of minute differences in tissue properties, the ability to respond to new antigenic markers presented by invading microorganisms or the neoantigens released at times of tissue injury (think DRESS syndrome).  The positive and negative selection process of T-cells is a marvelous process that seems to work extremely well, decreasing the odds of developing an autoimmune disease during lifetime.  Our B- and T-cell reservoirs have developed a sophisticated defense system which is both highly conserved and highly specific while being flexible enough to respond to almost any foreign signal.<\/p>\n\n\n\n

TCR testing is already part of the routine preclinical testing process required by Regulators worldwide.  Off-target toxicity or lack of selectivity rarely rises to a level of clinical concern with mAbs, the predominant class of biologicals.  This is quite remarkable: mAbs are considered much safer than NCEs, partly because of their pin-point efficacy.  This property of antibody B-cells maturation and antibody specificity is quite amazing, and the same holds true for mAbs produced in ex-vivo in bioreactors.  Hence, we take target specificity as a given and are mainly concerned about ADAs.  Indeed, package inserts for biologicals do not even mention TCR test results.<\/p>\n\n\n\n

This is for good reasons.  TCR testing in-vitro <\/em>on human tissues is problematic as non-specific binding may be misleading.  Therefore, preclinical TCR testing is considered a screening test, with caveats attached.  It may predict a problem for development but should be seen as just one piece of a jigsaw puzzle, in need of confirmation, to be evaluated in context with other findings.  At least that was the opinion of a Consortium of Experts from industry, published in 2010.[3]<\/a>   However, time does not stand still, and much has been learned since then. <\/p>\n\n\n\n

Cunningham et al.  provided a list of examples from mAb development when cross-reactivity was clinically relevant.  While changes to the PK profile can be dealt with, more concerning is off-target toxicity.[4]<\/a>  The authors make the point that testing procedures for cross-reactivity are incomplete and lack standardization.  In their words, a  \u201cdeep, systematic study of antibody specificity is lacking\u201d.<\/p>\n\n\n\n

A slightly different view is presented by Trier et al.[1]<\/a>  The authors feel that antigenic mimicry is not the underlying cause of many autoimmune diseases.  They make the point that many times cross-reactive antibodies are clinically silent and do not contribute to the development of autoimmune diseases.<\/p>\n\n\n\n

Are we too complacent when results turn positive on TCR testing?  Should the Dai study make us rethink our approach to TCR testing?  What exactly should one do with a positive finding on high-sensitivity TCR testing?  There is no threshold or cut-off as to when to call a signal relevant.  The more sensitive the methodology, the more cross-reactivity is to be expected. <\/p>\n\n\n\n

This situation reminds us of the early days of PCR testing for Legionella on bronchial samples.  Just about every test came back positive, while culture and antigen tests remained negative.  Hardly anyone had Legionellosis and required specific treatment. Clearly, an overly sensitive test resulted in large numbers of false-positive results. <\/p>\n\n\n\n

There are no easy answers here.\u00a0 More testing is not always helpful, if we don\u2019t know what to do with the results.\u00a0 As long as we cannot even interpret the results of existing test protocols, having a more sensitive method is unlikely to eliminate ambiguity. <\/p>\n\n\n\n

Therefore, our approach to TCR testing has not changed.\u00a0<\/p>\n\n\n\n

Since the Consortium published its recommendations in 2010, almost 2 decades of biological research have gone by.  This fact alone should justify a renewed look at current TCR practices as the field is so dynamic.<\/p>\n\n\n\n

\n\n\n\n
ABBREVIATIONS<\/strong>\nNCE\tnew chemical entity\nTCR\tT-cell receptor\nTCR\tTissue cross-reactivity\nDRESS\tDrug Reaction with Eosinophilia and Systemic Symptoms\nADA\tantidrug antibody\n\n\nREFERENCES<\/strong>\n[1]<\/a> Trier N.  Antibody Cross-Reactivity in Auto-Immune Diseases. Int. J. Mol. Sci. 2023, 24, 13609\n[2]<\/a> Dai Y.  Off-target reactivity in clinical monoclonal antibodies, Structure 34:1; 2026\n[3]<\/a> Leach M.  Use of Tissue Cross-reactivity Studies in the Development of Antibody-based iopharmaceuticals: History, Experience, Methodology, and Future Directions.  Toxicologic Pathology, 38: 1138-1166\n[4]<\/a> Cunningham O.  Polyreactivity and polyspecificity in therapeutic antibody development: risk factors for failure in preclinical and clinical development campaigns.  mAbs, 13:1, 1999195<\/pre>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Quick: What do you associate with the abbreviation \u2018TCR\u2019?  Does your immunology-trained mind automatically default to \u2018T-cell receptor\u2019?  Or is your first guess \u2018Tissue Cross Reactivity?  Our neural networks can deal with ambivalence and will make the right associations, eventually.  Language is imprecise by design and allows for wobble. Things Continue reading   OFF-TARGET ANTIBODIES<\/span>→<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":7170,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[227,3,18],"tags":[2659,1271,2657,2658,1583,2655,2656],"class_list":["post-7177","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-recent_literature","category-the_news","category-the_viewpoint","tag-adimab","tag-allphase-pharma-consulting","tag-antibody-polyreactivity","tag-dress-syndrome","tag-harald-reinhart","tag-tcr","tag-tissue-cross-reactivity"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2026\/05\/HR_TCR.slider.jpg?fit=640%2C180&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p4KWFr-1RL","jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":751,"url":"https:\/\/allphasepharma.com\/dir\/2014\/08\/23\/751\/not-so-boring-boron-containing-antibiotics-create-a-stir\/","url_meta":{"origin":7177,"position":0},"title":"Not So Boring: \u00a0Boron-Containing Antibiotics Create a Stir","author":"Harald","date":"August 23, 2014","format":false,"excerpt":"Why are there so few boron-containing drugs on the market? \u00a0The cancer drug bortezumib (Velcade\u00ae) may be the only better-known drug on the market with a boron atom in its structure.[1]\u00a0 Among antibiotics, there is Kerydin\u2122 (tavaborole), an approved topical solution for the treatment of onychomycosis caused by Trichophyton but\u2026","rel":"","context":"In "The News"","block_context":{"text":"The News","link":"https:\/\/allphasepharma.com\/dir\/category\/the_news\/"},"img":{"alt_text":"Novel -lactamase inhibitors: a therapeutic hope against the scou","src":"https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2014\/08\/fmicb-04-00392-g003-e1408842545171.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":4599,"url":"https:\/\/allphasepharma.com\/dir\/2025\/06\/29\/4599\/pk-pd-of-biologicals\/","url_meta":{"origin":7177,"position":1},"title":"PK\/PD of BIOLOGICALS","author":"Harald","date":"June 29, 2025","format":false,"excerpt":"Sometimes we come across an article we wish we had read earlier.\u00a0 This was the case with the publication by Zhao and colleagues[1].\u00a0 The article, now more than 12 years old, was written in the \u2018early\u2019 days of biological drug development, after the first wave of mAbs had already been\u2026","rel":"","context":"In "Did you know...?"","block_context":{"text":"Did you know...?","link":"https:\/\/allphasepharma.com\/dir\/category\/interesting_facts\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2025\/06\/PKPD-for-Biologicals.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2025\/06\/PKPD-for-Biologicals.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2025\/06\/PKPD-for-Biologicals.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":1287,"url":"https:\/\/allphasepharma.com\/dir\/2015\/03\/05\/1287\/the-pneumococcus-prominent-microbiologists-contributions-and-cross-connections\/","url_meta":{"origin":7177,"position":2},"title":"The Pneumococcus, Prominent Microbiologists, Contributions and Cross-Connections","author":"Harald","date":"March 5, 2015","format":false,"excerpt":"\u2018He who knows syphilis knows medicine\u2019 goes the saying. In a similar way this adage could be applied to the Pneumococcus, aka Streptococcus pneumoniae, Diplococcus pneumoniae or Diplococcus lanceolatus by saying \u201cHe who knows S. pneumoniae knows microbiology\u201d. Many \u2018big names\u2019 studied the\u00a0organism. \u00a0Their work on the Pneumococcus led to\u2026","rel":"","context":"In "Did you know...?"","block_context":{"text":"Did you know...?","link":"https:\/\/allphasepharma.com\/dir\/category\/interesting_facts\/"},"img":{"alt_text":"PNEUMOCOCCUS copy","src":"https:\/\/i0.wp.com\/allphasepharma.com\/dir\/wp-content\/uploads\/2015\/03\/PNEUMOCOCCUS-copy.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":439,"url":"https:\/\/allphasepharma.com\/dir\/2014\/07\/02\/439\/adequate-penetration-of-daptomycin-into-bone-tissue\/","url_meta":{"origin":7177,"position":3},"title":"Adequate Penetration of Daptomycin Into Bone Tissue","author":"Harald","date":"July 2, 2014","format":false,"excerpt":"After a single high dose of (8 or 10 mg\/kg BW) of daptomycin IV, bone levels were measured in plasma and trabecular bone obtained during hip or knee surgery of 16 patients.[1] At the time of surgery, mean concentrations in plasma and 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