Therapeutics
Ipilimumab experience autoimmune-like symp- toms and require close monitoring throughout the treatment regime9.
Assessing antibody binding using tissue cross-reactivity studies Researchers have adapted to this challenge by developing novel assays and approaches to acceler- ate their understanding of the performance of immunotherapies. One such approach is the tissue cross-reactivity study, which provides valuable insights into the likely in vivo response of a novel antibody or antibody-like molecular
structure
prior to commencing expensive clinical trials. Such studies enable a detailed assessment in vitro of the binding of a test article across a panel of 33 or more organs and across a variety of species. By considering the candidate’s profile of on- and off- target binding, scientists gain an understanding of the propensity of the structure to bind, with high specificity, to target healthy organs in which bind- ing is undesired. In turn, this increases confidence in the candidate’s performance, provides evidence- based safety and risk data, and accelerates its advance into clinical trials.
There is no prescriptive structure for the design of a tissue cross-reactivity study, with specific study goals dictating the overall design. Regulatory requirements will dictate whether the study requires a panel of full-face tissues or whether a tis- sue micro array (which comprises a single slide with multiple cores of tissue from the identified 33 organ normal tissue panel) can be used. A regula- tory-compliant GLP tissue cross-reactivity study can be split into two distinct phases; a non-GLP immunohistochemistry (IHC) method develop- ment and validation phase, followed by a GLP tis- sue cross-reactivity phase. The non-GLP phase involves full and extensive IHC method develop- ment including testing and optimising parameters for test article titration, antigen retrieval, blocking, amplification and detection reagents. This is fol- lowed by an assessment of specificity, linearity, reproducibility and a background staining assess- ment on a limited tissue panel from a single donor. An experienced study pathologist is often required to review the validation slides and final optimal method to add a seal of approval before proceed- ing into the GLP tissue cross-reactivity phase. Once a robust IHC method is validated, the method is applied across a panel of at least 33 tis- sues. Guidelines from the FDA recommend a panel of 33 tissues from three unrelated adult donors. For researchers seeking to gain regulatory approval in multiple jurisdictions, it is advised to assess
Drug Discovery World Summer 2017
binding across an extended panel of 38 tissues, covering both FDA and EMA recommendations7. Although these tissue panels are recommended, additional tissues from target organs specific to the test article can be included depending on particular toxicity concerns and the mode of action. At least two concentrations of the test article are recom- mended, while three concentrations (the optimum concentration identified in the validation phase, and also a sub-optimal and supra-optimal concen- tration) provides further information and ensures tissues of varying target expression can be assessed. Early preclinical studies may employ a non-GLP study utilising tissue micro arrays (TMAs) contain- ing an FDA-recommended tissue panel. This allows researchers to gain an insight into on-off target binding at an early stage, and can help direct development programmes to address undesired off-target binding. Furthermore, the use of TMAs is a considerably more economic approach for early preclinical studies, and is becoming increas- ingly popular to assess the safety profile early on in the development pipeline. However, for regulatory submission and advance into clinical trials, a GLP study comprising a full tissue panel is required. Several important elements should be considered when conducting GLP-compliant tissue cross-reac- tivity studies. Firstly, the experience of the scien- tists in performing tissue cross-reactivity assays with novel test articles, which often require exten- sive immunohistochemistry protocol development and validation. Some biopharmaceutical compa- nies choose to subcontract GLP tissue cross-reac- tivity studies to specialist contract research organi- sations, in order to gain access to their expertise in conducting these specialist studies, and to ensure robust data suitable for regulatory submission. Secondly, the sourcing and quality of the tissue panel used within the study. It is important to ensure that the frozen tissue is sourced with fully- informed patient consent, and the tissues are han- dled carefully prior to freezing to ensure preserva- tion of antigenicity and morphology. Since all data output is reliant on the expression of the test article in the tissue sections, it is critical that the tissue panel is of a high quality with no areas of necrosis or autolysis on any tissue. One or two tissue integrity biomarkers can be included as part of the tissue cross-reactivity study to demonstrate that the study materials meet these stringent quality cri- teria. A single section from each tissue is stained with routine tissue architecture biomarkers such as vimentin or cytokeratin, or as a multiplexed dual stain, which are complementary and provide broad staining over the majority of tissue architecture.
References 1World Health Organisation (2017). Cancer Fact Sheet. Accessed 22 May 2017:
http://www.who.int/mediacentr e/factsheets/fs297/en/. 2 Global data (2016). Immuno- Oncology Strategic Insight: Multi-indication and Market Size Analysis. Accessed 22 May 2017:
https://www.globaldata.com/st ore/report/gdhc057poa-- immuno-oncology-strategic- insight-multi-indication-and- market-size-analysis/. 3 Morrissey, KM et al (2016). Immunotherapy and Novel Combinations in Oncology: Current Landscape, Challenges and Opportunities. Clin Transl Sci 9: 89-104. 4 Kamta, J et al (2017). Advancing Cancer Therapy with Present and Emerging Immuno-Oncology Approaches. Frontiers in Oncology. 7: 64. 5 Rosenberg, SA (2014). IL-2: The First Effective Immunotherapy for Human Cancer. Immunol, 192 (12) 5451-5458. 6 Stroncek, DF (2017). Systematic evaluation of immune regulation and modulation. Journal of ImmunoTherapy of Cancer, 5:21. 7 Leach, MW et al (2010). Use of Tissue Cross-reactivity Studies in the Development of Antibody-based Biopharmaceuticals: History, Experience, Methodology, and Future Directions. Toxicologic Pathology, 38: 1138-1166. 8 Antonia, SJ et al (2014). Immuno-oncology Combinations: A Review of Clinical Experience and Future Prospects. Clin Cancer Res. 20(24). 9Weber, JS et al (2015). Toxicities of Immunotherapy for the Practitioner. Journal of Clinical Oncology 33(18). 10 Kontermann, RE, Brinkmann, U (2015). Bispecific antibodies. Drug Discovery Today 20 (7): 838-847.
Continued on page 54 53
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72