Choosing a CRO for Tissue Cross-Reactivity Studies: 10 questions to ask before you commit
How do experienced sponsors evaluate specialist tissue cross-reactivity (TCR) providers, and what questions should you ask when choosing a contract research organisation (CRO)?
Tissue cross-reactivity (TCR) studies are a critical part of the preclinical safety assessment of therapeutic antibodies and other targeted biologics. By evaluating where a therapeutic binds across a broad range of normal human tissues, these studies help identify potential off-target binding and also previously unknown sites of on-target binding before a candidate progresses into clinical development.
Because TCR studies form part of the evidence supporting an Investigational New Drug (IND) filing, the quality of the scientific data, pathology interpretation and supporting documentation can have a direct impact on regulatory confidence. A poorly designed or executed study may lead to additional questions, repeat work and programme delays, increasing both cost and development timelines.
Choosing the right CRO partner is not primarily a procurement decision; it is a scientific and regulatory risk decision. Below is the checklist we would use ourselves if we were on the sponsor side of this evaluation.
1. Track record
Ask about the CRO’s experience and the number of Good Laboratory Practice (GLP)-TCR studies they have performed. A CRO with a strong track record should be able to speak to this, even where specifics must stay anonymised for confidentiality reasons.
2. GLP compliance history
Ask for the CRO’s recent GLP inspection history and how any findings were resolved. This is public-adjacent information in most jurisdictions and a CRO confident in its compliance record will not be reluctant to discuss it.
Pay attention not just to whether findings occurred, but how quickly and thoroughly they were closed out. A strong GLP inspection history demonstrates that quality systems are embedded in day-to-day laboratory practice rather than existing only on paper. Rather than simply asking whether inspections have taken place, sponsors should understand what observations were raised, how they were resolved and whether corrective actions have been sustained over time.
3. Tissue source and quality
Review the CRO's tissue inventory alongside the ethical approvals and consent documentation supporting it. Before committing to a study, you should understand:
Whether tissue is sourced under a documented, auditable framework with a clear chain of custody
Whether the tissue samples are ‘true normal.’ Some cohort samples, while pathologically determined as normal, could be collected as adjacent to a cancer resection. It can be argued by the regulator that these specimens are not strictly normal, non-diseased tissue.
Whether the CRO maintains its own well-characterised biobank, or sources tissue reactively per study – this can influence timelines as certain human tissue samples required under FDA and EMA guidelines can be very difficult and time consuming to source.
Additionally, the quality of the tissues used is of the utmost importance. The tissues must retain antigenicity and exhibit good morphological preservation to allow adequate interpretation of staining patterns. The CRO should recommend incorporating confirmation of tissue antigenicity into the GLP study, as testing prior to the study does not guarantee antigenicity once the tissue has been sectioned onto glass slides.
4. Assay development rigor
Before GLP work begins, your antibody needs a robust immunohistochemistry (IHC) protocol: concentration range-finding, appropriate isotype and blocking controls, and positive and negative control tissues (or cell lines) with known target expression. A favourable dataset for a TCR study is a broadly negative result, representing no off-target binding. Therefore, it is critical to validate that the assay is specific and robust to avoid false negative results in the TCR study.
Ask how the CRO handles fit-for-purpose validation, and specifically how they've handled your antibody's format before - conjugated formats such as antibody-drug conjugates (ADCs), T-cell engagers, scFv fragments or bi- and tri-specifics require assay development and control approaches that not every lab has direct experience with. Is the CRO competent in conducting IHC across different sample types, formats and therapeutic modalities, and what levels of expertise does the team have when optimising IHC protocols? Your data are only as good as the scientific robustness of the IHC protocol your CRO develops.
5. Strategy for complex molecules
If you have a complex therapeutic (for example, multi-specific binders, T-cell engagers or B-cell engagers) explore with the CRO what they would recommend for validating or attributing any observed tissue binding with a specific feature of your molecule.
If your biotherapeutics are designed against non-human targets (for example in infectious disease) ask the CRO whether they have experience in development of assays for such targets in human tissue and to exemplify how they approach rigorous assay development for atypical or non-human targets.
6. Integrated TMA-to-GLP capability
Prior to commencing a full GLP TCR study, it is often cost effective to perform a study using tissue microarrays (TMAs). This can help triage potential therapeutic candidates and identify potential binding liabilities before embarking on the GLP study. Since the TMA screen is often used to inform the resulting GLP study, running both under a single CRO avoids technology transfer risk and cost, and keeps a single point of accountability for both assay execution and pathology interpretation.
If a CRO only offers non-GLP TCR, ask directly how they manage handoff to a second lab and who owns interpretation continuity. It will de-risk your study significantly if the CRO has expertise in both non-GLP TMA TCR and full GLP studies as once the IHC assay is developed and finalised, it can be applied to either or both study formats.
7. Pathologist credentials
Ask about the credentials of the specific pathologist who will review and sign your study. This should include qualifications and whether they are experienced with GLP studies. TCR interpretation is a specialised skill distinct from general histopathology, and the quality of that single sign-off has an outsized effect on how your submission will be received.
8. Turnaround and capacity
Once the final IHC assay conditions are finalised, TMA screening should typically be delivered in a matter of weeks. Before then, confirm GLP study slot availability and commitment against your actual IND timeline. Capacity constraints at busy CROs are one of the more common causes of unplanned schedule slippage late in a programme. To expedite or manage timelines around availability of the GLP batch of your therapeutic molecule, explore the CRO’s strategy and ability for starting the assay development phase, and non-GLP phase if required, early with a research grade batch of your therapeutic molecule.
9. Communication during interim findings
Understand how the CRO manages unexpected on- or off-target signals identified during TMA screening. A strong partner will proactively flag and discuss the biological significance of a finding with you before you commit to GLP spend, rather than simply delivering a report at the end of the process.
10. Cost transparency
Request an itemised quote that separates tissue procurement, assay development and verification, TMA screening, and the full GLP study. Bundled, opaque pricing makes it difficult to compare CROs on a like-for-like basis and can hide where the real costs and risk sit.
A practical first step
Choosing a TCR CRO is ultimately about confidence. Sponsors should be looking for evidence that the right partner can generate scientifically robust, regulator-ready data while reducing programme risk at every stage, from early TMA screening through to GLP reporting. Asking the right questions before a study begins is one of the simplest ways to avoid delays, unnecessary costs and repeated work later in development.
At Pharmagene®, these are the same questions we encourage prospective sponsors to ask us. We believe transparency is fundamental to building confidence, which is why we are happy to discuss our GLP inspection history, pathologist credentials, tissue sourcing and governance, assay development approach, experience with multiple therapeutic modalities and integrated TMA-to-GLP workflow during the earliest stages of project planning.
Our aim is not simply to deliver a TCR study, but to become a trusted scientific partner throughout the process, helping you to de-risk your programme, make informed decisions early, and generate robust data that support successful regulatory submissions.
For sponsors working with a new antibody or evaluating a new CRO relationship, a small feasibility or assay optimisation study can be a valuable first step. It provides an opportunity to assess antibody performance, optimise the IHC protocol where required, and experience first-hand how the CRO communicates, solves problems and supports your programme before committing to a full GLP TCR study.
