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What is Human Tissue Testing?

Drug Discovery / 14 October 2021 / Roland Linder

What is human tissue testing? To understand this unique area of research, you must first consider how drugs are tested and developed.

When a drug leaves the lab-stage and is tested in animals, the response does not always match that seen in humans. Diseases such as cancer or diabetes can be very similar in animals, but there are differences. Human tissue research can help by looking at the effects of drugs in donated bits of tissue (e.g. skin, cancer biopsies, blood) to check possible side effects before testing in human beings.

Hundreds of researchers across the globe are using human tissue research to improve the way drugs are tested and developed - one of them is Dr David Bunton. I interviewed Dr David Bunton below to learn about the past, present and future of human tissue testing. You can listen to the full interview here, or read on to find out more.


Would you mind telling us a little bit about yourself?

I'm the CEO at REPROCELL Europe based in Glasgow, UK. My background is in pharmacology and physiology and I was a lecturer in Physiology at Glasgow Caledonian University. In 2002 I spun out a life science company called Biopta, which was acquired by REPROCELL, a Japanese company in 2015. I'm still with REPROCELL today and head their European operations.


What exactly does REPROCELL do?

REPROCELL is a life science company that provides products and services - primarily in regenerative medicine and drug discovery - focused around human data, human tissue systems, and human-engineered tissue models.

We were one of the first companies to commercialize a particular type of stem cell called "induced pluripotent stem cells" which are taken from adult tissue and reprogrammed back into stem cells. It's been a very successful Japanese company in that field. REPROCELL have acquired a number of complementary businesses in the past five or six years around the stem cell and human tissue research space - all linked by a common theme of human data and human-relevant test systems.

Our group headquarters are in Yokohama in Japan, but I am based in Glasgow and our products distribution center is in Durham, UK. REPROCELL also has labs in Maryland, USA, and Hyderabad, India. It's a truly global business.


What is human tissue research?

Human tissue research is a broad area covering the use of human biospecimens that have been donated for research by patients. Its most common use is in drug discovery and development - either in academia or an industry - to try and base decisions about the safety and efficacy of drugs for human use using human systems. It's become a very common area in the past 10-15 years with the advent of precision medicine and the human genome project.

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Where exactly do the tissues come from?

The logistics for collecting biospecimens are key to the whole process. These are extremely precious samples that are donated by patients, so we start with gaining informed consent from the tissue donors.

Donated tissues come from a number of roots, but there are three primary routes - one of which is surgical residual material. Any tissue that's required for diagnostics is, of course, sent for further investigation. But if there's any other tissue available at that point the pathologist will decide if it can be donated to research. The second route is transplant tissue. Again, transplantation is the primary objective with transplant organs, but if for any reason the organs may not be placed for transplant then they can be used for research.

And the third route is biopsy material, where patients or volunteers donate samples. Most of us will be familiar with the idea of a blood sample, but skin and muscle biopsies can also be donated. Over the past year and a half, we've all become familiar with the use of nasal swabs to collect biological samples for COVID testing - these types of samples can also be used for research.

[Interviewer] So let's imagine doing an operation that removes some cancerous tissue - as a patient, I'm happy with that to be shared for medical research. Then it would be one of the sources, right?

That's a very common source: where tissue is being resected anyway and with consent of the patient can be used for other purposes. It's very important that the patient is informed. Usually there's a patient information booklet that explains the uses and the journey that the tissue will go on and also whether it's for commercial or non-commercial research.

[Interviewer] Tell me a little bit about the journey here. Once you donate some of your tissue, at a hospital for example, where does the tissue travel afterward? What's the logistical aspect of it? Where does it go?

Typically for tissue from surgery, it will first go to pathology and through the hands of the team that is diagnosing the treatment options for the patient. At that point, the pathologist will decide whether or not there's any tissue that could be made available for research.

If so, the tissue will be preserved or stored in an appropriate way depending on the purpose of the research: if it's a static study where we don't need to look at function, we're just looking at the structure, then the tissue could be frozen or fixed at that point in time.

However, for many of the studies that we do, we use the tissue fresh to retain the physiological relevance to the behavior of the tissue in the body. So we do as little as possible to the tissue and maintain it in a physiological buffer or culture media, and then transport that to the laboratory as fast as possible so that the functionality is maintained.

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How long do tissues survive in the lab and during transport?

It really varies according to the tissue type, as different tissues have different metabolic rates and sensitivities to being out of the body. Heart tissue, for example, is very active and doesn't survive more than a few hours. Other tissues, such as skin, are less metabolically active so are transported and preserved a little easier. But typically, we're talking about a matter of minutes to hours to get it to the lab and get it into a test system.

It really becomes a 24/7 lab operation to support these types of studies and the companies that have grown in the past 10-15 years are experts in logistics. It's not just the science or the laboratory experiments, but those processes to collect, store, transport the tissue, and maintain it in good condition. Because it's key that the material you have is as close to the starting point in the body; you want it to represent that normal physiology or pathophysiology. In most of our experiments, we will also qualify the tissues at the start to determine whether it's in good enough condition to undergo the experimental protocol.


How willing are people to donate tissues for research?

Patients are extremely supportive of this type of research, whether it's in the commercial or non-commercial sphere. A number of surveys and publications have looked at this area and have determined that over 95% of patients support this type of research.

It's critical that we continue to get the support of the public, but also show the benefits of it; show how medicines can be brought to market quicker and demonstrate safety and efficacy more clearly in patients. I think that precision medicine is one of the ways in which the public is becoming more aware of the need to understand, not only the responses in humans, but how we individually respond to different drugs.

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What research area is human tissue testing used in?

It can be used in many areas. I think the most common use of fresh tissues is in late-stage pre-clinical or lead optimization: where there's a small number of promising drug candidates, and the objective is to try and understand if data from cell-based models or animal models translates to humans. For example, do we see those signaling pathways activated? Do we see some readouts of biomarkers from the tissue that would indicate efficacy or perhaps be useful in showing that there are few side effects?

But we also see many instances where we are asked to investigate clinical problems: troubleshooting of clinical observations where a drug has not been tested sufficiently in human systems, and unexpected safety effects occur in the clinic. And that can be either the regulators or the sponsors of the research who will come back to us and say,

"Can you help to explain this mechanism? We looked at the responses in the cardiovascular system of various animal models and we didn't see any signal, but now we're seeing adverse effects in patients and volunteers."

That's where using human fresh tissues can give mechanistic insights into those effects that may differ between humans and animals.

[Interviewer] So really what you're doing is a last stop before you start a clinical trial before you have human volunteers for the medications. That's where you want to make sure that the animal testing data that you have is doing what it's meant to be doing - as the last safety check, last conviction check, in a sense.

That's the most common application. It's not something that's done in very high throughput because we're taking samples from patients. We're not looking at a high throughput cell-based model - we've got complex intact tissues. But for pharmacology, we can achieve reasonably good throughput for this type of test.

You could be looking at 20 to 30 individual tissues from a single donor, so you can still look at multiple compounds. But you're right, it tends to be late stage. Either lead optimization into pre-clinical safety, or late-stage pre-clinical in general.


What industries are using human tissue research?

The overwhelming use of it is in pharma and biotech, but we've done a number of studies in the agrochemical or medical device area where, again, there may be no suitable model in cells or animals that are that reflect what's what we're trying to assess. For example, assessing risk of a particular chemical or pesticide on reproductive health, or recreating the physical characteristics of a blood vessel in the lab which may be important for certain medical devices such as stents. So there are a number of uses but the overwhelming one is in drug discovery and that's both for small molecule traditional small molecules and also for biologicals.

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What is the main need that human tissue research addresses?

I think the main need is that, despite all our advances and improvements in science, there is still a problem with translation from pre-clinical to clinical in particular our prediction of efficacy. Over the past 20 years, I would say 50-60% of our studies have been some demonstration of efficacy, or proof-of-concept, in human disease tissue from the target patient population.

It's also about validating the drug target that has a likely benefit to patients, so that it's used properly, should reduce greatly clinical attrition rates. That's where we estimate we've saved clients huge sums from the many hundreds of drug candidates that have gone through our lab: at these later stages. I would say the biggest need is that serious problem that still exists of clinical attrition.

[Interviewer] You want to prevent the kind of issue where, let's say you're in a phase two clinical trial and you realize, "Okay, hang on, this isn't actually working as intended. All our previous lab data that we have, all our animal data was completely out, and here we are - it's not actually working as we thought it would."

That's right, and that's still all too common. Unfortunately, depending on the therapeutic area, it can be one in ten compounds that fail, or even as many as one in five. It's very difficult to succeed; we're seeing 90-95% failure rates in some areas. And while everyone knows that it's a problem, no one would say that human tissue on its own is going to address all those issues. It's far too complex and there's too many factors involved in that translation.

But certainly there is a focus generally on more translational models - not just through fresh tissues - but also through the use of frozen tissues, stem cell models, complex 3D tissue models, and organ-on-a-chip technologies. These are all part of a solution which is helping to improve our understanding of the complex human biology.

[Interviewer] You're basically saying, "Look we have another data point that's actually quite important - hopefully it will lead us to the right conclusions." But you can't guarantee that of course because, let's be honest, human bodies can be a little bit more complex than we sometimes think.

Exactly, it's reducing risk at each stage. There can be no guarantee of success - it's more about reducing risk at every step.


What is the most common therapeutic areas that are investigated using human tissues?

Much of this research originated in cancer, using tumor samples to characterize the differences between cancer types, and to look at molecular biology. That formed the foundation for a lot of tissue networks that allowed access to samples and remains a key area for drug discovery.

Today, human tissue research covers many different types of therapies - from cardiovascular disease, where we started (I was looking at heart failure hypertension etc.) to respiratory diseases such as asthma and COPD. Over the past 10 years, probably the most rapidly growing field has been in autoimmune disorders: psoriasis, atopic dermatitis, and inflammatory bowel diseases.

Crohn's disease and ulcerative colitis are on the increase, and there's a lot of focus in pharma on biologicals and preventing disease progression via early intervention. The key is to get the relevant tissue type fresh and use that as a model of drug effectiveness. That's one of the powers of the human tissue approach.

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Can you tell us how this type of research compares to other types of research?

There are there strengths and weaknesses to every approach, and human tissue is no different. When we started out the company in the early 2000s, there were many companies who embraced this approach and others who were more reluctant. It was quite different from traditional cell-based or animal approaches, which tend to focus on reproducibility and robustness of the assay more than the translation to humans.

There is no getting away from the fact that the responses in human tissues from 10 or 20 donors will be more variable than a comparable study in 20 rats where they're all inbred or outbred and therefore similar in their responses. It used to be that was seen as a weakness of human tissues but increasingly that's now understood as being one of the strengths.

That variation in response is what happens in the clinical trials and is now understood as a key reason why promising drugs sometimes fail; they may be benefiting a section of the target patient population in the clinical study, but other patients see little or no response.

Using human fresh tissue, we're trying to understand the reasons for that variation between individuals by looking at genetics, clinical history, and medical history. These are all key factors in understanding variation in drug response earlier in drug discovery, design clinical trials differently, and have more confidence that the target patient population is correct. That's one of the key benefits and it's really a cost benefit analysis as to how early that is done in the drug discovery process.

Having a "fail fast, fail early" approach has been shown to have huge cost savings downstream, because costs increase the further you go through the clinical trials. And having that increased understanding at the pre-clinical stage, even if it means more compounds are either discontinued or perhaps the target patient population is smaller than originally planned, that's still pays dividends when it comes to higher success in the clinic.

[Interviewer] It's a very interesting notion, but it totally makes sense. In a lab setting, you always want to have a standardized setting, so you're always testing against the same thing. Of course, in reality, it's nothing like that when you actually deal with somewhat diverse patient populations.

Yeah, it's very different and it's taken some time. As I say there was some resistance in our early days to that variation in response. We would sometimes be doing studies in quite small numbers of donors just to look and see is there any evidence of an effect in humans. And if you take five to ten donors you might see two or three where they're super responders, two or three where there's a reasonable response, and perhaps a handful where there's no response. And I think that is now accepted much more readily because of precision medicine, because of the human genome project, because there's a greater awareness in the public as well that we don't all respond in the same way to drugs.

That was perhaps quite a difficult message to communicate 10 years ago where the wider public would not appreciate that if they tried medicine that hasn't worked, that's not because it was the wrong medicine to prescribe at that time, it was just there was no understanding really of what the factors would be in that individual that might see that drug work or not. And that is gradually changing, that is underpinning precision medicine, personalized medicine, but we've still got a long way to go before that's truly implemented.

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Is human tissue research something that companies would usually do in-house?

The tendency is usually to outsource, but there are many excellent labs in in pharma in academia who will do this type of work. But it does require specialist knowledge: it requires the access to the tissue the logistics and the flexibility of the 24/7 lab operation I mentioned. So we tend to see it most commonly done in specialist contract research organizations, or specialist academic groups who focus on a niche area of particular disease area or tissue type.

Outsourcing human tissue testing to a commercial lab has a number of benefits. For example, regulatory approval is possible for safety assessments in human tissue and having a quality assurance system is certainly a benefit. Also having the flexibility as a contract research company that's doing these things day-in-day-out means it becomes economical to actually run a lab 24/7. Even big pharma may find it impractical to do that, so I would say most commonly it's outsourced, and that is probably fits with a growing trend in pharma industry of working with specialist partnerships and outsourcing the right type of work.

[Interviewer] Right, because you rather have a partner that's super specialized so they can give you what exactly what you want, rather than necessarily building it up yourself.

Exactly, and I think there is a lot to develop and a lot to consider before embarking in one of these projects. There's the ethical approval, there's the logistics of the supply chain that we discussed, there's the protocols and the validation around the different tissue types. That's a lot of variables by the time you factor in the possible number of tissue types, different targets, different platforms that can be used. So having groups that have got experience across a wide range of those things really helps.


Would you say that the demand for human tissue research is increasing?

I think it has been driven up by precision medicine, but also driven up in the past eighteen months by COVID - there's been such a strong interest in collecting COVID positive and negative samples for research. Both to look at the way in which patients have been responding to vaccines and different therapies, but also understanding the biology of disease.

One of the first studies published about SARS-CoV-2 was around its ability to infect so many different types of cells, which is quite an unusual characteristic and a potentially dangerous aspect of the virus. The researchers used human tissue studies to look at gene expression of viral receptors in various tissues.

Outside of COVID, there's been a real increase in the use of human tissue for research. It's been a trend that's been there the past 10-15 years, and I can only see that increasing through the drivers of precision medicine and artificial intelligence (AI).


How do you think the regulators view the data you generate with human tissue research?

The regulators have gone through this this process with industry and, in some cases, have been at the forefront of efforts to remove barriers to research using human data. They have tried to promote the appropriate use of human test systems. Tests using fresh tissue are not mandatory yet, but they are supportive studies for safety pharmacology. We've even had requests from regulators for specific studies troubleshooting adverse effects that appear during clinical trials.

Around five years ago, the FDA and MRHA took the initiative, alongside organizations like the NC3Rs in UK, to survey the pharma industry asking about the barriers to increased use of human tissue in safety assessments, as that tends to be the primary focus for the regulators. The study showed that most pharma companies were either using the technology or developing methods to use it, which included human fresh tissue and other approaches, such as 3D models.

So I think the regulators are very supportive, but it's not a panacea by any means. I think it's unrealistic to say that human tissue testing could replace all animal experiments, but it certainly is already reducing and refining those experiments and there's going to be further progress over the next 10 years.

[Interviewer] So in summary what you're saying is that the regulators are happy to take the additional data. At the same time it's not mandatory, but it does reduce the amount of animal testing.

I think that's right, it's a case-by-case basis. Typically, if it's a target where it's understood that animal models may not reflect human biology (serotonin receptors, for example) then the regulators may request that you need to include some human tissue systems. It could also be the sponsers in pharma themselves that identify potential risks and decide that they need human data.

I think it's being driven by causes of clinical failure: efficacy, safety, and pharmacokinetics. Those three big areas will account for most of the clinical failures, and those are the areas where human tissue is being employed.

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What does the future hold for human tissue research?

Right now, we've got more data than anyone could imagine. And the challenge is not generating that data but using it intelligently to gain. I think that these insights are not going to come from genomics or transcriptomics alone, because time and again we've seen that the predictions made just from looking at insights next-gen sequencing are not sufficient to understand pharmacology.

To get to true pharmacogenomics, we need to include the functional data. In addition to understanding the omics, we also need to understand the other information about these individuals - the clinical data, the medical history, what drug history that individual been exposed to. And that's really where AI could help us make some breakthroughs, because we're increasing the volume and complexity of the data. I think we can achieve insights that wouldn't otherwise be possible by appropriate use of AI machine learning models.

[Interviewer] Because effectively you can access it from a big data perspective -get the different sources of data and hopefully come up with coherent information that's actually useful. It helps us drive science forward, right?

Exactly, that's right. We've done some preliminary work in this this field and published some initial work with the Precision Medicine Innovation Center (PM-ICS) here in Scotland. Also, more recently we've been working with experts in AI machine learning to understand why an individual might respond to particular drugs in our fresh tissue system. By using the human fresh tissue as a proxy for the likely clinical response of the individual we can understand why those individuals have responded and other individuals have not. I think that's a very exciting area, really bringing together pharmacogenomics.

[Interviewer] Absolutely, it does sound very interesting. I imagine though that the quality of the data you need to use an input must be very high - it must be accurate, it must be relevant right otherwise...

Absolutely - the quality of the data is key. I think a challenge is the number of donors that are needed, but a lot of effort is being made internationally, within both public and private sector initiatives, to safely share and gather data. For example, in Scotland we have a network of "safe havens": National Health Service (NHS) run institutions that provide a firewall between the patient data in the healthcare system and pharmaceutical companies, CROs, or academic researchers. They ensure appropriate anonymization and access while still ensuring that we can make medical breakthroughs.

[Interviewer] One of the main benefits of having a centralized health service: you do have a large supply of data, there's no doubt about it [laughs]

You know that's definitely a benefit in the UK in general, and in Scotland in particular. Scotland-wide there is this health identification number that every individual has, from cradle to grave. That number identifies all of the health records and allows access to all medical and prescription history.

Looking at these things is important - not just for medical research - but also for economics. There is a huge benefit. But the other part of that is the trust and the transparency with which that's done with the public, and to bring the public along is to the benefit of research.


If any of our listeners would like to contact REPROCELL, how would they go about that?

We'd be delighted to discuss any of the ideas or concepts in the discussion today. The best way is through our website - we've got our contact details for all our sites and email addresses on there.

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