Executive Interview with Tobias Raabe, University of Pennsylvania

[0:00:00] Transcript

[0:00:21] Hi everyone and welcome today, we're joined by Dr Tobias Raabe, a Research Assistant Professor of Medicine at the University of Pennsylvania. His group is pioneering work in gene targeting and gene editing with a strong focus on human models.

[0:00:43] Tobias and his team are using lipid nano particles and patient derived organoids to better understand and develop new therapies for liver fibrosis. So welcome Tobias. It's good to have you with us today. I guess first question is, what drew you to human models in the first place, particularly within the context of gene targeting for liver fibrosis?

[0:01:05] Hi, thank you, Lucia, for the opportunity to talk a little bit about what we are doing.

[0:01:26] The answer to your question is foremost liver fibrosis and especially end stage liver disease. Or ESLD presents a major unmet clinical need.

[0:01:48] Secondly, mouse models of end stage liver disease do not accurately model the human disease, including important hallmarks of liver disease, such as hepatocyte senescence and ballooning, and they are relatively profound pathophysiological implications.

[0:02:10] And third, since 2011 we have organoids which were introduced by the clever slab in the Netherlands, and because of that, there's a completely new avenue of research possible.

[0:02:31] For example, patient liver derived organoids contain the epigenetic landscape of the diseased human liver, right? And in theory, therefore, these are the preferred preclinical model, enabling clinical translation, better than other models, especially rodent models, and probably in concert with non-human primates, which, of course, are pretty expensive,

[0:02:53] Perfect. Thank you very much. Could you maybe expand a bit more on your co culture system with the hepatocytes, fibroblasts and macrophages, just touch a bit more on how the cells interact?

[0:03:15] Sure the main features of our CO culture system are, it is currently a triple co culture of end stage diseased patient liver derived organoids, which contain mostly hepatocytes and also of human liver derived hepatic stellate cells and also peripheral human monocytes, so three different sources of cells.

[0:03:36] However, after combining those cell types in a special fibrosis medium, the hepatocytes become highly senescent and secrete factors that trans differentiate hepatic stellate cells in the proliferating collagen expressing myofibroblasts, and also those factors convert monocytes to pro inflammatory macrophages.

[0:03:58] And so these cell types are the exact cell types found in human end stage liver disease. So again, this is sort of a model that can, in a short period of time, like about a couple of days, induce the fibrotic niche of diseased liver. And I think it's relatively new. I don't think something similar has been made before. I may be wrong.

[0:04:20] Thank you very much, and I think you've already touched a bit on this about the patient derived tissue and the parenchymal patient derived cells and the importance of their epigenetic memory. Could you expand a bit more on what advantages these cells have?

[0:04:42] Sure our system is fully modular, right? And organoids, or just primary parasites, by the way, from a wide variety of liver diseases, can be added to it. So you could, like, take livers from viral hepatitis, from alcoholic cirrhosis, etc, make organoids or make hepatocytes and add them to the system.

[0:05:03] So it's very, very modular. Secondly, the system is compatible with cell type specific lipid nanoparticle mediated genome editing. And I think that's quite unique, as far as I can tell. And we have developed lipid nanoparticles that specifically target hepatocytes or myofibroblasts or macrophages, in other words, highly cell type specific.

[0:05:25] And of course, for many therapies, that's very important, because, for example, if you want to kill myofibroblasts, you don't want to also kill hepatocytes, right? And then, thirdly, it allows discovery of novel human therapeutic pathways. And the proven principle is that we found a novel pathway, a pathway that promotes myofibroblast proliferation, and we are currently evaluating this with novel antifibrotic therapies.

[0:05:47] So a pathway found in organoids, not in mice, and also the system is fully compatible with HTP screening, and this is really important for industrial applications, and therefore we are also very interested in collaborations with industry

[0:06:08] Perfect. Thank you very much. Could you maybe expand on the type of collaborations that you think will benefit most from your platform?

[0:06:30] I would say screening of therapeutic candidates would be an obvious one, because there are many companies that are interested in end stage liver disease, and they have their own therapeutic candidates, but they need to de risk them more.

[0:06:52] And I think our system is prime example of how you can use human cells, human organ, it's derived directly from the diseased tissue or liver in order to de risk and that there's simply not many companies that can do that by themselves.

[0:07:13] I see. Thank you very much. And what were the main challenges you encountered while developing this platform,

[0:07:35] I would say three.

[0:07:57] First, development of a medium and of extracellular matrix supporting multiple cell types in a triple co culture was not easy. There's no precedent for this system. Secondly, the optimizing of the timing of cell type addition and optimizing of the amounts of cell types added is also not easy. It sounds maybe trivial, but it's not.

[0:08:19] It's very important. And thirdly, the development of lipid nanoparticle mediated genome editing was quite challenging because there were no preexisting examples where nanoparticles were developed for an organoid system with multiple cell types.

[0:08:40] Thank you very much. And again, I think you've touched a bit on the importance of targeting more than one liver cell type simultaneously. And I guess, what could this mean in the broader sense for liver fibrosis patients, and what challenges remain in achieving this?

[0:09:02] Yeah, thanks for that question. It's a really important one. I think so. The background is that almost all clinical trials on end stage liver disease used a single drug, right? And they all have either completely or mostly failed despite 20 plus years of trying so very bad record, and that's probably due to the complexity of end stage liver disease, right?

[0:09:24] So, however, simultaneously targeting two or more cell types may may be much superior to targeting one cell type or targeting one gene, right? So, for example, it is known that hepatocytes are mechanic, mechanically stimulated by myofibroblasts, and as a result, lose their normal functions. Right?

[0:09:45] On the other hand, myofibroblast proliferation is suppressed, suppressed by healthy hepatocytes, but not by diseased hepatocytes, right? So there is a very strong hepatocyte myofibroblast crosstalk, right? Very strong, and it's very well documented, by the way. This is not as this is not a suggestion or an idea. This is, this is a fact, okay? And so therefore, I think it's automatic.

[0:10:07] That it suggests that targeting both cells at the same time should have a synergistic effect, a beneficial effect.

[0:10:29] Great. Thank you very much. Yeah, it definitely seems like an ambitious project, and we talked a bit about the importance of perception and mindset. So how does the biopharma sector view organoids and other human based models right now?

[0:10:50] Well, currently, it's clear that Pharma is interested. They are mostly have their own organoid facilities. And so far, the involvement of organoids in industry is sort of a system where they use organoids as in a helper function, right, but not as the main method.

[0:11:12] For example, there are FDA approved AAV mediated gene therapies like luxterna that have benefited from pre clinical research that included organoid systems right also platforms like organ on a chip and organoids are increasingly used to enhance safety pharmacogenetics and disease modelling in IND submissions. And there's an example, a liver chip, which is an organoid chip, was admitted into FDA pilot program in September 2024 right and that reflects regulatory acceptance for its use in supporting safety data, and also agency like the hub means the Hubrecht Institute organoids, which is now part of Merck, they report that their platforms helped streamline bispecific antibody Candidate Selection.

[0:11:34] So, it's a wide variety of things, but at the moment, in a helper function, I think in the future, this will change and expand.

[0:11:56] Thank you very much, and several of your projects have received funding from the NIH. So what are the key milestones you are hoping to achieve in the next year or two. Yes, there's a card that we have on the role of senescence in fibrotic liver and obese fat deposits and its relevance for infectivity by viruses such as SARS, cov two and others, and we are using human organoids and cells derived from patients liver, from patients fat and from patients lung for these studies.

[0:12:17] And another one is determining if dual targeting strategies, using cell type specific LNPs In end stage liver disease could act synergistically, something we just talked about.

[0:12:39] Perfect. Thank you very much. And final question from me, Tobias, so we're obviously very excited to welcome you to ask the Global's Discovery and Development Conference. So what key message are you hoping to leave the audience with from your presentation?

[0:13:01] Yeah, that's a great question. I would say a couple. Number one, organoid technology is ready for the next step. I think that's probably the most important one. So I would not be surprised if FDA approvals in the future could be based primarily on human organoid data, right?

[0:13:22] Some of them, at least. Secondly, organoids can be used not only for toxicity testing, but they can be used for evaluating biological effects of therapeutics and also for discovery of novel pathways, if I, as I just described above, and thirdly, integration of organoids with micro fluid existence and tissue printing systems will probably happen more in future.

[0:13:44] And all these non animal models, these three non animal models will complement each other, and that will result overall, in a reduced need for animal models in general, which is a good thing.

[0:14:06]  So non animal models, including human tissue derived organ and systems, have also the capacity to de risk lipid nanoparticles for human use, for a fraction of the cost of non-human primates.

[0:14:27] And I think that's really important, because the whole therapeutic field is moving towards lipid nanoparticles, even for complex diseases like cancer and liver disease.

[0:14:49] Perfect. Thank you very much. Definitely good takeaway messages so Tobias, thank you for sharing your thoughts and insights with us today on the organoid landscape, and we are very much looking forward to welcoming you Oxford Global Discovery and Development event taking place in San Diego from the second third of October.

[0:15:11] Tobias, thank you very much once again. Thank you very much indeed.