This exclusive article is by Dr. Ralph Vogelsang, Senior Director of Business Development & Licensing, ERS Genomics.
Conventional drug discovery models, such as animal models or human cell lines, often fail due to their divergence from human biology. In fact, over 90% of drugs tested in animals subsequently fail in human trials.
Enter organoids: three-dimensional in vitro models of organs or tissues derived from stem cells. Organoids closely mimic the structure and function of their natural counterparts, making them ideal tools for scientific research and drug discovery. Now, a number of companies are exploring how CRISPR-Cas9 technologies could be used in organoid research to aid a wide range of applications, from drug screening to precision medicine.
The rise of CRISPR in organoids
Organoids have come a long way since their inception in the early 2000s by Dr Hans Clevers. His pioneering work eventually led to the first intestinal organoids in 2009, with many other organoid models being developed in the years that followed. In 2013, the first successful cerebral organoids were created soon after, in 2015, CRISPR gene editing technology was integrated into organoid research, opening up entirely new possibilities in the field. CRISPR works by using RNA molecules to guide molecular scissors to specific DNA sequences, allowing precise gene editing by either adding, deleting, or modifying genes.
CRISPR-engineered organoids harness that precise genetic manipulation within a physiologically relevant platform, unlocking unprecedented insights into disease mechanisms, drug responses, and potential therapeutic approaches.
A closer look at disease
CRISPR-engineered organoids offer a powerful platform for unravelling diverse disease mechanisms. By manipulating specific genes within these 3-D models, researchers can delve into the intricate functions of genes implicated in various diseases.
For example, in a recent study published in Nature, researchers used patient-derived induced pluripotent stem cells and CRISPR engineering to develop a model of Leigh syndrome (LS). LS is a severe neurological disorder in children and currently has no cure. Traditional models fall short of allowing researchers to study the underlying neuropathology of this disease.
Using CRISPR, the researchers introduced mutations in the complex IV assembly gene SURF1 to develop the organoid model. Investigations and experiments using this model shed light on the molecular intricacies that hamper proper neuronal morphogenesis in LS.
Such investigations using CRISPR-engineered organoids not only enhance our understanding of disease mechanisms but also pave the way for the discovery of new drug targets. In the case of LS, the study suggested potential interventional strategies, such as boosting the SURF1 gene or targeting PGC1A.
Refining drug screening
As organoids closely resemble in vivo conditions, they also offer researchers a more accurate model for testing both the efficacy and safety/toxicity of drugs.
Patient-derived organoids (PDOs) have emerged as robust pre-clinical models in cancer as they demonstrate a high degree of similarity to the original patient tumour. However, PDOs can be challenging to extract or culture. CRISPR-engineered organoids offer a versatile and accessible platform for drug testing, and they are already being used to expand the scope of drug screening applications.
In a recent study published in Nature, CRISPR-engineered organoids were used for drug screening in nonalcoholic fatty liver disease (NAFLD). Human fetal hepatocyte organoids, modified using CRISPR, were used to screen drug candidates to identify compounds effective at resolving steatosis – the first stage of NAFLD. This approach not only allows researchers to explore potential drug targets, it also sheds light on the mechanisms by which specific compounds affect their therapeutic efficacy.
Solving the precision medicine puzzle
Similarly, PDOs are already being used to screen drugs for personalised therapies, such as is the case with cystic fibrosis.
Many individuals with cystic fibrosis carry rare mutations and clinical trials are not available to test the efficacy of certain drugs for these individuals. Personalised therapies offer the chance to harness the unique genetic and molecular characteristics of individuals and tailor medical treatments to specific patients, maximising the efficacy of treatments while minimising potential side effects.
HIT-CF Europe is a research project that screens drug candidates in PDOs to determine if they are safe and effective for those with rare mutations. However, getting access to PDOs is not always easy. Using CRISPR-engineered organoids, existing drugs could be tested for their efficacy against known rare mutations, improving the development of personalised therapies for individuals with rare conditions.
Future applications
The potential applications of CRISPR organoids in drug discovery and development are vast. Just a few months ago we saw the first FDA approval of a CRISPR-based gene therapy for sickle cell disease, pavi–ng the way for many more exciting developments in the CRISPR space.
For example, CRISPR-engineered organoids could aid in the development of T-cell immunotherapies in the future. Currently, and despite their promise, very few T-cell immunotherapies have been approved because current platforms to study interactions between cancer and T-cells are limited. Tumour organoids that have been genetically engineered to express specific mutations associated with cancer could be the perfect platform to assess the sensitivity of tumour-reactive T-cells for immunotherapy.
Whatever the future holds for CRISPR-engineered organoids, there is no doubt about their potential to “transform scientific research and drug development. From unravelling disease mechanisms to enabling personalised therapies, there are a myriad of applications to explore in the space.
