Exploring the paradigm shift from traditional to precision medicine through advanced genome editing technologies
Imagine a world where medicines are tailored not just to your disease, but to your unique genetic code. This isn't science fiction—it's the promise of precision medicine, a revolutionary approach that's transforming how we treat everything from rare genetic disorders to cancer 5 . For decades, medicine followed a "one-size-fits-all" approach, often with limited success for complex conditions like cystic fibrosis, diabetes, and many cancers. Scientists now understand that genetic variations among patients with the same disease often explain why treatments work for some but fail for others 5 .
"The need for personalized medicines has opened the doors for turning nucleic acids into therapeutics." 5
The need for personalized medicines has opened the doors for turning nucleic acids into therapeutics 5 . At the forefront of this revolution are powerful genome-editing tools that act like molecular scissors capable of precisely cutting and repairing defective genes. These technologies were the focus of the fourth annual Biopharmaceutical Research and Development Symposium (BRDS) held at the University of Nebraska Medical Center (UNMC) on September 7-8, 2017, where leading scientists gathered to explore how to harness these tools for therapeutic applications and diagnose genetic disorders 5 .
Dr. Ram I. Mahato, chair and professor of the Department of Pharmaceutical Sciences at UNMC, initiated the BRDS in 2014 to nurture relationships between biopharmaceutical industries, academic researchers, and students 5 . The 2017 symposium brought together 15 scientists from around the world representing both academia and industry, along with young scientists selected from various educational institutions for podium and poster presentations 5 .
This interdisciplinary focus fostered knowledge sharing and intense discussion among scientists with broad interests in gene therapy. As Dr. Vincent H.L. Lee from the Chinese University of Hong Kong noted in his opening address, transforming drug discovery and development requires a paradigm shift that considers pharmacogenomics, systems biology, gene therapy, and tissue engineering 5 . The symposium facilitated exactly this type of cross-pollination of ideas, presenting novel technologies, clinical successes, ethical considerations, and future directions for genome editing.
Bringing together experts from academia, industry, and research institutions
International Scientists
Annual Symposium
Inception Year
Scientific Disciplines
The journey to precise genome editing began with the discovery of DNA's double-helix structure 6 .
Scientists discovered restriction enzymes that could cut DNA at specific sequences, paving the way for recombinant DNA techniques 6 .
Zinc-finger nucleases (ZFNs) were engineered proteins that could introduce double-strand breaks in DNA at specific locations 1 6 . While ZFNs significantly improved gene editing efficiency over earlier methods, their design was time-consuming, laborious, and expensive 1 6 .
TALENs (transcription activator-like effector nucleases) offered easier design and the potential to target a wider range of sequences 1 6 . However, like ZFNs, TALENs still required engineers to create a new protein for each target—a significant limitation 6 .
The CRISPR-Cas9 system differed from previous technologies by using RNA instead of proteins for targeting 1 6 . The easily programmable single guide RNAs (sgRNAs) could be designed to home in on any DNA sequence, while the Cas9 nuclease acted as the molecular scissors 1 . This system dramatically simplified and accelerated genome editing, leading to its rapid adoption in labs worldwide 6 .
| Technology | Mechanism | Advantages | Limitations |
|---|---|---|---|
| ZFNs | Engineered zinc-finger proteins fused to FokI nuclease | First efficient engineered nucleases; higher efficiency than homologous recombination | Difficult to design; time-consuming; expensive; limited targeting range |
| TALENs | TALE proteins fused to FokI nuclease | Easier design than ZFNs; wider targeting range | Still requires protein engineering for each target; large size |
| CRISPR-Cas9 | RNA-guided Cas9 nuclease | Simple design (just change RNA sequence); highly versatile; high efficiency | Off-target effects; larger complex for delivery |
While CRISPR-Cas9 represented a major leap forward, scientists continued refining these tools for greater precision. In 2016 and 2017, researchers developed base editors that could chemically convert one DNA nucleotide to another without cutting both strands of DNA 6 . These come in two main types: cytosine base editors (CBEs) that change C•G to T•A, and adenine base editors (ABEs) that change A•T to G•C 1 6 .
In 2019, researchers developed an even more precise system called prime editing that can perform targeted insertions, deletions, and all types of point mutations without creating double-strand breaks 1 6 . By fusing a modified Cas9 to an engineered reverse transcriptase, prime editors can directly write new genetic information into a target DNA site specified by a specialized guide RNA called a pegRNA 1 . Recent research from MIT has further refined prime editing, dramatically lowering its error rate from about one error in seven edits to one in 101 for the most-used editing mode 2 .
A central concern with CRISPR-based therapies is off-target effects—unintended edits at similar DNA sequences that might cause harmful mutations 5 . As Dr. Shengdar Tsai from St. Jude Children's Research Hospital explained at the symposium, his team developed innovative methods to identify these off-target effects across the entire genome 5 .
(Genome-wide unbiased identification of double-stranded breaks enabled by sequencing) works by efficiently integrating short DNA tags into the sites of nuclease-induced breaks, followed by tag-specific amplification and high-throughput sequencing 5 . This provides a comprehensive picture of where editing is occurring throughout the genome.
(Circularization for in vitro cleavage reporting by sequencing) takes a different approach by selectively sequencing genomic DNA fragments cleaved by Cas9 in vitro 5 . Together, these methods provide easy, rapid, and comprehensive ways to identify genome-wide off-target mutations, enabling researchers to design safer CRISPR systems 5 .
More recently, researchers at the Broad Institute have developed additional safety measures, including a system called LFN-Acr/PA that uses a protein-based delivery system derived from anthrax toxin to introduce "anti-CRISPR" proteins into human cells . These proteins can rapidly shut down Cas9 activity after its editing job is done, reducing off-target effects and improving clinical safety .
Even the most sophisticated gene editors are useless if they can't reach their target cells. Delivery remains one of the biggest challenges in CRISPR medicine 3 . At the symposium, Dr. Daniel J. Siegwart from the University of Texas Southwestern Medical Center presented his work on zwitterionic amino lipids (ZALs)—specially designed nanoparticles that can safely co-deliver Cas9 mRNA and a single guide RNA to target cells 5 .
When intravenously administered to genetically engineered mice, these ZAL nanoparticles successfully induced gene editing in the liver, kidneys, and lungs 5 . The approach achieved a remarkable 95% decrease in protein level in vitro, demonstrating its potential effectiveness 5 . This non-viral delivery method offers advantages over viral vectors, which can trigger immune reactions and can't typically be readministered 3 .
Lipid nanoparticles (LNPs) have a natural affinity for the liver when delivered systemically, making them particularly useful for diseases where the relevant proteins are primarily made in liver cells 3 . Researchers are also working on creating versions of LNPs that have affinity for different organs, though these have not yet been tested in clinical trials 3 .
Protein Level Decrease In Vitro
Organs Targeted (Liver, Kidneys, Lungs)
Nanoparticle System
One of the most dramatic presentations at the symposium came from Dr. Kamel Khalili from Temple University, who described using CRISPR-Cas technology to pursue a cure for HIV/AIDS 5 .
The challenge with HIV is that the virus inserts its genetic material into the host's genome, creating "proviral DNA" that hides in cells, evading both the immune system and conventional antiviral drugs 5 . Dr. Khalili's team designed CRISPR-Cas systems to target and remove this integrated HIV-1 proviral DNA from the host genome 5 .
The experiment involved several key steps:
The research team demonstrated that their CRISPR system could successfully excise the HIV-1 provirus from infected human cells 5 . Even more importantly, they showed that the edited cells were protected against viral spread and reinfection 5 . The excision of the HIV genome occurred without significant damage to the host cells, suggesting the approach could be both safe and effective.
This groundbreaking work offered the first realistic strategy for completely eliminating HIV infection rather than merely managing it with lifelong drug therapy. The success in cellular models has paved the way for potential clinical trials aimed at curing AIDS in humans 5 .
| Experimental Measure | Finding | Significance |
|---|---|---|
| Proviral excision efficiency | Successful removal of HIV-1 DNA from host genome | Demonstrates feasibility of complete viral eradication |
| Cell viability post-editing | No significant damage to host cells | Suggests potential safety of the approach |
| Protection against reinfection | Edited cells resistant to new infection | Prevents rebound if all infected cells are cleared |
| Off-target effects | Minimal at predicted off-target sites | Supports clinical potential with further refinement |
| Reagent Type | Specific Examples | Function | Applications |
|---|---|---|---|
| Nucleases | ZFNs, TALENs, Cas9, Cas12 | Create targeted DNA breaks | Gene disruption, insertion, deletion |
| Editing Enhancers | Base editors, Prime editors | Enable precise nucleotide changes | Correct point mutations without DSBs |
| Delivery Vehicles | AAV, Lentivirus, Lipid Nanoparticles (LNPs), ZALs | Transport editing components into cells | In vivo and ex vivo therapies |
| Guide RNAs | sgRNA, pegRNA | Direct nucleases to specific DNA sequences | Target specification for all CRISPR applications |
| Detection Tools | GUIDE-seq, CIRCLE-seq | Identify off-target editing events | Safety assessment for therapeutic development |
| Donor Templates | ssODN, dsDNA with homology arms | Provide template for precise edits | HDR-mediated gene correction |
Viral and non-viral methods to transport gene editing components to target cells
Advanced sequencing techniques to identify off-target effects and verify edits
Nucleases, base editors, and prime editors for precise genetic modifications
The fourth annual BRDS symposium showcased both the remarkable progress and remaining challenges in genome editing for precision medicines. Since 2017, the field has advanced dramatically, with the first FDA-approved CRISPR-based therapy (CASGEVY for sickle cell disease and transfusion-dependent beta-thalassemia) reaching patients 1 3 . Clinical trials have expanded to target more common conditions, including heart disease and high cholesterol, with highly promising early results 3 .
The landmark case of baby KJ—an infant who received a personalized in vivo CRISPR therapy for CPS1 deficiency developed and delivered in just six months—demonstrates how far the field has progressed 3 . This case, which involved physicians and scientists from multiple institutions, serves as a proof of concept for on-demand gene-editing therapies for individuals with rare, previously untreatable genetic diseases 3 .
However, significant challenges remain. Delivery to specific tissues beyond the liver is still difficult, editing efficiencies need improvement, and safety concerns must be continually addressed 3 6 . Additionally, the high cost of these therapies and ensuring equitable access present substantial hurdles 3 .
Delivery Challenges
Editing Efficiency
Safety Concerns
Cost & Accessibility
Emerging technologies like AI-powered CRISPR design tools are now accelerating progress 7 . Stanford researchers have developed CRISPR-GPT, an AI tool that helps scientists design better gene-editing experiments faster, potentially reducing the timeline for developing new drugs from years to months 7 .
The fourth annual BRDS symposium highlighted both the tremendous potential and significant challenges of genome editing for precision medicine. As these technologies continue to evolve, they promise to transform how we treat not just rare genetic disorders, but potentially common conditions like heart disease, cancer, and neurodegenerative disorders.
The interdisciplinary collaboration exemplified by the BRDS—bringing together chemists, biologists, clinicians, and engineers—will be essential to overcoming current limitations. With continued innovation in delivery systems, editing precision, and safety measures, the vision of truly personalized medicines tailored to an individual's genetic makeup is coming closer to reality.
As Dr. Mahato noted when initiating the symposium, realizing the full potential of these technologies requires nurturing relationships between industry, academia, and the next generation of scientists. The discussions and discoveries shared at the fourth annual BRDS have contributed significantly to advancing this exciting frontier, bringing us closer to a future where genetic diseases are not just managed, but cured.