The AAV project continues to move forward and we have both progress—and some unexpected developments to report.
A Refresh – What is the AAV Project?
The AAV Project originated as the best path towards a viable therapy for children already living with ATP1A3 diseases (e.g.: AHC). It began after more than 6 months of intensive research by our scientific team into therapeutic options. Essentially, the only two real options were drugs and genetic therapies.
- Drug research includes (A) on-target and (B) off target drugs, but it’s an expensive proposition. The cost of finding new or repurposed on-target drugs for our ATP1A3-related diseases is enormous (for example $6.6 billion for Cystic Fibrosis). Other challenges include inaccuracies of in-silico modeling, expensive low-throughput screening, difficulty narrowing large libraries of drugs to those that might work, etc.
- A more viable option is genetic therapies, which includes (A) transgene delivery (like AAV-mediated gene therapy), (B) knockdown options (like antisense oligonucleotides), and (C) gene editing (like CRISPR). The most immediate and cost effective of those remains transgene delivery through AAV-mediated gene therapy – this is what we have been calling “The AAV Project”.
We continue to move forward, but also experienced several unanticipated results. In the update below, you’ll see that they turned out to be a blessing in disguise.
Spring and Summer – Initial Testing Phase Started
On March 10, 2020, Jackson Laboratory (“JAX”) expanded our ATP1A3 mouse colony using IVF. We expected 200 mice to be born, and approximately half of those to harbor a D801N mutation in ATP1A3 and present symptoms of AHC. Here is what occurred:
- 198 mice were born on March 29 and 30
- However, testing on their genetic sequences showed that JAX had used first-generation sperm instead of the intended second-generation sperm to produce the colony
- This resulted in only 37 mice with AHC. Eleven of these died before testing could begin, leaving too few mice to deliver statistical significance.
- We were still able to gather valuable information from this smaller sample size
Because of their error, JAX agreed to pay for both the IVF expansion, and a pilot study on the 26 remaining AHC mice. They injected our mice with one of our AAV vectors and tested them for a rescue at no cost to the project. Even though it delayed the project, we learned an enormous amount.
Important Discoveries Before Expensive Testing
In the experiments that followed in Jax’s pilot study, mice treated with the therapeutic vector showed:
- Some marginally better early bodyweight data, recovery from dystonia, and gait data.
- However, a significant percentage of injected mice died, including both control mice (those that received a “placebo-like” empty vector) and treated mice (those that received the therapeutic vector).
- Many of those mice died during a move from the storage facility to the behavioral testing facility, probably due to the stresses of cage-rattling, loud noises, bright lights, etc. – similar to the stimulus stresses our children are sensitive to.
- Other causes of death could be related to the trauma of brain surgery on a mouse model prone to seizures and sudden death or from problems with the vector.
We are now calibrating the numerous variables at play. Those include identifying the cause of death in our mice, the adequacy of the distribution and expression of our vectors in the mouse brain, potential toxicity of our vectors, the optimal DNA sequence of our vectors (including promoter analysis), specificity of expression of our vectors (expression in the right parts of the brain, and no expression in the wrong parts), dosage testing to make sure we are not over-dosing the mice (overexpression or toxicity), and optimizing the delivery site to make sure that our injections are not injuring the mice and causing additional deaths or seizures.
We see this as very important testing before we initiate the larger, significantly more expensive investigation.
The Blessing in Disguise
JAX’s error, and their steps to correct it, has allowed us to pause and strengthen the next step – the expensive and extensive round of behavioral tests.
Collaborating scientists have been briefed on our results and have offered substantial input in all areas. Scientists tend to take these course corrections in stride, but all of us as parents feel the delay acutely. To that end, we are currently pursuing these next steps:
- Investigating the causes of problems in our pilot study and working quickly to resolve them.
- Performing a number of additional experiments to help refine the vector, the delivery method, and dosages.
- Using the data collected to decide on the changes to make and when to go ahead with the larger study.
- Continuing to optimize dollars, while keeping a judicious eye on our timeline.
- Continuing to explore other possible treatment alternatives in parallel — from gene editing (CRISPR-Cas9) to drug screening.
The compelling reasons that make AAV-mediated gene therapy such a strong choice for AHC remain. It is a mature, well-tested, highly successful therapy that can be approved by the FDA with relative ease. With a strong plan and this stroke of good luck, the AAV-Project continues to move forward.