April 2023 ChromaChats™ Recap: Challenges in the Purification of AAVs

We had a wonderful turnout for our first ChromaChats™ meeting on Wednesday, April 26th. We had 30 industry leaders in attendance for a discussion focused on “Challenges in the Purification of AAVs”. This roundtable was co-led by Chromatan CEO Oleg Shinkazh and Dr. Peter Abbink, Managing Director at Batavia. The extensive discussion addressed many topics ranging from purification operations, pain points such as high cost and low recovery, scalability challenges, as well as what the future of AAV manufacturing looks like. We cherrypicked some points below, but only the attendees get the full scoop.

Topic: Pain Points for AAV Purification - Loss in Recovery for AAV Capture

• Meat of the problem = scalability & chromatography.
• One thing Oleg from Chromatan learned in their process is that a small addition of poloxamer made a significant difference. They were running a process where for the first 30 minutes, product was getting absorbed somewhere on the tubing or in the system, but when they added 0.01%, they were able to recover much faster.
• AAV protein concentration is quite low. One attendee discussed how when protein concentration is low, you notice how much more it sticks to surfaces. Using products to combat surface adherence can boost yields.

Topic: Do certain resins work better to optimize elution profiles

• An attendee on the call discussed her company’s experience and the importance of finding good resin: With all the new resins coming in, she explained how they don’t want to miss an opportunity to find one, but that it’s a hard balance between using material, using time, and also screening the resins thoroughly. One of the main methods they employ is very small-scale screening using a liquid handler.
• Small-scale screening has worked well and has scaled up well. With the liquid handle, it takes a lot of preparation to make sure it can act like the platform you use. Important to match it to your system as much as possible.
• Volume for experiment depends on load and concentration you are starting with. The attendee's company uses very little because liquid handler they use has 200μL and 600μL columns.
• Another pain point: just because they have a nice separation process for one certain type of capsid doesn’t mean it will always work for the others.

Topic: Any guidance from regulatory and what they are looking for full percentage?

• One attendee shares his experience and thoughts: Attendee discussed how what a regulatory agency is looking for but won’t tell you is “is your product safe”? That’s ultimately what you are trying to achieve and it’s not something any regulatory agency can tell you as they themselves don’t know.
• There are so many factors that come into play with product safety – it’s very product specific, it depends on what tissue you are trying to deliver it to, and what your delivery method is. Up to you to show why you think the distribution profile of your product is safe and to achieve empty/full ratios that you can safely demonstrate in animal and human models.

Topic: Where is the value on the triangle of product quality, yield, and cost

• One attendee shares how as a process development person, he tends to stray towards product quality, but that there is a direct trade-off in gene therapy with product quality and yield surrounding empty/full separation.
• How do you increase yield while maintaining product quality? Attendee shares that the key to achieving both is to develop a technology that can be both high yielding and support high purity.