Comparing Capping

September 7, 2022 / by Venkata Indurthi, Ph.D.

Enzymatic and co-transcriptional capping for RNA

With the manufacture of RNA, capping is one of the many crucial steps in developing the final product. There are two methods of capping, enzymatic and co-transcriptional. Both have advantages and disadvantages.

From a service standpoint, when manufacturing RNA for our clients, we offer both enzymatic and co-transcriptional capping. Our RNA experts will discuss the pros and cons of each with a client but it is ultimately their choice. For clients manufacturing their own RNA, we offer a full line of IVT and capping enzymes for enzymatic capping.

Both enzymatic capping and co-transcriptional capping can get you to the same final RNA, so, I don't think there is an advantage of one over the other in the industry’s current state. With co-transcriptional capping, the big advantage is that it's a one-pot reaction. You add in the cap analog with the IVT reaction, which makes it easier from a manufacturing standpoint. However, there are intellectual property (IP) constraints and licensing issues that you must deal with at that end of the spectrum.

With enzymatic capping, these are wild type enzymes, and there is more freedom to operate. From an activity or a potency standpoint, our observations tell us that enzymatic capping can be a little bit better than co-transcriptional. Enzymatic capping results in a natural cap at the end of the day.

Of course, you must optimize the enzyme and enzymatic capping as well. However, when we've compared the activity of both enzymatic and co-transcriptional capping you can, by proper optimization of your processes, come up with RNA that functions exactly the same way.

As I mentioned earlier, a big reason for people choosing enzymatic capping is because of lack of IP. As an example, for Aldevron clients we’re a one-stop shop. We control the raw materials and make the capping enzyme for ourselves. But there is room for improvement from an enzyme engineering standpoint. Additionally, in many cases, you have the advantage of redundant supply.

In that vein, let's say you get a capping agent from one company and they suddenly experience supply chain issues. If they can’t provide the product you need, that could cause expensive production delays. But with enzymatic capping, multiple sources make the same enzyme, where that’s not the case with co-transcriptional capping. You would need to switch suppliers, but you would still be able to continue with your project.

The bottom line is that either method works and can help you reach your goals. That’s why I don’t favor one capping approach over the other as the result really depends on the molecule itself. Overall, the RNA market would benefit from different options that have a much higher capping efficiency, so that is an area where we are trying to improve no matter the approach being used.

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