Here is the link to the US National Library of Medicine to learn all that is currently available about Lennox-Gastaut Syndrome and the available treatments and what lies ahead in living with it.
https://medlineplus.gov/genetics/condition/lenn...

And here is additional information from the Epilepsy Foundation:
https://www.epilepsy.com/learn/types-epilepsy-s...

These 2 of the best sources of the up-to-date information on Epilepsy in the world.

And have you read this article from the Resources section of MyEpilepsyTeam?
https://www.myepilepsyteam.com/resources/lennox...

I am actually an epileptic who takes Onfi (clobazam) for my seizures, and it’s the only thing that has ever controlled them. I don’t know enough about Lennox-Gastaut to give any advice, but I am sure there are resources on this site to go through to find answers.

I hope you and your son have a very good, and seizure free evening.