It might not be new, but very few people have heard of it. Just passing on info so that you can sound very clever around the campfire when some smart aleck tries to stump you with this calibre.
I'd imagine that the task of making a truly 'new' cartridge would be daunting. Making one that does something that no existing one does perfectly adequately must be terrifying unless you are looking to exploit some arbitrary legal loophole like the need for straight walled cartridges for hunting in some states in the US or having a service pistol/rifle that doesn't use a military cartridge like has been needed in some parts of Europe before.