I believe that the evaluation made by "third parties" of only 500 million, reflects only the tangible / concrete data expressed by Ngio, therefore mainly the excellent results of phase 2b of ae37, and does not include the value of the li-key covid vaccine, as there are still no official data that can prove its effectiveness (we have not yet started phase 1 ..)
Consequently, I think Joe delays the listing as much as possible, in order to add to the initial 500 million, the value given by the vaccine (which, confirming positive concrete data, could be worth a few billion).
So I expect a listing no earlier than half a year, with full vaccine results ...