Ann: Notice of General Meeting/Proxy Form, page-43

To me it means they knew about it much earlier, but not sure that is a bad thing, considering Prana did say they were working on/considering other stuff with PBT2. If they released that info to outsiders in order to give them commercial advantage over holders and other potential investors, then it is very suss bro.
If the work required for the publication was paid for then I think Prana knew about it a long time earlier. At what time it became price sensitive info is another matter. The fact they published without Prana participation is confusing.