I guess they could have sold 60%+ of PBT434 through a license...

 I guess they could have sold 60%+ of PBT434 through a license deal and X<50% of the company at market, which would IMO been a good deal for all, or is it PBT2 they are after?  I wonder if the Life board knew about the PBT2 discovery when the deal was proposed. If the PBT2 data was published in Dec 18, I am left to wonder if any Prana insiders had given any insider info to Life(Alterity group. Means outsiders) that LT Aus and US holders were denied.
I would maybe check with the US SEC on the legality of what is going down if I owned stock. I know this is an Australian company, but the SEC has recently demonstrated a willingness to go after foreign based companies that trade in the US, and I think the majority are now US holders, who have possibly not been privy to the same level of info that the buyer has. That is just a guess, but probably worth a look.
https://www.perkinscoie.com/en/news-insights/u-s-agencies-step-up-insider-trading-enforcement-against-foreign.html 

The Law: In August 2000, the Securities and Exchange Commission (SEC) adopted new rules regarding insider trading (made effective in October of the same year). Under Rule 10b5-1, the SEC defines insider trading as any securities transaction made when the person behind the trade is aware of nonpublic material information, and is hence violating his or her duty to maintain confidentiality of such knowledge.Information is defined as being material if its release could affect the company's stock price. The following are examples of material information: the announcement that the company will receive a tender offer, the declaration of a merger, a positive earnings announcement, the release of the company's discovery such as a new drug, an upcoming dividend announcement, an unreleased buy recommendation by an analyst and finally, an imminent exclusive in a financial news column. In a further effort to limit the possibility of insider trading, the SEC has also stated in Regulation Fair Disclosure (Reg FD), which was released at the same time as Rule 10b5-1, that companies can no longer be selective as to how they release information. This means that analysts or institutional clients cannot be privy to information ahead of retail clients or the general public. Everyone who is not a part of the company is to receive information at the same time.https://www.investopedia.com/articles/03/100803.asp

I am not an investment advisor, and the opinions above are just that. Please ignore them and DYOR.