Agreed. Investor NDAs covered (a) the existence and terms of the transaction prior to those being released in an 8k (this would include voting arrangements, etc), and (b) a separate NDA covering certain fundamental information about the trial / company.
All investors would have to sign "a". This NDA would prohibit trading until the 8k is released. NDA "b", while optional, would give long term investors comfort that the technology is compelling. The can't sell until the fundamental data is publicly available but why would they? If there is a significant therapeutic benefit, the stock is not going to stop at $0.50