Label discussions are part of routine prior to final decision. The confidentiality agreements keep this material information under wraps and no one is allowed to trade or even discuss this info with others not under this confidentiality agreement. If the label is being agreed upon to be expanded then NWBO must prepare accordingly. Evidence is not proof but for investors it is often enough to put together what is likely going on; ). Seems like you are here trying to get investors not to figure things out. Gee, I wonder why; ). Best wishes.
It does not need to be on official letterhead to be material. Materiality depends on the substance of the information. If a reasonable investor would consider it important, especially in a company where approval is the central value event, then it is hard to wave it away as immaterial just because the formal approval letter has not been issued.
Approval is material when official approval is granted and nothing else. Conversations with MHRA that include things such as "we really like your MAA and think it stands a very good chance of approval" for example are not material.
Why? Because it is not approval. Things could change before the official approval is granted.
Only approval has the financial consequences on the positive side. A CHM negative letter does have material status on the negative side because it is an official statement on the status of the MAA and, of course, a rejection is material.