If Anavex has insufficient rights to the commercial use of their sigma-1 receptor activators (blarcamesine, etc.) and this is a legitimate risk, are the institutional owners of millions of shares of AVXL ignorant of such?
A patent is not required to market and commercialise a product. However, without patent protection or with weak protection the risk is someone else being able to use your invention commercially or someone seeking enforcement against you claiming infringement of their patent.
The latter can and does happen all the time even with patent protection, but by having a strong patent (and sometimes a large tit for tat patent portfolio) there are means of deflecting infringement claims or better options for out of court settlements.
This is why investors and partners generally would like to see good patent protection before risking their own money and resources on a new product/idea.