According to Delaware corporate law, the charter of a company that is delinquent in filing an annual report and paying their state taxes is voided after 1 year. The last status for BioAmber, Inc., was March of 2019 showing over $300K of delinquent taxes. The company is completely out of business, so when the 1 year is over in March of 2020, Delaware will void that charter.
Right now the shares are equity in a company that only exists on paper. After Delaware gets done, the shares are equity in absolutely nothing.