The company said, however, that it remains in discussions regarding a potential new extension to the exclusivity period.
The talks are with a view to advancing a transaction, the terms for which have yet to be agreed.
In March, Curzon announced the signing of a letter of intent which envisaged a reverse takeover transaction with SSSIG that would see the resulting company owning 100% of the London Critical Metals Market (LCMM).
Since then work has been underway relating to due diligence and financing.
In a statement today, the company noted: “While the parties continue to work constructively towards renewing exclusivity and a potential transaction, there can be no certainty around the length of time required to reach definitive agreement or the likelihood of concluding a successful transaction. The company will continue to update the markets on progress as appropriate.”