"Ten million doses will be produced between July 1 and January 1, 2022," he added, describing it as the "first agreement on the European level for the production on EU territory of the Sputnik vaccine".
Several European Union countries have already begun distributing Sputnik V, but it has yet to be approved by the bloc's medicines regulator.
Last week the Amsterdam-based European Medicines Agency launched a rolling review of the Sputnik V vaccine, a key step towards being approved as the first non-Western jab to be used against the coronavirus across the 27-nation bloc.
"If the vaccine is not authorised in Europe by July 1, the doses produced (in Italy) will be bought by the Russian sovereign fund and distributed in countries where the Sputnik vaccine is authorised," Maggi said.
Italy's health ministry, contacted by AFP, declined to comment on the deal, while Adienne was not immediately available.
The EU has so far authorised three vaccines: the US-German Pfizer/BioNTech jab, US firm Moderna's shot, and the British-Swedish AstraZeneca/Oxford vaccine.