The Italian is currently banned for 18 months due to consumption of a prohibited steroid, which he claims was due to eating contaminated meat while in Malaysia to race last year.
While Iannone has sought to have the sanction overturned entirely, the World Anti-Doping Agency has also appealed to the Court of Arbitration for Sport (CAS) in a bid to have the term extended to four years.
Aprilia Racing CEO Massimo Rivola has publicly backed its embattled rider but, with no resolution in the judicial matter, Smith has been selected for the two Jerez races next month, MotoGP's official website has announced.
For how long the Gresini Racing-run Aprilia squad fields Smith in grands prix this season is not known, with CAS having not announced a date for the appeal hearing.
The former KTM factory rider would likely only race for as long as Iannone is unavailable, given wildcards have been struck out for 2020 due to coronavirus-related restrictions.
Jerez hosts the first two rounds of the premier class season on July 17-19 and July 24-26.