Aprilia rider Andrea Iannone has been banned for 18 months after testing positive for a banned substance last year.
Iannone was provisionally suspended in December after returning an adverse finding of a non-specified substance, later confirmed to be an illegal anabolic agent, in a urine sample taken at last year's Malaysian Grand Prix.
The Italian requested analysis of his B sample, which confirmed the initial result.
The FIM International Disciplinary Court (CDI) confirmed on Wednesday that the 30-year-old has been given a ban backdated to December 17, meaning it will run until June 16, 2021.
Iannone will miss the 2020 season, which is currently suspended due to the coronavirus pandemic, and the early rounds of next year.
MotoGP added in a statement that Iannone was also officially disqualified from last year's races in Malaysia and Spain, although he did not finish either.
Iannone has 21 days to file an appeal at the Court of Arbitration for Sport.
The next scheduled MotoGP race is at Le Mans on May 17, with the first five rounds having been called off amid the spread of COVID-19.