The International Motorcycle Federation (FIM) handed Iannone an 18-month ban after ruling he had unintentionally ingested the banned steroid drostanolone in meat he had eaten.

The Italian tested positive for the substance in an in-competition test at the 18th round of the MotoGP season in Sepang last November.

WADA appealed as it believed the sanction was too lenient and asked for a four-year ban.

In a statement, CAS said Iannone, who has has competed in MotoGP since the 2013 season and earned victory at the Austrian Grand Prix in 2016, had failed to prove he ingested the banned substance in contaminated meat and confirmed an anti-doping rule violation had been committed.

The CAS panel found Iannone had "failed to establish neither the precise type of meat he had consumed nor the origin of said meat".

"Moreover, the panel found that neither Andrea Iannone nor his experts were able to establish specifically that there was an issue of meat contamination by drostanolone in Malaysia," the CAS said.

Iannone "essentially left the Panel with protestations of innocence, his clean record and his alleged lack of incentive to dope", which "were insufficient to establish, on a balance of probability that Andrea Iannone’s ADRV was not intentional", the CAS added.

Iannone had been provisionally suspended on December 17 last year after the FIM was notified of the positive test.

His four-year ban from the sport will begin on that date and is due to conclude in December 2023.

The decision from the CAS could spell the end of the 31-year-old's career.