The end of July is the target for the start of the MotoGP season after races in Germany, the Netherlands and Finland were cancelled due to the coronavirus pandemic.
It was announced on Wednesday that the German Grand Prix at the Sachsenring on June 21 and the famous Assen round a week later will not go ahead.
The Grand Prix of Finland at the new Kymi Ring on July 12 has also been removed from the calendar.
Organisers are hoping they can salvage the season, with the Czech Grand Prix in Brno on August 9 next on the original schedule that has not yet been called off.
Carmelo Ezpeleta, chief executive of organisers and promoters Dorna Sports, said: "It is with great sadness that we announce the cancellation of these three important Grands Prix on the MotoGP calendar.
"The German GP is raced on a truly unique track with an incredible history, and the KymiRing is an exciting new venue set to welcome Grand Prix motorcycle racing back to Finland for the first time since 1982.
"And the iconic TT Circuit Assen had the unique honour of being the only venue to have held a round of the motorcycle racing Grand Prix World Championship every year, uninterrupted, since the Championship began in 1949.
"On behalf of Dorna I would like to thank all the fans for their understanding and patience as we wait for the situation to improve. We very much look forward to returning to the Sachsenring and the TT Circuit Assen in 2021, and eagerly await the Grand Prix debut of the new KymiRing next season."
It remains to be seen whether races in Spain, France and Italy that were postponed can be rearranged.
Ezpeleta has said Dorna Sports are "optimistic" of staging a season starting in either late July or early Augugst that would finish on schedule in November.