The five lower division survivors, along with Betfred Super League outfit Toronto Wolfpack, have withdrawn leaving 10 top-flight teams remaining in the competition.
Toronto announced last week they will not complete their Super League campaign this year and the Betfred Championship and League One seasons have been abandoned, due to the coronavirus pandemic.
Two newly-drawn sixth round ties will be played at John Smith’s Stadium in Huddersfield on Saturday, August 22, with the other six sides receiving a bye to the quarter-finals on the weekend of September 18-20.
Both sixth round ties will be televised by the BBC. Sky and the BBC will share quarter-final coverage.
The revised draw will take place later this week.
A statement from the Rugby Football League confirmed: "Following the withdrawal from the competition of Toronto Wolfpack and the five Betfred Championship and League One clubs who had earned places in the last 16, the RFL board was faced with an unprecedented set of circumstances.
"Having considered all the options and having received the support of the BBC and Coral, the RFL board decided that a redraw of the sixth round is the best and fairest way of proceeding."
The semi-finals will be held on Saturday, October 3, with both matches shown live on the BBC.
The final will follow two weeks later, with the venues for those matches to be confirmed in the coming weeks.
RFL chairman Simon Johnson said: “As with so much of sport and society in recent months, we have faced unique challenges in reshaping the Coral Challenge Cup.
“We are wholly sympathetic to the Championship and League One clubs who had earned places in the sixth round, but for various reasons and quite understandably do not now feel it would be in their best interests to continue in the competition.
“We believe that the fairest way to proceed from here is to redraw, meaning two sixth round ties and the other six clubs receiving a bye to the quarter-finals. We hope that supporters and clubs will understand this decision."
Johnson added: “Given the quality of the clubs remaining in the competition, it means we are guaranteed some mouthwatering ties.
“We would like to place on record our gratitude to Coral, the BBC and the clubs for their recognition that we have had to be flexible given such an unusual situation.
“We are very pleased that the Coral Challenge Cup will continue and the sport can look forward to some more memorable occasions and fascinating chapters in this historic competition.”
Leeds Rhinos had been due to play host to Hull KR in round six.
Other ties were Wakefield Trinity v Featherstone Rovers, York City Knights v Castleford Tigers, Sheffield Eagles v Hull, Newcastle Thunder v Toronto Wolfpack, Salford Red Devils v St Helens, Widnes Vikings v Catalans Dragons and Wigan Warriors v Warrington Wolves.
Sheffield confirmed on Monday they would not play their tie against Hull and York announced their withdrawal just 30 minutes before the RFL's statement on Tuesday morning, both siting player welfare as a mahor factor.
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