Kenya's half marathon world record holder Abraham Kiptum has been suspended from competition following an athlete biological passport violation.
The 29-year-old had been due to compete in Sunday's London Marathon.
Kiptum completed the Valencia half marathon in 58 minutes 18 seconds in October, five seconds quicker than the record set by Zersenay Tadese in 2010.
"We have a zero-tolerance policy on doping," said London Marathon event director Hugh Brasher.
"We recently announced a groundbreaking extensive intelligence-driven testing programme. This shows the programme is working. Cheats will be caught and there is no place for them in marathon running."
London Marathon organisers say Kiptum has left the city following the suspension issued by the Athlete Integrity Unit.
The athlete biological passport programme collects and compares biological data to spot discrepancies over time that suggest possible doping.
The build-up to this year's marathon has already been overshadowed by a dispute between distance running greats Sir Mo Farah and Haile Gebrselassie, following an altercation surrounding an alleged theft at Gebrselassie's hotel in Ethiopia.