* Rules bar doping offenders from winning title
* Kenyan can't defend London marathon victory
* Sumgong's agents say shocked by the news (Adds quotes from Sumgong's agents)
LONDON, April 7 (Reuters) - The Abbott World Marathon Majors (WMM) will hold back on naming a women's champion until after the conclusion of the doping case involving series leader Jemima Sumgong.
Sumgong, who last year became the first Kenyan woman to win Olympic gold in the marathon, tested positive for the banned blood-booster EPO (erythropoietin) in an out-of-competition test carried out by the sport's governing body.
"While we are distressed to learn of the reports of Jemima Sumgong's positive drug test, if true, they indicate that we are gaining ground in our long-standing fight against doping," Tim Hadzima, general manager of the consortium, said in a statement.
"Given our policies, until the conclusion of Jemima Sumgong's case and any potential appeal process, we will not name a Series X women's champion," he added.
Sumgong leads the standings for Series X, which concludes at the April 17 Boston Marathon.
Athletics Kenya said it was awaiting full information on Sumgong's violation and would give no further comment on it for now.
"In the meantime, Athletics Kenya frowns upon and condemns in the strongest terms any case of anti-doping rule violation whether in Kenya or elsewhere in the world," it said in a statement.
Sumgong's agents Rosa e Associati said in a statement: "If the facts (are) fully established, this has to be considered as a dramatic moment for Kenya... The news has shocked us and we distance ourselves from what happened...
"The case of Jemima is the proof that controls begin to work better: this is the only positive note in a situation that we consider serious and complex and that encourages us to redouble the efforts to fight doping in Kenya..."
WMM rules state that athletes found guilty of breaking anti-doping rules enforced by the governing body IAAF, World Anti-Doping Agency (WADA), national federations or any of the series' individual races cannot win a title.
"The Abbott World Marathon Majors is committed to eradicating doping and we will continue to lead the way in introducing and campaigning for aggressive measures," Hadzima said.
"To that end, we recently, in conjunction with the IAAF, built and funded one of the largest targeted testing pool of athletes, with an aim of requiring more than 150 individuals to submit to out-of-competition testing a minimum of six times a year."
Sumgong, 32, will not be defending her London marathon title on April 23, the organisers announced on Friday.
"She is currently suspended from competition pending the B test and the outcome of the investigation," chief executive Nick Bitel said in a statement. "Sumgong will therefore not run in London on 23 April to defend the title she won last year."
If Sumgong's B sample is confirmed as positive and she is subsequently banned, it would be a massive blow for Kenya, where her Rio victory was greeted with near-delirium after a long barren spell over the classic distance at the Olympics. (Reporting by Amlan Chakraborty in New Delhi and Isaack Omulo in Nairobi; editing by George Obulutsa/Mark Heinrich)