The top American finishers both placed seventh, Laura Thweatt in her marathon debut and Meb Keflezighi, the 2009 champ.
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Biwott was involved in a three-way battle with Geoffrey Kamworor and 2014 runner-up Lelisa Desisa before breaking clear in the last two miles.
Wilson Kipsang — who 12 months ago became the first man to win the London, Berlin and New York Marathons — fell off the pace around the 19-mile mark.
Biwott surged to cross the line in 2:10:34. Kamworor was second. Desisa, winner of the Boston Marathon, faded to third.
Keitany became the first repeat winner since three-time victor Paul Radcliffe in 2007 and 2008.
