He recorded a time of two hours five minutes and 38 seconds, after accelerating away from the group of favourites around the 30km mark.
Ethiopian Tadese Tola, winner in 2010, beat another Kenyan Eric Ndiema in a sprint for second. They were 51 seconds behind the winner.
Some's previous personal best of 2:08:29 was set last year in Frankfurt. The 22-year-old also won last year's Brighton Marathon.
Ethiopian Tadese Boru won the women's version in a new race record of two hours 21 minutes and six seconds.
Tadese beat the previous best of 2:21:40 set by compatriot Tirfi Beyene last year.
Merima Mohammed was 128 seconds behind in second with Kenyan Eunice Kirwa (2:23:34) completing the podium.