Grandmaster Wesley so was held to his second straight draw but still maintained the solo leadership after seven rounds in the Tata Steel Masters 2017 in Wijk aan Zee, Netherlands.
So split the point with Ukrainian GM Pavel Eljanov after 38 moves of Giuoco Piano to hike his tally to 5 points on three wins and four draws.
The Filipino-born So, who represents the United States, remained half a point ahead second-running Eljanov, GM Magnus Carlsen of Norway, and Chinese GM Wei Yi.
Carlsen, the reigning world champion, drew with hometown bet GM Anish Giri, while Wei dumped GM Loek Van Wely of the Netherlands for his second straight victory.