Van Niekerk captured the 200-metre title, and Simbine placed second in the 100m.
The 24-year-old Van Niekerk, who is the reigning World and Olympic champion in the 400m, clocked a winning time of 19.84 on a temporary built track to beat runner-up BeeJay Lee (20.17).
Because the competition was run on a straight line instead of the traditional curved track and field surface the time will not be listed in 2017 International Association of Athletics Federation (IAAF) records.
“I still have a lot of work ahead of me,” said Van Niekerk, who will run the 200m next weekend in Kingston, Jamaica. “But it is a positive result.”
Trinidad and Tobago track star Keston Bledman bolted to gold when he outsprinted sprinted Simbine to the line in 10.21 seconds to capture the men’s 100m title.
In the closest of finishes, Bledman and second-placed Simbine were credited with the same time. It was Bledman, though, who got the edge in the photo finish, edging his South African rival by one-thousandth of a second.