The best performers of the session on the S&P/ASX 200 were Altium Ltd (ASX:ALU), which rose 28.91% or 14.82 points to trade at 66.08 at the close. Meanwhile, Appen Ltd (ASX:APX) added 10.17% or 0.03 points to end at 0.33 and Mesoblast Ltd (ASX:MSB) was up 9.09% or 0.03 points to 0.30 in late trade.