Summit Therapeutics PLC (NASDAQ: SMMT) experienced a surprising 5.43% surge in its stock price during Monday's trading session, despite reporting mixed results from a Phase 3 trial of its experimental lung cancer drug, ivonescimab.

The company announced on Sunday that data from the Phase 3 HARMONi trial showed "consistent, clinically meaningful improvement" in progression-free survival for patients with certain types of metastatic non-squamous non-small cell lung cancer when ivonescimab was combined with chemotherapy. However, a report from medical news outlet Stat News highlighted a concerning discrepancy: patients treated with the drug candidate in North America and Europe experienced faster disease progression than those treated in China.

The unexpected stock price increase, despite the potentially complicating factor for US and European drug approvals, suggests that investors may be focusing on the overall positive aspects of the trial results or speculating on potential solutions to address the geographical differences in efficacy. It's also possible that other factors, such as market conditions or speculation, could be influencing the stock's performance. As the situation develops, investors and analysts will likely be closely watching for further updates from Summit Therapeutics regarding their plans to address these mixed results and navigate the regulatory landscape.