Shares of Summit Therapeutics (NASDAQ: SMMT) were sinking 22.6% as of 11:10 a.m. ET on Tuesday. This sell-off follows a similar steep decline of 22% on Friday after Summit revealed late-stage data for its lead candidate, ivonescimab, in combination with chemotherapy in treating non-small cell lung cancer (NSCLC).

In a regulatory filing on Friday, Summit referenced top-line data included in a presentation by its Chinese partner, Akeso, at the 2024 American Society of Clinical Oncology (ASCO) annual meeting. Patients receiving ivonescimab in combination with chemotherapy had a median progression-free survival of 7.06 months compared to 4.8 months for patients receiving only chemotherapy. However, 61.5% of patients receiving the combo experienced severe or medically significant treatment-emergent adverse events.

Investors reacted negatively to the late-stage data for ivonescimab. However, there was some good news: China's National Medical Products Administration gave the drug its first regulatory approval on Friday as a second-line treatment for patients with epidermal growth factor receptor (EFGR) mutated, advanced or metastatic NSCLC.

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Source Fool.com