Summit shares tumble on mixed data for lung cancer drug

By Christy Santhosh

Sept 8 (Reuters) - Summit Therapeutics SMMT.O shares slumped nearly 20% on Monday following mixed results from patient subgroups in a longer-term follow-up of its late-stage lung cancer drug trial.

The study results, reported on Sunday, showed that the drug, ivonescimab, had stronger benefit in patients with non-small cell lung cancer (NSCLC) in China, compared with those from North America and Europe.

While the study continues to read positively in aggregate, the details on the Asian vs. non-Asian subgroups were worse than expected, said Piper Sandler analyst Kelsey Goodwin.

Last year, Summit shares hit a record high after the company and its partner Akeso 9926.HK reported results from a trial in China, which showed patients who took ivonescimab had better survival rates than those on Merck's MRK.N blockbuster Keytruda.

However, shares dropped 30% in May after global data showed an overall survival benefit trend but failed to reach statistical significance.

Analysts have noted that the drug's miss on overall survival could be a roadblock to potential U.S. approval.

"If you have immature, short follow-up in Western patients, added to the much, much more mature data out of China, you dampen the effect short term. But that doesn't mean that long term, that's going to be the case," said Jack West, vice president of clinical development at Summit.

The company plans to initiate more trials exploring the drug for lung cancer and other diseases. Ivonescimab has already been approved in China for NSCLC.

Like Keytruda, Summit's therapy is an antibody designed to block a protein called PD-1, which helps the body's immune system to fend off cancer.