Summit Therapeutics is facing a challenging period following the release of data for its investigational cancer treatment, ivonescimab. The company's stock experienced a significant decline as the market reacted to notable differences in the drug's efficacy observed between Asian and Western patient populations. This divergence raises questions about the drug's broader applicability and its potential commercial success, pushing investors to reconsider their positions in the volatile biotechnology sector.
On Monday, September 8, Summit Therapeutics' shares plummeted by 17% from their previous closing price, reflecting investor apprehension. This sharp drop was triggered by new analysis highlighting a considerable disparity in treatment outcomes. Earlier in the year, ivonescimab had fueled optimism, with its robust performance in Chinese patients suggesting it could replicate similar success globally. Initial interim results from the global Harmoni study in May indicated a 48% reduction in tumor progression risk for patients receiving ivonescimab alongside chemotherapy, compared to those on chemotherapy alone.
However, the latest September data presented a stark contrast. Among 165 Western patients, the progression-free survival benefit showed only a 33% risk reduction. This was markedly lower than the 45% reduction observed in Asian patients. Such a substantial 12% gap has caused experts to scrutinize the reliability of other positive cancer trial results emanating from China recently. Furthermore, a lack of statistically significant overall survival benefit at a median follow-up of 29.7 months, despite a 21% reduction in death risk compared to chemotherapy alone, added to the concerns.
Despite these challenges, ivonescimab's journey is not necessarily over. The side effect profile appears manageable, with only a marginal increase in treatment discontinuation rates for patients on ivonescimab plus chemotherapy (7.3%) compared to chemotherapy alone (5%). Summit Therapeutics holds the rights to commercialize ivonescimab outside of China, a license acquired from Akeso. The company's ability to secure regulatory approval in Western markets hinges on whether regulators will overlook the observed geographical inconsistencies, focusing instead on the drug's still-meaningful 33% progression-free survival benefit in Western patients.
The path forward for Summit Therapeutics is complex. While the drug's safety profile is encouraging, the inconsistent efficacy data across different populations makes it difficult to project robust annual sales, particularly given the agreement to share a low double-digit percentage of net sales with Akeso. Despite the recent stock price drop to $19.50 per share, the company still maintains a considerable market capitalization of over $14 billion. This valuation appears lofty for a drug that has yet to demonstrate a definitive overall survival benefit and faces questions regarding its global market potential. Therefore, a cautious approach is warranted, and observing how regulators and oncologists react to these findings before making investment decisions would be prudent.
