Summit Therapeutics said its phase 2 AK112-206 study in first-line metastatic colorectal cancer produced an objective response rate of 70.8% in evaluable patients receiving ivonescimab plus mFOLFOX6 chemotherapy, based on 48 patients with response data. The trial enrolled 49 patients total, randomized evenly between the two dose levels, 24 patients in the 10 mg/kg arm and 25 in the 20 mg/kg arm.
The higher dose showed the stronger durability signal. At 9 months, the landmark duration-of-response estimate was 79.1% in the 20 mg/kg arm versus 41.5% in the 10 mg/kg arm, a gap of 37.6 percentage points. The 20 mg/kg group also posted a 9-month progression-free survival rate of 76.1%.
Safety data showed 20.4% of patients experienced serious treatment-related adverse events tied to ivonescimab or chemotherapy. There were no ivonescimab-related deaths and one ivonescimab-related discontinuation. All patients had at least one treatment-emergent adverse event, with the most common being decreased neutrophil count, decreased white blood cell count and anemia.
The study’s median follow-up was 9.9 months for the 10 mg/kg group and 9.8 months for the 20 mg/kg group. Summit said the 20 mg/kg arm produced more durable responses than the lower-dose arm, while the overall response rate was consistent across dose levels.
The company also pointed to its ongoing phase 3 HARMONI-GI3 trial in first-line unresectable metastatic colorectal cancer, comparing ivonescimab plus mFOLFOX6 with bevacizumab plus mFOLFOX6. As a result of these announcements, the company's shares have moved -12.26% on the market, and are now trading at a price of $15.39. Check out the company's full 8-K submission here.
