on Lyell Immunopharma Inc. (NASDAQ: LYEL) stock is up on Monday as the company is providing an update on the safety profile of its LYL273 treatment in a Phase 1 clinical trial for relapsed or refractory metastatic colorectal cancer (mCRC).
New GI Prophylaxis Regimen Reduces Severe Side Effects
As of May 5, 2026, data cutoff, 19 patients had been enrolled across the first two dose levels of the U.S. trial, which is evaluating LYL273 in patients with third-line or later metastatic colorectal cancer.
Ten patients received a newly implemented gastrointestinal prophylaxis regimen consisting of infliximab, vedolizumab, and budesonide, alongside a standardized safety management plan.
According to the company, the approach reduced the incidence of Grade greater than 2 diarrhea or colitis to 10% among patients receiving prophylaxis, compared with 55% in those who did not receive the regimen.
The company said none of the patients treated under the prophylaxis protocol experienced Grade 3 or higher cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS). No new adverse events of interest were reported.
Lyell also noted that the prophylactic treatment did not appear to affect GCC-CAR-positive cell expansion, with similar levels of maximum expansion and overall exposure observed between the two patient groups.
Dose escalation remains ongoing, and the maximum tolerated dose has not yet been identified.
Trial Expands Into Phase 1/2 Design
Lyell Immunopharma recently announced updates from its U.S. Phase 1 clinical trial evaluating LYL273, which has been amended to a Phase 1/2 design to allow for a seamless transition into a pivotal trial.
The trial aims to determine the maximum tolerated dose and has reported a 50% overall response rate in patients treated under a new gastrointestinal prophylaxis regimen.
Next Steps
Lyell expects to report additional Phase 1 clinical data, including clinical outcomes, during the second half of 2026. The company also anticipates holding an End-of-Phase 1 meeting with the FDA later this year.
LYEL Price Action: Lyell Immunopharma shares were up 1.09% at $12.10 at the time of publication on Monday, according to Benzinga Pro data.
Image via Shutterstock/ K_E_N
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