1. REC-4881 shows 75% efficacy in reducing polyp burden after 12 weeks. 2. 82% of patients maintained reduced burden 12 weeks post-treatment. 3. REC-4881 is first MEK1/2 inhibitor for familial adenomatous polyposis. 4. Engagement with FDA planned in 1H26 for potential registration. 5. FAP affects over 50,000 patients across US and EU.
FAQ
Why Bullish?
The clinical efficacy shown by REC-4881 bolsters investor confidence. Historical trends indicate shares often rise after positive trial results, as seen in similar biotech cases.
How important is it?
The results from the REC-4881 trial are crucial for RXRX. Success in trials can significantly influence stock value and market perception, particularly as FAP has no current treatment options.
Why Short Term?
The upcoming FDA engagement and trial results will likely affect RXRX's stock in the next few months. Similar biotech firms often see immediate impacts post-announcement of efficacy.
Promising Phase 1b/2 Results from REC-4881 Trial for Familial Adenomatous Polyposis (FAP)
Published on December 8, 2025
Overview of REC-4881 Trial Results
Recursion (Nasdaq: RXRX), a clinical-stage TechBio company, has reported positive outcomes from its ongoing Phase 1b/2 clinical trial, known as the TUPELO trial, evaluating REC-4881. This investigational allosteric MEK1/2 inhibitor targets familial adenomatous polyposis (FAP), a hereditary condition leading to colorectal cancer.
In the trial, REC-4881 (4 mg QD) demonstrated rapid clinical activity, with **75%** of evaluable patients experiencing reductions in total polyp burden after 12 weeks of treatment. Moreover, a **43%** median reduction in polyp burden was noted among participants (n=12). Significantly, following a 12-week off-therapy period (Week 25), **82%** of evaluable patients (9 of 11) maintained a durable reduction, with a **53%** median decrease observed from baseline.
Clinical Implications of the Findings
The natural history analysis conducted alongside the trial indicates a stark contrast between treated and untreated FAP patients. It revealed that **87%** of untreated FAP patients, resembling inclusion criteria of the TUPELO trial, experienced an increase in annual polyp burden. Notably, only **10%** remained stable and **3%** showed a modest decrease, highlighting the progressive nature of the disease (n=55).
Additionally, **40%** of participants (4 out of 10) achieved a clinically meaningful improvement in Spigelman stage, an important measure for assessing upper gastrointestinal disease severity.
Safety Profile and Next Steps
The safety profile of REC-4881 aligns with expectations for MEK1/2 inhibition. Most treatment-related adverse events were classified as Grade 1 or 2. Notably, Grade 3 events occurred in **15.8%** of safety-evaluable patients, with no Grade ≥4 treatment-related adverse events (TRAEs) reported to date.
Recursion plans to engage with the FDA in the first half of 2026 to outline potential registration pathways for REC-4881. In conjunction, the company intends to broaden the participant age criteria from **≥55** to **≥18** years and further refine the dosing regimen.
Expert Perspectives on REC-4881
Jessica Stout, D.O., Assistant Clinical Professor at the University of Utah School of Medicine and Principal Investigator of the TUPELO study, emphasized the significance of the durable reductions in polyp burden. “Given the near-100% lifetime risk of colorectal cancer and the lack of approved therapies, these results offer considerable hope,” she stated. “REC-4881 has the potential to become a vital non-surgical option for patients suffering from this debilitating condition.”
Chris Gibson, Ph.D., Co-Founder and CEO of Recursion, noted, “The favorable Phase 2 data validate the Recursion OS, demonstrating how AI-driven insights can translate into effective therapeutic solutions in diseases lacking approved pharmacotherapies.”
Background on Familial Adenomatous Polyposis (FAP)
FAP is a hereditary condition characterized by inactivating mutations in the APC gene. It can lead to the formation of hundreds to thousands of polyps in the gastrointestinal tract, with untreated individuals facing a nearly **100%** risk of developing colorectal cancer before age 40. As there are currently no approved medical therapies for this condition, patients often undergo multiple surgeries, including colectomy, which do not resolve the underlying disease biology and do not prevent future polyp formation.
Approximately **50%** of patients will require additional surgical interventions, leading to a marked decline in quality of life. FAP affects an estimated **50,000** individuals across the US and EU5 (France, Germany, Italy, Spain, and the UK).
Conclusion
The positive results from the REC-4881 TUPELO trial represent a significant advancement in the treatment landscape for FAP. The findings not only highlight the potential efficacy of REC-4881 but also underscore the importance of continued development in this critical area of unmet medical need.