On April 20, 2026 Immuneering Corporation (Nasdaq: IMRX), a late-stage clinical oncology company focused on keeping cancer patients alive and helping them thrive, reported the presentation of new genetic data at the 2026 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting taking place April 17-22, 2026 in San Diego, CA.
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"Atebimetinib is designed to promote survival by three mechanisms: shrinking tumors durably, preserving body mass by counteracting muscle wasting, and maintaining performance status by maximizing tolerability," said Ben Zeskind, Ph.D., Chief Executive Officer of Immuneering. "We believe these characteristics have the potential to both yield the best survival in the first-line, and to give patients the best chance of reaching and benefitting from second-line treatment. Today’s data at AACR (Free AACR Whitepaper) add genetic rationale to support atebimetinib’s observed durable tumor shrinkage and its optimal use in the first-line setting by showing that the most common RAS-inhibitor resistance mechanisms are rarely seen in atebimetinib-treated patients."
Inhibitors of RAS, RAF, or MEK often provide only temporary benefit due to pervasive resistance, as tumors acquire new mutations or mechanisms of escape within the MAPK pathway. Atebimetinib, a novel Deep Cyclic Inhibitor of MEK, is engineered to mitigate the selective pressure that typically drives these resistance mechanisms, with the goal of more durable anti-tumor activity. Immuneering presented circulating tumor DNA (ctDNA) data from 123 patients treated with atebimetinib, showing that acquired MAPK pathway alterations are rarely seen. These findings suggest that Deep Cyclic Inhibitors have the potential to overcome the limitations of conventional MAPK inhibition and provide a more sustained clinical benefit for patients, while potentially preserving sensitivity to subsequent treatments.
Key Findings from the AACR (Free AACR Whitepaper) Presentation:
Rare MAPK pathway reactivation: Across 86 patients treated with atebimetinib monotherapy and 37 patients treated in combination with chemotherapy, emergent and acquired mutations rarely converged on the RAS/MAPK pathway, in contrast to what is commonly observed with chronic RAS-targeted therapies.
Diffuse, non-convergent resistance patterns: Emergent resistance following atebimetinib treatment utilized a variety of non-MAPK pathways, rather than converging on a single escape mechanism.
Limited early adaptive resistance: ctDNA analysis showed minimal early molecular evolution during treatment, indicating that atebimetinib is not driving adaptive resistance and may impose less selective pressure than continuous pathway inhibition.
Taken together, the data position atebimetinib as a differentiated MEK inhibitor with potential to drive deep and durable antitumor activity.
"Our AACR (Free AACR Whitepaper) data further validate the scientific foundation of our platform, demonstrating that Deep Cyclic Inhibition can fundamentally alter how tumors evolve under therapy, unlocking opportunities to improve treatment durability," said Brett Hall, Ph.D., Chief Scientific Officer of Immuneering. "Deep Cyclic Inhibition of MEK avoids the continuous selective pressure that typically drives tumors to become resistant to treatment via reactivation of the MAPK pathway. This, combined with atebimetinib’s tolerability profile, has the potential to improve depth and durability of response in a broad range of cancers, starting with first-line pancreatic cancer."
Poster Presentation Details:
Title: Atebimetinib’s Deep Cyclic Inhibition of MEK Constrains MAPK-Axis Adaptive and Acquired Alterations in Patients with RAS-Mutant Tumors
Session Category: Experimental and Molecular Therapeutics
Session Title: Targeting Drug Resistance 2: RAS Signaling
Poster Number: 1873
Poster Board Number: 6
Session Date: April 20, 2026
Session Time: 9:00 AM – 12:00 PM ET
Location: Poster Section 19
The poster is available on the publications section of Immuneering’s website at View Source
Immuneering has guided to dosing the first patient in its pivotal Phase 3 MAPKeeper 301 trial of atebimetinib plus modified gemcitabine/nab-paclitaxel (mGnP) in patients with first-line metastatic pancreatic cancer in mid-2026. In the second half of the year, the company expects to dose the first patient in a Phase 2 trial of atebimetinib plus Libtayo in patients with first-line RAS-mutant non-small cell lung cancer.
(Press release, Immuneering, APR 20, 2026, View Source [SID1234664541])