Immuneering Corporation (Nasdaq: IMRX) reported updated Phase 2a clinical results for its oral MEK inhibitor atebimetinib (IMM-1-104) combined with modified gemcitabine/nab-paclitaxel (mGnP) in first-line metastatic pancreatic cancer, showing an exceptional 64% overall survival (OS) at 12 months — nearly double the historical benchmark for standard chemotherapy.

In data from 34 patients with a median follow-up of approximately 13.4 months, the atebimetinib+mGnP regimen also demonstrated:

• 94% OS at 6 months and 83% OS at 9 months, both indicating durable survival separation versus historical gemcitabine/nab-paclitaxel benchmarks.
• Median progression-free survival (mPFS) of 8.5 months, compared with ~5.5 months typical for standard care.
• Overall response rate (ORR) of 39% and disease control rate (DCR) of 81%, signaling encouraging tumor control metrics.
• Median overall survival not yet reached as of the data cutoff. Immuneering’s Chief Medical Officer characterized the survival results as “extraordinary” in a disease where effective first-line outcomes have historically been elusive. The safety profile was consistent with expectations for pancreatic cancer therapy, with no new safety signals observed.

The company confirmed alignment with both the US FDA and the EU’s EMA on a pivotal Phase 3 registrational trial — MAPKeeper 301 — which is now planned to begin dosing mid-2026. This global study is expected to enroll approximately 510 patients and will compare atebimetinib+mGnP directly against the current standard-of-care regimen, with overall survival as the primary endpoint and topline data anticipated in mid-2028.

Immuneering also flagged additional near-term catalysts, including circulating tumor DNA analysis planned for presentation at a major scientific meeting in Q2 2026 and expanded survival data from a cohort of more than 50 patients expected in 1H 2026.

Research context

Discovered by Immuneering, atebimetinib is designed as an oral, once-daily “deep cyclic inhibitor” of MEK1/2, key kinases in the MAPK/ERK signaling pathway, which is a central driver of cell proliferation and survival in many cancers, especially those with RAS or RAF mutations, and particularly in pancreatic cancer, where KRAS mutations are found in over 90% of PDACs, driving MAPK pathway activation.

Unlike traditional MEK inhibitors that provide continuous inhibition, atebimetinib delivers intermittent, deep inhibition, theorized to maximize cancer cell death while allowing normal cells to recover, potentially reducing toxicity and overcoming resistance mechanisms. The drug’s primary development focus is on pancreatic ductal adenocarcinoma (PDAC), with potential expansion to other MAPK-driven solid tumors.

Pancreatic cancer remains one of the most challenging solid tumors, with limited effective first-line options. If confirmed in a larger randomized setting, atebimetinib’s survival benefits could mark a notable advance in care for patients with metastatic disease.