Shares of Immuneering Corporation (NASDAQ: IMRX) experienced a notable decrease in premarket trading following the release of updated clinical trial results for its investigational agent atebimetinib (IMM-1-104). The company reported findings from an ongoing Phase 2a study assessing the efficacy of atebimetinib in combination with a modified chemotherapy protocol consisting of gemcitabine and nab-paclitaxel (mGnP) for patients diagnosed with first-line pancreatic cancer.
The data encompass outcomes from 34 participants with a median follow-up exceeding 13 months. The trial compared survival metrics between those receiving the chemotherapy regimen alone and those treated with the combination including atebimetinib.
Overall survival (OS) at 12 months for patients receiving only the chemotherapy combination was reported at 35%. In contrast, the cohort administered atebimetinib alongside mGnP demonstrated a markedly higher survival rate of 64% at the same interval.
Further, when evaluating earlier time points, the investigational arm exhibited an OS of 83% at 9 months versus approximately 47% for the chemotherapy-alone group. At 6 months, the combination therapy had a 94% survival rate compared to 67% for chemotherapy, underscoring a consistent survival advantage for the atebimetinib-inclusive regimen.
Median progression-free survival (PFS), which measures the time during and after treatment that a patient lives without disease progression, was 8.5 months in the experimental group compared to 5.5 months with chemotherapy alone. Moreover, the confirmed Overall Response Rate (ORR) at 12 months stood at 39% for the combination therapy versus 23% with chemotherapy.
Safety data as of the cutoff date, December 15, 2025, indicated that atebimetinib administered at 320 mg once daily combined with mGnP was generally well-tolerated among the first-line pancreatic cancer patients in the trial. However, two categories of adverse events reaching Grade 3 severity were observed in over 10% of participants, reflecting known side effect profiles requiring clinical management.
Looking ahead, Immuneering anticipates reporting data from an expanded trial cohort of 50 pancreatic cancer patients treated with the atebimetinib plus mGnP combination during the first half of 2026. This broader dataset will provide further insight into the regimen's efficacy and safety.
The company is also planning to initiate dosing for a pivotal Phase 3 trial, referred to as MAPKeeper 301, evaluating atebimetinib plus mGnP in the first-line pancreatic cancer setting around mid-2026. This study represents a critical step in the development program potentially leading to regulatory approval.
Additionally, Immuneering expects to commence dosing the first patient in a separate trial exploring atebimetinib in combination with Regeneron Pharmaceuticals Inc.'s (NASDAQ: REGN) Libtayo (cemiplimab) for non-small cell lung cancer during the second half of 2026, expanding the therapeutic scope of the candidate.
From a financial standpoint, Immuneering reaffirmed in December 2025 that its existing cash reserves and equivalents are sufficient to sustain operational activities through 2029 based on current business plans. This financial position offers a runway to support ongoing clinical development milestones.
In market reactions, IMRX shares declined by approximately 26.53% to $6.12 in early Thursday trading, reflecting investor caution despite the promising clinical data. Benzinga Pro data confirm the premarket stock movement amid the announcement.
Overall, while the updated Phase 2a results for atebimetinib show meaningful improvements in survival outcomes versus chemotherapy in first-line pancreatic cancer, the significant drop in share price highlights market sensitivity to clinical development risks and valuation uncertainties inherent in biotechnology stocks.