Immuneering's Cancer Drug Gets Green Light for Pivotal Phase 3 Trial

NEW YORK, NY – December 17, 2025 – In a significant development for one of the deadliest forms of cancer, Immuneering Corporation announced today it has received alignment from both U.S. and European regulators to advance its lead drug candidate, atebimetinib, into a global Phase 3 trial for first-line metastatic pancreatic cancer. The news provides a tangible beacon of hope for patients battling a disease with notoriously poor outcomes and limited treatment options.

The Cambridge, Massachusetts-based company confirmed it has completed its End-of-Phase 2 discussions with the U.S. Food and Drug Administration (FDA) and received positive scientific advice from the European Medicines Agency (EMA). This dual regulatory alignment validates the design of the upcoming pivotal trial, dubbed MAPKeeper 301, which is on track to begin enrolling patients in mid-2026.

“We are very pleased with our interactions with both the FDA and EMA, which we believe speaks to the compelling data we have generated to date in first-line pancreatic cancer, as well as the strength and simplicity of our proposed Phase 3 trial for atebimetinib,” said Ben Zeskind, Ph.D., Co-Founder and Chief Executive Officer of Immuneering.

Confronting a Formidable Foe

Pancreatic cancer remains a monumental challenge in modern oncology. With a five-year survival rate often languishing in the single digits for metastatic disease, it stands as one of the most lethal cancers worldwide. The current standard-of-care for patients newly diagnosed with metastatic pancreatic ductal adenocarcinoma (PDAC) typically involves intensive chemotherapy regimens like FOLFIRINOX or a combination of gemcitabine and nab-paclitaxel (GnP).

While these treatments can extend life, their efficacy is limited. Median overall survival with these regimens hovers between 8 and 12 months, a stark reality that has seen little improvement for decades. Historical data for the GnP combination, which will serve as the comparator in Immuneering's upcoming trial, shows a six-month survival probability of approximately 67%. Furthermore, these chemotherapies are often accompanied by severe side effects that can drastically reduce a patient's quality of life, making the search for more effective and better-tolerated therapies a paramount goal for the medical community.

The FDA has previously acknowledged this profound unmet need by granting atebimetinib both Fast Track and Orphan Drug designations for pancreatic cancer, regulatory incentives designed to expedite the development and review of promising new treatments for serious or rare conditions.

A Novel Mechanism for a Notorious Pathway

Atebimetinib represents a new strategy against a well-known driver of cancer growth. It is an oral, once-daily drug belonging to a novel class of medicines Immuneering calls "Deep Cyclic Inhibitors." The drug targets MEK, a key protein in the MAPK signaling pathway, a cellular communication network that is hyperactive in over 90% of pancreatic cancers, often due to mutations in the RAS gene.

Unlike conventional MEK inhibitors, which have often been hampered by dose-limiting toxicities, atebimetinib's deep cyclic inhibition is designed to shut down the pathway more profoundly but intermittently. This unique dosing strategy aims to outpace the cancer cells' ability to develop resistance while providing a "drug holiday" that may mitigate the harsh side effects, such as skin rash and gastrointestinal issues, that plague other drugs in its class. The goal is to create a treatment that is not only more effective but also durable and tolerable enough for long-term administration.

“The constructive guidance from both agencies validates our scientific approach and our understanding of the unmet need in first-line metastatic pancreatic cancer,” said Igor Matushansky, M.D., Ph.D., Chief Medical Officer of Immuneering. “We look forward to advancing atebimetinib into Phase 3 and working with investigators worldwide to bring this potentially transformative therapy to patients as expeditiously as possible.”

Encouraging Data Ignites Hope

The regulatory green light follows a stream of encouraging data from Immuneering's Phase 2a study. In results shared earlier this year, atebimetinib, when combined with a modified GnP chemotherapy regimen, demonstrated a remarkable 94% overall survival rate at the six-month mark in a cohort of 34 patients. This figure stands in sharp contrast to the 67% six-month survival seen in historical controls for GnP alone.

The positive signals extended to other key metrics. The trial showed a six-month progression-free survival rate of 72%, compared to 44% in historical data, and an overall response rate of 39%, versus 23% for the standard of care. Critically, the combination was reported to have a favorable tolerability profile, a key aspect of its potential differentiation. The company has also announced it will provide a further update on overall survival data from this study in the coming weeks.

The potential of this combination has been recognized by leading experts in the field. “New therapies for pancreatic cancer are urgently needed,” said Eileen M. O’Reilly, MD, an oncologist at Memorial Sloan Kettering Cancer Center, in the company's press release. “The phase IIa data of atebimetinib and chemotherapy shows a promising signal. I am excited to see this combination move forward to a randomized phase III evaluation.”

The Path to Approval: A Global Pivotal Trial

The upcoming MAPKeeper 301 trial will be a large-scale, global study designed to definitively answer whether atebimetinib can become a new standard of care. The trial will enroll approximately 510 patients with first-line metastatic PDAC. Patients will be randomized to receive either atebimetinib plus mGnP or the standard GnP regimen alone.

The primary goal of the trial is to demonstrate a statistically significant improvement in overall survival. Secondary objectives include measuring progression-free survival, tumor response rates, and quality of life. With the first patient expected to be dosed in mid-2026, Immuneering anticipates sharing topline results from this pivotal study in mid-2028.

Executing such a large and lengthy trial requires substantial financial resources. Immuneering has shored up its balance sheet, stating that its current cash reserves are sufficient to fund operations into 2029, seeing it well past the expected trial readout. This financial stability, combined with the clear regulatory path and promising early data, positions the company to fully pursue this high-stakes, high-reward endeavor. While the competitive landscape for oncology drugs is fierce, a successful outcome for atebimetinib in this notoriously difficult-to-treat cancer could transform the patient journey and establish a new therapeutic benchmark.