A New Blueprint for Immunity: Agenus Data Signals a Shift in Colon Cancer

LEXINGTON, MA – August 26, 2026 – The invisible networks that govern our world are not just digital; some are biological. For decades, the immune system’s network has been notoriously difficult to direct against one of the most common malignancies: colon cancer. Now, newly published data suggests a potential breakthrough in reprogramming that network, offering the prospect of not just treating the disease, but preventing its return.

In a peer-reviewed publication in Clinical Cancer Research, immuno-oncology firm Agenus Inc. unveiled updated results from its Phase 2 NEST trial that have sent ripples through the oncology community. The study, evaluating a combination of two immunotherapies before surgery, reported a stunning finding: after more than two years of follow-up, not a single patient with resectable colon cancer experienced a recurrence. This result is particularly profound because it includes a patient population whose tumors have long been considered “cold” and resistant to this class of drugs.

Remodeling the Battlefield

The central challenge in treating colon cancer with immunotherapy lies in a biological distinction. While a small subset of tumors (dMMR/MSI-H) are highly responsive, they account for only about 15% of cases. The vast majority are mismatch repair proficient (pMMR) or microsatellite stable (MSS), possessing a tumor microenvironment that effectively shields them from immune attack. Historically, these “cold” tumors have derived little to no benefit from checkpoint inhibitors, leaving surgery and chemotherapy as the standard of care.

The NEST trial sought to change that by deploying a combination of botensilimab (BOT) and balstilimab (BAL) before surgery. The strategy is based on a key insight: activating the immune system is most effective when the primary tumor and its surrounding network of lymph nodes are still intact. Botensilimab, the centerpiece of the combination, is a next-generation CTLA-4 inhibitor designed not just to release the brakes on the immune system, but to actively remodel the tumor microenvironment—weeding out suppressive cells and recruiting cancer-killing T-cells.

The results suggest this strategy is working. Among the 22 patients with traditionally resistant pMMR/MSS tumors, 59% had a significant pathologic response, meaning the tumor had substantially shrunk or disappeared by the time of surgery. More impressively, 41% achieved a “major” pathologic response (less than 10% viable tumor remaining), and nearly a third (32%) had a “complete” response, with no detectable cancer cells in the tumor or lymph nodes. These figures stand in stark contrast to the roughly 10-20% major response rates seen with older immunotherapy combinations in this setting.

“NEST provides important context for Agenus’ strategic focus on neoadjuvant BOT+BAL in MSS colon cancer,” said Steven O’Day, M.D., Chief Medical Officer of Agenus. “The findings show BOT+BAL can generate deep tumor responses and immune activation before surgery, without delaying surgery. These results strengthen the rationale for our phase 3 ROBBIN trial.”

The Digital Echo of a Cure

Beyond the tissue-level response, the trial leveraged another invisible network to gauge success: circulating tumor DNA (ctDNA). This “liquid biopsy” technology detects fragments of cancer DNA in the bloodstream, providing a real-time signal of tumor presence. Persistent ctDNA after surgery is a powerful predictor of recurrence.

In the NEST trial, an astounding 88% of patients who had detectable ctDNA at the start of the study had cleared it from their bloodstream before their operation. This molecular remission signal not only preceded the pathological findings but also bolstered the most compelling result of all: the complete absence of cancer recurrences. For context, a landmark study of standard neoadjuvant chemotherapy, FOxTROT, reported a two-year recurrence rate of 16.9%. While cross-trial comparisons require caution, the zero-recurrence figure from NEST over a similar timeframe is a powerful indicator of the combination's potential durability.

“For pMMR/MSS disease, where immunotherapy has historically had limited impact, the combination of pathologic responses, ctDNA clearance, no observed colorectal cancer recurrences at longer follow-up and immune remodeling is highly encouraging,” noted Pashtoon M. Kasi, M.D., M.S., the study’s originator and a medical oncologist at City of Hope Orange County.

A Strategic Pivot to Prevention

The NEST results are more than just a scientific success; they are the foundation of a major strategic pivot for Agenus. The company recently secured an oversubscribed private placement expected to raise up to $340 million, with the funds explicitly earmarked to advance the global Phase 3 ROBBIN trial. This pivotal study will compare neoadjuvant BOT+BAL against the current standard of care in high-risk Stage II and Stage III MSS colon cancer, a population with an estimated addressable market of over $7 billion in the U.S. alone.

The move represents a calculated shift in the entire immuno-oncology paradigm: from treating late-stage, metastatic disease to intervening early with curative intent. “This is about moving the entire battlefield,” commented one independent analyst. “Instead of fighting a difficult war in the metastatic setting, the goal is to prevent the war from ever happening by eliminating the disease and its microscopic seeds before they can spread.”

This early-intervention strategy is gaining traction across oncology, but Agenus's data provides one of the strongest signals yet that it could be viable in a major “cold” tumor type. The approach was also remarkably well-tolerated. Patients in the NEST trial proceeded to surgery without treatment-related delays, and no severe (Grade 4) side effects were observed—a critical factor when treating patients with a potentially curable disease.

With the larger, multicenter NEST3 study now enrolling and the global ROBBIN trial on the horizon, the blueprint for treating early-stage colon cancer may be on the verge of a fundamental redesign. The focus is shifting from simply removing a tumor to re-educating the body’s own defense network, aiming for a future where a cancer diagnosis is not followed by a years-long fear of recurrence, but by a durable, long-term remission.