A Six-Year Victory and the Dawn of Biopsy-Free Cancer Therapy

LONDON, UK – June 09, 2026 – In the world of oncology, a single patient outcome is rarely a revolution. But sometimes, it’s a powerful signal of a seismic shift on the horizon. This week, a story emerged from the European Association for Cancer Research (EACR) Congress that carries that weight: a patient with a notoriously difficult-to-treat metastatic colorectal cancer is not just alive, but completely disease-free more than six years after treatment with a novel immunotherapy.

The data, presented by Treos Bio, centers on its lead candidate, PolyPEPI1018. While this remarkable long-term survival is a headline in itself, it’s the technology humming beneath the surface that represents a more profound strategic leap. The company is advancing a dual approach—combining scalable, off-the-shelf vaccines with a platform that enables rapid personalization without the need for an invasive tumor biopsy. It’s a strategy that could fundamentally alter the operational and economic landscape of cancer treatment.

Cracking the Code of 'Cold' Tumors

For decades, microsatellite-stable metastatic colorectal cancer (MSS mCRC) has been a fortress against immunotherapy. Representing the vast majority of colorectal cancer cases, these tumors are immunologically “cold”—lacking the mutations that typically attract the attention of the immune system. As a result, blockbuster checkpoint inhibitors that have transformed outcomes in other cancers like melanoma have largely failed here, leaving chemotherapy as the grim standard of care.

The case presented at EACR offers a compelling counter-narrative. The patient, enrolled in the OBERTO-101 trial at the Mayo Clinic, presented with unresectable liver metastases and widespread disease. After initial chemotherapy, the patient received just three doses of PolyPEPI1018, an off-the-shelf multi-peptide vaccine, alongside standard maintenance therapy. The results were dramatic. Tumors began to shrink, enabling a curative surgery that would have previously been impossible. When pathologists examined the resected tissue from the liver, colon, and 27 lymph nodes, they found a complete pathological response: no viable tumor cells remained. Today, 77.2 months later, the patient remains cancer-free.

Translational analysis revealed the vaccine had effectively turned the “cold” tumor “hot.” The patient’s immune system mounted a broad attack, with T-cells recognizing all seven of the tumor antigens targeted by the vaccine. More importantly, these vaccine-specific T-cells were found to have infiltrated the tumor, signaling a direct and potent response. This single case provides a powerful proof-of-concept that an off-the-shelf vaccine can awaken the immune system to fight a cancer it previously ignored.

The Engine Room: PEPI's Promiscuous Approach

The science behind this success is Treos Bio’s proprietary PEPI (Promiscuous EPItopes) Technology. The platform is built on a simple but powerful idea. Instead of identifying unique mutations (neoantigens) for each patient, it focuses on shared, non-mutated antigens present across many tumors. The innovation lies in identifying specific peptide fragments—epitopes—that are “promiscuous,” meaning they can bind to a wide variety of a patient’s HLA molecules, the cellular machinery that presents antigens to the immune system. This promiscuity is designed to trigger a stronger, broader, and more reliable T-cell response.

“These presentations highlight the potential of TREOS Bio's PEPI Technology to support target prediction, broad T-cell activation and durable clinical benefit in difficult-to-treat cancers,” said Sunjeet Sawhney, Chief Executive Officer of TREOS Bio. “They also reinforce the rationale for advancing PolyPEPI1018 in combination with standard therapies, while applying the PEPI Platform to additional immune-refractory cancers where current options remain limited.”

Beyond the Biopsy: A New Paradigm in Personalization

While the off-the-shelf PolyPEPI1018 vaccine shows immense promise for scalability, the second pillar of Treos Bio’s strategy could be even more disruptive. The company also presented data on its PEPI Panel, a platform that could revolutionize how personalized cancer vaccines are made.

Currently, creating a personalized vaccine is a complex, expensive, and time-consuming process. It requires an invasive tumor biopsy, followed by deep sequencing to identify targetable mutations, and finally, custom manufacturing. Treos Bio’s PEPI Panel sidesteps this entire workflow. Using only a blood or saliva sample, the company performs HLA genotyping on the patient. It then cross-references this genetic data with its massive PEPI Panel—a library of over 3,200 peptides covering 184 antigens across 19 cancers—to computationally predict which pre-existing, validated peptides will be most immunogenic for that specific patient. A personalized treatment can be designed in days, not months.

As one biotech analyst noted, “The logistical and cost advantages of a biopsy-free platform are immense. If the clinical efficacy holds up, it could fundamentally change the accessibility of personalized immunotherapy, moving it from a bespoke solution for the few to a readily available tool for many.”

A compelling case study in a patient with advanced EGFR-mutant non-small cell lung cancer (NSCLC) underscores this potential. The patient had exhausted all options, progressing through radiotherapy, targeted therapies, and chemo-immunotherapy. Using the PEPI Panel, Treos designed a personalized 11-peptide vaccine without ever touching the tumor. After treatment, the patient’s immune system showed fresh T-cell responses against seven of the targeted antigens. Remarkably, when the patient was subsequently put back on a targeted therapy (osimertinib) that had previously failed, their lung and brain lesions showed sustained regression for over nine months. This suggests the PEPI-guided immunotherapy didn’t just attack the cancer directly but also re-sensitized the tumor microenvironment, making other therapies effective again.

A Dual Strategy for a Complex Market

Treos Bio’s two-pronged approach is a masterclass in strategic positioning within the hyper-competitive immunotherapy landscape. On one hand, the off-the-shelf PolyPEPI1018 targets a massive unmet need with a product designed for scale, speed, and simpler logistics. It’s a direct challenge to the one-size-fits-all model, aiming to provide a broadly applicable solution for a specific, large patient population.

On the other hand, the PEPI Panel offers deep personalization with unprecedented operational efficiency. It provides a pathway for treating rare and refractory cancers and serves as a powerful engine for pipeline expansion. Unlike competitors such as BioNTech and Moderna, whose mRNA platforms largely rely on the complex biopsy-and-sequence neoantigen model, Treos is carving out a distinct and potentially more scalable niche.

By developing both off-the-shelf and rapidly personalized therapies from the same core technology, the company is building a flexible immunotherapy engine. The six-year survival of a patient once deemed untreatable is the human face of this progress, but the underlying strategy—a fusion of broad accessibility and precise personalization—is the blueprint that could shape the next decade of cancer care.