New Cancer Diagnostic Targets Elusive Biomarker in Hard-to-Treat Tumors

BOSTON, MA – April 21, 2026 – By Christine Carter

In a significant step forward for precision oncology, Foundation Medicine and Bristol Myers Squibb have expanded their collaboration to tackle one of the field's persistent challenges: identifying patients with a subtle but critical genetic vulnerability. The partnership will focus on developing Foundation Medicine’s comprehensive genomic test, FoundationOne®CDx, into a companion diagnostic to find patients with a specific biomarker known as homozygous MTAP deletion, paving the way for a new investigational therapy from Bristol Myers Squibb.

This alliance addresses a crucial unmet need, as the MTAP deletion is prevalent in some of the most aggressive and difficult-to-treat cancers, including pancreatic cancer, glioblastoma, and non-small cell lung cancer (NSCLC). By refining the tools to find these patients, the two companies hope to bring a highly targeted treatment to those who currently have few options.

The Scientific Challenge: Unmasking a Hidden Biomarker

Homozygous deletion of the Methylthioadenosine Phosphorylase (MTAP) gene is not a rare event; it occurs in an estimated 10-15% of all human cancers. Its presence is particularly high in tumors with grim prognoses. Studies show MTAP deletion in up to 30% of pancreatic cancers, 33% of mesotheliomas, and nearly 60% of glioblastomas. For patients, this genetic alteration is often linked to shorter survival and a higher risk of metastasis.

The MTAP gene is located on a chromosomal region that also houses potent tumor suppressor genes. Its frequent co-deletion with these genes contributes to a more aggressive form of cancer. However, identifying this specific deletion has been a significant hurdle for clinicians and researchers. Detecting the complete loss of a gene, known as a copy number alteration, can be technically challenging.

“Homozygous MTAP deletion is a critical biomarker, yet one that can be difficult to detect without an assay that unveils blind spots others interpret as noise,” said Troy Schurr, chief commercial officer at Foundation Medicine, in a recent statement. The issue lies in the low signal-to-noise ratio in the genomic data, which can make it hard to distinguish a true gene deletion from background variability. This collaboration aims to refine FoundationOne CDx, an FDA-approved, tissue-based next-generation sequencing test, to reliably and accurately report homozygous MTAP deletion, ensuring that no eligible patient is missed.

A Targeted Attack: The Promise of PRMT5 Inhibition

The reason for singling out this biomarker lies in the unique metabolic vulnerability it creates within a cancer cell. The absence of the MTAP enzyme leads to a buildup of a metabolite called methylthioadenosine (MTA). This accumulation creates a dependency that can be exploited. Bristol Myers Squibb’s investigational therapy, BMS-986504, is designed to do just that.

BMS-986504 is a selective, MTA-cooperative inhibitor of a protein called PRMT5. In healthy cells, the drug has little effect. But in MTAP-deleted cancer cells overflowing with MTA, the drug binds to the PRMT5-MTA complex and shuts it down, triggering a cascade that leads to selective cancer cell death. This elegant mechanism allows the therapy to target the tumor while largely sparing healthy tissue.

Early clinical data has shown promise. A Phase 1/2 study of BMS-986504 in patients with various advanced solid tumors harboring the MTAP deletion demonstrated an overall response rate of 23%. The results were even more encouraging in a subgroup of patients with non-small cell lung cancer, where the response rate climbed to 30%.

These results have fueled further development, with multiple large-scale trials now planned or underway. The MountainTAP-29 study will investigate the drug as a first-line treatment for metastatic NSCLC, while the MountainTAP-30 trial will test it in patients with untreated metastatic pancreatic cancer—two patient populations in desperate need of new options.

The Power of Partnership: Co-Developing Drugs and Diagnostics

The collaboration between Foundation Medicine and Bristol Myers Squibb exemplifies a modern, more integrated approach to cancer drug development. The era of one-size-fits-all chemotherapy is giving way to a paradigm where therapies are designed for specific patient populations defined by molecular biomarkers. For this model to succeed, a reliable diagnostic test is just as important as the drug itself.

Foundation Medicine has established itself as a leader in this space, with its FoundationOne CDx and FoundationOne Liquid CDx tests collectively holding over 100 approved companion diagnostic indications in the U.S. and Japan. The company’s platform was the first broad companion diagnostic approved by the FDA, capable of detecting all major classes of genomic alterations from a single tissue sample.

This expanded partnership is not just a one-off project but a deepening of a long-standing relationship. For Bristol Myers Squibb, it de-risks the development of BMS-986504 by ensuring a clear path to identifying the patients most likely to benefit. For Foundation Medicine, it solidifies its position as the diagnostic partner of choice for leading pharmaceutical innovators and expands the clinical utility of its flagship test.

Implications for Patients and the Future of Oncology

For patients and their families, this collaboration represents tangible hope. Individuals diagnosed with MTAP-deleted cancers may soon have a dedicated therapeutic option where none previously existed. The development of a robust companion diagnostic is the critical first step in making that a reality, transforming a genomic finding into an actionable treatment plan.

This effort highlights a broader shift in oncology. The focus is expanding from more straightforward genetic mutations to complex alterations like copy number variations and the metabolic vulnerabilities they create. Successfully targeting MTAP deletion requires a sophisticated understanding of both cancer biology and diagnostic technology, representing the next frontier in personalized medicine.

As researchers continue to unravel the intricate wiring of cancer cells, the co-development of drugs and diagnostics will become even more essential. This alliance between Foundation Medicine and Bristol Myers Squibb serves as a powerful blueprint for the future, demonstrating how a deep, scientific partnership can accelerate the journey of a promising therapy from the laboratory to the clinic, ultimately offering new possibilities for patients fighting the toughest cancers.