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# Mixed Data on Colon Cancer Vaccine
- URL: https://www.fdaweb.com/mixed-data-on-colon-cancer-vaccine/
- Published: 2024-04-02T12:00:00.000Z
- Updated: 2026-09-14T14:27:07.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5156686

Gritstone Bio reports mixed data from an ongoing, signal-seeking Phase 2 portion of a Phase 2/3 study evaluating Granite, a personalized neoantigen cancer vaccine for front-line use in metastatic microsatellite-stable colorectal cancer (MSS-CRC). “Circulating tumor DNA (ctDNA) analysis over several months of treatment shows the expected relationship with disease progression and favors Granite, while short-term ctDNA response analysis (molecular response as defined per protocol) did not demonstrate a difference between study arms,” the company says.

The study is designed to quantify the clinical benefit of maintenance therapy with Granite (GRT-C901/GRT-R902) in combination with immune checkpoint blockade in addition to fluoropyrimidine/bevacizumab versus fluoropyrimidine/bevacizumab alone. “Overall progression-free survival (PFS) data show an early trend in benefit for Granite patients… and extended PFS benefit in high-risk patients …, in whom progression occurs faster,” the company says.

“Pioneering new spaces carries inherent risks, and with regard to defining molecular response, we simply got it wrong,” company president and CEO **Andrew Allen** is quoted in a [release](https://ir.gritstonebio.com/news-releases/news-release-details/gritstone-bio-announces-positive-preliminary-progression-free?ref=fdaweb.com) as saying. “ctDNA levels in both arms decreased on chemotherapy for longer than we anticipated, generating similar short-term molecular response rates across arms and rendering our protocol measure of ctDNA change uninformative. Fortunately, long-term analysis demonstrates the expected correlation of ctDNA with clinical benefit and favors Granite patients. We believe these preliminary findings put us in a strong position to share mature PFS data in the third quarter and then enter regulatory discussions regarding Phase 3.”

The results are “highly encouraging” and signify the first randomized trial evidence that a personalized neoantigen-directed vaccine can potentially drive efficacy in a metastatic “cold” tumor, Gritstone adds. “The overall trend of PFS improvement in Granite recipients is great to see, and the exploratory PFS hazard ratio of 0.52 in the high-risk group, a more mature dataset, is a striking signal.”

Gritstone says that up to 97% of patients with metastatic colorectal cancer are MSS, and unlike patients with melanoma and lung cancer, they have not been helped by checkpoint inhibitors. “These preliminary results indicate that Granite is inducing a potentially significant immune response in a disease that has been felt to be immunologically cold,” it says.

Additionally, Granite was found in the study to be generally well-tolerated, and no patients discontinued therapy due to adverse events. Mature PFS data are expected in the third quarter, and overall survival data are expected in the first half of next year, according to the company.