Guardant Health’s Blood Test Could Replace Biopsy for Certain Types of Cancer

Blood test

In 2017, the U.S. Food and Drug Administration (FDA) approved Merck’s Keytruda (pembrolizumab) for tumors that can show up anywhere in the body but are distinct because of what is called MSI-High, or microsatellite instability-high. To identify this marker, a tumor biopsy was required.

Now it looks like those types of tumors can be identified by a blood test. Redwood City, California-based Guardant Health, along with researchers with MD Anderson Cancer Center, the Samsung Medical Center and others, conducted a large study that showed the Guardant360 assay can accurately detect MSI.

MSI is a good predictor of response to checkpoint inhibitors in multiple cancer types. It shows up in about 1% of cancers and patients with advanced cancer who are MSI-High are typically eligible for immunotherapy. It is most common in colorectal, endometrial, and gastroesophageal cancers.

“Unfortunately, less than half of all advanced colon cancer patients are tested for this important biomarker,” stated Jeeyun Lee, associate professor, Division of Hematology/Oncology, Samsung Medical Center. “And across all solid tumors, we suspect the testing rate is far lower, in part due to challenges of working with tissue samples. By incorporating these results into a simple blood test, we should be able to increase the number of patients who get this information and benefit from appropriate immunotherapy.”

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The research group compared the data from 1,145 Guardant360 samples to MSI status that was found in standard-of-care tissue biopsies taken from medical records. What they found was the results from Guardant360 were the same as standard-of-care biopsy results in 98.4% of cases.

The research also analyzed the outcomes of checkpoint inhibitors in plasma MSI-High patients. In a group of 16 MSI-High gastric cancer patients receiving treatment with checkpoint inhibitors, the objective response rate was 63% and disease control rate was 81%.

“Millions of microsatellites exist throughout the genome, but most of them are poorly suited for blood-based clinical genomic analysis,” stated Scott Kopetz, associate professor of Gastrointestinal Medical Oncology at The University of Texas and co-author of the study, which was published in the journal Clinical Cancer Research. “These results show that a carefully designed panel, combined with efficient DNA-capture biochemistry and sophisticated bioinformatics tools, allow for accurate, sensitive MSI detection.”

It's also a validation for so-called liquid biopsies. These are comparable to solid tumor biopsy but are performed on blood to look for cancer cells or DNA from a tumor circulating in the blood. They are also used to detect other diseases.

Other companies working in the liquid-biopsy space include Karius, which developed a liquid biopsy for infection disease; Verily Life Sciences, which invested in Freenome; Apostle; Grail Bio; Thrive Earlier Detection Corp, which launched out of Johns Hopkins earlier this year; and others.

“We are proud to be able to bring this innovation to Guardant360 ordering physicians and the patients they treat,” stated AmirAli Talasaz, co-founder and president of Guardant Health. “We remain committed to improving the performance and utility of our products as our lab and the broader oncology field achieve advances in technology and breakthroughs in treatment.”

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