NEW YORK (GenomeWeb) – Inivata highlighted new data this week published with academic collaborators from Institut Gustave Roussy in France, which showed that patients tested using the company's liquid biopsy assay and treated based on the results benefitted from genomically targeted treatment just as much as subjects who got tissue-based tests in prior clinical trials.
The results — published online earlier this year and in print this week in Annals of Oncology —join a relatively slim set of evidence so far that speaks directly to the clinical utility of liquid biopsy tests and how their use actually impacts patient outcomes.
"We believe that our technology has advantages … but what you have to do is then prove that that means something in clinical practice, and that it has value to clinicians, and of course payors," Inivata's Chief Medical Officer Clive Morris said today.
"With all the excitement around ctDNA there has been very little published in terms of clinical outcomes of patients treated based on these tests," he added.
Concordance with tissue has dominated much of the existing data for liquid biopsy tests so far. And the fact that tests of patients' blood closely replicate those of their tissue does suggest that they should identify mutations with similar accuracy. If that's true, patients should respond to targeted drugs at about the same rate when tested using liquid biopsy as they have in the defining clinical trials that used tissue.
But this type of evidence isn't necessarily enough for clinicians calling for more definitive proof that a blood-based mutation actually predicts response to a targeted drug in the same way that tissue testing has proven itself to do.
Though studies have linked ctDNA status to drug response, suggesting strongly that response rates should be largely equivalent regardless of the DNA source, they have done so mostly in a retrospective manner.
Inivata's study provides important validation of this inferred clinical utility, for its own assay, but also potentially for liquid biopsy approaches more generally.
Unlike some other liquid biopsy firms, Inivata hasn't commercially launched its test yet, though it plans to later this year.
"We don't want to commercialize too soon and send an offering to the market and make claims, and drive demand without clinicians knowing exactly how to apply it," said Philip Perez, the firm's chief commercial officer.
Instead, the company has been using money raised in a £31.5 million ($46 million) Series A financing round last year to support studies like the one published this week, as well as research that it hopes will differentiate its technology from others based on exquisite sensitivity.
Though the study with Gustave Roussy was relatively small — investigators only followed 48 patients with advanced non-small cell lung cancer — Inivata believes it is the first to offer a clear prospective evaluation of a targeted drug's effectiveness based on the identification of cancer mutations in blood alone, without matched tissue testing.
The 48 subjects in the study all had known EGFR mutations and were treated initially with a tyrosine kinase inhibitor — to which they at some point developed resistance. Patients were recruited specifically because they could not be biopsied for a second round of tissue-based testing for one reason or another.
Researchers evaluated blood samples using Inivita's InVision ctDNA sequencing assay, looking for the presence of T790 mutations, a known mechanism of acquired resistance to the first and second-generation TKIs.
InVision is based on a technology called targeted amplicon sequencing (TAm-seq), developed by Tim Forshew and Muhammed Murtaza and spun out from Nitzan Rosenfeld's laboratory at the University of Cambridge in 2014.
According to Morris, the results of the new study speak to the validity and utility of InVision in two ways. First, about half of the patients tested were positive for T790M using the blood-based assay. This is consistent with the prevalance that would be expected based on a wealth of evidence from prior trials, he said in an interview this week.
Secondly, when these mutation-positive patients were treated with AstraZeneca's third-generation TKI Tagrisso (osimertinib), they had response rates that closely mimicked what was seen in the drug's registration trials using tissue-based tests.
Among evaluable patients, osimertinib showed a partial response rate of 62.5 percent and a stable disease rate of 37.5 percent, the study authors reported.
The Gustave Roussy study confirms results of individual case studies or small series that have begun to be presented at scientific meetings and published in brief over the last year or so.
For example, Guardant Health began describing prospective outcomes data in patients treated solely based on liquid biopsy at last year's ASCO annual meeting. According to the company, NSCLC patients in its NEXT-2 trial had an 88 percent response rate and 94 percent disease control rate when matched to a targeted therapy by their Guardant360 results.
The study also expands on what have so-far been mostly retrospective links between ctDNA and drug response by Guardant and other companies in the space.
Moving forward, Inivata expects to launch its flagship lung cancer test commercially later this year, Perez said. It also has plans for tests in a number of other cancer types, including breast, colon, pancreatic, and ovarian cancers, though these are not as far along in development.
Inivata's study this week speaks to a relatively low-hanging fruit in the liquid biopsy space — guiding targeted therapy in advanced cancer patients. But because it believes its technology stands out from others based on sensitivity in detection of very rare or infrequent alterations, the company is also working on building clinical utility evidence in other clinical niches that have seen growing interest in the liquid biopsy space, such as assessing risk of recurrence after surgery in early-stage cancers or detecting relapses and metastases early, before they manifest clinically.
Perez added that the firm is also anticipating that it will be following up the Series A funding round it closed last year with a "significant" Series B round in the next few months, buoying the validity and utility data to support its ongoing commercialization.