What is the POLARIS RSPO Gene Fusion TEST?
The POLARIS RSPO Gene Fusion TEST for colorectal cancer is a Laboratory-Developed Test (LDT) developed by the POLARIS Laboratory at Genome Institute of Singapore (POLARIS@GIS) for the qualitative detection of gene fusions involving either RSPO2 or RSPO3 by multiplex reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) in formalin-fixed paraffin-embedded (FFPE) or fresh (frozen) colorectal cancer (CRC) tissue. Presence of one of these fusions in microsatellite stable MSS CRC patients was shown to be a positive predictive biomarker for ETC-159 treatment.
How will the POLARIS RSPO Gene Fusion TEST results affect treatment for colorectal cancer patients?
R-spondins (RSPOs) are regulators of Wnt signalling. Over-activation of RSPO2 or RSPO3 leads to a hyperactivated Wnt signalling pathway. Several PDX models have demonstrated that ETC-159 has tumour-growth inhibiting properties as a single agent in tumours that bear RSPO gene fusions. As there was/is no specific test available to determine the presence of RSPO fusions other than NGS, which isn’t sufficiently sensitive, therefore the qRT-PCR RSPO Gene Fusion Test has been analytically validated in POLARIS according to CAP and Clinical Laboratory Standard Institute (CLSI) guidelines and after previous agreement with the US FDA. POLARIS is using the test to pre-screen CRC patients in the early-phase (Phase 1B) clinical trial to identify those patients with RSPO-fusions to support the selection and eligibility of CRC patients for whom ETC-159 treatment is being considered.
How are patients assured of the quality of the POLARIS RSPO Gene Fusion TEST?
The POLARIS RSPO Gene Fusion Test was developed and validated in accordance with the College of American Pathologists (CAP) guidelines, within the CAP-accredited POLARIS Laboratory at Genome Institute of Singapore (POLARIS@GIS).
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