A highly sensitive, low input, and automated assay for molecular residual disease detection (MRD) using whole-genome sequencing (WGS).

3060 Background: Molecular residual disease (MRD) detection using cell-free DNA (cfDNA) for solid tumors requires a highly sensitive and specific assay that can overcome the limitation of low abundance circulating-tumor DNA (ctDNA) in a standard blood draw with fast sample-to-answer turn-around time (TAT). Here we describe the development and analytical performance of Illumina’s TruSight Oncology MRD WGS assay (TSO MRD, for research use only), for detecting MRD using tumor-informed whole-genome sequencing (WGS) of cfDNA extracted from plasma samples across multiple cancer types. Methods: The TSO MRD assay was built using Illumina’s best-in-class WGS library preparation, informatics and sequencing technologies. The assay is composed of two major steps, fingerprinting and ctDNA detection. At the fingerprinting step, the DNA from tumor tissue and matched normal samples is analyzed through WGS to generate a sample specific somatic variant list. At the ctDNA detection step, the cfDNA extracted from plasma is analyzed through shallow WGS and the presence of ctDNA is detected using the tumor specific fingerprint as an input in the MRD analysis pipeline. The plasma extraction and WGS library preparation workflows are fully automated for high-throughput sample processing with minimum hands-on time and touch points. Results: Testing of commercial MRD reference materials and ctDNA-positive samples serially diluted into normal cfDNA background demonstrated a limit of detection of down to 0.001% VAF or 10 parts per million (PPM) in multiple cancer types. Testing of a panel of normal plasma samples from healthy individuals assessed against 20 sets of fingerprints from multiple cancer types demonstrated an analytical specificity of 99.7%. Testing of ctDNA samples with multiple operators, instruments and library prep start days demonstrated high reproducibility in MRD detection. The ctDNA testing works at an optimal input amount of 5 ng and a minimum input amount down to 2 ng, which yields a high sample success rate from one standard 10 ml of blood draw. The TAT of the fingerprinting and the ctDNA detection steps is 5-7 days, respectively. Conclusions: The TSO MRD assay demonstrated high analytical sensitivity and specificity in detecting the presence of ctDNA from low input plasma samples with automated workflow and fast TAT. This assay enables a single streamlined solid tumor MRD platform for multiple cancer types.