P03.03 MERMAID-1: A Phase III Study of Adjuvant Durvalumab plus Chemotherapy in Resected NSCLC Patients with MRD+ Post-Surgery

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30% of non-small-cell lung cancer (NSCLC) patients present with surgically resectable disease at diagnosis. To reduce disease recurrence, adjuvant chemotherapy is standard of care (SoC) for patients with completely (R0) resected stage II/III NSCLC. However, 5-year disease-free survival (DFS) rates remain low (∼40%), with a 5-year absolute benefit of only 5.4% derived from chemotherapy (Pignon et al. JCO 2008;26:3552-9). Determining who will benefit from adjuvant chemotherapy remains challenging. Identifying minimal residual disease (MRD) through detection of circulating tumour (ct) DNA post-surgery could predict early disease recurrence. Durvalumab is a selective, high-affinity, human IgG1 monoclonal antibody that blocks PD-L1 binding to PD-1 and CD80. In the phase III PACIFIC trial of patients with unresectable, stage III NSCLC without disease progression following radical platinum-based concurrent chemoradiotherapy, durvalumab improved progression-free survival (PFS) and overall survival (OS), demonstrating its efficacy in situations of residual disease. Further, initial data from POSEIDON showed durvalumab plus chemotherapy prolongs PFS versus chemotherapy in first line treatment of metastatic NSCLC. In the adjuvant setting (i.e. following complete tumour resection), this regimen could provide additional DFS benefit versus chemotherapy alone. MRD assessment could facilitate earlier, more selective adjuvant therapy for MRD+ patients, allowing for treatment intensification for this potentially biologically distinct disease, while minimising overtreatment of MRD– patients. MERMAID-1 will investigate the efficacy and safety of adjuvant durvalumab + SoC chemotherapy versus placebo + SoC chemotherapy in patients with completely resected stage II/III NSCLC, to assess the benefits of adjuvant therapy in patients with MRD+ status. MERMAID-1 (NCT04385368) is a phase III, parallel-arm, placebo-controlled, double-blind, multicentre study, conducted across 16 countries. Patients aged ≥18 years with histologically confirmed EGFR-/ALK- Wild-type, stage II/III NSCLC will enter the first screening period; a personalised MRD panel will be created. Before randomisation, and following assessment of MRD status post-surgery, patients will be further screened for full eligibility (no evidence of disease recurrence, WHO/ECOG performance status 0/1). Patients who have received prior adjuvant therapy or durvalumab, and those with mixed small cell and NSCLC histology or evidence of post-operative disease recurrence are ineligible. MRD status will be determined via ctDNA analysis of plasma samples, collected 3–4 weeks post-surgery, and based on personalised panels (comprised of ≤50 tumour-specific DNA variants) created by whole exome sequencing analysis of the patient’s resected tumour tissue. Approximately 332 patients will be randomised 1:1 (stratified by disease stage, MRD status, and PD-L1 expression) to durvalumab (1500 mg, intravenously) or placebo, plus concurrent SoC chemotherapy, once every three weeks (Q3W) for 12 weeks. Patients will continue with durvalumab monotherapy/placebo Q4W thereafter, until Week 48 or disease recurrence, whichever occurs first. Following a baseline radiological scan prior to randomisation, patients will be assessed Q12W until disease recurrence (per RECIST v1.1). The primary endpoint is DFS in the MRD+ analysis set (investigator-assessed). Secondary endpoints include DFS in the full analysis set (FAS; investigator-assessed); DFS in the MRD+ analysis set and FAS (blinded independent central review); OS in the MRD+ analysis set and FAS; and safety and tolerability, and patient-reported outcomes. adjuvant therapy, minimal residual disease, PD-L1