Efficacy and safety of first-line maintenance therapy with lurbinectedin plus atezolizumab in extensive-stage small-cell lung cancer (IMforte): a randomised, multicentre, open-label, phase 3 trial

Background: Despite improved efficacy with first-line immune checkpoint inhibitors plus platinum-based chemotherapy for extensive-stage small-cell lung cancer (ES-SCLC), survival remains poor. In this study, we aimed to compare lurbinectedin plus atezolizumab and atezolizumab alone as maintenance therapies in patients with ES-SCLC without progression after induction therapy with atezolizumab, carboplatin, and etoposide. Methods: IMforte was a randomised, open-label, phase 3 trial done at 96 hospitals and medical centres in 13 countries (Belgium, Germany, Greece, Hungary, Italy, Mexico, Poland, South Korea, Spain, Taiwan, Türkiye, the UK, and the USA). Eligible patients were aged 18 years or older with treatment-naive ES-SCLC. Patients received four 21-day cycles of induction treatment (atezolizumab, carboplatin, and etoposide). After completing induction treatment, eligible patients without disease progression were randomly assigned (1:1) using permuted blocks (Interactive Voice/Web Response System) to receive maintenance treatment intravenously every 3 weeks with lurbinectedin (3·2 mg/m²; with granulocyte colony-stimulating factor prophylaxis) plus atezolizumab (1200 mg) or atezolizumab (1200 mg). The two primary endpoints were independent review facility-assessed (IRF) progression-free survival and overall survival, measured from randomisation into the maintenance phase. Efficacy endpoints were assessed in the full analysis set, which included all patients who were randomly assigned to maintenance phase treatment, regardless of whether they received their assigned study treatment. Safety was assessed in all patients who received at least one dose of lurbinectedin or atezolizumab, and was analysed according to the treatment received. This study is registered with ClinicalTrials.gov, NCT05091567, and is closed for recruitment. Findings: Between Nov 17, 2021, and Jan 11, 2024, 895 patients were screened for enrolment, of whom 660 (74%) were enrolled into the induction phase. Between May 24, 2022, and April 30, 2024, 483 (73%) of 660 patients entered the maintenance phase and were randomly assigned to lurbinectedin plus atezolizumab (n=242) or atezolizumab (n=241). At the data cutoff (July 29, 2024), IRF progression-free survival was longer in the lurbinectedin plus atezolizumab group than the atezolizumab group (stratified hazard ratio [HR] 0·54 [95% CI 0·43–0·67]; p<0·0001), as was overall survival (stratified HR 0·73 [0·57–0·95]; p=0·017). 92 (38%) of 242 patients in the lurbinectedin plus atezolizumab group and 53 (22%) of 240 patients in the atezolizumab group had grade 3–4 adverse events. The most common grade 3–4 events in the lurbinectedin plus atezolizumab group were anaemia (20 [8%] of 242 patients), decreased neutrophil count (18 [7%] patients), and decreased platelet count (18 [7%] patients) and the most common events in the atezolizumab group were hyponatremia (five [2%] of 240 patients), dyspnoea (four [2%] patients), and pneumonia (four [2%] patients). Grade 5 adverse events occurred in 12 (5%) of 242 patients in the lurbinectedin plus atezolizumab group and six (3%) of 240 patients in the atezolizumab group. The incidence of myelosuppressive toxicities (eg, neutropenia and leukopenia) was higher in the lurbinectedin plus atezolizumab group than the atezolizumab group. Interpretation: IRF progression-free survival and overall survival were longer in the lurbinectedin plus atezolizumab group than the atezolizumab group for patients with ES-SCLC, albeit with a higher incidence of adverse events. Lurbinectedin plus atezolizumab represents a novel therapeutic option for first-line maintenance treatment in this setting. Funding: F Hoffmann-La Roche and Jazz Pharmaceuticals.