SUMMARY: The FDA on October 2, 2025, approved Lurbinectedin (ZEPZELCA®) in combination with Atezolizumab (TECENTRIQ®) or Atezolizumab and hyaluronidase-tqjs (TECENTRIQ HYBREZA®), for the maintenance treatment of adult patients with Extensive-Stage Small Cell Lung Cancer (ES-SCLC) whose disease has not progressed after first-line induction therapy with Atezolizumab or Atezolizumab and hyaluronidase-tqjs, Carboplatin, and Etoposide.
The American Cancer Society estimates that for 2025, about 226,650 new cases of lung cancer will be diagnosed and 124,730 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Small Cell Lung Cancer (SCLC) originates from neuroendocrine cells and accounts for approximately 10-15% of all lung cancers diagnosed annually in the US. It is lethal and aggressive. The 5 year survival rate for Extensive Stage SCLC (ES-SCLC) is less than 5%, with a median survival of 9-10 months from the time of diagnosis.
Treatment decisions was SCLC are typically based on the VA Lung Group 2-Staging system, which classifies disease as either Limited Stage (LS) or Extensive Stage (ES). In Limited Stage patients, the disease burden is limited to one hemithorax and regional nodes, without presence of extra-thoracic disease, and amenable to definitive-intent thoracic Radiation Therapy (RT). Extensive Stage encompasses all other SCLC patients.
Patients with ES-SCLC are often treated with chemoimmunotherapy with or without radiation in the first line setting. While initial responses to chemotherapy are often dramatic, relapse occurs in most patients, and recurrent disease typically demonstrates resistance to previously effective regimens. Consequently, extending response durability through maintenance therapy remains a key therapeutic goal.
Lurbinectedin is a selective alkylating agent that binds to guanine residues within DNA, leading to inhibition of oncogenic transcription factors and impairment of DNA repair pathways. This disrupts the cell cycle and induces tumor cell death.
Atezolizumab is a monoclonal antibody targeting Programmed Death-Ligand 1 (PD-L1), blocking its interaction with PD-1 and B7.1 receptors. By inhibiting PD-L1–mediated immune evasion, Atezolizumab restores anti-tumor T-cell activity and enhances immune-mediated tumor elimination.
The IMforte Trial: Study Design
The IMforte Trial is a global, open-label, randomized Phase III study (NCT05091567) conducted to evaluate the efficacy and safety of Lurbinectedin plus Atezolizumab as first-line maintenance therapy for adults with Extensive-Stage SCLC (ES-SCLC). In this study, a total of 660 treatment-naïve patients received induction therapy with Atezolizumab, Carboplatin, and Etoposide for four 21-day cycles. Of these, 483 patients without disease progression were randomized 1:1 to receive either:
- Lurbinectedin 3.2 mg/m² IV every 3 weeks with G-CSF prophylaxis plus Atezolizumab 1200 mg IV every 3 weeks, or
- Atezolizumab alone 1200 mg IV every 3 weeks
Treatment was continued until disease progression, unacceptable toxicity, or withdrawal. Stratification factors included baseline liver metastases, ECOG performance status, LDH levels, and receipt of prophylactic cranial irradiation. The Primary endpoints were Independent Review Facility (IRF)–assessed Progression-Free Survival (PFS) and Overall Survival (OS) from the start of maintenance therapy.
Efficacy Outcomes
After a median follow-up of 15 months, the IMforte study achieved both of its Primary endpoints:
- Median PFS: 5.4 months with Lurbinectedin plus Atezolizumab vs 2.1 months with Atezolizumab alone (HR=0.54; 95% CI: 0.43–0.67; P<0.0001)
- Median OS: 13.2 months vs 10.6 months, respectively (HR=0.73; 95% CI: 0.57–0.95; P=0.0174)
These outcomes reflect a 46% reduction in the risk of disease progression or death and a 27% reduction in the risk of death with the combination regimen. Median maintenance treatment duration was 4.1 months for the combination arm and 2.1 months for the monotherapy arm.
Safety and Tolerability
The combination of Lurbinectedin and Atezolizumab demonstrated a manageable safety profile with no new safety signals.
- Any-grade treatment-related adverse events (TRAEs):5% (combo) vs 40.0% (monotherapy)
- Grade 3–4 TRAEs: 25.6% vs 5.8%
- Grade 5 TRAEs: 0.8% vs 0.4%
The most common adverse reactions (≥30%) were lymphopenia, thrombocytopenia, anemia, leukopenia, neutropenia, nausea, and fatigue/asthenia. Discontinuations due to adverse events occurred in 6.2% and 3.3% of patients, respectively.
Clinical Interpretation
IMforte is the first global Phase III study to demonstrate significant improvement in both PFS and OS with a first-line maintenance approach in ES-SCLC. By integrating the DNA-damaging activity of Lurbinectedin with the immune reactivation potential of PD-L1 blockade, the combination offers a dual mechanism to counter both tumor proliferation and immune evasion. These results establish Lurbinectedin plus Atezolizumab as a new standard maintenance option for patients whose disease remains controlled after induction chemoimmunotherapy, an important milestone in a disease where long-term survival has historically been rare.
Key Takeaways for Oncology Practice
- Unmet Need: SCLC remains an aggressive malignancy with limited long-term treatment options.
- Clinical Significance: IMforte is the first Phase III trial to demonstrate both OS and PFS gains with a first-line maintenance regimen in ES-SCLC.
- Mechanistic Synergy: Combines DNA-targeted cytotoxic activity (Lurbinectedin) with PD-L1 blockade (Atezolizumab) for enhanced and durable tumor control.
- Practice Impact: Establishes Lurbinectedin plus Atezolizumab as an FDA-approved maintenance option for patients with ES-SCLC who respond to induction chemoimmunotherapy.
- Safety: Manageable toxicity profile; regular hematologic and clinical monitoring recommended.
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. Paz-Ares L, Borghaei H, Liu SV, et al. The Lancet 2025;405:2129-2143.
