A New Milestone in Small Cell Lung Cancer: Lurbinectedin Plus Atezolizumab

Small cell lung cancer (SCLC) is a highly aggressive tumor, usually associated with smoking, that can metastasize early. In extensive-stage (advanced; ES-SCLC) disease in particular, recurrence or progression often occurs quickly despite an initial response. This increases the need for maintenance treatments that can improve long-term survival.

#ASCO25 featured the phase 3 IMforte study, pointing to a potentially transformative development: Lurbinectedin , a next-generation chemotherapy drug, significantly improved both progression-free survival (PFS) and overall survival (OS) when combined with the immunotherapy agent atezolizumab.

The IMforte Study: Details and Findings

Study Design:

• Total number of patients: 660 (patients with ES-SCLC without brain metastases before treatment)

• Induction treatment: 4 cycles of carboplatin + etoposide + atezolizumab

• Maintenance treatment phase: 483 patients

  • Control group: Atezolizumab (1200 mg IV every 3 weeks)

  • Experimental group: Atezolizumab + lurbinectedin (3.2 mg/m² IV every 3 weeks)

Key Findings:

Progression-Free Survival (PFS):

• Experimental group: 5.4 months

• Control group: 2.1 months

• HR: 0.54; P < 0.0001. A 46% reduction in the risk of cancer progression

• 6-Month PFS: 41.2% (experimental) vs 18.7% (control)

• 12-Month PFS: 20.5% vs 12%

Overall Survival (OS):

• Experimental group: 13.2 months

• Control group: 10.6 months

• HR: 0.73; P = 0.0174. A 27% reduction in the risk of death.

• 12-Month OS: 56.3% vs 44.1%

Safety Profile:

• Grade 3/4 adverse reactions: 25.6% (experimental) vs 5.8% (control)

• Grade 5 (fatal) adverse events: 0.8% vs 0.4%

• Treatment discontinuation rate: 6.2% vs 3.3%

What Is Lurbinectedin (Zepzelca®)?

Origin:

Lurbinectedin is a compound derived from marine organisms. It is a more potent and selective version of ET-743, a compound obtained from the marine organism Ecteinascidia turbinata. In 2020, the FDA granted it accelerated approval for metastatic small cell lung cancer treatment.

Key Characteristics:

• Active ingredient: Lurbinectedin

• Brand name: Zepzelca®

• Drug class: Transcription inhibitor, alkaloid-derived antineoplastic agent

• Route of administration: IV infusion every 21 days (approximately 1 hour)

• FDA approval: June 15, 2020 (2nd-line treatment)

• Licensing status in Türkiye: Not licensed; included on the overseas medicines list and requires special TİTCK authorization

Mechanism of action:

• It binds to DNA and inhibits RNA Polymerase II.

• Stops oncogenic transcription

• Triggers apoptosis (programmed cell death)

• Facilitates immune activation in the tumor microenvironment

Most Common Adverse Reactions:

• Anemia (96%), leukopenia (72%), fatigue (58%), thrombocytopenia (44%)

• Nausea, loss of appetite, vomiting, diarrhea, neutropenic fever

• Pneumonia, elevated liver enzymes, skin ulceration

Clinical and Strategic Interpretation

With these findings, lurbinectedin emerges as a strong candidate not only for second-line treatment but also for first-line maintenance therapy . This strategy:

• Prolongs tumor control

• Deepens the effect of immunotherapy

• May make the immune response durable by establishing long-term T-cell memory

Conclusion: Is a New Standard Emerging?

According to ASCO25 data, lurbinectedin plus atezolizumab could become a new standard for ES-SCLC. Although not yet licensed in Türkiye, this FDA-approved agent can be obtained with special authorization. This promising development could mean longer survival for more patients in clinical practice.