Immunotherapy-Based Combination Improves Survival in SCLC for First Time in Phase 3 Study

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First-line treatment with atezolizumab plus chemotherapy helped patients with previously untreated extensive-stage small cell lung cancer (SCLC) live significantly longer than those treated with chemotherapy alone.

For the first time, an immunotherapy-based combination has succeeded in a phase 3 study of patients with extensive-stage small cell lung cancer (ES-SCLC). According to Genentech, first-line treatment with their programmed death ligand-1 (PD-L1) inhibitor atezolizumab (Tecentriq) plus chemotherapy helped patients with previously untreated ES-SCLC live significantly longer than those treated with chemotherapy alone.

Noting limited treatment progress for patients with ES-SCLC in the past 20 years, Genentech announced that the IMpower133 study met its co-primary end points of overall survival and progression-free survival. Safety for the combination was consistent with the known safety profiles of both treatments.


“These are the first positive phase 3 survival results for any immunotherapy-based combination in the initial treatment of ES-SCLC, a particularly difficult-to-treat type of disease,” said Sandra Horning, MD, chief medical officers and head of global development, Genentech, in a statement. “The clinically meaningful results from the Impower133 study add to the growing body of evidence demonstrating that Tencentriq-based combinations may be an effective treatment for different types of advanced lung cancer.”

The phase 3, multicenter, double-blind, randomized, placebo-controlled IMpower133 study is evaluating the efficacy and safety of the PD-L1 inhibitor in combination with chemotherapies carboplatin and etoposide versus chemotherapy alone in 403 chemotherapy-naïve patients with ES-SCLC. During the treatment induction phase, patients received treatment on 21-day cycles for 4 cycles, followed by maintenance with atezolizumab or placebo until progressive disease.

According to Genentech, this is the fourth positive phase 3 lung cancer study evaluating an atezolizumab-based combination this year. The company said that data will be submitted to health authorities globally, including the FDA and the European Medicines Agency.

Currently, atezolizumab is indicated for the treatment of patients with locally advanced or metastatic urothelial carcinoma who are not eligible for cisplatin-containing chemotherapy or have disease progression during or following any platinum-containing chemotherapy, or within 12 months of neoadjuvant or adjuvant chemotherapy.

However, last week, the FDA released a statement announcing the restricted use of atezolizumab for these patients. The decision was based on data showing decreased survival associated with the drug as a monotherapy compared with platinum-based chemotherapy in clinical trials that were investigating the drug’s ability to treat metastatic urothelial cancer. The FDA also issued efficacy concerns with pembrolizumab in this patient population.