AstraZeneca's Imfinzi (durvalumab) has been granted Priority Review and Breakthrough Therapy Designation by the U.S. Food and Drug Administration (FDA) for the treatment of patients with limited-stage small cell lung cancer (LS-SCLC) whose disease has not progressed following platinum-based concurrent chemoradiotherapy (cCRT). This regulatory action is based on the positive results from the ADRIATIC Phase III trial, potentially marking a significant advancement in a disease with limited treatment options. The FDA's decision is anticipated in the fourth quarter of 2024.
Clinical Efficacy of Imfinzi in LS-SCLC
The supplemental Biologics License Application (sBLA) for Imfinzi is supported by data from the ADRIATIC trial, which demonstrated a statistically significant and clinically meaningful improvement in overall survival (OS). Specifically, Imfinzi reduced the risk of death by 27% compared to placebo (HR 0.73; 95% CI: 0.57-0.93; p=0.0104). The estimated median OS was 55.9 months for Imfinzi versus 33.4 months for placebo. At three years, an estimated 57% of patients treated with Imfinzi were alive, compared to 48% on placebo.
Imfinzi also showed a reduction in the risk of disease progression or death by 24% (HR 0.76; 95% CI: 0.61-0.95; p=0.0161). Median progression-free survival (PFS) was 16.6 months for Imfinzi versus 9.2 months for placebo. Two-year PFS rates were 46% for Imfinzi and 34% for placebo.
Priority Review and Breakthrough Therapy Designation
The FDA grants Priority Review to medicines that, if approved, would offer significant improvements over available options. Breakthrough Therapy Designation (BTD) is intended to expedite the development and review of potential new medicines for serious conditions with unmet medical needs. These designations underscore the potential of Imfinzi to address a critical gap in the treatment of LS-SCLC.
Unmet Need in Small Cell Lung Cancer
Small cell lung cancer (SCLC) is an aggressive form of lung cancer, with LS-SCLC accounting for approximately 30% of SCLC diagnoses. Despite initial responses to chemotherapy and radiotherapy, the prognosis for LS-SCLC remains poor, with only 15-30% of patients surviving five years after diagnosis. The current standard of care has remained largely unchanged for four decades, highlighting the urgent need for new therapeutic options.
ADRIATIC Trial Design
The ADRIATIC trial is a randomized, double-blind, placebo-controlled, multi-center global Phase III trial involving 730 patients with LS-SCLC who had not progressed following cCRT. Patients were randomized to receive Imfinzi monotherapy or Imfinzi plus Imjudo (tremelimumab) versus placebo. The dual primary endpoints were PFS and OS for Imfinzi monotherapy versus placebo. The safety profile of Imfinzi was manageable and consistent with its known profile.
Imfinzi: An Anti-PD-L1 Antibody
Imfinzi (durvalumab) is a human monoclonal antibody that binds to the PD-L1 protein, blocking its interaction with PD-1 and CD80 proteins. This mechanism counters the tumor's immune-evading tactics and releases the inhibition of immune responses. Imfinzi is currently approved for unresectable Stage III NSCLC, extensive-stage SCLC, metastatic NSCLC, biliary tract cancer, and hepatocellular carcinoma, among other indications.
Susan Galbraith, Executive Vice President, Oncology R&D, AstraZeneca, stated, "This Priority Review reinforces the potential of Imfinzi to transform outcomes for patients as the first and only immunotherapy to demonstrate a survival benefit in limited-stage small cell lung cancer...we look forward to working with the FDA to bring Imfinzi to patients as quickly as possible."
