Current Landscape of Immunotherapy Trials Involving the Programmed Cell Death Protein 1/Programmed Death-Ligand 1 Axis in Intrathoracic Tumors

INTRODUCTION: The clinical successes seen with anti–programmed cell death protein 1/programmed death-ligand 1 (anti–PD-[L]1) agents have galvanized the field of immuno-oncology. We evaluated the landscape and trends in immunotherapy trials involving the PD-(L)1 axis in intrathoracic tumors. METHODS: We identified clinical trials involving anti–PD-(L)1 agents on the ClinicalTrials.gov registry through November 13, 2020 for NSCLC, SCLC, mesothelioma, and thymic epithelial tumor. Clinical trials were indexed according to monotherapy versus combination approaches, PD-(L)1 agents under investigation, clinical settings, trial start date, and partner drug(s). We assessed redundancy among the clinical trials. RESULTS: We found 686 clinical trials investigating anti–PD-(L)1 agents for intrathoracic tumors (540 trials in NSCLC, 96 in SCLC, 38 in mesothelioma, and 12 in thymic epithelial tumor). A total of 23 PD-(L)1 inhibitors are undergoing clinical development. A total of 81% of trials assess combination treatment. The number of clinical trials has been growing exponentially in the past decade. PD-(L)1 blockade was frequently combined with chemotherapy or immunomodulatory therapy. Various strategies are in development to overcome resistance to PD-(L)1 blockade in metastatic NSCLC. PD-(L)1 blockade is also increasingly evaluated in neoadjuvant and adjuvant settings. After the U.S. Food and Drug Administration’s approval of an anti–PD-(L)1 agent for a specific indication, 14 trials were launched thereafter, which continued to randomize patients to treatments that were inferior to the best available therapy. CONCLUSIONS: The number of clinical trials investigating anti–PD-(L)1 agents in intrathoracic tumors has experienced a steep increase over the past decade with a notable upward trend for combination trials. To reduce duplicative research efforts and accelerate the development of effective immunotherapeutics, improved coordination among key stakeholders and the adoption of innovative trial designs will be vital.