Two weeks after the initial approval of tremelimumab (Imjudo; AstraZeneca), a CTLA-4 monoclonal antibody, on November 10, 2022, the FDA approved this new immunotherapy, in combination with the PD-L1 inhibitor durvalumab (Imfinzi; AstraZeneca) and platinum-based chemotherapy, for the treatment of adults with metastatic non–small-cell lung cancer (NSCLC) and no EGFR or ALK genomic alterations.
“The approval of this dual immunotherapy regimen with chemotherapy introduces a new, generally well-tolerated treatment option for patients with this devastating disease and gives them the chance to benefit from the long-term survival advantage seen with CTLA-4 inhibition,” said Melissa Johnson, MD, lead investigator of POSEIDON and Director of Lung Cancer Research, Sarah Cannon Research Institute, Tennessee Oncology, Nashville.
The efficacy of this immunotherapy combination plus chemotherapy was evaluated in the phase 3 POSEIDON clinical trial, a randomized, multicenter, open-label study of patients with metastatic NSCLC who had not received systemic treatment. Patients were randomized to 1 of 3 treatment arms: (1) tremelimumab, durvalumab, and platinum-based chemotherapy for 4 cycles, followed by durvalumab and maintenance chemotherapy every 4 weeks, and a fifth dose of tremelimumab at week 16; (2) durvalumab plus platinum-based chemotherapy for 4 cycles, followed by durvalumab and maintenance chemotherapy; or (3) platinum-based chemotherapy for 6 cycles, followed by maintenance chemotherapy. Treatment was continued until disease progression or unacceptable adverse events.
The FDA approval was based on the results of the 675 patients in arms 1 and 3. The main efficacy measures were progression-free survival (PFS) and overall survival (OS). Tremelimumab plus durvalumab and chemotherapy showed a significant and clinically meaningful improvement in OS versus chemotherapy alone (hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.65-0.92; 2-sided P = .00304).
The median OS was 14 months (95% CI, 11.7-16.1) with the triplet combination versus 11.7 months (95% CI, 10.5-13.1) with chemotherapy alone. The median PFS was 6.2 months (95% CI, 5.0-6.5) and 4.8 months (95% CI, 4.6-5.8), respectively (HR, 0.72; 2-sided P = .00031). The overall response rate was 39% versus 4%, respectively, and the median duration of response was 9.5 months versus 5.1 months, respectively.
The most common (≥20%) adverse events with the triplet were nausea, fatigue, decreased appetite, musculoskeletal pain, rash, and diarrhea. Grade 3 or 4 laboratory abnormalities (≥10%) were neutropenia, anemia, leukopenia, lymphocytopenia, increased lipase, hyponatremia, and thrombocytopenia.