SUMMARY: Lung cancer is the second most common cancer in both men and women and accounts for about 13% of all new cancers and 21% of all cancer deaths. The American Cancer Society estimates that for 2023, about 238,340 new cases of lung cancer will be diagnosed and 127,070 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Non-Small Cell Lung Cancer (NSCLC) accounts for approximately 85% of all lung cancers. Of the three main subtypes of NSCLC, 30% are Squamous Cell Carcinomas (SCC), 40% are Adenocarcinomas and 10% are Large Cell Carcinomas. With changes in the cigarette composition and decline in tobacco consumption over the past several decades, Adenocarcinoma now is the most frequent histologic subtype of lung cancer.
Immune checkpoints are cell surface inhibitory proteins/receptors that are expressed on activated T cells. They harness the immune system and prevent uncontrolled immune reactions by switching off the T cells of the immune system. Immune checkpoint proteins/receptors include CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4, also known as CD152) and PD-1(Programmed cell Death 1). Checkpoint inhibitors unleash the T cells resulting in T cell proliferation, activation, and a therapeutic response.
IMFINZI® (Durvalumab) is a human immunoglobulin G1 monoclonal antibody that binds to the PD-L1 protein and blocks the interaction of PD-L1 with the PD-1 and CD80 proteins, countering the tumor’s immune-evading tactics, and unleashes the T cells. IMJUDO® (Tremelimumab) is a human immunoglobulin G2 monoclonal antibody that targets and blocks the activity of CTLA-4, enhancing binding of CD80 and CD86 to CD28. This complimentary mechanisms of action broadens clinical activity, potentially overcoming primary resistance to PD-(L)1 blockade by enabling novel T-cell responses. The concurrent addition of chemotherapy to checkpoint inhibitors causes tumor cell death and release of neoantigens, which increases immune priming, important for early disease control.
POSEIDON is a global, randomized, open-label, three-arm, Phase III study, which evaluated the efficacy of Tremelimumab plus Durvalumab along with chemotherapy, and Durvalumab along with chemotherapy, compared to chemotherapy alone, in first-line treatment of metastatic NSCLC. In this trial, 1013 patients (N=1013) with EGFR/ALK wild-type metastatic NSCLC were randomly assigned (1:1:1) to receive either Tremelimumab 75 mg IV plus Durvalumab 1,500 mg IV along with chemotherapy for up to four 21-day cycles, followed by Durvalumab 1500 mg IV once every 4 weeks until disease progression, with one additional Tremelimumab dose after chemotherapy at week 16 (fifth dose), Durvalumab 1500 mg IV plus chemotherapy for up to four 21-day cycles, followed by Durvalumab 1500 mg IV once every 4 weeks until disease progression, or chemotherapy alone for up to six 21-day cycles. Chemotherapy options for treatment groups included Carboplatin plus nab-Paclitaxel regardless of histology, Cisplatin or Carboplatin plus Gemcitabine for patients with squamous histology, and Cisplatin or Carboplatin plus Pemetrexed for patients with nonsquamous histology. Patients with nonsquamous histology who received Pemetrexed-Platinum doublet could receive Pemetrexed maintenance therapy if eligible. Patients continued treatment until progressive disease or unacceptable toxicity. Patients were stratified by PD-L1 expression (50% or more versus less than 50%), disease Stage (IVA versus IVB), and histology (squamous versus nonsquamous). The median age was 64 yrs, 63% had nonsquamous histology, and approximately a third of the patients had PD-L1 expression less than 1%. The treatment groups were well balanced. The Primary end points were Progression Free Survival (PFS) and Overall Survival (OS) for the Durvalumab plus chemotherapy group, compared to the chemotherapy alone group. Key Secondary end points were PFS and OS for Tremelimumab plus Durvalumab along with chemotherapy, compared to chemotherapy alone.
The coPrimary end point of PFS benefit with Durvalumab plus chemotherapy compared to chemotherapy alone was met (HR=0.74; P=0.0009), and the median PFS was 5.5 versus 4.8 months respectively and the 12-month PFS rates were 24.4% versus 13.1%. However, OS did not reach statistical significance (HR=0.86; P=0.075). When Secondary end points were formally evaluated, Tremelimumab plus Durvalumab and platinum-based chemotherapy demonstrated a statistically significant and clinically meaningful improvement in OS compared to chemotherapy alone (HR=0.77; P=0.003). The median OS was 14 months versus 11.7 months respectively and 2 year OS was 32.9% versus 22.1% respectively. The median PFS was 6.2 months and 4.8 months in the treatment arms, respectively (HR=0.72; P=0.0003) and the 1-year PFS rate was 26.6% and 13.1% respectively. Treatment benefit was seen across all PD-L1 subgroups, particularly in tumors with PD-L1 expression of 50% or more. Patients with tumor PD-L1 expression less than 1% appeared to gain improved survival benefit from the addition of Tremelimumab to Durvalumab and chemotherapy.
Based on this study, the FDA approved Tremelimumab in combination with Durvalumab and platinum-based chemotherapy for adult patients with metastatic NSCLC, with no sensitizing EGFR mutation or ALK genomic tumor aberrations.
It was concluded that Durvalumab plus chemotherapy significantly improved Progression Free Survival when compared to chemotherapy alone. A limited course of Tremelimumab added to Durvalumab and chemotherapy significantly improved Overall Survival and Progression Free Survival when compared to chemotherapy, and the clinical benefit extended to patients who had tumor PD-L1 expression less than 1%.
Durvalumab With or Without Tremelimumab in Combination With Chemotherapy as First-Line Therapy for Metastatic Non–Small-Cell Lung Cancer: The Phase III POSEIDON Study. Johnson ML, Cho BC, Luft A, et al. DOI: 10.1200/JCO.22.01737 Journal of Clinical Oncology 41, no. 6 (February 20, 2023) 1176-1179.
