Six Years of Mesothelioma Immunotherapy: From First Approval to 2026

For about 16 years between 2004 and 2020, mesothelioma treatment did not meaningfully change. The standard of care was cisplatin combined with pemetrexed, a regimen that extended median survival by about three months over older options and left most patients with few choices when it stopped working.

That era ended on October 2, 2020, when the FDA approved the combination of nivolumab (Opdivo) and ipilimumab (Yervoy) as first-line treatment for unresectable pleural mesothelioma. It was the first new first-line treatment for the disease in more than a decade, and it was the first immunotherapy regimen the FDA had ever approved for mesothelioma.

The six years since have brought more change to the mesothelioma treatment landscape than the previous thirty. Here is the full timeline.

The Timeline: 2020 to 2026

2020: The First Approval

The approval of nivolumab plus ipilimumab was based on the Phase 3 CheckMate-743 trial, which enrolled 605 patients with previously untreated, unresectable pleural mesothelioma. Half received the immunotherapy combination, the other half received standard platinum doublet chemotherapy.

Median overall survival was 18.1 months in the immunotherapy arm compared to 14.1 months with chemotherapy. The benefit was most pronounced in patients with non-epithelioid cell types, where immunotherapy more than doubled median survival (18.1 months versus 8.8 months). The primary results were published in The Lancet in January 2021 (Baas et al., 2021).

Nivolumab blocks PD-1, a checkpoint receptor on T cells. Ipilimumab blocks CTLA-4, a different checkpoint. By releasing both brakes on the immune system, the combination allows T cells to recognize and attack mesothelioma cells more effectively. Chemotherapy was not given with the immunotherapy, marking a shift away from the decades-old pemetrexed backbone for patients who responded to the immune approach.

2020 to 2021: Second-Line and Durvalumab

Two additional trials reshaped the landscape over this period.

The DREAM trial, a Phase 2 study published in Lancet Oncology in September 2020, tested durvalumab (a PD-L1 inhibitor) combined with first-line chemotherapy. The primary endpoint, progression-free survival at six months, was 57%. Median overall survival was 18.4 months. The approach set up a Phase 3 trial (DREAM3R) to confirm the benefit.

The CONFIRM trial, published in Lancet Oncology in October 2021, tested single-agent nivolumab against placebo in patients whose pleural mesothelioma had progressed after first-line treatment. Median overall survival was 10.2 months on nivolumab compared to 6.9 months on placebo (HR 0.69), a meaningful improvement for a population with no standard second-line options.

2022: CheckMate-743 Three-Year Update

Extended follow-up from CheckMate-743 was published in Annals of Oncology in May 2022 (Peters et al., 2022). At three years, 23% of patients in the immunotherapy arm were alive compared to 15% on chemotherapy. Median follow-up at the time of that analysis was 43.1 months.

2023 to 2024: Pembrolizumab Becomes the Second Approval

The IND.227 trial, also known as KEYNOTE-483, tested pembrolizumab plus platinum and pemetrexed chemotherapy against chemotherapy alone in first-line pleural mesothelioma. Primary results were published in The Lancet in November 2023 (Chu et al., 2023). Median overall survival improved from 16.1 months to 17.3 months (HR 0.79).

On September 17, 2024, the FDA approved pembrolizumab plus pemetrexed and platinum chemotherapy for first-line unresectable advanced or metastatic malignant pleural mesothelioma. It became the second immunotherapy regimen with an FDA indication in mesothelioma, joining nivolumab plus ipilimumab from 2020.

In February 2024, the ATOMIC-Meso Phase 3 trial was published in JAMA Oncology (Szlosarek et al., 2024). Pegargiminase (ADI-PEG20), a drug that depletes arginine from mesothelioma cells that cannot synthesize it, was combined with chemotherapy in 249 patients with nonepithelioid pleural disease. Median progression-free survival was 6.2 versus 5.6 months (HR 0.65). Median overall survival was 9.3 versus 7.7 months (HR 0.71). The compound represented a different approach entirely: metabolic vulnerability rather than immune activation.

2025: BNT327 Phase 2 Data at ASCO

BNT327 (also known as PM8002), a bispecific antibody that simultaneously blocks PD-L1 and VEGF-A, produced a confirmed objective response rate of 51.6% in 31 previously untreated patients (23 pleural, 8 peritoneal). The results were presented at the 2025 ASCO Annual Meeting. Median follow-up at the time of presentation was 22.3 months (data cutoff March 28, 2025), and median progression-free survival was 16.6 months overall. In the peritoneal subgroup, the objective response rate was 75% and the disease control rate was 90.3% overall.

Peritoneal mesothelioma has no specifically approved immunotherapy, so these figures drew particular interest even though the subgroup was small (n=8).

2026: Five-Year Data and Mechanistic Insights

Five-year follow-up from CheckMate-743 was published in the Journal of Clinical Oncology in March 2026. At five years, 14% of patients on nivolumab plus ipilimumab were alive compared to 6% on chemotherapy. Median follow-up was 66.8 months, with a hazard ratio of 0.74.

In February 2026, a preclinical study in Scientific Reports (Orozco Morales et al., 2026) provided a biological explanation for why checkpoint therapy works differently in pleural and peritoneal mesothelioma. Researchers reported that the peritoneal cavity creates an immune-suppressive microenvironment that resists single-agent checkpoint drugs in preclinical models.

The finding helps frame why dual-mechanism approaches like BNT327, which target both the checkpoint and the tumor blood supply, are being studied in peritoneal disease.

What Has Not Changed

Despite six years of progress, key gaps remain.

No immunotherapy has been specifically approved for peritoneal mesothelioma. Most Phase 3 trials still focus on pleural disease, leaving peritoneal patients dependent on off-label use of drugs approved for pleural disease or on clinical trial enrollment.

Response rates to first-line immunotherapy still hover between 40% and 55% in pleural disease. More than half of patients do not respond to the best available options, and durable responses (the kind that translate to long-term survival) remain the exception.

Biomarkers that reliably predict who will respond to checkpoint therapy have not emerged. PD-L1 expression, widely used as a biomarker in other cancers, shows only weak correlation with response in mesothelioma.

What Comes Next

Three areas of development look most active heading into the second half of 2026. Bispecific antibodies are the first: BNT327 is not the only drug of its class, and several companies are pursuing dual-targeting approaches that pair checkpoint blockade with inhibition of tumor blood vessels, angiogenesis, or other mechanisms. CAR-T and cell therapies are the second area, with multiple Phase 1 trials testing engineered T cells against mesothelin, a protein expressed on nearly all mesothelioma cells; early data have been mixed, but the approach remains under active investigation. Microenvironment sensitization is the third, and the 2026 Scientific Reports findings support the idea that combination approaches targeting macrophages, B cells, or other components of the tumor microenvironment may be needed to extend immunotherapy benefit to peritoneal disease and to non-responders overall.

Six years ago, people with mesothelioma had one first-line option and no approved second-line treatments. Today there are two FDA-approved immunotherapy regimens (nivolumab plus ipilimumab and pembrolizumab plus chemotherapy), multiple Phase 2 regimens showing promise, and a growing biological understanding of why the disease responds differently across subtypes.

What patients need next are larger trials, more biomarkers, and approval pathways that include peritoneal disease. For families in states with the highest case volumes, including Illinois (670 exposure sites, ranked sixth nationally) and Texas, understanding these treatment advances is especially urgent.