Mesothelioma patients may soon have another treatment option. A new drug combination achieved long-term survival in select patients. The combination involves two immunotherapy drugs: Imfinzi® (durvalumab) and tremelimumab.
This study included a unique setup, allowing some patients to repeat treatment with the same drugs. Repeating treatment appeared to improve survival. More than half the repeat treatment patients survived at least one year after starting their second round of therapy. This treatment approach has yet to earn regulatory approval. With further research, it could become an approved treatment option for mesothelioma patients.
Note: Tremelimumab is not yet approved by the U.S. Food and Drug Administration (FDA). It has no brand name. At this time, tremelimumab is only available through clinical trials.
Study Treated Inoperable Mesothelioma With New Immunotherapy
Researchers labeled this study NIBIT-MESO-1. Only patients who did not qualify for surgical mesothelioma treatment were included. Enrollment was open to patients with pleural or peritoneal mesothelioma. Initially, 40 patients enrolled. Only 17 went on to repeat treatment.
Study Patient Characteristics*
- Patients: 17
- Gender: 6 female, 11 male
- Median age: 65 years
- Epithelioid cell type: 14
- Biphasic cell type: 3
*Only patients who underwent repeat treatment are included in these characteristics.
Most of the study patients had received at least one round of chemotherapy before enrolling. Some patients experienced tumor progression during chemotherapy.
Researchers broke treatment into two phases: induction and maintenance.
- Induction phase: Patients received a dose of tremelimumab and durvalumab once every four weeks. They received a maximum of four doses.
- Maintenance phase: Patients received a dose of durvalumab once every four weeks. They received a maximum of nine doses.
Patients moved to the maintenance phase if they completed induction and were healthy enough to continue. Ultimately, 17 patients underwent re-treatment with tremelimumab and durvalumab.
Tremelimumab and Durvalumab Are Checkpoint Inhibitors
Tremelimumab and durvalumab belong to a class of drugs called checkpoint inhibitors. These drugs block an immune checkpoint. This allows immune cells to target and destroy cancer cells. A similar combination has previously demonstrated efficacy in pleural mesothelioma: Opdivo® (nivolumab) and Yervoy® (ipilimumab). Opdivo® and Yervoy® are also checkpoint inhibitors.
Checkpoint inhibitors usually target one specific immune checkpoint. Two commonly targeted checkpoints are called PD-1/PD-L1 and CTLA-4. The immunotherapy combinations mentioned here target these checkpoints:
- Checkpoint inhibitors targeting CTLA-4: Tremelimumab and Yervoy®
- Checkpoint inhibitors targeting PD-1/PD-L1: Imfinzi® (durvalumab) and Opdivo® (nivolumab)
Re-treated Patients Experienced Improved Survival
Researchers wanted to understand how re-treatment affected survival. To do that, they looked at two groups of patients:
- Additional chemotherapy patients: These patients did not qualify for repeat immunotherapy treatment. However, they did receive additional chemotherapy after the induction phase of the immunotherapy trial.
- Re-treated patients: These patients repeated tremelimumab and durvalumab treatment.
Median survival differed substantially between these two groups. Those treated with additional chemotherapy lived about 11 months. Patients treated with repeat immunotherapy lived about 26 months.
The re-treated patients lived more than twice as long as those who received additional chemotherapy.
The study also found the following survival rates for re-treated patients:
- 1-year survival: 53%
- 2-year survival: 24%
These results improve upon earlier studies of second-line mesothelioma treatment. Other second-line therapies for pleural mesothelioma achieved a median survival of about eight months. Thus, re-treatment with tremelimumab and durvalumab may provide a superior survival compared to past treatments.
New Treatment Similar to Recently Approved Regimen
Opdivo® and Yervoy® gained FDA approval for pleural mesothelioma treatment in late 2020. The combination improved patient survival in clinical trials. The Opdivo® and Yervoy® trial enrolled more than 600 patients.
Current results of tremelimumab and durvalumab show similar promise to the Opdivo® and Yervoy® trial. Tremelimumab and durvalumab can be tested in larger studies to gain FDA approval. In the meantime, mesothelioma patients may be able to access this therapy through clinical trials.
Patients interested in checkpoint inhibitors should discuss treatment options with their oncology team. A mesothelioma doctor can help determine the best treatment approach for each patient’s situation.