Checkpoint Inhibitors Promising for SCLC, Mesothelioma


Immune checkpoint inhibitors have emerged with encouraging results in patients with small cell lung cancer (SCLC) and mesothelioma



M. Catherine Pietanza, MD

Immune checkpoint inhibitors have emerged with encouraging results in patients with small cell lung cancer (SCLC) and mesothelioma, according to a presentation by M. Catherine Pietanza, MD, at the 10th Annual New York Lung Cancer Symposium.

“The antibodies to CTLA-4, PD-1, and PD-L1 can be safely given to these patients. Responses are seen and are durable. There is a benefit in both platinum-sensitive and platinum-refractory SCLC,” said Pietanza, a medical oncologist at Memorial Sloan Kettering Cancer Center.

Chemotherapy has traditionally been the choice treatment for the majority of patients with SCLC and mesothelioma, of which have few treatment options available, beyond the frontline setting. However, outcomes have generally been poor with these therapies, specifically for SCLC, where the median survival following second-line therapy ranges from 6 to 9 months.

“Pace of development of drugs for these malignancies has lagged behind NSCLC,” said Pietanza. “Both malignancies are associated with immunogenic effects. While PD-L1 expression is minimal to nonexistent in SCLC, it is quite high in mesothelioma.”

For those with SCLC, two studies have reported their findings, with several trials ongoing. In the phase I/II CheckMate-032 trial, patients with pretreated SCLC received the single-agent PD-1 inhibitor nivolumab (Opdivo) or the combination of nivolumab and the CTLA-4 inhibitor ipilimumab (Yervoy).

In the trial, 80 patients received nivolumab at 3 mg/kg every 2 weeks. For the combination arm, 47 patients received nivolumab at 1 mg/kg and ipilimumab at 3 mg/kg every 3 weeks. Treatment in both arms was continued for 4 cycles followed by nivolumab alone at 3 mg/kg every 2 weeks. In the single-agent group, a majority of patients had received 2 to 3 prior therapies (60%) and 55% were sensitive to frontline platinum-based therapy. In the combination group, most patients had received 1 prior therapy (55%) and 45% were sensitive to platinum treatment.

In evaluable patients, nivolumab monotherapy demonstrated an objective response rate (ORR) of 12.7% and a stable disease (SD) rate of 16.4%. The median duration of response (DOR) had not yet been reached (range, 19.4-61.6+ weeks).

In the combination arm, the ORR was 31.1%, with a 2.2% complete response rate. The SD rate for the combination was 22.2%. The median DOR was 30.4 weeks (range, 5.7-41.8+ weeks).

Median progression-free survival (PFS) with single-agent nivolumab was 1.38 months (95% CI, 1.31-1.54). In the combination arm, median PFS was 3.35 months (1.41-6.87). The 9-month PFS rates were 10.2% and 30.4% for the single-agent and combination, respectively.

Median overall survival (OS) with nivolumab alone was 3.55 months (95% CI, 2.66-7.46) and was 7.75 months with the combination (95% CI, 3.65-NR). The 1-year OS rates were 27.1% and 47.5%, for the monotherapy and combination arms, respectively.

The treatment-related adverse events (AEs) associated with treatment were generally mild and consistent with previous experiences. All grade AEs occurred in 41.3% of patients treated with monotherapy and in 83% of those who received the combination. Grade 3/4 AEs were seen in 11.3% of those treated with nivolumab alone and in 31.9% of individuals who received the combination.

“Obviously, very impressive is the progression-free survival being 30% with the combo and about 10% at 9 months for nivolumab alone, this is quite impressive,” Pietanza said. “I don't know if we would see these results with topotecan. Some of these patients have had more than two lines of therapy.”

In the phase Ib KEYNOTE-028 trial, 24 patients received the PD-1 inhibitor pembrolizumab (Keytruda) at 10 mg/kg every 2 weeks. All patients had received prior chemotherapy, specifically platinum/etoposide (100%), irinotecan or topotecan (46%), and/or a taxane (29%). All patients were PD-L1-positive.

With pembrolizumab the ORR was 29.2% (95% CI, 12.6-51.1), which consisted entirely of partial responses, The SD rate was 4.2% and the DOR was 29 weeks (range, 0.1-29.1 weeks). Median PFS was 1.8 months, with a 6-month PFS rate of 32.5%.

Overall, 62.5% of patients experienced a treatment-related AE of any grade with pembrolizumab. Grade 3/5 AEs occurred in 8.3% of patients, including 1 grade 5 incidence of colitis.

“There are numerous ongoing studies in small cell lung cancer utilizing these agents that are open or are about to be open at multiple institutions,” Pietanza noted. “I suggest we all look for them and enroll our patients on them—it is the only way that we are going to make very strong conclusions about these agents.”

For patients with malignant pleural mesothelioma, studies have explored pembrolizumab, the CTLA-4 inhibitor tremelimumab, and the PD-L1 inhibitor avelumab. In patients with mesothelioma, studies have revealed that PD-L1 expression is associated with a worse prognosis, further warranting the exploration of these agents.

In the 29-patient study of tremelimumab, the ORR was 6.9% and the DOR was 12.4 months. The median OS was 10.7 months and the median PFS was 6.2 months. The 1-year OS rate was 48.3% and the 2-year OS rate was 36.7%. All-grade treatment-related AEs were seen in 76% of patients; however, grade 3/4 events were less common (13%).

“The survival is pretty interesting, if you look at the median progression-free survival and the median overall survival it is approximately what is seen in some second-line trials,” Pietanza said. “It is the 1- and 2-year survival rates that really identify a subset of patients with mesothelioma who benefit from anti—CTLA-4 therapy."

In a study exploring pembrolizumab in 25 PD-L1-positive patients, the ORR was 28% with a DOR that was not yet reached (range, 10.4-40.3+ weeks). The median PFS was 5.8 months, with a 50% 6-month PFS rate. The all-grade AE rate was 60% and grade 3/4 AEs occurred in 16% of patients.

Similar findings were seen in a study exploring avelumab in 20 patients who were not selected by PD-L1 status. The ORR was 15% and the median PFS was 16.3 weeks. All-grade AEs were seen in 85% of patients and grade 3/4 AEs were experienced by 15% of individuals.

To further expand upon these results, a number of clinical trials are currently being conducted. In addition to single-agent studies for pembrolizumab and tremelimumab, studies are exploring the combinations of durvalumab (MEDI4736) and tremelimumab (NCT02592551) and single-agent nivolumab (NCT02497508).

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