Keytruda Approved for Some Patients With Gastric Cancer

Jason M. Broderick

Keytruda (pembrolizumab) was granted FDA approval for the treatment of patients with recurrent or advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma who have received two or more lines of chemotherapy and are PD-L1-positive.

The approval is based on findings from the phase 2 KEYNOTE-059 study. In the study, 143 of 259 patients had PD–L1-positive tumors (combined positive score 1 or higher) and microsatellite stable tumor status or undetermined microsatellite instability or mismatch repair status. The overall response rate (ORR) in these patients was 13.3 percent, including a complete response (CR) rate of 1.4 percent and a partial response (PR) rate of 11.9 percent.

The duration of response among the 19 responding patients ranged from 2.8+ to 19.4+ months. Responses were six months or longer in 11 (58 percent) patients and 12 months or longer in five (26 percent) patients.

“Historically, advanced gastric cancer has been particularly challenging to treat, and new treatment options are needed for these patients,” lead KEYNOTE-059 investigator Charles S. Fuchs, M.D., Yale Cancer Center, said in a statement. “The results observed in the diverse population of heavily pretreated advanced gastric or GEJ patients from the KEYNOTE-059 clinical trial demonstrate that pembrolizumab in the third-line setting has the potential to shift how we care for certain patients facing this difficult-to-treat disease.”

Full results from the KEYNOTE-059 trial were presented at the 2017 ASCO Annual Meeting. All 259 patients received Keytruda at a flat 200 mg dose every three weeks. The median age of patients was 62 years and 76.4 percent were male. The ECOG performance status for patients was primarily 0 (41.3 percent) and 1 (58.3 percent). Overall, 51.7 percent of patients had received two prior lines of therapy, and 29 percent and 19.3 percent had received three or four or more prior lines of therapy, respectively.

Across the entire study population, the ORR with Keytruda was 11.6 percent. In those who specifically received two prior lines of therapy, the ORR was 16.4 percent. The median progression-free survival (PFS) was 2.0 months and the median overall survival (OS) was 5.6 months, with a 12-month OS rate of 23.4 percent.

After a median follow-up of 5.8 months, 2.3 percent of patients had a CR and 9.3 percent had a PR. When including stable disease, the disease control rate was 27 percent. The median duration of response was 8.4 months.

Those treated in the third-line setting had a 3 percent CR rate and a 13.4 percent partial response rate. In the fourth-line and beyond, the ORR dropped to 6.4 percent, with a 1.6 percent CR rate. For those with PD-L1–positive tumors in the third-line setting (75 patients), the ORR was 22.7 percent with a 2.7 percent CR rate. In patients with PD-L1–negative tumors treated with third-line Keytruda (58 patients), the ORR was 8.6 percent with a 3.4 percent CR rate.

Among seven patients with microsatellite instability-high (MSI-H) tumors, the ORR with Keytruda was 57.1 percent and the CR rate was 14.3 percent. The disease control rate was 71.4 percent. In those with non–MSI-H tumors (167 patients), the ORR was 9 percent and the CR rate was 2.4 percent. The disease control rate was 22.2 percent.

The most frequently occurring treatment-related adverse events (AEs) of all grades were fatigue (18.9 percent), pruritus (8.9 percent), rash (8.5 percent), hypothyroidism (7.7 percent), decreased appetite (7.3 percent), anemia (6.9 percent), nausea (6.9 percent), diarrhea (6.6 percent) and arthralgia (5.8 percent). There were two treatment-related grade 5 AEs (acute kidney injury and pleural effusion).

The accelerated approval of Keytruda for this indication is contingent on the results of a confirmatory trial.

Keytruda is approved for several indications, including as a treatment for patients with lung cancer, melanoma, Hodgkin lymphoma and other types of cancer. In mid-May, the FDA granted an accelerated approval to Keytruda as a treatment for patients without other options with unresectable or metastatic, MSI-H or mismatch repair deficient (dMMR) solid tumors. This was in addition to those with MSI-H or dMMR colorectal cancer following progression on a fluoropyrimidine, oxaliplatin and irinotecan.
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