The novel agent pembrolizumab demonstrated promising antitumor activity and manageable toxicity in patients with advanced gastric cancer, according to study results presented at the Gastrointestinal Cancers Symposium.
Pembrolizumab (Keytruda, Merck) — which is being studied in a variety of several cancer types — is a monoclonal antibody that blocks the PD-1 pathway.
Kei Muro, MD, of the department of clinical oncology at Aichi Cancer Center Hospital in Japan, and colleagues assessed the relationship between PD-L1 expression and clinical outcomes in patients with advanced gastric cancer treated with pembrolizumab.
All patients had recurrent or metastatic adenocarcinoma of the stomach or gastroesophageal junction. Eligibility was limited to patients with distinctive stromal or ≥1% tumor nest cell PD-L1 staining.
Of the 162 patients screened, 65 were identified as PD-L1 positive. From that cohort, 39 patients enrolled in the study. About half of patients (48.7%; n=19) were from Asia-Pacific regions.
Median age of the cohort was 63 years (range, 33-78 years). Most patients in the cohort had undergone prior therapies for their cancers, and 67% had received at least two prior therapies.
Patients received pembrolizumab 10 mg/kg every 2 weeks for up to 24 months or until they achieved complete response, demonstrated progression or experienced unacceptable toxicity.
Imaging was performed every 8 weeks. Overall response rate served as the primary endpoint. Secondary endpoints included duration of response, PFS and OS.
Median follow-up was 8.8 months (range, 6.2-12.6 months).
At the time of final analysis, 13 patients (33%) remained on therapy.
The overall response rate as determined by central review was 22% (95% CI, 10-39). Overall response rate as determined by investigator review was 33% (95% CI, 19-50).
The median time to response was 8 weeks (range, 7-16 weeks), and the median duration of response was 24 weeks. The 6-month PFS rate was 24%, and the 6-month OS rate was 69%.
Researchers reported one drug-related death due to hypoxia. Four patients experienced a combined five grade 3 to grade 5 drug-related adverse events. They included one case each of peripheral sensory neuropathy, fatigue, hypoxia, pneumonitis and decreased appetite.
“Pembrolizumab demonstrated manageable toxicity and promising antitumor activity in advanced gastric cancer,” the researchers wrote. “These results support the ongoing development of pembrolizumab for gastric cancer.”
For more information:
Muro K. Abstract #3. Presented at: 2015 Gastrointestinal Cancers Symposium; Jan. 15-17, 2015; San Francisco.
Disclosure: The researchers report employment relationships with Merck, as well as stock ownership and other interests in Bayer, Celgene, Johnson & Johnson and Merck.