Pembrolizumab Promising Treatment for Advanced Gastric Cancer

September 13, 2017

By Jenny Powers

MADRID, Spain -- September 13, 2017 -- An update of results from 3 cohorts in the KEYNOTE-059 study demonstrates that pembrolizumab continues to provide promising clinical activity in patients with advanced gastric or gastro-oesophageal junction (GEJ) cancer, according to updated findings from the phase 2 KEYNOTE-059 study reported at the 42nd European Society for Medical Oncology (ESMO) Congress.

The primary objective of confirmed objective response rate (ORR) with pembrolizumab in cohort 1 (n = 259), which specifically had received 2 or more prior lines of therapy, was 12% (95% CI: 8% to 17%). Among PD-L1-positive patients, the ORR rose to 16% (95% CI: 11% to 23%), while the ORR was 6% (95% CI: 3% to 13%) in patients with PD-L1-negative tumours. The median progression-free survival (PFS) was 2.0 months (95% CI: 2 to 2 months) and median overall survival (OS) was 6 months (95% CI: 4 to 7 months).

Cohort 2 (n = 25), which received pembrolizumab in combination with chemotherapy, demonstrated a confirmed ORR of 60% (95% CI: 39% to 79%) overall. The ORR was 73% (95% CI: 45% to 92%) in patients with PD-L1-positive versus 38% (95% CI: 9% to 76%) in patients with PD-L1-negative tumours. Median PFS was 7 months (95% CI: 6 to 11 months) and median OS was 14 months (95% CI: 9 months to “not estimable”).

Cohort 3 (n = 31) comprised patients with PD-L1 expressing tumours who received pembrolizumab as a first-line single agent, and demonstrated a confirmed ORR of 26% (95% CI: 12% to 45%). Median PFS was 3 months (95% CI: 2 to 6 months) and median OS was not reached (95% CI: 9 to 21 months).

“These results confirm previously reported results from the global KEYNOTE-059 study where manageable safety and promising antitumour activity were demonstrated, both for single agent pembrolizumab and for pembrolizumab plus chemotherapy in patients with gastric or GEJ cancer,” stated lead author Zev A. Wainberg MD, David Geffen School of Medicine at The University of California - Los Angeles, Los Angeles, California, speaking here on September 8 at a late-breaker presentation.

All cohorts received pembrolizumab at 200 mg every 3 weeks for up to 2 years. Pembrolizumab was delivered following ≥2 prior lines of therapy in cohort 1, in combination with cisplatin plus 5-fluorouracil or capecitabine (in Japan only) as first-line in cohort 2, and as first-line monotherapy in cohort 3.
The median follow-up in cohorts 1, 2, and 3 was 6 months (range: 1 to 25 months), 14 months (range: 2 to 24 months), and 18 months (range: 2 to 21 months), respectively.

The incidence of grades 3 to 5 treatment-related adverse events (TRAEs) in cohorts 1, 2 and 3 was 18%, 76%, and 23%, respectively. TRAEs led to discontinuation by 7 patients (3%) in cohort 1 and 3 patients (12%) in cohort 2. TRAEs led to death in 2 patients in cohort 1 and 1 patient in cohort 3.

A supplemental biologics license application based on data from the KEYNOTE-059 study was accepted by the US Food and Drug Administration (FDA) for a priority review in May 2017 for pembrolizumab as a treatment for patients following at least 2 lines of therapy for recurrent or advanced gastric or GEJ adenocarcinoma.

Funding for this trial was provided by Merck & Co, Inc., Kenilworth, New Jersey.

[Presentation title: KEYNOTE-059 Update: Efficacy and Safety of Pembrolizumab Alone or in Combination With Chemotherapy in Patients With Advanced Gastric or Gastroesophageal (G/GEJ) cancer. Abstract LBA28]

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