Merck & Co. on Saturday said that 23.2 percent of treatment-naïve patients with advanced non-small-cell lung cancer (NSCLC) who received the anti-PD-1 therapy Keytruda (pembrolizumab) in the Phase Ib KEYNOTE-001 study were alive at five years. The results were detailed at the American Society of Clinical Oncology (ASCO) annual meeting, with the society noting that in the pre-immunotherapy era, five-year survival rates in this setting averaged 5.5 percent.
Further results from the trial showed that in previously treated patients, the five-year overall survival (OS) rate was 15.5 percent for Keytruda. Lead study author Edward Garon remarked "the fact that we have patients on this trial that are still alive after seven years is quite remarkable," adding "we also have evidence that most patients who are doing well after two years on [Keytruda] live for five years or more."
Merck said that results also showed that the five-year OS rate among patients whose tumours expressed PD-L1 was 29.6 percent in treatment-naïve patients and 25 percent in previously-treated subjects. This compared with five-year OS rates in people with PD-L1 expression of below 50 percent of 15.7 percent in treatment-naïve patients and 12.6 percent in previously-treated subjects.
Additional results showed that among people receiving Keytruda after undergoing previous treatment, 42 percent had responses that lasted for a median of 16.8 months. Meanwhile, for those who received Keytruda as initial therapy, 23 percent had responses that lasted a median of 38.9 months.
Keytruda gained FDA approval  in 2016 as a first-line treatment for advanced NSCLC tumours that do not have EGFR or ALK gene mutations, but that express PD-L1 on 50 percent or more of their cells. Meanwhile, earlier this year, the drug received expanded clearance  for the front-line treatment of patients with stage III NSCLC who could not have the tumours surgically removed or irradiated, or advanced NSCLC with PD-L1 expression levels over 1 percent and no EGFR or ALK gene mutations. Sales of Keytruda are expected to be over $10 billion this year, rising to $20 billion in 2024.
Researchers on Saturday also detailed results from the Phase III KEYNOTE-062 trial of Keytruda as a first-line treatment for patients with advanced gastric or gastroesophageal junction adenocarcinoma, which Merck announced  in April failed to prolong OS or progression-free survival versus chemotherapy alone. However, additional findings suggested that Keytruda alone was non-inferior to chemotherapy for OS in the entire intention-to-treat population of patients whose tumours expressed PD-L1.
At ASCO, results showed that at two years, 39 percent of patients, all of whom had high PD-L1 levels, that received Keytruda alone were alive, compared with 22 percent of those given standard chemotherapy. In patients with a PD-L1 combined positive score of 10 or more, survival with Keytruda was superior to chemotherapy, with median OS in the two groups of 17.4 months and 10.8 months, respectively.
Richard Schilsky, ASCO's chief medical officer, said the findings introduce the potential of using Keytruda, which has fewer toxic side effects, in place of chemotherapy, noting "for some, it can greatly extend survival." Keytruda gained accelerated FDA approval  in 2017 for patients with recurrent, locally advanced or metastatic, gastric or gastroesophageal junction cancer with tumours that express PD-L1 with a combined positive score of one or more.