Merck’s Keytruda (pembrolizumab) shows promise as a treatment for advanced, previously treated cervical squamous cell cancer, according to a preliminary analysis of a Phase 2 trial.
The data, which will be presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting, June 2-6, indicated response rates increased with longer follow-up. The ongoing trial — which is still recruiting participants — is expected to conclude in May 2019.
The poster presentation, “Pembrolizumab for previously treated advanced cervical squamous cell cancer: Preliminary results from the phase 2 KEYNOTE-158 study,” included data from the first 47 patients, who had been followed for at least 18 weeks up to Oct. 19, 2016.
The Phase 2 KEYNOTE-158 (NCT02628067) trial enrolled adult patients with confirmed advanced cervical squamous cell cancer. In an earlier, ongoing Phase 1b trial (NCT02054806), Keytruda had shown promising effects in cervical cancer patients who had tumors that produced the protein PD-L1.
Keytruda blocks the immune checkpoint molecule PD-1, and the presence of the factor PD-L1 — which binds PD-1 — has been suggested to predict treatment response. But the Phase 2 trial recruited patients without first checking their tumors’ PD-L1 levels.
All patients had gone through at least one prior round of standard cervical cancer treatment. Although they had advanced cancer, they were in good physical shape, according to the ECOG performance status scale. Participants could be restricted only in their ability to perform strenuous physical activity.
The group was treated with 200 mg of Keytruda every three weeks. The treatment continues for two years or until the cancer progresses or patients experience intolerable side effects.
Analyses showed that patients had an overall response rate of 17 percent. Researchers noted that the response rate was not linked to patients’ PD-L1 levels, which were measured retrospectively.
Fifteen patients had at least 27 weeks of follow-up. Among them, the overall response rate was 27 percent.
The data indicate that Keytruda may benefit patients with this type of cervical cancer, the research team concluded.
Researchers plan to present an update at the meeting, including 83 patients who will have had at least 27 weeks of follow-up. They will share safety and efficacy data for that group.
Several of the study’s authors reported ties to pharmaceutical companies.