Merck’s oncology drug Keytruda, when layered onto routine care in advanced cervical cancer, resulted in a materially greater delay in patients’ disease progression than chemoradiotherapy alone, according to a recent interim analysis of a late-stage trial. 

The findings were seen in the drugmaker’s Phase 3 KEYNOTE-A18 trial, designed to assess whether adding Merck’s anti-PD-1 megablockbuster Keytruda could move the needle in treating newly diagnosed patients with the high-risk locally advanced form of the disease. 

The drug already has a beachhead in certain patients with the persistent, recurrent or metastatic form of the gynecological malignancy. 

The results “reinforce our research efforts in earlier stages of disease where there is a greater potential for better outcomes,” said Gursel Aktan, VP for global clinical development at Merck Research Labs, in a statement Wednesday.

The standard treatment regimen for advanced cervical cancer involves concurrent chemoradiotherapy, (external beam radiotherapy and cisplatin), plus intracavitary brachytherapy. That course, augmented by Keytruda, showed a statistically significant and clinically meaningful improvement in progression-free survival (PFS) versus standard of care on its own, the drugmaker said. 

As such, the trial met one of its primary endpoints. The other endpoint — a favorable trend in overall survival (OS) — was also observed for the Keytruda combo versus concurrent chemoradiotherapy alone. However, Merck said, the OS data were not mature at the time of this interim analysis and the drugmaker will track this as the trial continues. 

Meanwhile, no new Keytruda safety signals were identified. The drugmaker plans to release results at an upcoming medical meeting and to submit them to regulatory bodies, which could potentially expand Keytruda’s indication set beyond its two approved indications in recurrent or metastatic cervical cancer.

Patients with the high-risk locally advanced form often have a poor prognosis, with more than half experiencing disease recurrence within two years, observed Dr. Domenica Lorusso, the study’s overall principal investigator and an associate professor of obstetrics and gynecology at the Catholic University of Rome. 

“However, there have been limited new treatment advances for these patients beyond the current standard of care in the last 20 years,” Lorusso stated, adding that the KEYNOTE-A18 results support use of Keytruda combined with the current standard as a new treatment option in this disease state.

Keytruda is Merck’s flagship product, generating $21 billion in sales last year, accounting for more than one-third of the company’s total revenue. That tally is set to rise as the drugmaker extends the immuno-oncology agent into earlier line settings.

A pivotal Food and Drug Administration decision date is coming up later this year, for use of the drug in the adjuvant lung cancer setting.

J.P. Morgan’s Chris Schott forecasts the Keytruda franchise growing 15% this year, tacking on another $6 billion in revenue, according to an estimate issued this month. Overall the analyst projects $24.4 billion in Keytruda revenues this year, increasing to $31.8 billion by 2028. Sales erosion is set to start in 2029, though, due to biosimilar competition.