MSD withdraws Keytruda’s US indication for small cell lung cancer

MSD (Merck & Co) has voluntarily withdrawn the US indication for its checkpoint inhibitor Keytruda in metastatic small cell lung cancer (SCLC).

The US Food and Drug Administration (FDA) granted Keytruda (pembrolizumab) an accelerated approval for the treatment of third line SCLC in June 2019.

That approval was based on results from the KEYNOTE-158 and KEYNOTE-028 trials, which showed that Keytruda monotherapy led to a 19% objective response rate (ORR) in SCLC patients whose cancer had progressed despite prior therapies.

However, continued approval in this indication was dependent on a post-marketing study demonstrating superiority of Keytruda as determined by overall survival (OS).

Keytruda failed to meet this requirement in the KEYNOTE-604 trial, as announced in January 2020.

Results from this trial showed that when Keytruda was added to chemotherapy, it extended the time patients live without their cancer getting worse – progression-free survival (PFS) – but was unable to improve OS.

SCLC accounts for around 10-15% of all cases of lung cancer, according to Merck, and has a poor prognosis with a five-year survival rate of approximately 6%, across all stages of the disease at diagnosis.

Keytruda is dominant in another type of lung cancer – non-small cell lung cancer – and has become a new standard-of-care treatment in this indication since first gaining approval in October 2015.

However, the SCLC market has been cornered by rival checkpoint inhibitors, including Roche’s Tecentriq (atezolizumab) which is approved for first-line SCLC.

AstraZeneca’s (AZ) Imfinzi (durvalumab) also entered the therapy area in 2020, gaining a green light in the US in combination with chemotherapy as a first-line treatment of extensive-stage SCLC.

“The accelerated pathways created by the FDA have been integral to the remarkable progress in oncology care over the past five years and have helped many cancer patients with advanced disease, including small cell lung cancer, access new treatments,” said Roy Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories.

“Keytruda remains a foundational treatment for certain patients with metastatic non-small cell lung cancer. We will continue to rigorously evaluate the benefits of Keytruda in small cell lung cancer and other types of cancer, in pursuit of Merck’s mission to save and improve lives,” he added.

Last week, AZ also announced that it had withdrawn Imfinzi’s US indication for advanced bladder cancer after a post-marketing study failed to hit the mark.

Similarly, Bristol Myers Squibb decided to withdraw the US indication for PD-1 inhibitor Opdivo  (nivolumab) in SCLC which has progressed following prior therapies.

As with Keytruda, Opdivo was granted an accelerated approval in this indication but subsequent confirmatory studies failed to meet their primary endpoints of OS in SCLC.