On 1 March, Merck announced the voluntary withdrawal of its Keytruda (pembrolizumab) immunotherapy for the treatment of patients with metastatic small cell lung cancer (SCLC) with disease progression on or after platinum-based chemotherapy and at least one other prior line of therapy.
The move came following the US Food and Drug Administration’s (FDA’s) recent crackdown on drugs approved through accelerated pathways without the required post-marketing data.
Accelerated approval for Keytruda in metastatic SCLC was granted in June 2019 based on tumour response rate and durability of response trial data from KEYNOTE-158 (cohort G) and KEYNOTE-028 (cohort C1).
However, the FDA required overall survival (OS) data to confirm Keytruda’s use in metastatic SCLC and data from the KEYNOTE-604 phase 3 trial failed to meet this endpoint.
As announced in January 2020, KEYNOTE-604, the confirmatory Phase III trial for this indication, met one of its dual primary endpoints of progression-free survival but did not reach statistical significance for the other primary endpoint of OS.
Keytruda is the dominant checkpoint inhibitor in the immuno-oncology space, approved for a long list of cancer indications.
In the third quarter of 2020 alone, the drug achieved sales of $3.7bn, an increase of 21% from the same period in 2019.
Merck is in the process of notifying healthcare professionals about the withdrawal and advises that patients being treated with Keytruda for metastatic SCLC should discuss the next steps in care with their healthcare provider.
“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 Dr. 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.”
Keytruda’s other indications remain unaffected. These include treatment for forms of cervical cancer, Merkel cell cancer, primary mediastinal large B-cell lymphoma, gastric cancer, certain metastatic or unresectable solid tumours, triple-negative breast cancer, and endometrial cancer, in addition to treating paediatric colorectal cancer and other paediatric cancers.
Keytruda’s withdrawal for metastatic SCLC comes on the back of the FDA’s industry-wide evaluation of its accelerated approvals to determine which have not met post-marketing requirements.
Last week AstraZeneca announced it was withdrawing its checkpoint inhibitor Imfinzi in bladder cancer following a similar interaction with the FDA. Given the increase in accelerated approvals in recent years, other withdrawals are expected to follow.
The Imfinzi accelerated approval was for advanced bladder cancer with high PD-1 levels or in patients regardless of PD-1 status, and was to be confirmed by the DANUBE trial, but the drug failed to meet OS endpoints compared to standard of care.
For patients with extensive SCLC, Imfinzi is approved as a first line treatment, based on OS data from the Phase III CASPIAN clinical trial.