On 2 October 2015, the US Food and Drug Administration (FDA) granted accelerated approval for pembrolizumab (Keytruda) to treat patients with advanced (metastatic) non-small-cell lung cancer (NSCLC) whose disease has progressed after other treatments and with tumorus that express PD-L1. Keytruda is approved for use with a companion diagnostic, the PD-L1 IHC 22C3 pharmDx test, the first test designed to detect PD-L1 expression in non-small-cell lung tumours.
Keytruda works by targeting the cellular pathway known as PD-1/PD-L1. By blocking this pathway, Keytruda may help the body’s immune system fight the cancer cells. In 2014, Keytruda was approved to treat patients with advanced melanoma following treatment with ipilimumab, a type of immunotherapy. Another drug, nivolumab (Opdivo), manufactured by Bristol-Meyers Squibb, also targets the PD-1/PD-L1 pathway and was approved to treat squamous NSCLC in 2015.
The safety of Keytruda was studied in 550 patients with advanced NSCLC. The most common side effects of Keytruda included fatigue, decreased appetite, dyspneoa and cough. Keytruda also has the potential to cause severe side effects that result from the immune system effect of Keytruda, known as immune-mediated side effects.
The effectiveness of Keytruda for this use was demonstrated in a subgroup of 61 patients enrolled within a larger multicenter, open-label, multi-part study. The subgroup consisted of patients with advanced NSCLC that progressed following platinum-based chemotherapy or, if appropriate, targeted therapy for certain genetic mutations (ALK or EGFR). This subgroup also had PD-L1 positive tumours based on the results of the 22C3 pharmDx diagnostic test. Study participants received 10 mg/kg of Keytruda every two or three weeks. The major outcome measure was overall response rate. Tumours shrank in 41% of patients treated with Keytruda and the effect lasted between 2.1 and 9.1 months.
In the 550 study participants with advanced NSCLC, severe immune-mediated side effects occurred involving the lungs, colon and hormone-producing glands. Other uncommon immune-mediated side effects were rash and vasculitis. Women who are pregnant or breastfeeding should not take Keytruda because it may cause harm to a developing fetus or newborn baby. Across clinical studies, a disorder in which the body’s immune system attacks part of the peripheral nervous system (Guillain-Barre Syndrome) also occurred.
The FDA granted Keytruda breakthrough therapy designation for this indication because Merck demonstrated through preliminary clinical evidence that the drug may offer a substantial improvement over available therapies. The drug also received priority review status, which is granted to drugs that, at the time the application was submitted, have the potential to be a significant improvement in safety or effectiveness in the treatment of a serious condition.
Keytruda was approved under the agency’s accelerated approval programme, which allows the approval of a drug to treat a serious or life-threatening disease based on clinical data showing the drug has an effect on a surrogate endpoint reasonably likely to predict clinical benefit to patients. This programme provides earlier patient access to promising new drugs while the company conducts confirmatory clinical trials. An improvement in survival or disease-related symptoms in patients being treated with Keytruda has not yet been established.