The Food and Drug Administration has granted accelerated approval for pembrolizumab (Keytruda) in combination with chemotherapy to treat locally recurrent unresectable or metastatic triple-negative breast cancer (TNBC) that expresses PD-L1, as determined by a combined positive score of 10 or greater on an FDA-approved assay.
The FDA also approved a PD-L1 assay for selecting TNBC patients for pembrolizumab, the PD-L1 IHC 22C3 pharmDx .
Pembrolizumab is approved for numerous indications in the United States, but the new approval is its first breast cancer indication.
The accelerated approval for pembrolizumab in TNBC was based on progression-free survival (PFS) in the KEYNOTE-355 trial. The FDA noted that continued approval of pembrolizumab in TNBC “may be contingent upon verification and description of clinical benefit in the confirmatory trials.”
KEYNOTE-355 enrolled patients with locally recurrent unresectable or metastatic TNBC who had not received chemotherapy in the metastatic setting. Patients were randomized to chemotherapy (nab-paclitaxel, paclitaxel, or gemcitabine plus carboplatin) plus placebo (n = 281) or chemotherapy plus pembrolizumab at 200 mg on day 1 every 3 weeks (n = 562).
Among PD-L1-positive patients (n = 323), the median PFS was 5.6 months in the placebo arm and 9.7 months in the pembrolizumab arm (hazard ratio, 0.65; P = .0012).
The recommended pembrolizumab dose in TNBC is 200 mg every 3 weeks or 400 mg every 6 weeks administered prior to chemotherapy until disease progression, unacceptable toxicity, or up to 24 months.
Pembrolizumab can cause immune-mediated adverse reactions that may be severe or fatal, according to Merck , the manufacturer of pembrolizumab. These adverse reactions include pneumonitis, colitis, hepatitis, endocrinopathies, nephritis, severe skin reactions, solid organ transplant rejection, and complications of allogeneic hematopoietic stem cell transplant.
“Based on the severity of the adverse reaction, [pembrolizumab] should be withheld or discontinued and corticosteroids administered if appropriate,” the company noted.
For more details on pembrolizumab, see the full prescribing information .