FDA Approves Pembrolizumab Plus Chemo for TNBC

The FDA granted an accelerated approval to pembrolizumab (Keytruda) plus chemotherapy for the treatment of patients with locally recurrent, unresectable or metastatic triple-negative breast cancer (TNBC) with PD-L1 expression is CPS ≥10, according to the agency.

The approval was based off findings from the multicenter, double-blind KEYNOTE-355 trial. In the trial, eligible patients were randomized 2:1 to receive either 200 mg on day 1 every 3 weeks of pembrolizumab plus chemotherapy or a placebo plus chemotherapy (paclitaxel protein-bound or paclitaxel, or gemcitabine plus carboplatin).

The primary outcome was progression-free survival (PFS) according to RECIST 1.1 criteria. In the group with CPS ≥10, average PFS was 9.7 months in the pembrolizumab arm, compared with 5.6 months in the placebo arm.

Recommended dosing is 200 mg every 3 weeks or 400 mg every 6 weeks, given prior to chemotherapy treatment. This should be administered until disease progression, unacceptable toxicity, or for 24 months.

Paclitaxel protein bound, when administered with pembrolizumab, should be 100 mg/m2 on days 1, 8 and 15 every 28 days, or paclitaxel 90 mg/m2 on days 1, 8 and 15 every 28 days, or gemcitabine 1000 mg/m2 plus carboplatin AUC 2 mg/mL/min on Days 1 and 8 every 21 days is administered via intravenous infusion.

Common adverse events, which occurred in 20% or more of patients receiving pembrolizumab, were fatigue, nausea, diarrhea, constipation, vomiting, alopecia, rash, cough, decreased appetite, headache. The most common laboratory abnormalities were anemia, leukopenia, neutropenia, lymphopenia, thrombocytopenia, elevated ALT and AST, hyperglycemia, hypoalbuminemia, increased alkaline phosphate, hypocalcemia, hyponatremia, hypophosphatemia, and hypokalemia.

The FDA also approved a companion diagnostic, PD-L1 IHC 22C3 pharmDx to determine which patients should receive pembrolizumab treatment.