The U.S. Food and Drug Administration granted accelerated approval to pembrolizumab in combination with pemetrexed and carboplatin for the treatment of patients with previously untreated metastatic non-squamous non-small cell lung cancer (NSCLC).

Approval was based on a cohort (G1) of patients enrolled in an open-label, multicenter, multi-cohort study (KEYNOTE-021).

A total of 123 patients with locally advanced or metastatic non-squamous NSCLC and no prior systemic treatment for metastatic disease were enrolled.

Patients were randomised to receive either pembrolizumab, 200 mg every 3 weeks, in combination with pemetrexed and carboplatin (PC) for 4 cycles followed by pembrolizumab for a maximum of 24 months (n=60) compared to PC alone (n=63).

At the investigator’s discretion, patients in both arms may have received pemetrexed as maintenance therapy.

Randomisation was stratified by PD-L1 tumour expression (tumour proportion score [TPS] <1% vs. TPS ≥1%).

The trial demonstrated an improvement in overall response rate (ORR) and in progression-free survival (PFS) for patients randomised to pembrolizumab plus PC.

The ORR was 55% (95% CI: 42-68%) for the pembrolizumab plus PC arm and 29% (95% CI: 18-41%) for the PC alone arm (p=0.0032).

Among responders, the proportion of patients with response durations of 6 months or longer was 93% in the pembrolizumab-containing arm and 81% in the PC alone arm.

The hazard ratio for PFS was 0.53 (95% CI: 0.31, 0.91, p=0.0205) and the median PFS was 13.0 months (95% CI: 8.3, NE) for the pembrolizumab plus PC arm and 8.9 months (95% CI: 4.4, 10.3) for the PC alone arm.

Exploratory analyses of ORR were conducted in subgroups defined by PD-L1 tumour expression (TPS <1% and TPS ≥1%).

In the TPS <1% subgroup, the ORR was 57% and 13% in the pembrolizumab plus PC and in the PC alone arms, respectively.

In the TPS ≥1% subgroup, the ORR was 54% and 38% in the pembrolizumab plus PC and in the PC alone arms, respectively.

Adverse events (AEs) and serious AEs (SAE) were observed at a higher incidence with the addition of pembrolizumab to PC compared to PC alone in patients from Cohort G1.

Serious AEs occurred in 41% of the patients in the pembrolizumab plus PC arm compared with 28% in the PC alone arm.

The most common AEs (all grades) in the pembrolizumab PC arm were fatigue (71%), nausea (68%), and constipation (51%).

The most common grade 3-4 adverse reactions were fatigue (3.4%), dyspnea (3.4%), nausea (1.7%), vomiting (1.7%), diarrhea (1.7%), and rash (1.7%).

Pembrolizumab was discontinued for adverse reactions in 10% of patients.

The most common adverse reaction resulting in discontinuation of pembrolizumab (≥ 2%) was acute kidney injury (3.4%).

Immune-mediated adverse reactions can occur with pembrolizumab including pneumonitis, colitis, hepatitis, endocrinopathies, and nephritis.

Based on the severity of the adverse reaction, pembrolizumab should be withheld or discontinued and corticosteroids administered when appropriate.

The recommended pembrolizumab dose and schedule for NSCLC is 200 mg as an intravenous infusion every 3 weeks until disease progression, unacceptable toxicity, or up to 24 months in patients without disease progression.

Full prescribing information for pembrolizumab is available here.