While PD-L1 expression levels are not considered to be a reliable biomarker for response to immunotherapeutic agents, response to durvalumab in the phase II ATLANTIC trial did increase with higher PD-L1 expression.
The objective response rate (ORR) with durvalumab increased in line with PD-LI expression: In PD-L1 low or negative patients with PD-L1 expression on less than 25% of tumor cells, the ORR was 7.5% (95% CI, 3.114.5), and ORR was 16.4% (95% CI, 10.8–23.5) in patients with PD-L1 expression ≥25%. But the highest ORR of 30.9% (95% CI, 20.2–43.3) was observed in patients with tumoral PD-L1 expression on ≥90% of tumor cells.
One-year overall survival (OS) rates were 48% in patients with PD-L1 ≥25% and 51% in patients with PD-L1 ≥90%.
This response appeared to be durable, with a median duration of response (DoR) that was not reached (NR): ORR in the respective groups was 12.3 months (95%CI, 7.5NR), NR (95%CI, 7.2–NR), and NR, where 18 of 21 responders remained progression-free at data cut-off.
“Results from this trial with durvalumab in a heavily pre-treated population, many of whom have had 3 or more prior treatment regimens, are encouraging and consistent with efficacy observed with other immunotherapy medicines in metastatic, relapsed NSCLC,” commented Marina Garassino MD, of the Fondazione IRCCS Istituto Nazionale dei Tumori in Milan.
Garassino presented data from 2 of the 3 cohorts of patients participating in the single-arm, phase II, global ATLANTIC trial of durvalumab: Patients in cohort 2 were divided into PD-L1 low expressers, with <25% PD-L1 expression on tumor cells, and PD-L1 high expressers with ≥25% tumoral PD-L1 expression, and patients in cohort 3 were PD-L1 high expressers with ≥90% on tumour cells. Cohort 2 had 265 patients and Cohort 3 contained 68 patients who were treated with durvalumab at 10 mg/kg intravenous every 2 weeks.
The ATLANTIC study initially enrolled all-comers and then restricted enrollment to patients with PD-L1 high tumors determined by membrane staining. The trial was conducted in patients with locally advanced or metastatic stage IIIBIV NSCLC and EGFR/ALK wild-type tumors. All patients were heavily pretreated. Sixty percent of patients in cohort 2 and 40% of patients in cohort 3 received 3 or more lines of treatment prior to durvalumab.
The primary endpoint was ORR by RECIST v1.1, and secondary endpoints included disease control rate (DCR), DoR, progression-free survival (PFS), OS, and safety.
Responses were consistent and similar in patients with squamous and non-squamous histology, according to Garassino.
In cohort 2, patients with low and high expression demonstrated DCR of 20.4% and 28.8%, respectively, and patients in cohort 3 with the highest expression showed DCR of 38.2%.
The median PFS was 1.9 months, 3.3 months, and 2.4 months in cohort 2 low- and high-expressing patients, and in cohort 3, respectively. OS in the respective groups was 9.3 months, 20.9 months, and NR.
Durvalumab showed a manageable safety and tolerability profile; most adverse events (AEs) were low grade and resolved with treatment delay and/or immunosuppressive interventions. Grade ≥3 treatment-related AEs occurred in 8.3% and 17.6% of cohort 2 and cohort 3 patients, respectively.
“There were few discontinuations due to treatment-related adverse events,” she commented. Treatment-related AEs leading to discontinuation occurred in 2.7% of patients.