“We observed a very encouraging response rate. Responses were seen across PD-L1 status,” said Wade Iams, MD, at a press conference held in advance of the annual meeting of the Society for Immunotherapy of Cancer. Dr. Iams is a professor of medicine at Vanderbilt University Medical Center, Nashville, Tenn.
“The study was not loaded to PD-L1–high patients. We had a good breakdown across all of our three typical groups in the [NSCLC] treatment setting. Across histology types between squamous and nonsquamous, the median duration of response was almost 22 months. This is very encouraging compared to historical controls,” he said.
Eftilagimod alpha is a soluble form of the LAG-3 protein, which is a stimulator of antigen-presenting cells and CD8+ T cells through its action on MHC class 2 molecules. It suppresses the activation of T cells and therefore has the potential to boost the effect of anti–PD-1 therapy. LAG-3 can have both stimulatory and inhibitor immune effects, leading Immutep, which sponsored the study with Merck Sharp and Dohme, to pursue it in both cancer immunotherapy and autoimmune diseases.
The drug is a departure from other drugs which are LAG-3 antagonists. Those therapies interfere with the interaction between LAG-3 on the surface of activated T cells and MHC class 2 molecules on the surface of resting dendritic cells, which would otherwise dampen immune response in the tumor microenvironment. On the other hand, LAG-3 (or eftilagimod alpha) interacts with MHC class 2 on the surface of activated dendritic cells and monocytes to stimulate production of cytotoxic CD8+ T cells. These in turn can be unleashed further by the downstream action of pembrolizumab.
The phase 2 trial included three parts: In part A, 114 patients with NSCLC received the combination of eftilagimod alpha and pembrolizumab being given as a first-line therapy. Part B looked at the combination in 36 patents who were resistant to PD-1/PD-L1 therapies. Part C included 39 patients with head and neck squamous cell carcinoma who had previously received platinum-based chemotherapy. Patients received combination therapy for up to 1 year, then monotherapy with pembrolizumab for up to another year.
The primary endpoint of the study was a comparison of overall response rate to historical controls, with success set at 35% or higher. In the intent-to-treat analysis of the treatment-naive NSCLC population, ORR was 39.5% (95% confidence interval, 30.5%-49.1%) and the interim median progression-free survival was 6.9 months (95% CI, 4.9-9.3 months). Among 40 responders, the median duration of response was 21.6 months (95% CI, 17.3-30.0 months). ORRs were similar between squamous and nonsquamous subtypes.
In his presentation of the results, Dr. Iams said that 75% of participants had PD-L1 levels below 50%. The ORR was highest at 55% in the PD-L1 greater than 50% group, 44.7% in the PD-L1 1%-49% group, and 31.1% in the PD-L1 less than 1% group. It was a “very impressive response rate” for the low PD-L1 group, Dr. Iams said. Interim median progression-free survival followed a similar trend, with values of 11.4 months, 8.3 months, and 4.2 months, respectively.
Asked about the efficacy across subgroups, Dr. Iams responded that other immune stimulating agents have shown a stepwise improvement across PD-L1 expression levels, similar to what was observed in the current study. “My personal opinion as to why it was still effective at low PD-L1 is in part that PD-L1 is an imperfect biomarker. We know that there’s tumor heterogeneity, and perhaps it’s not fully representative of a one-site evaluation, but also in combination, and we have seen this in patients with [NSCLC] treated with both PD-L1 and CTLA-4 agents of increased efficacy in the PD-L1–low patients. So these combination immunotherapy strategies may be uniquely opportune for the low PD-L1 patients,” Dr. Iams said.
The study was funded by Immutep and Merck Sharp and Dohme. Dr. Iams has financial relationships with Merck.