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OA20 - Immunotherapy and Markers (ID 401)
- Event: WCLC 2016
- Type: Oral Session
- Track: Biology/Pathology
- Presentations: 1
OA20.02 - Neoantigen Targeting in NSCLC Patients with Complete Response to Anti-PD-1 Immunotherapy (ID 4352)
11:00 - 12:30 | Author(s): K.N. Smith
Anti-PD-1 immunotherapy has resulted in durable clinical responses in heavily pretreated patients with non-small cell lung cancer (NSCLC). While NSCLC is typically seen as non-immunogenic, there is a 15-20% objective response rate and a median duration of response of 17 months in patients treated with the PD-1 inhibitor, nivolumab. This duration of response has not been reported with other systemic therapies in advanced NSCLC. While tumor PD-L1 expression may be a biomarker of sensitivity to anti-PD-1 therapy, and the number of somatic mutations may play a role in PD-1 upregulation on T cells, the mechanisms underlying response vs. progressive disease have yet to be fully elucidated.
Whole exome sequencing and mutation-associated neoantigen (MANA) prediction was performed on tumor sections from two advanced NSCLC patients with complete response to nivolumab. Peptides representing MANAs were synthesized and tested against PBMC in a 10-day cultured IFNg ELISpot assay. Reactive MANAs were assessed in binding and stability assays. TCR sequencing was performed on reactive cell cultures and on DNA obtained from tumor resections to match MANA-reactive TCR clones with clones that were infiltrating the tumor.
The mean mutational burden in NSCLC as reported previously is 360 sequence alterations. In our study, patient 1 had 30 sequence alterations and patient 2 had 314. Despite the difference in mutational load, MANA reactivity was detected in peripheral blood of both patients >1 year after being declared cancer-free. TCR clones of MANA-reactive peripheral T cells were detected in tumor resections and were expanded in MANA-stimulated T cell cultures. Binding and stability assays confirmed that these MANAs bind to their cognate HLA with high affinity and stability.
These findings show that NSCLC tumors with differential mutational burden can show regression following checkpoint blockade and suggest that the quality of mutations may be more influential in immunogenicity than the overall quantity of mutations. Our data also show that MANA reactivity may be the underlying mechanism by which T cells eliminate tumor following anti-PD-1 immunotherapy. Additional studies should evaluate mechanisms of enhancing MANA reactivity in patients who do not respond to checkpoint blockade and should further validate the link between MANA reactivity and clinical response to anti-PD-1.
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