Background Immunosuppressive myeloid cells in the tumor microenvironment (TME) limit the efficacy of immune checkpoint inhibitors (ICIs) in head and neck squamous cell carcinoma (HNSCC). Preclinical and clinical studies demonstrated that antibody blockade of semaphorin 4D (SEMA4D) reverses immunosuppression, including attenuation of MDSC recruitment and function1 and promotes organization of lymphoid aggregates within tumors,2 leading to enhanced efficacy of ICIs. Pepinemab, a SEMA4D blocking antibody, in combination with avelumab was well tolerated and provided clinical benefit in patients with ICI-resistant, PD-L1-low NSCLC.3 The primary hypothesis of this proof-of-concept study is that pepinemab in combination with pembrolizumab will improve the efficacy of immunotherapy in R/M HNSCC.
Methods KEYNOTE-B84 (NCT04815720) is an ongoing single-arm open-label study evaluating the safety, efficacy, and PK/PD of pepinemab in combination with pembrolizumab as first-line treatment of R/M HNSCC. The study includes immunotherapy naïve patients who have tumor PD-L1 combined positive scores (CPS) of <20 and ≥20 with an interim analysis when 36 patients complete the first tumor response assessment. The primary efficacy endpoint is ORR, and secondary endpoints include PFS, DoR, and OS, as well as exploratory biomarker analyses. Pre- and on-treatment biopsies are collected for evaluation of immune contexture in TME. Data presented here include pre-specified interim analysis of safety, efficacy, and biomarker assessments.
Results The combination appears to be well tolerated with no DLTs observed or safety signals identified by the SMC. Notably, in the PD-L1 low population (CPS<20, N=19), we observed approximately a doubling in ORR, DCR, and PFS for the combination of pepinemab and pembrolizumab, as compared to reported single agent pembrolizumab.4 Among the CPS<20 population, ORR was 21.1% (2 CR and 2 PR), DCR was 73.7%, and median PFS was 5.79 months. In contrast, in the CPS≥20 subgroup, the ORR was 17.6% (n=17), similar to ICI monotherapy for this population. Spatial multiplex IHC analysis of pre- and post-treatment tumor biopsies demonstrated an increase in activated APC, reduced recruitment of MDSC, and highly organized immune aggregates (figure 1) that corresponded with disease control.
Conclusions The pre-specified interim analysis of the ongoing KN-B84 study showed that pepinemab in combination with pembrolizumab was well-tolerated, suggested early signs of improved anti-tumor response over single agent pembrolizumab in the difficult to treat PD-L1 low group, and provided evidence of treatment-induced biomarker changes in the TME of responder tumors, including formation of high-density lymphoid aggregates.
Clavijo PE, Friedman J, Robbins Y, Moore EC, Smith E, Zauderer M, Evans EE, Allen CT. Semaphorin4D Inhibition Improves Response to Immune-Checkpoint Blockade via Attenuation of MDSC Recruitment and Function. Cancer Immunol Res. 2019 Feb;7(2):282–291. doi: 10.1158/2326–6066.CIR-18–0156.
Olson B, Mallow C, Reilly C, et al. Neoadjuvant SEMA4D blockade with nivolumab alters suppressive myeloid cells while elevating B cell and CD26hi T cell infiltration in the tumors of patients with resectable stage III melanoma. Journal for ImmunoTherapy of Cancer 2022;10:doi: 10.1136/jitc-2022-SITC2022.0613
Shafique MR, Fisher TL, Evans EE, et al. A Phase Ib/2 Study of Pepinemab in Combination with Avelumab in Advanced Non-Small Cell Lung Cancer. Clin Cancer Res 2021, doi: 10.1158/1078–0432.CCR-20–4792
Burtness B, Rischin D, Greil R, Soulières D, Tahara M, et al. Pembrolizumab Alone or With Chemotherapy for Recurrent/Metastatic Head and Neck Squamous Cell Carcinoma in KEYNOTE-048: Subgroup Analysis by Programmed Death Ligand-1 Combined Positive Score. J Clin Oncol. 2022 Jul 20;40(21):2321–2332. doi: 10.1200/JCO.21.02198.
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