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Supplemental Figure S1. Levels of serum cytokines in patients over the course of treatment. Serum levels of the cytokines IFN-γ (A), IP-10 (B), TNF-α (C) MIP-1α (D), MIP-1β (E), RANTES (F), GM CSF (G), and IL-8 (H) were measured at baseline and during cycle 8 using a custom V-Plex assay. Assay was performed in triplicate and the average was plotted for each individual patient. *, p=0.0008 for IFN-γ, p=0.0011 for IP-10, p=0.0102 for TNF-α Supplemental Figure S2. Levels of serum cytokines in patients stratified by length of progression-free survival. Serum levels of the cytokines MIP-1α (A), MIP-1β (B), RANTES (C), GM-CSF (D), and IL-8 (E) were measured at baseline and during cycle 8 using a custom V-Plex assay. The assay was performed in triplicate and the average was plotted for each individual patient stratified by progression-free survival greater than or less than 100 days Supplemental Figure S3. Gating strategy for defining monocytic and granulocytic MDSC. Examples of monocytic-dominant (A) and granulocytic-dominant (B) total MDSC. PBMCs procured from pre-therapy blood draws were stained with anti-CD33-APC, anti-HLA-DR-PECy7, anti-CD11b-PE, anti-CD14-V-450, and anti CD15-FITC antibodies; CD33+/HLA-DR- populations were further characterized by CD15, CD14, and CD11b expression. Percentages gleaned from CD15+CD11b+ and CD14+CD11b+ quadrants were back multiplied by total MDSC (CD33+HLA-DR-) to obtain values presented in Table S3.

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Purpose:mAbs including cetuximab can induce antibody-dependent cellular cytotoxicity (ADCC) and cytokine production mediated via innate immune cells with the ability to recognize mAb-coated tumors. Preclinical modeling has shown that costimulation of natural killer (NK) cells via the Fc receptor and the IL12 receptor promotes NK-cell–mediated ADCC and production of cytokines.Patients and Methods:This phase I/II trial evaluated the combination of cetuximab with IL12 for the treatment of EGFR-expressing head and neck cancer. Treatment consisted of cetuximab 500 mg/m2 i.v. every 2 weeks with either 0.2 mcg/kg or 0.3 mcg/kg IL12 s.c. on days 2 and 5 of the 2-week cycle, beginning with cycle 2. Correlative studies from blood draws obtained prior to treatment and during therapy included measurement of ADCC, serum cytokine, and chemokine analysis, determination of NK cell FcγRIIIa polymorphisms, and an analysis of myeloid-derived suppressor cell (MDSC) frequency in peripheral blood.Results:The combination of cetuximab and IL12 was well tolerated. No clinical responses were observed, however, 48% of patients exhibited prolonged progression-free survival (PFS; average of 6.5 months). Compared with patients that did not exhibit clinical benefit, patients with PFS >100 days exhibited increased ADCC as therapy continued compared with baseline, greater production of IFNγ, IP-10, and TNFα at the beginning of cycle 8 compared with baseline values and had a predominance of monocytic MDSCs versus granulocytic MDSCs prior to therapy.Conclusions:Further investigation of IL12 as an immunomodulatory agent in combination with cetuximab in head and neck squamous cell carcinoma is warranted.

Supplementary Table 1. Toxicities; Supplementary Table 2. Patient characteristics and response evaluation; Supplementary Table 3. Patient Correlative Study Results