Zalutumumab

Antibodies against the Epidermal Growth Factor receptor is suggested to decrease tumour failure and increase survival rates of patients (pts) with Head and Neck Squamous Cell Carcinomas (HNSCC) when combined with radiotherapy. This study aimed to evaluate if concurrent treatment with the EGFR inhibitor zalutumumab during (chemo-)radiotherapy improved outcome in pts with HNSCC.

Overall, 608 eligible pts with biopsy-verified HNSCC of the oral cavity, pharynx and larynx were accrued November 2007 to June 2012. Pts were randomized to a control-arm of primary accelerated radiotherapy predominantly 66-68 Gy, 2 Gy/fraction, 6fx/week and concomitant daily hypoxic radiosensitisation with nimorazole. St. III-IV carcinomas received weekly cisplatin 40 mg/m² in addition to nimorazole. The zalutumumab-arm was identical to the control-arm plus zalutumumab 8 mg/kg. First dose was given the week before start of treatment and continued weekly during radiotherapy. Analyses were performed as intention-to-treat. Primary endpoint was loco-regional failure. Secondary endpoints were disease-specific survival and overall survival.

In total, 307 pts were in the control-arm and 301 in the zalutumumab-arm. Median follow-up was 59 months. Patient and tumour parameters were well balanced. The 5-year loco-regional failure rate was 24 % in the zalutumumab-arm and 18 % in the control-arm; Hazard Ratio (HR) 1.16 (95 % CI 0.84-1.59); disease-specific survival; HR 1.04 (95 % CI 0.73-1.50) and overall survival; HR 1.21, (0.91-1.61). Effect of zalutumumab was not influenced by HPV/p16 status.

Addition of concomitant zalutumumab to primary (chemo-)radiotherapy and concomitant nimorazole for HNSCC did not increase loco-regional control nor disease-specific or overall survival.

EGFR plays an essential role in cellular signaling pathways that regulate cell growth, proliferation, and survival and is often dysregulated in cancer. Several monoclonal IgG antibodies have been clinically tested over the years, which exert their function via blocking the ligand binding domain (thereby inhibiting downstream signaling) and inducing Fc-related effector functions, such as antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). However, these IgG antibodies do not optimally recruit neutrophils, which are the most abundant white blood cell population in humans. Therefore, we reformatted six therapeutic EGFR antibodies (cetuximab, panitumumab, nimotuzumab, necitumumab, zalutumumab, and matuzumab) into the IgA3.0 format, which is an IgA2 isotype adapted for clinical application. Reformatting these antibodies preserved Fab-mediated functions such as EGFR binding, growth inhibition, and ligand blockade. In addition, whole leukocyte ADCC was significantly increased when using this panel of IgA3.0 antibodies compared with their respective IgG counterparts, with no major differences between IgA3.0 antibodies. In vivo, IgA3.0 matuzumab outperformed the other antibodies, resulting in the strongest suppression of tumor outgrowth in a long intraperitoneal model. We showed that neutrophils are important for the suppression of tumor outgrowth. IgA3.0 matuzumab exhibited reduced receptor internalization compared with the other antibodies, possibly accounting for its superior in vivo Fc-mediated tumor cell killing efficacy. In conclusion, reformatting EGFR antibodies into an IgA3.0 format increased Fc-mediated killing while retaining Fab-mediated functions and could therefore be a good alternative for the currently available antibody therapies.