Safety, pharmacokinetics and efficacy of SCT200, an anti-EGFR monoclonal antibody in patients with wild-type KRAS/NRAS/BRAF metastatic colorectal cancer: a phase I dose-escalation and dose-expansion study

Background: An over-expression of the epidermal growth factor receptor (EGFR) has been observed in colorectal cancer and is associated with aggressive disease and poor prognosis. SCT200 is a newly developed recombinant, fully humanized, anti-EGFR monoclonal antibody. This study aimed to evaluate its safety, tolerability, pharmacokinetics (PK), and efficacy in patients with wild-type KRAS/NRAS/BRAF metastatic colorectal cancer (mCRC). METHODS: This phase I study comprising dose-escalation phase and dose-expansion phase. SCT200 was administrated intravenously to groups of three to six patients. An every 3-week dosing cycle (0.5-15.0 mg/kg) and multiple dosing schedule were evaluated. Blood samples were collected at preset intervals for PK assessment, radiological imaging was used for efficacy assessment, and continuous safety monitoring was performed in each group during the study. RESULTS: From December 16, 2014 to December 31, 2018, fifty-six patients with wild-type KRAS/NRAS/BRAF mCRC receiving ≥ 1 dose of SCT200 were evaluated. Among them, 44.6% (25/56) of the patients failed at least two prior lines of chemotherapy. No dose-limiting toxicities occurred in any group. All of the patients experienced treatment-emergent adverse events (TEAEs). 96.4% (54/56) of patients experienced treatment-related adverse events (TRAEs), and 26.8% (15/56) of patients with Grade ≥ 3 TRAEs. No serious TRAEs were observed. The most common TRAEs were dermotoxicity and hypomagnesemia. PK analysis showed non-linear PK in the range of 0.5 - 8.0 mg/kg of single dose SCT200, the clearance decreased, and the elimination half-life (T_1/2) prolonged following dose increase. In the multiple-dose period, the clearance decreased, peak concentration increased, and T_1/2 prolonged during prolonged drug administration, and a steady state was reached after five consecutive dose of 6.0 mg/kg quaque week (QW). The objective response rate (ORR) was 30.4% (17/56, 95% confidence interval [CI], 18.8%-44.1%). The ORR in the dose-expansion group (6.0 mg/kg QW) was 48.0% (12/25, 95% CI, 27.8%-68.7%), the median progression-free survival was 5.2 months (95%CI, 3.6-5.5), and the median overall survival was 20.2 months (95%CI, 12.1-not reached).

Conclusions: SCT200 showed favorable safety, PK profile, and preliminary efficacy for patients with wild-type KRAS/NRAS/BRAF mCRC.

Trial registration: This study was registered with ClinicalTrials.gov ( NCT02211443 ).