Population pharmacokinetics (popPK) of Sym004 to evaluate the effect of intrinsic and extrinsic factors on exposure in metastatic colorectal cancer (mCRC).

Abstract

496 Background: Sym004 consists of two anti-EGFR monoclonal antibodies (futuximab and modotuximab) directed against non-overlapping epitopes in the EGFR domain III. Sym004 induces rapid and efficient removal of the EGFR from the cancer cell surface by triggering EGFR internalization and degradation and has shown promising efficacy in mCRC patients. Based upon a post-hoc analysis of a Phase 2 study, a Phase 3 trial in genomically selected mCRC patients is in preparation. Methods: The aim was to establish a popPK model for Sym004 in order to i) evaluate impact of covariates (intrinsic and extrinsic factors) on Sym004 exposure and ii) provide exposure metrics for a PK/PD analysis. Sym004 serum concentrations were obtained from 330 patients with mCRC (n = 247) or advanced solid tumors (studies Sym004-01, Sym004-02, Sym004-05 and Sym004-06). Sym004 (0.4-18 mg/kg) was dosed by i.v. infusion weekly or every 2nd week, or as a 9 mg/kg loading dose followed by 6 mg/kg weekly (9/6 mg/kg weekly). Non-linear mixed effects modelling was done in NONMEM v7.3.0. Covariates evaluated included body weight, age, sex, race, albumin, renal function, hepatic function, tumor type and size, ECOG and previous anti-EGFR treatments. Results: The base popPK model was a 2-compartment model with linear and non-linear Michaelis-Menten-type elimination and a priori inclusion of body weight on CL, Vmax, V1 and V2. The model captured the non-linear PK well. The final covariate model retained covariates whose point estimates were outside the range of 0.8 to 1.25 and whose 90% confidence intervals did not overlap with the null value and included only body weight and albumin. Inter-individual variability was estimated for CL, Vmax and V1 and was in the range of 18-30%. Simulations were used to assess the clinical relevance of the covariates as judged by the magnitude of the change in exposure of the Phase 3 dose regimen of 9/6 mg/kg weekly. Conclusions: The popPK model described the Sym004 PK data well. No covariates were present that changed the Sym004 exposure in a clinically significant manner which would necessitate a dose modification. The model is suitable for simulating the Sym004 PK for PK/PD analyses. Clinical trial information: NCT01117428,NCT01417936,NCT02083653,NCT01955473.