Abstract CT054: A dose escalation and toxicity study using pre-determined target concentration of Ramucirumab, a novel anti-angiogenic agent in children with recurrent / refractory solid tumors: A report from the children's oncology group phase I/ pilot consortium (ADVL1416)

Abstract

Abstract Ramucirumab (RAM) is a high affinity, humanized, monoclonal antibody that binds to the extra-cellular domain of the vascular endothelial growth factor receptor (VEGFR). RAM prevents the binding of VEGF ligands with VEGFR-2, the most potent receptor of the VEGF tumor angiogenesis pathway. RAM is FDA approved for adults with NSCLC, as well as for gastric and colorectal adenocarcinoma where higher exposure was associated with better outcomes. Based on population pharmacokinetic (PK) analysis of the adult data, a minimum steady state concentration (Cmin ss) of ≥ 50 µg/ml of RAM was considered the target concentration for pediatrics. The Children's Oncology Group (COG) conducted a phase 1 study using a rolling six design to define the maximum tolerated dose (MTD) and /or a recommended phase 2 dose (RP2D), evaluate toxicities and explore circulating angiogenic cells as a biomarker for RAM monotherapy in children with recurrent/refractory solid tumors. The starting dose of 8 mg/kg IV q2 weeks (DL1) was chosen based on the adult safety profile and effective Cmin ss. Since adult data suggested that lower body weight was associated with lower Cmin ss, dose escalation to 12 mg/kg IV q2 weeks (DL2) was planned provided the MTD was not exceeded in DL1 and up to 16 mg/kg IV q2 weeks (DL3) if Cmin ss was < 50 µg/ml in 1 of 6 subjects on DL2 without exceeding the MTD. An expansion cohort was planned at the lowest dose where at least 5 of 6 subjects exceeded the target in order to generate PK data in at least 6 additional subjects < 12 years of age. In the absence of an MTD, the RP2D was defined as the dose achieving Cmin ss ≥ 50 µg/ml on day 42 ± 2, after 3 doses of RAM administered IV every 2 weeks, in at least 10 of 12 subjects. Sixteen subjects (15 eligible; 7 females), median age of 14 years (3-21 yrs.) have been enrolled. Of the 7 subjects on DL1, two had insufficient PK sampling to establish Cmin ss, including 1 who experienced grade 2 proteinuria (DLT). In the remaining 5, the median (range) Cmin ss was 66 (40-136) µg/ml; 2/5 did not achieve the target of ≥ 50 µg/ml. Of the 8 subjects on DL2, two had insufficient PK sampling, including 1 with grade 2 proteinuria (DLT). In the remaining 6, the median (range) Cmin ss was 64 (51-101) µg/ml, all ≥ 50 µg/ml; thus 12mg/kg IV q2 weeks was identified for the expansion cohort. The most common RAM related non-DLT toxicities were grade 1/2 headache in 6 subjects, grade 1/2 elevation in aspartate aminotransferase in 7 subjects and grade 2/3 hypertension in 2 subjects. Due to low participation, circulating angiogenic cells could not be analyzed. This is the first COG study in which dose escalation and RP2D for a targeted agent incorporated a primary PK endpoint (Cmin ss) based upon efficacy data from adult studies and paves the way for similar study design for future phase-1 studies. Citation Format: Kamnesh Pradhan, Stacey L. Berg, Xiaowei Liu, Charles G. Minard, James Croop, Joel M. Reid, Elizabeth Fox, Brenda J. Weigel. A dose escalation and toxicity study using pre-determined target concentration of Ramucirumab, a novel anti-angiogenic agent in children with recurrent / refractory solid tumors: A report from the children's oncology group phase I/ pilot consortium (ADVL1416) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT054.