Abstract CT224: Pilot study in patients with advanced solid tumors to evaluate feasibility of ferumoxytol (FMX) as tumor imaging agent prior to MM-398, a nanoliposomal irinotecan (nal-IRI)

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Introduction MM-398, a stable nanoliposomal irinotecan (nal-IRI), is designed to exploit leaky tumor vasculature for enhanced drug delivery to tumors. Tumor deposition of nal-IRI and subsequent irinotecan conversion by CES enzymes in both neoplastic cells and tumor associated macrophages (TAM) may positively correlate with activity. Predictive biomarkers to measure tumor deposition could identify patients likely to benefit from nal-IRI. FMX is a 30nm iron-oxide, superparamagnetic nanoparticle with MRI contrast properties. The particle size, its propensity for uptake by TAMs and similar distribution patterns to nal-IRI in preclinical models led to a clinical study evaluating the feasibility of correlating FMX-based MRI (Fe-MRI) acquisition with tissue drug metabolite levels and other biomarkers to estimate drug delivery to tumor. Patients and methods Eligible patients (n=12) with refractory solid tumors with at least two metastatic lesions >2cm accessible for a percutaneous biopsy were enrolled from one institution. Fe-MRI scans were performed on a 1.5T MRI using T2* iron sensitive sequences prior to and following FMX infusion (0.5h, 24h, 72h). MR images were used to direct biopsies at 72h to FMX high or low regions, permitting intra- and inter-patient comparisons of FMX and nal-IRI tumor levels. Patients continued on nal-IRI at 80mg/m2 q2w until progression. Tissue iron and TAM distribution were assessed by IHC, tissue-bound metabolite levels by mass-spectrometry. T2* signal was used to calculate FMX levels in total lesions along with FMX estimates on biopsy images derived from fused MRI-CT biopsy images. The first 9 patients (2M 7F; median age 57 years, range 28-71 years) are reported. Results There were no safety-related or other potential interactions with nal-IRI and FMX. Adverse events of nal-IRI were consistent with previous studies. FMX levels, quantified in 36 tumor lesions from the first 9 subjects, showed mean FMX accumulation of 37.9 mcg/mL [3.3-101.2 mcg/mL] and 13.2 mcg/mL [0.1-41.0 mcg/mL] at 24h and 72h, respectively. Lesions were localized mostly in liver (67%) and lymph nodes/peritoneal sites (25%). A mechanistic PK model indicated that tissue permeability to FMX contributed to Fe-MRI signals at 24h, while FMX binding contributed at 72h. Levels of irinotecan and SN-38 were 3.59mcg/g [2.29-4.89mcg/g] and 11.43ng/g [4.04-18.8ng/g], respectively, at 72h in biopsies from the first 6 patients. Conclusions This study is one of the first to measure active metabolite SN-38 levels in patient tumors. FMX can be used as a tumor contrast agent prior to nal-IRI treatment. T2* MRI sequences allowed for quantitation of FMX concentrations in tumor and reference tissue. A mechanistic model provided an estimation of FMX tumor tissue permeability and binding that may be useful as a predictive biomarker of nanotherapeutics such as nal-IRI. Citation Format: Ramesh K. Ramanathan, Ronald L. Korn, Jasgit C. Sachdev, Gerald J. Fetterly, Katie Marceau, Vickie Marsh, John M. Neil, Ronald G. Newbold, Natarajan Raghunand, Joshua Prey, Stephan G. Klinz, Eliel Bayever, Jonathan B. Fitzgerald. Pilot study in patients with advanced solid tumors to evaluate feasibility of ferumoxytol (FMX) as tumor imaging agent prior to MM-398, a nanoliposomal irinotecan (nal-IRI). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT224. doi:10.1158/1538-7445.AM2014-CT224