A phase I imaging and pharmacodynamic trial of CS-1008 in patients (pts) with metastatic colorectal cancer (mCRC).

Abstract

2583 Background: Death receptor 5 (DR5) is a member of the TNFR superfamily that initiates the extrinsic apoptotic pathway. CS-1008 is a humanised, monoclonal IgG1 agonistic antibody (Ab) to human DR5 created by CDR grafting of the murine Ab TRA-8. The aim of this study was to investigate the impact of CS-1008 dose on biodistribution, quantitative tumor uptake and anti-tumor response in pts with mCRC. Methods: Pts with mCRC were treated with weekly IV CS-1008 in 5 non-sequential cohorts (Co). Different loading doses were used on days 1 and 8 (0.2 to 6 mg/kg), followed by a weekly dose of 2 mg/kg. D1 and D36 doses were trace-labeled with 111In, followed by whole-body planar and regional SPECT imaging over 10 days. Primary endpoints: initial biodistribution, pharmacokinetic (PK) and tumor uptake following single infusion; changes in biodistribution, PK and tumor uptake following sequential doses. Secondary endpoints: tumor response; changes in tumor metabolism by FDG-PET; serum apoptosis biomarkers and tumor response markers. Results: 19 pts (median age 64 yrs; M:F 11:8; 2-6 prior chemotherapy regimens) were enrolled as follows: Co 1, n=2; Co 2, n=4; Co 3, n=5; Co 4, n=3; and Co 5, n=5. Tumor uptake was variable: 7 pts had no uptake, 11 pts had uptake in all sites of disease but liver, 1 pt showed liver uptake. Tumor uptake and PK were not affected by dose or repeated drug administration. No anti-CS-1008 Ab responses were detected. DR5 expression in archived samples did not correlate with uptake or response. 111In‐CS‐1008 biodistribution showed gradual blood pool clearance and no abnormal uptake in normal tissue. Mean % change in SUVmax from baseline in lesions with uptake was higher than in those with no uptake. There were 8 SD, 1 PR and 10 PD. Duration of PR was 3.7 months (mo). Mean duration of SD was 4 mo. Disease control rate (SD + PR) in pts with uptake was 58% vs 28% of pts with no uptake. Lesions with no uptake were more likely to progress, with a PD risk of 3.4 times higher than those lesions with uptake. Conclusions: Tumor DR5 expression, assessed by 111In-CS-1008 imaging, revealed real-time heterogeneous DR5 expression and appeared to be a promising predictive imaging biomarker of clinical benefit in pts with mCRC receiving CS-1008. Clinical trial information: NCT01220999.