Phase 2 Study of Lutetium 177-Labeled Anti-Carbonic Anhydrase IX Monoclonal Antibody Girentuximab in Patients with Advanced Renal Cell Carcinoma.

Unlabelled Despite advances in the treatment of metastatic clear cell renal cell carcinoma (ccRCC), there is still an unmet need in the treatment of this disease. A phase 2 radioimmunotherapy (RIT) trial with lutetium 177 ((177)Lu)-girentuximab was initiated to evaluate the efficacy of this approach. In this nonrandomized single-arm trial, patients with progressive metastatic ccRCC who met the inclusion criteria received 2405 MBq/m(2) of (177)Lu-girentuximab intravenously. In the absence of persistent toxicity and progressive disease, patients were eligible for retreatment after 3 mo with 75% of the previous activity dose. A total of 14 patients were included. After the first therapeutic infusion, eight patients (57%) had stable disease (SD) and one (7%) had a partial regression. The treatment was generally well tolerated but resulted in grade 3-4 myelotoxicity in most patients. After the second cycle, continued SD was observed in five of six patients, but none were eligible for retreatment due to prolonged thrombocytopenia. In conclusion, RIT with (177)Lu-girentuximab resulted in disease stabilization in 9 of 14 patients with progressive metastatic ccRCC, but myelotoxicity prevented retreatment in some patients.Patient summary We investigated the efficacy of lutetium 177-girentuximab radioimmunotherapy in patients with metastatic kidney cancer. The treatment resulted in disease stabilization in 9 of 14 patients. The main toxicity was prolonged low blood cell counts.Trial registration ClinicalTrials.gov identifier: NCT02002312 (https://clinicaltrials.gov/ct2/show/NCT02002312)

Pairwise comparison of 89Zr- and 124I-labeled cG250 based on positron emission tomography imaging and nonlinear immunokinetic modeling: in vivo carbonic anhydrase IX receptor binding and internalization in mouse xenografts of clear-cell renal cell carcinoma

PURPOSE: The positron-emitting tomography (PET) tracer, (124)I-cG250, directed against carbonic anhydrase IX (CAIX) shows promise for pre-surgical diagnosis of clear renal cell carcinoma (cRCC) [1, 2]. The radiometal zirconium-89 ((89)Zr), however, may offer advantages as a surrogate PET nuclide over (124)I in terms of greater tumor uptake and retention [3]. In the current report, we have developed a non-linear immunokinetic model to facilitate a quantitative comparison of absolute uptake and antibody turnover between (124)I-cG250 and (89)Zr- cG250 using a human cRCC xenograft tumor model in mice. We believe that his unique model better relates quantitative imaging data to the salient biologic features of tumor antibody-antigen binding and turnover. METHODS: We conducted experiments with (89)Zr-cG250 and (124)I-cG250 using a human ccRCC cell line (SK-RC-38) to characterize the binding affinity and internalization kinetics of the two tracers in vitro. Serial-PET imaging was performed in mice bearing sub-cutaneous cRCC tumors to simultaneously detect and quantify time-dependent tumor uptake in vivo. Using the known specific activities of the two tracers, the equilibrium rates of antibody internalization and turnover in the tumor were derived from the PET images using non-linear compartmental modeling. RESULTS: The two tracers demonstrate virtually identical tumor-cell binding and internalization but with markedly different retentions in vitro. Superior PET images were obtained using (89)Zr-cG250, owing to the more prolonged trapping of the radiolabel in the tumor and simultaneous wash-out from normal tissues. Estimates of cG250-CAIX complex turnover were 1.35–5.51 × 10(12) molecules per hour per gram of tumor (20% of receptors internalized per hour), and the ratio of (124)I/(89)Zr atoms released per unit time by tumor was 17.5. CONCLUSIONS: Pairwise evaluation of (89)Zr-cG250 and (124)I-cG250 provided the basis for a non-linear immunokinetic model which yielded quantitative information about the binding and internalization of radioantibody bound to CAIX on tumor cells in vivo. (89)Zr-cG250 is likely to provide high-quality PET images and may be a useful tool to quantify CAIX/cG250 receptor turnover and cG250-accessible antigen density non-invasively in man

Agents described in the Molecular Imaging and Contrast Agent Database for imaging carbonic anhydrase IX expression

Carbonic anhydrase IX (CA IX) is selectively expressed in a range of hypoxic tumours and is a validated endogenous hypoxia marker with prognostic significance; hence, CA IX is of great interest as a molecular imaging target in oncology. In this review, we present an overview of the different imaging agents and imaging modalities that have been applied for the in vivo detection of CA IX. The imaging agents reviewed are all entries in the Molecular Imaging and Contrast Agent Database (MICAD) and comprise antibody, antibody fragments and small molecule imaging agents. The effectiveness of these agents for imaging CA IX in vivo gave variable performance; however, a number of agents proved very capable. As molecular imaging has become indispensable in current medical practice we anticipate that the clinical significance of CA IX will see continued development and improvements in imaging agents for targeting this enzyme.Griffith Sciences, School of Natural SciencesFull Tex