TY - JOUR T1 - Bispecific INV721 antibody improves specific targeting in neuroblastoma to limit neuropathic pain JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 8 LP - 8 VL - 62 IS - supplement 1 AU - Zachary Rosenkrans AU - Amy Erbe AU - Bonnie Hammer AU - Bryan Glaser AU - Chris Massey AU - Arika Feils AU - Eduardo Aluicio-Sarduy AU - Daniel Gerhardt AU - Jennifer Dennin AU - Jonathan Engle AU - Paul Sondel AU - Roland Green AU - Reinier Hernandez Y1 - 2021/05/01 UR - http://jnm.snmjournals.org/content/62/supplement_1/8.abstract N2 - 8Objectives: Neuroblastoma is the most common extra-cranial solid tumor in pediatric patients. The standard of care for high-risk patients includes a monoclonal antibody (dinutuximab) that targets disialoganglioside 2 (GD2). Severe neuropathic pain often results from treatment with an anti-GD2 antibody because GD2 is expressed on peripheral nerves. Other tumor antigens, which are not expressed on nervous tissue, such as B7H3 (CD276), have also been identified for neuroblastoma treatment. We developed a next-generation bispecific antibody targeting GD2 and B7H3 to mitigate toxicity from off-target binding to GD2 positive neural cells that do not co-express B7H3 for improved neuroblastoma targeting. Methods: INV721 was engineered to bispecifically target GD2 and B7H3. The design allows INV721 to bind strongly when GD2 and B7H3 are expressed concurrently on tumors but has decreased avidity when only GD2 or B7H3 are present. INV721, dinutuximab, and a non-specific control (BB WT) were conjugated with deferoxamine for radiolabeling with Zr-89 (t1/2 = 78.4 h). B78 melanomas, expressing both (GD2+/B7H3+), either (GD2+/B7H3- or GD2-/B7H3+), or neither GD2 and B7H3 (GD2-/B7H3-), were implanted on the upper and lower flanks of C57Bl/6 mice for internal control purposes. 89Zr-Df-INV721, 89Zr-Df-dinutuximab, and 89Zr-Df-BB WT were then administered (3.7 MBq) separately for longitudinal PET imaging studies. PET images were acquired using an Inveon microPET/CT scanner and reconstructed using the OSEM3D/MAP algorithm. The Inveon Research Workstation software was used to quantify regions-of-interest (ROIs), with data calculated as percent injected dose per gram of tissue (%ID/g). Quantification of the uptake in the spine was used as a measure of GD2 targeting on nervous tissue, with the BB WT control serving as a measure of background Zr-89 uptake. After the last scanning time point at 72 h post-injection (p.i.), the mice were euthanized, and the major organs were collected for ex vivo biodistribution studies. P-values were calculated using a two-tailed Student’s t-test. Results: Longitudinal PET imaging studies revealed maximal 89Zr-Df-INV721 tumor uptake when GD2 and B7H3 were both highly expressed. The highest tumor uptake in the GD2 and B7H3 positive tumor occurred at 48 h p.i. (8.7±1.2 %ID/g), which was significantly higher than the only GD2 positive tumor (4.6±0.4 %ID/g, p=0.005). In comparison, we observed high uptake of 89Zr-Df-dinutuximab only in GD2+ tumors and low uptake for 89Zr-Df-BB WT in all tumors regardless of target expression. The spine uptake for all groups peaked at 72 h p.i., when the uptake for 89Zr-Df-dinutuximab (6.9±0.6%ID/g) was significantly higher compared to 89Zr-Df-INV721 (3.5±0.6%ID/g, p=0.0008), indicating the reduced affinity of the latter for this off-target tissue. Ex vivo biodistribution studies determined uptake in the GD2+/B7H3+ tumors to be 10.7±0.4, 12.0±5.2, and 4.6±0.8 %ID/g for 89Zr-Df-INV721, 89Zr-Df-dinutuximab, and 89Zr-Df-BB WT, respectively. In comparison, GD2+ and B7H3 negative tumors had an uptake of 6.6±1.0, 11.8±2.1, and 4.5±1.0 %ID/g for 89Zr-Df-INV721, 89Zr-Df-dinutuximab, and 89Zr-Df-BB WT, respectively. 89Zr-Df-INV721 uptake in the GD2+/B7H3+ tumors was significantly higher than the GD2+/B7H3- tumors (p=0.002), but there was no significant difference between the tumors for 89Zr-Df-dinutuximab or 89Zr-Df-BB WT. Conclusion: Our results demonstrated the bispecific character of the INV721 antibody by finding elevated uptake in GD2+/B7H3+ tumors but limited uptake in those expressing either or none of the targets. Off target uptake in the spine (GD2+) was decreased for INV721 compared to an anti-GD2 antibody. This study indicates that INV721 is an excellent candidate for neuroblastoma treatment that may limit neuropathic pain compared to the currently available anti-GD2 antibody therapies in the clinic. ER -