Early response rates and Curie scores at end of induction: An update from a phase II study of an anti-GD2 monoclonal antibody (mAb) with chemotherapy (CT) in newly diagnosed patients (pts) with high-risk (HR) neuroblastoma (NB).

Abstract

10534 Background: We are conducting a Phase II trial of the anti-GD2 mAb hu14.18K322A given concomitantly with CT in newly diagnosed pts with HR NB. Our primary objective is to compare the response rate (RR; defined as ≥ PR) after two courses of CT with cyclophosphamide (CTX)/topotecan (TPT) and hu14.18K322A with GM-CSF and IL-2 to the RR reported by Park et al. (JCO 29:4351, 2011), using identical CT with GCSF only, in a two-stage group sequential design. Semiquantitative MIBG scoring (Curie; CS) has been shown to be a prognostic indicator of outcome in pts with HR NB (Yanik et al, J Nucl Med, 2013), particularly, those with CS > 2 at end of induction (EoI) CT have inferior outcomes. Here we update the RR and report the CS at EoI CT. Methods: Pts received induction CT (6 cycles) as described by Park et al, with the addition of hu14.18K332A (on d 2-5; 40mg/m2/d x 4d), daily sc GM-CSF and sc IL-2 (1 x 106 IU/m2/dose) qod x 6. 123I-MIBG scans and scoring (CS) were obtained on all pts at diagnosis, after second course of CT and at EoI. Results: 42 evaluable pts completed the first two courses of CT (24 male, median age 2.9 yrs (range 6 m -15.2 yrs), 36 INSS 4, 19 MYCNamplified); 40/42 evaluable pts had measurable reductions in primary tumor volume after two courses of CT (median 79%, average 69%, range +5 – 100%). Responses (≥ PR) after two courses were seen in 32/42 (76.2%; 95% CI 61.3 – 87.9%); No mAb dose-reductions were made but 20/43 (47%) pts had infusion times extended. The development of human anti-human antibody reactivity (HAHA) to hu14.18K322A in the first 22 pts is minimal. Of the 36 INSS 4 pts, 1 withdrew prior to EoI and 2 are too early. The median CS at diagnosis for the 33 stage 4 pts who have completed induction CT was 18 (range 1 – 28). At EoI the median CS was 0 (range 0 -23); 29/33 INSS 4 pts had EoI CS ≤ 2. Conclusions: The addition of hu14.18K322A to two courses of CTX/TPT significantly improves the RR compared to two courses of CTX/TPT alone (32/42 vs 12/30 as reported by Park et al,; P = 0.000004). The improved median CS of the stage 4 patients from 18 at diagnosis to 0 at EoI suggest the improvement in early RR may translate into improved EFS as well. Clinical trial information: NCT01857934.