Background: A new delivery method of anti-GD2 antibody ch14.18/CHO by long term infusion (LTI) may improve the toxicity profile but maintain effective immune modulation and clinical activity in patients (pts) with high risk relapsed/refractory neuroblastoma (NB).
Methods: 124 pts were enrolled into an open label Phase II clinical trial (EudraCT 2009-018077-31) to receive up to 5 cycles of 6x106 IU/m2 sc IL2 (d1-5; 8-12), LTI of 100 mg/m2 ch14.18/CHO (d8-17) and 160 mg/m2 oral 13-cis-RA (d19-32)(APN311-202). Primary efficacy endpoints were antibody (>1µg/ml) and NK-cell levels. Toxicity endpoint was i.v. morphine free antibody delivery after 5 days of cycle 1 in >80% patients. Secondary endpoints were increased ADCC levels over baseline, Fc gamma receptor (FCGR) polymorphisms, objective clinical responses and progression as well as overall survival.
Results:
All per protocol treated patients met primary efficacy endpoints. This translated into an increase in ADCC in all evaluable patients. Toxicity observed in this trial was improved compared to standard delivery methods of anti-GD2 antibodies. Objective clinical response rate observed in this trial was 40%. The survival update of the cohort revealed a 2-y OS of 64±6% (mean OS 2.7± 0.2 y, median EFS 3.7 y (95% CI: 2.0-3.7 y)) and a 2-y EFS of 53 ± 6% (mean EFS 2.0 ± 0.2 y, median EFS 2.3 y (95% CI: 1.2-3.3 y)). This result is clearly superior to historical controls not treated with ch14.18/CHO (p<0.001), indicating clinical efficacy of the treatment.
In this cohort, we found 63/124 pts with low affinity FCGR alleles (FCGR2A-H131R/R and/or FCGRA3A-V158 F/F). These patients showed lower EFS and OS rates compared to 59/124 patients with high affinity FCGR polymorphisms (p<0.05). These findings underline FCGR mediated ADCC as mechanism of action of this treatment modality.
Conclusion: Results of this Phase II study show efficacy, clinical activity and improved toxicity profile of a new delivery method of ch14.18/CHO and underline ADCC as the mechanism of action.