Purpose Immunotherapy of high-risk neuroblastoma using the anti-GD2 antibody dinutuximab induces antibody-dependent cell-mediated cytotoxicity (ADCC). Galunisertib, an inhibitor of TGFβR1, was examined for its ability to enhance the efficacy of dinutuximab in combination with human ex vivo activated NK (aNK) cells against neuroblastoma. Experimental Design TGFB1 and TGFBR1 mRNA expression was determined for 249 primary neuroblastoma tumors by microarray analysis. The ability of galunisertib to inhibit SMAD activity induced by neuroblastoma patient blood and bone marrow plasmas in neuroblastoma cells was tested. The impact of galunisertib on TGFβ1-induced inhibition of aNK cytotoxicity and ADCC in vitro and on anti-neuroblastoma activity in NSG mice was determined. Results Neuroblastomas express TGFB1 and TGFBR1 mRNA. Galunisertib suppressed SMAD activation in neuroblastoma cells induced by exogenous TGFβ1 or by patient blood and bone marrow plasma, and suppressed SMAD2 phosphorylation in human neuroblastoma cells growing in NSG mice. In NK cells treated in vitro with exogenous TGFβ1, galunisertib suppressed SMAD2 phosphorylation and restored the expression of DNAM-1, NKp30, and NKG2D cytotoxicity receptors, TRAIL death ligand, the release of perforin and granzyme A, and the direct cytotoxicity and ADCC of aNK cells against NB cells. Addition of galunisertib to adoptive cell therapy with aNK cells plus dinutuximab reduced tumor growth and increased survival of mice injected with two neuroblastoma cell lines or a patient-derived xenograft. Conclusion Galunisertib suppresses activation of SMAD2 in neuroblastomas and aNK cells, restores NK cytotoxic mechanisms, and increases the efficacy of dinutuximab with aNK cells against neuroblastoma tumors.

We determined whether quantifying neuroblastoma-associated mRNAs (NB-mRNAs) in bone marrow and blood improves assessment of disease and prediction of disease progression in patients with relapsed/refractory neuroblastoma. mRNA for CHGA, DCX, DDC, PHOX2B, and TH was quantified in bone marrow and blood from 101 patients concurrently with clinical disease evaluations. Correlation between NB-mRNA (delta cycle threshold, Δ, for the geometric mean of genes from the TaqMan Low Density Array NB5 assay) and morphologically defined tumor cell percentage in bone marrow, I-meta-iodobenzylguanidine (MIBG) Curie score, and CT/MRI-defined tumor longest diameter was determined. Time-dependent covariate Cox regression was used to analyze the relationship between Δ and progression-free survival (PFS). NB-mRNA was detectable in 83% of bone marrow (185/223) and 63% (89/142) of blood specimens, and their Δ values were correlated (Spearman = 0.67, < 0.0001), although bone marrow was 7.9 ± 0.5 stronger than blood When bone marrow morphology, MIBG, or CT/MRI were positive, NB-mRNA was detected in 99% (99/100), 88% (100/113), and 81% (82/101) of bone marrow samples. When all three were negative, NB-mRNA was detected in 55% (11/20) of bone marrow samples. Bone marrow NB-mRNA correlated with bone marrow morphology or MIBG positivity ( < 0.0001 and = 0.007). Bone marrow and blood Δ values correlated with PFS ( < 0.001; = 0.001) even when bone marrow was morphologically negative ( = 0.001; = 0.014). Multivariate analysis showed that bone marrow and blood Δ values were associated with PFS independently of clinical disease and gene status ( < 0.001; = 0.055). This five-gene NB5 assay for NB-mRNA improves definition of disease status and correlates independently with PFS in relapsed/refractory neuroblastoma. .