Background: EDO-S101 is an alkylating histone-deacetylase inhibitor (HDACi) fusion molecule that combines the strong DNA damaging effect of Bendamustine, with a fully functional pan-HDAC inhibitor, vorinostat. In this work, we investigated the preclinical rationale for the use of EDO-S101 in Hodgkin lymphoma (HL).
Material and methods:
In-vitro, a panel of 8 HL cell lines was used to study the cytotoxicity of EDO-S101 alone and combined with radiation therapy, and to investigate its cellular and molecular effects. In vivo, we investigated in immunodeficient NOD/SCID-gammac-/- mice xenografted with the L428 the antitumor effect of EDO-S101 alone . This evaluation, based on organ infiltration and survival, was performed following one single (60mg/kg or 80mg/kg) dosing or a repeat- dose (60mg/kg) of EDO-S101.
Results:
In-Vitro, the IC50 of EDO-S101 ranged between 1.6 to 6.3mM in 8 Hl cell lines after a 48 h-exposure. All HL cell lines showed a high sensitivity to EDO-S101; a clonogenic survival assay confirmed these observations. Multiple mechanisms of action of EDO-S101 were identified.
In one group of HL cell lines (L428-L428-s, L540, SUP-HD, L591 and KMH2), activation of apoptosis was independent of the P53 status. The combination of EDO-S101 with irradiation demonstrated a dramatical enhancement of apoptotic cell death via G2 arrest.
In a second group (L1236 and HDLM2), with the higher sensitivity to EDO-S101, resistance to apoptosis was associated with a higher frequency of chromatid aberrations involved in mitotic cell death. The effect of radiation was marginal in this group.
In-Vivo, in mice engrafted with the L428 cells, treatment with EDO-S101 reduced drastically L428 cells infiltration, and prolonged survival of EDO-S101 treated mice in comparison with those untreated.
Histological evaluation of the infiltration of tumoral cells after EDO-S101 treatment showed a significant reduction of tumor cell infiltration, more pronounced after a single dose of 80 mg/kg EDO-S101 than after two administrations of 60mg/kg. We observed a high liver weight heterogeneity in untreated mice, contrasting with homogeneous weight in treated mice. The absence of necrotic cells and cell degeneration in treated mice could be correlated to the anti-tumoral effect of EDO-S101 confirming the efficacy of EDO-S101.
Conclusion:
Our results show the antitumoral activity of EDO-S101 in pre-clinical models of HL, both in-vitro and in-vivo.