Developing epigenetic synergistic drug combinations with albendazole in paediatric acute myeloid leukaemia Free

Acute myeloid leukaemia (AML) is an aggressive malignancy that account for ~25% of all paediatric cancers (Tebbi 2021). Over the last few decades, advancements in technologies, earlier diagnosis, better supportive care, and refinements of chemotherapy regimens have significantly improved the overall survival (OS) rate for paediatric AML. However, mortality rates remain unacceptably high with a five-year OS rate of ~70%. Unfortunately, there are also high relapse rates associated with paediatric AML at ~30% (Kantarjian et al. 2021; Elgarten et al. 2020). Alongside this, current treatment strategies can cause severe, toxic side effects (Hernandez et al. 2019). Therefore, there is an urgent clinical need for novel therapies that will provide efficacy against paediatric AML, whilst also reducing therapy-associated side effects.

We previously performed a single agent screen using the Screen-Well® FDA drug library in primary murine cells, representative of MLL-AF9-driven paediatric AML and normal karyotype HOXA9-Meis1 driven AML. We found the anthelmintic agent albendazole (ABZ) to have remarkable anti-leukaemia efficacy in vitro and in vivo while having negligible effects in a normal mouse and human cells. RNA-seq analysis of ABZ-treated AML cells identified 98 genes with increased expression, and 14 downregulated genes. IL1B, P38 MAPK and NF-kB were identified as key perturbed networks following ABZ treatment. Moreover, SELPLG was found to be top ranked upstream regulator of the ABZ gene signature. Finally, luciferase expressing THP-1 childhood AML cells were generated and pre-treated with either vehicle or ABZ and an untreated group included. Live tracking of pSLIEW-transduced AML cells in NSG mice showed ABZ decreased leukaemia burden and extended lifespan (median survival; Control (30 days) vs ABZ (53 days)).

To further improve the clinical efficacy and durability of ABZ response, we aim to develop synergistic combinations with ABZ. For this, we selected to evaluate epigenetic compounds in combination due to previous studies. Similar anthelmintic agents, mebendazole (MBZ) and parbendazole (PBZ), have been reported to have effects on epigenetic regulators that alter C-MYB degradation (Walf-Vorderwülbecke et al. 2018) and induce AML cell differentiation (Matuso et al. 2024). We performed a single agent in-house screen using the DiscoveryProbe™ Epigenetics Compound Library from ApexBio (n=328). The screen was performed on THP-1 and HL-60 cells to identify potential epigenetic agents to combine with ABZ. Both cell lines were treated at low concentrations (0.5 µM–5 µM) for several timepoints. Drugs that reduced cell viability to ≤95% were deemed as hits. 87 epigenetic drugs were taken forward and combined with ABZ to find potential synergistic combinations. These epigenetic hits represent various target families such as HDAC inhibitors (vorinostat, panobinostat, and CUDC-101), BET inhibitors (OTX-015, PFI-1, and (-)-JQ), aurora kinase inhibitors (MK-8745 and JNJ-7706621), and DNA synthesis inhibitors (cytarabine). Compared to the library, some epigenetic drug families were overrepresented as hits. For example, HDAC inhibitors represent 22.8% of the library but represent 31.03% of single agent hits. BET inhibitors represent 9.54% of drugs from the library and account for 13.79% of hits.

The combination screen was performed using a lower concentration range (0 µM, 0.1 µM, 0.25 µM and 0.5 µM) of the 87 epigenetic drugs and ABZ. Synergy was calculated using the SyngerFinder 3.0. A ZIP score of 10 or more was used to deem a combination synergistic. An additional threshold of an average cell inhibition percentage score of 20 or more was used to select synergistic hits to take forward for validation. This resulted in 40 synergistic hits that appeared in both cell lines. These combinations will be taken forward for further validation. HDAC inhibitors (vorinostat), BET inhibitors (OTX-015) and histone methyltransferase (MS023) were among the most represented epigenetic target families, indicating potential mechanism of action of the novel ABZ+epigenetic combination.

The novel drug candidate ABZ was found to have remarkable anti-leukaemia efficacy in murine and human models of childhood AML in vitro and in vivo while having negligible effects in normal cells. Current work is focused on evaluating ABZ+epigenetic synergistic combinations that will be taken forward for proteomics analysis and pre-clinical efficacy on AML patient samples.