Fimepinostat

Human immunodeficiency virus type 1 (HIV-1) persists in latent reservoirs, mainly within CD4 + T cells, which are refractory to antiretroviral therapy, and can lead to rapid viral rebound upon treatment interruption. The “shock and kill” strategy aims to eliminate latent reservoirs by inducing viral transcription through latency-reversing agents (LRAs), thereby exposing infected cells to immune-mediated clearance. We developed and validated a simple, low-cost, and highly reproducible in vitro screening protocol to evaluate the efficacy and safety of LRAs, using a two-color flow cytometry assay on ACH2 cells, a well-characterized model of HIV-1 latency. Using this method, we identified PEP005 and CUDC-907 as the most potent LRAs across multiple experimental settings. Their reactivation capacity was further confirmed through transcriptomic analysis, which revealed a significant upregulation of viral RNA copies following stimulation. In addition, we collaborated with Dompé for using the Exscalate platform, an innovative computer-aided drug discovery approach, together with the experimental validation, which led to the identification of Tandutinib, a tyrosine kinase and mTOR inhibitor, as a novel LRA candidate with appreciable latency-reversing activity in the ACH2 model. While the ACH2 cell line does not fully recapitulate the complexity of HIV latency in vivo , it offers a robust and scalable system for early-stage screening and prioritization of candidate LRAs. Importantly, the future application of these LRAs in ex vivo samples derived from people living with HIV, with a particular focus on pediatric samples, will be crucial to deepen our understanding of latency reactivation in clinically relevant settings and age-specific immune environments.

This study addresses a major obstacle to curing human immunodeficiency virus type 1 (HIV-1) infection: the persistence of latent viral reservoirs that are not eliminated by current therapies. We developed a simple and reproducible assay to identify compounds capable of reactivating latent virus, a key step in cure strategies. Using this approach, we identified effective latency-reversing compounds and, through collaboration with Dompé using the EXSCALATE platform, we also identified Tandutinib as a promising new candidate for further investigation.

Fimepinostat, an oral dual inhibitor of histone deacetylase (HDAC) and phosphatidylinositol‐4,5‐bisphosphate 3‐kinase (PI3K), has shown activity in preclinical models of Myc‐driven pediatric malignancies. This Phase 1 trial aimed to determine the recommended pediatric Phase 2 dose (RPP2D), describe the toxicity profile, and evaluate the pharmacokinetics of fimepinostat in children with relapsed and refractory solid and central nervous system (CNS) tumors.

This multicenter, Phase 1 study enrolled patients ages 1–21 years with relapsed or refractory solid tumors, CNS tumors, or lymphoma. The dose‐escalation phase followed a 3 + 3 design, starting at 27.5 mg/m 2 and escalating to 45 mg/m 2 . Following dose escalation, three expansion cohorts were opened including cohorts for patients with Myc(n)‐driven neuroblastoma, Myc‐driven extracranial solid tumors, and diffuse large B‐cell lymphoma or Burkitt lymphoma. The pharmacokinetics of fimepinostat and its metabolites were studied after the first dose.

Twenty‐six patients were enrolled, with 25 receiving treatment. The median age was 13.6 years (range: 4.1–20.9). In the dose‐escalation phase, 12 patients were evaluable for DLT assessment. The RPP2D was initially determined to be 45 mg/m 2 but was revised to 35 mg/m 2 after observing DLTs in the dose‐expansion phase. Treatment‐related adverse events were primarily hematologic and gastrointestinal. No objective responses were observed in 23 evaluable patients. Three patients had stable disease for over four cycles, including a patient with MYCN amplified neuroblastoma with stable disease for 24 cycles. Pharmacokinetic analysis showed significant interpatient variability and rapid conversion of fimepinostat to its metabolites.

Fimepinostat was tolerable at a dose of 35 mg/m 2 in children with relapsed and refractory solid and CNS tumors, but lacked significant clinical activity. Discovery of drugs to target Myc continues to be a high priority for childhood cancers.

ClinicalTrials.gov identifier: NCT02909777