The Novel Nano-Formulation of the HDAC Inhibitor, Romidepsin, for the Treatment of Relapsed, Refractory Peripheral T-Cell Lymphoma

Background: The peripheral T-cell lymphomas (PTCL) are a heterogeneous group of diseases often associated with a poor outcome. Since conventional chemotherapy fails to produce cure in the majority of patients, there is a lack of accepted standard of care for most PTCL subtypes. The PTCL appear to be a group of diseases characterized by gross epigenetic dysregulation with a unique vulnerability to epigenetic modulation. Recurring mutations in IDH2, TET2 and DNMT3A, which create a hypermethylator phenotype, coupled with mutations in genes that control histone acetylation such as EP300 and CREBBP, have been identified as recurrent in several subtypes of PTCL. Despite the approval of several drugs for patients with relapsed or refractory disease, the prognosis for patients with PTCL are dismally low. The approval of histone deacetylase inhibitors (HDACi) coupled with recent evidence suggesting that combinations of epigenetically targeted drugs induce clinically meaningful results has created a drug development strategy that offers an innovative approach to these complex diseases. The HDACi exhibit a lineage selective activity against the PTCL, with 4 HDACi (Belinostat, Romidepsin, Vorinostat and Chidamide) approved for Relapsed/Refractory (R/R) TCL patients around the world. Although Romidepsin was approved by the FDA for the treatment of cutaneous TCL and R/R PTCL, its indication in R/R PTCL was recently withdrawn due to the negative result of the Phase 4 commitment study.

Objectives: We aim to develop a novel nano-encapsulated formulation of Romidepsin (Romi) with a superior safety and efficacy profile with a more convenient dosing schedule.

Methods: Using a combinatorial strategy of solvent screening and polymer chemistries, we developed a first-in-class nano-romidepsin (NanoRomi). We utilized Dynamic Light Scattering (DLS), Cryo-EM to characterize the size and morphology of the nanoparticles and LC-MS-defined drug loading to "lock down” a nanoparticle formulation for in vitro testing. Cell viability, flow cytometry and western blotting (WB) assays were performed to determine the NanoRomi mediated cell death, apoptosis and histone acetylation in TCL cell lines. To determine maximum tolerated dose of the NanoRomi vs free Romi, in vivo single-dose toxicity study was performed. The clinical score and weight loss of the mice were considered endpoints. For pharmacokinetics study, mice were treated at the ½ MTD and plasma was isolated from blood collected at time points following a single treatment for mass spectrometry based quantification of drug levels.

Results: We developed NanoRomi by nanoprecipitation or solvent displacement method using a specific Drug/Polymer/Surfactant ratio. Cryo-EM and DLS confirmed that NanoRomi had a poly-dispersity index between 0.16 to 0.27 and a z-average of 60-70 nm, indicating uniform size and homogenous particle distribution. At 60 hours, the TCL cell lines were consistently sensitive to NanoRomi (IC50: 0.7-1.9 nM), which was comparable to Romi (Fig 1A). Flow cytometry for cleaved PARP demonstrated that treatment with NanoRomi induced apoptosis similar to Romi. WB analysis showed increased acetylation of histone H3 and H4 in a time and concentration-dependent manner. In vivo single-dose toxicity assay showed a clear correlation between dose and weight loss and/or clinical score in both free Romi and NanoRomi treated groups. Mice reached humane endpoints at 8 mg/kg treatment for intraperitoneal route of administration for both the drugs. Preliminary PK analysis indicated that the t_1/2 of Romi (plasma) is comparable between free Romi and NanoRomi treatments while the Cmax and AUC for NanoRomi is 3 to 4-fold higher compared to the free Romi. The plasma-concentration time courses of Romi after the intraperitoneal administration of the free Romi and NanoRomi showed that the drug reached maximum concentration after 6 hours and 3 hours for free Romi and NanoRomi, respectively (Fig 1B).

Conclusions: These studies confirm that NanoRomi effectively targets tumor cells producing the same constellation of effects seen with free Romi. In addition, the in vivo studies suggest a likely superior safety and pharmacokinetic profile. NanoRomi may represent a valuable asset with unique properties that favorably distinguish it from free Romi. Ongoing studies are focused on the in vivo therapeutic efficacy, as we translate the development of this agent to Phase 1 studies.

Manavalan:Astex: Research Funding. O'Connor:TG Therapeutics: Current Employment, Current equity holder in publicly-traded company. Loughran:Keystone Nano: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Recludix Pharma: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Kymera Therapeutics: Honoraria; Prime Genomics: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Dren Bio, Inc: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees. Kester:Keystone Nano: Current equity holder in private company, Other: CTO and co-founder. Feith:Recludix Pharma: Research Funding; AstraZeneca: Research Funding; Kymera Therapeutics: Honoraria. Marchi:Myeloid Therapeutics: Ended employment in the past 24 months, Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; Celgene/BMS: Research Funding; University of virginia: Patents & Royalties: 3062/170 PROV; NomoCan Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding; Kyowa Kirin: Honoraria; Daiichi Sankyo: Other: Participation at advisory board.