Intravitreal HDAC Inhibitor Belinostat Effectively Eradicates Vitreous Seeds Without Retinal Toxicity In Vivo in a Rabbit Retinoblastoma Model.

Abstract

Purpose:

Current melphalan-based regimens for intravitreal chemotherapy for retinoblastoma vitreous seeds are effective but toxic to the retina. Thus, alternative agents are needed. Based on the known biology of histone deacetylases (HDACs) in the retinoblastoma pathway, we systematically studied whether the HDAC inhibitor belinostat is a viable, molecularly targeted alternative agent for intravitreal delivery that might provide comparable efficacy, without toxicity.

Methods:

In vivo pharmacokinetic experiments in rabbits and in vitro cytotoxicity experiments were performed to determine the 90% inhibitory concentration (IC90). Functional toxicity by electroretinography and structural toxicity by optical coherence tomography (OCT), OCT angiography, and histopathology were evaluated in rabbits following three injections of belinostat 350 µg (2× IC90) or 700 µg (4× IC90), compared with melphalan 12.5 µg (rabbit equivalent of the human dose). The relative efficacy of intravitreal belinostat versus melphalan to treat WERI-Rb1 human cell xenografts in rabbit eyes was directly quantified. RNA sequencing was used to assess belinostat-induced changes in RB cell gene expression.

Results:

The maximum nontoxic dose of belinostat was 350 µg, which caused no reductions in electroretinography parameters, retinal microvascular loss on OCT angiography, or retinal degeneration. Melphalan caused severe retinal structural and functional toxicity. Belinostat 350 µg (equivalent to 700 µg in the larger human eye) was equally effective at eradicating vitreous seeds in the rabbit xenograft model compared with melphalan (95.5% reduction for belinostat, P < 0.001; 89.4% reduction for melphalan, P < 0.001; belinostat vs. melphalan, P = 0.10). Even 700 µg belinostat (equivalent to 1400 µg in humans) caused only minimal toxicity. Widespread changes in gene expression resulted.

Conclusions:

Molecularly targeted inhibition of HDACs with intravitreal belinostat was equally effective as standard-of-care melphalan but without retinal toxicity. Belinostat may therefore be an attractive agent to pursue clinically for intravitreal treatment of retinoblastoma.

• Authors: Jessica V Kaczmarek, Carley M Bogan, Janene M Pierce, Yuankai K Tao, Sheau-Chiann Chen, Qi Liu, Xiao Liu, Kelli L Boyd, M Wade Calcutt, Thomas M Bridges, Craig W Lindsley, Debra L Friedman, Ann Richmond, Anthony B Daniels
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 62 Issue 14 Pg. 8 (11 01 2021) ISSN: 1552-5783 [Electronic] United States
• PMID: 34757417 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Annexin A5
• Antineoplastic Agents, Alkylating
• Histone Deacetylase Inhibitors
• Hydroxamic Acids
• Sulfonamides
• belinostat
• Melphalan

Topics

• Animals
• Annexin A5
• Antineoplastic Agents, Alkylating (therapeutic use)
• Disease Models, Animal
• Electroretinography
• Fluorescein Angiography
• Histone Deacetylase Inhibitors (pharmacokinetics, therapeutic use, toxicity)
• Hydroxamic Acids (pharmacokinetics, therapeutic use, toxicity)
• Intravitreal Injections
• Maximum Tolerated Dose
• Melphalan (therapeutic use)
• Neoplasm Seeding
• Rabbits
• Retina (drug effects, physiology)
• Retinal Neoplasms (diagnosis, drug therapy, physiopathology)
• Retinoblastoma (diagnosis, drug therapy, physiopathology)
• Retrospective Studies
• Sulfonamides (pharmacokinetics, therapeutic use, toxicity)
• Tomography, Optical Coherence
• Vitreous Body (metabolism)
• Xenograft Model Antitumor Assays