Dose-ranging and further therapeutic evaluation of a bicistronic humanized TrkB-BDNF gene therapy for glaucoma in rodents

Andrew Osborne; Tasneem Z Khatib; Michael Whitehead; Terrance Mensah; Sadat Yazdouni; Bart Nieuwenhuis; Zara Ali; Jared Ching; Robert Watt; Naoki Kishi; Naoki Kozono; James R Tribble; Peter S Widdowson; Keith R Martin

doi:10.1186/s44477-025-00003-y

Dose-ranging and further therapeutic evaluation of a bicistronic humanized TrkB-BDNF gene therapy for glaucoma in rodents

Mol Neurodegener Adv. 2025;1(1):3. doi: 10.1186/s44477-025-00003-y. Epub 2025 Aug 18.

Authors

Andrew Osborne^{1

2

3}, Tasneem Z Khatib^{1

4

5

6}, Michael Whitehead^{1

3}, Terrance Mensah¹, Sadat Yazdouni^{1

4}, Bart Nieuwenhuis^{1

7}, Zara Ali^{1

4}, Jared Ching^{1

4}, Robert Watt¹, Naoki Kishi⁸, Naoki Kozono⁸, James R Tribble^{9

10}, Peter S Widdowson^{2

3}, Keith R Martin^{1

2

4

11

12}

Affiliations

¹ John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
² Quethera Ltd, Babraham Research Campus, Cambridge, UK.
³ Ikarovec Ltd, The Norwich Research Park Innovation Centre, Norwich, UK.
⁴ Eye Department, Addenbrooke's Hospital, Cambridge, UK.
⁵ Medical Sciences Division, University of Oxford, Oxford, UK.
⁶ Ophthalmology, Byers Eye Institute at Stanford, Stanford University, Stanford, CA USA.
⁷ Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
⁸ Astellas Pharma Inc. Miyukigaoka, Tsukuba, Ibaraki Japan.
⁹ School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK.
¹⁰ Department of Clinical Neuroscience, Division of Eye and Vision, St. Erik Eye Hospital, Karolinska Institutet, Stockholm, Sweden.
¹¹ Centre for Eye Research Australia, and Royal Victorian Eye and Ear Hospital, Melbourne, Australia.
¹² Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Australia.

Abstract

Background: Glaucoma is a leading cause of irreversible blindness, characterized by the progressive degeneration of retinal ganglion cells (RGCs). Activation of the Tropomyosin receptor kinase B (TrkB) pathway by mature brain-derived neurotrophic factor (mBDNF) has emerged as a promising neuroprotective strategy, given its critical role in promoting RGC survival in preclinical models.

Methods: We advanced the development of a bicistronic adeno-associated viral (AAV) gene therapy vector engineered to co-express human TrkB and mBDNF. The vector was optimized with fully human transgene sequences and evaluated for functional expression and dose scalability to support clinical translation. Expression tracking and efficiency were enhanced by incorporating a self-cleaving 2A peptide sequence.

Results: In a mouse model of optic nerve crush, intravitreal administration of 1.52E8 to 7.60E8 genome copies (GC)/eye significantly mitigated RGC damage. In a rat model of laser-induced ocular hypertension, doses ranging from 3.80E8 to 1.90E9 GC/eye preserved both visual function and RGC survival. The 2A peptide facilitated efficient co-expression of TrkB and mBDNF while minimizing interference from endogenous protein pathways.

Conclusions: These findings demonstrate that co-expression of human TrkB and mBDNF via a bicistronic AAV vector yields robust, dose-dependent neuroprotection and sustained transgene expression in two distinct models of glaucomatous injury. This gene therapy represents a promising first-in-class candidate for the treatment of glaucoma.

Supplementary information: The online version contains supplementary material available at 10.1186/s44477-025-00003-y.

Keywords: BDNF; Gene therapy; Glaucoma; Neuroprotection; TrkB.