Our Areas of Focus
Developing a Treatment for GUCY2D Leber Congenital Amaurosis (LCA1)-
Two decades ago, I was assigned a Ph.D. thesis project to develop a gene therapy for vision loss in multiple animal models of LCA1. I continued to focus on this condition as a postdoctoral fellow, during which time I discovered the necessary components (viral vector, capsid and transgene cassette) that efficiently conferred therapy. My lab went on to successfully restore retinal function and useful vision over the long term in 3 different mouse models of LCA1. In 2014, I partnered with Genzyme/Sanofi to conduct the final pre-clinical studies necessary to bring a gene therapy for LCA1 into the clinic. Phase I/II clinical trials began in 2019 (NCT03920007). The program was then licensed to Atsena Therapeutics, a biotech start-up I co-founded and for which I serve as Director/CSO. Excitingly, both safety and efficacy have been demonstrated. Clinically meaningful improvements in patient quality of life are being re-ported by multiple participants treated with ATSN-101. For example, they are reading food labels for the first time, seeing snowflakes for the first time, and navigating outside their home at night for the first time! It has been an absolute pleasure to help guide this science from bench to bedside and I look forward to moving it into a Phase III trial and, ultimately, to approval!
Developing a Treatment for X-linked retinoschisis
Subretinal delivery of AAV to the peripheral retina is generally well tolerated, but surgical detachment of the central retina (macula and fovea) can lead to loss of central retinal thickness and visual acuity. Most existing AAV capsids only transduce cells within the subretinal injection bleb, meaning that macular transduction is enabled only following submacular injection. For the reasons noted above, our lab has worked to design AAV capsids that can target cells in the macula/fovea without the need for surgical detachment of this fragile region, and those capable of targeting a wider expanse of retina without the need to increase bleb size or vector concentration to levels that could illicit a humoral immune response. AAV.SPR, also referred to as AAV44.9(E531D), is a rationally designed capsid that is satisfying these requirements. AAV.SPR spreads laterally beyond the margins of the subretinal injection bleb, is more potent than benchmark vectors, and it enables safe and efficient transduction of foveal cones without the need for foveal detachment and transduction of a much larger area of retina. These features increase its safety (can be delivered at lower doses thereby lowering the risk of immune response) and potential for efficacy using agency-approved outcomes (i.e. an approvable level of improvement in microperimetry of ≥7dB in at least 5 prespecified loci). In 2023, Atsena Therapeutics initiated a Phase 1/2 clinical trial (NCT05878860) using AAV.SPR containing human RS1 (retinoschisin) to treat X-linked retinoschisis (XLRS). AAV.SPR was the logical choice for addressing this condition because 1) it efficiently transduces photoreceptors (the target cell) and 2) can be injected far away from the central schisis cavities (separations in the retinal layers) and, by virtue of its spread, still efficiently deliver therapeutic RS1 to those central cells. This program is based on strong preclinical data and I look forward to the readout in patients!
Developing Treatments for Inherited Retinal Disease Associated with Mutations in Large Genes
A significant hurdle in the retinal gene therapy field is how to efficiently deliver large therapeutic genes to photoreceptors. A limitation of AAV is its relatively modest genetic packaging capacity (you can’t fit more than 5,000 bp of DNA inside an AAV capsid). Despite this, it is to date the only viral (and non-viral) vector capable of efficiently transducing photoreceptors and maintaining persistent expression. To overcome the size limitation, the Boye Lab has developed dual AAV vector platforms wherein the therapeutic gene is split in half and delivered via two different vectors. Once inside the cell, these halves recombine via complementary sequence to the form full-length gene. We have worked for a decade to optimize these dual AAV vectors to enable preservation of vision in patients with MYO7A-associated Usher syndrome (USH1B). In 2020, Atsena Therapeutics licensed this technology and, together, we have generated a strong preclinical data packet which supports the use of these dual vectors in USH1B patients. Specifically, we have confirmed the sequence fidelity of the recombined gene, that it encodes full-length protein, and that it is well tolerated following subretinal injection in a clinically relevant species. I look forward to bringing this from the bench to the bedside in the very near future.
Engineering AAV for Safe and Efficient Gene Delivery to the Human Retina
FDA approval of an Adeno associated virus (AAV)- based gene therapy for RPE65-Leber congenital amaurosis (LCA2) solidified gene therapy’s place in current medical practice. However, in the 6 years since, there have been no additional approvals, and multiple hurdles associated with retinal gene therapy have come to light. The development of therapies that safely and efficiently target the human retina remains a significant, unmet need. In the Boye Lab, we ask questions grounded in both basic and translational science to elaborate upon biological determinants of retinal transduction by AAV via different routes of administration. Results from clinical trials utilizing intravitreally injected AAVs have shown dose-limiting inflammation, and neutralization of the AAV capsid by pre-existing antibodies (NAbs), implicating the host immune system as barrier to clinical translation. The eye’s ‘immune-privilege’ has perhaps led to an under appreciation of the immune system’s role in shaping the outcome of intra-ocularly delivered AAVs. Naturally occurring antibodies to capsids capable of transducing retina via the vitreous (i.e. AAV2) are prevalent in up to 70% of humans. As such, a large percentage of patients will not meet inclusion criteria for emerging therapies. We are actively working to overcome these barriers by 1) enhancing transduction and safety of intravitreally delivered AAVs by engineering the capsid and genome to avoid immune recognition, 2) enhancing retinal transduction by subILM delivery of AAVs to enable efficient and specific transduction of inner and outer retina, and 3) enhancing transduction by subretinally delivered AAVs that spread laterally beyond the injection site.