A new imaging device, termed a "cryomacroscope", was used to observe macrofractures in the cryoprotectant cocktails DP6 and VS55. Details of the design and construction of the cryomacroscope were presented in Part I of this report, which focused on describing the apparatus and observations of crystallization. Part I and the current paper (Part II) describe events that occur as 1 mℓ of cryoprotectant contained in a glass vial is cooled from room temperature down to cryogenic temperatures (∼ -135°C). The presence of cracking, as well as patterns in their position and orientation, are found to be dependent on the cooling rate and on the specific cryoprotectant cocktail. Cracks, if present, disappear upon rewarming, although they appear to be sites for later preferential crystallization. Computations which predict temperatures and mechanical stresses are used to explain observations of cracking. In conjunction with these reports, additional photos of cryomacroscopy of vitrification, crystallization, and fracture formation are available at http://www.me.cmu.edu/faculty1/rabin/CryomacroscopyImages01.htm.

No abstract

Retinal gene therapy is a rapidly growing field with numerous clinical trials underway, and route of delivery is a critical contributor to its success. Subretinal administration, which involves pars plana vitrectomy in the operating room, offers targeted delivery to retinal-pigment epithelium cells and photoreceptors. Due to the immune-privileged nature of the subretinal space, the risk of an immune reaction against viral capsid antigens is minimized, an advantage of subretinal administration in patients with preexisting neutralizing antibodies. Intravitreal administration, with fewer procedure-related complications, is challenged by potential immune response and incomplete vector penetration through the internal limiting membrane. However, novel vectors, optimized by ''directed evolution'' may address these issues. Nonsurgical in-office suprachoroidal gene delivery offers the potential for greater surface-area coverage of the posterior segment compared to focal subretinal injection, and is not hindered by the internal limiting membrane. However, the vector must pass through multiple layers to reach the targeted retinal layers, and there is a risk of immune response. This review highlights recent developments, challenges, and future opportunities associated with viral and nonviral suprachoroidal gene delivery for the treatment of chorioretinal diseases. While ocular tolerability and short-term effectiveness of suprachoroidal gene delivery have been demonstrated in preclinical models, durability of gene expression, long-term safety, potential systemic exposure, and effective delivery to the macula require further exploration. Although the safety and efficacy of suprachoroidal gene delivery are yet to be proven in clinical trials, further optimization could facilitate nonsurgical in-office suprachoroidal gene therapy.

Suprachoroidal drug delivery technology has advanced rapidly and emerged as a promising administration route for a variety of therapeutic candidates, in order to target multiple ocular diseases, ranging from neovascular age-related macular degeneration to choroidal melanoma. This review summarizes the latest preclinical and clinical progress in suprachoroidal delivery of therapeutic agents, including small molecule suspensions, polymeric entrapped small molecules, gene therapy (viral and nonviral nanoparticles), viral nanoparticle conjugates (VNCs), and cell therapy. Formulation customization is critical in achieving favorable pharmacokinetics, and sustained drug release profiles have been repeatedly observed for multiple small molecule suspensions and polymeric formulations. Novel therapeutic agents such as viral and nonviral gene therapy, as well as VNCs, have demonstrated promise in animal studies. Several of these suprachoroidally-administered therapies have been assessed in clinical trials, including small molecule suspensions of triamcinolone acetonide and axitinib, viral vector RGX-314 for gene therapy, and VNC AU-011. With continued drug delivery research and optimization, coupled with customized drug formulations, suprachoroidal drug delivery may address large unmet therapeutic needs in ophthalmology, targeting affected tissues with novel therapies for efficacy benefits, compartmentalizing therapies away from unaffected tissues for safety benefits, and achieving durability to relieve the treatment burden noted with current agents.

Purpose This study assessed physician-investigator experience with suprachoroidal (SC) injections, an investigational therapeutic administration technique using a 900 or 1100 µm microneedle to inject drugs into the SC space. Methods Datasets from six clinical trials across three diseases (noninfectious uveitis; diabetic macula edema, and retinal vein occlusion) were assessed. In addition to a user survey, retrospective correlations were performed between procedural variables (needle length), and demographics, and ocular characteristics. Results In the user survey, 84% (31/37) of physician-investigators did not perceive the SC injections to be meaningfully more challenging than other ocular injections. For the correlation analysis, the 900 µm needle was used for 71% (412/581) of baseline injections, and switching to the longer needle occured in the remaining 29% of baseline injections. No statistical correlations were found between needle lengths and age, race, disorder, refraction, visual acuity, intraocular pressure, retinal central subfield thickness, or lens status. Patient gender and needle length were statistically associated, with 76% (210/275) versus 66% (202/306) of injections administered with 900 µm needles for female and male gender, respectively. Injection quadrant correlated to needle length with 78% (214/275) of superotemporal quadrant injections administered with 900 µm needles, compared with 65% (73/113) of inferotemporal quadrant injections. Conclusions Both the user survey and the correlation analysis demonstrated that SC injection is well accepted by physician-investigators, and the two needle lengths accommodate a wide range of anatomic and demographic variables. Translational Relevance These results, along with the presented ex-vivo endoscopic imaging, suggest that SC injection could be readily adopted in clinical practice for targeted compartmentalized delivery of ocular therapeutics.