An injectable vitreous substitute with sustained release of metformin for enhanced uveal melanoma immunotherapy.

Uveal melanoma (UM) is the most prevalent primary intraocular malignant tumor in adults with a high rate of metastasis. Conventional treatments have limited effects on metastasis and cause permanent ocular tissue defects. Here, a novel strategy based on an injectable vitreous substitute with sustained metformin release ability (IVS-Met) was reported for efficient UM therapy as well as for repairing vitreous deficiency and preserving visual function. IVS-Met showed an excellent long-term anti-tumor effect by direct tumor attack and modulation of the tumor microenvironment (TME). IVS-Met reduced the proportion of pro-tumor M2 tumor-associated macrophages and induced the pro-inflammatory M1 phenotype, thus reversing the immunosuppressive TME and eliciting robust anti-tumor immune responses. Notably, IVS-Met demonstrated high performance in the inhibition of UM metastasis and significantly extended the survival time of mice. In addition, the vitreous substitute achieved facile administration via direct injection and exhibited excellent rheological and optical properties with the key parameters very close to those of the vitreous body to repair vitreous deficiency and preserve visual function. In summary, this strategy has realized effective UM treatment while retaining eyeballs and vision for the first time, revealing great potential for translation to clinical practice.