The human eye is like an immunological fortress, with its ability to exclude unwanted intruders a boon when preventing infection but a burden when trying to deliver vital medicines. Researchers in China have now turned to an unusual source—pig semen—to develop eye drops that can deliver cancer drugs to the back of the eye.
In a mouse model of retinoblastoma, the eye drops killed cancer cells, slowed tumor growth and ultimately saved the rodents’ retinas, the researchers reported in Science Advances on March 27.
Most therapies that need to reach the retina, in the deepest recesses of the eye, use injections that are off-putting to patients and can themselves damage the vital organ. Scientists led by Yu Zhang, Ph.D., of Shenyang Pharmaceutical University in northeast China, extracted lipid-based particles called exosomes from pig semen and turned them into anti-cancer package carriers.
Zhang’s team was inspired by the discovery that exosomes “play a facilitative role in the penetration of physiological barriers in the female reproductive tract during sperm migration,” he told Fierce Biotech. This made them wonder whether the particles could slip through barriers in the eye, too.
In their study, the researchers found that exosomes can pass into the eye without damaging tissue, using a pathway mediated by epidermal growth factor receptors. This mechanism differs from how exosomes overcome barriers in the reproductive tract, the authors noted.
The team filled their seminal packages with nanoparticles called carbon dots, which have been gaining popularity as a diagnostic and therapeutic tool for cancer.
“Carbon dots have emerged as a promising approach for cancer therapy, owing to their enzyme-like activity and high safety profile,” Zhang explained. That said, the eye-dropping approach isn’t limited to just carbon dots.
“Research on exosomes as drug carriers is relatively mature, and their potential for encapsulating other therapeutic agents is theoretically feasible,” Zhang said.
Retinoblastoma is a common eye cancer in children that is fatal if untreated. While the disease is completely curable in high-income countries, patients fare far worse in low-and-middle-income nations, where 80% of cases occur, due to slow diagnosis and treatment.
Zhang is now continuing to explore exosomes from pigs, but is also prospecting bull semen too. He hopes to bring the new eye drops into human trials someday, but acknowledged “there is still a long way to go before that.”