A new patch embedded with microneedles may deliver anti-PD-1 antibodies directly to the site of melanoma, according to a study in Nano Letters.

In animal studies, the technique more effectively targeted melanoma than other immunotherapy treatments.

Recently, cancer immunotherapy research has focused on using “anti-PD-1” antibodies to prevent cancer cells from tricking T cells, but this poses several challenges, according to study author Chao Wang, a postdoctoral researcher in the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill. “First, the anti-PD-1 antibodies are usually injected into the bloodstream, so they cannot target the tumor site effectively. Second, the overdose of antibodies can cause side effects such as an autoimmune disorder,” he says.

To address these challenges, the researchers developed a patch that uses microneedles to deliver anti-PD-1 antibodies locally to the skin tumor. The microneedles are made from hyaluronic acid.

The anti-PD-1 antibodies are embedded in nanoparticles, along with glucose oxidase – an enzyme that produces acid when it comes into contact with glucose. These nanoparticles are then loaded into microneedles, which are arrayed on the surface of a patch.

When the patch is applied to a melanoma, blood enters the microneedles. The glucose in the blood makes the glucose oxidase produce acid, which slowly breaks down the nanoparticles. As the nanoparticles degrade, the anti-PD-1 antibodies are released directly into the tumor.

The researchers tested the technique against melanoma in a mouse model. The microneedle patch loaded with anti-PD-1 nanoparticles was compared to treatment by injecting anti-PD-1 antibodies directly into the bloodstream and to injecting anti-PD-1 nanoparticles directly into the tumor.

After 40 days, 40 percent of the mice who were treated using the microneedle patch survived and had no detectable remaining melanoma – compared to a zero percent survival rate for the control groups, the study showed.

The researchers also created a drug cocktail, consisting of anti-PD-1 and anti-CTLA-4 antibodies– which also helps T cells attack the cancer cells. Using this combination in the microneedle patch, 70 percent of the mice survived and had no detectable melanoma after 40 days.

The team is now seeking funding to pursue further studies and potential clinical translation.