Researchers at Rockefeller University are reporting encouraging results from an early clinical trial of a redesigned cancer immunotherapy that is injected directly into tumors.

In the small study, six of 12 patients experienced tumor shrinkage, and two patients went into complete remission, according to findings published in the journal Cancer Cell.

And remarkably, the treatment not only affected the injected tumors but those located in other areas of the body shrank or were eliminated by immune cells.

The therapy is based on a class of drugs known as CD40, which stimulate the immune system to recognize and attack cancer cells. Traditionally, these drugs have been given through the bloodstream, which can lead to widespread side effects such as inflammation and liver damage.

To reduce those risks, researchers modified the drug — called 2141-V11 — and changed how it is delivered. Instead of intravenous infusion, the treatment is injected directly into tumors.

“When we did that, we saw only mild toxicity,” said study author Jeffrey V. Ravetch of Rockefeller University.

In addition to shrinking the treated tumors, the therapy appeared to trigger a broader immune response throughout the body — an effect that surprised researchers.

“This effect -- where you inject locally but see a systemic response -- that's not something seen very often in any clinical treatment,” Ravetch said. “It's another very dramatic and unexpected result from our trial.”

In some cases, tumors that were not directly injected also shrank or disappeared. This occurred in two patients with advanced cancers — one with melanoma and another with breast cancer.

“The melanoma patient had dozens of metastatic tumors on her leg and foot, and we injected just one tumor up on her thigh,” Ravetch said. “After multiple injections of that one tumor, all the other tumors disappeared.”

“The same thing happened in the patient with metastatic breast cancer, who also had tumors in her skin, liver, and lung,” he added. “And even though we only injected the skin tumor, we saw all the tumors disappear.”

Researchers say the treatment works by activating T cells — immune cells that can seek out and destroy cancer throughout the body once they recognize it.

While the results are promising, the study was small, and more research is needed. Larger clinical trials are already underway, with nearly 200 patients enrolled.