It's early in the trials, but a treatment used to help the immune system fight blood cancers is showing great promise against solid tumors as well.

If shown successful, the treatment called CAR-T therapy could revolutionize cancer therapy by being an effective option for a wider range of cancer patients beyond leukemia and other blood cancers.

According to a report from the American Association for Cancer Research, scientists presented the results of a phase 1 clinical trial at the AACR Annual Meeting 2019 on March 29 to April 3.

Prasad S. Adusumilli, MD, says that patients who have advanced-stage solid tumors that are metastatic in the chest cavity usually see poor outcomes even with treatment. CAR-T is an excellent option, but beyond blood cancers, it has had little success.

Now, Adusumilli and his team has developed a new CAR-T cell that can achieve success in solid tumors, and early tests show that this is a promising new treatment.

CAR-T Cell Therapy: How Does It Work?

CAR-T cell therapy is when doctors genetically modifies a number of the patient's cells to help them recognize and attack cancer. It was initially approved and used for leukemia and lymphomas, injecting the modified immune system cells directly into the blood, where the cancer is.

The problem for other types of cancer is the therapy hasn't succeeded in cases where the cells have to go from the bloodstream to wherever the tumor is, whether it's in the lung, breast, or other organs.

Furthermore, the proteins that the therapy targets are also present in normal cells, which means even healthy cells can be attacked by the modified cells.

For the study, Adusumilli and the rest of the team developed a new CAR-T cell that could overcome these issues. AACR reports that the new mesothelin-targeted CAR-T cells, called IcasM28z, contains the Icaspase-9 "suicide switch" that can be triggered to destroy all CAR-T cells when it exhibits unexpected toxicity inside a patient's body.

Early Trials Show Great Potential For CAR-T Therapy

Trials included 19 patients with mesothelioma, plus two other patients with lung and breast cancer that have already metastasized to the chest cavity. The modified cells were injected into the chest where the tumors were located.

One patient underwent surgery and radiation after the therapy and continues to do well without additional treatments 20 months later.

Fifteen of the patients saw their conditions improve enough to start taking a drug for the immune system, with 11 observed long enough to display results. Of the 11, two went into remission from cancer, with one relapsing later. Six had their tumors shrink, while the cancers of three worsened.

Of course, Adusumilli stresses that these findings are limited since the researchers are only at phase 1 of the trials.

Still, the research offers hope that CAR-T therapy could be developed further to treat different kinds of cancer patients.

"The novelty of our study is that the CAR-T cells target the cancer cell-surface protein, mesothelin, which is expressed on the majority of cancer cells, and they are delivered directly to the tumor site using regional delivery techniques," Adusumilli explains. "If this approach is successful, 2 million patients with mesothelin-expressing solid tumors per year in the United States will be eligible for this treatment."

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