VISTA protein clinical trials recently tested a drug known as CA-170 for its potential effectiveness as a type of cancer therapy. CA-170 is an immunotherapy drug that prevents the deactivation of immune system T-cells by cancer cells. The trials, which included mesothelioma patients, recently concluded.
What Is VISTA? Immune Checkpoint Proteins and Inhibitors
VISTA (V-domain Ig suppressor of T-cell activation) is a type of protein that helps cancer cells avoid attack by the body’s immune system.
What Are Immune Checkpoints?
Immune system T-cells have proteins on their surfaces known as checkpoints. Other cells have proteins on their surfaces that interact with these checkpoints, turning them off and telling the immune cell not to attack. The VISTA clinical trial was the first to test a drug that targets these proteins.
What Are Immune Checkpoint Inhibitors?
Healthy cells have specific proteins that bind to and disable checkpoints on T-cells, protecting them from the immune system.
Unfortunately, cancer cells also often have these proteins they evolved to protect them from the immune system. PD-1 is one example of a checkpoint protein targeted by new cancer therapies. T-cells have PD-1 on their outer surfaces. When PD-1 binds to a protein known as PD-L1 on other cells, it knows not to attack that cell.
Drugs that target either PD-1 or PD-L1 can potentially block the interaction between immune cells and cancer cells. This allows T-cells to recognize, attack, and kill cells in the tumor. VISTA is another checkpoint protein that researchers are targeting.
How Is VISTA Important for Mesothelioma?
Immunotherapy effectiveness often depends not just on the type of cancer but also on the individual. Most pleural mesothelioma patients do not respond to therapies involving PD-1 or PD-L1.[1]
VISTA, is similar to PD-L1, making it a more promising target for immunotherapy.[2]
VISTA is expressed by more than 90% of mesothelioma cancer cells, making it an excellent target for new therapies. If a drug can block VISTA, the immune system has a better chance of targeting the cancer cells
What Is CA-170?
The new drug recently tested in clinical trials is known as CA-170. Curis, Inc., a biotechnology company that focuses on cancer treatments, is developing and testing the drug. CA-170 is an immune checkpoint inhibitor that targets VISTA.[3]
CA-170 is new and unique in that it is the first therapy tested to target VISTA. Other checkpoint inhibitors that target PD-L1 have already been discovered and tested. Drugs like atezolizumab (Tecentriq) and durvalumab (Imfinzi) are helping the immune system identify and fight cancer.
But CA-170 is the first new therapy that hypothesizes that it can target both PD-L1 and VISTA. The early stages of testing show promising results that this drug can help patients with non-small cell lung cancer. Everyone is interested to see how it works in mesothelioma.
Other VISTA Studies
CA-170 is just one potential drug that could target VISTA and other mesothelioma checkpoint inhibitors. A very recent study done in a lab with cell cultures used other VISTA-targeted antibody-drug conjugates to target VISTA expressed in mesothelioma cells.
The results, although not in human patients, were promising. The researchers found that two new conjugates successfully killed mesothelioma cells and could become targets for novel drugs.[4]
VISTA Clinical Trials
The CA-170, VISTA, and PD-L1 phase I clinical trial is now complete. The trial was conducted in several locations, including San Francisco, California, and Denver, Colorado.[2] Even though this trial is no longer accepting participants, others will continue to open as the compound begins to show safety and efficacy.
Patients with mesothelioma began treatment with the drug in January 2019. The phase I trial’s purpose was to determine the drug’s clinical effects, how it works, and whether it is safe. Mesothelioma patients were given two levels of doses administered every day for two twenty-one-day cycles.
How Can Mesothelioma Patients Get Involved in Clinical Trials?
Clinical trials test the effectiveness and safety of new therapies. When deciding to participate in any clinical trial, it is important to weigh the risk of side effects. Patients must also understand that the outcome of these therapies may not be what they hope.
CA-170 is such a new drug that there are no currently known common side effects. Animal and laboratory studies cleared it as safe enough for human clinical trials; however, this does not mean this drug will be proven safe for human patients.
One clinical trial targeting VISTA was recruiting mesothelioma patients but has now concluded. Phase 1 Study of CI-8993 Anti-VISTA Antibody in Patients With Advanced Solid Tumor Malignancies provided participants with a compound designed to target VISTA in order to evaluate the safety of the treatment.[5]
Although that trial concluded, researchers are always beginning new trials, which may need mesothelioma patients to participate.
If you are interested in learning more about any upcoming clinical trials, talk to your oncologist or other members of your medical team. Mesothelioma patients often qualify for trials because of the aggressive nature of this cancer and how difficult it is to treat.
