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VISTA Protein Clinical Trials

Many of the new drugs being tested to treat cancer are immunotherapy drugs. Targeting and utilizing the immune system to fight cancer cells shows increasing promise as a novel type of cancer therapy.

Clinical trials are now ongoing to test immune checkpoint protein inhibitors, including a new drug known as CA-170. CA-170 is designed to prevent interaction between immune system T-cells and cancer cells. This in turn lets immune cells know they can attack and destroy cancer cells. CA-170 is currently in phase I trials and is the first drug to work on checkpoint protein V-domain Ig suppressor of T-cell activation (VISTA).

Immune Checkpoint Proteins and Inhibitors

The VISTA clinical trial is the first to test a drug that targets this specific protein. VISTA is a type of protein that helps cancer cells avoid attack by the body’s immune system. 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.

Although healthy cells have the specific proteins that bind to and disable checkpoints on T-cells, so do cancer cells. 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 to not 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 go ahead and attack the tumor. Another protein, known as VISTA, is similar to PD-L1. PD-L1 expresses strongly in 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.


The new drug currently being tested in clinical trials is known as CA-170. This drug is being developed and tested by Curis, Inc, a biotechnology company that focuses on cancer treatments. CA-170 is an immune checkpoint inhibitor. It targets both PD-L1 and VISTA.

CA-170 is new and unique in that it is the first 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 proving to help boost the immune system to fight cancer. But CA-170 is the first new therapy that does double duty, targeting PD-L1 and VISTA. The early stages of testing show promising results that this drug can help patients with mesothelioma.

VISTA Clinical Trials

The CA-170, VISTA and PD-L1 clinical trials are just getting off the ground. They are currently in phase I. Participants have been selected and include a dedicated cohort of mesothelioma patients. The trial is being conducted in several locations, including San Francisco, California and Denver, Colorado.

Patients with mesothelioma began treatment with the drug in January 2019. The study is expected to carry on until 2020. The purposes of the phase I trial are to determine the clinical effects of the drug, how it works, and if it is safe. Mesothelioma patients will be given two levels of doses administered every day for two 21-day cycles.

Patients who qualify for the current VISTA and CA-170 trials must meet the following criteria:

  • Be 18 years old or older.
  • Have been given a life expectancy of three months or longer.
  • Have adequate organ functioning and bone marrow.
  • Be able to swallow oral medications.
  • Have negative pregnancy test results.
  • Have a measurable disease.
  • Be diagnosed with a cancer that has high VISTA expression, like mesothelioma, or have a cancer not responding to standard therapy.

If a patient has participated in any other experimental treatment within the last four weeks, he or she cannot participate in this clinical trial. Other criteria that would exclude a patient include  having undergone radiation therapy within the previous three weeks and having residual toxicity from chemotherapy. Other health exclusions include positive tests for infection and some types of heart disease.

Getting Involved in Clinical Trials

This is just one example of many ongoing clinical trials recruiting new patients with mesothelioma. Clinical trials not only test for effectiveness, but also test the safety of new therapies. When deciding to participate in any clinical trial, it is important to weigh the risk of side effects. It is also important for patients to 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.

If you are interested in learning more about the CA-170 and VISTA 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.

Page Edited by Dave Foster

Dave has been a mesothelioma Patient Advocate for over 10 years. He consistently attends all major national and international mesothelioma meetings. In doing so, he is able to stay on top of the latest treatments, clinical trials, and research results. He also personally meets with mesothelioma patients and their families and connects them with the best medical specialists and legal representatives available. Connect with Patient Advocate Dave Foster
  1. National Institutes of Health. U.S. National Library of Medicine. (2018, February). A Study of CA-170 (Oral PD-L1, PD-L2 and VISTA Checkpoint Antagonist) in Patients with Advanced Tumors and Lymphoma. Retrieved from
    Retrieved from: https://clinicaltrials.gov/ct2/show/study/NCT02812875
  2. Cision PR Newswire. (2019, January 24). First Mesothelioma Patient Dosed in CA-170 Study. Retrieved from
    Retrieved from: https://www.prnewswire.com/news-releases/first-mesothelioma-patient-dosed-in-ca-170-study-300783484.html

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