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VISTA Protein Clinical Trials

Many of the new drugs being tested for treating cancer and mesothelioma specifically are immunotherapy drugs. Targeting and utilizing the immune system to fight cancer cells is increasingly showing promise as a novel type of cancer therapy.

One of the types of clinical trials going on now is the testing of immune checkpoint protein inhibitors, including a new drug known as CA-170. The drug is designed to prevent an interaction between immune system T-cells and cancer cells. This should in turn let the immune cells know that they can attack and destroy the cancer cells. CA-170 is in phase I trials now 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 being attacked by the body’s immune system. The T-cells of the immune system 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.

While healthy cells have the proteins that bind to and disable checkpoints on T-cells, so do cancer cells. One example that has already been targeted by new therapies for cancer treatment is the PD-1 checkpoint protein. 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 have the potential to block the interaction between immune cells and cancer cells so that the T-cells can go ahead and attack the tumor. Another protein, known as VISTA, is similar to PD-L1. And, it has been found to be expressed strongly in mesothelioma cancer cells. This makes it a good 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 being tested in clinical trials now is known as CA-170. It 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 to be 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. There is great promise that it will help mesothelioma patients in these early stages of testing.

VISTA Clinical Trials

The CA-170, VISTA and PD-L1 clinical trials have only begun recently and are in phase I. Participants have been selected, and these include a dedicated cohort of mesothelioma patients as well as those with other types of cancer, like lymphoma. The trial is going on in several locations, including San Francisco, California and Denver, Colorado.

The patients with mesothelioma began getting doses of the drug in January 2019 and the study is expected to carry on until 2020. The purposes of the phase I trial are to determine how the drug works, if it is safe, and what the clinical effects are. Mesothelioma patients will be given two levels of doses that are 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 that is not responding to standard therapy

Some of the criteria that would exclude a patient from this trial include having been a part of any other experimental treatment with in the last four weeks, having undergone radiation therapy within the previous three weeks, and having residual toxicity from chemotherapy. There are also some other health exclusions, such as positive tests for some illnesses and infections, or some types of heart disease.

Getting Involved in Clinical Trials

This is just one example of many clinical trials that are ongoing or recruiting new patients with mesothelioma. Clinical trials are testing not just the effectiveness of new therapies but also the safety. It is important to keep in mind when deciding to participate, that there are risks of side effects and a risk that the outcome will not be as hoped.

CA-170 is such a new drug that there are no known common side effects yet. Animal and laboratory studies cleared it as safe enough to go to clinical trials, but that doesn’t mean it won’t be proven unsafe or harmful in human patients.

If you are interested in learning more about the CA-170 and VISTA trials and wonder if you could qualify to join the 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 of 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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