Medically reviewed by Prof. Shimon Slavin, MD. Updated: June 2026
Immune checkpoint inhibitors are a class of drugs used in immunotherapy for cancer that remove the brakes from the immune system, allowing a patient’s own T cells to recognize and attack cancer cells more effectively.
At Biotherapy International, checkpoint inhibitor therapy is not used as a standalone treatment. It is applied as part of a sequential immunotherapy protocol and is most effective following oncolytic virus therapy.
Why Checkpoint Inhibitor Therapy Is More Effective After Oncolytic Virus Treatment
Many tumors are classified as “cold” because they do not produce a meaningful immune response. The immune system either fails to recognize the tumor as a threat, or does so insufficiently. As a result, there may be too few anticancer T cells within the tumor to generate an effective immune response.
Oncolytic virus therapy helps address this problem. The virus selectively targets malignant cells and simultaneously triggers immunological processes within the tumor. As cancer cells are destroyed, tumor antigens are released, allowing the immune system to begin recognizing cancer cells more effectively.
As a result, the immune system starts to perceive the tumor as a target for attack. Activated T cells are recruited to the tumor, where they can recognize and destroy cancer cells. In this way, a previously “cold” tumor becomes significantly more visible to the immune system and more responsive to immune attack.
However, many cancers have their own mechanisms to defend against immune attack. Even after T cells recognize cancer cells, those cells can suppress T cell activity through immune checkpoints, including the PD-1/PD-L1 and CTLA-4 pathways. These mechanisms act as immune “brakes”, limiting the ability of T cells to destroy cancer.
This is where checkpoint inhibitors play a critical role. They block the signals that suppress T cell activity, allowing already-activated anticancer T cells to continue attacking cancer cells more effectively.
Unlike using checkpoint inhibitors alone against cold tumors, the sequential combination of oncolytic viruses and checkpoint inhibitors first establishes an anticancer immune response, then amplifies it.
This is why at Biotherapy International, checkpoint inhibitor therapy is typically applied after oncolytic virus treatment. This sequential approach first makes the tumor visible to the immune system, then strengthens the anticancer immune response that has already been initiated.
Learn more about oncolytic virus therapy
Biotherapy’s Approach to Checkpoint Blockade
Standard checkpoint inhibitor protocols typically focus on one or two targets, CTLA-4 and PD-1. At Biotherapy International, Prof. Shimon Slavin’s approach addresses a broader spectrum of immune suppression.
Beyond CTLA-4 and PD-1, significant attention is given to controlling mechanisms that conventional protocols overlook. These include regulatory T cells (Treg), which actively suppress the anticancer immune response; myeloid-derived suppressor cells (MDSC), which block T cell activity in the tumor microenvironment; and tumor-associated macrophages (TAM), which can shield cancer cells from immune attack.
This approach targets multiple mechanisms through which cancer suppresses the immune system simultaneously. The goal is to strengthen the anticancer immune response while reducing the risk of side effects compared to standard high-dose therapy.
After completing the treatment course, the patient’s response is evaluated. Based on the tumor’s response and the patient’s overall clinical status, Prof. Slavin develops the next stage of therapy. This may involve continuing checkpoint inhibitor therapy, transitioning to Cytokine-Mediated Immunotherapy (CMI), or additional cycles of oncolytic virus treatment.
Checkpoint Inhibitor Therapy or CMI?
The choice between checkpoint inhibitor therapy and CMI is determined individually, following an analysis of the diagnosis, residual disease burden, prior treatment history, and the patient’s general condition. After completing oncolytic virus therapy, patients are typically offered one of two immunotherapy pathways.
Checkpoint inhibitor therapy is generally recommended for patients who are able to receive infusion treatment at one of Biotherapy International’s partner clinics. In some cases, therapy may be administered in the patient’s home country in coordination with their treating oncologist.
Cytokine-Mediated Immunotherapy (CMI) is an alternative when checkpoint inhibitor therapy is unavailable, contraindicated, or not the optimal choice. CMI activates the immune system through a different mechanism and may be administered at home under medical supervision.
Despite differences in method, both strategies share the same goal: strengthening the immune response against cancer cells that have been made visible to the immune system by prior oncolytic virus therapy.
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