Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) are inhibitory checkpoints that are commonly seen on activated T cells and have been offered as promising targets for the treatment of cancers. Immune checkpoint inhibitors (ICIs)targeting PD-1, including pembrolizumab and nivolumab, and those targeting its ligand PD-L1, including avelumab, atezolizumab, and durvalumab, and two drugs targeting CTLA-4, including ipilimumab and tremelimumab have been approved for the treatment of several cancers and many others are under investigating in advanced trial phases. ICIs increased antitumor T cells’ responses and showed a key role in reducing the acquired immune system tolerance which is overexpressed by cancer and tumor microenvironment. However, 50% of patients could not benefit from ICIs monotherapy. To overcome this, a combination of ipilimumab and nivolumab is frequently investigated as an approach to improve oncological outcomes. Despite promising results for the combination of ipilimumab and nivolumab, safety concerns slowed down the development of such strategies. Herein, we review data concerning the clinical activity and the adverse events of ipilimumab and nivolumab combination therapy, assessing ongoing clinical trials to identify clinical outlines that may support combination therapy as an effective treatment. To the best of our knowledge, this paper is one of the first studies to evaluate the efficacy and safety of ipilimumab and nivolumab combination therapy in several cancers.

Although the ever-increasing number of cancer patients pose substantial challenges worldwide, finding a treatment with the highest response rate and the lowest number of side effects is still undergoing research. Compared to chemotherapy, the relatively low side effects of cancer immunotherapy have provided ample opportunity for immunotherapy to become a promising approach for patients with malignancy. However, the clinical translation of immune-based therapies requires robust anti-tumoral immune responses. Immune checkpoints have substantial roles in the induction of an immunosuppressive tumor microenvironment and tolerance against tumor antigens. Identifying and targeting these inhibitory axes, which can be established between tumor cells and tumor-infiltrating lymphocytes, can facilitate the development of anti-tumoral immune responses. Bispecific T-cell engagers, which can attract lymphocytes to the tumor microenvironment, have also paved the road for immunological-based tumor elimination. The development of CAR-T cells and their gene editing have brought ample opportunity to recognize tumor antigens, independent from immune checkpoints and the major histocompatibility complex (MHC). Indeed, there have been remarkable advances in developing various CAR-T cells to target tumoral cells. Knockout of immune checkpoints via gene editing in CAR-T cells might be designated for a breakthrough for patients with malignancy. In the midst of this fast progress in cancer immunotherapies, there is a need to provide up-to-date information regarding immune checkpoints, bispecific T-cell engagers, and CAR-T cells. Therefore, this review aims to provide recent findings of immune checkpoints, bispecific T-cell engagers, and CAR-T cells in cancer immunotherapy and discuss the pertained clinical trials.

Preclinical studies have indicated that T-cell immunoglobulin and ITIM domain (TIGIT) can substantially attenuate anti-tumoral immune responses. Although multiple clinical studies have evaluated the significance of TIGIT in patients with solid cancers, their results remain inconclusive. Thus, we conducted the current systematic review and meta-analysis based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) to determine its significance in patients with solid cancers. We systematically searched the Web of Science, Embase, PubMed, and Scopus databases to obtain peer-reviewed studies published before September 20, 2020. Our results have shown that increased TIGIT expression has been significantly associated with inferior overall survival (OS) (HR = 1.42, 95% CI: 1.11–1.82, and p-value = 0.01). Besides, the level of tumor-infiltrating TIGIT⁺CD8⁺ T-cells have been remarkably associated inferior OS and relapse-free survival (RFS) of affected patients (HR = 2.17, 95% CI: 1.43–3.29, and p-value < 0.001, and HR = 1.89, 95% CI: 1.36–2.63, and p-value < 0.001, respectively). Also, there is a strong positive association between TIGIT expression with programmed cell death-1 (PD-1) expression in these patients (OR = 1.71, 95% CI: 1.10–2.68, and p-value = 0.02). In summary, increased TIGIT expression and increased infiltration of TIGIT⁺CD8⁺ T-cells can substantially worsen the prognosis of patients with solid cancers. Besides, concerning the observed strong association between TIGIT and PD-1, ongoing clinical trials, and promising preclinical results, PD-1/TIGIT dual blockade can potentially help overcome the immune-resistance state seen following monotherapy with a single immune checkpoint inhibitor in patients with solid cancers.