Regorafenib in combination with immune checkpoint inhibitors for mismatch repair proficient (pMMR)/microsatellite stable (MSS) colorectal cancer.

Immune checkpoint inhibitors (ICIs) have marked a new era of cancer treatment, showing remarkable efficacy in a wide range of solid malignancies. In colorectal cancer (CRC), however, the therapeutic potential of ICIs is limited to the small group (≈5%) of patients with mismatch repair deficient (dMMR)/high microsatellite instable (MSI-H) tumours, which are characterised by high mutational/neo-antigen burden, and an inflammatory tumour microenvironment with abundant tumour-infiltrating lymphocytes. Over the last few years, research has focused on immuno-modulatory strategies that could overcome the inherent resistance to ICIs that is observed in the vast group (≈95%) of patients with mismatch repair proficient (pMMR)/microsatellite stable (MSS) tumours. Among these, the combination of ICIs with multi-kinase inhibitors has gained traction in preclinical studies and clinical trials. Thanks to their multiple targets and mechanisms of action, generally involving key cancer pathways such as oncogenesis, angiogenesis, metastasis, and tumour immunity, these agents can exert synergistic effects with ICIs, eventually turning inherently cold cancers into hot tumours, that can be efficiently recognised and targeted by an activated immune system. Regorafenib is routinely used for chemorefractory CRC with limited efficacy. Preliminary evidence, however, suggests that this multi-kinase inhibitor could be an optimal combination partner for ICIs. In this review article, we explain the biological rationale underlying the synergism between regorafenib and ICIs, discuss the available clinical data in CRC, and take a glance into future perspectives by presenting ongoing trials and possible research developments in this setting.

Akin Telli T ，Bregni G ，Vanhooren M ，Saude Conde R ，Hendlisz A ，Sclafani F ... -  《-》

Improving the efficiency of immune checkpoint inhibitors for metastatic pMMR/MSS colorectal cancer: Options and strategies.

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment and been extensively used for patients with metastastic colorectal cancer (mCRC), especially those harboring deficient mismatch repair/ microsatellite instability (dMMR/MSI). However, the majority of mCRC are classified as proficient mismatch repair/microsatellite stability(pMMR/MSS) type characterized by a cold immune microenvironment, rendering them generally unresponsive to ICIs. How to improve the efficacy of ICIs for these patients is an important issue to be solved. On the one hand, it is urgent to discover the predictive biomarkers and clinical characteristics associated with effectiveness and expand the subset of pMMR/MSS mCRC patients who benefit from ICIs. Additionally, combined strategies are being explored to modulate the immune microenvironment of pMMR/MSS CRC and facilitate the conversion of cold tumors into hot tumors. In this review, we have focused on the recent advancements in the predictive biomarkers and combination therapeutic strategies with ICIs for pMMR/MSS mCRC.

Yang C ，Zhao L ，Lin Y ，Wang S ，Ye Y ，Shen Z ... -  《-》

How to overcome resistance to immune checkpoint inhibitors in colorectal cancer: From mechanisms to translation.

Immunotherapy, especially with immune checkpoint inhibitors (ICIs), has shown advantages in cancer treatment and is a new hope for patients who have failed multiline therapy. However, in colorectal cancer (CRC), the benefit is limited to a small subset of patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) metastatic CRC (mCRC). In addition, 45% to 60% of dMMR/MSI-H mCRC patients showed primary or acquired resistance to ICIs. This means that these patients may have potential unknown pathways mediating immune escape. Almost all mismatch repair-proficient (pMMR) or microsatellite-stable (MSS) mCRC patients do not benefit from ICIs. In this review, we discuss the mechanisms of action of ICIs and their current status in CRC. We then discuss the mechanisms of primary and acquired resistance to ICIs in CRC. Finally, we discuss promising therapeutic strategies to overcome resistance to ICIs in the clinic.

Wang Q ，Shen X ，Chen G ，Du J ... -  《-》

Immunotherapy efficacy on mismatch repair-deficient colorectal cancer: From bench to bedside.

Colorectal cancers (CRCs) with deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) often have sustained responses to immune checkpoint inhibitors (ICIs) including selective monoclonal antibodies against Program Death 1 (PD-1), Programmed Death Ligand 1(PD-L1), and cytotoxic T lymphocyte associated antigen 4 (CTLA-4). However, a substantial fraction of dMMR CRCs do not respond or ultimately develop resistance to immunotherapy. The majority (~85%) of CRCs are MMR proficient (pMMR) or microsatellite stable (MSS) and lack response to ICIs. Understanding the biology and mechanisms underlying dMMR-associated immunogenicity is urgently needed for improving the therapeutic efficacy of immunotherapy on CRC. Compared to pMMR/MSS CRCs, dMMR/MSI CRCs typically have increased tumor mutational burden (TMB), lower response rate to 5-fluorouracil-based chemotherapy, distinctive immunological features such as high tumor-infiltrating lymphocytes (TILs), and better prognosis. Here, we review the current understanding of the clinical relevance of dMMR/MSI in CRCs, the molecular basis and rationales for targeting dMMR CRC with immunotherapy, and clinical approaches using ICIs as single agents or in combination with other therapies for MSI-H CRCs. Furthermore, we address the potential strategies to sensitize pMMR/MSS CRC to immunotherapy by converting an immunologically "cold" microenvironment into a "hot" one.

Lizardo DY ，Kuang C ，Hao S ，Yu J ，Huang Y ，Zhang L ... -  《-》

Application of immune checkpoint inhibitors in colorectal cancer.

Wang L ，Huang C 《-》