Microsatellite Stable mCRC Research Articles

Tislelizumab plus cetuximab and irinotecan in refractory microsatellite stable and RAS wild-type metastatic colorectal cancer: a single-arm phase 2 study

Immunotherapy confers little to no benefit in the treatment of microsatellite stable (MSS) metastatic colorectal cancer (mCRC). Mechanistic insights suggested that epidermal growth factor receptor (EGFR) antibody plus irinotecan might augment the tumor immune response in mCRC. Therefore, we conducted a proof-of-concept, single-arm, phase 2 study (ChiCTR identifier: ChiCTR2000035642) of a combination treatment regimen including tislelizumab (anti-PD-1), cetuximab (anti-EGFR) and irinotecan in 33 patients with MSS and RAS wild-type (WT) mCRC who were previously treated with ≥2 lines of therapy. The primary endpoint was met, with a confirmed objective response rate of 33%. As secondary endpoints, the disease control rate was 79%, and the median progression-free survival and overall survival were 7.3 and 17.4 months respectively. Among the 33 patients, 32 (97.0%) had treatment-related adverse events (AEs). Three (9.1%) reported grade ≥ 3 AEs, including rash (n = 1), neutropenia (n = 2). The post-hoc evaluation of dynamic circulating tumor DNA using next generation sequencing and the analysis of peripheral immune proteomics landscape using Olink revealed that lower variant allele frequency (VAF) at baseline, greater reduction in VAF on treatment, and a hot peripheral macroenvironment were associated with the treatment response independently. Our study showed the antitumor activity of tislelizumab, cetuximab, and irinotecan combination with a tolerable safety profile in previously treated MSS and RAS WT mCRC.

Immunotherapy for Microsatellite-Stable Metastatic Colorectal Cancer: Can we close the Gap between Potential and Practice?

This review will explore various strategies to rendering MSS mCRCs susceptible to ICI. Moreover, we will provide an overview of potential biomarkers that may aid to better patient selection, and discuss ongoing efforts in this area of research. Colorectal cancer (CRC) ranks among the top three most common cancers worldwide. While significant advances in treatment strategies have improved the prognosis for patients in the early stages of the disease, treatment options for metastatic CRC (mCRC) remain limited. Although immune checkpoint inhibitors (ICI) have revolutionized the treatment of several malignancies, its efficacy in mCRC is largely confined to patients exhibiting a high microsatellite instability status (MSI-H). However, the vast majority of mCRC patients do not exhibit a MSI-H, but are microsatellite stable (MSS). In these patients ICIs are largely ineffective. So far, ICIs do not play a crucial role in patients with MSS mCRC, despite the promising data for inducing long-term remissions in other tumour entities. For this reason, novel treatment strategies are needed to overcome the primary resistance upon ICI in patients with MSS.

COLUMBIA-1: a randomised study of durvalumab plus oleclumab in combination with chemotherapy and bevacizumab in metastatic microsatellite-stable colorectal cancer

BackgroundTo determine whether the addition of durvalumab (anti-PD-L1) and oleclumab (anti-CD73) to standard-of-care treatment (FOLFOX and bevacizumab) enhances the anti-tumour effect in patients with metastatic colorectal cancer (mCRC).MethodsCOLUMBIA-1 (NCT04068610) was a Phase Ib (feasibility; Part 1)/Phase II (randomised; Part 2) trial in patients with treatment-naïve microsatellite stable mCRC. Patients in Part 2 were randomised to receive standard-of-care (control arm) or standard-of-care plus durvalumab and oleclumab (experimental arm). Primary objectives included safety and efficacy.ResultsSeven patients were enrolled in Part 1 and 52 in Part 2 (n = 26 in each arm). Grade ≥3 treatment-emergent adverse events (TEAE) occurred in 80.8% and 65.4% of patients in the control and experimental arms of Part 2, respectively, with 26.9% and 46.3% experiencing serious TEAEs. The confirmed objective response rate (ORR) was numerically higher in the experimental arm compared with the control arm (61.5% [95% confidence interval (CI), 40.6–79.8] vs 46.2% [95% CI, 26.6–66.6]) but did not meet the statistically significant threshold in either arm.ConclusionThe safety profile of FOLFOX and bevacizumab in combination with durvalumab and oleclumab was manageable; however, the efficacy results do not warrant further development of this combination in patients with microsatellite stable mCRC.RegistrationNCT04068610.

Abstract CT217: First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial

Abstract Metastatic colorectal cancer (mCRC) remains a difficult-to-treat disease. While patients with microsatellite instable metastatic colorectal cancer (mCRC) benefit from immune checkpoint blockade, chemotherapy with targeted therapies remains the only therapeutic option for microsatellite stable (MSS) tumors. The single arm, phase IB/II MEDITREME trial evaluated the safety and efficacy of durvalumab plus tremelimumab combined with mFOLFOX6 chemotherapy in first line, in 57 patients with RAS-mutant unresectable mCRC. Safety was the primary objective of phase IB; no safety issue was observed. The phase II primary objective of efficacy in terms of 3-month PFS in MSS patients was met, with 3-month PFS of 90.7% [95% CI: 79.2-96%]. For secondary objectives, response rate was 64.5%, median PFS was 8.2 months [95% CI: 5.9-8.6] and overall survival was not reached in MSS patients. We observed higher tumor mutational burden and lower genomic instability in responders. Integrated transcriptomic analysis underlined that high immune signature, and low epithelio-mesenchymal transition were associated with better outcome. Immunomonitoring showed induction of neoantigen and NY-ESO1 and TERT blood tumor specific T cell response, associated with better PFS. The combination of durvalumab-tremelimumab with mFOLFOX6 was tolerable with promising clinical activity in MSS mCRC. Clinicaltrials.gov identifier: NCT03202758. Citation Format: Marion Thibaudin, Jean-David Fumet, Emeric Limagne, Léa Hampe, Susy Daumoine, Valentin Derangère, Caroline Laheurte, Olivier Adotevi, Caroline Truntzer, François Ghiringhelli. First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT217.

Abstract 1189: Modulation of the MSS and MSI colorectal cancer immune microenvironment with FOLFOX and FOLFIRI -/+ anti-PD-1 immunotherapy

Abstract Metastatic colorectal cancer (mCRC) is a deadly disease with a five-year survival rate of 14%. Most patients receive 5-FU (F) and folinic acid (FOL) combined with oxaliplatin (OX), irinotecan (IRI), or both (OXIRI). Immune checkpoint inhibitors (ICIs) are effective against microsatellite instable (MSI) tumors, but 95% of mCRC tumors are microsatellite stable (MSS) and ICI-resistant. Though the primary targets of 5-FU, irinotecan, and oxaliplatin are well-understood, their effects on the tumor microenvironment (TME) remain incompletely characterized. Chemotherapy-mediated immune stimulation in MSS CRC has been observed in preclinical models and clinical trials. We hypothesize that combination chemotherapy treatment modulates the immune microenvironment of CRC -/+ ICI, with differences across subtype and treatment regimen. Chemotherapy-dependent changes in cancer cell gene expression, PD-L1 levels, cytokine secretion, and T cell activation were measured using in vitro models of MSS and MSI CRC. A preliminary evaluation of spleen and tumor T cells and dendritic cells (DCs) in murine models of MSS and MSI CRC after immunotherapy -/+ chemotherapy was conducted. CD8+ T cells, DCs, PD-L1, CD69, and GM-CSF expression were measured in clinical specimens of chemotherapy-treated MSS mCRC patients. In MSS CRC, FOX increased GM-CSF and activated CD8+ T cells in vitro and activated splenic CD8+ and CD4+ T cells in vivo. FOX and FIRI suppressed an anti-PD-1-mediated enhancement of type 1 cDCs in the tumor in vivo. FOLFOX was associated with increased tumor CD8+ T cells and decreased GM-CSF in MSS mCRC biopsies. FIRI treatment increased PD-L1 in vitro. FOLFIRI was not associated with increased tumor CD8+ T cells in MSS mCRC biopsies. In MSI CRC, FOX increased tumor CD8+ T cells in vivo. Here, we elucidate novel effects of clinically relevant chemotherapy combinations on the TME in MSS and MSI CRC. These data point to a FOX-specific mechanism by which CD8+ T cell infiltration into MSS mCRC tumors is enhanced, but their activation is halted potentially by GM-CSF suppression and/or type 1 cDC depletion in the TME. These findings contribute to our understanding of the mechanisms of chemotherapy-dependent immune modulation and bring the field closer to harnessing these effects for therapeutic gain. Citation Format: Lindsey Carlsen, Maximilian Pinho-Schwermann, Leiqing Zhang, Andrew Elliott, Kelsey E. Huntington, William J. MacDonald, Brooke Verschleiser, Laura Jinxuan Wu, Wafik S. El-Deiry. Modulation of the MSS and MSI colorectal cancer immune microenvironment with FOLFOX and FOLFIRI -/+ anti-PD-1 immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1189.

Abstract 900: Development and validation of an artificial-intelligence-based pathomics biomarker to predict resistance to first-line treatment in metastatic colorectal cancer

Abstract Background: The backbone chemotherapy of first-line standard of care (SOC) for microsatellite stable (MSS) metastatic colorectal cancer (mCRC) combines 5-Fluorouracil to oxaliplatin and/or irinotecan. There are no biomarkers to predict response, which is complete or long-lasting (CR/LLR) in 20-25% of patients, while 10-15% are primary refractory. The aim of this work is to develop a predictive biomarker, based on digital pathology images, that can help stratify patients according to their risk of resistance. Methods: We trained a supervised bag-of-words artificial intelligence (AI)-based model on a cohort of response outliers mCRC patients classified as “really sensitive” (RS) if they achieved CR or LLR >10 months to any SOC, or “really resistant” (RR) if progression occurred at first disease reassessment. Whole-slide Imaging (WSI) of the resected primary tumors were tiled into patches of 224 × 224 pixel (0.5μm/pixel). First-order and texture features were subsequently extracted from all tumoral tiles and grouped into homogenous clusters through a k-means algorithm (k=6). For each patient, the percentage of tiles belonging to each tiles’ cluster was computed to represent new features (called bag of words) with whom different machine learning classifiers were trained. Main clinicopathological features were matched to treatment response by Fisher’s exact test. Results: To date, we analyzed 82 response outlier patients, of whom 35 were classified as RS and 46 RR. Of them, patients identified at Italian centers were used as construction cohort (N=47; 27 RR and 20 RS) and those identified at Spanish centers were used a validation cohort (N=35; 19 RR and 16 RS). The best result was obtained using a stepwise logistic regression, reaching a negative predictive value (NPV) of 90% (18/20; 95% CI=70-97%) and 71% (10/14; 95% CI=49-87%), in the construction and validation sets. No standard clinicopathological features (including stage, RAS/BRAF status, histology and sidedness) was associated with the chance of being RR. Conclusions: We demonstrated that a pathomics signature has the potential to predict resistance to SOC in MSS mCRC. Further validation of these preliminary findings on a larger cohort of response outlier patients is ongoing. Citation Format: Luca Lazzari, Gianluca Mauri, Valentina Giannini, Debora Cafaro, Giulia Nicoletti, Caterina Marchiò, Andrea Sartore-Bianchi, Federica Marmorino, Maria Nieva Munoz, Nadia Saoudi Gonzalez, Alberto Puccini, Chiara Cremolini, Clara Montagut, Elena Elez, Stefania Sciallero, Enrico Berrino, Martina Carullo, Pietro Paolo Vitiello, Maria Costanza Aquilano, Martina Di Como, Emanuela Bonoldi, Salvatore Siena, Alberto Bardelli, Daniele Regge, Silvia Marsoni. Development and validation of an artificial-intelligence-based pathomics biomarker to predict resistance to first-line treatment in metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 900.

Abstract 2505: Immune dynamics and response predictors to regorafenib, ipilimumab, and nivolumab (RIN) treatment in chemotherapy resistant microsatellite stable (MSS) metastatic colorectal cancer (mCRC)

Abstract Background: In our previous study, RIN therapy in MSS mCRC patients, excluding those with liver metastases, yielded a notable 36.4% objective response rate. RIN treatment was observed to remodel the local tumor microenvironment by enhancing immune infiltration, especially in responders. Systemic immunity, as assessed through peripheral blood analysis, showed that responders had lower baseline immune activity, which increased markedly post-treatment. Patients with liver metastases demonstrated a reduced CD4/CD8 T cell ratio, indicative of immunosenescence. Methods: Building on our prior research, we analyzed blood samples from 29 chemotherapy-resistant MSS mCRC patients undergoing RIN therapy, collected at baseline and after two consecutive treatment cycles. Two 28-marker spectral flow cytometry panels were used to assess immune senescence and cytokine production in lymphocytes. Additionally, T cell receptor repertoires and transcriptional profiles were analyzed using RNA sequencing from sorted non-naïve T cells. Results: The study unveiled distinct immunological profiles in MSS mCRC patient responders vs non-responders to RIN treatment. Responders demonstrated increased numbers of newly expanding CD8 T cell clones on-treatment, indicative of an active immune responses. In contrast, non-responders displayed evidence of increased DNA damage in circulating lymphocytes (T, B, and NK cells), as marked by elevated γ-H2AX levels. We also identified divergent cytokine production profiles patterns at baseline: T cells in non-responders demonstrated increased capacity for production of IL-2, IL-10, IL-4/-13, and IL-22, while production of IFN-γ in both T cells and NK cells correlated with improved outcomes. Notably, patients with liver metastases exhibited greater frequencies of senescent T cells, characterized by increased expression of senescence markers (SA-βGal, CD57, Granzyme B/K) and a reduction in CD27 and CD28 in CD4 T cells, along with an accumulation of terminally differentiated CD8 T cells both pre- and post-treatment. Additionally, RNA sequencing revealed an upregulation of FOXO1 related genes in non-naive T cells of responder patients, which is consistent with its important role for this pathway in attenuating senescence and maintenance of stem-like properties in T cells. Conclusions: The effectiveness of RIN therapy is associated with baseline functional potential of circulating T cells and an on-treatment expansion of T cell clonotypes. Pre-existing and persistent features of senescence and DNA damage in circulating lymphocytes may be a major barrier to RIN treatment efficacy in MSS colorectal cancer and should be validated further in future studies. Citation Format: Jian Ye, Chongkai Wang, Colt Egelston, Weihua Guo, Peter Lee, Marwan Fakih. Immune dynamics and response predictors to regorafenib, ipilimumab, and nivolumab (RIN) treatment in chemotherapy resistant microsatellite stable (MSS) metastatic colorectal cancer (mCRC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2505.

Identification of beneficial populations for targeted-immunotherapy combinations: tailoring later-line care for patients with pMMR/MSS metastatic colorectal cancer.

This study explores the benefits of targeted-immunotherapy combination in third-line or beyond treatment for microsatellite stable (MSS) metastatic colorectal cancer (mCRC) in a real-world setting. Patients with MSS mCRC who were treated with either a targeted-immunotherapy combination or targeted therapy alone in the third-line or beyond setting at our hospital from August 2018 to August 2022 were included in the study. Inclusion criteria comprised patients treated with targeted therapy alone or in combination with immunotherapy. Effectiveness was compared between treatments, and patients with the potential to benefit from targeted-immunotherapy combination were identified. Among 71 patients, 31 received targeted therapies alone (TT group) and 40 received a combination of targeted therapy and immunotherapy (TI group). The TI group had higher objective response rates (20% vs 3.2%) and disease control rates (82.5% vs 58.1%). The median progression-free survival was significantly better in the TI group (4.6 vs 4.1 months, P = 0.027). Liver metastasis was associated with poor prognosis, while patients with only lung metastases had the longest median progression-free survival of 12.3 months with combination therapy. The study indicates that targeted-immunotherapy combination offers more benefits than targeted therapy alone for MSS mCRC in the third-line or beyond setting.

Efficacy, safety, and predictors of fruquintinib plus anti-programmed death receptor-1 (PD-1) antibody in refractory microsatellite stable metastatic colorectal cancer in a real-world setting: a retrospective cohort study.

Patients with microsatellite stable (MSS) advanced colorectal cancer (CRC) have few alternatives for salvage therapy and a large unmet clinical need. Preclinical studies demonstrate that fruquintinib combined with anti-programmed death protein 1 (PD-1) has a synergistic anti-tumor effect. But a few phase 2 clinical studies show inconsistent efficacy of this combination therapy in CRC. The aim of this study was to investigate the efficacy, safety, and predictors of fruquintinib plus PD-1 antibodies in refractory MSS metastatic CRC (mCRC) in a real-world setting. We performed a retrospective single-center analysis to assess the outcomes of patients with MSS mCRC who were treated with fruquintinib plus anti-PD-1 antibodies subsequent to the failure of standard therapies at the Hunan Cancer Hospital. The overall survival (OS), progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), and toxicity were reviewed and evaluated. The primary endpoint was OS. The impact on OS and PFS was examined using the Cox regression model. Between 1 January 2019 and 30 June 2022, we enrolled 70 eligible patients. The median follow-up was 17.2 months (range, 5.3-32.9 months). The median OS (mOS) and median PFS (mPFS) were 19.48 and 5.5 months respectively. The ORR was 11.43% and the DCR was 84.29%. Multivariate Cox regression analysis reveals liver metastasis (LM) without local treatment was a risk factor for OS [hazard ratio (HR) =5.31, P=0.0184], whereas that with local treatment (HR =2.19, P=0.263) was not. The most common adverse events were hand-foot syndrome (37.14%), hypertension (34.29%), mucositis oral (32.86%). No serious adverse effects or adverse effect-related deaths were reported. There were no instances of severe adverse effects or deaths related to adverse effects reported. Our study indicates that the combination of fruquintinib and anti-PD-1 antibodies can improve the OS and PFS with a tolerable toxicity profile for Chinese patients with refractory MSS mCRC. LM without local therapy is a negative prognostic factor for OS, but those with local treatment can significantly prolong survival. We require additional well-structured, prospective, and extensive studies to confirm and validate these findings.

Fecal microbiota transplantation plus tislelizumab and fruquintinib in refractory microsatellite stable metastatic colorectal cancer: an open-label, single-arm, phase II trial (RENMIN-215)

Immunotherapy has revolutionized the treatment of cancer. However, microsatellite stable (MSS) metastatic colorectal cancer (mCRC) shows a low response to PD-1 inhibitors. Antiangiogenic therapy can enhance anti-PD-1 efficacy, but it still cannot meet clinical needs. Increasing evidence supported a close relationship between gut microbiome and anti-PD-1 efficacy. This study aimed to explore the efficacy and safety of the combination of fecal microbiota transplantation (FMT) and tislelizumab and fruquintinib in refractory MSS mCRC. In the phase II trial, MSS mCRC patients were administered FMT plus tislelizumab and fruquintinib as a third-line or above treatment. The primary endpoint was progression-free survival (PFS). Secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), duration of response (DoR), clinical benefit rate (CBR), safety and quality of life. Feces and peripheral blood were collected for exploratory biomarker analysis. This study is registered with Chictr.org.cn, identifier ChiCTR2100046768. From May 10, 2021 to January 17, 2022, 20 patients were enrolled. Median follow-up was 13.7 months. Median PFS was 9.6 months (95% CI 4.1-15.1). Median OS was 13.7 months (95% CI 9.3-17.7). Median DoR was 8.1 months (95% CI 1.7-10.6). ORR was 20% (95% CI 5.7-43.7). DCR was 95% (95% CI 75.1-99.9). CBR was 60% (95% CI 36.1-80.9). Nineteen patients (95%) experienced at least one treatment-related adverse event (TRAE). Six patients (30%) had grade 3-4 TRAEs, with the most common being albuminuria (10%), urine occult blood (10%), fecal occult blood (10%), hypertension (5%), hyperglycemia (5%), liver dysfunction (5%), hand-foot skin reaction (5%), and hypothyroidism (5%). No treatment-related deaths occurred. Responders had a high-abundance of Proteobacteria and Lachnospiraceae family and a low-abundance of Actinobacteriota and Bifidobacterium. The treatment did not change the structure of peripheral blood TCR repertoire. However, the expanded TCRs exhibited the characteristics of antigen-driven responses in responders. FMT plus tislelizumab and fruquintinib as third-line or above treatment showed improved survival and manageable safety in refractory MSS mCRC, suggesting a valuable new treatment option for this patient population. This study was supported by the National Natural Science Foundation of China (82102954 to Wensi Zhao) and the Special Project of Central Government for Local Science and Technology Development of Hubei Province (ZYYD2020000169 to Yongshun Chen).

Immunocheckpoint Inhibitors in Microsatellite-Stable or Proficient Mismatch Repair Metastatic Colorectal Cancer: Are We Entering a New Era?

Colorectal cancer (CRC) is the third most frequent cancer and the second leading cause of cancer-related deaths in Europe. About 5% of metastatic CRC (mCRC) are characterized by high microsatellite instability (MSI) due to a deficient DNA mismatch repair (dMMR), and this condition has been related to a high sensitivity to immunotherapy, in particular to the Immune Checkpoint Inhibitors (ICIs). In fact, in MSI-H or dMMR mCRC, treatment with ICIs induced remarkable response rates and prolonged survival. However, the majority of mCRC cases are mismatch-repair-proficient (pMMR) and microsatellite-stable (MSS), and unfortunately these conditions involve resistance to ICIs. This review aims to provide an overview of the strategies implemented to overcome ICI resistance and/or define subgroups of patients with MSS or dMMR mCRC who may benefit from immunotherapy.

Refractory microsatellite stable metastatic colorectal cancer with ERBB2/ERBB3 mutation may be preferred population for regorafenib plus PD-1 inhibitor therapy: a real-world study.

Microsatellite stable (MSS) colorectal cancer (CRC) has been referred to as the "cold tumor" because of almost no response to anti-programmed death-1 (PD-1) antibody. A recent REGONIVO trial showed that regorafenib plus nivolumab had an encouraging efficacy in MSS metastatic CRC (mCRC). However, only a small subset of patients may benefit from the combination therapy. We aim to evaluate the efficacy and safety data of immune checkpoint inhibitors combined with regorafenib in refractory MSS mCRC and to discover biomarkers that can effectively stratify the beneficial patient population. We retrospectively analyzed patients with MSS mCRC who received regorafenib combined with anti-PD-1 antibody therapy. The objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and status of gene mutation were reviewed and evaluated. Twenty-one patients received combination treatment. At a median treatment duration of 4 months, one patient achieved complete response, three patients achieved partial response, and two patients achieved stable disease as the best response. The ORR and DCR were 19% and 28.5% in the overall population, respectively. The median PFS was 4 months, and the median OS was 25 months. Only erbb2 receptor tyrosine kinase 2/erbb3 receptor tyrosine kinase 3 (ERBB2/ERBB3) mutation status was confirmed to be a potential predictive factor for effective treatment. In patients with ERBB2/ERBB3 mutation, ORR, DCR, and PFS exhibited significant improvements in comparison with that in wild-type patients. Grade 3 or higher treatment-related adverse events occurred in three patients (14.3%). Regorafenib in combination with PD-1 inhibitor provides a feasible treatment regimen for refractory MSS mCRC with tolerated toxicity. Patients with ERBB2/ERBB3 mutation may be the preferred population for this combination regimen.

Sintilimab plus bevacizumab, oxaliplatin and capecitabine as first-line therapy in RAS-mutant, microsatellite stable, unresectable metastatic colorectal cancer: an open-label, single-arm, phase II trial

Microsatellite stable (MSS) and RAS-mutant metastatic colorectal cancer (mCRC) patients are characterized by an immunosuppressive microenvironment and a low response rate to immunotherapy. Chemotherapy and anti-angiogenesis therapy have been reported to potentially promote immunotherapy response. This study aims to assess the preliminary anti-tumor activity and safety of sintilimab plus bevacizumab, oxaliplatin and capecitabine as a treatment option for patients with RAS-mutant MSS mCRC. This study was an open-label, single-arm, phase II trial in China. Patients with unresectable, RAS-mutant and MSS metastatic colorectal adenocarcinoma received treatment by intravenous sintilimab (200mg, day 1) plus bevacizumab (7.5mg/kg, day 1), oxaliplatin (135mg/m2, day 1) and oral capecitabine (1g/m2, day 1-14) in each 21-day cycle. The primary endpoints included objective response rate (ORR) and adverse events. Biomarker analysis was performed to identify potential predictors of good response to treatment. This study is registered with ClinicalTrials.gov, number NCT04194359. Between April 2021 and December 2021, 25 patients were enrolled. Two (8%) patients showed complete response (CR), 19 (76%) had partial response (PR) and 4 (16%) presented with stable disease. ORR reached 84% (95% CI, 63.9-95.5) and the disease control rate was 100% (95% CI, 86.3-100). The median progression-free survival (PFS) was 18.2 months for the full analysis set. The most common treatment-related adverse events (TRAEs) in all grades were anemia (21/25, 84%), neutropenia (20/25, 80%), and hand-foot syndrome (14/25, 56%). The most frequent grade 3 or 4 TRAEs were neutropenia (3/25, 12%) and increased alanine transaminase (2/25, 8%). No grade 5 adverse events occurred. In the exploration of biomarkers, 5 patients could be characterized as TTN/OBSCN "double-hit" after treatment, and the copy number variants burden was significantly decreased in tumor tissues after treatment compared with the baseline. Nanostring panel RNA sequencing analysis indicated a better tumor immune microenvironment cell infiltration in CR/PR patients compared with non-CR/PR patients as well as the PFS-long (≥12.5 months) group compared with the PFS-short group. Combination treatment with sintilimab plus bevacizumab, oxaliplatin and capecitabine as first-line treatment demonstrated a promising antitumor activity and a manageable safety profile in RAS-mutant, MSS and unresectable mCRC. Exploratory biomarker assessment analysis showed that some RAS-mutant and MSS patients changed into "immune-hot" subtype after the treatment. This study was supported by the Key R&D Program of Zhejiang Province (2021C03125 to Ying Yuan), the National Natural Science Foundation of China (81872481 to Ying Yuan, 82072624 to Kefeng Ding), the Fundamental Research Funds for the Central Universities (No. 226-2022-00009 to Kefeng Ding), and the Zhejiang Provincial Natural Science Foundation of China (No. LY22H160024 to Hanguang Hu).

Sintilimab plus bevacizumab and CapeOx (BBCAPX) on first-line treatment in patients with RAS mutant, microsatellite stable, metastatic colorectal cancer: study protocol of a randomized, open-label, multicentric study

BackgroundRat sarcoma viral oncogene homolog (RAS) gene mutation is a common molecular event in colorectal cancer (CRC). The prognosis of mCRC (metastatic colorectal cancer) patients with RAS mutation is poor and capecitabine and oxaliplatin (CapeOx) plus bevacizumab has shown to be one of the standard therapeutic regimens as first line for these patients with objective response rate (ORR) of ~ 50% and median progression-free survival (mPFS) of 8–9 months. Immunotherapy, especially anti-programmed death 1 (PD-1) monoclonal antibody has demonstrated ground-breaking results in deficient mismatch repair (dMMR) / microsatellite instability-high (MSI-H) mCRC patients. However, the response rate of in microsatellite stable (MSS) patients is extremely low. In addition, preclinical studies have demonstrated that anti-Vascular endothelial growth factor (VEGF) agents, such as bevacizumab, can induce tumor vascular normalization and enhance antitumor immunity. Previous study indicated the combination of chemotherapy, anti-VEGF agents (bevacizumab) with immune checkpoint inhibitors may have promising clinical activity in RAS mutant, MSS refractory mCRC patients. Based on these evidences, we will explore the combination of CapeOx with bevacizumab and sintilimab (anti-PD-1 monoclonal antibody) in RAS mutant, MSS mCRC patients as first-line therapy.MethodsThis is a randomized, open-label, multicentric clinical trial. In the sintilimab arm, patients will receive sintilimab in combination with CapeOx and bevacizumab. In the control arm, patients will receive CapeOx and bevacizumab. This trial will recruit 494 patients from 20 centers and randomly (1:1) disseminated into two groups. The primary endpoint is the PFS. The secondary endpoints include overall survival, safety, ORR, and disease control rate.DiscussionThis study may provide new ideas for optimizing oncology treatment planning for RAS mutant, MSS mCRC patients in the first-line set.Trial registrationThis study is short for BBCAPX and has been registered at clinicaltrials.gov registry with identifier NCT05171660.

The role of immunotherapy in microsatellites stable metastatic colorectal cancer: state of the art and future perspectives.

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide, despite several advances has been achieved in last decades. Few prognostic and predictive biomarkers guide therapeutic choice in metastatic CRC (mCRC), among which DNA mismatch repair deficiency and/or microsatellite instability (dMMR/MSI) holds a crucial role. Tumors characterized by dMMR/MSI benefit from immune checkpoint inhibitors. However, most of the mCRC patients (around 95%) are microsatellite stable (MSS), thereby intrinsically resistant to immunotherapy. This represents a clear unmet need for more effective treatments in this population of patients. In this review, we aim to analyze immune-resistance mechanisms and therapeutic strategies to overcome them, such as combinations of immunotherapy and chemotherapy, radiotherapy or target therapies specifically in MSS mCRC. We also explored both available and potential biomarkers that may better select MSS mCRC patients for immunotherapy. Lastly, we provide a brief overview on future perspectives in this field, such as the gut microbiome and its potential role as immunomodulator.

Abstract 6676: Exploratory biomarker analyses in phase 1 study of regorafenib, ipilimumab, and nivolumab (RIN) in chemotherapy resistant microsatellite stable (MSS) metastatic colorectal cancer (mCRC)

Abstract Background: We recently reported an objective response rate of 36.4% in a phase I trial of RIN in MSS mCRC patients without liver metastases, while no response was noted in patients with liver metastases. Here we characterized kinetics in local and systemic immune responses associated with clinical outcomes, liver metastasis, and immune related toxicity during RIN treatment. Methods: Patients with chemotherapy-resistant MSS mCRC received RIN at (R) at 80 mg QD x 21 days in 4-week(w) cycle, (I) at 1mg/kg Q6w and (N) at 240 mg Q 2w (n=29). Needle biopsies were collected at baseline (n=8) and 4 weeks (n=6) after treatment. Blood samples were collected at baseline (n=29), 4 weeks (n=29) and 8 weeks (n=25) after treatment. Alterations in the tumor microenvironment (TME) were characterized by RNA sequencing. We analyzed the immune cell composition and activities in the blood, including 90 subpopulations of leukocytes and 29 activation/suppression/proliferation markers, with high-dimensional spectral flow cytometry. Results: The clinical responses are positively correlated with the induction of local anti-tumor immunity. Patients with better clinical outcomes exhibited higher levels of lymphocyte infiltration, chemokine production, and antigen-presentation potential in the local TME following one cycle of RIN treatment. The duration of progression-free survival (PFS) was correlated with a higher baseline STING signal in the TME. In the peripheral blood, the responders have more circulating CD4 T cells, B cells, and cDC1, while expressing lower immune activation markers, especially in T cells with type 1 immunity at baseline. At 4 weeks, immune activation and proliferation markers were higher in responders than non-responders. Interestingly, immune effectors (non-Tregs, CD45RA− CD8 T cells, NKT cells, and M1 monocytes) in the blood were proportionally reduced in responders at 4 weeks, coincident with their enrichment in the local TME. We also compared peripheral immune signatures between patients with and without liver metastases, liver metastases (n=7) were associated with a significantly lower ratio of CD4/CD8 T cells in the blood, a phenomenon of immunosenescence, both at baseline and after RIN treatment. Lastly, the occurrence of immune-related toxicities was closely correlated with the induction of immune activities in both acellular and cellular components in the circulation. Conclusions: Clinical benefit of RIN was correlated to more robust immune activation of the TME and peripheral blood following one cycle of treatment. A higher baseline STING signal in the TME was associated with longer PFS. Liver metastasis was associated with a lower ratio of peripheral CD4/CD8 T cells which may contribute to the resistance to immunotherapy in those patients. Citation Format: Jian Ye, Chongkai Wang, Colt Egelston, Weihua Guo, Peter P. Lee, Marwan Fakih. Exploratory biomarker analyses in phase 1 study of regorafenib, ipilimumab, and nivolumab (RIN) in chemotherapy resistant microsatellite stable (MSS) metastatic colorectal cancer (mCRC). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6676.

Abstract 4406: Impact of site of metastases on response to immunotherapy in microsatellite stable (MSS) metastatic colorectal cancer (mCRC)

Abstract Background: We have noted that responses to the combinations of regorafenib and nivolumab (REGONIVO) or regorafenib ipilimumab nivolumab (RIN) were limited to MSS mCRC without liver involvement. We sought to delineate the impact of non-liver metastatic sites on the response to these combinations. Methods: We performed a single center retrospective analysis of MSS mCRC receiving REGONIVO or RIN. To isolate the impact of immunotherapy on metastatic disease sites, we performed a 2-month (mo) analysis of organ specific response using organ specific RECIST assessment. Results: 96 patients (Pts) (39 RIN and 57 REGONIVO) were evaluated. Overall response rate (ORR), median progression free survival (PFS), and median overall survival (OS) were 0%, 2 mo, and 7 mo in pts with liver metastatic (LM) disease (n = 33). We focused on the impact of other metastatic disease site on OS and PFS within the non-LM group to exclude liver as a confounding variable (n=63). Pts with lung-only mCRC had the best prognosis with an ORR, median PFS, and median OS of 56%, 13 mo, and unreached at 24 mo. Pts with peritoneal mCRC fared poorly (ORR 0%, median PFS= 1.5 mo, median OS =12 mo). A high ORR (75%) was noted in a small cohort of 4 pts with lymph node only disease. However, concurrent LN with lung only mCRC diminished efficacy outcomes. Differences in PFS and OS by organ involvement were independent of treatment (REGONIVO or RIN) based on estimates from Cox proportional hazard model. 2-mo response rates by metastatic sites are shown in Table 1. Responses at the 2-mo mark in the 96 pt cohort occurred in lung, LN, and soft tissue metastases but were most robust in lung only metastatic disease. Conclusions: Responses to the combination REGONIVO or RIN are most robust in lung-only metastatic disease and appear to be modest in the setting of LN and soft tissue involvement. Liver and peritoneal disease was associated with lack of benefit from these combinations. Table 1. 2-month Response Rates by Site of Metastatic Disease Sites of mCRC Number of Pts PD SD PR+CR Lung 72 33 (45.8%) 21 (29.2%) 18 (25.0%) Lung response in the setting of liver mets 27 18 (66.7%) 7 (25.9%) 2 (7.4%) Lung response without liver mets 45 15 (33.3%) 14 (31.1%) 16 (35.6%) Lung response in lung only metastatic disease 16 3 (18.8%) 4 (25.0%) 9 (56.2) Liver 33 31 (93.9%) 2 (6.1%) 0 (0%) Lymph Node (LN) 49 32 (65.3%) 12 (24.5%) 5 (10.2%) LN in the setting of liver mets 22 20 (90.9%) 2 (9.1%) 0 (0%) LN in the setting of no liver 30 14 (46.7%) 11 (36.7%) 5 (16.6%) LN only 4 1 (25%) 0 (0%) 3 (75%) Peritoneal 15 14 (93.3%) 1 (6.7%) 0 (0%) Soft tissue 30 11 (39.3%) 15 (53.6%) 2 (7.1%) Bone 8 4 (50%) 4 (50%) 0 (0%) Brain 1 1 (100%) 0 (0%) 0 (0%) Spleen + Adrenal 5 4 (80%) 1 (20%) 0 (0%) Citation Format: Marwan Fakih, Jaideep Sandhu, Xiaochen Li, Chongkai Wang. Impact of site of metastases on response to immunotherapy in microsatellite stable (MSS) metastatic colorectal cancer (mCRC). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4406.

Trial in progress: A phase II, multicenter, open-label study of PolyPEPI1018 in combination with atezolizumab in participants with relapsed or refractory microsatellite-stable metastatic colorectal (MSS mCRC) cancer (Oberto-301).

TPS283 Background: Colorectal cancer (CRC) is among the top three most commonly occurring cancers globally. CRC is now routinely classified as MSI-high (MSI-H) or microsatellite-stable (MSS) based on the detection or absence of molecular markers of genetic instability, respectively. The efficacy of checkpoint inhibitor immunotherapy in MSI-H CRC has not been replicated in MSS CRC. Therefore, additional interventions are needed to convert immunologically “cold” MSS CRC to “hot” tumors resembling MSI-H tumors. PolyPEPI1018 is an off-the-shelf, multi-peptide vaccine containing 12 immunogenic epitopes derived from 7 cancer testis antigens (CTAs) frequently expressed in patients with CRC. PolyPEPI1018 successfully restored and boosted pre-existing anticancer immunity of MSS mCRC subjects and triggered recruitment and infiltration of cytotoxic T cells into the tumor. In first line metastatic MSS CRC, PolyPEPI1018 in combination with fluoropyrimidine/bevacizumab vaccine was safe and demonstrated early evidence of clinical activity. Therefore, we hypothesized that the combination of PolyPEPI1018 and atezolizumab will convert a “cold” MSS mCRC to a “hot” tumor and may increase the likelihood of inducing favorable antitumor immunity and subsequent clinical benefit. Methods: The study is a phase 2, multicenter, single-arm clinical trial of PolyPEPI1018 vaccine (1.2 mg, sc, every 3 weeks) and atezolizumab (1200 mg, iv, every 3 weeks) for patients with advanced or metastatic MSS CRC who have progressed on 2 or 3 lines of prior standard regimens. 28 patients will be enrolled at 3 US sites with a primary objective to assess the safety and tolerability of multiple doses of PolyPEPI1018 in combination with atezolizumab. Secondary endpoints include objective response rate (ORR) assessed by RECIST v1.1, vaccine induced immunological response rate (IRR), progression-free survival and overall survival. Correlative aims include assessing blood and tissue biomarkers (PD-L1, Immunoscore®IC, ctDNA, clinical tumor markers) for association with clinical benefit. An exploratory study is being conducted for co-development of a companion diagnostic based on HLA-genotype and computational personal epitope (PEPI) prediction test. A Simon 2-stage design will be used for the initial assessment of ORR. If pre-specified activity goal for the first stage of accrual (n = 18) is met, additional 10 participants will be enrolled to the second stage. A formal review of safety will be performed after the initial 6 participants have received at least 2 cycles of study therapy. The study is open with 10 patients enrolled at time of submission. Clinical trial information: NCT05243862 .

Regorafenib, ipilimumab, and nivolumab (RIN) in chemotherapy-resistant MSS metastatic colorectal cancer (mCRC).

110 Background: We recently reported on the activity of regorafenib (R), ipilimumab (I) and nivolumab (N) (RIN) in microsatellite stable (MSS) mCRC. Here, we describe mature efficacy data at the recommended phase 2 dose (RP2D) and the results of a new escalation (ESC) cohort of 40 mg to 80 mg regorafenib. Methods: Patients (pts) with chemotherapy resistant MSS mCRC received RIN at (R) at 80 mg QD x 21 days in 4-week(w) cycle, (I) at 1mg/kg Q6w and (N) at 240 mg Q 2w. If no more than 1 dose limiting toxicity (DLT) was noted in 6 evaluable pts, an expansion cohort was assessed at that dose level. Following RP2D establishment and given the increased rate of transient skin toxicity on cycle (C) 1, the protocol was amended to explore a 10-pt cohort with 40 mg/day (R) on C1 with escalation to 80mg/day on C2+. Results: 39 pts with chemotherapy resistant MSS mCRC were enrolled. 29 pts enrolled on the RP2D and 10 pts at the amended 40 to 80mg cohort. At the RP2D and ESC cohorts, 7 and 3 pts had liver metastases (LM), respectively. No significant clinical activity was noted in LM pts (ORR = 0%, median progression free survival (mPFS) = 2 months (mo)). Overall response rate (ORR), disease control rate (DCR), mPFS, median overall survival (OS) in the 22 pts with non-LM (NLM) pts in the RP2D and ESC cohorts were 36% (41% iRECIST), 68% (82% iRECIST), 5.0 mo (6.0 mo iRECIST), > 22 mo (not reached) and 0%, 57% (71.4% iRECIST), 4 mo (4 mo iRECIST), and > 10 mo (not reached). 6/22 NLM at the P2RD remain without PD at 22 mo and beyond. All 7 NLM pts in the ESC cohort progressed by 7 mo from enrollment. ctDNA (Guardant 360) assays were available at baseline and at 4-6 weeks in 23/39 pts. Early ctDNA clearance was confirmed in 8/17 pts at RP2D (4PR and 4SD > 6 mo; mPFS = 11 mo) and 2/6 pts at the ESC cohort (PFS 4.5 mo and 7mo). An ESC vs. RP2D strategy mitigated skin rash (10% vs. 38% grade (G) 3; 20% vs. 66% any G). Other immune related ≥ G3 toxicities are summarized. Conclusions: RIN (80/1/240) has substantial activity in MSS NLM mCRC patients. An ESC strategy of 40/1/240 to 80/1/240 on C2+ reduced transient skin rash and other immune-mediated toxicities but was associated with less favorable clinical outcome. These data suggest that a starting R dose of 80 mg is important in priming the immune response to RIN. The RP2D of 80/1/240 mg is recommended for further investigation in NLM mCRC. Clinical trial information: NCT04362839 . [Table: see text]

Effect of immunotherapy on the survival outcomes in tumor mutational burden-high (TMB-H) microsatellite stable (MSS) metastatic colorectal cancer (mCRC): A single-institution experience.

239 Background: The benefit of immunotherapy for patients with mCRC with high tumor mutational burden (TMB-H) has been widely debated. In 2020, the FDA approved the use of pembrolizumab for the treatment of patients with TMB-H unresectable or metastatic solid tumors, with TMB-H defined as ≥10 mutations/Mb on a commercial tissue-based assay, based on KEYNOTE 158 results. However, the clinical value of applying this universal cut off to mCRC needs further investigation. Methods: We queried Moffitt Cancer Center (MCC) databases for patients with MSS mCRC, harboring TMB-H (tested with tissue and/or liquid biopsies) who received immunotherapy between January 2018 and December 2021. Patients with incomplete records were excluded. Clinical data were extracted by trained staff from electronic medical records. Objective response rate was measured by using clinical assessment from chart review. Results: We identified 40 patients with TMB-H MSS mCRC 13 of whom received immune checkpoint inhibitor therapy. Female patients represented 31% (n=4) of the 13 treated patients. Median age for the patients was 60 years (range 34-71. Thirty-eight percent (n=5) of the primary tumors originated in the right side. Thirty-one percent (n=4) presented with stage 4 CRC at diagnosis. Histopathology was adenocarcinoma in 92% (n=12) and one had neuroendocrine differentiation. Tumors were well-differentiated 8% (n=1), moderately differentiated 46% (n=6), or poorly differentiated 23% (n=3). Four patients (31%) had POLE/ POLD-1 mutations. The objective response rate (ORR) was 31% (4/13) with responses limited to tumors only with POLE/ POLD-1 mutations (100%, 4/4). The median progression free survival (mPFS) was 3.8 months for the overall cohort and 28.5 months for patients with POLE/POLD-1 mutated tumors. Agent specific analysis showed mPFS for patients treated with pembrolizumab was 3.5 months (mean 5.2; range 0.6-15.7), and 3.4 months (mean 12.1; range 0.5-12.1) for patients treated with nivolumab. Five patients received immunotherapy in combination with regorafenib. The mPFS for these patients was 3.4 months (mean 3.8; range 0.5-8.0). Of five patients with TMB>30 (38%), 4 (80%) had POLE/POLD-1 mutated tumors. One case without POLE/POLD-1 mutations, but with a TMB>30 did not experience any response. Conclusions: Although TMB-H demonstrated therapeutic significance in the KEYNOTE 158 study, the utility of 10 mutations/MB as a universal cutoff warrants additional evaluation. Here we report that a TMB-H cutoff value of ≥ 10 for patients with MSS CRC was not associated with clinically meaningful response to immunotherapy, but patients with MSS CRC with POLE/ POLD-1 mutations may be more likely to benefit from immunotherapy.