Microsatellite Stable Metastatic Colorectal Cancer Research Articles

Phase Ib open-label, multicenter study of pixatimod, an activator of TLR9, in combination with nivolumab in subjects with microsatellite-stable metastatic colorectal cancer, metastatic pancreatic ductal adenocarcinoma and other solid tumors

BackgroundPixatimod is a unique activator of the Toll-like Receptor 9 pathway. This phase I trial evaluated safety, efficacy and pharmacodynamics of pixatimod and PD-1 inhibitor nivolumab in immunologically cold cancers.Methods3+3...

110P Fecal microbiota transplantation in combination with fruquintinib and tislelizumab in refractory microsatellite stable metastatic colorectal cancer: A single center phase II trial

Microsatellite stable (MSS) metastatic colorectal cancer (mCRC) is one of the tumor type in which PD-1 inhibitor as monotherapy has proven less effective. Studies have shown that anti-VEGF therapies may enhance anti-PD-1 efficacy and microbiome-based therapies can overcome resistance to anti-PD-1. This study was to explore the efficacy and safety of fecal microbiota transplantation (FMT) combined with anti-VEGF and anti-PD-1 therapy in advanced mCRC with MSS.

160P COLUMBIA-1: A phase Ib/II, open-label, randomized, multicenter study of durvalumab plus oleclumab in combination with chemotherapy and bevacizumab as first-line (1L) therapy in metastatic microsatellite-stable colorectal cancer (MSS-mCRC)

Despite advances in the treatment of mCRC combining chemotherapy regimens with biologics, most patients (pts) still progress within 11 months of receiving 1L chemotherapy. Addition of novel therapies to the standard of care (SoC) to improve antitumor activity is urgently needed. The randomized part 2 of COLUMBIA-1 (NCT04068610) evaluated the safety and efficacy of combining SoC (bevacizumab [BEV] + FOLFOX) with the PD-L1 inhibitor durvalumab (D) and the anti-CD73 monoclonal antibody oleclumab (O).

Regorafenib with or without a programmed cell death protein 1 antibody as third-line treatment for microsatellite stable metastatic colorectal cancer.

Although the use of regorafenib plus nivolumab demonstrates promising outcomes in patients with refractory microsatellite stable (MSS) metastatic colorectal cancer (mCRC), this effect has not been substantiated in other studies. Moreover, a comparison between the outcomes of regorafenib and programmed cell death protein 1 (PD-1) antibody combination therapy and regorafenib monotherapy remains unexplored. In this study, we aimed to assess whether regorafenib and PD-1 antibody combination therapy is superior to regorafenib monotherapy as a third-line treatment for MSS mCRC. Patients with MSS mCRC who received regorafenib and PD-1 antibody or regorafenib monotherapy as third-line treatment were eligible for inclusion. In total, 179 patients were enrolled, of which 84 were administered regorafenib combined with a PD-1 antibody and 95 were administered regorafenib monotherapy. Patients administered regorafenib combined with a PD-1 antibody had similar progression-free survival (PFS) as those on regorafenib monotherapy (median PFS was 2.4months and 1.9months, respectively, p=0.086). The administration of regorafenib combined with a PD-1 antibody resulted in significantly longer PFS than that seen with regorafenib monotherapy in both male (5.2months vs. 2.4 months, p=0.001) and female (3.9months vs. 1.8 months, p=0.037) patients without liver metastasis. Female patients with liver metastasis who were administered regorafenib combined with a PD-1 antibody had shorter PFS than those administered regorafenib monotherapy (1.8months vs. 2.0 months, p=0.030). Liver metastasis and sex are predictors of survival benefit following the addition of a PD-1 antibody to regorafenib in patients with MSS mCRC.

CXD101 and nivolumab in patients with metastatic microsatellite-stable colorectal cancer (CAROSELL): a multicentre, open-label, single-arm, phase II trial

Patients with microsatellite stable (MSS) colorectal carcinoma (CRC) do not respond to immune checkpoint inhibitors. Preclinical models suggested synergistic anti-tumour activity combining CXD101 and anti-programmed cell death protein 1 treatment; therefore, we assessed the clinical combination of CXD101 and nivolumab in heavily pre-treated patients with MSS metastatic CRC (mCRC). This single-arm, open-label study enrolled patients aged 18 years or older with biopsy-confirmed MSS CRC; at least two lines of systemic anticancer therapies (including oxaliplatin and irinotecan); at least one measurable lesion; Eastern Cooperative Oncology Group performance status of 0, 1 or 2; predicted life expectancy above 3 months; and adequate organ and bone marrow function. Nine patients were enrolled in a safety run-in study to define a tolerable combination schedule of CXD101 and nivolumab, followed by 46 patients in the efficacy assessment phase. Patients in the efficacy assessment cohort were treated orally with 20 mg CXD101 twice daily for 5 consecutive days every 3 weeks, and intravenously with 240 mg nivolumab every 2 weeks. The primary endpoint was immune disease control rate (iDCR). Between 2018 and 2020, 55 patients were treated with CXD101 and nivolumab. The combination therapy was well tolerated with the most frequent grade 3 or 4 adverse events being neutropenia (18%) and anaemia (7%). Immune-related adverse reactions commonly ascribed to checkpoint inhibitors were surprisingly rare although we did see single cases of pneumonitis, hypothyroidism and hypopituitarism. There were no treatment-related deaths. Of 46 patients assessable for efficacy, 4 (9%) achieved partial response and 18 (39%) achieved stable disease, translating to an immune disease control rate of 48%. The median overall survival (OS) was 7.0 months (95% confidence interval 5.13-10.22 months). The primary endpoint was met in this phase II study, which showed that the combination of CXD101 and nivolumab, at full individual doses in the treatment of advanced or metastatic MSS CRC, was both well tolerated and efficacious.

PD-1 Inhibitor Combined with Radiotherapy and GM-CSF with or not IL-2 (PRaG regimen) in Patients with Microsatellite Stable Metastatic Colorectal Cancer

<h3>Purpose/Objective(s)</h3> Immunotherapy has improved outcomes for metastatic colorectal cancer(mCRC) patients with MSI-H/dMMR but has not been effective in MSS/pMMR tumors, which comprise 95% of mCRC. Radiotherapy is able to stimulate tumor specific immune response and improve the efficacy of PD-1/PD-L1 inhibitors in metastatic cancers. The synergistic effects of radiotherapy and PD-1/PD-L1 inhibitors can be reinforced by adding cytokines like granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2(IL-2). Our previous PRaG trial demonstrated that radiotherapy in combination with PD-1 inhibitors and GM-CSF could improve clinical response in patients with advanced refractory solid tumors, which was presented at the ASTRO congress 2021. We found that mCRC patients with MSS/pMMR could also benefit from the PRaG regimen. <h3>Materials/Methods</h3> Patients of mCRC with MSS/pMMR were collected from the PRaG trial and PRaG 2.0 trial. A treatment cycle consisted of radiotherapy (5 or 8 Gy × 2-3f) delivered for one metastatic lesion, PD-1 inhibitor dosing within one week after completion of radiotherapy, GM-CSF 200μg subcutaneous (SC) injection once daily for 14 days(d1-14), or GM-CSF 200μg (d1-7), and then sequentially followed by IL-2 200 million IU SC once daily for 7 days(d8-14). PRaG regimen was repeated every 21 days for at least 2 cycles until no appropriate lesions for irradiation or reached the tolerance dose. Pooled analysis of response rate (ORR), median progression-free survival (PFS), and treatment-related adverse events were calculated. The PRaG trial was registered in chictr.org.cn (No. ChiCTR1900020175) and the PRaG 2.0 trial was registered in clinicaltrials.gov (NCT04892498). <h3>Results</h3> With the cutoff date of 15 February 2022, a total of 12 mCRC patients with MSS/pMMR were enrolled. All of the patients completed at least 2 cycles of PRaG therapy and one evaluation. The median follow-up was 7.0 months (95%CI, 4.7, 9.3). The ORR was 25%, and the disease control rate (DCR) was 58.3%. The median PFS was 4.7 months (95%CI, 0.9 to 8.5). One patient got complete remission, with PFS over 18 months. Treatment-related adverse events (TRAE) occurred in 10 of 12 (83.3%) patients. One patient (8.3%) occurred Grade3 TRAE of renal insufficiency. <h3>Conclusion</h3> Our preliminary results suggest that the PRaG regimen could improve clinical outcomes in mCRC patients with MSS/pMMR with acceptable toxicity. Radiotherapy could have radiosensitization effect on immunotherapy of mCRC with MSS/pMMR.

Microsatellite stable metastatic colorectal cancer without liver metastasis may be preferred population for regorafenib or fruquintinib plus sintilimab as third-line or above therapy:A real-world study.

ObjectivesThe antitumor activity of nivolumab plus regorafenib in colorectal cancer from a phase Ib REGONIVO study is encouraging. The present study was conducted to evaluate the efficacy and safety of regorafenib or fruquintinib plus sintilimab as third-line or above therapy in patients with microsatellite stable (MSS) metastatic colorectal cancer.MethodsPatients with MSS metastatic colorectal cancer who have failed from prior treatment and received regorafenib or fruquintinib plus sintilimab as third-line or above therapy from January 2019 to December 2020 were prospectively analyzed based on real-world clinical practice. The primary end point was progression free survival (PFS). Secondary end points included objective response rate (ORR), disease control rate (DCR), overall survival (OS), and safety.Results42 patients received regorafenib plus sintilimab(RS), and the other 30 patients received fruquintinib plus sintilimab(FS). In the general population, the ORR and DCR were 13.9% and 70.8%, and the median PFS and OS was 4.2(95% CI=2.9-5.5) and 10.5 (95% CI=8.6-12.4) months, respectively. There were no statistically significant differences between RS and FS group in PFS (3.5(2.2-4.8) vs. 5.5(3.5-7.5) months, P=0.434) and OS (11.0(7.0-15.0) vs. 10.5(3.8-17.2) months, P=0.486). Subgroup analysis suggested that patients without liver metastasis responded well to this combination regimen (ORR: 21.4% vs. 9.1%) and obtained better OS (26(8.8-43.2) vs. 10.0(7.4-12.6) months, P=0.016). The incidence of Grade 3-4 adverse events (AEs) was 15.3% and the toxicities were generally tolerable and manageable.ConclusionsRegorafenib or fruquintinib plus sintilimab as third-line or above therapy provide a feasible treatment regimen for MSS metastatic colorectal cancer with tolerated toxicity. Patients without liver metastasis may be the preferred population for this combination regimen.

1688P Selection of PD-L1 escape variants in microsatellite stable metastatic colorectal cancer on avelumab treatment

In patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC), immune checkpoint blockade is ineffective. However, data from the AVETUX trial suggests PD-L1 epitope escape upon avelumab treatment in MSS-mCRC patients expressing the high affinity SNP of FcγR3a (rs396991).

The Current and Evolving Role of Immunotherapy in Metastatic Colorectal Cancer.

Immunotherapy can be considered a therapeutic revolution in oncology, with great impact on many tumor types, such as melanoma and non-small cell lung cancer. However, in metastatic colorectal cancer, the benefits in terms of prolonged tumor control and high response rate are limited to the rare subgroup of tumors with high mutation burden - mostly tumors that harbor microsatellite instability (MSI) or a deficient mismatch repair system (dMMR), or tumor microsatellite stability and damaging mutations in the exonuclease domains of POLE or POLD. The KEYNOTE-028 uncontrolled phase II trial demonstrated an impressive antitumor activity of pembrolizumab in patients with treatmentrefractory Lynch-associated tumors, including colorectal cancer. Nivolumab with or without ipilimumab confirmed the efficacy of immune checkpoint inhibitors in patients with previously treated dMMR / MSI metastatic colorectal cancer. The recent KEYNOTE-177 phase III trial demonstrated that pembrolizumab significantly reduced the relative risk of disease progression or death and improved progression-free survival in patients with treatment-naive dMMR / MSI metastatic colorectal cancer in comparison with first-line chemotherapy with or without biologics. Unfortunately, current pharmacological strategies with immunotherapy have not been successful for most patients with microsatellite stable metastatic colorectal cancer. In this review, we critically appraise the applicability of immune checkpoint inhibitors in dMMR/MSI metastatic colorectal cancer. We also discuss the recent negative trials of immunotherapy combinations in microsatellite stabl.

Efficacy and safety of anti-PD-1 antibody plus regorafenib in refractory microsatellite stable metastatic colorectal cancer: a retrospective single-arm cohort study

BackgroundManagements for refractory proficient mismatch repair (pMMR) or microsatellite stable (MSS) metastatic colorectal cancer (mCRC) were still challenging and controversial. Our study sought to investigate the efficacy and safety of anti-programmed cell death protein 1 (anti-PD-1) antibodies plus regorafenib in refractory pMMR/MSS mCRC.MethodsWe retrospectively analyzed the efficacy and safety of 103 pMMR/MSS mCRC patients treated with at least one dose of anti-PD-1 antibodies plus regorafenib (80 mg once daily for 21 days on/7 days off 28 days as a cycle) between July 2019 and June 2021 at the Hunan Cancer Hospital. All patients had previously received at least second-line treatment. The patients were evaluated by computed tomography every 2 or 3 treatment cycles until progression or being lost to follow-up. The primary end point was overall survival (OS).ResultsThe median follow-up period was 5.30 (range, 0.50–22.50) months. The median OS (mOS) and medical progression-free survival (mPFS) were 8.40 and 2.50 months for the entire cohort, respectively. The mOS and mPFS were 16.07 and 3.10 months in patients who received >1 cycle of anti-PD-1 antibodies and regorafenib (n=55), which were significantly longer than 4.37 and 1.11 months in those received only 1 cycle (n=48) (both P<0.001, respectively). The Cox multivariate regression analysis demonstrated that the number of cycles of regorafenib plus PD-1 and previously undergone surgery were independent risk factors for OS, whereas Sintilimab was confirmed to have a significant better PFS compared to other anti-PD-1 antibodies. Of the 55 patients who were evaluated, 7 were diagnosed with a partial response (PR) and another 16 were diagnosed with stable disease (SD), but no patient showed a complete response (CR). Thus, the objective response rate (ORR) was 12.7% and the disease control rate was 41.8%. Treatment-related adverse events (TRAEs) of grade 3 or higher occurred in 13 (12.6%) patients.ConclusionsThe combination of regorafenib plus anti-PD-1 antibodies has a manageable safety profile and may improve prognosis for pMMR/MSS mCRC patients, especially those who received >1 cycle. Compared to the other anti-PD-1 antibodies, sintilimab may be more efficacious; however, further prospective studies need to be conducted to confirm our findings.

Abstract 5212: Braf-altered microsatellite-stable metastatic colorectal cancer: A niche for immunotherapy

Abstract Background: The successful inhibition of the PD-1/PD-L1 axis and CTLA-4 has opened the era of immuno-oncology, however only a few patients with metastatic colorectal cancer (mCRC) and microsatellite instability (MSI, ~5%) derive survival benefits from these treatments. BRAF genomic alterations, mainly V600 point mutations, comprise 10-15% of cases and have a poorer prognostic phenotype. Method: The public domain genomic database (via cBioPortal and AACR Project GENIE) was used as an external control to explore the genomic make-up of BRAF-mutated and BRAF-wild mCRC tumors. The Wilcoxon sum rank test was used for the genome-wide association analysis, and the Kaplan-Meier method was used to estimate survival. Besides, clinical observations on extraordinary responses to regorafenib plus nivolumab therapy in two patients with microsatellite stable (MSS) mCRC with BRAF genomic alterations were reported. Result: The CRC cohort comprised 2,936 patients and the immune checkpoint inhibitor (ICI) treated cohort comprised 1,661 patients, of which 110 (6.6%) were CRC patients. BRAF genomic alterations (CRC versus ICI cohort: 12.4% versus 11.8%, respectively) were significantly associated with POLE and PRKDC gene mutations (p&amp;lt;0.001). The genomic signatures, such as higher mutation count (MC) (log2 [6.54 versus 3], Wilcoxon p&amp;lt;10-10) and lower fraction genome altered (FGA) (log2 [-3.62 versus -2.22], Wilcoxon p=2.08e-9) were similar to that of POLE and PRKDC in the CRC cohort. Also, BRAF genomic alterations are associated with higher mutation counts in not only MSI but MSS cohorts (p=0.033 and p&amp;lt;0.001, respectively). In the ICI cohort, BRAF-altered colorectal tumors were associated with a higher TMB (43.3 versus 7.81, Wilcoxon p=0.016). In the CRC cohort, BRAF-altered tumors were associated with poorer overall survival (median 38.04 versus &amp;gt;80 month, log rank p&amp;lt;0.0001); and in the ICI cohort, BRAF-altered colorectal tumors were associated with a trend of better overall survival after ICI treatment (median &amp;gt;80 versus 15 months, log rank p=0.121) Conclusion: BRAF-mutated malignancies represent a sub-population of MSS CRC with higher TMB, which could benefit from a combination of regorafenib and nivolumab therapy. Citation Format: Feng-Che Kuan, Chung-Sheng Shi, Yu-Ying Wu, Meng-Hung Lin. Braf-altered microsatellite-stable metastatic colorectal cancer: A niche for immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5212.

FAT4 mutation as a potential predictive biomarker for immunotherapy combined with anti-angiogenic therapy in MSS metastatic colorectal cancer.

e15504 Background: Microsatellite stable (MSS) metastatic colorectal cancer (CRC) lacks effective treatments and has a poor prognosis. The aim of this study was to identify patients who could benefit from immunotherapy combined with anti-angiogenic therapy. Exploration of predictive biomarkers could help to maximize the clinical benefits. Methods: In total, FFPE tissues samples before immunotherapy combined with anti-angiogenic therapy of 21 patients were successfully tested for tumor microenvironments (TMEs) by multiple immunofluorescence, of which 11 of them were successfully detected by 733-gene NGS panel in a CLIA-certified laboratory. The correlation between gene variations and clinical durable benefit (DCB: PR, or SD≥6 months), PFS and TMEs were analyzed by Fisher's test, K-M survival curve analysis and Mann Whitney analysis respectively. Results: Significant difference was detected between FAT4 mutation (FAT4-MUT) and FAT4 wildtype (FAT4-WT) regarding DCB (100%, 4/4 vs 17%, 1/7, P = 0.0152) and progress-free survival (median PFS, 13.8 months vs 2.8 months, LogRank P = 0.003). There was no significant difference in TMB level between DCB and NDB (SD＜6 months, or PD) groups (12 mut/Mb vs 6 mut/Mb, P = 0.0823) or between FAT4-MUT and FAT4-WT (11 mut/Mb vs 6 mut/Mb, P = 0.3697). TMEs analyses revealed that the CD3+CD4+ T cell proportion was tended to be higher in FAT4-MUT (0.7% vs 0.3%, P = 0.054). Further TIMER2.0 data showed FAT4-MUT was significantly associated with higher Immune infiltration of four immune cells, including CD4+ T cell in both colon and rectal adenocarcinoma, CD8+ central memory T cell, B cell, and Macrophage in colon adenocarcinoma. Conclusions: Our findings indicated that FAT4 mutation serves as a potential novel biomarker correlated with a better response to immunotherapy combined with anti-angiogenic therapy in MSS metastatic CRC, which may be related to the activation of CD4 T cell infiltration. However, these need to be validated by further cohort expansion.

The response of PD-1 inhibitor combined with Radiotherapy and GM-CSF(PRaG) with or without IL-2 in microsatellite stable metastatic colorectal cancer: Analysis of pooled data from two phase II trials.

e15561 Background: Immunotherapy has improved outcomes for metastatic colorectal cancer(mCRC) patients with MSI-H/dMMR but has not been effective in MSS/pMMR tumors, which comprise 95% of mCRC. In metastatic cancers, radiotherapy can be used as a local therapy and a sensitizer to PD-1/PD-L1 inhibitors. The synergistic effects of radiotherapy and PD-1/PD-L1 inhibitors can be reinforced by adding cytokines like granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2(IL-2). Our previous PRaG trial demonstrated that PD-1 inhibitors in combination with radiotherapy and GM-CSF could improve clinical response in patients with advanced refractory solid tumors. We found that mCRC patients with MSS/pMMR could also benefit from the PRaG regimen. Methods: Patients of mCRC with MSS/pMMR were collected from the PRaG trial and PRaG 2.0 trial. A treatment cycle consisted of radiotherapy (5 or 8Gy×2-3f) delivered for one metastatic lesion, PD-1 inhibitor dosing within one week after completion of radiotherapy, GM-CSF 200μg subcutaneous (SC) injection once daily for 14 days(d1-14), or GM-CSF 200μg (d1-7), and then sequentially followed by IL-2 200 million IU SC once daily for 7 days(d8-14). PRaG regimen was repeated every 21 days for at least 2 cycles until no appropriate lesions for irradiation or reached the tolerance dose. Pooled analysis of response rate (ORR), median progression-free survival (PFS), and treatment-related adverse eventswere calculated. Results: With the cutoff date of 31 December 2021, a total of 9 mCRC patients with MSS/pMMR were enrolled. All of the patients completed at least 2 cycles of PRaG therapy and one evaluation. The median follow-up was 7.6 months (95%CI, 3.8, 11.4). The ORR was 22.2%, and the disease control rate(DCR) was 66.7%. The median PFS was 5.6 months (95%CI, 1.5 to 9.7). One patient got complete remission, with PFS over 17months. Treatment-related adverse events (TRAE) occurred in 7 of 9 (77.8%) patients. One patient (11.1%) occurred Grade3 TRAE of renal insufficiency. Conclusions: Our preliminary results suggest that the PRaG regimen could improve clinical outcomes in mCRC patients with MSS/pMMR with acceptable toxicity.

P-23 Phase II study (daNIS-3) of the anti–TGF-β monoclonal antibody NIS793 and other new investigational drug combinations with standard-of-care therapy vs standard-of-care alone in patients with second-line metastatic colorectal cancer

Colorectal cancer (CRC) is the second leading global cause of cancer-related death. Despite recent improvements in chemotherapy + targeted agent combination therapies, treatment options for second-line, microsatellite-stable metastatic CRC (mCRC) remain suboptimal. TGF-β has a multifactorial role in tumorigenesis and maintaining an immunosuppressive tumor microenvironment. NIS793 is a potent, selective, human IgG2 monoclonal antibody (mAb) antagonist of TGF-β. This study investigates NIS793 in combination with standard-of-care (SOC) for second-line treatment of mCRC.

Regorafenib combined with programmed cell death-1 inhibitor against refractory colorectal cancer and the platelet-to-lymphocyte ratio's prediction on effectiveness.

BACKGROUNDThe effectiveness of regorafenib plus programmed cell death-1 (PD-1) inhibitor in treating microsatellite stable (MSS) metastatic colorectal cancer (mCRC) remains controversial. AIMTo investigate the benefits of regorafenib combined with PD-1 inhibitor in treating MSS mCRC and explore indicators predicting response. METHODSThis retrospective study included a total of 30 patients with microsatellite stable metastatic colorectal cancer treated with regorafenib combined with programmed cell death-1 inhibitor at Henan Provincial People’s Hospital between December 2018 and December 2020. During a 4-wk treatment cycle, regorafenib was performed for 3 continuous weeks. PD-1 inhibitor was intravenously injected starting on the first day of the oral intake of regorafenib. We reviewed tumor response, progression-free survival (PFS), overall survival, and treatment-related adverse events (TRAEs) and evaluated association between platelet-to-lymphocyte ratio (PLR) and outcomes in this retrospective study. RESULTSStable disease and progressive disease were found in 18 (60.0%) and 12 (40.0%) patients, respectively. The disease control rate was 60.0%. The median follow-up time was 12.0 mo, and median PFS was 3.4 mo [95% confidence interval (CI): 2.2-4.6 mo]. Of the 12 patients with progressive disease, 10 (83.3%) had liver metastasis before starting the combined treatment. Among the 18 patients with SD, 10 (55.6%) did not have liver metastases. One patient without liver metastases at baseline was found with a substantially prolonged PFS of 11.2 mo. The liver metastasis, the choice of programmed cell death-1 inhibitor other than nivolumab or pembrolizumab and previous exposure to regorafenib was’t associated with treatment outcome. The median PFS in the low-PLR group was 4.2 mo (95%CI: 3.5-4.9 mo), compared with 2.8 mo (95%CI: 1.4-4.2 mo) in the high-PLR group (P = 0.005). The major TRAEs included hand-foot syndrome (33.3%), hypertension (23.3%), malaise (20.0%), and gastrointestinal reaction (16.7%). The incidence of grade 3 TRAEs was 13.3% (4/30), which comprised abnormal capillary proliferation (n = 1), transaminase elevation (n = 1), and hand-foot syndrome (n = 2). No grade 4 or higher toxicity was observed. CONCLUSIONRegorafenib combined with PD-1 inhibitor could lead to a longer PFS in some patients with MSS mCRC. The PLR might be a prediction of the patient response to this therapy.

A phase II study of pembrolizumab, binimetinib, and bevacizumab in patients with microsatellite-stable, refractory, metastatic colorectal cancer (mCRC).

118 Background: To date, immune-checkpoint inhibition for microsatellite stable (MSS) mCRC has been ineffective, though targeted therapy combination strategies may be promising. This phase II, investigator-initiated trial (NCT03475004) was designed to evaluate the efficacy and safety of the three-drug combination of pembrolizumab (pembro), binimetinib, and bevacizumab in patients with advanced, MSS treatment-refractory colorectal cancer. Methods: Patients with mCRC locally determined to be MSS and whom have progressed on two prior lines of therapy were enrolled. Treatment consists of pembro (200 mg every 3 weeks), binimetinib (45 mg BID) and bevacizumab (7.5 mg/kg every 3 weeks) until disease progression or unacceptable toxicity. The primary endpoint is PFS using RECIST v1.1 by investigator review. Additional endpoints include objective response rate, disease control rate at time of first re-staging (2 mo), duration of response, and safety and tolerability. Results: 50 patients have been enrolled (accrual is completed). 53% of patients are male and the mean age is 53.6 (range 31-79). The mean number of prior therapies is 5.3. At the time of preliminary data review, 39 patients are evaluable for response data. The median PFS was 5.8 mo (95% CI 4.2 to 8.9). The objective response rate was 13% with 5 partial responses. 24 patients (62%) had stable disease and 10 (26%) had progressive disease as the best response. The disease control rate at the time of first re-staging was 74%. Median duration of response was 6.5 mo. 19 (40%) patients experienced serious adverse events; the most common grade ≥3 adverse events included transaminase elevation (15%), diarrhea (11%), acneiform rash (9%), hypertension (9%), and anemia (9%). Conclusions: Preliminary results from this phase II study indicate that this regimen of pembrolizumab, binimetinib, and bevacizumab has promising activity and acceptable tolerability in this heavily pre-treated population of patients with MSS metastatic colorectal cancer. Final results will be presented as well as ongoing correlative studies. Clinical trial information: NCT03475004.

Concurrent BRAFV600E and BRCA Mutations in MSS Metastatic Colorectal Cancer: Prevalence and Case Series of mCRC patients with prolonged OS

BackgroundBRAF V600E+ microsatellite stable (MSS) metastatic colorectal cancer (mCRC) patients comprise up to 10% of advanced CRC. They have a poor prognosis with a median survival typically <1 year. Despite use of multi-agent 1st line chemotherapy regimens and combination targeted therapies, outcomes are still poor. In our Institutional Molecular Tumor Board (MTB) database, we identified 3 mCRC patients with MSS/BRAF V600E who also had a BRCA1 or BRCA2 co-mutation and had relatively long overall survivals. Prior studies suggested that BRCA mutations are uncommon in CRC and we queried the Foundation Medicine (FM) genomic database to evaluate the prevalence of these cases as well as those with co-mutations in other homologous recombination genes. Methods36,966 CRC pts were sequenced by FMI using hybrid capture comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA) for pathogenic BRAF mutations and/or a mutation in BRCA1/2 or a co-mutation in other homologous recombination (HR) genes (BARD1, CDK12, FANCL, PALB2, ATM, RAD54L, CHEK2, BRAF, BRIP1, RAD51D, RAD51C, RAD51B, CHEK1). Selected cohort analysis of BRAF V600E co-mutated with BRCA1 and BRCA2 were separated into MSI-H and MSS cohorts. The clinicopathological features and genomic loss of heterozygosity (gLOH) of those with a BRAF V600E and a BRCA1/BRCA2 mutation were collected and analyzed. We also describe 3 consecutive cases of mCRC patients, identified through the Inova Schar Cancer Institute (ISCI) MTB registry, whom had prolonged OS. ResultsOf 36,966 colorectal cancer pts, 6.6% were BRAF V600E+ and 1.5% had any co-occurring HR gene mutation(s) with 0.6% of the total mCRC population having co-ocurring BRAF V600E and BRCA1/2 alterations. BRCA co-mutations were higher in MSI-High BRAF V600E, however 24.1% of co-occurrences were observed in MSS samples. BRCA1 co-mutation was more commonly associated with MSS BRAF V600E and was associated with a higher gLOH than MSI-H BRAF V600E (18.7% vs 2.8%; p <0.001). In our institutional MTB database, (3/241;1.2%) CRC patients were MSS, BRAF V600E+ with BRCA1 or BRCA2 co-mutations, all somatic in origin, with an average gLOH of 21.4% and overall survivals of 72+(alive), 17+(alive), and 30 months, respectively. ConclusionCo-existence of BRAF V600E/BRCA1/2 may represent a unique subset of advanced MSS CRC that may have a better prognosis and represent an opportunity to test novel targeted therapies. The elevated gLOH in these cases may also be a valuable biomarker for these pts. Larger prospective clinical validation trials in this subset is warranted.

Tumour mutational burden predicts resistance to EGFR/BRAF blockade in BRAF-mutated microsatellite stable metastatic colorectal cancer

AimTo unveil genomic and immunohistochemical expression profiles associated with primary resistance to EGFR/BRAF targeted therapy in patients with BRAF-mutated and microsatellite stable (MSS) metastatic colorectal cancer. Experimental designIn this multicenter case-control study on patients treated with EGFR/BRAF ± MEK blockade, we compared a primary resistance cohort (N = 20; RECISTv1.1 PD/SD, and progression-free survival [PFS] <16 weeks) versus a sensitive one (N = 19; RECISTv1.1 PR/CR, and PFS ≥16 weeks) in terms of clinical and genomic/expression data by means of comprehensive genomic profiling, tumour mutational burden (TMB), BRAF-mutant transcriptional subtypes (BM) classification and PTEN expression. ResultsLeft-sided tumours (28% of the total) were enriched in the sensitive versus resistant cohort (53% versus 10%, P = 0.010). Genomic alterations in the PIK3CA/MTOR pathway, BM1 status and PTEN loss were similarly distributed among patients with resistant and sensitive tumours. Amplification of CCND1-3 genes were found only in patients with primary resistance (20% versus 0%, P = 0.106). TMB and prevalence of intermediate TMB (TMB-I 6–20 mutations/Mb) were higher in the resistant versus sensitive cohort (median TMB: 6 [IQR, 3–7.29] versus 3 [IQR, 1.26–3.5]; P = 0.013; TMB-I/H: 60% versus 11%; P = 0.001). Patients with TMB-I had shorter PFS (3.3 versus 5.9 months; HR = 2.19, 95%CI, 1.07–4.47, P = 0.031) and overall survival (6.3 versus 10.5 months; HR = 2.22, 95%CI, 1.02–4.81, P = 0.044). ConclusionDespite the small sample size, the association of a relatively higher TMB with limited benefit from EGFR/BRAF blockade in patients with MSS and BRAF-mutated mCRC deserves prospective validation.

Proteasome inhibitors restore the STAT1 pathway and enhance the expression of MHC class I on human colon cancer cells

BackgroundA new strategy, particularly a novel combination, for immunotherapy in microsatellite stable metastatic colorectal cancer (mCRC) treatment needs to be formulated. Studies on the interferon-γ (IFN-γ)/ Janus kinase (JAK)/ signal transducer and activator of transcription (STAT)1 pathway provide new directions in this regard.MethodsOur study applies three colon cancer cell lines, including microsatellite stable (MSS) cell lines, which are SW480 and SW620, and microsatellite instability-high (MSI-H) cell line, which is DLD-1. We compared the expressions of immune surface markers on colon cancer cells in response to IFN-γ. We elucidated these mechanisms, which involved the upregulation of immune surface markers. Furthermore, we examined real-world clinical samples using the PerkinElmer Opal multiplex system and NanoString analysis.ResultsWe established that the baseline expression of major histocompatibility complex (MHC) class I alleles and programmed death-ligand 1 (PD-L1) were generally low in cell line models. The immune surface markers were significantly increased after IFN-γ stimulation on SW480 but were notably unresponsive on the SW620 cell line. We discovered that STAT1 and phosphorylated STAT1 (pSTAT1) were downregulated in the SW620 cell line. We verified that the STAT1/pSTAT1 could be restored through the application of proteasome inhibitors, especially bortezomib. The expression of MHC class I as downstream signals of STAT1 was also up-regulated by proteasome inhibitors. The similar results were reproduced in DLD-1 cell line, which was also initially unresponsive to IFN-γ. In real-world samples of patients with mCRC, we found that higher STAT1 expression in tumor cells was strongly indicative of a highly immunogenic microenvironment, with significantly higher expression levels of MHC class I and PD-L1, not only on tumor cells but also on non-tumor cells. Furthermore, tumor infiltrating lymphocytes (TILs) were increased in the positive-STAT1 group. Through NanoString analysis, we confirmed that the mRNA expressions of IFN-γ, human leukocyte antigen (HLA)-A, HLA-E, and HLA-G were also significantly higher in the positive-STAT1 group than those in the negative-STAT1 group.ConclusionOur study provides a novel rationale for the addition of bortezomib, a proteasome inhibitor, into new immunotherapy combinations.

Real-world outcomes of regorafenib combined with immune checkpoint inhibitors in patients with advanced or metastatic microsatellite stable colorectal cancer: A multicenter study

BackgroundTreatment strategies are limited for patients with chemotherapy refractory microsatellite stable (MSS) colorectal cancer. We aim to evaluate the efficacy and safety of immune checkpoint inhibitors (ICIs) combined with regorafenib in this population in routine clinical practice.MethodsWe retrospectively analyzed patients with advanced or metastatic colorectal cancer who received at least one dose of ICIs combined with regorafenib in 14 Chinese medical centers. The primary outcome was objective response rate (ORR). This study was registered at ClinicalTrials.gov on February 2020 (NCT04771715).ResultsEighty-four patients received ICIs combined with regorafenib from January 2019 to January 2021. Most patients (91%) received two or more systemic treatment lines before the study treatment. Seventy-six patients (90%) had confirmed MSS status. At a median follow-up of 5.5 months, four patients achieved partial response (5%) and 37 patients achieved stable disease (45%) as the best response. The median progression-free survival (PFS) was 3.1 months, and the median overall survival was 17.3 months. Eleven patients (13%) remained progression-free for more than 6 months. Baseline liver metastasis (HR 1.98, 95%CI 1.07–3.69, P = 0.03) and neutrophil–lymphocyte ratio (NLR) of ≥ 1.5 (HR 2.83, 95%CI 1.00–7.98, P = 0.05) were associated with shorter PFS in multivariate analysis. Grade 3 or higher treatment-related adverse events (TRAEs) occurred in 16 patients (19%).ConclusionThe combination of ICIs with regorafenib can be a valuable treatment option for a proportion of patients with chemotherapy refractory MSS colorectal cancer. Patients with no liver metastasis and a low NLR at baseline may derive most benefit from this strategy.