Neoadjuvant immunotherapy involves administering immune checkpoint inhibitors before surgical resection in high-risk resectable disease. This strategy was shown to have a high pathological response rate and prolonged relapse-free survival in randomized trials in melanoma, glioblastoma, and colon cancer with small numbers of patients. In resectable cancers, immune checkpoint inhibitors such as anti-programmed cell death-1 (PD1) and anti-cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) can enhance antitumor immunity by activating antigen-specific T cells found in the primary tumor. These tumor-reactive T cells continue to exert antitumor effects on remaining neoplastic cells after the resection of the primary tumor, potentially preventing relapses from occurring. Based on the scientific rationale and early clinical observations with surrogate survival endpoints, neoadjuvant immunotherapy may provide an effective alternative to other therapeutic strategies such as adjuvant treatment. However, this can be determined only by conducting randomized controlled trials comparing neoadjuvant immunotherapy with the current standard of care for each tumor site. This review discusses the cellular mechanisms that occur during successful neoadjuvant immunotherapy and highlights the clinical data from the available human studies that support the preclinical mechanistic data. Here we also discuss strategies required for successful neoadjuvant immunotherapy, including combination treatment strategies and resistance mechanisms to neoadjuvant treatment.

Background: Microbiome manipulation research is focused on developing techniques to modify the gut microbiome and augment responses to immune checkpoint inhibitors (ICI). Fecal microbiota transplantation (FMT) represents a potential strategy to overcome primary or acquired resistance to ICI. 20 patients with advanced melanoma were enrolled in a phase I multicenter trial to evaluate the safety and response to anti-PD1 combined with FMT using healthy donor stool as first-line treatment (MIMic, NCT03772899 ). Combination therapy was safe, and the objective response rate (ORR) was 65%. We now report survival data based on over 3 years of follow-up. Patients with advanced melanoma and treatment-naïve for advanced disease received a single FMT with healthy donor stool followed by standard anti-PD1 therapy. Progression-free survival (PFS) and overall survival (OS) were measured from the date of FMT to event. Radiographic response was measured using RECIST 1.1 criteria. Both median PFS (mPFS) and median OS (mOS) were determined using the Kaplan-Meier method. Post hoc analyses assessed the impact of specific factors on survival outcomes. Minimum follow-up was 40 months from the date of FMT of the last patient, with the longest surviving patient in complete response at 62.2 months. At the time of data analysis, eight patients were alive and seven patients were without progression. No patients remain on anti-PD1 therapy. Only two patients received additional lines of therapy. The mPFS was 29.6 months and mOS 52.8 months. The 1, 2, and 3 years estimated survival rates were 95%, 74% and 53%, respectively. Post hoc analysis demonstrated significantly improved mPFS in responders and patients with FMT-specific toxicity. Combining first-line anti-PD1 therapy and oral FMT with healthy donor stool in this small cohort was safe and demonstrated an improvement in ORR, mPFS, and mOS, compared with randomized trials. Our sample size was small, and results were only hypothesis generating. The potential benefit of microbiome manipulation using oral FMT from healthy donors prior to ICI in patients with advanced melanoma will be evaluated in the ME.17 randomized phase 2 Canadian study ( NCT06623461 ).

Pancreatic cancer has a high mortality rate, and its incidence is increasing worldwide. The almost universal poor prognosis of pancreatic cancer is partly due to symptoms presenting only at late stages and limited effective treatments. Recently, immune checkpoint blockade inhibitors have drastically improved patient survival in metastatic and advanced settings in certain cancers. Unfortunately, these therapies are ineffective in pancreatic cancer. However, tumor biopsies from long-term survivors of pancreatic cancer are more likely to be infiltrated by cytotoxic T-cells and certain species of bacteria that activate T-cells. These observations suggest that T-cell activation is essential for anti-tumor immunity in pancreatic cancers. This review discusses the immunological mechanisms responsible for effective anti-tumor immunity and how immune-based strategies can be exploited to develop new pancreatic cancer treatments.

Immune-checkpoint inhibitors benefit a subset of patients with advanced cancer, and the metabolic determinants of response remain unclear. Here, using targeted metabolomics and metagenomics, we profiled 4,336 plasma samples from 1,714 patients across five tumor types and 16 cohorts spanning Europe and North America, longitudinally sampled during five immune-checkpoint inhibitor-based treatment modalities, including fecal microbiota transplantation. A multimodal machine-learning framework integrating 154 metabolites with clinical variables identified five metabolites, age, body mass index and renal function as predictors of 12-month progression-free survival. The model achieved areas under the curve of 0.88 in training and 0.73 in validation cohorts of 105 and 30 patients, respectively and generalized across seven external cohorts. Histidine was a favorable prognostic feature of survival, whereas long-chain fatty acids and succinate were negatively associated with outcome. Histidine supplementation enhanced antitumor immunity in mice. Histidine-rich diets improved progression-free survival in patients lacking dysbiotic microbiome signatures associated with histidine catabolism.

Aim: To evaluate optimal systemic therapy sequencing (first-line targeted therapy (1L-TT) vs. first-line immunotherapy (1L-IO)) in patients with BRAF-mutated metastatic melanoma. Methods: Nation-wide prospective data of patients with newly diagnosed BRAF-mutated metastatic melanoma were retrieved from the Canadian Melanoma Research Network. Results: Our study included 79 and 107 patients in the 1L-IO and 1L-TT groups, respectively. There were more patients with ECOG 0–1 (91% vs. 72%, p = 0.023) in the 1L-IO group compared to the 1L-TT group. Multivariable Cox analysis suggested no OS differences between the two groups (HR 0.838, 95%CI 0.502–1.400, p = 0.500). However, patients who received 1L-TT then 2L-IO had the longest OS compared to 1L-IO without 2L therapy, 1L-IO then 2L-TT, and 1L-TT without 2L therapy (38.3 vs. 32.2 vs. 16.9 vs. 6.3 months, p < 0.001). For patients who received 2L therapy, those who received 2L-IO had a trend towards OS improvement compared with the 2L-TT group (21.7 vs. 8.9 months, p = 0.053). Conclusions: Our nation-wide prospective study failed to establish any optimal systemic therapy sequencing in advanced BRAF-mutant melanoma patients. Nevertheless, we provided evidence that immunotherapy has durable efficacy in advanced BRAF-mutant melanoma patients, regardless of treatment line, and that Canadian medical oncologists were selecting the appropriate treatment sequences in a real-world setting, based on patients’ clinical and tumour characteristics.