Immune checkpoint therapy (ICT) provides substantial clinical benefits to cancer patients, but a large proportion of cancers do not respond to ICT. To date, the genomic underpinnings of primary resistance to ICT remain elusive. Here, we performed immunogenomic analysis of data from TCGA and clinical trials of anti-PD-1/PD-L1 therapy, with a particular focus on homozygous deletion of 9p21.3 (9p21 loss), one of the most frequent genomic defects occurring in ~13% of all cancers. We demonstrate that 9p21 loss confers “cold” tumor-immune phenotypes, characterized by reduced abundance of tumor-infiltrating leukocytes (TILs), particularly, T/B/NK cells, altered spatial TILs patterns, diminished immune cell trafficking/activation, decreased rate of PD-L1 positivity, along with activation of immunosuppressive signaling. Notably, patients with 9p21 loss exhibited significantly lower response rates to ICT and worse outcomes, which were corroborated in eight ICT trials of >1,000 patients. Further, 9p21 loss synergizes with PD-L1/TMB for patient stratification. A “response score” was derived by incorporating 9p21 loss, PD-L1 expression and TMB levels in pre-treatment tumors, which outperforms PD-L1, TMB, and their combination in identifying patients with high likelihood of achieving sustained response from otherwise non-responders. Moreover, we describe potential druggable targets in 9p21-loss tumors, which could be exploited to design rational therapeutic interventions.

PURPOSE: DNA polymerase epsilon is critical to DNA proofreading and replication. Mutations in POLE have been associated with hypermutated tumors and antitumor response to immune checkpoint inhibitor (ICI) therapy. We present a clinicopathologic analysis of patients with advanced cancers harboring POLE mutations, the pattern of co-occurring mutations, and their response to ICI therapy within the context of mutation pathogenicity.METHODS: We conducted a retrospective analysis of next-generation sequencing data at MD Anderson Cancer Center to identify patient tumors with POLE mutations and their co-occurring mutations. The pathogenicity of each mutation was annotated using InterVar and ClinVar. Differences in therapeutic response to ICI, survival, and co-occurring mutations were reported by POLE pathogenicity status.RESULTS: Four hundred fifty-eight patient tumors with POLE mutations were identified from 14,229 next-generation sequencing reports; 15.0% of POLE mutations were pathogenic, 15.9% benign, and 69.1% variant of unknown significance. Eighty-two patients received either programmed death 1 or programmed death ligand-1 inhibitors as monotherapy or in combination with cytotoxic T-cell lymphocyte-4 inhibitors. Patients with pathogenic POLE mutations had improved clinical benefit rate (82.4% v 30.0%; P = .013), median progression-free survival (15.1 v 2.2 months; P < .001), overall survival (29.5 v 6.8 months; P < .001), and longer treatment duration (median 15.5 v 2.5 months; P < .001) compared to those with benign variants. Progression-free survival and overall survival remained superior when adjusting for number of co-occurring mutations (≥ 10 v < 10) and/or microsatellite instability status (proficient mismatch repair v deficient mismatch repair). The number of comutations was not associated with response to ICI (clinical benefit v progressive disease: median 13 v 11 comutations; P = .18).CONCLUSION: Pathogenic POLE mutations were associated with clinical benefit to ICI therapy. Further studies are warranted to validate POLE mutation as a predictive biomarker of ICI therapy.

Summary: In recent years, there has been remarkable progress in our understanding of cancer biology, host responses, and the concept of precision oncology. These advances have focused attention on biomarker-driven, tissue-agnostic drug development strategies. The recent approvals by the FDA of pembrolizumab for the treatment of unresectable or metastatic, microsatellite instability–high or deficient mismatch repair solid tumors, and more recently for the treatment of tumor mutational burden–high tumors; and of larotrectinib and entrectinib for the treatment of neurotrophic tyrosine kinase (NTRK) fusion–positive solid tumors, have further heightened interest in target-driven as opposed to histology-driven drug development. Herein, we focus on tissue-agnostic clinical drug development with an understanding of target modulation in the context of histology. The use of molecular genetics and biomarker-driven strategies rather than traditional histology based on organ of origin has reinforced the concept of tissue-agnostic drug development. Recent approvals in the United States, Europe, Japan, Australia, and other regions have further heightened interest in target-driven as opposed to histology-driven drug development.

The regulatory approvals of tumor-agnostic therapies have led to the re-evaluation of the drug development process. The conventional models of drug development are histology-based. On the other hand, the tumor-agnostic drug development of a new drug (or combination) focuses on targeting a common genomic biomarker in multiple cancers, regardless of histology. The basket-like clinical trials with multiple cohorts allow clinicians to evaluate pan-cancer efficacy and toxicity. There are currently eight tumor agnostic approvals granted by the Food and Drug Administration (FDA). This includes two immune checkpoint inhibitors, and five targeted therapy agents. Pembrolizumab is an anti-programmed cell death protein-1 (PD-1) antibody that was the first FDA-approved tumor-agnostic treatment for unresectable or metastatic microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) solid tumors in 2017. It was later approved for tumor mutational burden-high (TMB-H) solid tumors, although the TMB cut-off used is still debated. Subsequently, in 2021, another anti-PD-1 antibody, dostarlimab, was also approved for dMMR solid tumors in the refractory setting. Patients with fusion-positive cancers are typically difficult to treat due to their rare prevalence and distribution. Gene rearrangements or fusions are present in a variety of tumors. Neurotrophic tyrosine kinase (NTRK) fusions are present in a range of pediatric and adult solid tumors in varying frequency. Larotrectinib and entrectinib were approved for neurotrophic tyrosine kinase (NTRK) fusion-positive cancers. Similarly, selpercatinib was approved for rearranged during transfection (RET) fusion-positive solid tumors. The FDA approved the first combination therapy of dabrafenib, a B-Raf proto-oncogene serine/threonine kinase (BRAF) inhibitor, plus trametinib, a mitogen-activated protein kinase (MEK) inhibitor for patients 6 months or older with unresectable or metastatic tumors (except colorectal cancer) carrying a BRAF^V600E mutation. The most recent FDA tumor-agnostic approval is of fam-trastuzumab deruxtecan-nxki (T-Dxd) for HER2-positive solid tumors. It is important to identify and expeditiously develop drugs that have the potential to provide clinical benefit across tumor types.

PURPOSE: KRAS is the most mutated proto-oncogene that has been identified in cancer, and treatment of patients with KRAS mutations remains an arduous challenge. Recently, KRAS ^G12C mutation has attracted special interest because it is now considered potentially druggable with recently developed covalent small-molecule KRAS ^G12C inhibitors. Nevertheless, to date, there have been no large-scale analyses of liquid biopsy that include testing for KRAS ^G12C. Here, we performed a comprehensive analysis of KRAS ^G12C mutations in multiple cancer types, as detected by circulating tumor DNA. METHODS: We conducted a 5-year retrospective review of KRAS ^G12C mutations in patients with cancer who had undergone Guardant360 testing between July 1, 2014, and June 30, 2019; our study included treatment-naive and previously treated patients with metastatic solid tumors. RESULTS: KRAS ^G12C mutations were identified in 2,985 of 80,911 patients (3.7%), across > 40 tumor types. KRAS ^G12C mutations were detected most frequently in patients with nonsquamous non–small-cell lung cancer (NSCLC; 7.5%), NSCLC of all subtypes (6.9%), cancer of unknown primary (4.1%), colorectal cancer (3.5%), squamous NSCLC (2.0%), pulmonary neuroendocrine tumors (1.9%), and pancreatic ductal adenocarcinoma (1.2%) and cholangiocarcinoma (1.2%). KRAS ^G12C mutations were predominantly clonal (clonality > 0.9%) in patients with lung adenocarcinoma, non-NSCLC, cancer of unknown primary, NSCLC, and pancreatic ductal adenocarcinoma, and patients with colorectal cancer and breast cancer had bimodal distribution of clonal and subclonal KRAS ^G12C mutations. CONCLUSION: Our study demonstrates the feasibility of using circulating tumor DNA to identify KRAS ^G12C mutations across solid tumors; the highest detection rate was in lung cancer, as previously reported in the literature.

NTRK fusions are oncogenic drivers for multiple tumor types. Therefore, the development of selective tropomyosin receptor kinase (TRK) inhibitors, including larotrectinib and entrectinib, has been transformative in the context of clinical management, given the high rates of responses to these drugs, including intracranial responses in patients with brain metastases. Given their promising activity in pan-cancer cohorts, larotrectinib and entrectinib received U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) approval for tissue-agnostic indications in patients with advanced solid tumors harboring NTRK fusions. The safety profiles for both drugs are quite manageable, although neurotoxicity driven by the on-target inhibition of normal NTRK can be a concern. Also, on- and off-target resistance mechanisms can arise during therapy with TRK inhibitors, but they can be addressed with the use of combination therapy and next-generation TRK inhibitors. More recently, the FDA approved the use of repotrectinib, a second-generation TRK inhibitor, in patients with NTRK fusions, based on data suggesting clinical efficacy and safety, which could offer another tool for the treatment of NTRK-altered cancers. In this review, we summarize the current evidence related to the use of TRK inhibitors in the tissue-agnostic setting. We also elaborate on the safety profiles and resistance mechanisms from a practical perspective.