Targeting the intracellular immune checkpoint CISH with CRISPR-Cas9-edited T cells in patients with metastatic colorectal cancer: a first-in-human, single-centre, phase 1 trial

Background: Over the past decade, immunotherapeutic strategies-mainly targeting the PD-1-PD-L1 immune checkpoint axis-have altered cancer treatment for many solid tumours, but few patients with gastrointestinal forms of cancer have benefited to date. There remains an urgent need to extend immunotherapy efficacy to more patients while addressing resistance to current immune checkpoint inhibitors. The aim of this study was to determine the safety and anti-tumour activity of knockout of CISH, which encodes cytokine-inducible SH2-containing protein, a novel intracellular immune checkpoint target and a founding member of the SOCS family of E3-ligases, using tumour infiltrating lymphocyte (TILs) genetically edited with CRISPR-Cas9 in patients with metastatic gastrointestinal epithelial cancers.

Methods: For this first-in-human, single-centre, phase 1 trial, patients aged 18-70 years with a diagnosis of metastatic gastrointestinal epithelial cancer with progressive disease following at least one first line standard therapy, measurable disease with at least one lesion identified as resectable for TIL generation and at least one other lesion meeting RECIST criteria as measurable to serve as an indicator of disease response, and an ECOG performance status of 0 or 1 were screened and enrolled if meeting these and all other eligibility criteria. TILs procured from tumour biopsies were expanded on the basis of neoantigen reactivity, subjected to CRISPR-Cas9-mediated CISH knockout, and infused intravenously into 12 patients after non-myeloablative lymphocyte depleting chemotherapy (cyclophosphamide 60 mg/kg per dose on study days -6 and -5, and fludarabine 25 mg/m2 per dose on days -7 to -3) followed by high-dose IL-2 (aldesleukin; 720 000 IU/kg per dose). The primary endpoint was safety of administration of neoantigen-reactive TILs with knockout of the CISH gene, and a key secondary endpoint was anti-tumour activity measured as objective radiographic response and progression-free and overall survival. This study is registered with ClinicalTrials.gov, NCT04426669, and is complete.

Findings: Between May 12, 2020, and Sept 16, 2022, 22 participants were enrolled in the trial (one patient was enrolled twice owing to lack of TIL outgrowth on the first attempt); ten patients were female, and 11 were male (self-defined). One patient was Asian, the remainder were White (self-defined). We successfully manufactured CISH knockout TIL products for 19 (86%) of the patients, of whom 12 (63%) received autologous CISH knockout TIL infusion. The median follow-up time for the study was 129 days (IQR 15-283). All 12 (100%) patients had treatment-related severe adverse events. The most common grade 3-4 adverse events included haematological events (12 patients [100%]) attributable to the preparative lymphodepleting chemotherapy regimen or expected effects of IL-2, fatigue (four patients [33%]), and anorexia (three patients [25%]). Deaths of any cause for patients on study were attributed to the underlying disease under study (metastatic gastrointestinal cancer) and related complications (10 patients) or infection (grade 5 septicaemia in one patient). There were no severe (≥grade 3) cytokine release or neurotoxicity events. Six (50%) of 12 patients had stable disease by day 28, and four (33%) had stable disease ongoing at 56 days. One young adult patient with microsatellite-instability-high colorectal cancer refractory to anti-PD1/CTLA-4 therapies had a complete and ongoing response (>21 months).

Interpretation: These results support the safety and potential antitumour activity of inhibiting the immune checkpoint CISH through the administration of neoantigen-reactive CISH-knockout TILs, with implications for patients with advanced metastatic cancers refractory to checkpoint inhibitor immunotherapies, and provide the first evidence that a novel intracellular checkpoint can be targeted with therapeutic effect.

Funding: Intima Bioscience.