Oncology · Medical Literature
Guanylyl Cyclase 2C-Targeted Chimeric Antigen Receptor T-Cell Therapy in Patients With Metastatic Colorectal Cancer.
Abstract
The clinical efficacies of third- or later-line therapies for metastatic colorectal cancer (CRC) are extremely limited. The purpose of this study was to evaluate the safety and efficacy of a chimeric antigen receptor T (CAR T) cell targeting guanylyl cyclase 2C (GUCY2C) that was steadily expressed in all stages of CRC in a phase I study. This was an open-label, single-center, phase I study, consisting of a 3 + 3 pattern dose-escalation phase and a dose-expansion investigation. Tumor tissues were histologically confirmed positive for GUCY2C expression. Four dose levels were tested in the dose-escalation phase, including 3 × 108 (DL1), 6 × 108 (DL2), 12 × 108 (DL3), and 20 × 108 (DL4) CAR T cells. The primary end points were safety and tolerability within 28 days after the first infusion. In the dose-escalation phase, dose-limiting toxicity was not observed. DL3 was chosen for dose-expansion study. A total of 20 patients with metastatic CRC were infused with GUCY2C CAR T after lymphodepletion, and only one patient (5.0%) showed grade 3 cytokine release syndrome and neurotoxicity. Grade 3 diarrhea occurred in 11 patients (55.0%). Of 19 evaluable patients, the objective response rate (ORR) was 26.3%, with all responding patients in DL3 and DL4 groups. Of 10 patients in the DL3 group, the ORR was 40.0% and the median progression-free survival time (mPFS) was 7.0 months. Among patients showing medium-to-high GUCY2C expression in the DL3 group, the ORR achieved 50.0% and the mPFS was 9.0 months. GUCY2C CAR T showed acceptable safety profile and high response rate in patients with third- or later-line CRC, and the clinical efficacy was associated with CAR T dose level.
Clinical relevance
In patients with GUCY2C-expressing metastatic colorectal cancer who have progressed on three or more prior lines of therapy, what is the safety, tolerability, and preliminary antitumor efficacy of the autologous GUCY2C-targeted CAR T-cell product IM96 across escalating dose levels? __SNAPSHOT__ {"studyDesign":"Open-label, single-center, phase I dose-escalation (3+3 design) and dose-expansion study (NCT05287165)","setting":"Single center; Peking University Cancer Hospital and Institute, Beijing, China","sampleSize":"n=20 infused (dose-escalation + dose-expansion); 19 evaluable for efficacy","population":"Adult patients with histologically confirmed GUCY2C-positive metastatic colorectal cancer who had progressed on at least three prior lines of systemic therapy, including patients with liver metastases","intervention":"Single intravenous infusion of autologous GUCY2C-targeted CAR T cells (IM96) at one of four dose levels (DL1: 3×10⁸, DL2: 6×10⁸, DL3: 12×10⁸, DL4: 20×10⁸ CAR T cells) following lymphodepletion with fludarabine and cyclophosphamide","comparator":"Not applicable (single-arm study)","primaryOutcome":"Safety and tolerability within 28 days after the first CAR T-cell infusion, including dose-limiting toxicity (DLT) assessment","followUp":"Not reported (data cutoff December 2023 per conference abstract; exact individual follow-up duration not specified in the abstract)","fundingSource":"Government (National Natural Science Foundation of China; National Key Research and Development Program of China); additional sources not fully specified"}
Key findings
PRIMARY SAFETY OUTCOME: No dose-limiting toxicity (DLT) was observed across all four dose levels in the dose-escalation phase, and no maximum tolerated dose was reached. Of 20 infused patients, grade ≥3 cytokine release syndrome (CRS) occurred in 1 patient (5.0%) and grade ≥3 neurotoxicity (ICANS) occurred in 1 patient (5.0%). Notably, grade 3 diarrhea — a toxicity mechanistically anticipated given GUCY2C expression in normal intestinal mucosa — occurred in 11 of 20 patients (55.0%), representing the most frequent severe adverse event. DL3 (12×10⁸ CAR T cells) was selected for dose-expansion based on dose-escalation results. EFFICACY (secondary): Of 19 evaluable patients across all dose levels, the objective response rate (ORR) was 26.3%; all responses were observed exclusively in the DL3 and DL4 cohorts, indicating a dose-response relationship. In the DL3 cohort specifically (n=10), the ORR was 40.0% and the median progression-free survival (mPFS) was 7.0 months. In the DL3 subgroup with medium-to-high GUCY2C tumor expression (n not specified in the abstract), the ORR was 50.0% and mPFS was 9.0 months. The disease control rate in the DL3 cohort was 60.0% (reported separately in supplemental ASCO data). Confidence intervals, p-values, and overall survival data were not reported in the abstract. NNT is not calculable from the available data in the absence of a comparator arm. Duration of response was not reported in the abstract.
Practice implications
This phase I trial establishes that GUCY2C-targeted CAR T-cell therapy (IM96) can be administered at the tested dose levels without reaching a DLT or maximum tolerated dose, and the overall grade 3–4 toxicity profile — particularly for CRS and neurotoxicity — appears more favorable than that observed with CAR T therapies in hematologic malignancies. However, the 55% rate of grade 3 diarrhea is clinically significant and consistent with on-target, off-tumor activity against GUCY2C expressed in normal intestinal epithelium; this warrants careful monitoring and may limit tolerability in a broader population or at higher doses. The ORR of 26.3% overall and 40.0% in the recommended phase II dose cohort (DL3) is clinically noteworthy in a heavily pretreated population for whom approved options (e.g., regorafenib, TAS-102/trifluridine-tipiracil) typically yield ORRs below 5%. The signal that higher GUCY2C expression correlates with improved ORR (50.0% mPFS 9.0 months in medium-to-high expressors at DL3) suggests that biomarker-directed patient selection will be critical in future development. These findings apply to patients who are GUCY2C IHC-positive, have received ≥3 prior lines, and were enrolled at a single specialized Chinese center; generalizability to Western populations, patients with microsatellite-instable (MSI-H) disease, patients with poor performance status, or those ineligible for lymphodepletion is not established. This summary is based on abstract-level data only; full publication data including confidence intervals, response duration, subgroup analyses, and pharmacokinetics are not available for complete appraisal. __LIMITATIONS__ Very small sample size (n=20 total, n=10 in the recommended expansion dose cohort) severely limits precision of all efficacy and safety estimates; no confidence intervals or p-values are reported.,Single-center study conducted at a highly specialized institution in China; generalizability to other health systems, ethnic populations, and practice settings is unknown.,No control arm; historical comparator benchmarking is indirect and subject to selection bias.,Efficacy endpoints (ORR, PFS) are surrogates; no overall survival data are reported in the abstract.,Follow-up duration is not clearly reported, making durability of response unassessable from abstract alone.,Patient selection required histologic GUCY2C positivity, which may enrich for biologically favorable tumors and limit generalizability.,Biomarker subgroup analysis (medium-to-high GUCY2C expression) is exploratory and retrospective in nature, with subgroup size not reported; results should be considered hypothesis-generating only.,Manufacturing success rate and manufacturing failure (an important practical limitation of autologous CAR T therapies) are not reported in the abstract.,The 55% rate of grade 3 diarrhea may be underappreciated as a significant on-target toxicity that could affect tolerability and quality of life at scale.,Only abstract-level data are available for this review; full trial data including pharmacokinetics, response duration, and complete adverse event tables are not yet available for independent appraisal. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This phase I single-center trial of IM96, a GUCY2C-targeted autologous CAR T-cell therapy, demonstrated a manageable safety profile without dose-limiting toxicity and an ORR of 40% at the recommended phase II dose (12×10⁸ cells) in heavily pretreated, GUCY2C-positive metastatic CRC — a signal that substantially exceeds historical benchmarks for third-line or later therapy in this setting. Grade 3 diarrhea (55%) is a clinically important on-target toxicity requiring prospective management strategies. These preliminary findings support continued phase II evaluation with biomarker-driven patient selection, but are insufficient to change current practice given the small sample, single-center design, absence of a control arm, and abstract-only data availability.