Neoadjuvant toripalimab plus celecoxib versus toripalimab monotherapy for mismatch repair-deficient or microsatellite instability-high, locally advanced colorectal cancer (PICC-2): an open-label, multicentre, randomised, phase 2 trial
Mené sur 110 patients atteints d'un cancer colorectal de stade localement avancé et présentant une haute instabilité des microsatellites ou une déficience du système MMR (durée médiane de suivi : 18,1 mois), cet essai multicentrique de phase II évalue l'efficacité, du point de vue du taux de réponse complète, et la toxicité de l'ajout du célécoxib au toripalimab en traitement néoadjuvant
Background: Neoadjuvant immune checkpoint blockade has shown remarkable activity in mismatch repair-deficient (dMMR) or microsatellite instability-high (MSI-H), locally advanced colorectal cancer. Preclinical studies suggest that COX-2 inhibition might modulate the inflammatory tumour microenvironment and augment the effect of PD-1 blockade. We aimed to investigate whether the addition of the COX-2 inhibitor celecoxib to neoadjuvant toripalimab would increase the pathological complete response in this population.
Methods: PICC-2 was a multicentre, open-label, randomised, controlled, phase 2 trial conducted at three academic hospitals in China. Eligible patients were aged 18–75 years; had histologically confirmed dMMR or MSI-H colorectal cancer, of clinical stage T3–T4 or any clinical T stage with lymph node positivity (N+); had an Eastern Cooperative Oncology Group performance status score of 0 or 1; and had adequate haematological, hepatic, and renal function. Participants were randomly assigned (1:1) via an interactive web response system, stratified by tumour location and clinical T stage, to receive neoadjuvant toripalimab plus celecoxib or toripalimab monotherapy every 14 days for 12 cycles, followed by surgery. Toripalimab 3 mg/kg was administered intravenously on day 1 in both groups; patients in the toripalimab plus celecoxib group also received celecoxib 200 mg orally twice daily on days 1–14. The primary endpoint was the proportion of patients with pathological complete response, defined as no presence of residual viable tumour in the primary tumour and all sampled lymph nodes at surgery, assessed by central blinded independent pathological review in the intention-to-treat population. Safety was assessed in all patients who received at least one dose of study treatment. This study is registered with ClinicalTrials.gov, NCT03926338, and is ongoing.
Findings: Between May 5, 2022, and Jan 20, 2025, 110 patients were randomly assigned to toripalimab plus celecoxib (n=55) or toripalimab monotherapy (n=55). Overall, 65 (59%) patients were male, all patients were Chinese, 76 (69%) had cT4 tumours, and 105 (95%) had clinically node-positive disease. At the data cutoff date (Oct 10, 2025), median follow-up was 18·1 months (IQR 11·5–25·3). 49 (89%) of 55 patients in each group completed all 12 planned cycles of neoadjuvant therapy. Surgery was done in 53 (96%) of 55 patients in the toripalimab plus celecoxib group and 51 (93%) of 55 in the monotherapy group. Pathological complete response was observed in 49 of 55 patients (89% [95% CI 78–96]) in the toripalimab plus celecoxib group versus 38 of 55 (69% [55–81]) in the monotherapy group (between-group difference 19 percentage points [95% CI 4–34]; p=0·014). Grade 3 treatment-related adverse events occurred in three (5%) patients and four (7%) patients, respectively; grade 3 treatment-related adverse events were tumour perforation (two [4%]) and bowel obstruction (one [2%]) in the toripalimab plus celecoxib group, and rash (one [2%]), tumour perforation (one [2%]), increased aminotransferase (one [2%]), and hypothyroidism (one [2%]) in the monotherapy group. No grade 4 or 5 treatment-related adverse events occurred.
Interpretation: In patients with dMMR or MSI-H locally advanced colorectal cancer, neoadjuvant toripalimab plus celecoxib significantly increased the proportion of patients attaining pathological complete response compared with toripalimab monotherapy, with a similar safety profile. These findings support further investigation of this combination strategy in larger phase 3 trials.
The Lancet Oncology , résumé, 2026