Efficacy and safety of toripalimab with fruquintinib in the third-line treatment of refractory advanced metastatic colorectal cancer: results of a single-arm, single-center, prospective, phase II clinical study

Abstract

Background: The most effective treatment with immune checkpoint inhibitors (ICIs) is limited to the microsatellite instability high (MSI-H) subgroup of advanced colorectal cancer. ICIs are completely ineffective in microsatellite stabilized (MSS) patients with advanced colorectal cancer. Fruquintinib, a tyrosine kinase inhibitor (TKI) domestically made in China that specifically inhibits vascular endothelial growth factor receptors, is used to treat refractory metastatic colorectal cancer (mCRC). Researches showed that anti-angiogenic therapy combined with immunotherapy induces a long-lasting antitumor immune response. Here, we aimed to evaluate antitumor efficacy and safety of fruquintinib with anti-programmed death-1 (PD-1) antibody toripalimab in Chinese patients with non-MSI-H/mismatch repair proficient (pMMR) mCRC.

Methods: This was a single-arm, single-center, prospective, phase II clinical trial. A total of 19 MSS patients with refractory or advanced mCRC were enrolled They received fruquintinib (5 mg, orally, once daily for 3 weeks followed by 1 week off in 4-week cycles) and toripalimab (240 mg, intravenously administered on day 1 once every 3 weeks) until disease progression or unacceptable toxicity. The objective response rate (ORR), progression-free survival (PFS), overall survival (OS), 1-year PFS rate, disease control rate (DCR), and toxicity were reviewed and evaluated. The Cox regression model was used to analyze the influence on OS and PFS.

Results: Among the 19 patients, the median age was 52 years (range, 30-71 years); 4 patients (21.05%) achieved partial response, 10 patients (52.63%) experienced stable disease, and 4 patients (21.05%) experienced progressive disease. The ORR was 21.05%. The median PFS and OS were 5.98 months and 11.10 months, respectively. Patients with peritoneal metastasis received greater benefit from combination therapy, with a longer PFS (P=0.043) in the univariate analysis. The most common treatment-related adverse reactions were fatigue (57.89%), hepatic dysfunction (42.11%) and hypertension (36.84%). No serious adverse effects or adverse effect-related deaths were reported.

Conclusions: Our study provides evidence supporting fruquintinib combined with an anti-PD-1 monoclonal antibody have the better effect than fruquintinib alone in the third-line setting for Chinese patients with MSS advanced colorectal cancer. Primary lesion excision and peritoneal metastasis were independent prognostic factors of PFS. Further well-designed, prospective, large-scale studies are needed to validate this outcome.

Keywords: Fruquintinib; anti-programmed death-1 (PD-1) inhibitors; metastatic colorectal cancer (mCRC); non-microsatellite instability high/mismatch repair proficient (non-MSI-H/pMMR).

Figure 1

The combined therapeutic response was measured by contrast-enhanced CT/MRI and was calculated according to tumor thickness diameter ratio before and after treatment. (A) A waterfall plot of tumor response in all 19 patients; (B) swimmer plot of tumor response in all 19 patients. BOR, best overall response; PR, partial response; SD, stable disease; PD, progressive disease; NE, not evaluated.

Figure 2

PFS, OS and DOR curves of patients with advanced CRC treated with toripalimab and fruquintinib. (A) The mOS of the combined treatment, (B) the mPFS of the combined treatment, and (C) the mDOR in the combined treatment. OS, overall survival; mOS, median overall survival; CI, confidence interval; PFS, progression-free survival; mPFS, median progression free survival; DOR, duration of response; mDOR, median duration of response; NA, not arrived.