Strategy to enhance radiosensitivity with low-dose radiation targeting pMMR rectal cancer, an immune blind spot

Patients with mismatch repair proficient (pMMR)/microsatellite stable (MSS) locally advanced rectal cancer (LARC), which accounts for over 90% of cases, show almost no response to single-agent immune checkpoint inhibitors due to a low mutation burden. Researchers at Sun Yat-sen University Cancer Center (SYSUCC) have introduced a strategy using low-dose radiation therapy (LDRT) as a catalyst to induce immune sensitivity to overcome immune resistance. The principle involves low-dose radiation promoting immunogenic cell death (ICD) within the tumor microenvironment, converting 'cold tumors' into 'hot tumors' with activated immune responses. This Phase 2 trial (NCT07448142) is designed to maximize anticancer synergy with the PD-1 inhibitor Pucotenlimab through 4Gy and 10Gy fractionated doses while minimizing damage to normal tissues.

Expansion of Indications and Combination Design for Lepu Biopharma's Fuyuhang (HX008)

Pucotenlimab (brand name: Fuyuhang, development code: HX008), used in the trial, is a humanized IgG4 monoclonal antibody developed by Hong Kong-listed Lepu Biopharma (2157.HK) that received China NMPA approval in 2022. Researchers are inducing a systemic immune response by combining 200mg of Pucotenlimab with the standard cytotoxic chemotherapy CAPEOX (capecitabine/oxaliplatin) in 3-week cycles. A precision response-adaptive protocol was applied, in which the decision to administer an additional 3–4 cycles was based on tumor response after two cycles. This is an attempt to expand the treatment scope for existing immunotherapy-refractory colorectal cancer by organically combining immunogenic chemotherapy and radiation priming.

Verifying the 'Watch-and-Wait' paradigm for organ preservation, replacing radical surgery

The primary endpoint of this trial is set as a composite complete response rate, encompassing clinical complete response (cCR) and pathological complete response (pCR), evaluating 50 enrolled patients. Patients judged as cCR, where the tumor has completely disappeared via MRI and endoscopy after treatment, will transition to non-surgical 'Watch-and-Wait' management instead of invasive total mesorectal excision (TME). This can prevent complications such as stoma formation or bowel dysfunction associated with standard radical surgery and fully preserve the patient's quality of life. The goal is to establish a new treatment standard that minimizes unnecessary surgical intervention and maximizes organ preservation rates.

Potential to Reshape the Standard of Care in the $150 Billion Colorectal Cancer Market

The global colorectal cancer therapeutics market is a massive market projected to reach approximately $150 billion by 2026 and exceed $200 billion in the future. In the dMMR setting, GSK's Jemperli (generic name: dostarlimab) achieved a 100% complete response rate as neoadjuvant monotherapy; however, high-dose total neoadjuvant therapy (TNT) remains the standard of care for the vast majority pMMR market. If the high complete response rate of low-dose radiation combination therapy is confirmed in this trial, it could establish a next-generation neoadjuvant treatment paradigm that avoids high-dose radiation toxicity. This holds strategic significance in reducing dependence on expensive high-dose radiation equipment and significantly expanding the prescription scope of immunotherapy to refractory solid tumors.