Phase II Clinical Trial Results of Recombinant Human Hepatocyte Growth Factor Plasmid Injection (NL003) for Critical Limb Ischemia Published in Molecular Therapy

Recently, the Phase II clinical trial results of the gene therapy drug “Recombinant Human Hepatocyte Growth Factor Naked Plasmid Injection” (NL003), developed by Beijing Northland Biotechnology Co., Ltd., for the treatment of critical limb ischemia (CLI), were published in Molecular Therapy, Volume 27, Issue 12 (pages 2158–2165). The journal is sponsored by the American Society of Gene & Cell Therapy and primarily publishes significant research findings in the field of molecular therapeutics. Its 2018 impact factor was 8.402.

This study adopted a randomized, double-blind, multicenter, placebo-controlled design. A total of 200 subjects with critical limb ischemia (CLI) were randomly enrolled across nine research centers in China, with 50 subjects assigned to each of the high-dose, medium-dose, low-dose, and placebo groups. The observation period was 180 days. The primary endpoints were the rate of complete pain resolution and the rate of complete ulcer healing, and adverse reactions were evaluated. This clinical study received funding support from the National “Major New Drug Creation” Program on two occasions.

Phase II study results demonstrated: In terms of efficacy, all dosing groups showed significant pain relief compared to the placebo group (p<0.05); on Day 180, the rate of complete resolution of rest pain without the use of analgesics showed a statistically significant difference compared to the placebo group (p<0.05); regarding the rate of complete ulcer healing, the high-dose group achieved 66.67%, which was statistically significantly different from the 27.27% observed in the placebo group (p=0.0243). In terms of safety, there were no significant differences between the dosing groups and the placebo group in the incidence of adverse events (AEs), serious adverse events (SAEs), or local injection site reactions; no SAEs related to the investigational drug occurred. Among the published results of similar investigational drugs, this is the first instance where positive results have been simultaneously achieved for both the rate of complete resolution of rest pain (a primary clinical symptom of CLI) and the rate of complete ulcer healing. The trial results indicate that the drug has a high level of safety and demonstrates good therapeutic efficacy for severe lower extremity arterial ischemic disease, providing a basis for conducting Phase III clinical studies.

NL003 is a naked plasmid gene therapy drug constructed using a highly efficient pCK vector and a modified human HGF gene sequence. Following intramuscular injection into the ischemic region of the affected limb, it transfects skeletal muscle cells to simultaneously express and secrete two naturally occurring human HGF protein isoforms, HGF723 and HGF728. The HGF protein promotes the proliferation and migration of vascular endothelial cells as well as the migration of arterial smooth muscle cells, thereby facilitating angiogenesis at the ischemic site, establishing microvascular collateral circulation, and achieving the therapeutic goal of treating limb ischemic diseases. It is indicated for the treatment of critical limb ischemia (CLI) and can also be used for conditions such as diabetic peripheral neuropathy (DPN).

In this Phase II study, the investigational product was administered via multi-point intramuscular injection into the affected limb on Days 0, 14, and 28 post-randomization. Unlike the fixed-site administration commonly used for similar gene therapy products in all subjects, this approach required angiographic localization of diseased vessels and ischemic regions. Injections were targeted to specific muscle sites that were anatomically more favorable for collateral circulation establishment based on the vascular status of the affected limb. This method is more conducive to promoting angiogenesis and the formation of collateral circulation compared to fixed-site administration.

Critical Limb Ischemia (CLI) represents the most severe stage of ischemia caused by insufficient blood supply to the limbs due to factors such as lower extremity atherosclerosis, thromboangiitis obliterans, and diabetic lower extremity ischemia. Its main clinical manifestations include reduced walking ability, rest pain, and ulcers, which significantly impair patients’ quality of life. Currently, there are no effective pharmacological treatments for CLI available worldwide; clinical management primarily relies on surgical revascularization through percutaneous interventions and bypass surgery. According to overseas literature, approximately 20–30% of patients are unable to undergo surgical revascularization due to advanced age, frailty, poor vascular conditions, and various comorbidities. Among patients without effective treatment options, the rate of direct progression to amputation can reach 40%, and the one-year mortality rate exceeds 20%. Based on forecasts from the SAGE GROUP’s 2017 consulting report, the number of CLI patients in China ranges from 5.6 to 6.3 million. With the aging population and the increasing number of individuals exposed to risk factors such as hypertension, hyperlipidemia, diabetes, and smoking, the prevalence of CLI is on the rise, indicating a significant unmet medical need in this field.

In the same issue, the journal published an editorial titled “Gene Therapy for CLI Enters Clinical Application,” which gave a positive evaluation of the trial results. The authors stated: “CLI is a major global health concern. It is highly significant that the investigational drug achieved definitive positive results in a randomized, blinded, controlled study. Although there are still aspects regarding the mechanism of action and clinical administration strategies that require further validation, the published results of this HGF naked plasmid gene therapy study bring hope to patients who currently lack suitable therapeutic options.”

Currently, the Phase III clinical study of the investigational drug was officially launched in July 2019 at the lead site, Peking Union Medical College Hospital. By the end of 2019, a total of nine centers had been sequentially activated, and the trial is progressing smoothly.

Original Title: Phase II Clinical Trial Results of “Recombinant Human Hepatocyte Growth Factor Naked Plasmid Injection” Published in Molecular Therapy