On December 23, 2025 Fapon Biopharma, a biotech in developing therapeutic biologics including cytokine-antibody fusion proteins and T-cell engagers, reported the publication of pioneering research on FP008, a novel fusion protein in Cell Reports Medicine. The peer-reviewed article details the preclinical and translational validation of FP008 (anti-PD-1 × IL-10M). This first-in-class bifunctional fusion protein is designed to address a fundamental limitation in cancer immunotherapy: the inability to reactivate terminally exhausted T cells within tumors.
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Interleukin-10 (IL-10) has shown potential to directly activate and expand exhausted CD8⁺ T cells, but its clinical application has been constrained by dose-limiting hematological toxicities. Fapon’s research team addressed this limitation by engineering IL-10 into a monomeric form (IL-10M). As reported, the engineered IL-10M demonstrated a significant reduction in toxicity. The innovative "cis-delivery" mechanism enabled targeted enrichment of IL-10M onto PD-1-positive exhausted CD8⁺ T cells within the tumor micro-environment. This approach mitigates systemic toxicity while potentially enhancing anti-tumor immune responses.
The study demonstrated FP008’s robust anti-tumor activity across multiple mouse tumor models, including those resistant to anti-PD-1 therapy. FP008 reversed terminal exhaustion of CD8⁺ T cells and restored their functional capacity through localized activation, minimizing systemic exposure.
In comprehensive GLP toxicology studies in cynomolgus monkeys, FP008 exhibited a favorable safety profile at doses up to 10 mg/kg, with no significant hematological adverse events observed. The data supported that this approach has the potential to overcome prior clinical limitations of IL-10-based therapies.
FP008 has cleared an Investigational New Drug (IND) application with the U.S. FDA and China NMPA. Phase I clinical trial is currently ongoing with readout expected later this year. FP008 represents a novel therapeutic strategy for patients with advanced solid tumors refractory to or relapsed from PD-1/PD-L1 checkpoint inhibitors.
(Press release, Fapon Biopharma, DEC 23, 2025, View Source [SID1234661614])