Forlong Biotechnology, a clinical-stage biotech company focusing on developing transformative cytokine therapies for patients with severe unmet needs, today announced that a late-breaking abstract featuring interim safety and efficacy data from a Phase 1 study evaluating the Company’s novel IL-15 superagonist, FL115, has been selected for poster presentation at the 40^th Annual Meeting of the Society for Immunotherapy of Cancer (SITC 2025) being held November 5-9, 2025, in National Harbour, Maryland.

FL115 is an engineered IL-15/IL15Rα-Fbody fusion protein, aiming to enhance anti-tumor immunity via IL-15-mediated signaling on NK and CD8+ T cells while minimizing complexity from Fc. Fbody® is a single-chain Fc designed to eliminate classical Fc effects including ADCC/CDC/ADCP while retaining FcRn engagement. Multiple Phase 1 clinical studies for FL115 as a monotherapy are being completed. FL115 is currently being investigated in combination with Bacillus Calmette-Guérin (BCG) in a Phase 2 clinical trial to evaluate safety and preliminary efficacy in patients with nonmuscle invasive bladder cancer (NMIBC) and in combination with an anti-PD1 monoclonal antibody in a Phase 1b/2 clinical trial to evaluate safety and preliminary efficacy in patients with advanced solid tumors.

“Our mission is to leverage our synthetic immunology platforms to engineer cytokines to fine tune the immune system, providing cancer patients with novel treatment options,” said Dong Wei, Ph.D., Chief Executive Officer of Forlong Biotechnology, “IL-15 has long been believed to be an attractive cytokine for cancer immunotherapy, and fusing Fbody to IL-15/IL15Rα complex presents a differentiated IL-15 superagonist profile for the treatment of solid tumors. We appreciate the opportunity to present initial data from our Phase 1 study of FL115 to leading immuno-oncology experts in this prestigious late-breaking forum.”

Poster Details:

Program: FL115

Poster Title: Preliminary safety, pharmacokinetics, pharmacodynamics and efficacy of FL115, a novel IL-15 superagonist, from a Phase 1 study in patients with advanced solid tumors

Abstract Number: 1334

Presenter: Dong Wei, Ph.D., CEO, Forlong Biotechnology

Date & Time: Saturday, November 8, 2025

About FL115

FL115 is an engineered IL-15/IL15Rα-Fbody fusion protein, aiming to enhance anti-tumor immunity via IL-15-mediated signaling on NK and CD8+ T cells while minimizing complexity from Fc. FL115 has demonstrated significant anti-tumor activities as a monotherapy or as part of combination therapy in vivo, and can be manufactured by a robust and efficient process with excellent product stability. Clinically, FL115 has demonstrated favorable safety profile and preliminary clinical responses as a monotherapy, and has the best-in-class potential to synergize with current and emerging T cell-targeting immunotherapies through combination therapy to significantly improve the treatment outcome for patients. It is currently being investigated in combination with Bacillus Calmette-Guérin (BCG) in a Phase 2 clinical trial to evaluate safety and preliminary efficacy in patients with nonmuscle invasive bladder cancer (NMIBC) and in combination with an anti-PD1 monoclonal antibody in a Phase 1b/2 clinical trial to evaluate safety and preliminary efficacy in patients with advanced solid tumors.

About Forlong Biotechnology

Forlong Biotechnology is a clinical-stage biotech company focusing on developing transformative cytokine therapies for cancer patients with severe unmet needs. It has established four proprietary synthetic immunology platforms: Fbody ® Long-acting Technology Platform, Fc engineering platform, Syntokine® Synthetic Cytokine Platform and AI-driven Intelligent Biomolecular Discovery Platform. The leading candidate FL115 is interleukin-15 (IL-15) superagonist with best-in-class potential, currently being advanced to combo therapy with PD-(L)1 antibodies in Phase I for patients with solid tumors and combo therapy with BCG in Phase II for patients with NMIBC. Its second candidate FL116 is a PD-1 antibody fused with interleukin-18 (IL-18) mutein which is engineered to bind IL-18 receptor and not IL-18BP (a decoy), and has demonstrated potent tumor-killing efficacy in multiple in vivo tumor models resistant to immune checkpoint inhibitors.

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