Forlong Biotechnology, a clinical-stage biotech company focusing on developing transformative cytokine therapies for patients with severe unmet needs, today announced that the first patient has been treated in a Phase 2 clinical trial investigating FL115 in combination with Bacillus Calmette-Guérin (BCG). The study will assess the anti-tumor effect of the combination therapy, including Complete Response Rate and Duration for carcinoma in situ (CIS) NMIBC patients, and Disease Free Survival and Relapse Free Survival for papillary (Ta/T1) NMIBC patients.

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. The start of the Phase 2 clinical trial builds on positive data from the Phase 1 trial where FL115 demonstrated favorable safety and efficacy in the same patient population. As a monotherapy at the recommended dose for expansion, 4/6 patients achieved responses longer than 3 months, of which 2 patients achieving responses longer than 9 months. This dose of FL115 in combination with BCG will be investigated in the Phase 2 trial.

“Dosing the first patient in our Phase 2 trial for FL115 marks a defining moment for Forlong, as we advance our lead candidate further into clinical development and continue to validate the potential of our synthetic immunology platforms,” said Dong Wei, Ph.D., Chief Executive Officer of Forlong Biotechnology, “FL115 stands out with favorable safety and preliminary efficacy observed in multiple Phase 1 clinical studies in advanced solid tumors and NMIBC. With FL115 interim data for advanced solid tumor to be presented as Late Breaking Abstract on Nov 8 at the 40^th Annual Meeting of the Society for Immunotherapy of Cancer (SITC 2025), this trial gives us the opportunity to further validate FL115 as potential Best-in-class IL-15 superagonist, and bring new treatment options for cancer patients in need.”

The Phase 2 clinical trial plans to enroll three arms: BCG unresponsive CIS NMIBC patients, BCG unresponsive high risk papillary NMIBC patients, and BCG naïve medium/high risk NMIBC patients. The trial will be conducted at over 15 investigator sites in China.

About FL-115

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 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. Its lead 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 Bacillus Calmette-Guérin (BCG) in Phase II for patients with nonmuscle invasive bladder cancer (NMIBC). Its second candidate FL116 is a PD-1 antibody fused with interleukin-15 (IL-18) mutein which is engineered to bind IL-18 receptor and not IL-18BP, and has demonstrated potent tumor-killing efficacy in multiple in vivo tumor models resistant to immune checkpoint inhibitors.

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