Forlong Announces Completion of Phase I Clinical Studies of FL115 Monotherapy (IV): Disease Control for 3 Heavily-pretreated Patients with Advanced Solid Tumors over 12 Months

SHANGHAI & SUZHOU, China--(BUSINESS WIRE)--Forlong Biotechnology, a clinical-stage biotech company focusing on developing transformative cytokine therapies for patients with severe unmet needs, today announced that Phase I clinical studies of FL115, an IL-15 superagonist, as monotherapy via intravenous infusion in patients with advanced solid tumors have been completed, with durable treatment effects observed in 2 patients with confirmed partial response (cPR) and 1 patient with stable disease (SD).

Phase I clinical studies of FL115 were conducted in US and China in parallel:

FL115-101 Study was conducted in US, with 11 patients treated. One patient with advanced cervical cancer and 4 prior therapies received the 1^st dose in July 2024, and achieved SD. The patient was rolled off the study in Sept 2025, and continue to receive the FL115 treatment under a Single Patient IND Protocol/Treatment Plan. Data from this study will be presented at the upcoming 2026 American Society of Clinical Oncology (ASCO) Annual Meeting (Poster Board: 291; Session Type/Title: Developmental Therapeutics—Molecularly Targeted Agents and Tumor Biology; Date and Time: May 30, 2026, 1:30 PM-4:30 PM CDT)

FL115-102 Study was conducted in China, with 23 patients treated. One patient with highly invasive NUT-NSCLC and 3 lines of prior therapies received the 1^st dose of FL115 in Apr 2025, and achieved cPR. Another patient with lymphoepithelial carcinoma (parotid gland) and 4 lines of prior therapies received the 1^st dose of FL115 in Jun 2025, and achieved cPR. Both patients have been rolled off the study respectively in March and May 2026, and continue to receive the FL115 under a Compassionate Treatment program. Data from this study was presented as a Late-breaking Abstract at 40th SITC Annual Meeting.

FL115 (IV) is currently being investigated in combination with an anti-PD1 monoclonal antibody in a Phase 1b/2 clinical trial in patients with advanced solid tumors. Preclinical data regarding FL115 (Subcutaneous Injection) was presented at the 2026 AACR Annual Meeting, and a Phase 1 clinical study will be initiated in 2H 2026 to evaluate FL115 (Subcutaneous Injection) in patients with advanced solid tumors. In parallel, FL115 (Intravesicale Delivery) is currently being investigated in combination with Bacillus Calmette-Guérin (BCG) in a Phase 2 clinical trial in patients with nonmuscle invasive bladder cancer (NMIBC).

“We deeply appreciate the commitment and support from the patients and their families,” said Dong Wei, Ph.D., Chief Executive Officer of Forlong Biotechnology, “With favorable safety, preliminary efficacy and duration of response observed in Phase 1 clinical studies, FL115 continues to show its potential as Best-in-class IL-15 superagonist. We are advancing FL115 for multiple indications via different delivery routes, aiming to develop optimal treatment options for cancer patients in need.”

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.