On May 27, 2026 Forlong Biotechnology, a clinical-stage biotech company focusing on developing transformative cytokine therapies for patients with severe unmet needs, reported 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).

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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 1st 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) (Free ASCO Whitepaper) 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 1st dose of FL115 in Apr 2025, and achieved cPR. Another patient with lymphoepithelial carcinoma (parotid gland) and 4 lines of prior therapies received the 1st 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 (Free SITC Whitepaper) 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 (Free AACR Whitepaper) 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.

(Press release, Forlong Biotechnology, MAY 27, 2026, View Source [SID1234666121])