Evaluating the safety and efficacy of CRISPR/AaCas12b ^Max -modified tumor infiltrating lymphocytes (GT300) as monotherapy in advanced solid tumors.

5613 Background: Adoptive cell therapy using autologous tumor-infiltrating lymphocytes (TILs) has shown promising results in melanoma patients. However, its effectiveness in other solid tumors, especially "cold" tumors, is still being explored. GT300, a next-generation TIL product, is engineered using CRISPR/AaCas12bMax to disrupt two key immunoregulatory targets identified through genome-wide CRISPR screening. This modification aims to enhance TIL function and overcome the suppressive tumor microenvironment, potentially expanding its use to cold tumors like ovarian and colorectal cancer. Therefore, two studies were initiated to assess the preliminary safety and efficacy of GT300 in advanced solid tumors. Methods: The first-in-class study aims to enroll patients with advanced, treatment-refractory solid tumors, focusing on gynecological cancers. After determining the optimal biological dose (OBD), a monotherapy expansion phase will begin for patients with various solid tumors. Participants undergo nonmyeloablative (NMA) lymphodepletion and receive an infusion of the G300 TIL product, followed by IL-2 administration. Results: As of September 5, 2024, five patients have been enrolled in these two studies, with a median age of 55 years and a median of two prior therapy lines. After FC lymphodepleting chemotherapy, patients received GT300 infusions at doses of ≥1 × 10⁹ viable cells. Four out of five patients subsequently received IL-2. Most adverse events (AEs) were Grade 1 or 2, with Grade 3/4 AEs including fever, rash, dental ulcer, anemia, and decreased platelet count. No DLTs were observed. The ORR was 60% (3/5 evaluable patients). Two patients (40%) achieved CR in cervical cancer and peritoneal papillary serous carcinoma, while one patient (20%) with ovarian cancer had a PR. Despite variations in TIL doses (3.2×10⁹ to 1.90×10¹⁰ cells) and IL-2 regimens (up to 3.0×10⁵ IU/kg), robust TIL proliferation was consistently observed post-infusion. Responders showed biphasic CD45+CD3+ T cell expansion, indicating sustained immune activation. An early increase in IFN-γ levels from days 3 to 10 strongly correlated with positive outcomes, suggesting its potential as an early efficacy biomarker. Conclusions: In patients with previously treated gynecological cancer, GT300, administered after FC lymphodepleting chemotherapy and followed by higher-dose IL-2, exhibited a manageable safety profile. GT300, a CRISPR/Cas9 dual knockout anti-exhaustion TIL product, showed favorable clinical outcomes with a 60% objective ORR, including 40% CR and 20% PR, with no DLTs observed. The infusion led to robust TIL expansion and IFN-γ secretion. These promising results indicate favorable long-term survival outcomes, durable responses, and no long-term safety concerns associated with GT300. Clinical trial information: NCT06145802 , NCT06397963 .