AFNT-211: An FAS-41BB–enhanced TCR-T cell therapy with stem-like properties targeting KRAS G12V-expressing solid tumors.
Authors: Hoffmann Michele , Brown Lauren , Campbell Martin , Pechhold Klaus , He Xingyue , Lee Joseph , Qu Hongjing , Liang Jinsheng , Chapuis Aude , Greenberg Philip D , Nagorsen Dirk , Vallaster Markus P , Canestraro Martina , Lam Hubert , Shapiro Gary , Hallet Damien , Nguyen Kim , Vincent Loic , Schmitt Thomas 
Published: June 2023

2543 Background: KRAS is the most common oncogenic driver mutation in solid tumors, promoting the initiation and progression of many uncurable cancers, including colorectal, pancreatic and lung cancer. While small molecule inhibitors to KRASG12C mutations have been approved, there are no targeted therapies available for patients with highly prevalent KRASG12V mutations. TCR-T cell therapies have demonstrated remarkable responses in clinical trials, but their durability has been limited by the immunosuppressive tumor microenvironment (TME). AFNT-211 is an autologous T cell therapy engineered to express an HLA-A*11:01 KRASG12V-specific TCR, further enhanced with CD8α/β coreceptor and a FAS-41BB switch receptor to drive T cell persistence and durable clinical responses. CD8α/β coreceptor enables a coordinated CD4+/CD8+ T cell response and FAS-41BB converts the FAS ligand (FASL) TME death signal into a costimulatory signal through 41BB activation. Methods: AFNT-211 was assessed for efficacy in vitro against a panel of KRASG12V-expressing tumor cell lines and in vivo using human xenograft mouse models. In vitro safety studies were performed to assess potential cross-reactivity, alloreactivity, and cytokine-independent growth. The clinical manufacturing process consists of autologous CD4+/CD8+ T cells transduced with lentivirus and expanded using culture conditions that drive robust expansion while preserving stem-like properties. Phenotypic and functional analyses of AFNT-211 were performed using flow cytometry and cell-based assays. Results: Coculture of AFNT-211 with a panel of KRASG12V-expressing tumor cell lines led to significant effector cytokine secretion, T cell proliferation, and tumor cell killing. The CD8α/β coreceptor enabled CD4+ T cell recognition of KRASG12V and greater overall cytotoxicity. The FAS-41BB switch receptor dramatically augmented the magnitude and durability of the anti-tumor response against FASL-expressing tumor cells. XScan mutagenesis and potential off-target peptide testing revealed no significant cross-reactivities. No alloreactivity was observed against a panel of lymphoblastoid cell lines presenting the most frequent HLA types in the US population. Potent anti-tumor response was observed in vivo in a mouse xenograft model. Affini-T’s Thrive manufacturing platform used for the production of AFNT-211 consistently delivers >30-40e9 TCR-engineered T cells with a high frequency of naïve and central memory T cells expressing negligible markers of exhaustion. Conclusions: The AFNT-211 manufacturing process generates a large number of TCR-T cells with desirable stem-like properties optimized for clinical dosing. Preclinical data demonstrated a potent and safe profile for AFNT-211 that supports clinical development in HLA-A*11:01 patients with advanced/metastatic solid tumors harboring a KRAS G12V mutation.