Abstract 406: Discovery of potent and selective TRIB2 inhibitors with therapeutic efficacy in therapy-resistant neuroendocrine prostate cancer.

Abstract Background: Lineage plasticity and therapy resistance remain major challenges in advanced prostate cancer, where a subset of tumors evade androgen receptor (AR)-targeted therapy and acquire neuroendocrine (NE) features. Neuroendocrine prostate cancer (NEPC), whether arising de novo or following antiandrogen treatment, is highly aggressive and lacks effective targeted therapies. We previously identified the pseudokinase TRIB2 as a critical regulator of enzalutamide resistance, lineage plasticity, and tumor survival, establishing it as a potential therapeutic target. However, no TRIB2 inhibitors are currently available for clinical use, underscoring the need for therapeutic development. Methods: Using structure-guided in-silico modeling, cell-based screening, and biochemical validation, we identified and optimized TRIB2-targeting small molecules. The lead compound, TBI-001, was evaluated for target engagement, specificity, and functional efficacy. Downstream signaling, phenotypic changes, viability, and apoptosis were evaluated in antiandrogen-resistant and NEPC cell models, as well as engineered cells with TRIB2 overexpression (e.g., LNCaP-TRIB2, RWPE1-TRIB2) using western blotting, IHC, and functional assays. Drug metabolism and pharmacokinetics were examined in preclinical models. Results: TBI-001 is a potent and bioavailable TRIB2 inhibitor that directly binds TRIB2, induces its protein degradation, and suppresses downstream survival signaling, including pAKT and BCL2. TBI-001 broadly inhibited TRIB2-regulated NE and lineage-plasticity programs, including epigenetic and transcriptional regulators (EZH2, BRD4, SOX2, NMYC), canonical NE transcription factors (ASCL1, BRN2), the NE antigen DLL3, and the effector PEG10. Importantly, TBI-001 reduced CD56 (NCAM1), a NEPC surface marker linked to lineage plasticity, metastasis, and immune evasion, as well as the immune-modulatory molecule B7-H3 (CD276), indicating effects on both NE differentiation and immune-evasive signaling. Functionally, TBI-001 markedly reduced viability and induced apoptosis in antiandrogen-resistant prostate cancer cell lines and NEPC models (NCI-H660, LASCPC-01), while demonstrating limited effects in control epithelial cells. In vivo, TBI-001 treatment led to significant tumor regression in therapy-resistant NEPC xenograft models, decreased NE marker expression, and showed no observable toxicity. Metabolic profiling in human hepatocytes confirmed efficient hepatic metabolism and favorable stability. Conclusions: These findings establish that pharmacologic targeting of TRIB2 with TBI-001 disrupts oncogenic signaling and neuroendocrine programs that drive aggressive prostate cancer behavior. TBI-001 demonstrates strong anti-tumor activity, favorable tolerability, and promising pharmacologic profile, supporting its advancement toward clinical development as TRIB2-targeted therapy for advanced, therapy-resistant prostate cancer. Citation Format: Jitender Monga, Sang-Yoon Lee, Sharad K. Suthar, Sudha Sadasivan, Shirish Gadgeel, Craig Rogers. Discovery of potent and selective TRIB2 inhibitors with therapeutic efficacy in therapy-resistant neuroendocrine prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 406.