Abstract A096: Discovery of a covalent allosteric inhibitor targeting AKT1 E17K for the treatment of solid tumors

Abstract Background A recurrent mutation in AKT1, E17K, acts as a primary oncogenic driver in select solid tumors, including breast, endometrial cancers and prostate, by promoting constitutive membrane localization and sustained kinase activation. While pan-AKT inhibitors have demonstrated clinical activity, their lack of wild-type and isoform selectivity often results in dose-limiting toxicities, such as hyperglycemia, diarrhea, and rash, that limit efficacy and tolerability. To address these limitations, we developed REZO-001, a mutant-selective covalent allosteric inhibitor designed to achieve potent, sustained inhibition of AKT1 E17K while minimizing toxicity through sparing of wild-type AKT isoforms. Methods Compounds were evaluated through a comprehensive series of assays designed to assess biochemical potency, cellular activity, and covalent engagement of the AKT1 E17K mutant. Selectivity was characterized across wild-type isoforms, as well as through broad kinase profiling, cancer cell panels, and safety pharmacology assessments. Pharmacokinetic studies were conducted to determine compound exposure and half-life. Lead candidates demonstrating favorable properties were advanced into in vivo efficacy studies using AKT1 E17K-mutant CDX model. Rezo’s proprietary mass spectrometry (MS) platform was employed to profile compound-induced alterations in the AKT1 E17K interactome, providing mechanistic insight into target engagement and pathway rewiring. Results REZO-001 belongs to a class of potent, reversible covalent inhibitors of AKT1 E17K, demonstrating strong cellular selectivity over wild-type AKT1. REZO-001 and related analogs exhibited rapid and sustained covalent engagement of AKT1 E17K, with >24-hour on-target residence time, while exhibiting minimal binding to, and rapid dissociation from, AKT1 WT and AKT2. Compared to clinical pan-AKT inhibitors, REZO-001 showed a more favorable off-target profile across a broad kinase panel, safety panels, and both cancer and primary cell panels. Accordingly, REZO-001 exhibited minimal inhibition of glucose uptake, a key toxicity associated with AKT2 inhibition. In AKT1 E17K-mutant CDX models, once-daily oral dosing of REZO-001 resulted in robust tumor growth inhibition, with efficacy surpassing that of Capivasertib. The compound demonstrated favorable pharmacokinetics and tolerability, and proteomic profiling using Rezo’s mass spectrometry platform revealed normalization of the aberrant protein–protein interactome of the AKT1 E17K. Conclusions REZO-001 is a potent, mutant-selective covalent inhibitor of AKT1 E17K that demonstrates a differentiated pharmacologic profile. By sparing wild-type AKT isoforms, REZO-001 minimizes off-target toxicity while achieving durable and selective target engagement. These findings support the continued development of REZO-001 as a targeted therapy for patients with AKT1 E17K-mutant tumors. Citation Format: Mengqi Zhong, Subrata Shaw, Keelan Guiley, Man-Tzu Wang, Yueqing Lin, Jason Drummond, Pooja Sharma, Jocelyne Lopez, Daniel Wruck, Chris Adams, Jenna Triplett, Daniela Flores, Fabian Ortega, Hannes Braberg, Ali Bashir, Simranjit Singh, Kevin Hu, Katherine Schutt, Nicholas Hunt, Deidre Johns, Sourav Bandyopadhyay, Christopher Sinz, Cristiana Guiducci. Discovery of a covalent allosteric inhibitor targeting AKT1 E17K for the treatment of solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A096.