A-1331852

By enabling automated analysis of FRET images, FRET-SAM significantly enhances the efficiency and accuracy of FRET two-hybrid assays, while eliminating subjective bias. The capability of FRET-SAM to resolve drug-target interactions establishes it as a promising tool for drug discovery.

Dormancy was induced with low-dose FAC (5-Fluorouracil, Adriamycin, Cyclophosphamide). Notably, disseminated cell frequency inversely correlated with primary tumor size during neoadjuvant chemotherapy, underscoring the need for systemic therapies targeting distant dormant cells. These findings identify Bcl-xL as a central survival factor in chemotherapy-induced dormancy, and suggest that tumor-targeted systemic delivery of A-1331852 may eradicate disseminated dormant cells and prevent metastatic relapse in high-risk TNBC.

The FRET-HBTDS method was performed on the FRETscope with a 20× objective for the cells co-expressing CFP-Bcl-xL and YFP-Bak to assess the action of eight compounds (A1331852, S63845, AC, DSF/Cu, Met, REGO, SOFA, ABT199) on the interaction between Bcl-xL and Bak. Our data firmly demonstrate that A1331852 unlocks the binding state of Bcl-xL and Bak, while DSF/Cu modifies the structure of the Bcl-xL-Bak complex. These findings demonstrate that FRET-HBTDS can be used to assess the efficacy of a drug by revealing the binding state and complex molecular structure of the target proteins using FRET technology in living cells, which may be a potential targeted drug screening method.

Mnt deletion provoked the apoptosis of MLL::AF9 AML cells in vitro and increased apoptosis elicited by the BH3 (BCL-2 homology region 3) mimetic drugs S63845 (MCL-1 (Myeloid cell leukemia-1) specific), ABT-199/Venetoclax (BCL-2 (B-cell lymphoma-2) specific), and A-1331852 (BCL-XL (B-cell lymphoma-extra large) specific). Of note, inducing MNT deletion in a human MLL-rearranged AML cell line transplanted into NSG (NOD SCID Gamma) mice debulked established leukemia and significantly extended the survival of transplant recipients. Taken together with previous studies that demonstrated a critical role for MNT in the development and sustained expansion of B and T lymphomas, our results suggest that a small molecule inhibiting MNT function may be a valuable therapeutic agent for myeloid and lymphoid malignancies.

Here, we investigated the underlying mechanisms of inherent resistance to the BCL2i ABT-199 and BCL-XL inhibitor A1331852, focusing on the roles of the principal pro-apoptotic BH3-only proteins NOXA and BIM. Resistance to BCL2i and BCL-XL inhibitors was abrogated by suppression of MCL1 expression. In conclusion, we show that NOXA is essential for the effectiveness of BH3-mimetics targeting BCL2/BCL-XL; in the absence of NOXA, BIM displaced from BCL2/BCL-XL can be bound by MCL1.

In preclinical models, the small-molecule inhibitor A-1331852 (targeting ARL3) potently suppresses ERα-positive tumor growth and synergizes with endocrine therapies. These findings establish ARL3 as a critical regulator of ERα homeostasis via USP10, highlighting its dual role as a biomarker and ARL3-targeted therapeutic for ERα-positive breast cancer.

To induce sensitivity, we treated MIK665-resistant samples with ABCB1 inhibitors elacridar or tariquidar, BCL-XL inhibitor A1331852, or BCL-2 inhibitor venetoclax in combination with MIK665. Additionally, the combination of MIK665 with venetoclax restored sensitivity in samples with primary venetoclax resistance. Overall, this study indicates that elevated ABCB1 expression is a potentially targetable resistance mechanism in the context of MIK665 resistance, and that a combination of MIK665 with venetoclax may be effective for overcoming resistance to either MCL-1 or BCL-2 inhibition.

Lastly, we found enhanced in vivo antitumor activity in mCRPC by combining the clinically relevant agents B7-H3-seco-DUBA (vobramitamab duocarmazine) and A-1331852. Collectively, our findings provide rationale for the development of ADC therapies combining genotoxic payloads with Bcl-xL inhibitors for mCRPC. B7-H3, PSMA, and STEAP1 targeted ADC therapies combining genotoxic payloads with Bcl-xL inhibitors induce p53-dependant apoptotic cell death in mCRPC, providing a clinically viable strategy for the treatment of advanced prostate cancer.

We combined A-1331852 and S63845 with IKE or RSL3 (ferroptosis-inducing drugs). These data indicate that BCL-xL maintains ChRCC cell survival by suppressing apoptosis. The BCL-xL-specific PROTAC DT2216, currently in clinical trials, may provide an opportunity for ChRCC therapy.

Patients often develop resistance to next-generation hormonal therapies that target the AR-axis (e.g., abiraterone, enzalutamide)...Combinations targeting Bcl-xL (A-1331852 and navitoclax) and Mcl-1 (S63845) synergistically decreased cell viability and induced apoptotic activity via cleavage of PARP, caspase 3, and caspase 7 across AR-V7 expressing CRPC cell lines (LNCaP95, VCaP-CR, 22Rv1) and a patient-derived organoid model (LuCaP 167 CR)...We showed similar synergistic efficacy with the Bcl-xL targeting PROTAC in combination with S63845 in the 3D spheroid models. Our findings support further preclinical development of Bcl-xL and Mcl-1 inhibitors for mCRPC.

Using flow cytometry and single-cell RNA sequencing of the tumor microenvironment, we found that the broad activity of the triple therapy relied on the expansion of T and NK cells with cytotoxic potential, an increase in the M1/M2 macrophage ratio, and a reduction of immunosuppressive Treg cells, dendritic cells, and B lymphocytes. In conclusion, we report a novel regimen combining epigenetic and BCL-XL inhibitors with ICB that produces potent anti-tumor responses in multiple preclinical models of solid tumors.

In this study, XZ338, a highly potent and selective BCL-XL degrader derived from BCL-XL specific inhibitor A-1331852, was generated. XZ338 is 70-fold more potent than ABT-263 against MOLT-4 T-ALL cells, with over 89-fold selectivity for MOLT-4 cells over human platelets.