ALDH1A3-IN-1 (Compound 14) is a potent ALDH1A3 inhibitor (antagonist) with IC50 of 0.63 µM and Ki of 0.46 µM. ALDH1A3-IN-1 may be utilized to study prostate cancer.
ALDH1A3-IN-1 (Compound 14) is a potent and selective inhibitor of aldehyde dehydrogenase 1 family member A3 (ALDH1A3), an enzyme overexpressed in cancer stem cells, particularly in prostate and glioblastoma. It inhibits ALDH1A3 with an IC50 of 0.63 uM and a Ki of 0.46 uM and exhibits anti-proliferative activity against prostate cancer cells. Target: ALDH1A3 (Aldehyde Dehydrogenase 1 Family Member A3, IC50 = 0.63 uM, Ki = 0.46 uM). ALDH1A3-IN-1 binds to the active site of ALDH1A3, inhibiting the conversion of aldehydes to carboxylic acids. This depletes NAD+, induces oxidative stress, and suppresses cancer stem cell self-renewal, proliferation, and tumor-initiating capacity. In vitro, in prostate cancer cell lines (e.g., LNCaP, PC-3), ALDH1A3-IN-1 (0-200 uM, 96 h) exhibits dose-dependent anti-proliferative activity. In primary prostate cells, it reduces cell viability at 0-200 uM over 72 h. ALDH1A3-IN-1 also decreases ALDH activity, as measured by the ALDEFLUOR assay, and reduces spheroid formation in stem cell-enriched cultures. No in vivo efficacy data have been published specifically for ALDH1A3-IN-1 in animal models. Based on its mechanism, it is expected to reduce tumor growth and prevent recurrence in prostate cancer xenograft models and ALDH1A3-expressing glioblastoma models. For cell-free ALDH1A3 enzyme inhibition assay: recombinant human ALDH1A3 enzyme (50 ng) is incubated with varying concentrations of ALDH1A3-IN-1 (0-200 uM) and aldehyde substrate (e.g., benzaldehyde or all-trans-retinal) in the presence of NAD+ in 100 uL assay buffer (100 mM sodium phosphate, pH 7.5, 1 mM DTT, 1 mM EDTA) for 5-10 min at 25degC. NADH fluorescence is measured at excitation 340 nm, emission 460 nm. IC50 is calculated from dose-response curves. For cell-based assays: prostate cancer cells (e.g., LNCaP, PC-3) are seeded in 96-well plates and treated with ALDH1A3-IN-1 (0-200 uM) for 72-96 h. Cell viability is measured by MTT or CellTiter-Glo assay. ALDH activity is measured by ALDEFLUOR assay according to manufacturer instructions. For animal studies: potential in vivo protocol in nude mouse prostate cancer xenograft model: mice with established subcutaneous PC-3 tumors are treated with ALDH1A3-IN-1 (25-100 mg/kg, IP or oral daily) for 3-4 weeks. Tumor volume is measured by calipers. Tumor stem cell population (ALDH-positive cells) is analyzed by flow cytometry at study end. No PK data are available for ALDH1A3-IN-1. For small molecule ALDH1A3 inhibitors (MW 284.2 for free base), predicted PK in rodents: moderate oral bioavailability, Tmax 1-2 h, half-life 4-6 h, moderate plasma protein binding, and liver metabolism via phase I/II enzymes. No toxicity data have been reported. ALDH1A3 is involved in retinoic acid biosynthesis; inhibition may cause retinoid deficiency-like effects: impaired vision, skin abnormalities, and developmental toxicity. No acute toxicity studies have been published. ALDH1A3-IN-1 is a research compound not yet approved for clinical use. It is used as a chemical probe to study the role of ALDH1A3 in cancer stem cell biology and to validate ALDH1A3 as a therapeutic target for preventing cancer recurrence and overcoming chemoresistance, particularly in prostate and glioblastoma multiforme.

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