Methotrexate analogues. 12. Synthesis and biological properties of some aza homologues

Methotrexate-based PROTACs as DHFR-specific chemical probes

Methotrexate (MTX) is a tight-binding dihydrofolate reductase (DHFR) inhibitor, used as both an antineoplastic and immunosuppressant therapeutic. MTX, like folate undergoes folylpolyglutamate synthetase-mediated γ-glutamylation, which affects cellular retention and target specificity. Mechanisms of MTX resistance in cancers include a decrease in MTX poly-γ-glutamylation and an upregulation of DHFR. Here, we report a series of potent MTX-based proteolysis targeting chimeras (PROTACs) to investigate DHFR degradation pharmacology and one-carbon biochemistry. These on-target, cell-active PROTACs show proteasome- and E3 ligase-dependent activity, and selective degradation of DHFR in multiple cancer cell lines. By comparison, treatment with MTX increases cellular DHFR protein expression. Importantly, these PROTACs produced distinct, less-lethal phenotypes compared to MTX. The chemical probe set described here should complement conventional DHFR inhibitors and serve as useful tools for studying one-carbon biochemistry and dissecting complex polypharmacology of MTX and related drugs. Such compounds may also serve as leads for potential autoimmune and antineoplastic therapeutics.

Synthesis, anticancer evaluation and molecular docking studies of methotrexate's novel Schiff base derivatives against malignant glioma cell lines

Recent years have witnessed advancement in cancer research that has led to the development of improved cytotoxic therapies with reduced side effects. Methotrexate (MTX) is a commonly used anticancer drug having robust activity, but with serious side effects. Several derivatives of MTX have been reported by modification at different sites to reduce its side effects and enhance efficacy. The current work describes the development of active MTX Schiff base derivatives by treating MTX with several aldehydes viz 2-chlorobenzaldehyde, 3-nitrobenzaldehyde, 5-chloro-2-hydroxybenz-aldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-thiocarboxyaldehyde, trans-2-pentenal and glutaraldehyde. Newly synthesized derivatives were evaluated for their anticancer potential against human malignant glioma U87 (MG-U87) cell lines at different concentrations of 200 μM, 100 μM, 50 μM, 25 μM, 12.5 μm, 6.25 μm and 0 μM. MTX derivatives with 2-Chlorobenzaldehyde (IC₅₀ ∼100 μM), 2-Thiocarboxyaldehyde (IC₅₀ <200 μM) and 2- Pentenal (IC₅₀ ∼250 μM) showed much better activity at 100 µM compared to 400 µM concentration of MTX. Molecular docking studies were performed that showed a good correlation with the results obtained from in vitro experiments. The excellent agreement between molecular modeling and growth inhibition assay shows that the binding mode hypothesis is justly close to the experimentally biological values, therefore, may prove helpful for further lead optimization and clinical trials.Communicated by Ramaswamy H. Sarma.

Preparation and In Vitro and In Vivo Evaluation of Technetium-99m-Labeled Folate and Methotrexate Conjugates as Tumor Imaging Agents

The cell-membrane folic acid (FA) receptors are known to be responsible for cellular accumulation of FA and FA analogs, such as methotrexate (MTX), and are overexpressed on several tumor cells. Folate, as well as antifolates (i.e., MTX), possess high affinity for the folate-receptor positive cells and tissues and were deemed useful for diagnostic imaging. We have prepared and evaluated technetium-99m (99mTc)- labeled FA and MTX analogs using MAG3 and MAG2 chelating agents in an attempt to develop folate-receptor targeting radiopharmaceuticals. Folate and MTX-conjugates after labeling with 99mTc by ligand exchange method displayed high in vitro stability in human plasma. In vitro cell binding and internalization on MCF-7 and MDA-MB-231 cells indicated the affinity and specificity of the radioconjugates toward human breast cancer cells. In mice, all radioconjugates showed rapid clearance from the blood and excretion mainly through the renal/urinary pathway, with some elimination by way of the biliary route. There was no significant accumulation of radioactivity observed in other organs, with the exception of the intestines. Uptake in the breast tumor was moderate in nude mice. These findings could be of potential diagnostic interest in designing and developing FA/MTX-based radiopharmaceuticals for tumor imaging.