Imidazo[1,2-b]pyridazine

Identification of Imidazo[1,2-b]pyridazine Derivatives as Potent, Selective, and Orally Active Tyk2 JH2 Inhibitors.[Pubmed:30891145]

ACS Med Chem Lett. 2019 Feb 21;10(3):383-388.

In sharp contrast to a previously reported series of 6-anilino imidazopyridazine based Tyk2 JH2 ligands, 6-((2-oxo-N1-substituted-1,2-dihydropyridin-3-yl)amino)Imidazo[1,2-b]pyridazine analogs were found to display dramatically improved metabolic stability. The N1-substituent on 2-oxo-1,2-dihydropyridine ring can be a variety of alkyl, aryl, and heteroaryl groups, but among them, 2-pyridyl provided much enhanced Caco-2 permeability, attributed to its ability to form intramolecular hydrogen bonds. Further structure-activity relationship studies at the C3 position led to the identification of highly potent and selective Tyk2 JH2 inhibitor 6, which proved to be highly effective in inhibiting IFNgamma production in a rat pharmacodynamics model and fully efficacious in a rat adjuvant arthritis model.

Imidazo[1,2-b]pyridazines targeting Toxoplasma gondii calcium-dependent protein kinase 1 decrease the parasite burden in mice with acute toxoplasmosis.[Pubmed:29524527]

Int J Parasitol. 2018 Jun;48(7):561-568.

The current therapeutic arsenal for toxoplasmosis is restricted to drugs non-specific to the parasite which cause important side effects. Development of more efficient and specific anti-Toxoplasma compounds is urgently needed. Imidazo[1,2-b]pyridazines designed to inhibit the calcium-dependent protein kinase 1 of Toxoplasma gondii (TgCDPK1) and effective against tachyzoite growth in vitro at submicromolar ranges were modified into hydrochloride salts to be administered in vivo in a mouse model of acute toxoplasmosis. All protonated Imidazo[1,2-b]pyridazine salts (SP230, SP231 and SP232) maintained their activity on TgCDPK1 and T. gondii tachyzoites. Rat and mouse liver microsomes were used to predict half-life and intrinsic clearance, and the pharmacokinetic profile of the most rapidly degraded imidazo[1,2b]pyridazine salt (SP230) was determined in serum, brain and lungs of mice after a single administration of 50mg/kg. Compounds were then tested in vivo in a murine model of acute toxoplasmosis. Mice infected with tachyzoites of the ME49 strain of T. gondii were treated for 4, 7 or 8days with 25 or 50mg/kg/day of SP230, SP231 or SP232. The parasite burdens were strongly diminished (>90% reduction under some conditions) in the spleen and the lungs of mice treated with Imidazo[1,2-b]pyridazine salts compared with untreated mice, without the need for pre-treatment. Moreover, no increases in the levels of hepatic and renal toxicity markers were observed, demonstrating no significant signs of short-term toxicity. To conclude, Imidazo[1,2-b]pyridazine salts have strong efficacy in vivo on acute toxoplasmosis and should be further tested in a model of mouse congenital toxoplasmosis.

Design, synthesis, and biological evaluation of imidazo[1,2-b]pyridazine derivatives as mTOR inhibitors.[Pubmed:28235701]

Eur J Med Chem. 2017 Mar 31;129:135-150.

ATP-competitive mTOR inhibitors have been studied as potential antitumor agents. Based on the structure-activity relationship of known mTOR inhibitors, a series of novel Imidazo[1,2-b]pyridazine derivatives were synthesized and characterized. The anti-proliferative activities of these compounds were evaluated by SRB assay against six human cancer cell lines. Imidazo[1,2-b]pyridazine diaryl urea derivatives A15-A24 exhibited significant anti-proliferative activity especially against non-small cell lung cancer A549 and H460 with IC50 values ranging from 0.02 muM to 20.7 muM. Among them, compounds A17 and A18 showed mTOR inhibitory activity with IC50 of 0.067 muM and 0.062 muM, respectively. A more detailed analysis of compounds A17 and A18 showed that they induced G1-phase cell cycle arrest and suppressed the phosphorylation of AKT and S6 at cellular level. Moreover, obvious anticancer effect of A17 in vivo was observed in established nude mice A549 xenograft model.

Environmentally-Safe Conditions for a Palladium-Catalyzed Direct C3-Arylation with High Turn Over Frequency of Imidazo[1,2-b]pyridazines Using Aryl Bromides and Chlorides.[Pubmed:27380613]

Chem Asian J. 2016 Sep 6;11(17):2443-52.

Pd(OAc)2 was found to catalyze very efficiently the direct arylation of Imidazo[1,2-b]pyridazine at C3-position under a very low catalyst loading and phosphine-free conditions. The reaction can be performed in very high TOFs and TONs employing as little as 0.1-0.05 mol % catalyst using a wide range of aryl bromides. In addition, some electron-deficient aryl chlorides were also found to be suitable substrates. Moreover, 31 examples of the cross couplings were reported using green, safe, and renewable solvents, such as pentan-1-ol, diethylcarbonate or cyclopentyl methyl ether, without loss of efficiency.