New series of thiazolo[4,5-d]pyridazin and imidazo[2′,1′:2,3]thiazolo[4,5-d]pyridazin analogues were designed, synthesized and evaluated for their in vitro DHFR inhibition and antitumor activity. Compounds 13 and 43 proved to be DHFR inhibitors with IC₅₀ 0.05 and 0.06 μM, respectively. 43 proved lethal to OVCAR-3 Ovarian cancer and MDA-MB-435 Melanoma at IC₅₀ 0.32 and 0.46 μM, respectively. The active compounds formed hydrogen bond at DHFR binding site between N₁-nitrogen of the pyridazine ring with Glu30; the carbonyl group with Trp24, Arg70 or Lys64; π-cation interaction with Arg22 and π-π interaction with Phe31 residues. Ring annexation of the active 1,3-thiazole ring analogue 13 into the bicyclic thiazolo[4,5-d]pyridazine (18,19) or imidazo[2,1-b]thiazoles (23–25) decreased the DHFR inhibition activity; while the formation of the tricyclic imidazo[2′,1′:2,3]-thiazolo[4,5-d]pyridazine (43–54) increased potency. The obtained model could be useful for the development of new class of DHFR inhibitors.

设计，合成并评价了噻唑洛[4,5- d ]哒嗪和咪唑并[2'，1'：2,3]噻唑洛[4,5- d ]哒嗪类似物的新系列，并对其体外DHFR抑制和抗肿瘤活性进行了评估。。化合物13和43被证明是DHFR抑制剂，IC ₅₀分别为0.05和0.06μM。在IC ₅₀分别为0.32和0.46μM时，有43例被证明对OVCAR-3卵巢癌和MDA-MB-435黑色素瘤具有致死性。活性化合物在N ₁之间的DHFR结合位点形成氢键-哒嗪环与Glu30的氮；具有Trp24，Arg70或Lys64的羰基；与Arg22的π-阳离子相互作用和与Phe31残基的π-π相互作用。活性-1,3-噻唑环类似物的环吞并13到双环噻唑并[4,5- d ]哒嗪（18，19）或咪唑并[2,1- b ]噻唑（23 - 25）降低了DHFR的抑制活性; 而形成三环咪唑并[2'，1'：2,3]-噻唑并[4,5- d ]哒嗪（43 – 54）则增加了效力。获得的模型可能对开发新型的DHFR抑制剂有用。