Novel [1,2,4]triazole derivatives were synthesized via various synthetic pathways. Among which were different substituted [1,2,4]triazole analogues that were synthesized, in addition to various fused [1,2,4]triazolo[1,5‐a]pyrimidine derivatives, [1,2,4]triazolo[1,5‐a][1,3,5]triazines, and [1,2,4]triazolo[5,1‐c][1,2,4]triazines. Besides, benzo[h][1,2,4]triazolo[5,1‐b]quinazolines, [1,2,4]triazolo‐[5,1‐b]quinazoline, [1,2,4]triazolo[1,5‐a]quinazoline and [1,2,4]triazolo[5,1‐d][1,2,3,5]tetrazine derivatives were also synthesized. The newly synthesized compounds were evaluated for their in vitro anticancer activity against liver cancer HepG2 and breast cancer MCF7 cell lines compared with the reference drug doxorubicin. Compounds 4, 7, 15, 17, 28, 34, and 47 were found to exert promising anticancer activity against HepG2 cell line showing IC50 values ranging from 17.69 to 25.4 μM/L, while compounds 7, 14a, 17, 28, and 34 showed significant activity against MCF7 cell line with IC50 values ranging from 17.69 to 27.09 μM/L.

Various new substituted and fused pyridotriazepine analogues have been synthesized via different synthetic pathways. Among which are different heterocyclic compounds consisting of the pyridotriazepine backbone fused to different heterocyclic systems comprising either substituted pyrimidine nucleus such as compounds 3–9 or substituted 4‐aminopyridine nucleus such as compounds 10–16. Besides, the tetrahydroquinoline derivative 17, [1,2,4]triazolopyrimidine derivative 18, thienodiazocine derivative 19, dihydrobenzofuropyridine derivative 20, and the substituted pyrrole derivative 21 were synthesized. In addition, different substituted pyridotriazepine derivatives as indicated in compounds 22–25 were designed and synthesized. Twenty‐five of the newly synthesized compounds were subjected to in vitro anticancer screening against mammalian colon carcinoma HCT‐116 cell line using Cisplatin as a reference drug. The anticancer activity screening results revealed that among the tested compounds, the tetrahydropyrido[1,2‐b]pyrimido[4,5‐e][1,2,4]triazepine derivative 4 substituted at C2 and C4 positions with S‐methyl and amino moieties, respectively, and the 2,4‐dithioxo analogue 9 and the 2‐thioxodipyrido[1,2‐b:2′,3′‐e][1,2,4]triazepine derivative 11 substituted at C3 and C4 with a cyano and amino moieties, respectively, exhibited moderate to strong anticancer activity against mammalian colon carcinoma HCT‐116 cell line.