Synthesis of Novel Thieno[2,3-d]pyrimidine Derivatives and Evaluation of Their Cytotoxicity and EGFR Inhibitory Activity.

Background: 4-Substitutedaminoquinazoline scaffolds were reported to possess potent cytotoxic and EGFR inhibitory activity such as gefitinib (Iressa), erlotinib (Tarceva) and tandutinib.

Objective: Synthesis of novel 4-substitutedaminothieno[2,3-d]pyrimidine derivatives as bioisosters of 4-substitutedaminoquinazoline derivatives with potential cytotoxic and EGFR inhibitory activity.

Methods: Novel 4-substitutedaminothieno[2,3-d]pyrimidine derivatives 4a-i and 5a-c were synthesized via reacting corresponding 4-chlorothieno[2,3-d]pyrimidine derivatives 3a-c with N-methylpiperazine, morpholine, N-phenylpiperazine or 1,3-propanediamine. Six compounds (2a, 4d, 4e, 5a-c) were selected by the National Cancer Institute (USA) for evaluating their cytotoxic activity using 60 different human tumor cell lines using a single dose (10-5 Molar). The rest of the synthesized compounds (2b, 2c, 3a-c, 4a-c and 4f-i) were subjected to screening against T47D breast cancer cell line using a single dose (10-5 Molar) at Pharmacology lab., Cancer biology lab., Egyptian National Institute. Moreover, compounds 2a and 4b-e were subjected to further evaluation by IC50 determination. Finally, the inhibition of epidermal growth factor receptor (EGFR) was then investigated for the most active compounds 2a and 4d.

Results: Compounds 2a and 4b-e showed significant cytotoxic activity. Compound 2a was more potent than doxorubicin against lung cancer cell line A549 with IC50 = 13.40 μM and comparable activity against MCF7. Compound 4d exhibited more potent activity than Doxorubicin against prostate PC3 (IC50 = 14.13 µM) while showed comparable activity against MCF7 and T47D.

Conclusion: 4-Substitutedaminothieno[2,3-d]pyrimidine is a promising backbone for the design and synthesis of potent cytotoxic leads.