Design, Green Synthesis and Tailoring of Vitamin E TPGS Augmented Niosomal Nano-Carrier of Pyrazolopyrimidines as Potential Anti-Liver and Breast Cancer Agents with Accentuated Oral Bioavailability

Abstract

VEGF plays a crucial role in cancer development, angiogenesis and progression, principally liver and breast cancer. It is vital to uncover novel chemical candidates of VEGFR inhibitors to develop more potent anti-breast and anti-liver cancer agents than the currently available candidates, sorafenib and regorafenib, that face resistance obstacles and severe side effects. Herein, nine pyrazolopyrimidine derivatives were designed, synthesized as sorafenib and regorafenib analogues and screened for their in vitro cytotoxic and growth inhibition activities against four human cancer cell lines, namely breast cancer (Michigan Cancer Foundation-7 (MCF-7), hepatocellular carcinoma (HCC) type (HepG2), lung carcinoma (A-549) and human colorectal carcinoma-116 (HCT-116)). Among the tested compounds, compounds 1, 2a, 4b and 7 showed the uppermost cytotoxic activities against all aforementioned cell lines with IC50 estimates varying from 6 to 50 µM, among which compound 7 showed the best inhibitory activity on all tested compounds. Stunningly, compound 7 showed the best significant inhibition of the VEGFR-2 protein expression level (72.3%) as compared to the control and even higher than that produced with sorafenib and regorafenib (70.4% and 55.6%, respectively). Modeling studies provided evidence for the possible interactions of the synthesized compounds with the key residues of the ATP binding sites on the hinge region and the "DFG out" motif of VEGFR-2 kinase. Collectively, our present study suggests that pyrazolopyrimidine derivatives are a novel class of anti-cancer drug candidates to inhibit VEGF-VEGFR function. Aspiring to promote constrained aqueous solubility, hence poor oral bioavailability of the developed lead molecule, 7 and 2a-charged D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) surface-coated niosomes were successfully constructed, adopting a thin film hydration technique striving to overcome these pitfalls. A 23 full factorial design was involved in order to investigate the influence of formulation variables: type of surfactant, either Span 60 or Span 40; surfactant:cholesterol ratio (8:2 or 5:5) along with the amount of TPGS (25 mg or 50 mg) on the characteristics of the nanosystem. F2 and S2 were picked as the optimum formula for compounds 2a and 7 with desirability values of 0.907 and 0.903, respectively. In addition, a distinguished improvement was observed in the compound's oral bioavailability and cytotoxic activity after being included in the nano-TPGS-coated niosomal system relative to the unformulated compound. The nano-TPGS-coated niosomal system increased the hepatocellular inhibitory activity four times fold of compound 7a (1.6 µM) and two-fold of 2a (3 µM) relative to the unformulated compounds (6 µM and 6.2 µM, respectively).