Pyrazole is a common structural unit in many pharmaceuticals and a central axis of numerous ongoing studies
devoted to the synthesis and biological evaluation of novel pyrazole moiety-bearing molecules. Annelated
pyrazoles are of particular interest as they constitute the core of several well-known drugs, including Sildenafil,
Zaleplon and Allopurinol. Among the vast variety of up to now developed biologically active annelated pyrazole
derivatives, synthetically demanding 2H-pyrazolo[4,3-c]pyridines are still relatively understudied.
Herein we present synthesis of novel variously substituted 2H-pyrazolo[4,3-c]pyridine derivatives, which are
easily accessible from various pyrazolidin-3-ones. The compounds were evaluated for their optical properties
and cytotoxicity in vitro against a small panel of normal and cancer cell lines. The compounds exhibited
favorable cytotoxicity, with GI50 values in the micromolar range and selected ones were further studied to assess
their mode of action.

Acknowledgements
This work was supported by the Research Council of Lithuania (LMTLT), agreement No S-MIP-20-60.