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Design and Biological Evaluation of Pyrazole-Based Sulphonamide Anticancer Leads

This study reports the design, synthesis, and biological evaluation of novel pyrazole-based sulphonamide derivatives as potential anticancer agents for colorectal cancer, identifying compound CTPS-1 as a promising preliminary hit with moderate in vitro activity against HCT116 cells, favorable ADMET profiles, and strong molecular docking interactions, despite the need for further optimization to address hepatotoxicity.

Original authors: Y. H. Momin, K. S. Shinde, S. S. Shelake, S. S. Gaikwad, A. G. Patil

Published 2026-07-31

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CC BY 4.0

Original authors: Y. H. Momin, K. S. Shinde, S. S. Shelake, S. S. Gaikwad, A. G. Patil

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the human body as a bustling, high-tech city. Inside this city, there are millions of tiny workers (cells) that follow strict rules to keep everything running smoothly. Sometimes, however, a few workers get confused, stop listening to orders, and start building chaotic, runaway construction projects. This is what we call cancer. To stop these runaway projects, scientists act like master architects and locksmiths. They design tiny, custom-made keys (drugs) that fit perfectly into specific locks (proteins) on the cancer cells. If the key fits, it jams the lock, stopping the cancer from growing or even telling the cell to shut down. But designing these keys is tricky; they have to be strong enough to do the job, small enough to travel through the city's streets (our bloodstream), and safe enough not to break anything else along the way. This is where a new study comes in, exploring a fresh set of keys made from a special building block called "pyrazole" combined with a "sulphonamide" group, specifically targeting a type of cancer that affects the colon (the large intestine).

In this study, a team of researchers from India decided to build a series of ten new molecular keys, which they named CTPS-1 through CTPS-10. They started by designing these keys on a computer, using a process called "molecular docking." Think of this like a video game where you try to fit a puzzle piece into a slot; the computer simulates how well the new drug fits into the "locks" of three specific proteins known to help colorectal cancer grow: mPGES-1, Apaf-1, and HGPRT. The computer gave them a score for how tight the fit was. The results were promising: the new keys fit quite well, with scores ranging from -5.3 to -7.7 kcal/mol, which is comparable to early-stage hits that scientists get excited about.

But fitting on a computer is just the first step. The team then went into the lab to actually build two of these keys, CTPS-1 and CTPS-6, and checked their blueprints using special tools like FT-IR and NMR to make sure they were built exactly as designed. Once they had the real molecules, they tested them against colorectal cancer cells (called HCT116) in a petri dish. They used a standard cancer drug, 5-fluorouracil (5-FU), as a benchmark. The standard drug was very effective, stopping 85% of the cancer cells at a dose of 100 µg/mL. The new key, CTPS-1, showed "moderate" activity. It managed to stop about 68% of the cancer cells at the same dose, with a calculated IC50 value (the amount needed to stop half the cells) of 85.62 µg/mL. This is a good start, but it's not as strong as the standard drug yet.

Interestingly, the other key they built, CTPS-6, didn't work as well. Even at the highest dose tested (100 µg/mL), it only stopped about 44% of the cells and never reached the 50% mark needed to calculate an IC50. Why the difference? The researchers suspect it comes down to a tiny detail in the design: CTPS-1 has a chlorine atom attached to it, while CTPS-6 has a methyl group. The chlorine acts like an "electron-withdrawing" magnet, pulling electrons in a way that helps the drug stick better to the cancer targets, whereas the methyl group in CTPS-6 is more "electron-donating" and didn't help the drug grab on as tightly.

The study also ran a series of safety checks on the computer (ADMET analysis) to predict how the body would handle these drugs. The results suggested that these molecules would be good at getting into the body through the mouth and wouldn't easily cross into the brain (which is often a good thing for cancer drugs). However, there was a red flag: the computer predicted that all the compounds might be toxic to the liver. This means that while they look promising as cancer fighters, they would need to be tweaked to make them safer for the liver before they could ever be tested in people.

So, what is the bottom line? The paper suggests that CTPS-1 is a "preliminary hit"—a promising starting point that proves the idea works. It shows that pyrazole-based sulphonamides can fight colorectal cancer cells, and that adding a chlorine atom makes them stronger. However, the paper is very clear that this is just the beginning. The drugs are not yet potent enough to replace current treatments, they haven't been tested on normal cells to see if they are safe, and we don't know exactly how they kill the cancer cells yet. The researchers conclude that with more work to fix the liver toxicity and improve the strength, these molecules could become the foundation for new, effective cancer medicines in the future.

Technical Summary: Design and Biological Evaluation of Pyrazole-Based Sulphonamide Anticancer Leads

Problem Statement
Colorectal cancer remains a significant global health challenge, necessitating the development of novel therapeutic agents with improved efficacy and pharmacokinetic profiles. While pyrazole and sulphonamide scaffolds individually possess known anti-inflammatory and anticancer properties, their hybridization specifically targeting key colorectal cancer-associated proteins—Microsomal Prostaglandin E Synthase-1 (mPGES-1), Apoptotic Protease Activating Factor-1 (Apaf-1), and Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT)—has not been fully explored. Furthermore, there is a gap in literature regarding the integration of computational screening with experimental validation for this specific class of hybrid molecules. This study addresses the need for rational drug design to identify early-stage "hit" molecules that can serve as a foundation for optimizing anticancer leads.

Methodology
The study employed a multi-disciplinary approach combining rational drug design, chemical synthesis, computational modeling, and in vitro biological evaluation.

Rational Design and Synthesis: Ten novel pyrazole-based sulphonamide derivatives (CTPS-1 to CTPS-10) were designed by integrating a pyrazole scaffold with aryl sulphonamide and ester functionalities. The synthesis involved the condensation of $\beta$ -ketoesters with 4-hydrazinobenzenesulfonamide. Two specific compounds, CTPS-1 (containing a 5-chlorothiophene moiety) and CTPS-6 (containing a 5-methylthiophene moiety), were selected for full synthesis and characterization based on initial in silico predictions.
Characterization: The synthesized compounds were characterized using FT-IR, $^1$ H-NMR, and Mass Spectrometry to confirm structural integrity and the presence of functional groups such as sulfonamide, ester, and heterocyclic rings.
Computational Studies:
- Molecular Docking: The compounds were docked against three target proteins (HGPRT, Apaf-1, and mPGES-1) using PyRx and Biovia Discovery Studio. The protocol was validated by re-docking co-crystallized ligands.
- ADMET Analysis: Pharmacokinetic properties (absorption, distribution, metabolism, excretion) and toxicity profiles were predicted using SwissADME, pKCSM, and PreADMET.
- Density Functional Theory (DFT): Electronic properties, including HOMO-LUMO energy gaps, chemical hardness, and electrophilicity, were calculated for CTPS-1 and CTPS-6 using Orca software to correlate electronic structure with reactivity.
Biological Evaluation: The cytotoxic potential of CTPS-1 and CTPS-6 was evaluated against the human colorectal carcinoma cell line (HCT116) using the MTT assay. 5-Fluorouracil (5-FU) served as the standard reference drug.

Key Results

Chemical Synthesis: The synthesis of CTPS-1 and CTPS-6 was successful, with yields of 24.48% and 22.76%, respectively. Spectroscopic data confirmed the formation of the pyrazole-sulfonamide structure, with specific confirmation of the chlorine isotope pattern in CTPS-1 via mass spectrometry.
Molecular Docking: All ten designed compounds showed moderate to good binding affinities.
- Against HGPRT (2JBH), CTPS-1, CTPS-4, CTPS-5, and CTPS-6 exhibited binding scores ranging from -7.6 to -7.7 kcal/mol, comparable to the natural ligand Guanosine-5'-monophosphate (-7.8 kcal/mol).
- Against Apaf-1 (2P1H), CTPS-3, CTPS-4, and CTPS-5 showed improved affinity over the co-crystal zinc ion.
- Against mPGES-1 (4YK5), CTPS-1, CTPS-2, and CTPS-4 demonstrated strong binding (-7.6 to -7.7 kcal/mol).
- CTPS-1 and CTPS-6 were identified as the best-docked candidates for detailed analysis, showing interactions with key amino acid residues (e.g., Thr149, Arg148 in HGPRT; Ser20, Thr21 in mPGES-1).
ADMET and Toxicity: Most compounds adhered to Lipinski's Rule of Five, with good human intestinal absorption (HIA) and low blood-brain barrier (BBB) permeability. However, in silico toxicity predictions indicated that all compounds were potentially hepatotoxic, a liability requiring future optimization. No mutagenic or skin sensitization risks were predicted for most compounds.
DFT Analysis: CTPS-1 exhibited a HOMO-LUMO gap ( $\Delta E$ ) of 3.226 eV, while CTPS-6 showed 3.194 eV. CTPS-1 displayed higher electrophilicity ( $\Omega = 4.75$ eV) and electronegativity ( $\chi = 3.91$ eV) compared to CTPS-6, suggesting a stronger capacity for electron acceptance and interaction with nucleophilic biological targets.
Cytotoxicity:
- CTPS-1 demonstrated moderate cytotoxicity against HCT116 cells with an IC $_{50}$ value of 85.62 µg/mL (67.93% inhibition at 100 µg/mL).
- CTPS-6 showed significantly lower activity, failing to reach 50% inhibition at the tested concentration range (IC $_{50}$ could not be determined; 44.48% inhibition at 100 µg/mL).
- The standard drug 5-FU showed an IC $_{50}$ of 41.65 µg/mL.

Significance and Claims
The authors position this work as a foundational step in the discovery of pyrazole-derived sulphonamide anticancer agents. The study claims that:

Structure-Activity Relationship (SAR): The electron-withdrawing chlorine atom in CTPS-1 likely enhances cytotoxicity compared to the electron-donating methyl group in CTPS-6, potentially by increasing interactions with key biomolecular targets.
Lead Identification: Although less potent than 5-FU, CTPS-1 qualifies as a "hit" molecule (IC $_{50}$ between 50–100 µg/mL) suitable for further structural optimization.
Multi-Target Potential: The compounds show promise as multi-target inhibitors for colorectal cancer pathways involving inflammation (mPGES-1), apoptosis (Apaf-1), and nucleotide metabolism (HGPRT).

Limitations and Future Directions
The paper explicitly acknowledges several limitations:

Biological evaluation was restricted to a single cancer cell line (HCT116) without assessment of selectivity against normal cells.
No mechanistic studies (e.g., apoptosis induction, cell cycle arrest) were performed.
Molecular dynamics simulations were not conducted to assess ligand-protein stability over time.
The predicted hepatotoxicity requires experimental validation and structural mitigation.

The authors conclude that while the current derivatives exhibit moderate potency, they provide a viable scaffold for rational lead optimization, specifically suggesting modifications to the ester group, backbone stiffening, and the introduction of stronger electron-withdrawing groups to improve efficacy and reduce toxicity.

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