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Synthesis and Biological Evaluation of Telmisartan Alkylamine Derivatives as Potential Anticancer Agents

TANNER J. SCHUMACHER, ZACHARY S. GARDNER, MICHAEL P. MCPARLAN, TASMIN OMY, KOMARAIAH PALLE, JON RUMBLEY and VENKATRAM R. MEREDDY
Anticancer Research March 2024, 44 (3) 911-919; DOI: https://doi.org/10.21873/anticanres.16885

Abstract

Background/Aim: Telmisartan is an angiotensin II receptor type 1 (AT1) antagonist with anticancer properties against solid and hematological cancer cell lines. Using telmisartan as a template, we developed alkylamine derivatives with reduced AT1 activity but increased anticancer activity. Materials and Methods: Synthesis of candidate compounds was carried out via hexafluorophosphate benzotriazole tetramethyl uronium coupling reaction, then their inhibition of cell proliferation was determined via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and colony-formation assay was carried out on the lead candidate compound 8. Cell death via apoptosis or necrosis by compound 8 was determined by flow cytometry using annexin V and propidium iodide, tolerability dosing was carried out in ICR mice, and tumor-reduction properties were determined in an MDA-MB-231 xenograft model. Results: Some of the synthesized candidates exhibited good inhibition of cell proliferation with low micromolar half maximal effective concentrations in triple-negative breast cancer cell lines MDA-MB-231 and 4T1. Compound 8 exhibited lower affinity towards AT1 than parent telmisartan, inhibition of colony formation, and cell-cycle analysis revealed apoptosis as potentially important in causing cell death. In vivo evaluation with compound 8 indicated that it was well tolerated at high concentrations in healthy mice. Additionally, compound 8 showed higher growth inhibition in the MDA-MB-231 tumor xenograft mouse model compared to telmisartan. Conclusion: Our study indicated that alkylamine derivatives of telmisartan exhibited good solubility and higher inhibition of cancer cell proliferation than telmisartan. Compound 8 was found to be a good lead compound, with potential for development as an anticancer agent.

Key Words:

Telmisartan is a blocker of angiotensin II type 1 (AT1) receptor, clinically used for the treatment of hypertension and heart failure (1-4). Drug-repurposing studies have indicated that this compound exhibits cell proliferation-inhibiting properties against various types of solid and hematological cancer cells (5-17). Some of the reported studies also include significant in vivo tumor growth inhibition in mice treated with telmisartan (5-17). Some of the anticancer mechanisms that have been implicated include activation of peroxisome proliferator-activated receptor-gamma, AMP-activated protein kinase and mammalian target of rapamycin (mTOR) signaling pathways (5-8). Although telmisartan has been reported to provide tumor growth inhibition in a few mouse tumor models, its ability to inhibit cancer proliferation often requires high micromolar dosages. Regular use of this drug at high concentrations may pose significant clinical consequences of lowering blood pressure due to its high potency for AT1 receptor. As part of our longstanding interest in developing novel small molecules as potential anticancer agents, we undertook a project to synthesize telmisartan derivatives to reduce their potency for AT1 and reduce cancer cell proliferation at low concentrations (18-26).

Aliphatic amines and their derivatives have been extensively used to improve pharmacological activity, water solubility, and oral bioavailability of many clinically used anticancer drugs (26-29). The chemical structure of telmisartan (Figure 1) contains bibenzimidazole and biphenyl units with a carboxylic acid group. This acid group participates in the critical binding interactions with the AT1 receptor to provide high potency at low concentrations (30, 31). We envisioned that coupling of the carboxylic group in telmisartan with aliphatic amines might improve cell proliferation-inhibiting properties while reducing the affinity for AT1 receptor. If the synthesized novel aminotelmisartan derivatives showed the anticipated pharmacological properties, then they might be further developed as anticancer agents. In this regard, we coupled the carboxylic acid of telmisartan under amide coupling conditions with various aliphatic amines including piperazines, aminoethyl piperazines, aminomethyl piperidines/pyrrolidines, and aminoethyl amines.

Figure 1.
Figure 1.

Coupling of alkyl amines with the carboxylic acid of telmisartan (1). DMF: Dimethylformamide; Et3N: triethylamine; HBTU: hexafluorophosphate benzotriazole tetramethyl uronium.

Materials and Methods

Synthesis of candidate compounds. The carboxylic acid of telmisartan (1 mmol) was dissolved in 5 ml dimethylformamide followed by slow addition of 1.5 mmol hexafluorophosphate benzotriazole tetramethyl uronium. To a separate reaction vessel, 1.1 mmol of the respective amine was dissolved in dimethylformamide and 2 mmol triethyl amine was added. After 5 minutes, the amine mixture was added dropwise to the solution of hexafluorophosphate benzotriazole tetramethyl uronium with telmisartan and stirred for 12 hours. Reaction progress was monitored via thin-layer chromatography and upon consumption of telmisartan, the reaction mixture was poured over dilute HCl and extracted with 50 ml ethyl acetate three times. The resulting crude mixture was purified via column chromatography (50-90% ethyl acetatehexanes) to afford the final products 2-12 in good yields (80-91%). Spectral data for lead candidate 8: 1H Nuclear magnetic resonance (400 MHz, chloroform-d): d 7.8 (m, 1H), 7.6 (m, 1H), 7.5 (s, 1H), 7.4 (m, 2H), 7.3 (m, 7H), 7.1 (d, 2H, J=8 Hz), 6.0 (t, 1H, J=5Hz), 5.4 (s, 2H), 3.8 (s, 3H), 3.2 (m, 1H), 2.9 (quint, 2H, J=7.6 Hz), 2.8 (m, 1H), 2.7 (s, 3H), 2.5 (br., 1H), 2.4 (m, 2H), 1.9 (m, 2H), 1.6 (s, 1H), 1.5 (m, 1H), 1.4 (m, 1H), 1.2 (m, 2H), 1.0 (t, 3H, J=7.2Hz), 0.9 (m, 1H). 13C Nuclear magnetic resonance (100 MHz, chloroform-d): d169.8, 156.3, 154.7, 143.2, 142.9, 140.3, 138.6, 136.7, 136.2, 135.3, 135.1, 130.2, 129.9, 129.5, 129.4, 128.4, 127.4, 126.4, 124.0, 123.8, 122.5, 122.3, 119.6, 109.5, 108.9, 55.3, 47.0, 46.4, 45.2, 31.8, 29.9, 29.8, 25.9, 24.0, 21.9, 16.9, 14.1. High-resolution mass spectrometry electrospray ionization m/z: calculated for C39H42N6O [M+1]: 611.3493, found 611.3505.

Cell culture. MDA-MB-231 cells (American Type Culture Collection, Manassas, Virginia, USA) for in vitro were grown in Dulbecco’s modified Eagle’s medium (Corning, Murphysboro, IL, USA) supplemented with 10% fetal bovine serum (FBS) and penicillin-streptomycin (PS) (50 μg/ml) (Gibco, Grand Island, NY, USA). 4T1 cells (American Type Culture Collection, Manassas, VA, USA) were grown in RPMI (Corning) supplemented with 10% FBS and PS (50 μg/ml) (Gibco). MDA-MB-231 cells for in vivo use were maintained in L-15, with 10% FBS (Gibco). All cells were incubated at 37°C with 5% CO2.

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay. Confluent MDA-MB-231 and 4T1 cells were treated with trypsin, centrifuged, and resuspended at 5×104 cells/ml. To a 96-well plate was added 100 μl of the cell suspension and cells were incubated at 37°C with 5% CO2 for 24 hours. Test compounds were then added in eight, 1:2 serial dilutions starting at 100 μM down to 0.78 μM, with 0.001% dimethyl sulfoxide (DMSO) as control, the plate was then incubated for 3 days. After incubation, 10 μl of MTT (5 mg/ml) was added to the plate which was further incubated for 4 hours. One hundred microliters of sodium dodecyl sulfate (0.1 g/ml, 0.01N HCl) was then added and the plate was incubated for an additional 4 hours. Absorbance values were then taken at 570 nm using a BioTek Synergy 2 Multimode Microplate Reader (BioTek Instruments Inc., Winooski, VT, USA). The absorbance values of treated wells were then divided by those of untreated growth media control values to calculate the percentage survival. Survival was then plotted against the log of concentration in GraphPad Prism 10 software (GraphPad Software, Boston, MA, USA) to generate half-maximal effective concentration (EC50) values.

Clonogenic survival assay. A total of 500 MDA-MB-231 cells were plated in 6-well culture dishes in triplicate. Cells were allowed to attach overnight and were then treated with 1, 3, 5, 6, and 7 μM of 8 or dimethyl sulfoxide (DMSO) as the vehicle control and allowed to form colonies. After 7 days, colonies were fixed in methanol, stained with crystal violet (0.5% w/v), and counted. Only colonies containing more than 25 cells were imaged and counted.

Apoptosis and necrosis assay. The number of apoptotic and necrotic MDA-MB-231 cells were measured by annexin V and propidium iodide (PI) staining using flow cytometry. After treatment with 8 at 10 and 25 μM for 72 hours, cells were removed using trypsin/EDTA, washed with phosphate-buffered saline, and resuspended in annexin V binding buffer (BD Biosciences, Franklin Lakes, NJ, USA). Fluorescein isothiocyanate-labeled annexin V and PI (BD Biosciences) were added to cells which were incubated for another 15 minutes. The number of apoptotic cells (annexin V+/PI−) and necrotic cells (annexin V+/PI+) events per microliter was quantified using a BD Accuri flow cytometer (BD Biosciences).

General tolerability study. Female BALB/C mice (7-8 weeks old, 17-21 g) (Charles River, Wilmington, MA, USA) were randomly assigned into groups (n=6 mice per group) and mice were intraperitoneally administered the lead candidate (compound 8) in the vehicle below in incremental doses for 12 days starting at 10 mg/kg or with vehicle control [10% DMSO, 10% polyethylene glycol 400 (PEG-400; CAS 25322-68-3), 40% Kolliphor HS 15 (CAS: 61909-81-7; 7.5% w/v in sterile water)] in 40% sterile water (Sigma–Aldrich, St. Louis, MO, USA). Dosing was increased after every third day of treatment up to a final concentration of 40 mg/kg. Body weights were recorded daily, and mice were monitored for behavior and grooming patterns. A body weight loss >10% indicated a halting of treatment until weight recovery; when a body weight loss >20% was observed, that mouse would be euthanized. At the end of the study, all mice were euthanized. The study was carried out following Institutional Animal Care and Use Committee protocol 2211-40546A.

Tumor growth-inhibition study. This part of the study was carried out by a contract organization, Medicilon Incorporated (Pudong, Shanghai, PR China) Female BALB/C mice (7-8 weeks old, 17-21 g) were obtained from Beijing Vital River Laboratory Animal Technology Co., Ltd. (Beijing, PR China) (License No.: SCXK-2021-0006. Animal Certificate No.: 110011220106449863). Cultured MDA-MB-231 cells were re-suspended in L-15 basal medium containing 50% Matrigel to 1×108 cells/ml. Under sterile conditions, 0.1 ml of cell suspension was inoculated subcutaneously into the right flank of BALB/C nude mice.

At 27 days after inoculation, tumor volumes averaged 190 mm3, mice were then randomized into three groups (n=8) for intraperitoneal treatment with vehicle [10% DMSO, 10% PEG-400, 40% Kolliphor HS 15 (7.5% w/v in sterile water) in 40% sterile water (Sigma–Aldrich)], 5 mg/kg telmisartan, or 5 mg/kg compound 8 in the above vehicle, respectively, administered for 21 days. On each day of administration, the animals were weighed, and the drug was administered according to the animal weight at a volume of 10 ml/kg. Tumor volume (mm3) was calculated as follows: (a×b2)/2, a being the tumor length and b the tumor width. The tumors were measured in two dimensions using a caliper. At the end of the study, tumors were resected and weighed.

Ethical considerations. The general tolerability study was approved and in compliance with the University of Minnesota’s Institutional Animal Care and Use Committee (2211-40546A). This study was performed in accordance with the relevant guidelines and regulations, and all protocols were approved by the University of Minnesota. The xenograft study was carried out using license No.: SCXK-2021-0006 and Animal Certificate No.: 110011220106449863.

Human AT1 cellular functional assay. Evaluation of the AT1 antagonist effect of compound 8 was carried out by Eurofin Discovery (San Diego, CA, USA) using a literature-reported procedure (32). Briefly, intracellular Ca2+ was monitored via fluorimetry in human recombinant HEK293 cells. The cellular antagonist effect was calculated as the percentage inhibition of control reference agonist response for AT1 after treatment with varying doses of compound 8. The apparent dissociation constant was calculated using a modified Cheng Prusoff equation.

Statistical analysis. Statistical analysis was carried out via unpaired parametric t-test.

Results

The coupling reaction of alkylamines and telmisartan with hexafluorophosphate benzotriazole tetramethyl uronium under basic conditions took place smoothly to provide the corresponding amides 2-12 after purification by silica gel column chromatography (Figure 1 and Figure 2).

Figure 2.
Figure 2.

Synthesized amino-telmisartan derivatives 2-12.

All the synthesized compounds were evaluated via MTT cell-proliferation assay against two TNBC cell lines, namely MDA-MB-231 (triple-negative mammary gland epithelial adenocarcinoma derived from a metastatic site of human origin) and 4T1 (metastatic stage IV triple-negative mammary gland epithelial cell line of murine origin). The piperazine derivatives 2-6 exhibited good solubility and the EC50 values were in the range from 11 to 29 μM compared to the parent telmisartan, which exhibited EC50 values of 89 and 62 μM, respectively. The aminomethyl piperidine and pyrrolidine derivatives 7-9, especially the candidate compound 8, were found to be more potent compared to other derivatives, with EC50 values of ~8 μM and ~11 μM, respectively. The aminoethyl amine derivatives 10 and 11 were slightly less potent than 8 and candidate 12 showed the least cell proliferation inhibition (Table I). Based on its higher inhibition of cell proliferation at lower concentrations, compound 8 was chosen as a lead for further studies.

View this table:
Table I.

Half-maximal effective concentration (EC50) for aminotelmisartan derivatives 1-12 against triple-negative breast cancer cell lines MDA-MB-231 and 4T1 evaluated via cell-proliferation assay. Values are means±standard error of the mean of a minimum of three biological replicates with two technical replicates per experiment.

A goal of this project was to develop candidate compounds with a lower affinity for the AT1 receptor than telmisartan. In this regard, candidate compound 8 was evaluated for its potential antagonistic effects on the AT1 receptor using human recombinant HEK-293 cells by measuring intracellular Ca2+ via fluorimetry. It was found that 8 inhibited the control agonist response to 50% at ~0.6 μM. The apparent equilibrium dissociation constant of 8 was found to be 48 nM. The parent telmisartan 1 was found to inhibit AT1 agonist response to 50% at 3.7 nM, with an equilibrium dissociation binding constant of 0.33 nM (33).

We treated MDA-MB-231 cells with 8 at concentrations ranging from 1 to 7 μM to assess its effectiveness in reducing their ability to form colonies. When compared to control cells treated with DMSO, this assay showed that the ability to form colonies was reduced in a dose-dependent manner (Figure 3).

Figure 3.
Figure 3.

Compound 8 inhibits colony formation ability of MDA-MB-231 cells. A: Representative image of colony assay plate of MDA-MB-231 cells treated with the indicated concentrations of 8. B: Survival fraction of MDA-MB-231 cells treated with the indicated concentration of 8. The error bars represent the standard deviation of values from three independent experiments. Statistical analysis was carried out via unpaired parametric t-test Significantly different from the dimethyl sulfoxide (DMSO) vehicle control at: *p<0.05, **p<0.01, ***p<0.001.

We then performed flow cytometry on MDA-MB-231 cells to analyze the cell cycle profile and apoptosis status of cells after treatment with 8 to better understand the reason for the reduced colony formation. Treatment with 8 led to a significant increase in the G1 phase of the cell cycle compared to DMSO-treated cells (Figure 4).

Figure 4.
Figure 4.

Treatment with 8 increased the proportion of G0/G1 phase of the cell cycle. A: Representative image of the cell-cycle profile of MDA-MB-231 cells treated with 8 at 7 μM for 24 hours. B: Histogram of the cell-cycle profile, showing an increase in G0/G1-phase cells after treatment with 8. The results are the mean from three different experiments. The error bar represents the standard deviation. Statistical analysis was carried out via unpaired parametric t-test. **Significantly different from the dimethyl sulfoxide (DMSO) vehicle control at p<0.01.

Similarly, in MDA-MB-231 cells, we also examined the percentage of cells undergoing apoptosis after 72-hour exposure to 8 at 10 μM and 25 μM or DMSO using annexin-V staining. As shown in Figure 5, compound 8-treated cells showed over 3- and 15-fold increase in total annexin-V positive cells, respectively, compared to DMSO-treated cells. Collectively, these results indicate that compound 8 exerts its cytotoxic activity in MDA-MB-231 cells at least partly by inducing cell-cycle arrest and apoptosis.

Figure 5.
Figure 5.

Treatment of MDA-MB-231 cell with 8 promoted apoptosis. A: Comparison of apoptosis measured by fluorescein isothiocyanate-conjugated annexin-V/propidium iodide staining and flow cytometry after treatment with 10 or 25 μM of 8 or dimethyl sulfoxide (DMSO) for 72 hours. B: Quantification of apoptotic cells from three different independent experiments. The error bars represent the standard deviation. Statistical analysis was carried out via unpaired parametric t-test Significantly different from the dimethyl sulfoxide (DMSO) vehicle control at: *p<0.05 and **p<0.01.

Based on the encouraging in vitro studies, compound 8 was further evaluated in vivo for its general tolerability and anticancer effect in mice. For the general tolerability study, healthy ICR mice (n=6) were injected with 8 at an initial dose of 10 mg/kg, intraperitoneally. Dose escalations to 20, 30 and 40 mg/kg were made on days 4, 7, and 10, respectively. The results of this in vivo study showed that compound 8 was generally well tolerated up to 40 mg/kg as shown by normal body weight changes (Figure 6) and grooming patterns.

Figure 6.
Figure 6.

In vivo dose escalation study to determine general tolerability of compound 8 for 12 days. Dosing started at 10 mg/kg/day (A), increased to 20 mg/kg/day (B), 30 mg/kg/day (C), and 40 mg/kg/day (D). An unpaired parametric t-test was used to compare body mass between the treatment group and the vehicle control-treated group. No statistical differences between groups were found.

The lead candidate 8 was further evaluated for its anticancer activity in an MDA-MB-231 tumor xenograft model in BALB/c nude mice (Figure 7). From this study, there was ~29% suppression in tumor volume in mice treated with 8 (5 mg/kg) compared to the control group (Figure 7). It was found that telmisartan provided ~15% suppression of tumor volume. At the end of the study, all the tumors were resected, the tumor masses were weighed, and weights were compared to the vehicle-treated group to validate the tumor growth reduction in vivo (Figure 7). It was found that there was a ~13% reduction in tumor mass of mice treated with telmisartan and ~23% reduction in tumor mass of mice treated with 8 in comparison to controls.

Figure 7.
Figure 7.

Tumor reduction study in BALB/c nude mice with MDA-MB-231 xenografts. Compounds 1 and 8 were administered at 5 mg/kg/day (i.p.) each. A: An unpaired parametric t-test was used to compare the mean tumor volume between mice treated with 1 (p=0.8) or 8 (p=0.3). B: An unpaired parametric t-test was used to compare tumor masses between the vehicle-treated group and groups treated with 1 (p=0.7) or 8 (p=0.5). Data represent the mean±standard error of the mean.

Discussion

TNBC is a particularly aggressive form of breast cancer that is difficult to treat, with few available treatment options. Hence, we chose two tumorigenic and highly metastatic TNBC cell lines (4T1 and MDA-MB-231) to evaluate the in vitro cell proliferation inhibition of the synthesized candidates 2-12. In this regard, we employed a standard MTT cell-proliferation assay. As we envisioned, the piperazine derivatives 2-6 showed potent inhibition of cell proliferation compared to telmisartan (Table I). One of the potential reasons for this enhanced potency might be due to a better cellular uptake compared to telmisartan that has a carboxylic acid which ionizes at physiological pH. The tert-butyloxycarbonyl-protected piperazine derivative 5 showed higher potency compared to its free piperazine derivatives 2-4. We attribute this to a higher lipophilicity of 5 allowing it to cross the lipid bilayer of the cell membrane more efficiently. Encouraged by these results, we then replaced the piperazines with more lipophilic piperidines and pyrolidine 7-9 to maintain a good balance between hydrophilicity and lipophilicity. The candidates 8 and 9 showed more potent overall inhibition of cell proliferation than the piperazine derivatives 2-6. The same trend was observed with the aminoethyl derivatives 10 and 11. Candidate 12, containing the diethanol amide, was found to be less potent that compounds 2-11. We attribute this loss in potency to the poor solubility of this derivative. Based on its potent cell proliferation inhibition, compound 8 was chosen as the lead candidate for further in vitro and in vivo studies.

This candidate showed an ~130% increase in dissociation binding constant and ~160% increase in EC50 for AT1 receptor. One of our aims was to develop a candidate with reduced affinity for AT1 receptor compared to telmisartan. Encouraged by the reduced AT1 affinity of candidate 8, it was further evaluated for its ability to reduce colony formation, its effect on cell cycle, and mechanism of cell death.

Further investigations into the anticancer mechanisms of compound 8 revealed that it halted cell-cycle progression in the G1 phase along with inhibition of colony formation and induction of apoptotic cell death in vitro. The colony-formation assay provides insights into the effectiveness of cytotoxic effects (34) of compound 8 at inhibiting the formation of colonies from single cells in the MDA-MB-231 cell line. This assay is also crucial for assessing the long-term impact of the compound on cell proliferation (35). The dose-dependent reduction in the ability to form colonies indicates the concentration-dependent inhibitory effect of compound 8 (Figure 3). This information is essential for determining the compound’s potency in preventing sustained cell growth. Generally, adherent cell populations are widely evaluated by colony-forming assay (36).

Cell-cycle analysis offers valuable information on how compound 8 influences the progression of MDA-MB-231 cells through different phases of the cell cycle. The observed significant increase in the G1 phase after treatment with 8 suggests a potential mechanism by which the compound exerts its antiproliferative effects (Figure 4). G1-Phase arrest acts as a natural defense mechanism against uncontrolled proliferation (37, 38). Compounds that induce G1 arrest have the potential to suppress tumor growth by restricting the ability of cancer cells to divide. The G1-phase arrest is often associated with a halt in cell-cycle progression, preventing cells from entering the DNA synthesis phase; G1 arrest also hints at the activation of apoptotic pathways (39, 40). Cells arrested in G1 may undergo apoptosis, a programmed cell death mechanism. This is a desirable outcome in anticancer therapies, as it leads to the elimination of damaged or aberrant cells. When we further evaluated the effect of compound 8 using an apoptosis assay, we found a significant increase in annexin-V+ cells at different concentrations of compound 8, indicating that it has apoptotic effects in MDA-MB-231 cells (Figure 5). The observed increase in apoptotic cells suggests that apoptosis is a crucial mechanism by which compound 8 exerts its cytotoxic effect. The results from these assays guide the understanding of how candidate compound 8 may impact critical cellular processes. It goes beyond simple cell-proliferation assays to delve into the potential mechanisms that contribute to the observed anticancer properties.

We then evaluated candidate compound 8 for its preliminary tolerability and maximum tolerated dose (MTD) in healthy ICR mice. For every drug candidate, it is important to determine the MTD value and typically a dose less than the MTD value is used for in vivo efficacy studies. As indicated in Figure 6, candidate 8 was tolerated up to 40 mg/kg without any apparent side-effects. Based on this high dose tolerance, we set a dose of 5 mg/kg of candidate 8, which is several fold lower than the MTD for the in vivo efficacy model. We chose a human cell-based xenograft model using MDA-MB-231 in BALB/c mice, which is widely employed for evaluating the efficacy of new drug candidates for TNBC treatment. In this study we found that candidate compound 8 led to a 29% decrease in tumor volume and a ~23% reduction in tumor mass (Figure 7). The modest inhibition of tumor growth can be attributed to various factors including poor pharmacokinetic/pharmacodynamic properties along with micromolar concentrations required for cell proliferation inhibition. In contrast, the parent compound telmisartan was found to reduce tumor volume and mass by only ~15% and ~13%, respectively (Figure 7).

Contrary to a few literature reports, which showed telmisartan to significantly reduce tumor volume by up to 70% in various tumor models (5-17), our studies indicated only a poor tumor growth reduction in an MDA-MB-231 xenograft model. It is quite possible that some of the previously reported anticancer mechanisms may not be applicable in this tumor model. Based on the increased cytotoxicity, reduced AT1 antagonism, general tolerability at high doses, and good efficacy at lower doses, we believe that there is a good potential to further carryout alkylamine-based structure–activity studies to identify a candidate compound with good pharmacological and pharmaceutical properties.

Conclusion

In conclusion, we synthesized and evaluated novel alkylamine derivatives of telmisartan as potential anticancer agents. A few of the synthesized candidates showed effective suppression of cell growth, with low micromolar EC50 values. In vitro evaluation of apoptosis and cell-cycle analysis with the lead candidate 8 revealed that apoptosis might be a key mechanism by which this candidate compound induced cell death. Further, in vivo evaluation indicated that 8 was generally well tolerated in healthy mice. Additionally, in the MDA-MB-231 mouse xenograft model, 8 demonstrated a greater reduction in tumor growth compared to telmisartan. Overall, we believe that further structure–activity relationship studies of the synthesized telmisartan alkylamine derivatives have good potential to identify a candidate drug with low in vitro potency and higher in vivo efficacy.

Acknowledgements

The Authors thank the Department of Chemistry and Biochemistry, University of Minnesota Duluth, College of Pharmacy and Integrated Biosciences, University of Minnesota, Randy Shaver Cancer Research and Community Fund, Whiteside Clinical Research Institute for their financial support.

Footnotes

  • Authors’ Contributions

    TS contributed to performing experiments, statistical analysis, and article development. ZG, and MM contributed to performing experiments. TO contributed to performing experiments and statistical analysis. KP, JR, and VM contributed to study and experimental design, interpretation of the data, and article development. All Authors have reviewed and agreed to the final version of the article.

  • Conflicts of Interest

    The Authors report no conflicts of interest in relation to this study.

  • Funding

    This study was funded by a Randy Shaver Cancer Research and Community Fund Whiteside Clinical Research Institute Grant

  • Received December 21, 2023.
  • Revision received January 25, 2024.
  • Accepted February 7, 2024.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).

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Synthesis and Biological Evaluation of Telmisartan Alkylamine Derivatives as Potential Anticancer Agents
TANNER J. SCHUMACHER, ZACHARY S. GARDNER, MICHAEL P. MCPARLAN, TASMIN OMY, KOMARAIAH PALLE, JON RUMBLEY, VENKATRAM R. MEREDDY
Anticancer Research Mar 2024, 44 (3) 911-919; DOI: 10.21873/anticanres.16885
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