Chemotherapeutic options for schistosomiasis, a prevalent infectious disease of poverty, are limited to just one drug, praziquantel (PZQ), and alternatives are needed. Our previous studies identified thiophen-2-yl pyrimidines (TPPs), which are structurally derived from microtubule (MT)-active phenylpyrimidines, as potent paralytics of Schistosoma mansoni. Although relatively non-toxic to mammalian cells, the progenitor compound, 3, had poor aqueous solubility and was lipophilic potentially hindering preclinical advancement. To address these issues and expand on the structure-activity and structure-property relationships, 43 new TPP analogs were designed and synthesized, their lipophilicity calculated (cLogP), and their anti-schistosomal activity evaluated in culture. This effort yielded compound 38, which possessed an oxetane-containing amine moiety at C5, and an ortho, ortho-difluoroaniline at C6 of the TPP scaffold. Compared to 3, compound 38 had better aqueous solubility (46 vs. < 0.5 μM), decreased lipophilicity (cLogP 4.48 vs. 6.81), a 14.5-fold increase in paralytic potency against adult S. mansoni (EC50 = 37 vs. 538 nM), and limited toxicity (CC50 > 20 μM) to three mammalian cell lines. In mice, 38 demonstrated a 3-fold longer plasma half-life (t1/2; 1.51 vs. 0.48 h) for a 40% loss in maximum plasma concentration (Cmax). In washout experiments, 38 produced a sustained paralysis of both juvenile and adult S. mansoni, possibly suggesting a broader in vivo efficacy spectrum compared to PZQ, which is inactive against the juvenile parasite. The two other medically important species, Schistosoma haematobium and Schistosoma japonicum, were also susceptible to 38. Finally, to identify potential protein targets, we synthesized a TPP photoaffinity labeling (PAL) probe that labeled several S. mansoni proteins by SDS-PAGE fluorescence analysis, although, notably, not tubulin, suggesting that the antischistosomal activity of 38 is a function of engaging other targets. Future work with the TPP series will aim to decrease toxicity further and improve pharmacokinetic properties to better support in vivo efficacy testing.

Center for Discovery and Innovation in Parasitic Diseases Skaggs School of Pharmacy and Pharmaceutical Sciences University of California San Diego 9255 Pharmacy Lane MC0657 La Jolla CA 92093 USA

Department of Chemistry and Biochemistry University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA

Department of Organic Chemistry University of Chemistry and Technology Technická 5 Prague 6 16628 Czech Republic

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McManus DP, Dunne DW, Sacko M, Utzinger J, Vennervald BJ, Zhou XN. Schistosomiasis. Nat Rev Dis Primers. 2018;4(1): 13. PubMed

Colley DG, Bustinduy AL, Secor WE, King CH. Human schistosomiasis. Lancet. 2014;383(9936): 2253–2264. PubMed PMC

Schistosomiasis; 2023. https://www.who.int/news-room/fact-sheets/detail/schistosomiasis.

Buonfrate D, Ferrari TCA, Adegnika AA, Russell Stothard J, Gobbi FG. Human schistosomiasis. Lancet. 2025;405(10479): 658–670. PubMed

Wasson PS, Kavanagh Williamson M, Hallas-Potts A, Lopez-Jimena B, Koscielniak M, Tait S, Gyapong M, Lamberti O, Ndubani R, Preston A, Musaya J, Kayuni SA, Kumwenda D, van Lieshout L, Webster BL, Downs JA, Sturt A, Specht S, Lemin ME, Long EF, Kjetland EF, Randrianasolo BS, Stothard JR, Gouvras A, Rollinson D, Secor WE, Shanaube K, Bustinduy AL. ‘Female Genital Schistosomiasis: Translational Challenges and Opportunities’ - outputs and actions from a consultative, collaborative and translational workshop. Parasitology. 2025: 1–11.

Rinaldo D, Perez-Saez J, Vounatsou P, Utzinger J, Arcand JL. The economic impact of schistosomiasis. Infect Dis Poverty. 2021;10(1): 134. PubMed PMC

Doruska MJ, Barrett CB, Rohr JR. Modeling how and why aquatic vegetation removal can free rural households from poverty-disease traps. Proc Natl Acad Sci U S A. 2024;121(52): e2411838121. PubMed PMC

Andrews P, Thomas H, Pohlke R, Seubert J. Praziquantel. Med Res Rev. 1983;3(2): 147–200. PubMed

Waechtler A, Cezanne B, Maillard D, Sun R, Wang S, Wang J, Harder A. Praziquantel - 50 Years of Research. ChemMedChem. 2023;18(12): e202300154. PubMed

Caffrey CR. Schistosomiasis and its treatment. Future Med Chem. 2015;7(6): 675–676. PubMed

Caffrey CR, El-Sakkary N, Mäder P, Krieg R, Becker K, Schlitzer M, Drewry DH, Vennerstrom JL, Grevelding CG. Drug Discovery and Development for Schistosomiasis. Neglected Tropical Diseases: Drug Discovery and Development. 2019;77: 187–225.

Caldwell N, Afshar R, Baragaña B, Bustinduy AL, Caffrey CR, Collins JJ, Fusco D, Garba A, Gardner M, Gomes M, Hoffmann KF, Hsieh M, Lo NC, McNamara CW, Komguep Nono J, Padalino G, Read KD, Roestenberg M, Spangenberg T, Specht S, Gilbert IH. Perspective on Schistosomiasis Drug Discovery: Highlights from a Schistosomiasis Drug Discovery Workshop at Wellcome Collection, London, September 2022. ACS Infect Dis. 2023;9(5): 1046–1055. PubMed PMC

Monti L, Cornec AS, Oukoloff K, Kovalevich J, Prijs K, Alle T, Brunden KR, Smith AB 3rd, El-Sakkary N, Liu LJ, Syed A, Skinner DE, Ballatore C, Caffrey CR. Congeners Derived from Microtubule-Active Phenylpyrimidines Produce a Potent and Long-Lasting Paralysis of Schistosoma mansoni In Vitro. ACS Infect Dis. 2021;7(5): 1089–1103. PubMed PMC

Monti L, Wang SC, Oukoloff K, Smith AB 3rd, Brunden KR, Caffrey CR, Ballatore C. Brain-Penetrant Triazolopyrimidine and Phenylpyrimidine Microtubule Stabilizers as Potential Leads to Treat Human African Trypanosomiasis. ChemMedChem. 2018;13(17): 1751–1754. PubMed PMC

Oukoloff K, Nzou G, Varricchio C, Lucero B, Alle T, Kovalevich J, Monti L, Cornec AS, Yao Y, James MJ, Trojanowski JQ, Lee VM- Y, Smith AB III, Brancale A, Brunden KR, Ballatore C. Evaluation of the Structure-Activity Relationship of Microtubule-Targeting 1,2,4-Triazolo[1,5-a]pyrimidines Identifies New Candidates for Neurodegenerative Tauopathies. J Med Chem. 2021;64(2): 1073–1102. PubMed PMC

Kovalevich J, Cornec AS, Yao Y, James M, Crowe A, Lee VM- Y, Trojanowski JQ, Smith AB 3rd, Ballatore C, Brunden KR. Characterization of Brain-Penetrant Pyrimidine-Containing Molecules with Differential Microtubule-Stabilizing Activities Developed as Potential Therapeutic Agents for Alzheimer’s Disease and Related Tauopathies. J Pharmacol Exp Ther. 2016;357(2): 432–450. PubMed PMC

Waring MJ. Lipophilicity in drug discovery. Expert Opin Drug Discov. 2010;5(3): 235–248. PubMed

Lipinski CA. Drug-like properties and the causes of poor solubility and poor permeability. J Pharmacol Toxicol Methods. 2000;44(1): 235–249. PubMed

Leeson PD, Springthorpe B. The influence of drug-like concepts on decision-making in medicinal chemistry. Nat Rev Drug Discov. 2007;6(11): 881–890. PubMed

Lipinski CA. Lead- and drug-like compounds: the rule-of-five revolution. Drug Discov Today Technol. 2004;1(4): 337–341. PubMed

Meanwell NA. Improving drug candidates by design: a focus on physicochemical properties as a means of improving compound disposition and safety. Chem Res Toxicol. 2011;24(9): 1420–1456. PubMed

Hughes JD, Blagg J, Price DA, Bailey S, Decrescenzo GA, Devraj RV, Ellsworth E, Fobian YM, Gibbs ME, Gilles RW, Greene N, Huang E, Krieger-Burke T, Loesel J, Wager T, Whiteley L, Zhang Y. Physiochemical drug properties associated with in vivo toxicological outcomes. Bioorg Med Chem Lett. 2008;18(17): 4872–4875. PubMed

Lou K, Yao Y, Hoye AT, James MJ, Cornec A-S, Hyde E, Gay B, Lee VM- Y, Trojanowski JQ, Smith AB III, Brunden KR, Ballatore C. Brain-penetrant, orally bioavailable microtubule-stabilizing small molecules are potential candidate therapeutics for Alzheimer’s disease and related tauopathies. J Med Chem. 2014;57(14): 6116–6127. PubMed PMC

Alle T, Varricchio C, Yao Y, Lucero B, Nzou G, Demuro S, Muench M, Vuong KD, Oukoloff K, Cornec A-S, Francisco KR, Caffrey CR, Lee VM- Y, Smith AB III, Brancale A, Brunden KR, Ballatore C. Microtubule-Stabilizing 1,2,4-Triazolo[1,5-a]pyrimidines as Candidate Therapeutics for Neurodegenerative Disease: Matched Molecular Pair Analyses and Computational Studies Reveal New Structure–Activity Insights. J Med Chem. 2023;66(1): 435–459. PubMed PMC

Kolb H, Finn M, Sharpless K. Click chemistry: Diverse chemical function from a few good reactions. Angewandte Chemie-International Edition. 2001;40(11): 2004-+. PubMed

Mackinnon AL, Taunton J. Target Identification by Diazirine Photo-Cross-linking and Click Chemistry. Curr Protoc Chem Biol. 2009;1: 55–73. PubMed PMC

Oukoloff K, Kovalevich J, Cornec AS, Yao Y, Owyang ZA, James M, Trojanowski JQ, Lee VM- Y, Smith AB III, Brunden KR, Ballatore C. Design, synthesis and evaluation of photoactivatable derivatives of microtubule (MT)-active [1,2,4]triazolo[1,5-a]pyrimidines. Bioorg Med Chem Lett. 2018;28(12): 2180–2183. PubMed PMC

Sonogashira K. Development of Pd-Cu catalyzed cross-coupling of terminal acetylenes with sp(2)-carbon halides. J Organomet Chem. 2002;653(1–2): 46–49.

Abdulla M-H, Ruelas DS, Wolff B, Snedecor J, Lim K-C, Xu F, Renslo AR, Williams J, McKerrow JH, Caffrey CR. Drug discovery for schistosomiasis: hit and lead compounds identified in a library of known drugs by medium-throughput phenotypic screening. PLoS Negl Trop Dis. 2009;3(7): e478. PubMed PMC

Long T, Rojo-Arreola L, Shi D, El-Sakkary N, Jarnagin K, Rock F, Meewan M, Rascón AA Jr, Lin L, Cunningham KA, Lemieux GA, Podust L, Abagyan R, Ashrafi K, McKerrow JH, Caffrey CR. Phenotypic, chemical and functional characterization of cyclic nucleotide phosphodiesterase 4 (PDE4) as a potential anthelmintic drug target. PLoS Negl Trop Dis. 2017;11(7): e0005680. PubMed PMC

Marcellino C, Gut J, Lim KC, Singh R, McKerrow J, Sakanari J. WormAssay: a novel computer application for whole-plate motion-based screening of macroscopic parasites. PLoS Negl Trop Dis. 2012;6(1): e1494. PubMed PMC

B Bibo-Verdugo B, Wang SC, Almaliti J, Ta AP, Jiang Z, Wong DA, Lietz CB, Suzuki BM, El-Sakkary N, Hook V, Salvesen GS, Gerwick WH, Caffrey CR, O’Donoghue AJ. The Proteasome as a Drug Target in the Metazoan Pathogen, Schistosoma mansoni. ACS Infect Dis. 2019;5(10): 1802–1812. PubMed PMC

O’Brien J, Wilson I, Orton T, Pognan F. Investigation of the Alamar Blue (resazurin) fluorescent dye for the assessment of mammalian cell cytotoxicity. Eur J Biochem. 2000;267(17): 5421–5426. PubMed

Francisco KR, Monti L, Yang W, Park H, Liu LJ, Watkins K, Amarasinghe DK, Nalli M, Polaquini CR, Regasini LO, Crotti AEM, Silvestri R, Magalhães LG, Caffrey CR. Structure-activity relationship of dibenzylideneacetone analogs against the neglected disease pathogen, Trypanosoma brucei. Bioorg Med Chem Lett. 2023;81: 129123. PubMed PMC

http://www.chemaxon.com

Nagilla R, Nord M, McAtee JJ, Jolivette LJ. Cassette dosing for pharmacokinetic screening in drug discovery: comparison of clearance, volume of distribution, half-life, mean residence time, and oral bioavailability obtained by cassette and discrete dosing in rats. J Pharm Sci. 2011;100(9): 3862–3874. PubMed

Sabah AA, Fletcher C, Webbe G, Doenhoff MJ. Schistosoma mansoni: chemotherapy of infections of different ages. Exp Parasitol. 1986;61(3): 294–303. PubMed

Caffrey CR. Chemotherapy of schistosomiasis: present and future. Curr Opin Chem Biol. 2007;11(4): 433–439. PubMed

Hailegebriel T, Nibret E, Munshea A. Efficacy of Praziquantel for the Treatment of Human Schistosomiasis in Ethiopia: A Systematic Review and Meta-Analysis. J Trop Med. 2021;2021: 2625255. PubMed PMC

Sisay M, Hailu T, Damtie D, Geta K, Zelalem L, Misganaw D. Efficacy of single dose praziquantel against Schistosoma mansoni in East Africa: a systematic review and meta-analysis. Sci Rep. 2025;15(1): 4642. PubMed PMC

Chan JD, Cupit PM, Gunaratne GS, McCorvy JD, Yang Y, Stoltz K, Webb TR, Dosa PI, Roth BL, Abagyan R, Cunningham C, Marchant JS. The anthelmintic praziquantel is a human serotoninergic G-protein-coupled receptor ligand. Nat Commun. 2017;8(1): 1910. PubMed PMC

Pica-Mattoccia L, Cioli D. Sex- and stage-related sensitivity of Schistosoma mansoni to in vivo and in vitro praziquantel treatment. Int J Parasitol. 2004;34(4): 527–533. PubMed

Lucero B, Francisco KR, Varricchio C, Liu LJ, Yao Y, Brancale A, Brunden KR, Caffrey CR, Ballatore C. Design, Synthesis, and Evaluation of An Anti-trypanosomal [1,2,4]Triazolo[1,5-a]pyrimidine Probe for Photoaffinity Labeling Studies. ChemMedChem. 2024;19(8): e202300656. PubMed PMC

Lucero B, Alle T, Bufano M, Yao Y, Brunden KR, Brancale A, Ballatore C, Francisco KR, Caffrey CR. Photoaffinity labeling of protein targets in a complex metazoan: proof-of-concept using a probe for Schistosoma mansoni tubulin. bioRxiv. 2025. 10.1101/2025.10.04.680471 DOI

Zhang J, Xin L, Shan B, Chen W, Xie M, Yuen D, Zhang W, Zhang Z, Lajoie GA, Ma B. PEAKS DB: de novo sequencing assisted database search for sensitive and accurate peptide identification. Mol Cell Proteomics. 2012;11(4): M111.010587.

Brindley PJ, Strand M, Norden AP, Sher A. Role of host antibody in the chemotherapeutic action of praziquantel against Schistosoma mansoni: identification of target antigens. Mol Biochem Parasitol. 1989;34(2): 99–108. PubMed

Brindley PJ, Sher A. The chemotherapeutic effect of praziquantel against Schistosoma mansoni is dependent on host antibody response. J Immunol. 1987;139(1): 215–220. PubMed

Driciru E, Koopman JPR, Cose S, Siddiqui AA, Yazdanbakhsh M, Elliott AM, Roestenberg M. Immunological Considerations for Schistosoma Vaccine Development: Transition to Endemic Settings. Front Immunol. 2021;12: 635985. PubMed PMC

Andrews P. Praziquantel: mechanisms of anti-schistosomal activity. Pharmacol Ther. 1985;29(1): 129–156. PubMed

Matsumoto Y, Perry G, Levine RJ, Blanton R, Mahmoud AA, Aikawa M. Paramyosin and actin in schistosomal teguments. Nature. 1988;333(6168): 76–78. PubMed

Schmidt J, Bodor O, Gohr L, Kunz W. Paramyosin isoforms of Schistosoma mansoni are phosphorylated and localized in a large variety of muscle types. Parasitology. 1996;112 ( Pt 5): 459–467. PubMed

Grossman Z, Ram D, Markovics A, Tarrab-Hazdai R, Lantner F, Ziv E, Schechter I. Schistosoma mansoni: stage-specific expression of muscle-specific genes. Exp Parasitol. 1990;70(1): 62–71. PubMed

Cunha VM, Meyer-Fernandes JR, Noël F. A (Ca(2+)-Mg2+)ATPase from Schistosoma mansoni is coupled to an active transport of calcium. Mol Biochem Parasitol. 1992;52(2): 167–173. PubMed

Abdulla MH, Lim KC, Sajid M, McKerrow JH, Caffrey CR. Schistosomiasis mansoni: novel chemotherapy using a cysteine protease inhibitor. PLoS Med. 2007;4(1): e14. PubMed PMC

Basch PF. Cultivation of Schistosoma mansoni in vitro. I. Establishment of cultures from cercariae and development until pairing. J Parasitol. 1981;67(2): 179–185. PubMed